X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/8a7f259d86f19ec320d180180dee4911ed80946e..b87a6e0eedc31fdaa0d468349769b265db904aa7:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index adf652d9a..75a5ac02c 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1,10 +1,12 @@ -. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.20 2007/07/19 17:07:39 magnus Exp $ -. . ///////////////////////////////////////////////////////////////////////////// . This is the primary source of the Exim Manual. It is an xfpt document that is . converted into DocBook XML for subsequent conversion into printing and online . formats. The markup used herein is "standard" xfpt markup, with some extras. . The markup is summarized in a file called Markup.txt. +. +. WARNING: When you use the .new macro, make sure it appears *before* any +. adjacent index items; otherwise you get an empty "paragraph" which causes +. unwanted vertical space. . ///////////////////////////////////////////////////////////////////////////// .include stdflags @@ -28,7 +30,7 @@ foot_right_recto="&chaptertitle; (&chapternumber;)" foot_right_verso="&chaptertitle; (&chapternumber;)" toc_chapter_blanks="yes,yes" - table_warn_soft_overflow="no" + table_warn_overflow="overprint" ?> .literal off @@ -43,8 +45,8 @@ . the element must also be updated for each new edition. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.66" -.set version "4.67" +.set previousversion "4.75" +.set version "4.80" .set ACL "access control lists (ACLs)" .set I "    " @@ -168,17 +170,15 @@ Specification of the Exim Mail Transfer Agent The Exim MTA -10 April 2007 -PhilipHazel -PH -University of Cambridge Computing Service -
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
+17 May 2012 +EximMaintainers +EM - 4.67 - 10 April 2007 - PH + 4.80 + 17 May 2012 + EM -2007University of Cambridge +2012University of Cambridge .literal off @@ -253,7 +253,7 @@ maximum - limit + limit monitor @@ -363,6 +363,8 @@ contributors. .section "Exim documentation" "SECID1" +. Keep this example change bar when updating the documentation! + .new .cindex "documentation" This edition of the Exim specification applies to version &version; of Exim. @@ -383,7 +385,7 @@ very wide interest. .cindex "books about Exim" An &"easier"& discussion of Exim which provides more in-depth explanatory, introductory, and tutorial material can be found in a book entitled &'The Exim -SMTP Mail Server'&, published by UIT Cambridge +SMTP Mail Server'& (second edition, 2007), published by UIT Cambridge (&url(http://www.uit.co.uk/exim-book/)). This book also contains a chapter that gives a general introduction to SMTP and @@ -426,8 +428,6 @@ directory are: .row &_exim.8_& "a man page of Exim's command line options" .row &_experimental.txt_& "documentation of experimental features" .row &_filter.txt_& "specification of the filter language" -.row &_pcrepattern.txt_& "specification of PCRE regular expressions" -.row &_pcretest.txt_& "specification of the PCRE testing program" .row &_Exim3.upgrade_& "upgrade notes from release 2 to release 3" .row &_Exim4.upgrade_& "upgrade notes from release 3 to release 4" .endtable @@ -450,33 +450,29 @@ Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge. .cindex "wiki" .cindex "FAQ" -.new As well as Exim distribution tar files, the Exim web site contains a number of differently formatted versions of the documentation. A recent addition to the -online information is the Exim wiki (&url(http://www.exim.org/eximwiki/)), +online information is the Exim wiki (&url(http://wiki.exim.org)), which contains what used to be a separate FAQ, as well as various other examples, tips, and know-how that have been contributed by Exim users. .cindex Bugzilla -An Exim Bugzilla exists at &url(http://www.exim.org/bugzilla/). You can use +An Exim Bugzilla exists at &url(http://bugs.exim.org). You can use this to report bugs, and also to add items to the wish list. Please search first to check that you are not duplicating a previous entry. -.wen .section "Mailing lists" "SECID3" .cindex "mailing lists" "for Exim users" -.new The following Exim mailing lists exist: .table2 140pt +.row &'exim-announce@exim.org'& "Moderated, low volume announcements list" .row &'exim-users@exim.org'& "General discussion list" .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc." -.row &'exim-announce@exim.org'& "Moderated, low volume announcements list" -.row &'exim-future@exim.org'& "Discussion of long-term development" +.row &'exim-cvs@exim.org'& "Automated commit messages from the VCS" .endtable -.wen You can subscribe to these lists, change your existing subscriptions, and view or search the archives via the mailing lists link on the Exim home page. @@ -492,18 +488,18 @@ lists. .section "Exim training" "SECID4" .cindex "training courses" -From time to time (approximately annually at the time of writing), training -courses are run by the author of Exim in Cambridge, UK. Details of any -forthcoming courses can be found on the web site -&url(http://www-tus.csx.cam.ac.uk/courses/exim/). - +Training courses in Cambridge (UK) used to be run annually by the author of +Exim, before he retired. At the time of writing, there are no plans to run +further Exim courses in Cambridge. However, if that changes, relevant +information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/). .section "Bug reports" "SECID5" .cindex "bug reports" .cindex "reporting bugs" -Reports of obvious bugs should be emailed to &'bugs@exim.org'&. However, if you -are unsure whether some behaviour is a bug or not, the best thing to do is to -post a message to the &'exim-dev'& mailing list and have it discussed. +Reports of obvious bugs can be emailed to &'bugs@exim.org'& or reported +via the Bugzilla (&url(http://bugs.exim.org)). However, if you are unsure +whether some behaviour is a bug or not, the best thing to do is to post a +message to the &'exim-dev'& mailing list and have it discussed. @@ -537,13 +533,13 @@ The &_.bz2_& file is usually a lot smaller than the &_.gz_& file. .cindex "distribution" "signing details" .cindex "distribution" "public key" .cindex "public key for signed distribution" -The distributions are currently signed with Philip Hazel's GPG key. The +The distributions are currently signed with Nigel Metheringham's GPG key. The corresponding public key is available from a number of keyservers, and there is -also a copy in the file &_Public-Key_&. The signatures for the tar bundles are +also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are in: .display -&_exim-n.nn.tar.gz.sig_& -&_exim-n.nn.tar.bz2.sig_& +&_exim-n.nn.tar.gz.asc_& +&_exim-n.nn.tar.bz2.asc_& .endd For each released version, the log of changes is made separately available in a separate file in the directory &_ChangeLogs_& so that it is possible to @@ -729,12 +725,11 @@ the Exim documentation, &"spool"& is always used in the first sense. A number of pieces of external code are included in the Exim distribution. .ilist -Regular expressions are supported in the main Exim program and in the Exim -monitor using the freely-distributable PCRE library, copyright © -University of Cambridge. The source is distributed in the directory -&_src/pcre_&. However, this is a cut-down version of PCRE. If you want to use -the PCRE library in other programs, you should obtain and install the full -version of the library from +Regular expressions are supported in the main Exim program and in the +Exim monitor using the freely-distributable PCRE library, copyright +© University of Cambridge. The source to PCRE is no longer shipped with +Exim, so you will need to use the version of PCRE shipped with your system, +or obtain and install the full version of the library from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre). .next .cindex "cdb" "acknowledgment" @@ -751,7 +746,6 @@ This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later version. - This code implements Dan Bernstein's Constant DataBase (cdb) spec. Information, the spec and sample code for cdb can be obtained from &url(http://www.pobox.com/~djb/cdb.html). This implementation borrows @@ -1549,7 +1543,6 @@ If a host is unreachable for a period of time, a number of messages may be waiting for it by the time it recovers, and sending them in a single SMTP connection is clearly beneficial. Whenever a delivery to a remote host is deferred, - .cindex "hints database" Exim makes a note in its hints database, and whenever a successful SMTP delivery has happened, it looks to see if any other messages are waiting @@ -1559,7 +1552,6 @@ one connection. - .section "Permanent delivery failure" "SECID21" .cindex "delivery" "permanent failure" .cindex "bounce message" "when generated" @@ -1655,6 +1647,23 @@ architecture and operating system for itself, but the defaults can be overridden if necessary. +.new +.section "PCRE library" "SECTpcre" +.cindex "PCRE library" +Exim no longer has an embedded PCRE library as the vast majority of +modern systems include PCRE as a system library, although you may need +to install the PCRE or PCRE development package for your operating +system. If your system has a normal PCRE installation the Exim build +process will need no further configuration. If the library or the +headers are in an unusual location you will need to either set the PCRE_LIBS +and INCLUDE directives appropriately, +or set PCRE_CONFIG=yes to use the installed &(pcre-config)& command. +If your operating system has no +PCRE support then you will need to obtain and build the current PCRE +from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre/). +More information on PCRE is available at &url(http://www.pcre.org/). +.wen + .section "DBM libraries" "SECTdb" .cindex "DBM libraries" "discussion of" .cindex "hints database" "DBM files used for" @@ -1864,6 +1873,14 @@ SUPPORT_TLS=yes TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto TLS_INCLUDE=-I/usr/local/openssl/include/ .endd +.new +.cindex "pkg-config" "OpenSSL" +If you have &'pkg-config'& available, then instead you can just use: +.code +SUPPORT_TLS=yes +USE_OPENSSL_PC=openssl +.endd +.wen .cindex "USE_GNUTLS" If GnuTLS is installed, you should set .code @@ -1879,6 +1896,16 @@ USE_GNUTLS=yes TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt TLS_INCLUDE=-I/usr/gnu/include .endd +.new +.cindex "pkg-config" "GnuTLS" +If you have &'pkg-config'& available, then instead you can just use: +.code +SUPPORT_TLS=yes +USE_GNUTLS=yes +USE_GNUTLS_PC=gnutls +.endd +.wen + You do not need to set TLS_INCLUDE if the relevant directory is already specified in INCLUDE. Details of how to configure Exim to make use of TLS are given in chapter &<>&. @@ -1887,8 +1914,11 @@ given in chapter &<>&. .section "Use of tcpwrappers" "SECID27" + .cindex "tcpwrappers, building Exim to support" .cindex "USE_TCP_WRAPPERS" +.cindex "TCP_WRAPPERS_DAEMON_NAME" +.cindex "tcp_wrappers_daemon_name" Exim can be linked with the &'tcpwrappers'& library in order to check incoming SMTP calls using the &'tcpwrappers'& control files. This may be a convenient alternative to Exim's own checking facilities for installations that are @@ -1903,18 +1933,20 @@ USE_TCP_WRAPPERS=yes CFLAGS=-O -I/usr/local/include EXTRALIBS_EXIM=-L/usr/local/lib -lwrap .endd -in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is -&"exim"&. For example, the line +in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control +files is &"exim"&. For example, the line .code exim : LOCAL 192.168.1. .friendly.domain.example .endd in your &_/etc/hosts.allow_& file allows connections from the local host, from the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&. -All other connections are denied. Consult the &'tcpwrappers'& documentation for +All other connections are denied. The daemon name used by &'tcpwrappers'& +can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in +in &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the +configure file. Consult the &'tcpwrappers'& documentation for further details. - .section "Including support for IPv6" "SECID28" .cindex "IPv6" "including support for" Exim contains code for use on systems that have IPv6 support. Setting @@ -1934,6 +1966,36 @@ support has not been tested for some time. +.section "Dynamically loaded lookup module support" "SECTdynamicmodules" +.cindex "lookup modules" +.cindex "dynamic modules" +.cindex ".so building" +On some platforms, Exim supports not compiling all lookup types directly into +the main binary, instead putting some into external modules which can be loaded +on demand. +This permits packagers to build Exim with support for lookups with extensive +library dependencies without requiring all users to install all of those +dependencies. +Most, but not all, lookup types can be built this way. + +Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be +installed; Exim will only load modules from that directory, as a security +measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined +for your OS; see &_OS/Makefile-Linux_& for an example. +Some other requirements for adjusting &`EXTRALIBS`& may also be necessary, +see &_src/EDITME_& for details. + +Then, for each module to be loaded dynamically, define the relevant +&`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes". +For example, this will build in lsearch but load sqlite and mysql support +on demand: +.code +LOOKUP_LSEARCH=yes +LOOKUP_SQLITE=2 +LOOKUP_MYSQL=2 +.endd + + .section "The building process" "SECID29" .cindex "build directory" Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been @@ -2071,6 +2133,28 @@ files or libraries are required. When a lookup type is not included in the binary, attempts to configure Exim to use it cause run time configuration errors. +.new +.cindex "pkg-config" "lookups" +.cindex "pkg-config" "authenticators" +Many systems now use a tool called &'pkg-config'& to encapsulate information +about how to compile against a library; Exim has some initial support for +being able to use pkg-config for lookups and authenticators. For any given +makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new +variable with the &`_PC`& suffix in the name and assign as the value the +name of the package to be queried. The results of querying via the +&'pkg-config'& command will be added to the appropriate Makefile variables +with &`+=`& directives, so your version of &'make'& will need to support that +syntax. For instance: +.code +LOOKUP_SQLITE=yes +LOOKUP_SQLITE_PC=sqlite3 +AUTH_GSASL=yes +AUTH_GSASL_PC=libgsasl +AUTH_HEIMDAL_GSSAPI=yes +AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi +.endd +.wen + .cindex "Perl" "including support for" Exim can be linked with an embedded Perl interpreter, allowing Perl subroutines to be called during string expansion. To enable this facility, @@ -2214,9 +2298,8 @@ but this usage is deprecated. .cindex "installing Exim" "what is not installed" Running &'make install'& does not copy the Exim 4 conversion script -&'convert4r4'&, or the &'pcretest'& test program. You will probably run the -first of these only once (if you are upgrading from Exim 3), and the second -isn't really part of Exim. None of the documentation files in the &_doc_& +&'convert4r4'&. You will probably run this only once if you are +upgrading from Exim 3. None of the documentation files in the &_doc_& directory are copied, except for the info files when you have set INFO_DIRECTORY, as described in section &<>& below. @@ -2598,6 +2681,11 @@ This option causes Exim to output a few sentences stating what it is. The same output is generated if the Exim binary is called with no options and no arguments. +.vitem &%--version%& +.oindex "&%--version%&" +This option is an alias for &%-bV%& and causes version information to be +displayed. + .vitem &%-B%&<&'type'&> .oindex "&%-B%&" .cindex "8-bit characters" @@ -2827,12 +2915,10 @@ The &'exim_checkaccess'& utility is a &"packaged"& version of &%-bh%& whose output just states whether a given recipient address from a given host is acceptable or not. See section &<>&. -.new Features such as authentication and encryption, where the client input is not plain text, cannot easily be tested with &%-bh%&. Instead, you should use a specialized SMTP test program such as &url(http://jetmore.org/john/code/#swaks,swaks). -.wen .vitem &%-bhc%&&~<&'IP&~address'&> .oindex "&%-bhc%&" @@ -2905,6 +2991,26 @@ The specified sender is treated as if it were given as the argument to the preference to the address taken from the message. The caller of Exim must be a trusted user for the sender of a message to be set in this way. +.vitem &%-bmalware%&&~<&'filename'&> +.oindex "&%-bmalware%&" +.cindex "testing", "malware" +.cindex "malware scan test" +This debugging option causes Exim to scan the given file, +using the malware scanning framework. The option of &%av_scanner%& influences +this option, so if &%av_scanner%&'s value is dependent upon an expansion then +the expansion should have defaults which apply to this invocation. ACLs are +not invoked, so if &%av_scanner%& references an ACL variable then that variable +will never be populated and &%-bmalware%& will fail. + +Exim will have changed working directory before resolving the filename, so +using fully qualified pathnames is advisable. Exim will be running as the Exim +user when it tries to open the file, rather than as the invoking user. +This option requires admin privileges. + +The &%-bmalware%& option will not be extended to be more generally useful, +there are better tools for file-scanning. This option exists to help +administrators verify their Exim and AV scanner configuration. + .vitem &%-bnq%& .oindex "&%-bnq%&" .cindex "address qualification, suppressing" @@ -2929,7 +3035,7 @@ unqualified addresses in header lines are left alone. .vitem &%-bP%& .oindex "&%-bP%&" -.cindex "configuration options, extracting" +.cindex "configuration options" "extracting" .cindex "options" "configuration &-- extracting" If this option is given with no arguments, it causes the values of all Exim's main configuration options to be written to the standard output. The values @@ -2938,6 +3044,9 @@ arguments, for example: .code exim -bP qualify_domain hold_domains .endd +.cindex "hiding configuration option values" +.cindex "configuration options" "hiding value of" +.cindex "options" "hiding value of" However, any option setting that is preceded by the word &"hide"& in the configuration file is not shown in full, except to an admin user. For other users, the output is as in this example: @@ -2966,6 +3075,7 @@ local part) and outputs what it finds. .cindex "options" "router &-- extracting" .cindex "options" "transport &-- extracting" +.cindex "options" "authenticator &-- extracting" If one of the words &%router%&, &%transport%&, or &%authenticator%& is given, followed by the name of an appropriate driver instance, the option settings for that driver are output. For example: @@ -2979,6 +3089,11 @@ using one of the words &%router_list%&, &%transport_list%&, or settings can be obtained by using &%routers%&, &%transports%&, or &%authenticators%&. +.cindex "options" "macro &-- extracting" +If invoked by an admin user, then &%macro%&, &%macro_list%& and &%macros%& +are available, similarly to the drivers. Because macros are sometimes used +for storing passwords, this option is restricted. +The output format is one item per line. .vitem &%-bp%& .oindex "&%-bp%&" @@ -3161,7 +3276,7 @@ the listening daemon. .cindex "testing" "addresses" .cindex "address" "testing" This option runs Exim in address testing mode, in which each argument is taken -as a &new(recipient) address to be tested for deliverability. The results are +as a recipient address to be tested for deliverability. The results are written to the standard output. If a test fails, and the caller is not an admin user, no details of the failure are output, because these might contain sensitive information such as usernames and passwords for database lookups. @@ -3207,7 +3322,7 @@ doing such tests. .cindex "version number of Exim" This option causes Exim to write the current version number, compilation number, and compilation date of the &'exim'& binary to the standard output. -It also lists the DBM library this is being used, the optional modules (such as +It also lists the DBM library that is being used, the optional modules (such as specific lookup types), the drivers that are included in the binary, and the name of the run time configuration file that is in use. @@ -3224,7 +3339,7 @@ dynamic testing facilities. .cindex "verifying address" "using &%-bv%&" .cindex "address" "verification" This option runs Exim in address verification mode, in which each argument is -taken as a &new(recipient) address to be verified by the routers. (This does +taken as a recipient address to be verified by the routers. (This does not involve any verification callouts). During normal operation, verification happens mostly as a consequence processing a &%verify%& condition in an ACL (see chapter &<>&). If you want to test an entire ACL, possibly @@ -3276,6 +3391,23 @@ This option acts like &%-bv%&, but verifies the address as a sender rather than a recipient address. This affects any rewriting and qualification that might happen. +.vitem &%-bw%& +.oindex "&%-bw%&" +.cindex "daemon" +.cindex "inetd" +.cindex "inetd" "wait mode" +This option runs Exim as a daemon, awaiting incoming SMTP connections, +similarly to the &%-bd%& option. All port specifications on the command-line +and in the configuration file are ignored. Queue-running may not be specified. + +In this mode, Exim expects to be passed a socket as fd 0 (stdin) which is +listening for connections. This permits the system to start up and have +inetd (or equivalent) listen on the SMTP ports, starting an Exim daemon for +each port only when the first connection is received. + +If the option is given as &%-bw%&<&'time'&> then the time is a timeout, after +which the daemon will exit, which should cause inetd to listen once more. + .vitem &%-C%&&~<&'filelist'&> .oindex "&%-C%&" .cindex "configuration file" "alternate" @@ -3288,25 +3420,23 @@ name, but it can be a colon-separated list of names. In this case, the first file that exists is used. Failure to open an existing file stops Exim from proceeding any further along the list, and an error is generated. -When this option is used by a caller other than root or the Exim user, and the -list is different from the compiled-in list, Exim gives up its root privilege -immediately, and runs with the real and effective uid and gid set to those of -the caller. However, if ALT_CONFIG_ROOT_ONLY is defined in -&_Local/Makefile_&, root privilege is retained for &%-C%& only if the caller of -Exim is root. - -That is, the Exim user is no longer privileged in this regard. This build-time -option is not set by default in the Exim source distribution tarbundle. -However, if you are using a &"packaged"& version of Exim (source or binary), -the packagers might have enabled it. - -Setting ALT_CONFIG_ROOT_ONLY locks out the possibility of testing a -configuration using &%-C%& right through message reception and delivery, even -if the caller is root. The reception works, but by that time, Exim is running -as the Exim user, so when it re-executes to regain privilege for the delivery, -the use of &%-C%& causes privilege to be lost. However, root can test reception -and delivery using two separate commands (one to put a message on the queue, -using &%-odq%&, and another to do the delivery, using &%-M%&). +When this option is used by a caller other than root, and the list is different +from the compiled-in list, Exim gives up its root privilege immediately, and +runs with the real and effective uid and gid set to those of the caller. +However, if a TRUSTED_CONFIG_LIST file is defined in &_Local/Makefile_&, that +file contains a list of full pathnames, one per line, for configuration files +which are trusted. Root privilege is retained for any configuration file so +listed, as long as the caller is the Exim user (or the user specified in the +CONFIGURE_OWNER option, if any), and as long as the configuration file is +not writeable by inappropriate users or groups. + +Leaving TRUSTED_CONFIG_LIST unset precludes the possibility of testing a +configuration using &%-C%& right through message reception and delivery, +even if the caller is root. The reception works, but by that time, Exim is +running as the Exim user, so when it re-executes to regain privilege for the +delivery, the use of &%-C%& causes privilege to be lost. However, root can +test reception and delivery using two separate commands (one to put a message +on the queue, using &%-odq%&, and another to do the delivery, using &%-M%&). If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a prefix string with which any file named in a &%-C%& command line option @@ -3327,6 +3457,7 @@ caller is privileged, or unless it is an exotic configuration that does not require privilege. No check is made on the owner or group of the files specified by this option. + .vitem &%-D%&<&'macro'&>=<&'value'&> .oindex "&%-D%&" .cindex "macro" "setting on command line" @@ -3336,6 +3467,14 @@ unprivileged caller, it causes Exim to give up its root privilege. If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is completely disabled, and its use causes an immediate error exit. +If WHITELIST_D_MACROS is defined in &_Local/Makefile_& then it should be a +colon-separated list of macros which are considered safe and, if &%-D%& only +supplies macros from this list, and the values are acceptable, then Exim will +not give up root privilege if the caller is root, the Exim run-time user, or +the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected +to be removed in the future. Acceptable values for the macros satisfy the +regexp: &`^[A-Za-z0-9_/.-]*$`& + The entire option (including equals sign if present) must all be within one command line item. &%-D%& can be used to set the value of a macro to the empty string, in which case the equals sign is optional. These two commands are @@ -3352,6 +3491,7 @@ exim '-D ABC = something' ... .endd &%-D%& may be repeated up to 10 times on a command line. + .vitem &%-d%&<&'debug&~options'&> .oindex "&%-d%&" .cindex "debugging" "list of selectors" @@ -3729,6 +3869,14 @@ by an admin user. This option causes the contents of the message body (-D) spool file to be written to the standard output. This option can be used only by an admin user. +.vitem &%-Mvc%&&~<&'message&~id'&> +.oindex "&%-Mvc%&" +.cindex "message" "listing in RFC 2822 format" +.cindex "listing" "message in RFC 2822 format" +This option causes a copy of the complete message (header lines plus body) to +be written to the standard output in RFC 2822 format. This option can be used +only by an admin user. + .vitem &%-Mvh%&&~<&'message&~id'&> .oindex "&%-Mvh%&" .cindex "listing" "message headers" @@ -4450,17 +4598,21 @@ existing file in the list. .cindex "configuration file" "ownership" .cindex "ownership" "configuration file" The run time configuration file must be owned by root or by the user that is -specified at compile time by the EXIM_USER option, or by the user that is specified at compile time by the CONFIGURE_OWNER option (if set). The -configuration file must not be world-writeable or group-writeable, unless its -group is the one specified at compile time by the EXIM_GROUP option or by the +configuration file must not be world-writeable, or group-writeable unless its +group is the root group or the one specified at compile time by the CONFIGURE_GROUP option. &*Warning*&: In a conventional configuration, where the Exim binary is setuid to root, anybody who is able to edit the run time configuration file has an -easy way to run commands as root. If you make your mail administrators members -of the Exim group, but do not trust them with root, make sure that the run time -configuration is not group writeable. +easy way to run commands as root. If you specify a user or group in the +CONFIGURE_OWNER or CONFIGURE_GROUP options, then that user and/or any users +who are members of that group will trivially be able to obtain root privileges. + +Up to Exim version 4.72, the run time configuration file was also permitted to +be writeable by the Exim user and/or group. That has been changed in Exim 4.73 +since it offered a simple privilege escalation for any attacker who managed to +compromise the Exim user account. A default configuration file, which will work correctly in simple situations, is provided in the file &_src/configure.default_&. If CONFIGURE_FILE @@ -4476,21 +4628,24 @@ configuration. .cindex "configuration file" "alternate" A one-off alternate configuration can be specified by the &%-C%& command line option, which may specify a single file or a list of files. However, when -&%-C%& is used, Exim gives up its root privilege, unless called by root or the -Exim user (or unless the argument for &%-C%& is identical to the built-in value -from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of -configuration files before installing them. No owner or group checks are done -on a configuration file specified by &%-C%&. - -The privileged use of &%-C%& by the Exim user can be locked out by setting -ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However, -if you do this, you also lock out the possibility of testing a -configuration using &%-C%& right through message reception and delivery, even -if the caller is root. The reception works, but by that time, Exim is running -as the Exim user, so when it re-execs to regain privilege for the delivery, the -use of &%-C%& causes privilege to be lost. However, root can test reception and -delivery using two separate commands (one to put a message on the queue, using -&%-odq%&, and another to do the delivery, using &%-M%&). +&%-C%& is used, Exim gives up its root privilege, unless called by root (or +unless the argument for &%-C%& is identical to the built-in value from +CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller +is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%& +is useful mainly for checking the syntax of configuration files before +installing them. No owner or group checks are done on a configuration file +specified by &%-C%&, if root privilege has been dropped. + +Even the Exim user is not trusted to specify an arbitrary configuration file +with the &%-C%& option to be used with root privileges, unless that file is +listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of +testing a configuration using &%-C%& right through message reception and +delivery, even if the caller is root. The reception works, but by that time, +Exim is running as the Exim user, so when it re-execs to regain privilege for +the delivery, the use of &%-C%& causes privilege to be lost. However, root +can test reception and delivery using two separate commands (one to put a +message on the queue, using &%-odq%&, and another to do the delivery, using +&%-M%&). If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a prefix string with which any file named in a &%-C%& command line option must @@ -4505,6 +4660,16 @@ non-privileged user causes Exim to discard its root privilege. If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is completely disabled, and its use causes an immediate error exit. +The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder +to declare certain macro names trusted, such that root privilege will not +necessarily be discarded. +WHITELIST_D_MACROS defines a colon-separated list of macros which are +considered safe and, if &%-D%& only supplies macros from this list, and the +values are acceptable, then Exim will not give up root privilege if the caller +is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a +transition mechanism and is expected to be removed in the future. Acceptable +values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`& + Some sites may wish to use the same Exim binary on different machines that share a file system, but to use different configuration files on each machine. If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first @@ -4529,30 +4694,38 @@ is introduced by the word &"begin"& followed by the name of the part. The optional parts are: .ilist -&'ACL'&: Access control lists for controlling incoming SMTP mail. +&'ACL'&: Access control lists for controlling incoming SMTP mail (see chapter +&<>&). .next .cindex "AUTH" "configuration" &'authenticators'&: Configuration settings for the authenticator drivers. These are concerned with the SMTP AUTH command (see chapter &<>&). .next &'routers'&: Configuration settings for the router drivers. Routers process -addresses and determine how the message is to be delivered. +addresses and determine how the message is to be delivered (see chapters +&<>&&--&<>&). .next &'transports'&: Configuration settings for the transport drivers. Transports -define mechanisms for copying messages to destinations. +define mechanisms for copying messages to destinations (see chapters +&<>&&--&<>&). .next -&'retry'&: Retry rules, for use when a message cannot be immediately delivered. +&'retry'&: Retry rules, for use when a message cannot be delivered immediately. +If there is no retry section, or if it is empty (that is, no retry rules are +defined), Exim will not retry deliveries. In this situation, temporary errors +are treated the same as permanent errors. Retry rules are discussed in chapter +&<>&. .next &'rewrite'&: Global address rewriting rules, for use when a message arrives and -when new addresses are generated during delivery. +when new addresses are generated during delivery. Rewriting is discussed in +chapter &<>&. .next &'local_scan'&: Private options for the &[local_scan()]& function. If you want to use this feature, you must set .code LOCAL_SCAN_HAS_OPTIONS=yes .endd -in &_Local/Makefile_& before building Exim. Full details of the -&[local_scan()]& facility are given in chapter &<>&. +in &_Local/Makefile_& before building Exim. Details of the &[local_scan()]& +facility are given in chapter &<>&. .endlist .cindex "configuration file" "leading white space in" @@ -4693,7 +4866,7 @@ up in a MySQL database. It helps to keep the file less cluttered if long strings such as SQL statements are defined separately as macros, for example: .code ALIAS_QUERY = select mailbox from user where \ - login=${quote_mysql:$local_part}; + login='${quote_mysql:$local_part}'; .endd This can then be used in a &(redirect)& router setting like this: .code @@ -4749,6 +4922,9 @@ space) and then the value. For example: .code qualify_domain = mydomain.example.com .endd +.cindex "hiding configuration option values" +.cindex "configuration options" "hiding value of" +.cindex "options" "hiding value of" Some option settings may contain sensitive data, for example, passwords for accessing databases. To stop non-admin users from using the &%-bP%& command line option to read these values, you can precede the option settings with the @@ -4796,13 +4972,11 @@ You can use whichever syntax you prefer. .section "Integer values" "SECID48" .cindex "integer configuration values" .cindex "format" "integer" -.new If an option's type is given as &"integer"&, the value can be given in decimal, hexadecimal, or octal. If it starts with a digit greater than zero, a decimal number is assumed. Otherwise, it is treated as an octal number unless it starts with the characters &"0x"&, in which case the remainder is interpreted as a hexadecimal number. -.wen If an integer value is followed by the letter K, it is multiplied by 1024; if it is followed by the letter M, it is multiplied by 1024x1024. When the values @@ -4815,20 +4989,16 @@ used. .section "Octal integer values" "SECID49" .cindex "integer format" .cindex "format" "octal integer" -.new If an option's type is given as &"octal integer"&, its value is always interpreted as an octal number, whether or not it starts with the digit zero. Such options are always output in octal. -.wen .section "Fixed point numbers" "SECID50" .cindex "fixed point configuration values" .cindex "format" "fixed point" -.new If an option's type is given as &"fixed-point"&, its value must be a decimal integer, optionally followed by a decimal point and up to three further digits. -.wen @@ -4855,7 +5025,6 @@ is perfectly acceptable, for example, to specify &"90m"& instead of &"1h30m"&. .section "String values" "SECTstrings" .cindex "string" "format of configuration values" .cindex "format" "string" -.new If an option's type is specified as &"string"&, the value can be specified with or without double-quotes. If it does not start with a double-quote, the value consists of the remainder of the line plus any continuation lines, starting at @@ -4864,7 +5033,6 @@ removed, and with no interpretation of the characters in the string. Because Exim removes comment lines (those beginning with #) at an early stage, they can appear in the middle of a multi-line string. The following two settings are therefore equivalent: -.wen .code trusted_users = uucp:mail trusted_users = uucp:\ @@ -4950,11 +5118,9 @@ list items, it is not ignored when parsing the list. The space after the first colon in the example above is necessary. If it were not there, the list would be interpreted as the two items 127.0.0.1:: and 1. -.new .section "Changing list separators" "SECID53" .cindex "list separator" "changing" .cindex "IPv6" "addresses in lists" -.wen Doubling colons in IPv6 addresses is an unwelcome chore, so a mechanism was introduced to allow the separator character to be changed. If a list begins with a left angle bracket, followed by any punctuation character, that @@ -4967,9 +5133,8 @@ This facility applies to all lists, with the exception of the list in &%log_file_path%&. It is recommended that the use of non-colon separators be confined to circumstances where they really are needed. -.new .cindex "list separator" "newline as" -.cindex "newline as list separator" +.cindex "newline" "as list separator" It is also possible to use newline and other control characters (those with code values less than 32, plus DEL) as separators in lists. Such separators must be provided literally at the time the list is processed. For options that @@ -4991,7 +5156,6 @@ Unlike printing character separators, which can be included in list items by doubling, it is not possible to include a control character as data when it is set as the separator. Two such characters in succession are interpreted as enclosing an empty list item. -.wen @@ -5808,6 +5972,9 @@ This causes any temporarily failing address to be retried every 15 minutes for 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address is not delivered after 4 days of temporary failure, it is bounced. +If the retry section is removed from the configuration, or is empty (that is, +if no retry rules are defined), Exim will not retry deliveries. This turns +temporary errors into permanent errors. .section "Rewriting configuration" "SECID58" @@ -5866,6 +6033,10 @@ password are correct. In the examples it just produces an error message. To make the authenticators work, you can use a string expansion expression like one of the examples in &<>&. +Beware that the sequence of the parameters to PLAIN and LOGIN differ; the +usercode and password are in different positions. &<>& +covers both. + .ecindex IIDconfiwal @@ -5885,13 +6056,11 @@ Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)). The documentation for the syntax and semantics of the regular expressions that -are supported by PCRE is included in plain text in the file -&_doc/pcrepattern.txt_& in the Exim distribution, and also in the HTML -tarbundle of Exim documentation. It describes in detail the features of the -regular expressions that PCRE supports, so no further description is included -here. The PCRE functions are called from Exim using the default option settings -(that is, with no PCRE options set), except that the PCRE_CASELESS option is -set when the matching is required to be case-insensitive. +are supported by PCRE is included in the PCRE distribution, and no further +description is included here. The PCRE functions are called from Exim using +the default option settings (that is, with no PCRE options set), except that +the PCRE_CASELESS option is set when the matching is required to be +case-insensitive. In most cases, when a regular expression is required in an Exim configuration, it has to start with a circumflex, in order to distinguish it from plain text @@ -5930,47 +6099,6 @@ $ is needed because string expansion also interprets dollar characters. -.section "Testing regular expressions" "SECID59" -.cindex "testing" "regular expressions" -.cindex "regular expressions" "testing" -.cindex "&'pcretest'&" -A program called &'pcretest'& forms part of the PCRE distribution and is built -with PCRE during the process of building Exim. It is primarily intended for -testing PCRE itself, but it can also be used for experimenting with regular -expressions. After building Exim, the binary can be found in the build -directory (it is not installed anywhere automatically). There is documentation -of various options in &_doc/pcretest.txt_&, but for simple testing, none are -needed. This is the output of a sample run of &'pcretest'&: -.display -&` re> `&&*&`/^([@]+)@.+\.(ac|edu)\.(?!kr)[a-z]{2}$/`&*& -&`data> `&&*&`x@y.ac.uk`&*& -&` 0: x@y.ac.uk`& -&` 1: x`& -&` 2: ac`& -&`data> `&&*&`x@y.ac.kr`&*& -&`No match`& -&`data> `&&*&`x@y.edu.com`&*& -&`No match`& -&`data> `&&*&`x@y.edu.co`&*& -&` 0: x@y.edu.co`& -&` 1: x`& -&` 2: edu`& -.endd -Input typed by the user is shown in bold face. After the &"re>"& prompt, a -regular expression enclosed in delimiters is expected. If this compiles without -error, &"data>"& prompts are given for strings against which the expression is -matched. An empty data line causes a new regular expression to be read. If the -match is successful, the captured substring values (that is, what would be in -the variables &$0$&, &$1$&, &$2$&, etc.) are shown. The above example tests for -an email address whose domain ends with either &"ac"& or &"edu"& followed by a -two-character top-level domain that is not &"kr"&. The local part is captured -in &$1$& and the &"ac"& or &"edu"& in &$2$&. - - - - - - . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -6117,13 +6245,26 @@ using Berkeley DB versions 3 or 4, it opens existing databases for reading with the DB_UNKNOWN option. This enables it to handle any of the types of database that the library supports, and can be useful for accessing DBM files created by other applications. (For earlier DB versions, DB_HASH is always used.) +.new +.next +.cindex "lookup" "dbmjz" +.cindex "lookup" "dbm &-- embedded NULs" +.cindex "sasldb2" +.cindex "dbmjz lookup type" +&(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is +interpreted as an Exim list; the elements of the list are joined together with +ASCII NUL characters to form the lookup key. An example usage would be to +authenticate incoming SMTP calls using the passwords from Cyrus SASL's +&_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own +&(cram_md5)& authenticator. +.wen .next .cindex "lookup" "dbmnz" .cindex "lookup" "dbm &-- terminating zero" .cindex "binary zero" "in lookup key" .cindex "Courier" .cindex "&_/etc/userdbshadow.dat_&" -.cindex "dmbnz lookup type" +.cindex "dbmnz lookup type" &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero is not included in the key that is passed to the DBM library. You may need this if you want to look up data in files that are created by or shared with some @@ -6135,10 +6276,12 @@ by default, but has an option to omit them (see section &<>&). .next .cindex "lookup" "dsearch" .cindex "dsearch lookup type" -&(dsearch)&: The given file must be a directory; this is searched for a file -whose name is the key. The key may not contain any forward slash characters. -The result of a successful lookup is the name of the file. An example of how -this lookup can be used to support virtual domains is given in section +&(dsearch)&: The given file must be a directory; this is searched for an entry +whose name is the key by calling the &[lstat()]& function. The key may not +contain any forward slash characters. If &[lstat()]& succeeds, the result of +the lookup is the name of the entry, which may be a file, directory, +symbolic link, or any other kind of directory entry. An example of how this +lookup can be used to support virtual domains is given in section &<>&. .next .cindex "lookup" "iplsearch" @@ -6150,7 +6293,7 @@ IPv6 addresses must be enclosed in quotes to prevent the first internal colon being interpreted as a key terminator. For example: .code 1.2.3.4: data for 1.2.3.4 -192.168.0.0/16 data for 192.168.0.0/16 +192.168.0.0/16: data for 192.168.0.0/16 "abcd::cdab": data for abcd::cdab "abcd:abcd::/32" data for abcd:abcd::/32 .endd @@ -6358,7 +6501,6 @@ not likely to be useful in normal operation. .next .cindex "whoson lookup type" .cindex "lookup" "whoson" -.new &(whoson)&: &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that allows a server to check whether a particular (dynamically allocated) IP address is currently allocated to a known (trusted) user and, optionally, to @@ -6374,7 +6516,6 @@ The query consists of a single IP address. The value returned is the name of the authenticated user, which is stored in the variable &$value$&. However, in this example, the data in &$value$& is not used; the result of the lookup is one of the fixed strings &"yes"& or &"no"&. -.wen .endlist @@ -6615,11 +6756,13 @@ is used on its own as the result. If the lookup does not succeed, the &`fail`& keyword causes a &'forced expansion failure'& &-- see section &<>& for an explanation of what this means. -The supported DNS record types are A, CNAME, MX, NS, PTR, SRV, and TXT, and, -when Exim is compiled with IPv6 support, AAAA (and A6 if that is also +.new +The supported DNS record types are A, CNAME, MX, NS, PTR, SPF, SRV, and TXT, +and, when Exim is compiled with IPv6 support, AAAA (and A6 if that is also configured). If no type is given, TXT is assumed. When the type is PTR, the data can be an IP address, written as normal; inversion and the addition of &%in-addr.arpa%& or &%ip6.arpa%& happens automatically. For example: +.wen .code ${lookup dnsdb{ptr=192.168.4.5}{$value}fail} .endd @@ -6644,6 +6787,23 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. +.cindex "TXT record" "in &(dnsdb)& lookup" +.cindex "SPF record" "in &(dnsdb)& lookup" +.new +For TXT records with multiple items of data, only the first item is returned, +unless a separator for them is specified using a comma after the separator +character followed immediately by the TXT record item separator. To concatenate +items without a separator, use a semicolon instead. For SPF records the +default behaviour is to concatenate multiple items without using a separator. +.wen +.code +${lookup dnsdb{>\n,: txt=a.b.example}} +${lookup dnsdb{>\n; txt=a.b.example}} +${lookup dnsdb{spf=example.org}} +.endd +It is permitted to specify a space as the separator character. Further +white space is ignored. + .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" By default, both the preference value and the host name are returned for @@ -6788,6 +6948,10 @@ The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports secure (encrypted) LDAP connections. The second of these ensures that an encrypted TLS connection is used. +With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular +LDAP connections, rather than the SSL-on-connect &`ldaps`&. +See the &%ldap_start_tls%& option. + .section "LDAP quoting" "SECID68" .cindex "LDAP" "quoting" @@ -7086,6 +7250,14 @@ operator is to double any quote characters within the text. .section "SQL lookups" "SECTsql" .cindex "SQL lookup types" +.cindex "MySQL" "lookup type" +.cindex "PostgreSQL lookup type" +.cindex "lookup" "MySQL" +.cindex "lookup" "PostgreSQL" +.cindex "Oracle" "lookup type" +.cindex "lookup" "Oracle" +.cindex "InterBase lookup type" +.cindex "lookup" "InterBase" Exim can support lookups in InterBase, MySQL, Oracle, PostgreSQL, and SQLite databases. Queries for these databases contain SQL statements, so an example might be @@ -7125,10 +7297,13 @@ with a newline between the data for each row. If any MySQL, PostgreSQL, Oracle, or InterBase lookups are used, the &%mysql_servers%&, &%pgsql_servers%&, &%oracle_servers%&, or &%ibase_servers%& option (as appropriate) must be set to a colon-separated list of server -information. Each item in the list is a slash-separated list of four items: -host name, database name, user name, and password. In the case of Oracle, the -host name field is used for the &"service name"&, and the database name field -is not used and should be empty. For example: +information. +(For MySQL and PostgreSQL only, the global option need not be set if all +queries contain their own server information &-- see section +&<>&.) Each item in the list is a slash-separated list of four +items: host name, database name, user name, and password. In the case of +Oracle, the host name field is used for the &"service name"&, and the database +name field is not used and should be empty. For example: .code hide oracle_servers = oracle.plc.example//userx/abcdwxyz .endd @@ -7141,8 +7316,10 @@ hide mysql_servers = localhost/users/root/secret:\ .endd For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but because this is a colon-separated list, the colon has to be doubled. For each -query, these parameter groups are tried in order until a connection and a query -succeeds. +query, these parameter groups are tried in order until a connection is made and +a query is successfully processed. The result of a query may be that no data is +found, but that is still a successful query. In other words, the list of +servers provides a backup facility, not a list of different places to look. The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b @@ -7152,6 +7329,46 @@ addition, escapes the percent and underscore characters. This cannot be done for MySQL because these escapes are not recognized in contexts where these characters are not special. +.section "Specifying the server in the query" "SECTspeserque" +For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase), +it is possible to specify a list of servers with an individual query. This is +done by starting the query with +.display +&`servers=`&&'server1:server2:server3:...'&&`;`& +.endd +Each item in the list may take one of two forms: +.olist +If it contains no slashes it is assumed to be just a host name. The appropriate +global option (&%mysql_servers%& or &%pgsql_servers%&) is searched for a host +of the same name, and the remaining parameters (database, user, password) are +taken from there. +.next +If it contains any slashes, it is taken as a complete parameter set. +.endlist +The list of servers is used in exactly the same way as the global list. +Once a connection to a server has happened and a query has been +successfully executed, processing of the lookup ceases. + +This feature is intended for use in master/slave situations where updates +are occurring and you want to update the master rather than a slave. If the +master is in the list as a backup for reading, you might have a global setting +like this: +.code +mysql_servers = slave1/db/name/pw:\ + slave2/db/name/pw:\ + master/db/name/pw +.endd +In an updating lookup, you could then write: +.code +${lookup mysql{servers=master; UPDATE ...} } +.endd +That query would then be sent only to the master server. If, on the other hand, +the master is not to be used for reading, and so is not present in the global +option, you can still update it by a query of this form: +.code +${lookup pgsql{servers=master/db/name/pw; UPDATE ...} } +.endd + .section "Special MySQL features" "SECID73" For MySQL, an empty host name or the use of &"localhost"& in &%mysql_servers%& @@ -7520,9 +7737,11 @@ differ only in their names. .cindex "@[] in a domain list" .cindex "domain list" "matching local IP interfaces" .cindex "domain literal" -If a pattern consists of the string &`@[]`& it matches any local IP interface -address, enclosed in square brackets, as in an email address that contains a -domain literal. +If a pattern consists of the string &`@[]`& it matches an IP address enclosed +in square brackets (as in an email address that contains a domain literal), but +only if that IP address is recognized as local for email routing purposes. The +&%local_interfaces%& and &%extra_local_interfaces%& options can be used to +control which of a host's several IP addresses are treated as local. In today's Internet, the use of domain literals is controversial. .next .cindex "@mx_any" @@ -7590,8 +7809,10 @@ list item such as &`*key.ex`& matches &'donkey.ex'& as well as If a pattern starts with a circumflex character, it is treated as a regular expression, and matched against the domain using a regular expression matching function. The circumflex is treated as part of the regular expression. -References to descriptions of the syntax of regular expressions are given in -chapter &<>&. +Email domains are case-independent, so this regular expression match is by +default case-independent, but you can make it case-dependent by starting it +with &`(?-i)`&. References to descriptions of the syntax of regular expressions +are given in chapter &<>&. &*Warning*&: Because domain lists are expanded before being processed, you must escape any backslash and dollar characters in the regular expression, or @@ -7640,7 +7861,7 @@ pattern must be an appropriate query for the lookup type, as described in chapter &<>&. For example: .code hold_domains = mysql;select domain from holdlist \ - where domain = '$domain'; + where domain = '${quote_mysql:$domain}'; .endd In most cases, the data that is looked up is not used (so for an SQL query, for example, it doesn't matter what field you select). Exim is interested only in @@ -7832,11 +8053,23 @@ The IP address of the subject host is masked using <&'number'&> as the mask length. A textual string is constructed from the masked value, followed by the mask, and this is used as the lookup key. For example, if the host's IP address is 192.168.34.6, the key that is looked up for the above example is -&"192.168.34.0/24"&. IPv6 addresses are converted to a text value using lower -case letters and dots as separators instead of the more usual colon, because -colon is the key terminator in &(lsearch)& files. Full, unabbreviated IPv6 +&"192.168.34.0/24"&. + +When an IPv6 address is converted to a string, dots are normally used instead +of colons, so that keys in &(lsearch)& files need not contain colons (which +terminate &(lsearch)& keys). This was implemented some time before the ability +to quote keys was made available in &(lsearch)& files. However, the more +recently implemented &(iplsearch)& files do require colons in IPv6 keys +(notated using the quoting facility) so as to distinguish them from IPv4 keys. +For this reason, when the lookup type is &(iplsearch)&, IPv6 addresses are +converted using colons and not dots. In all cases, full, unabbreviated IPv6 addresses are always used. +Ideally, it would be nice to tidy up this anomalous situation by changing to +colons in all cases, given that quoting is now available for &(lsearch)&. +However, this would be an incompatible change that might break some existing +configurations. + &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an IPv6 address) is not the same as specifying just &%net-%& without a number. In the former case the key strings include the mask value, whereas in the latter @@ -7894,7 +8127,11 @@ expression. .cindex "regular expressions" "in host list" .cindex "host list" "regular expression in" If the item starts with &"^"& it is taken to be a regular expression which is -matched against the host name. For example, +matched against the host name. Host names are case-independent, so this regular +expression match is by default case-independent, but you can make it +case-dependent by starting it with &`(?-i)`&. References to descriptions of the +syntax of regular expressions are given in chapter &<>&. For +example, .code ^(a|b)\.c\.d$ .endd @@ -7916,12 +8153,15 @@ required. .section "Behaviour when an IP address or name cannot be found" "SECTbehipnot" -.cindex "host" "lookup failures" +.cindex "host" "lookup failures, permanent" While processing a host list, Exim may need to look up an IP address from a name (see section &<>&), or it may need to look up a host name from an IP address (see section &<>&). In either case, the behaviour when it fails to find the information it is seeking is the same. +&*Note*&: This section applies to permanent lookup failures. It does &'not'& +apply to temporary DNS errors, whose handling is described in the next section. + .cindex "&`+include_unknown`&" .cindex "&`+ignore_unknown`&" By default, Exim behaves as if the host does not match the list. This may not @@ -7955,15 +8195,23 @@ Both &`+include_unknown`& and &`+ignore_unknown`& may appear in the same list. The effect of each one lasts until the next, or until the end of the list. -&*Note*&: This section applies to permanent lookup failures. It does &'not'& -apply to temporary DNS errors. They always cause a defer action (except when -&%dns_again_means_nonexist%& converts them into permanent errors). + +.section "Temporary DNS errors when looking up host information" &&& + "SECTtemdnserr" +.cindex "host" "lookup failures, temporary" +.cindex "&`+include_defer`&" +.cindex "&`+ignore_defer`&" +A temporary DNS lookup failure normally causes a defer action (except when +&%dns_again_means_nonexist%& converts it into a permanent error). However, +host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to +&`+ignore_unknown`& and &`+include_unknown`&, as described in the previous +section. These options should be used with care, probably only in non-critical +host lists such as whitelists. .section "Host list patterns for single-key lookups by host name" &&& "SECThoslispatnamsk" -.cindex "host" "lookup failures" .cindex "unknown host name" .cindex "host list" "matching host name" If a pattern is of the form @@ -8317,6 +8565,13 @@ start of a portion of the string that is interpreted and replaced as described below in section &<>& onwards. Backslash is used as an escape character, as described in the following section. +Whether a string is expanded depends upon the context. Usually this is solely +dependent upon the option for which a value is sought; in this documentation, +options for which string expansion is performed are marked with † after +the data type. ACL rules always expand strings. A couple of expansion +conditions do not expand some of the brace-delimited branches, for security +reasons. + .section "Literal text in expanded strings" "SECTlittext" @@ -8439,6 +8694,10 @@ below. The operator notation is used for simple expansion items that have just one argument, because it reduces the number of braces and therefore makes the string easier to understand. +.vitem &*$bheader_*&<&'header&~name'&>&*:*&&~or&~&*$bh_*&<&'header&~name'&>&*:*& +This item inserts &"basic"& header lines. It is described with the &%header%& +expansion item below. + .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&& {*&<&'arg'&>&*}...}*&" .cindex &%dlfunc%& @@ -8547,7 +8806,6 @@ yields &"99"&. Two successive separators mean that the field between them is empty (for example, the fifth field above). -.new .vitem &*${filter{*&<&'string'&>&*}{*&<&'condition'&>&*}}*& .cindex "list" "selecting by condition" .cindex "expansion" "selecting from list by condition" @@ -8564,7 +8822,6 @@ ${filter{a:b:c}{!eq{$item}{b}} .endd yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored to what it was before. See also the &*map*& and &*reduce*& expansion items. -.wen .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& @@ -8598,14 +8855,10 @@ letters appear. For example: .endd .vitem "&*$header_*&<&'header&~name'&>&*:*&&~or&~&&& - &*$h_*&<&'header&~name'&>&*:*&" -See &*$rheader*& below. - -.vitem "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&& - &*$bh_*&<&'header&~name'&>&*:*&" -See &*$rheader*& below. - -.vitem "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&& + &*$h_*&<&'header&~name'&>&*:*&" &&& + "&*$bheader_*&<&'header&~name'&>&*:*&&~or&~&&& + &*$bh_*&<&'header&~name'&>&*:*&" &&& + "&*$rheader_*&<&'header&~name'&>&*:*&&~or&~&&& &*$rh_*&<&'header&~name'&>&*:*&" .cindex "expansion" "header insertion" .vindex "&$header_$&" @@ -8839,7 +9092,6 @@ ${lookup nisplus {[name=$local_part],passwd.org_dir:gcos} \ .endd -.new .vitem &*${map{*&<&'string1'&>&*}{*&<&'string2'&>&*}}*& .cindex "expansion" "list creation" .vindex "&$item$&" @@ -8855,7 +9107,6 @@ ${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}} expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the value of &$item$& is restored to what it was before. See also the &*filter*& and &*reduce*& expansion items. -.wen .vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& .cindex "expansion" "numeric hash" @@ -9022,7 +9273,6 @@ The &(redirect)& router has an option called &%forbid_filter_readsocket%& which locks out the use of this expansion item in filter files. -.new .vitem &*${reduce{*&<&'string1'&>}{<&'string2'&>&*}{*&<&'string3'&>&*}}*& .cindex "expansion" "reducing a list to a scalar" .cindex "list" "reducing to a scalar" @@ -9048,9 +9298,8 @@ ${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}} At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are restored to what they were before. See also the &*filter*& and &*map*& expansion items. -.wen -.vitem &*$rheader_*&<&'header&~name'&>&*:&~or&~$rh_*&<&'header&~name'&>&*:*& +.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*& This item inserts &"raw"& header lines. It is described with the &%header%& expansion item above. @@ -9218,7 +9467,6 @@ header line, and the effective address is extracted from it. If the string does not parse successfully, the result is empty. -.new .vitem &*${addresses:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2822 address handling" .cindex "&%addresses%& expansion item" @@ -9239,7 +9487,6 @@ expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular) expansion item, which extracts the working address from a single RFC2822 address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of processing lists. -.wen .vitem &*${base62:*&<&'digits'&>&*}*& @@ -9304,9 +9551,10 @@ decimal, even if they start with a leading zero; hexadecimal numbers are not permitted. This can be useful when processing numbers extracted from dates or times, which often do have leading zeros. -A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024, +A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024 +or 1024*1024*1024, respectively. Negative numbers are supported. The result of the computation is -a decimal representation of the answer (without &"K"& or &"M"&). For example: +a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example: .display &`${eval:1+1} `& yields 2 @@ -9519,6 +9767,38 @@ For single-key lookup types, no quoting is ever necessary and this operator yields an unchanged string. +.vitem &*${randint:*&<&'n'&>&*}*& +.cindex "random number" +This operator returns a somewhat random number which is less than the +supplied number and is at least 0. The quality of this randomness depends +on how Exim was built; the values are not suitable for keying material. +If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. +.new +If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used, +for versions of GnuTLS with that function. +.wen +Otherwise, the implementation may be arc4random(), random() seeded by +srandomdev() or srandom(), or a custom implementation even weaker than +random(). + + +.vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*& +.cindex "expansion" "IP address" +This operator reverses an IP address; for IPv4 addresses, the result is in +dotted-quad decimal form, while for IPv6 addreses the result is in +dotted-nibble hexadecimal form. In both cases, this is the "natural" form +for DNS. For example, +.code +${reverse_ip:192.0.2.4} +${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3} +.endd +returns +.code +4.2.0.192 +3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 +.endd + + .vitem &*${rfc2047:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "expansion operator" @@ -9537,7 +9817,6 @@ string, using as many &"encoded words"& as necessary to encode all the characters. -.new .vitem &*${rfc2047d:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "decoding" @@ -9546,7 +9825,10 @@ This operator decodes strings that are encoded as per RFC 2047. Binary zero bytes are replaced by question marks. Characters are converted into the character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are not recognized unless &%check_rfc2047_length%& is set false. -.wen + +&*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to +access a header line, RFC 2047 decoding is done automatically. You do not need +to use this operator as well. @@ -9678,6 +9960,42 @@ lower case), signifying multiplication by 1024 or 1024*1024, respectively. As a special case, the numerical value of an empty string is taken as zero. +In all cases, a relative comparator OP is testing if <&'string1'&> OP +<&'string2'&>; the above example is checking if &$message_size$& is larger than +10M, not if 10M is larger than &$message_size$&. + + +.vitem &*bool&~{*&<&'string'&>&*}*& +.cindex "expansion" "boolean parsing" +.cindex "&%bool%& expansion condition" +This condition turns a string holding a true or false representation into +a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"& +(case-insensitively); also positive integer numbers map to true if non-zero, +false if zero. +An empty string is treated as false. +Leading and trailing whitespace is ignored; +thus a string consisting only of whitespace is false. +All other string values will result in expansion failure. + +When combined with ACL variables, this expansion condition will let you +make decisions in one place and act on those decisions in another place. +For example: +.code +${if bool{$acl_m_privileged_sender} ... +.endd + + +.vitem &*bool_lax&~{*&<&'string'&>&*}*& +.cindex "expansion" "boolean parsing" +.cindex "&%bool_lax%& expansion condition" +Like &%bool%&, this condition turns a string into a boolean state. But +where &%bool%& accepts a strict set of strings, &%bool_lax%& uses the same +loose definition that the Router &%condition%& option uses. The empty string +and the values &"false"&, &"no"& and &"0"& map to false, all others map to +true. Leading and trailing whitespace is ignored. + +Note that where &"bool{00}"& is false, &"bool_lax{00}"& is true. + .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "expansion" "encrypted comparison" .cindex "encrypted strings, comparing" @@ -9811,7 +10129,6 @@ This condition, which has no data, is true during a message's first delivery attempt. It is false during any subsequent delivery attempts. -.new .vitem "&*forall{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" &&& "&*forany{*&<&'a list'&>&*}{*&<&'a condition'&>&*}*&" .cindex "list" "iterative conditions" @@ -9841,7 +10158,6 @@ ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}} .endd The value of &$item$& is saved and restored while &*forany*& or &*forall*& is being processed, to enable these expansion items to be nested. -.wen .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& @@ -9866,6 +10182,25 @@ string is lexically greater than the second string. For &%gt%& the comparison includes the case of letters, whereas for &%gti%& the comparison is case-independent. +.new +.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& + &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& +.cindex "string" "comparison" +.cindex "list" "iterative conditions" +Both strings are expanded; the second string is treated as a list of simple +strings; if the first string is a member of the second, then the condition +is true. + +These are simpler to use versions of the more powerful &*forany*& condition. +Examples, and the &*forany*& equivalents: +.code +${if inlist{needle}{foo:needle:bar}} + ${if forany{foo:needle:bar}{eq{$item}{needle}}} +${if inlisti{Needle}{fOo:NeeDLE:bAr}} + ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}} +.endd +.wen + .vitem &*isip&~{*&<&'string'&>&*}*& &&& &*isip4&~{*&<&'string'&>&*}*& &&& &*isip6&~{*&<&'string'&>&*}*& @@ -9876,13 +10211,22 @@ case-independent. .cindex "&%isip6%& expansion condition" The substring is first expanded, and then tested to see if it has the form of an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas -&%isip4%& and &%isip6%& test just for IPv4 or IPv6 addresses, respectively. For -example, you could use +&%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses. + +For an IPv4 address, the test is for four dot-separated components, each of +which consists of from one to three digits. For an IPv6 address, up to eight +colon-separated components are permitted, each containing from one to four +hexadecimal digits. There may be fewer than eight components if an empty +component (adjacent colons) is present. Only one empty component is permitted. + +&*Note*&: The checks are just on the form of the address; actual numerical +values are not considered. Thus, for example, 999.999.999.999 passes the IPv4 +check. The main use of these tests is to distinguish between IP addresses and +host names, or between IPv4 and IPv6 addresses. For example, you could use .code ${if isip4{$sender_host_address}... .endd -to test which version of IP an incoming SMTP connection is using. - +to test which IP version an incoming SMTP connection is using. .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*& .cindex "LDAP" "use for authentication" @@ -9967,10 +10311,12 @@ See &*match_local_part*&. .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "&%match_ip%& expansion condition" +.new This condition matches an IP address to a list of IP address patterns. It must be followed by two argument strings. The first (after expansion) must be an IP -address or an empty string. The second (after expansion) is a restricted host +address or an empty string. The second (not expanded) is a restricted host list that can match only an IP address, not a host name. For example: +.wen .code ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}} .endd @@ -9995,7 +10341,6 @@ where the first item in the list is the empty string. .next The item @[] matches any of the local host's interface addresses. .next -.new Single-key lookups are assumed to be like &"net-"& style lookups in host lists, even if &`net-`& is not specified. There is never any attempt to turn the IP address into a host name. The most common type of linear search for @@ -10015,9 +10360,13 @@ just as easy to use the fact that a lookup is itself a condition, and write: .code ${lookup{${mask:$sender_host_address/24}}dbm{/a/file}... .endd -.wen .endlist ilist +.new +Note that <&'string2'&> is not itself subject to string expansion, unless +Exim was built with the EXPAND_LISTMATCH_RHS option. +.wen + Consult section &<>& for further details of these patterns. .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -10045,6 +10394,11 @@ item can be used, as in all address lists, to cause subsequent items to have their local parts matched casefully. Domains are always matched caselessly. +.new +Note that <&'string2'&> is not itself subject to string expansion, unless +Exim was built with the EXPAND_LISTMATCH_RHS option. +.wen + &*Note*&: Host lists are &'not'& supported in this way. This is because hosts have two identities: a name and an IP address, and it is not clear how to specify cleanly how such a test would work. However, IP addresses can be @@ -10124,6 +10478,10 @@ configuration, you might have this: .code server_condition = ${if pwcheck{$auth1:$auth2}} .endd +Again, for a PLAIN authenticator configuration, this would be: +.code +server_condition = ${if pwcheck{$auth2:$auth3}} +.endd .vitem &*queue_running*& .cindex "queue runner" "detecting when delivering from" .cindex "expansion" "queue runner test" @@ -10243,7 +10601,6 @@ support for TLS or the content scanning extension. .vlist .vitem "&$0$&, &$1$&, etc" .cindex "numerical variables (&$1$& &$2$& etc)" -.new When a &%match%& expansion condition succeeds, these variables contain the captured substrings identified by the regular expression during subsequent processing of the success string of the containing &%if%& expansion item. @@ -10253,9 +10610,7 @@ variables may also be set externally by some other matching process which precedes the expansion of the string. For example, the commands available in Exim filter files include an &%if%& command with its own regular expression matching condition. -.wen -.new .vitem "&$acl_c...$&" Values can be placed in these variables by the &%set%& modifier in an ACL. They can be given any name that starts with &$acl_c$& and is at least six characters @@ -10276,7 +10631,6 @@ also reset by MAIL, RSET, EHLO, HELO, and after starting a TLS session. When a message is received, the values of these variables are saved with the message, and can be accessed by filters, routers, and transports during subsequent delivery. -.wen .vitem &$acl_verify_message$& .vindex "&$acl_verify_message$&" @@ -10390,6 +10744,15 @@ is empty and &$authentication_failed$& is set to &"1"&). Failure includes any negative response to an AUTH command, including (for example) an attempt to use an undefined mechanism. +.new +.vitem &$av_failed$& +.cindex "content scanning" "AV scanner failure" +This variable is available when Exim is compiled with the content-scanning +extension. It is set to &"0"& by default, but will be set to &"1"& if any +problem occurs with the virus scanner (specified by &%av_scanner%&) during +the ACL malware condition. +.wen + .vitem &$body_linecount$& .cindex "message body" "line count" .cindex "body of message" "line count" @@ -10403,7 +10766,7 @@ number of lines in the message's body. See also &$message_linecount$&. .cindex "binary zero" "in message body" .vindex "&$body_zerocount$&" When a message is being received or delivered, this variable contains the -number of binary zero bytes in the message's body. +number of binary zero bytes (ASCII NULs) in the message's body. .vitem &$bounce_recipient$& .vindex "&$bounce_recipient$&" @@ -10455,25 +10818,19 @@ This variable is available when Exim is compiled with the content-scanning extension and the obsolete &%demime%& condition. For details, see section &<>&. - -.vitem &$dnslist_domain$& -.cindex "black list (DNS)" +.vitem &$dnslist_domain$& &&& + &$dnslist_matched$& &&& + &$dnslist_text$& &&& + &$dnslist_value$& .vindex "&$dnslist_domain$&" -When a client host is found to be on a DNS (black) list, -the list's domain name is put into this variable so that it can be included in -the rejection message. - -.vitem &$dnslist_text$& +.vindex "&$dnslist_matched$&" .vindex "&$dnslist_text$&" -When a client host is found to be on a DNS (black) list, the -contents of any associated TXT record are placed in this variable. - -.vitem &$dnslist_value$& .vindex "&$dnslist_value$&" -When a client host is found to be on a DNS (black) list, -the IP address from the resource record is placed in this variable. -If there are multiple records, all the addresses are included, comma-space -separated. +.cindex "black list (DNS)" +When a DNS (black) list lookup succeeds, these variables are set to contain +the following data from the lookup: the list's domain name, the key that was +looked up, the contents of any associated TXT record, and the value from the +main A record. See section &<>& for more details. .vitem &$domain$& .vindex "&$domain$&" @@ -10664,14 +11021,12 @@ This is an obsolete name for &$received_ip_address$&. .vindex "&$interface_port$&" This is an obsolete name for &$received_port$&. -.new .vitem &$item$& .vindex "&$item$&" This variable is used during the expansion of &*forall*& and &*forany*& -conditions (see section &<>&), and &*filter*&, &*man*&, and +conditions (see section &<>&), and &*filter*&, &*map*&, and &*reduce*& items (see section &<>&). In other circumstances, it is empty. -.wen .vitem &$ldap_dn$& .vindex "&$ldap_dn$&" @@ -10681,7 +11036,7 @@ lookup. .vitem &$load_average$& .vindex "&$load_average$&" -This variable contains the system load average, multiplied by 1000 to that it +This variable contains the system load average, multiplied by 1000 so that it is an integer. For example, if the load average is 0.21, the value of the variable is 210. The value is recomputed every time the variable is referenced. @@ -10817,6 +11172,13 @@ This variable is available when Exim is compiled with the content-scanning extension. It is set to the name of the virus that was found when the ACL &%malware%& condition is true (see section &<>&). +.vitem &$max_received_linelength$& +.vindex "&$max_received_linelength$&" +.cindex "maximum" "line length" +.cindex "line length" "maximum" +This variable contains the number of bytes in the longest line that was +received as part of the message, not counting the line termination +character(s). .vitem &$message_age$& .cindex "message" "age of" @@ -10830,13 +11192,17 @@ delivery attempt. .cindex "message body" "in expansion" .cindex "binary zero" "in message body" .vindex "&$message_body$&" -This variable contains the initial portion of a message's -body while it is being delivered, and is intended mainly for use in filter -files. The maximum number of characters of the body that are put into the -variable is set by the &%message_body_visible%& configuration option; the -default is 500. Newlines are converted into spaces to make it easier to search -for phrases that might be split over a line break. -Binary zeros are also converted into spaces. +.oindex "&%message_body_visible%&" +This variable contains the initial portion of a message's body while it is +being delivered, and is intended mainly for use in filter files. The maximum +number of characters of the body that are put into the variable is set by the +&%message_body_visible%& configuration option; the default is 500. + +.oindex "&%message_body_newlines%&" +By default, newlines are converted into spaces in &$message_body$&, to make it +easier to search for phrases that might be split over a line break. However, +this can be disabled by setting &%message_body_newlines%& to be true. Binary +zeros are always converted into spaces. .vitem &$message_body_end$& .cindex "body of message" "expansion variable" @@ -10888,8 +11254,15 @@ number of lines received. Before delivery happens (that is, before filters, routers, and transports run) the count is increased to include the &'Received:'& header line that Exim standardly adds, and also any other header lines that are added by ACLs. The blank line that separates the message header -from the body is not counted. Here is an example of the use of this variable in -a DATA ACL: +from the body is not counted. + +As with the special case of &$message_size$&, during the expansion of the +appendfile transport's maildir_tag option in maildir format, the value of +&$message_linecount$& is the precise size of the number of newlines in the +file that has been written (minus one for the blank line between the +header and the body). + +Here is an example of the use of this variable in a DATA ACL: .code deny message = Too many lines in message header condition = \ @@ -10912,7 +11285,7 @@ precise size of the file that has been written. See also &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&. .cindex "RCPT" "value of &$message_size$&" -While running an ACL at the time of an SMTP RCPT command, &$message_size$& +While running a per message ACL (mail/rcpt/predata), &$message_size$& contains the size supplied on the MAIL command, or -1 if no size was given. The value may not, of course, be truthful. @@ -11179,9 +11552,7 @@ is, the ACLs defined by &%acl_smtp_predata%&, &%acl_smtp_data%&, &%acl_smtp_mime%&, &%acl_not_smtp_start%&, &%acl_not_smtp%&, and &%acl_not_smtp_mime%&. .next -.new From within a &[local_scan()]& function. -.wen .endlist @@ -11413,7 +11784,6 @@ In an ACL, when a sender verification fails, this variable contains information about the failure. The details are the same as for &$recipient_verify_failure$&. -.new .vitem &$sending_ip_address$& .vindex "&$sending_ip_address$&" This variable is set whenever an outgoing SMTP connection to another host has @@ -11427,7 +11797,6 @@ connections, see &$received_ip_address$&. This variable is set whenever an outgoing SMTP connection to another host has been set up. It contains the local port that is being used. For incoming connections, see &$received_port$&. -.wen .vitem &$smtp_active_hostname$& .vindex "&$smtp_active_hostname$&" @@ -11458,7 +11827,6 @@ argument, that is, the text that follows the command name, with leading white space removed. Following the introduction of &$smtp_command$&, this variable is somewhat redundant, but is retained for backwards compatibility. -.new .vitem &$smtp_count_at_connection_start$& .vindex "&$smtp_count_at_connection_start$&" This variable is set greater than zero only in processes spawned by the Exim @@ -11470,7 +11838,6 @@ never changes. It is only an approximation of how many incoming connections there actually are, because many other connections may come and go while a single connection is being processed. When a child process terminates, the daemon decrements its copy of the variable. -.wen .vitem "&$sn0$& &-- &$sn9$&" These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators @@ -11517,6 +11884,16 @@ command in a filter file. Its use is explained in the description of that command, which can be found in the separate document entitled &'Exim's interfaces to mail filtering'&. +.new +.vitem &$tls_bits$& +.vindex "&$tls_bits$&" +Contains an approximation of the TLS cipher's bit-strength; the meaning of +this depends upon the TLS implementation used. +If TLS has not been negotiated, the value will be 0. +The value of this is automatically fed into the Cyrus SASL authenticator +when acting as a server, to specify the "external SSF" (a SASL term). +.wen + .vitem &$tls_certificate_verified$& .vindex "&$tls_certificate_verified$&" This variable is set to &"1"& if a TLS certificate was verified when the @@ -11527,15 +11904,42 @@ message was received, and &"0"& otherwise. When a message is received from a remote host over an encrypted SMTP connection, this variable is set to the cipher suite that was negotiated, for example DES-CBC3-SHA. In other circumstances, in particular, for message -received over unencrypted connections, the variable is empty. See chapter -&<>& for details of TLS support. +received over unencrypted connections, the variable is empty. Testing +&$tls_cipher$& for emptiness is one way of distinguishing between encrypted and +non-encrypted connections during ACL processing. + +The &$tls_cipher$& variable retains its value during message delivery, except +when an outward SMTP delivery takes place via the &(smtp)& transport. In this +case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made, +and then set to the outgoing cipher suite if one is negotiated. See chapter +&<>& for details of TLS support and chapter &<>& for +details of the &(smtp)& transport. .vitem &$tls_peerdn$& .vindex "&$tls_peerdn$&" When a message is received from a remote host over an encrypted SMTP connection, and Exim is configured to request a certificate from the client, the value of the Distinguished Name of the certificate is made available in the -&$tls_peerdn$& during subsequent processing. +&$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the +value is retained during message delivery, except during outbound SMTP +deliveries. + +.new +.vitem &$tls_sni$& +.vindex "&$tls_sni$&" +.cindex "TLS" "Server Name Indication" +When a TLS session is being established, if the client sends the Server +Name Indication extension, the value will be placed in this variable. +If the variable appears in &%tls_certificate%& then this option and +some others, described in &<>&, +will be re-expanded early in the TLS session, to permit +a different certificate to be presented (and optionally a different key to be +used) to the client, based upon the value of the SNI extension. + +The value will be retained for the lifetime of the message. During outbound +SMTP deliveries, it reflects the value of the &%tls_sni%& option on +the transport. +.wen .vitem &$tod_bsdinbox$& .vindex "&$tod_bsdinbox$&" @@ -11546,6 +11950,10 @@ files, for example: Thu Oct 17 17:14:09 1995. .vindex "&$tod_epoch$&" The time and date as a number of seconds since the start of the Unix epoch. +.vitem &$tod_epoch_l$& +.vindex "&$tod_epoch_l$&" +The time and date as a number of microseconds since the start of the Unix epoch. + .vitem &$tod_full$& .vindex "&$tod_full$&" A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40 @@ -11577,8 +11985,8 @@ by ISO 8601, for example: 20030221154023Z. .vitem &$value$& .vindex "&$value$&" This variable contains the result of an expansion lookup, extraction operation, -or external command, as described above. &new("It is also used during a -&*reduce*& expansion.") +or external command, as described above. It is also used during a +&*reduce*& expansion. .vitem &$version_number$& .vindex "&$version_number$&" @@ -12078,6 +12486,7 @@ listed in more than one group. .row &%disable_ipv6%& "do no IPv6 processing" .row &%keep_malformed%& "for broken files &-- should not happen" .row &%localhost_number%& "for unique message ids in clusters" +.row &%message_body_newlines%& "retain newlines in &$message_body$&" .row &%message_body_visible%& "how much to show in &$message_body$&" .row &%mua_wrapper%& "run in &""MUA wrapper""& mode" .row &%print_topbitchars%& "top-bit characters are printing" @@ -12144,12 +12553,20 @@ listed in more than one group. .section "Data lookups" "SECID101" .table2 +.row &%ibase_servers%& "InterBase servers" +.row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's" +.row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's" +.row &%ldap_cert_file%& "client cert file for LDAP" +.row &%ldap_cert_key%& "client key file for LDAP" +.row &%ldap_cipher_suite%& "TLS negotiation preference control" .row &%ldap_default_servers%& "used if no server in query" +.row &%ldap_require_cert%& "action to take without LDAP server cert" +.row &%ldap_start_tls%& "require TLS within LDAP" .row &%ldap_version%& "set protocol version" .row &%lookup_open_max%& "lookup files held open" -.row &%mysql_servers%& "as it says" -.row &%oracle_servers%& "as it says" -.row &%pgsql_servers%& "as it says" +.row &%mysql_servers%& "default MySQL servers" +.row &%oracle_servers%& "Oracle servers" +.row &%pgsql_servers%& "default PostgreSQL servers" .row &%sqlite_lock_timeout%& "as it says" .endtable @@ -12192,6 +12609,7 @@ listed in more than one group. .row &%check_spool_space%& "before accepting a message" .row &%deliver_queue_load_max%& "no queue deliveries if load high" .row &%queue_only_load%& "queue incoming if load high" +.row &%queue_only_load_latch%& "don't re-evaluate load for each message" .row &%queue_run_max%& "maximum simultaneous queue runners" .row &%remote_max_parallel%& "parallel SMTP delivery per message" .row &%smtp_accept_max%& "simultaneous incoming connections" @@ -12219,6 +12637,7 @@ listed in more than one group. .row &%acl_smtp_auth%& "ACL for AUTH" .row &%acl_smtp_connect%& "ACL for connection" .row &%acl_smtp_data%& "ACL for DATA" +.row &%acl_smtp_dkim%& "ACL for DKIM verification" .row &%acl_smtp_etrn%& "ACL for ETRN" .row &%acl_smtp_expn%& "ACL for EXPN" .row &%acl_smtp_helo%& "ACL for EHLO or HELO" @@ -12270,12 +12689,12 @@ listed in more than one group. .section "TLS" "SECID108" .table2 -.row &new(&%gnutls_require_kx%&) "control GnuTLS key exchanges" -.row &new(&%gnutls_require_mac%&) "control GnuTLS MAC algorithms" -.row &new(&%gnutls_require_protocols%&) "control GnuTLS protocols" +.row &%gnutls_compat_mode%& "use GnuTLS compatibility mode" +.row &%openssl_options%& "adjust OpenSSL compatibility options" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" .row &%tls_certificate%& "location of server certificate" .row &%tls_crl%& "certificate revocation list" +.row &%tls_dh_max_bits%& "clamp D-H bit count suggestion" .row &%tls_dhparam%& "DH parameters for server" .row &%tls_on_connect_ports%& "specify SSMTP (SMTPS) ports" .row &%tls_privatekey%& "location of server private key" @@ -12420,12 +12839,14 @@ See also the &'Policy controls'& section above. .row &%dns_ipv4_lookup%& "only v4 lookup for these domains" .row &%dns_retrans%& "parameter for resolver" .row &%dns_retry%& "parameter for resolver" +.row &%dns_use_edns0%& "parameter for resolver" .row &%hold_domains%& "hold delivery for these domains" .row &%local_interfaces%& "for routing checks" .row &%queue_domains%& "no immediate delivery for these" .row &%queue_only%& "no immediate delivery at all" .row &%queue_only_file%& "no immediate delivery if file exists" .row &%queue_only_load%& "no immediate delivery if load is high" +.row &%queue_only_load_latch%& "don't re-evaluate load for each message" .row &%queue_only_override%& "allow command line to override" .row &%queue_run_in_order%& "order of arrival" .row &%queue_run_max%& "of simultaneous queue runners" @@ -12446,7 +12867,7 @@ See also the &'Policy controls'& section above. .row &%bounce_return_message%& "include original message in bounce" .row &%bounce_return_size_limit%& "limit on returned message" .row &%bounce_sender_authentication%& "send authenticated sender with bounce" -.row &new(&%dsn_from%&) "set &'From:'& contents in bounces" +.row &%dsn_from%& "set &'From:'& contents in bounces" .row &%errors_copy%& "copy bounce messages" .row &%errors_reply_to%& "&'Reply-to:'& in bounces" .row &%delay_warning%& "time schedule" @@ -12462,14 +12883,23 @@ See also the &'Policy controls'& section above. Those options that undergo string expansion before use are marked with †. -.option accept_8bitmime main boolean false +.new +.option accept_8bitmime main boolean true .cindex "8BITMIME" .cindex "8-bit characters" This option causes Exim to send 8BITMIME in its response to an SMTP EHLO command, and to accept the BODY= parameter on MAIL commands. However, though Exim is 8-bit clean, it is not a protocol converter, and it takes no steps to do anything special with messages received by this route. -Consequently, this option is turned off by default. + +Historically Exim kept this option off by default, but the maintainers +feel that in today's Internet, this causes more problems than it solves. +It now defaults to true. +A more detailed analysis of the issues is provided by Dan Bernstein: +.display +&url(http://cr.yp.to/smtp/8bitmime.html) +.endd +.wen .option acl_not_smtp main string&!! unset .cindex "&ACL;" "for non-SMTP messages" @@ -12671,17 +13101,17 @@ saying &"keep on trying, even though there are big problems"&. &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not thought to be very useful any more, and its use should probably be avoided. + .option av_scanner main string "see below" This option is available if Exim is built with the content-scanning extension. It specifies which anti-virus scanner to use. The default value is: .code sophie:/var/run/sophie .endd -If the value of &%av_scanner%& starts with dollar character, it is expanded +If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. See section &<>& for further details. - .option bi_command main string unset .oindex "&%-bi%&" This option supplies the name of a command that is run when Exim is called with @@ -12784,7 +13214,7 @@ section &<>& for details of the caching. This option defines the &"random"& local part that can be used as part of callout verification. The default value is .code -$primary_host_name-$tod_epoch-testing +$primary_hostname-$tod_epoch-testing .endd See section &<>& for details of how this value is used. @@ -12948,8 +13378,7 @@ should not be present in incoming messages, and this option causes them to be removed at the time the message is received, to avoid any problems that might occur when a delivered message is subsequently sent on to some other recipient. -.new -.option disable_fnync main boolean false +.option disable_fsync main boolean false .cindex "&[fsync()]&, disabling" This option is available only if Exim was built with the compile-time option ENABLE_DISABLE_FSYNC. When this is not set, a reference to &%disable_fsync%& in @@ -12962,7 +13391,6 @@ When &%disable_fsync%& is set true, Exim no longer calls &[fsync()]& to force updated files' data to be written to disc before continuing. Unexpected events such as crashes and power outages may cause data to be lost or scrambled. Here be Dragons. &*Beware.*& -.wen .option disable_ipv6 main boolean false @@ -13008,7 +13436,7 @@ dns_check_names_pattern = \ (?i)^(?>(?(1)\.|())[^\W_](?>[a-z0-9/-]*[^\W_])?)+$ .endd which permits only letters, digits, slashes, and hyphens in components, but -they must start and end with a letter or digit. Hyphens are not, in fact, +they must start and end with a letter or digit. Slashes are not, in fact, permitted in host names, but they are found in certain NS records (which can be accessed in Exim by using a &%dnsdb%& lookup). If you set &%allow_utf8_domains%&, you must modify this pattern, or set the option to an @@ -13053,12 +13481,24 @@ to set in them. See &%dns_retrans%& above. +.new +.option dns_use_edns0 main integer -1 +.cindex "DNS" "resolver options" +.cindex "DNS" "EDNS0" +If this option is set to a non-negative number then Exim will initialise the +DNS resolver library to either use or not use EDNS0 extensions, overriding +the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0 +on. + +If the resolver library does not support EDNS0 then this option has no effect. +.wen + + .option drop_cr main boolean false This is an obsolete option that is now a no-op. It used to affect the way Exim handled CR and LF characters in incoming messages. What happens now is described in section &<>&. -.new .option dsn_from main "string&!!" "see below" .cindex "&'From:'& header line" "in bounces" .cindex "bounce messages" "&'From:'& line, specifying" @@ -13070,7 +13510,6 @@ dsn_from = Mail Delivery System .endd The value is expanded every time it is needed. If the expansion fails, a panic is logged, and the default value is used. -.wen .option envelope_to_remove main boolean true .cindex "&'Envelope-to:'& header line" @@ -13263,20 +13702,10 @@ gecos_name = $1 See &%gecos_name%& above. -.new -.option gnutls_require_kx main string unset -This option controls the key exchange mechanisms when GnuTLS is used in an Exim -server. For details, see section &<>&. - -.option gnutls_require_mac main string unset -This option controls the MAC algorithms when GnuTLS is used in an Exim -server. For details, see section &<>&. - -.option gnutls_require_protocols main string unset -This option controls the protocols when GnuTLS is used in an Exim -server. For details, see section &<>&. -.wen - +.option gnutls_compat_mode main boolean unset +This option controls whether GnuTLS is used in compatibility mode in an Exim +server. This reduces security slightly, but improves interworking with older +implementations of TLS. .option headers_charset main string "see below" This option sets a default character set for translating from encoded MIME @@ -13348,10 +13777,10 @@ do. By default, Exim just checks the syntax of HELO and EHLO commands (see &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like to do more extensive checking of the data supplied by these commands. The ACL -condition &`verify`& &`=`& &`helo`& is provided to make this possible. +condition &`verify = helo`& is provided to make this possible. Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&) to force the check to occur. From release 4.53 onwards, this is no longer -necessary. If the check has not been done before &`verify`& &`=`& &`helo`& is +necessary. If the check has not been done before &`verify = helo`& is encountered, it is done at that time. Consequently, this option is obsolete. Its specification is retained here for backwards compatibility. @@ -13373,7 +13802,7 @@ available) yields the calling host address. However, the EHLO or HELO command is not rejected if any of the checks fail. Processing continues, but the result of the check is remembered, and can -be detected later in an ACL by the &`verify`& &`=`& &`helo`& condition. +be detected later in an ACL by the &`verify = helo`& condition. .option helo_verify_hosts main "host list&!!" unset .cindex "HELO verifying" "mandatory" @@ -13429,8 +13858,8 @@ this check fails, Exim behaves as if the name lookup failed. .vindex "&$sender_host_name$&" After any kind of failure, the host name (in &$sender_host_name$&) remains unset, and &$host_lookup_failed$& is set to the string &"1"&. See also -&%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and &`verify`& &`=`& -&`reverse_host_lookup`& in ACLs. +&%dns_again_means_nonexist%&, &%helo_lookup_domains%&, and +&`verify = reverse_host_lookup`& in ACLs. .option host_lookup_order main "string list" &`bydns:byaddr`& @@ -13496,6 +13925,14 @@ chapter &<>&, which contains a discussion about local network interfaces and recognizing the local host. +.option ibase_servers main "string list" unset +.cindex "InterBase" "server list" +This option provides a list of InterBase servers and associated connection data, +to be used in conjunction with &(ibase)& lookups (see section &<>&). +The option is available only if Exim has been built with InterBase support. + + + .option ignore_bounce_errors_after main time 10w .cindex "bounce message" "discarding" .cindex "discarding bounce message" @@ -13544,6 +13981,46 @@ next attempt to deliver such a message, it gets removed. The incident is logged. +.option ldap_ca_cert_dir main string unset +.cindex "LDAP", "TLS CA certificate directory" +This option indicates which directory contains CA certificates for verifying +a TLS certificate presented by an LDAP server. +While Exim does not provide a default value, your SSL library may. +Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP +and constrained to be a directory. + + +.option ldap_ca_cert_file main string unset +.cindex "LDAP", "TLS CA certificate file" +This option indicates which file contains CA certificates for verifying +a TLS certificate presented by an LDAP server. +While Exim does not provide a default value, your SSL library may. +Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP +and constrained to be a file. + + +.option ldap_cert_file main string unset +.cindex "LDAP" "TLS client certificate file" +This option indicates which file contains an TLS client certificate which +Exim should present to the LDAP server during TLS negotiation. +Should be used together with &%ldap_cert_key%&. + + +.option ldap_cert_key main string unset +.cindex "LDAP" "TLS client key file" +This option indicates which file contains the secret/private key to use +to prove identity to the LDAP server during TLS negotiation. +Should be used together with &%ldap_cert_file%&, which contains the +identity to be proven. + + +.option ldap_cipher_suite main string unset +.cindex "LDAP" "TLS cipher suite" +This controls the TLS cipher-suite negotiation during TLS negotiation with +the LDAP server. See &<>& for more details of the format of +cipher-suite options with OpenSSL (as used by LDAP client libraries). + + .option ldap_default_servers main "string list" unset .cindex "LDAP" "default servers" This option provides a list of LDAP servers which are tried in turn when an @@ -13552,6 +14029,25 @@ details of LDAP queries. This option is available only when Exim has been built with LDAP support. +.option ldap_require_cert main string unset. +.cindex "LDAP" "policy for LDAP server TLS cert presentation" +This should be one of the values "hard", "demand", "allow", "try" or "never". +A value other than one of these is interpreted as "never". +See the entry "TLS_REQCERT" in your system man page for ldap.conf(5). +Although Exim does not set a default, the LDAP library probably defaults +to hard/demand. + + +.option ldap_start_tls main boolean false +.cindex "LDAP" "whether or not to negotiate TLS" +If set, Exim will attempt to negotiate TLS with the LDAP server when +connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's +"STARTTLS". This is distinct from using "ldaps", which is the LDAP form +of SSL-on-connect. +In the event of failure to negotiate TLS, the action taken is controlled +by &%ldap_require_cert%&. + + .option ldap_version main integer unset .cindex "LDAP" "protocol version, forcing" This option can be used to force Exim to set a specific protocol version for @@ -13746,6 +14242,15 @@ this option is set greater than zero, any attempt to call &[getpwnam()]& with an argument that is longer behaves as if &[getpwnam()]& failed. +.option message_body_newlines main bool false +.cindex "message body" "newlines in variables" +.cindex "newline" "in message body variables" +.vindex "&$message_body$&" +.vindex "&$message_body_end$&" +By default, newlines in the message body are replaced by spaces when setting +the &$message_body$& and &$message_body_end$& expansion variables. If this +option is set true, this no longer happens. + .option message_body_visible main integer 500 .cindex "body of message" "visible size" @@ -13816,6 +14321,18 @@ an oversized message is logged in both the main and the reject logs. See also the generic transport option &%message_size_limit%&, which limits the size of message that an individual transport can process. +If you use a virus-scanner and set this option to to a value larger than the +maximum size that your virus-scanner is configured to support, you may get +failures triggered by large mails. The right size to configure for the +virus-scanner depends upon what data is passed and the options in use but it's +probably safest to just set it to a little larger than this value. Eg, with a +default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M, +some problems may result. + +A value of 0 will disable size limit checking; Exim will still advertise the +SIZE extension in an EHLO response, but without a limit, so as to permit +SMTP clients to still indicate the message size along with the MAIL verb. + .option move_frozen_messages main boolean false .cindex "frozen messages" "moving" @@ -13840,7 +14357,7 @@ contains a full description of this facility. .option mysql_servers main "string list" unset .cindex "MySQL" "server list" This option provides a list of MySQL servers and associated connection data, to -be used in conjunction with &(mysql)& lookups (see section &<>&). The +be used in conjunction with &(mysql)& lookups (see section &<>&). The option is available only if Exim has been built with MySQL support. @@ -13868,10 +14385,100 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. +.option openssl_options main "string list" unset +.cindex "OpenSSL "compatibility options" +This option allows an administrator to adjust the SSL options applied +by OpenSSL to connections. It is given as a space-separated list of items, +each one to be +added or -subtracted from the current value. + +This option is only available if Exim is built against OpenSSL. The values +available for this option vary according to the age of your OpenSSL install. +The &"all"& value controls a subset of flags which are available, typically +the bug workaround options. The &'SSL_CTX_set_options'& man page will +list the values known on your system and Exim should support all the +&"bug workaround"& options and many of the &"modifying"& options. The Exim +names lose the leading &"SSL_OP_"& and are lower-cased. + +Note that adjusting the options can have severe impact upon the security of +SSL as used by Exim. It is possible to disable safety checks and shoot +yourself in the foot in various unpleasant ways. This option should not be +adjusted lightly. An unrecognised item will be detected at startup, by +invoking Exim with the &%-bV%& flag. + +.new +Historical note: prior to release 4.80, Exim defaulted this value to +"+dont_insert_empty_fragments", which may still be needed for compatibility +with some clients, but which lowers security by increasing exposure to +some now infamous attacks. +.wen + +An example: +.code +# Make both old MS and old Eudora happy: +openssl_options = -all +microsoft_big_sslv3_buffer \ + +dont_insert_empty_fragments +.endd + +Possible options may include: +.ilist +&`all`& +.next +&`allow_unsafe_legacy_renegotiation`& +.next +&`cipher_server_preference`& +.next +&`dont_insert_empty_fragments`& +.next +&`ephemeral_rsa`& +.next +&`legacy_server_connect`& +.next +&`microsoft_big_sslv3_buffer`& +.next +&`microsoft_sess_id_bug`& +.next +&`msie_sslv2_rsa_padding`& +.next +&`netscape_challenge_bug`& +.next +&`netscape_reuse_cipher_change_bug`& +.next +&`no_compression`& +.next +&`no_session_resumption_on_renegotiation`& +.next +&`no_sslv2`& +.next +&`no_sslv3`& +.next +&`no_ticket`& +.next +&`no_tlsv1`& +.next +&`no_tlsv1_1`& +.next +&`no_tlsv1_2`& +.next +&`single_dh_use`& +.next +&`single_ecdh_use`& +.next +&`ssleay_080_client_dh_bug`& +.next +&`sslref2_reuse_cert_type_bug`& +.next +&`tls_block_padding_bug`& +.next +&`tls_d5_bug`& +.next +&`tls_rollback_bug`& +.endlist + + .option oracle_servers main "string list" unset .cindex "Oracle" "server list" This option provides a list of Oracle servers and associated connection data, -to be used in conjunction with &(oracle)& lookups (see section &<>&). +to be used in conjunction with &(oracle)& lookups (see section &<>&). The option is available only if Exim has been built with Oracle support. @@ -13910,7 +14517,7 @@ interpreter. See chapter &<>& for details of its use. .cindex "PostgreSQL lookup type" "server list" This option provides a list of PostgreSQL servers and associated connection data, to be used in conjunction with &(pgsql)& lookups (see section -&<>&). The option is available only if Exim has been built with +&<>&). The option is available only if Exim has been built with PostgreSQL support. @@ -13933,8 +14540,8 @@ of the &%-oX%& option, unless a path is explicitly supplied by &%-oP%&. .option pipelining_advertise_hosts main "host list&!!" * .cindex "PIPELINING" "suppressing advertising" This option can be used to suppress the advertisement of the SMTP -PIPELINING extension to specific hosts. &new("See also the &*no_pipelining*& -control in section &<>&.") When PIPELINING is not advertised and +PIPELINING extension to specific hosts. See also the &*no_pipelining*& +control in section &<>&. When PIPELINING is not advertised and &%smtp_enforce_sync%& is true, an Exim server enforces strict synchronization for each SMTP command and response. When PIPELINING is advertised, Exim assumes that clients will use it; &"out of order"& commands that are &"expected"& do @@ -14086,11 +14693,29 @@ causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever .cindex "message" "queueing by load" If the system load average is higher than this value, incoming messages from all sources are queued, and no automatic deliveries are started. If this -happens during local or remote SMTP input, all subsequent messages on the same -connection are queued. Deliveries will subsequently be performed by queue -runner processes. This option has no effect on ancient operating systems on -which Exim cannot determine the load average. See also -&%deliver_queue_load_max%& and &%smtp_load_reserve%&. +happens during local or remote SMTP input, all subsequent messages received on +the same SMTP connection are queued by default, whatever happens to the load in +the meantime, but this can be changed by setting &%queue_only_load_latch%& +false. + +Deliveries will subsequently be performed by queue runner processes. This +option has no effect on ancient operating systems on which Exim cannot +determine the load average. See also &%deliver_queue_load_max%& and +&%smtp_load_reserve%&. + + +.option queue_only_load_latch main boolean true +.cindex "load average" "re-evaluating per message" +When this option is true (the default), once one message has been queued +because the load average is higher than the value set by &%queue_only_load%&, +all subsequent messages received on the same SMTP connection are also queued. +This is a deliberate choice; even though the load average may fall below the +threshold, it doesn't seem right to deliver later messages on the same +connection when not delivering earlier ones. However, there are special +circumstances such as very long-lived connections from scanning appliances +where this is not the best strategy. In such cases, &%queue_only_load_latch%& +should be set false. This causes the value of the load average to be +re-evaluated for each message. .option queue_only_override main boolean true @@ -14384,12 +15009,10 @@ value is set to zero, no limit is applied. However, it is required to be non-zero if either &%smtp_accept_max_per_host%& or &%smtp_accept_queue%& is set. See also &%smtp_accept_reserve%& and &%smtp_load_reserve%&. -.new A new SMTP connection is immediately rejected if the &%smtp_accept_max%& limit has been reached. If not, Exim first checks &%smtp_accept_max_per_host%&. If that limit has not been reached for the client host, &%smtp_accept_reserve%& and &%smtp_load_reserve%& are then checked before accepting the connection. -.wen .option smtp_accept_max_nonmail main integer 10 @@ -14436,7 +15059,6 @@ seen). .option smtp_accept_max_per_host main string&!! unset .cindex "limit" "SMTP connections from one host" .cindex "host" "limiting SMTP connections from" -.new This option restricts the number of simultaneous IP connections from a single host (strictly, from a single IP address) to the Exim daemon. The option is expanded, to enable different limits to be applied to different hosts by @@ -14445,7 +15067,6 @@ connection attempts from the same host are rejected with error code 421. This is entirely independent of &%smtp_accept_reserve%&. The option's default value of zero imposes no limit. If this option is set greater than zero, it is required that &%smtp_accept_max%& be non-zero. -.wen &*Warning*&: When setting this option you should not use any expansion constructions that take an appreciable amount of time. The expansion and test @@ -14460,13 +15081,17 @@ doing this processing, it cannot accept any other incoming connections. .cindex "SMTP" "incoming connection count" .cindex "queueing incoming messages" .cindex "message" "queueing by SMTP connection count" -If the number of simultaneous incoming SMTP calls handled via the listening -daemon exceeds this value, messages received by SMTP are just placed on the -queue; no delivery processes are started automatically. A value of zero implies -no limit, and clearly any non-zero value is useful only if it is less than the -&%smtp_accept_max%& value (unless that is zero). See also &%queue_only%&, -&%queue_only_load%&, &%queue_smtp_domains%&, and the various &%-od%&&'x'& -command line options. +If the number of simultaneous incoming SMTP connections being handled via the +listening daemon exceeds this value, messages received by SMTP are just placed +on the queue; no delivery processes are started automatically. The count is +fixed at the start of an SMTP connection. It cannot be updated in the +subprocess that receives messages, and so the queueing or not queueing applies +to all messages received in the same connection. + +A value of zero implies no limit, and clearly any non-zero value is useful only +if it is less than the &%smtp_accept_max%& value (unless that is zero). See +also &%queue_only%&, &%queue_only_load%&, &%queue_smtp_domains%&, and the +various &%-od%&&'x'& command line options. . Allow this long option name to split; give it unsplit as a fifth argument @@ -14496,14 +15121,14 @@ that are specified in &%smtp_reserve_hosts%&. The value set in &%smtp_accept_max%& includes this reserve pool. The specified hosts are not restricted to this number of connections; the option specifies a minimum number of connection slots for them, not a maximum. It is a guarantee that this group -of hosts can always get at least &%smtp_accept_reserve%& connections. -&new("However, the limit specified by &%smtp_accept_max_per_host%& is still -applied to each individual host.") +of hosts can always get at least &%smtp_accept_reserve%& connections. However, +the limit specified by &%smtp_accept_max_per_host%& is still applied to each +individual host. For example, if &%smtp_accept_max%& is set to 50 and &%smtp_accept_reserve%& is set to 5, once there are 45 active connections (from any hosts), new connections are accepted only from hosts listed in &%smtp_reserve_hosts%&, -&new("provided the other criteria for acceptance are met.") +provided the other criteria for acceptance are met. .option smtp_active_hostname main string&!! unset @@ -14950,11 +15575,13 @@ contains the pipe command. This specifies the transport driver that is to be used when a &%mail%& command is used in a system filter. + .option system_filter_user main string unset .cindex "uid (user id)" "system filter" -If this option is not set, the system filter is run in the main Exim delivery -process, as root. When the option is set, the system filter runs in a separate -process, as the given user. Unless the string consists entirely of digits, it +If this option is set to root, the system filter is run in the main Exim +delivery process, as root. Otherwise, the system filter runs in a separate +process, as the given user, defaulting to the Exim run-time user. +Unless the string consists entirely of digits, it is looked up in the password data. Failure to find the named user causes a configuration error. The gid is either taken from the password data, or specified by &%system_filter_group%&. When the uid is specified numerically, @@ -14962,8 +15589,7 @@ specified by &%system_filter_group%&. When the uid is specified numerically, If the system filter generates any pipe, file, or reply deliveries, the uid under which the filter is run is used when transporting them, unless a -transport option overrides. Normally you should set &%system_filter_user%& if -your system filter generates these kinds of delivery. +transport option overrides. .option tcp_nodelay main boolean true @@ -15037,6 +15663,12 @@ receiving incoming messages as a server. If you want to supply certificates for use when sending messages as a client, you must set the &%tls_certificate%& option in the relevant &(smtp)& transport. +.new +If the option contains &$tls_sni$& and Exim is built against OpenSSL, then +if the OpenSSL build supports TLS extensions and the TLS client sends the +Server Name Indication extension, then this option and others documented in +&<>& will be re-expanded. +.wen .option tls_crl main string&!! unset .cindex "TLS" "server certificate revocation list" @@ -15044,6 +15676,29 @@ option in the relevant &(smtp)& transport. This option specifies a certificate revocation list. The expanded value must be the name of a file that contains a CRL in PEM format. +.new +See &<>& for discussion of when this option might be re-expanded. +.wen + + +.new +.option tls_dh_max_bits main integer 2236 +.cindex "TLS" "D-H bit count" +The number of bits used for Diffie-Hellman key-exchange may be suggested by +the chosen TLS library. That value might prove to be too high for +interoperability. This option provides a maximum clamp on the value +suggested, trading off security for interoperability. + +The value must be at least 1024. + +The value 2236 was chosen because, at time of adding the option, it was the +hard-coded maximum value supported by the NSS cryptographic library, as used +by Thunderbird, while GnuTLS was suggesting 2432 bits as normal. + +If you prefer more security and are willing to break some clients, raise this +number. +.wen + .option tls_dhparam main string&!! unset .cindex "TLS" "D-H parameters for server" @@ -15052,6 +15707,11 @@ a file which contains the server's DH parameter values. This is used only for OpenSSL. When Exim is linked with GnuTLS, this option is ignored. See section &<>& for further details. +.new +If the DH bit-count from loading the file is greater than tls_dh_max_bits then +it will be ignored. +.wen + .option tls_on_connect_ports main "string list" unset This option specifies a list of incoming SSMTP (aka SMTPS) ports that should @@ -15069,6 +15729,10 @@ the expansion is forced to fail, or the result is an empty string, the private key is assumed to be in the same file as the server's certificates. See chapter &<>& for further details. +.new +See &<>& for discussion of when this option might be re-expanded. +.wen + .option tls_remember_esmtp main boolean false .cindex "TLS" "esmtp state; remembering" @@ -15108,19 +15772,34 @@ are using OpenSSL, you can set &%tls_verify_certificates%& to the name of a directory containing certificate files. This does not work with GnuTLS; the option must be set to the name of a single file if you are using GnuTLS. +These certificates should be for the certificate authorities trusted, rather +than the public cert of individual clients. With both OpenSSL and GnuTLS, if +the value is a file then the certificates are sent by Exim as a server to +connecting clients, defining the list of accepted certificate authorities. +Thus the values defined should be considered public data. To avoid this, +use OpenSSL with a directory. + +.new +See &<>& for discussion of when this option might be re-expanded. +.wen + .option tls_verify_hosts main "host list&!!" unset .cindex "TLS" "client certificate verification" .cindex "certificate" "verification of client" This option, along with &%tls_try_verify_hosts%&, controls the checking of -certificates from clients. -The expected certificates are defined by &%tls_verify_certificates%&, which -must be set. A configuration error occurs if either &%tls_verify_hosts%& or -&%tls_try_verify_hosts%& is set and &%tls_verify_certificates%& is not set. +certificates from clients. The expected certificates are defined by +&%tls_verify_certificates%&, which must be set. A configuration error occurs if +either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and +&%tls_verify_certificates%& is not set. Any client that matches &%tls_verify_hosts%& is constrained by -&%tls_verify_certificates%&. The client must present one of the listed -certificates. If it does not, the connection is aborted. +&%tls_verify_certificates%&. When the client initiates a TLS session, it must +present one of the listed certificates. If it does not, the connection is +aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require +the host to use TLS. It can still send SMTP commands through unencrypted +connections. Forcing a client to use TLS has to be done separately using an +ACL to reject inappropriate commands when the connection is not encrypted. A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client matches this option (but not &%tls_verify_hosts%&), Exim requests a @@ -15325,14 +16004,13 @@ file = ${extract{mailbox}{$address_data}} This makes the configuration file less messy, and also reduces the number of lookups (though Exim does cache lookups). -The &%address_data%& facility is also useful as a means of passing information -from one router to another, and from a router to a transport. In addition, if .vindex "&$sender_address_data$&" .vindex "&$address_data$&" -&$address_data$& is set by a router when verifying a recipient address -from an ACL, it remains available for use in the rest of the ACL statement. -After verifying a sender, the value is transferred to &$sender_address_data$&. - +The &%address_data%& facility is also useful as a means of passing information +from one router to another, and from a router to a transport. In addition, if +&$address_data$& is set by a router when verifying a recipient address from an +ACL, it remains available for use in the rest of the ACL statement. After +verifying a sender, the value is transferred to &$sender_address_data$&. @@ -15442,6 +16120,9 @@ router is skipped, and the address is offered to the next one. If the result is any other value, the router is run (as this is the last precondition to be evaluated, all the other preconditions must be true). +This option is unique in that multiple &%condition%& options may be present. +All &%condition%& options must succeed. + The &%condition%& option provides a means of applying custom conditions to the running of routers. Note that in the case of a simple conditional expansion, the default expansion values are exactly what is wanted. For example: @@ -15452,12 +16133,19 @@ Because of the default behaviour of the string expansion, this is equivalent to .code condition = ${if >{$message_age}{600}{true}{}} .endd + +A multiple condition example, which succeeds: +.code +condition = ${if >{$message_age}{600}} +condition = ${if !eq{${lc:$local_part}}{postmaster}} +condition = foobar +.endd + If the expansion fails (other than forced failure) delivery is deferred. Some of the other precondition options are common special cases that could in fact be specified using &%condition%&. - .option debug_print routers string&!! unset .cindex "testing" "variables in drivers" If this option is set and debugging is enabled (see the &%-d%& command line @@ -15634,7 +16322,6 @@ failures are treated as configuration errors. &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)& router that has the &%one_time%& option set. -.new .cindex "duplicate addresses" .oindex "&%unseen%&" &*Warning 2*&: If the &%unseen%& option is set on the router, all header @@ -15645,7 +16332,6 @@ modifications. Exim does not do duplicate deliveries (except, in certain circumstances, to pipes -- see section &<>&), but it is undefined which of the duplicates is discarded, so this ambiguous situation should be avoided. The &%repeat_use%& option of the &%redirect%& router may be of help. -.wen @@ -15669,12 +16355,10 @@ errors. &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)& router that has the &%one_time%& option set. -.new &*Warning 2*&: If the &%unseen%& option is set on the router, all header removal requests are deleted when the address is passed on to subsequent routers, and this can lead to problems with duplicates -- see the similar warning for &%headers_add%& above. -.wen .option ignore_target_hosts routers "host list&!!" unset @@ -15776,6 +16460,13 @@ real_localuser: check_local_user transport = local_delivery .endd +For security, it would probably be a good idea to restrict the use of this +router to locally-generated messages, using a condition such as this: +.code + condition = ${if match {$sender_host_address}\ + {\N^(|127\.0\.0\.1)$\N}} +.endd + If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router, both conditions must be met if not optional. Care must be taken if wildcards are used in both a prefix and a suffix on the same router. Different @@ -15885,12 +16576,15 @@ applies to all of them. .option pass_router routers string unset .cindex "router" "go to after &""pass""&" -When a router returns &"pass"&, the address is normally handed on to the next +Routers that recognize the generic &%self%& option (&(dnslookup)&, +&(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing +routing to continue, and overriding a false setting of &%more%&. When one of +these routers returns &"pass"&, the address is normally handed on to the next router in sequence. This can be changed by setting &%pass_router%& to the name of another router. However (unlike &%redirect_router%&) the named router must be below the current router, to avoid loops. Note that this option applies only to the special case of &"pass"&. It does not apply when a router returns -&"decline"&. +&"decline"& because it cannot handle an address. @@ -16241,7 +16935,6 @@ overriding a false setting of &%more%&. There is little point in setting the value of &%unseen%& contains expansion items (and therefore, presumably, is sometimes true and sometimes false). -.new .cindex "copy of message (&%unseen%& option)" Setting the &%unseen%& option has a similar effect to the &%unseen%& command qualifier in filter files. It can be used to cause copies of messages to be @@ -16265,7 +16958,6 @@ so this ambiguous situation should be avoided. The &%repeat_use%& option of the Unlike the handling of header modifications, any data that was set by the &%address_data%& option in the current or previous routers &'is'& passed on to subsequent routers. -.wen .option user routers string&!! "see below" @@ -16411,6 +17103,40 @@ look for A or AAAA records, unless the domain matches &%mx_domains%&, in which case routing fails. +.new +.section "Declining addresses by dnslookup" "SECTdnslookupdecline" +.cindex "&(dnslookup)& router" "declines" +There are a few cases where a &(dnslookup)& router will decline to accept +an address; if such a router is expected to handle "all remaining non-local +domains", then it is important to set &%no_more%&. + +Reasons for a &(dnslookup)& router to decline currently include: +.ilist +The domain does not exist in DNS +.next +The domain exists but the MX record's host part is just "."; this is a common +convention (borrowed from SRV) used to indicate that there is no such service +for this domain and to not fall back to trying A/AAAA records. +.next +Ditto, but for SRV records, when &%check_srv%& is set on this router. +.next +MX record points to a non-existent host. +.next +MX record points to an IP address and the main section option +&%allow_mx_to_ip%& is not set. +.next +MX records exist and point to valid hosts, but all hosts resolve only to +addresses blocked by the &%ignore_target_hosts%& generic option on this router. +.next +The domain is not syntactically valid (see also &%allow_utf8_domains%& and +&%dns_check_names_pattern%& for handling one variant of this) +.next +&%check_secondary_mx%& is set on this router but the local host can +not be found in the MX records (see below) +.endlist +.wen + + .section "Private options for dnslookup" "SECID118" @@ -16790,7 +17516,6 @@ below, following the list of private options. .cindex "options" "&(manualroute)& router" The private options for the &(manualroute)& router are as follows: -.new .option host_all_ignored manualroute string defer See &%host_find_failed%&. @@ -16822,7 +17547,6 @@ as &%host_find_failed%&, except that it cannot be set to &"ignore"&. The &%host_find_failed%& option applies only to a definite &"does not exist"& state; if a host lookup gets a temporary error, delivery is deferred unless the generic &%pass_on_timeout%& option is set. -.wen .option hosts_randomize manualroute boolean false @@ -17421,11 +18145,9 @@ It can be routed to be delivered to a specified pipe command. .next It can cause an automatic reply to be generated. .next -.new It can be forced to fail, optionally with a custom error message. .next It can be temporarily deferred, optionally with a custom message. -.wen .next It can be discarded. .endlist @@ -17712,10 +18434,10 @@ redirection items of the form :defer: :fail: .endd -respectively. When a redirection list contains such an item, it applies to the -entire redirection; any other items in the list are ignored (&':blackhole:'& is -different). Any text following &':fail:'& or &':defer:'& is placed in the error -text associated with the failure. For example, an alias file might contain: +respectively. When a redirection list contains such an item, it applies +to the entire redirection; any other items in the list are ignored. Any +text following &':fail:'& or &':defer:'& is placed in the error text +associated with the failure. For example, an alias file might contain: .code X.Employee: :fail: Gone away, no forwarding address .endd @@ -18317,6 +19039,13 @@ real_localuser: local_part_prefix = real- transport = local_delivery .endd +For security, it would probably be a good idea to restrict the use of this +router to locally-generated messages, using a condition such as this: +.code + condition = ${if match {$sender_host_address}\ + {\N^(|127\.0\.0\.1)$\N}} +.endd + .option syntax_errors_text redirect string&!! unset See &%skip_syntax_errors%& above. @@ -18853,11 +19582,9 @@ filter itself, and the original process that reads the result and delivers it are all run in parallel, like a shell pipeline. The filter can perform any transformations it likes, but of course should take -care not to break RFC 2822 syntax. A demonstration Perl script is provided in -&_util/transport-filter.pl_&; this makes a few arbitrary modifications just to -show the possibilities. Exim does not check the result, except to test for a -final newline when SMTP is in use. All messages transmitted over SMTP must end -with a newline, so Exim supplies one if it is missing. +care not to break RFC 2822 syntax. Exim does not check the result, except to +test for a final newline when SMTP is in use. All messages transmitted over +SMTP must end with a newline, so Exim supplies one if it is missing. .cindex "content scanning" "per user" A transport filter can be used to provide content-scanning on a per-user basis @@ -19528,13 +20255,16 @@ This option applies only to deliveries in maildir format, and is described in section &<>& below. -.option maildir_use_size_file appendfile boolean false +.new +.option maildir_use_size_file appendfile&!! boolean false .cindex "maildir format" "&_maildirsize_& file" -Setting this option true enables support for &_maildirsize_& files. Exim +The result of string expansion for this option must be a valid boolean value. +If it is true, it enables support for &_maildirsize_& files. Exim creates a &_maildirsize_& file in a maildir if one does not exist, taking the quota from the &%quota%& option of the transport. If &%quota%& is unset, the value is zero. See &%maildir_quota_directory_regex%& above and section &<>& below for further details. +.wen .option maildirfolder_create_regex appendfile string unset .cindex "maildir format" "&_maildirfolder_& file" @@ -19610,7 +20340,8 @@ in which case it is: message_prefix = "From ${if def:return_path{$return_path}\ {MAILER-DAEMON}} $tod_bsdinbox\n" .endd - +&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of +&`\n`& to &`\r\n`& in &%message_prefix%&. .option message_suffix appendfile string&!! "see below" The string specified here is expanded and output at the end of every message. @@ -19620,6 +20351,8 @@ setting .code message_suffix = .endd +&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of +&`\n`& to &`\r\n`& in &%message_suffix%&. .option mode appendfile "octal integer" 0600 If the output file is created, it is given this mode. If it already exists and @@ -19732,6 +20465,7 @@ The regular expression should not assume that the length is at the end of the file name (even though &%maildir_tag%& puts it there) because maildir MUAs sometimes add other information onto the ends of message file names. +Section &<>& contains further information. .option quota_warn_message appendfile string&!! "see below" @@ -19801,11 +20535,12 @@ This option causes lines to be terminated with the two-character CRLF sequence of batched SMTP, the byte sequence written to the file is then an exact image of what would be sent down a real SMTP connection. -The contents of the &%message_prefix%& and &%message_suffix%& options are -written verbatim, so must contain their own carriage return characters if these -are needed. In cases where these options have non-empty defaults, the values -end with a single linefeed, so they must be changed to end with &`\r\n`& if -&%use_crlf%& is set. +&*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options +(which are used to supply the traditional &"From&~"& and blank line separators +in Berkeley-style mailboxes) are written verbatim, so must contain their own +carriage return characters if these are needed. In cases where these options +have non-empty defaults, the values end with a single linefeed, so they must be +changed to end with &`\r\n`& if &%use_crlf%& is set. .option use_fcntl_lock appendfile boolean "see below" @@ -20145,6 +20880,7 @@ tag is added to its name. However, if adding the tag takes the length of the name to the point where the test &[stat()]& call fails with ENAMETOOLONG, the tag is dropped and the maildir file is created with no tag. + .vindex "&$message_size$&" Tags can be used to encode the size of files in their names; see &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%& @@ -20154,8 +20890,19 @@ forced to fail, the tag is ignored, but a non-forced failure causes delivery to be deferred. The expanded tag may contain any printing characters except &"/"&. Non-printing characters in the string are ignored; if the resulting string is empty, it is ignored. If it starts with an alphanumeric character, a leading -colon is inserted. +colon is inserted; this default has not proven to be the path that popular +maildir implementations have chosen (but changing it in Exim would break +backwards compatibility). + +For one common implementation, you might set: +.code +maildir_tag = ,S=${message_size} +.endd +but you should check the documentation of the other software to be sure. +It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%& +as this allows Exim to extract the size from your tag, instead of having to +&[stat()]& each message file. .section "Using a maildirsize file" "SECID136" @@ -20496,8 +21243,9 @@ delivers the message to it using the LMTP protocol. .option timeout lmtp time 5m The transport is aborted if the created process or Unix domain socket does not -respond to LMTP commands or message input within this timeout. Here is an -example of a typical LMTP transport: +respond to LMTP commands or message input within this timeout. Delivery +is deferred, and will be tried again later. Here is an example of a typical +LMTP transport: .code lmtp: driver = lmtp @@ -20580,9 +21328,14 @@ later"&. In this case, delivery is deferred. Details of a permanent failure are logged, but are not included in the bounce message, which merely contains &"local delivery failed"&. +If the command exits on a signal and the &%freeze_signal%& option is set then +the message will be frozen in the queue. If that option is not set, a bounce +will be sent as normal. + If the return code is greater than 128 and the command being run is a shell script, it normally means that the script was terminated by a signal whose -value is the return code minus 128. +value is the return code minus 128. The &%freeze_signal%& option does not +apply in this case. If Exim is unable to run the command (that is, if &[execve()]& fails), the return code is set to 127. This is the value that a shell returns if it is @@ -20791,6 +21544,14 @@ is set, failure to exec is treated specially, and causes the message to be frozen, whatever the setting of &%ignore_status%&. +.option freeze_signal pipe boolean false +.cindex "signal exit" +.cindex "&(pipe)& transport", "signal exit" +Normally if the process run by a command in a pipe transport exits on a signal, +a bounce message is sent. If &%freeze_signal%& is set, the message will be +frozen in Exim's queue instead. + + .option ignore_status pipe boolean false If this option is true, the status returned by the subprocess that is set up to run the command is ignored, and Exim behaves as if zero had been returned. @@ -20852,6 +21613,9 @@ setting .code message_prefix = .endd +&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of +&`\n`& to &`\r\n`& in &%message_prefix%&. + .option message_suffix pipe string&!! "see below" The string specified here is expanded and output at the end of every message. @@ -20860,6 +21624,9 @@ The suffix can be suppressed by setting .code message_suffix = .endd +&*Note:*& If you set &%use_crlf%& true, you must change any occurrences of +&`\n`& to &`\r\n`& in &%message_suffix%&. + .option path pipe string "see below" This option specifies the string that is set up in the PATH environment @@ -20872,6 +21639,17 @@ sought in the PATH directories, in the usual way. &*Warning*&: This does not apply to a command specified as a transport filter. +.option permit_coredump pipe boolean false +Normally Exim inhibits core-dumps during delivery. If you have a need to get +a core-dump of a pipe command, enable this command. This enables core-dumps +during delivery and affects both the Exim binary and the pipe command run. +It is recommended that this option remain off unless and until you have a need +for it and that this only be enabled when needed, as the risk of excessive +resource consumption can be quite high. Note also that Exim is typically +installed as a setuid binary and most operating systems will inhibit coredumps +of these by default, so further OS-specific action may be required. + + .option pipe_as_creator pipe boolean false .cindex "uid (user id)" "local delivery" If the generic &%user%& option is not set and this option is true, the delivery @@ -20970,9 +21748,9 @@ of what would be sent down a real SMTP connection. The contents of the &%message_prefix%& and &%message_suffix%& options are written verbatim, so must contain their own carriage return characters if these -are needed. Since the default values for both &%message_prefix%& and -&%message_suffix%& end with a single linefeed, their values must be changed to -end with &`\r\n`& if &%use_crlf%& is set. +are needed. When &%use_bsmtp%& is not set, the default values for both +&%message_prefix%& and &%message_suffix%& end with a single linefeed, so their +values must be changed to end with &`\r\n`& if &%use_crlf%& is set. .option use_shell pipe boolean false @@ -21012,6 +21790,7 @@ procmail_pipe: envelope_to_add check_string = "From " escape_string = ">From " + umask = 077 user = $local_part group = mail @@ -21107,7 +21886,7 @@ no further messages are sent over that connection. -.section "Use of the $host variable" "SECID145" +.section "Use of the $host and $host_address variables" "SECID145" .vindex "&$host$&" .vindex "&$host_address$&" At the start of a run of the &(smtp)& transport, the values of &$host$& and @@ -21119,6 +21898,21 @@ that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&, &%serialize_hosts%&, and the various TLS options are expanded. +.section "Use of $tls_cipher and $tls_peerdn" "usecippeer" +.vindex &$tls_bits$& +.vindex &$tls_cipher$& +.vindex &$tls_peerdn$& +.vindex &$tls_sni$& +At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&, +&$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$& +are the values that were set when the message was received. +These are the values that are used for options that are expanded before any +SMTP connections are made. Just before each connection is made, these four +variables are emptied. If TLS is subsequently started, they are set to the +appropriate values for the outgoing connection, and these are the values that +are in force when any authenticators are run and when the +&%authenticated_sender%& option is expanded. + .section "Private options for smtp" "SECID146" .cindex "options" "&(smtp)& transport" @@ -21154,6 +21948,11 @@ forced to fail, the option is ignored. Other expansion failures cause delivery to be deferred. If the result of expansion is an empty string, that is also ignored. +The expansion happens after the outgoing connection has been made and TLS +started, if required. This means that the &$host$&, &$host_address$&, +&$tls_cipher$&, and &$tls_peerdn$& variables are set according to the +particular connection. + If the SMTP session is not authenticated, the expansion of &%authenticated_sender%& still happens (and can cause the delivery to be deferred if it fails), but no AUTH= item is added to MAIL commands @@ -21294,21 +22093,11 @@ being used, names are looked up using &[gethostbyname()]& instead of using the DNS. Of course, that function may in fact use the DNS, but it may also consult other sources of information such as &_/etc/hosts_&. -.new -.option gnutls_require_kx main string unset -This option controls the key exchange mechanisms when GnuTLS is used in an Exim -client. For details, see section &<>&. - -.option gnutls_require_mac main string unset -This option controls the MAC algorithms when GnuTLS is used in an Exim -client. For details, see section &<>&. - -.option gnutls_require_protocols main string unset -This option controls the protocols when GnuTLS is used in an Exim -client. For details, see section &<>&. -.wen +.option gnutls_compat_mode smtp boolean unset +This option controls whether GnuTLS is used in compatibility mode in an Exim +server. This reduces security slightly, but improves interworking with older +implementations of TLS. -.new .option helo_data smtp string&!! "see below" .cindex "HELO" "argument, setting" .cindex "EHLO" "argument, setting" @@ -21323,17 +22112,16 @@ $primary_hostname During the expansion, the variables &$host$& and &$host_address$& are set to the identity of the remote host, and the variables &$sending_ip_address$& and &$sending_port$& are set to the local IP address and port number that are being -used. These variables can be therefore used to generate different values for -different servers or different local IP addresses. For example, if you want the -string that is used for &%helo_data%& to be obtained by a DNS lookup of the -outgoing interface address, you could use this: +used. These variables can be used to generate different values for different +servers or different local IP addresses. For example, if you want the string +that is used for &%helo_data%& to be obtained by a DNS lookup of the outgoing +interface address, you could use this: .code helo_data = ${lookup dnsdb{ptr=$sending_ip_address}{$value}\ {$primary_hostname}} .endd The use of &%helo_data%& applies both to sending messages and when doing callouts. -.wen .option hosts smtp "string list&!!" unset Hosts are associated with an address by a router such as &(dnslookup)&, which @@ -21380,12 +22168,10 @@ start of the SMTP session. This means that it cannot use any of the ESMTP facilities such as AUTH, PIPELINING, SIZE, and STARTTLS. -.new .option hosts_avoid_pipelining smtp "host list&!!" unset .cindex "PIPELINING" "avoiding the use of" Exim will not use the SMTP PIPELINING extension when delivering to any host that matches this list, even if the server host advertises PIPELINING support. -.wen .option hosts_avoid_tls smtp "host list&!!" unset @@ -21482,10 +22268,11 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter .vindex "&$host$&" .vindex "&$host_address$&" This option specifies which interface to bind to when making an outgoing SMTP -call. &*Note:*& Do not confuse this with the interface address that was used -when a message was received, which is in &$received_ip_address$&, formerly -known as &$interface_address$&. The name was changed to minimize confusion with -the outgoing interface address. There is no variable that contains an outgoing +call. The value is an IP address, not an interface name such as +&`eth0`&. Do not confuse this with the interface address that was used when a +message was received, which is in &$received_ip_address$&, formerly known as +&$interface_address$&. The name was changed to minimize confusion with the +outgoing interface address. There is no variable that contains an outgoing interface address because, unless it is set by this option, its value is unknown. @@ -21560,12 +22347,22 @@ is deferred. .option protocol smtp string smtp .cindex "LMTP" "over TCP/IP" +.cindex "ssmtp protocol" "outbound" +.cindex "TLS" "SSL-on-connect outbound" +.vindex "&$port$&" If this option is set to &"lmtp"& instead of &"smtp"&, the default value for the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local deliveries into closed message stores. Exim also has support for running LMTP over a pipe to a local process &-- see chapter &<>&. +.new +If this option is set to &"smtps"&, the default vaule for the &%port%& option +changes to &"smtps"&, and the transport initiates TLS immediately after +connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. +The Internet standards bodies strongly discourage use of this mode. +.wen + .option retry_include_ip_address smtp boolean true Exim normally includes both the host name and the IP address in the key it @@ -21677,6 +22474,22 @@ ciphers is a preference order. +.new +.option tls_sni smtp string&!! unset +.cindex "TLS" "Server Name Indication" +.vindex "&$tls_sni$&" +If this option is set then it sets the $tls_sni variable and causes any +TLS session to pass this value as the Server Name Indication extension to +the remote side, which can be used by the remote side to select an appropriate +certificate and private key for the session. + +See &<>& for more information. + +OpenSSL only, also requiring a build of OpenSSL that supports TLS extensions. +.wen + + + .option tls_tempfail_tryclear smtp boolean true .cindex "4&'xx'& responses" "to STARTTLS" When the server host is not in &%hosts_require_tls%&, and there is a problem in @@ -22108,6 +22921,10 @@ rewriting rule is skipped unless the relevant addresses are being processed. &`s`& rewrite the &'Sender:'& header &`t`& rewrite the &'To:'& header .endd +"All headers" means all of the headers listed above that can be selected +individually, plus their &'Resent-'& versions. It does not include +other headers such as &'Subject:'& etc. + You should be particularly careful about rewriting &'Sender:'& headers, and restrict this to special known cases in your own domains. @@ -22241,11 +23058,14 @@ can be done on the rewritten addresses. .chapter "Retry configuration" "CHAPretry" .scindex IIDretconf1 "retry" "configuration, description of" .scindex IIDregconf2 "configuration file" "retry section" -The &"retry"& section of the run time configuration file contains a list of +The &"retry"& section of the runtime configuration file contains a list of retry rules that control how often Exim tries to deliver messages that cannot -be delivered at the first attempt. If there are no retry rules, temporary -errors are treated as permanent. The &%-brt%& command line option can be used -to test which retry rule will be used for a given address, domain and error. +be delivered at the first attempt. If there are no retry rules (the section is +empty or not present), there are no retries. In this situation, temporary +errors are treated as permanent. The default configuration contains a single, +general-purpose retry rule (see section &<>&). The &%-brt%& command +line option can be used to test which retry rule will be used for a given +address, domain and error. The most common cause of retries is temporary failure to deliver to a remote host because the host is down, or inaccessible because of a network problem. @@ -22827,7 +23647,7 @@ includes the list of supported mechanisms. For example: &`$ `&&*&`telnet server.example 25`&*& &`Trying 192.168.34.25...`& &`Connected to server.example.`& -&`Escape character is '^]'.`& +&`Escape character is '^]'.`& &`220 server.example ESMTP Exim 4.20 ...`& &*&`ehlo client.example`&*& &`250-server.example Hello client.example [10.8.4.5]`& @@ -22845,15 +23665,29 @@ included by setting .code AUTH_CRAM_MD5=yes AUTH_CYRUS_SASL=yes +.new +AUTH_DOVECOT=yes +AUTH_GSASL=yes +AUTH_HEIMDAL_GSSAPI=yes +.wen AUTH_PLAINTEXT=yes AUTH_SPA=yes .endd in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5 authentication mechanism (RFC 2195), and the second provides an interface to -the Cyrus SASL authentication library. The third can be configured to support +the Cyrus SASL authentication library. +.new +The third is an interface to Dovecot's authentication system, delegating the +work via a socket interface. +The fourth provides an interface to the GNU SASL authentication library, which +provides mechanisms but typically not data sources. +The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but +supporting setting a server keytab. +The sixth can be configured to support the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is -not formally documented, but used by several MUAs. The fourth authenticator +not formally documented, but used by several MUAs. The seventh authenticator supports Microsoft's &'Secure Password Authentication'& mechanism. +.wen The authenticators are configured using the same syntax as other drivers (see section &<>&). If no authenticators are required, no @@ -22885,12 +23719,48 @@ The remainder of this chapter covers the generic options for the authenticators, followed by general discussion of the way authentication works in Exim. +.new +&*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and +per-mechanism basis. Please read carefully to determine which variables hold +account labels such as usercodes and which hold passwords or other +authenticating data. + +Note that some mechanisms support two different identifiers for accounts: the +&'authentication id'& and the &'authorization id'&. The contractions &'authn'& +and &'authz'& are commonly encountered. The American spelling is standard here. +Conceptually, authentication data such as passwords are tied to the identifier +used to authenticate; servers may have rules to permit one user to act as a +second user, so that after login the session is treated as though that second +user had logged in. That second user is the &'authorization id'&. A robust +configuration might confirm that the &'authz'& field is empty or matches the +&'authn'& field. Often this is just ignored. The &'authn'& can be considered +as verified data, the &'authz'& as an unverified request which the server might +choose to honour. + +A &'realm'& is a text string, typically a domain name, presented by a server +to a client to help it select an account and credentials to use. In some +mechanisms, the client and server provably agree on the realm, but clients +typically can not treat the realm as secure data to be blindly trusted. +.wen + .section "Generic options for authenticators" "SECID168" .cindex "authentication" "generic options" .cindex "options" "generic; for authenticators" +.option client_condition authenticators string&!! unset +When Exim is authenticating as a client, it skips any authenticator whose +&%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be +used, for example, to skip plain text authenticators when the connection is not +encrypted by a setting such as: +.code +client_condition = ${if !eq{$tls_cipher}{}} +.endd +(Older documentation incorrectly states that &$tls_cipher$& contains the cipher +used for incoming messages. In fact, during SMTP delivery, it contains the +cipher used for the delivery.) + .option driver authenticators string unset This option must always be set. It specifies which of the available @@ -22919,6 +23789,11 @@ This option must be set for a &%plaintext%& server authenticator, where it is used directly to control authentication. See section &<>& for details. +.new +For the &(gsasl)& authenticator, this option is required for various +mechanisms; see chapter &<>& for details. +.wen + For the other authenticators, &%server_condition%& can be used as an additional authentication or authorization mechanism that is applied after the other authenticator conditions succeed. If it is set, it is expanded when the @@ -23146,12 +24021,10 @@ announces support for authentication, and the host matches an entry in either of these options, Exim (as a client) tries to authenticate as follows: .ilist -.new For each authenticator that is configured as a client, in the order in which they are defined in the configuration, it searches the authentication mechanisms announced by the server for one whose name matches the public name of the authenticator. -.wen .next .vindex "&$host$&" .vindex "&$host_address$&" @@ -23379,18 +24252,21 @@ login: driver = plaintext public_name = LOGIN server_prompts = Username:: : Password:: - server_condition = ${if ldapauth \ - {user="cn=${quote_ldap_dn:$auth1},ou=people,o=example.org" \ - pass=${quote:$auth2} \ - ldap://ldap.example.org/}} + server_condition = ${if and{{ \ + !eq{}{$auth1} }{ \ + ldapauth{\ + user="uid=${quote_ldap_dn:$auth1},ou=people,o=example.org" \ + pass=${quote:$auth2} \ + ldap://ldap.example.org/} }} } server_set_id = uid=$auth1,ou=people,o=example.org .endd -Note the use of the &%quote_ldap_dn%& operator to correctly quote the DN for -authentication. However, the basic &%quote%& operator, rather than any of the -LDAP quoting operators, is the correct one to use for the password, because -quoting is needed only to make the password conform to the Exim syntax. At the -LDAP level, the password is an uninterpreted string. - +We have to check that the username is not empty before using it, because LDAP +does not permit empty DN components. We must also use the &%quote_ldap_dn%& +operator to correctly quote the DN for authentication. However, the basic +&%quote%& operator, rather than any of the LDAP quoting operators, is the +correct one to use for the password, because quoting is needed only to make +the password conform to the Exim syntax. At the LDAP level, the password is an +uninterpreted string. .section "Support for different kinds of authentication" "SECID174" @@ -23523,6 +24399,20 @@ lookup_cram: Note that this expansion explicitly forces failure if the lookup fails because &$auth1$& contains an unknown user name. +.new +As another example, if you wish to re-use a Cyrus SASL sasldb2 file without +using the relevant libraries, you need to know the realm to specify in the +lookup and then ask for the &"userPassword"& attribute for that user in that +realm, with: +.code +cyrusless_crammd5: + driver = cram_md5 + public_name = CRAM-MD5 + server_secret = ${lookup{$auth1:mail.example.org:userPassword}\ + dbmjz{/etc/sasldb2}} + server_set_id = $auth1 +.endd +.wen .section "Using cram_md5 as a client" "SECID177" .cindex "options" "&(cram_md5)& authenticator (client)" @@ -23596,10 +24486,17 @@ be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for Kerberos, note that because of limitations in the GSSAPI interface, changing the server keytab might need to be communicated down to the Kerberos layer independently. The mechanism for doing so is dependent upon the Kerberos -implementation. For example, for Heimdal, the environment variable KRB5_KTNAME +implementation. +.new +For example, for older releases of Heimdal, the environment variable KRB5_KTNAME may be set to point to an alternative keytab file. Exim will pass this variable through from its own inherited environment when started as root or the Exim user. The keytab file needs to be readable by the Exim user. +With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the +environment variable. In practice, for those releases, the Cyrus authenticator +is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider +the &(heimdal_gssapi)& authenticator, described in chapter &<>& +.wen .section "Using cyrus_sasl as a server" "SECID178" @@ -23630,8 +24527,10 @@ sasl: server_set_id = $auth1 .endd -.option server_realm cyrus_sasl string unset +.new +.option server_realm cyrus_sasl string&!! unset This specifies the SASL realm that the server claims to be in. +.wen .option server_service cyrus_sasl string &`smtp`& @@ -23651,7 +24550,7 @@ sasl_cram_md5: sasl_plain: driver = cyrus_sasl public_name = PLAIN - server_set_id = $auth1 + server_set_id = $auth2 .endd Cyrus SASL does implement the LOGIN authentication method, even though it is not a standard method. It is disabled by default in the source distribution, @@ -23684,7 +24583,7 @@ dovecot_plain: driver = dovecot public_name = PLAIN server_socket = /var/run/dovecot/auth-client - server_set_id = $auth1 + server_set_id = $auth2 dovecot_ntlm: driver = dovecot @@ -23696,12 +24595,223 @@ If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to &$received_ip_address$& (that is, the connection is local), the &"secured"& option is passed in the Dovecot authentication command. If, for a TLS connection, a client certificate has been verified, the &"valid-client-cert"& -option is passed. &new("When authentication succeeds, the identity of the user -who authenticated is placed in &$auth1$&.") +option is passed. When authentication succeeds, the identity of the user +who authenticated is placed in &$auth1$&. .ecindex IIDdcotauth1 .ecindex IIDdcotauth2 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// +.new +.chapter "The gsasl authenticator" "CHAPgsasl" +.scindex IIDgsaslauth1 "&(gsasl)& authenticator" +.scindex IIDgsaslauth2 "authenticators" "&(gsasl)&" +.cindex "authentication" "GNU SASL" +.cindex "authentication" "SASL" +.cindex "authentication" "EXTERNAL" +.cindex "authentication" "ANONYMOUS" +.cindex "authentication" "PLAIN" +.cindex "authentication" "LOGIN" +.cindex "authentication" "DIGEST-MD5" +.cindex "authentication" "CRAM-MD5" +.cindex "authentication" "SCRAM-SHA-1" +The &(gsasl)& authenticator provides server integration for the GNU SASL +library and the mechanisms it provides. This is new as of the 4.80 release +and there are a few areas where the library does not let Exim smoothly +scale to handle future authentication mechanisms, so no guarantee can be +made that any particular new authentication mechanism will be supported +without code changes in Exim. + + +.option server_channelbinding gsasl boolean false +Some authentication mechanisms are able to use external context at both ends +of the session to bind the authentication to that context, and fail the +authentication process if that context differs. Specifically, some TLS +ciphersuites can provide identifying information about the cryptographic +context. + +This means that certificate identity and verification becomes a non-issue, +as a man-in-the-middle attack will cause the correct client and server to +see different identifiers and authentication will fail. + +This is currently only supported when using the GnuTLS library. This is +only usable by mechanisms which support "channel binding"; at time of +writing, that's the SCRAM family. + +This defaults off to ensure smooth upgrade across Exim releases, in case +this option causes some clients to start failing. Some future release +of Exim may switch the default to be true. + + +.option server_hostname gsasl string&!! "see below" +This option selects the hostname that is used when communicating with the +library. The default value is &`$primary_hostname`&. +Some mechanisms will use this data. + + +.option server_mech gsasl string "see below" +This option selects the authentication mechanism this driver should use. The +default is the value of the generic &%public_name%& option. This option allows +you to use a different underlying mechanism from the advertised name. For +example: +.code +sasl: + driver = gsasl + public_name = X-ANYTHING + server_mech = CRAM-MD5 + server_set_id = $auth1 +.endd + + +.option server_password gsasl string&!! unset +Various mechanisms need access to the cleartext password on the server, so +that proof-of-possession can be demonstrated on the wire, without sending +the password itself. + +The data available for lookup varies per mechanism. +In all cases, &$auth1$& is set to the &'authentication id'&. +The &$auth2$& variable will always be the &'authorization id'& (&'authz'&) +if available, else the empty string. +The &$auth3$& variable will always be the &'realm'& if available, +else the empty string. + +A forced failure will cause authentication to defer. + +If using this option, it may make sense to set the &%server_condition%& +option to be simply "true". + + +.option server_realm gsasl string&!! unset +This specifies the SASL realm that the server claims to be in. +Some mechanisms will use this data. + + +.option server_scram_iter gsasl string&!! unset +This option provides data for the SCRAM family of mechanisms. +&$auth1$& is not available at evaluation time. +(This may change, as we receive feedback on use) + + +.option server_scram_salt gsasl string&!! unset +This option provides data for the SCRAM family of mechanisms. +&$auth1$& is not available at evaluation time. +(This may change, as we receive feedback on use) + + +.option server_service gsasl string &`smtp`& +This is the SASL service that the server claims to implement. +Some mechanisms will use this data. + + +.section "&(gsasl)& auth variables" "SECTgsaslauthvar" +.vindex "&$auth1$&, &$auth2$&, etc" +These may be set when evaluating specific options, as detailed above. +They will also be set when evaluating &%server_condition%&. + +Unless otherwise stated below, the &(gsasl)& integration will use the following +meanings for these variables: + +.ilist +.vindex "&$auth1$&" +&$auth1$&: the &'authentication id'& +.next +.vindex "&$auth2$&" +&$auth2$&: the &'authorization id'& +.next +.vindex "&$auth3$&" +&$auth3$&: the &'realm'& +.endlist + +On a per-mechanism basis: + +.ilist +.cindex "authentication" "EXTERNAL" +EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&; +the &%server_condition%& option must be present. +.next +.cindex "authentication" "ANONYMOUS" +ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&; +the &%server_condition%& option must be present. +.next +.cindex "authentication" "GSSAPI" +GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&; +&$auth2$& will be set to the &'authorization id'&, +the &%server_condition%& option must be present. +.endlist + +An &'anonymous token'& is something passed along as an unauthenticated +identifier; this is analogous to FTP anonymous authentication passing an +email address, or software-identifier@, as the "password". + + +An example showing the password having the realm specified in the callback +and demonstrating a Cyrus SASL to GSASL migration approach is: +.code +gsasl_cyrusless_crammd5: + driver = gsasl + public_name = CRAM-MD5 + server_realm = imap.example.org + server_password = ${lookup{$auth1:$auth3:userPassword}\ + dbmjz{/etc/sasldb2}{$value}fail} + server_set_id = ${quote:$auth1} + server_condition = yes +.endd + +.wen + +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.new +.chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss" +.scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator" +.scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&" +.cindex "authentication" "GSSAPI" +.cindex "authentication" "Kerberos" +The &(heimdal_gssapi)& authenticator provides server integration for the +Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname +reliably. + +.option server_hostname heimdal_gssapi string&!! "see below" +This option selects the hostname that is used, with &%server_service%&, +for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'& +identifier. The default value is &`$primary_hostname`&. + +.option server_keytab heimdal_gssapi string&!! unset +If set, then Heimdal will not use the system default keytab (typically +&_/etc/krb5.keytab_&) but instead the pathname given in this option. +The value should be a pathname, with no &"file:"& prefix. + +.option server_service heimdal_gssapi string&!! "smtp" +This option specifies the service identifier used, in conjunction with +&%server_hostname%&, for building the identifer for finding credentials +from the keytab. + + +.section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar" +Beware that these variables will typically include a realm, thus will appear +to be roughly like an email address already. The &'authzid'& in &$auth2$& is +not verified, so a malicious client can set it to anything. + +The &$auth1$& field should be safely trustable as a value from the Key +Distribution Center. Note that these are not quite email addresses. +Each identifier is for a role, and so the left-hand-side may include a +role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&. + +.vindex "&$auth1$&, &$auth2$&, etc" +.ilist +.vindex "&$auth1$&" +&$auth1$&: the &'authentication id'&, set to the GSS Display Name. +.next +.vindex "&$auth2$&" +&$auth2$&: the &'authorization id'&, sent within SASL encapsulation after +authentication. If that was empty, this will also be set to the +GSS Display Name. +.endlist + +.wen + . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -23887,8 +24997,12 @@ The &%tls_verify_certificates%& option must contain the name of a file, not the name of a directory (for OpenSSL it can be either). .next The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no -facility for varying its Diffie-Hellman parameters. I understand that this has -changed, but Exim has not been updated to provide this facility. +facility for varying its Diffie-Hellman parameters. +.new +Since then, the GnuTLS support has been updated to generate parameters upon +demand, keeping them in the spool directory. See &<>& for +details. +.wen .next .vindex "&$tls_peerdn$&" Distinguished Name (DN) strings reported by the OpenSSL library use a slash for @@ -23896,24 +25010,35 @@ separating fields; GnuTLS uses commas, in accordance with RFC 2253. This affects the value of the &$tls_peerdn$& variable. .next OpenSSL identifies cipher suites using hyphens as separators, for example: -DES-CBC3-SHA. GnuTLS uses underscores, for example: RSA_ARCFOUR_SHA. What is -more, OpenSSL complains if underscores are present in a cipher list. To make -life simpler, Exim changes underscores to hyphens for OpenSSL and hyphens to -underscores for GnuTLS when processing lists of cipher suites in the +DES-CBC3-SHA. GnuTLS historically used underscores, for example: +RSA_ARCFOUR_SHA. What is more, OpenSSL complains if underscores are present +in a cipher list. To make life simpler, Exim changes underscores to hyphens +for OpenSSL and passes the string unchanged to GnuTLS (expecting the library +to handle its own older variants) when processing lists of cipher suites in the &%tls_require_ciphers%& options (the global option and the &(smtp)& transport option). .next The &%tls_require_ciphers%& options operate differently, as described in the sections &<>& and &<>&. +.new +.next +Some other recently added features may only be available in one or the other. +This should be documented with the feature. If the documentation does not +explicitly state that the feature is infeasible in the other TLS +implementation, then patches are welcome. +.wen .endlist -.section "GnuTLS parameter computation" "SECID181" -GnuTLS uses RSA and D-H parameters that may take a substantial amount of time +.section "GnuTLS parameter computation" "SECTgnutlsparam" +.new +GnuTLS uses D-H parameters that may take a substantial amount of time to compute. It is unreasonable to re-compute them for every TLS session. Therefore, Exim keeps this data in a file in its spool directory, called -&_gnutls-params_&. The file is owned by the Exim user and is readable only by -its owner. Every Exim process that start up GnuTLS reads the RSA and D-H +&_gnutls-params-NNNN_& for some value of NNNN, corresponding to the number +of bits requested. +The file is owned by the Exim user and is readable only by +its owner. Every Exim process that start up GnuTLS reads the D-H parameters from this file. If the file does not exist, the first Exim process that needs it computes the data and writes it to a temporary file which is renamed once it is complete. It does not matter if several Exim processes do @@ -23930,26 +25055,45 @@ until enough randomness (entropy) is available. This may cause Exim to hang for a substantial amount of time, causing timeouts on incoming connections. The solution is to generate the parameters externally to Exim. They are stored -in &_gnutls-params_& in PEM format, which means that they can be generated -externally using the &(certtool)& command that is part of GnuTLS. +in &_gnutls-params-N_& in PEM format, which means that they can be +generated externally using the &(certtool)& command that is part of GnuTLS. To replace the parameters with new ones, instead of deleting the file and letting Exim re-create it, you can generate new parameters using &(certtool)& and, when this has been done, replace Exim's cache file by renaming. The relevant commands are something like this: .code +# ls +[ look for file; assume gnutls-params-2236 is the most recent ] # rm -f new-params # touch new-params # chown exim:exim new-params +# chmod 0600 new-params +# certtool --generate-dh-params --bits 2236 >>new-params # chmod 0400 new-params -# certtool --generate-privkey --bits 512 >new-params -# echo "" >>new-params -# certtool --generate-dh-params --bits 1024 >> new-params -# mv new-params gnutls-params +# mv new-params gnutls-params-2236 .endd If Exim never has to generate the parameters itself, the possibility of stalling is removed. +The filename changed in Exim 4.80, to gain the -bits suffix. The value which +Exim will choose depends upon the version of GnuTLS in use. For older GnuTLS, +the value remains hard-coded in Exim as 1024. As of GnuTLS 2.12.x, there is +a way for Exim to ask for the "normal" number of bits for D-H public-key usage, +and Exim does so. This attempt to remove Exim from TLS policy decisions +failed, as GnuTLS 2.12 returns a value higher than the current hard-coded limit +of the NSS library. Thus Exim gains the &%tls_dh_max_bits%& global option, +which applies to all D-H usage, client or server. If the value returned by +GnuTLS is greater than &%tls_dh_max_bits%& then the value will be clamped down +to &%tls_dh_max_bits%&. The default value has been set at the current NSS +limit, which is still much higher than Exim historically used. + +The filename and bits used will change as the GnuTLS maintainers change the +value for their parameter &`GNUTLS_SEC_PARAM_NORMAL`&, as clamped by +&%tls_dh_max_bits%&. At the time of writing (mid 2012), GnuTLS 2.12 recommends +2432 bits, while NSS is limited to 2236 bits. +.wen + .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl" .cindex "TLS" "requiring specific ciphers (OpenSSL)" @@ -23958,7 +25102,10 @@ There is a function in the OpenSSL library that can be passed a list of cipher suites before the cipher negotiation takes place. This specifies which ciphers are acceptable. The list is colon separated and may contain names like DES-CBC3-SHA. Exim passes the expanded value of &%tls_require_ciphers%& -directly to this function call. The following quotation from the OpenSSL +directly to this function call. +Many systems will install the OpenSSL manual-pages, so you may have +&'ciphers(1)'& available to you. +The following quotation from the OpenSSL documentation specifies what forms of item are allowed in the cipher string: .ilist @@ -23995,6 +25142,26 @@ includes any ciphers already present they will be ignored: that is, they will not be moved to the end of the list. .endlist +.new +The OpenSSL &'ciphers(1)'& command may be used to test the results of a given +string: +.code +# note single-quotes to get ! past any shell history expansion +$ openssl ciphers 'HIGH:!MD5:!SHA1' +.endd + +This example will let the library defaults be permitted on the MX port, where +there's probably no identity verification anyway, but ups the ante on the +submission ports where the administrator might have some influence on the +choice of clients used: +.code +# OpenSSL variant; see man ciphers(1) +tls_require_ciphers = ${if =={$received_port}{25}\ + {DEFAULT}\ + {HIGH:!MD5:!SHA1}} +.endd +.wen + .new @@ -24005,81 +25172,47 @@ not be moved to the end of the list. .cindex "TLS" "specifying key exchange methods (GnuTLS)" .cindex "TLS" "specifying MAC algorithms (GnuTLS)" .cindex "TLS" "specifying protocols (GnuTLS)" +.cindex "TLS" "specifying priority string (GnuTLS)" .oindex "&%tls_require_ciphers%&" "GnuTLS" -The GnuTLS library allows the caller to specify separate lists of permitted key -exchange methods, main cipher algorithms, MAC algorithms, and protocols. -Unfortunately, these lists are numerical, and the library does not have a -function for turning names into numbers. Consequently, lists of recognized -names have to be built into the application. The permitted key exchange -methods, ciphers, and MAC algorithms may be used in any combination to form a -cipher suite. This is unlike OpenSSL, where complete cipher suite names are -passed to its control function. - -For compatibility with OpenSSL, the &%tls_require_ciphers%& option can be set -to complete cipher suite names such as RSA_ARCFOUR_SHA, but for GnuTLS this -option controls only the cipher algorithms. Exim searches each item in the -list for the name of an available algorithm. For example, if the list -contains RSA_AES_SHA, then AES is recognized, and the behaviour is exactly -the same as if just AES were given. - -.oindex "&%gnutls_require_kx%&" -.oindex "&%gnutls_require_mac%&" -.oindex "&%gnutls_require_protocols%&" -There are additional options called &%gnutls_require_kx%&, -&%gnutls_require_mac%&, and &%gnutls_require_protocols%& that can be used to -restrict the key exchange methods, MAC algorithms, and protocols, respectively. -These options are ignored if OpenSSL is in use. - -All four options are available as global options, controlling how Exim -behaves as a server, and also as options of the &(smtp)& transport, controlling -how Exim behaves as a client. All the values are string expanded. After -expansion, the values must be colon-separated lists, though the separator -can be changed in the usual way. - -Each of the four lists starts out with a default set of algorithms. If the -first item in a list does &'not'& start with an exclamation mark, all the -default items are deleted. In this case, only those that are explicitly -specified can be used. If the first item in a list &'does'& start with an -exclamation mark, the defaults are left on the list. - -Then, any item that starts with an exclamation mark causes the relevant -entry to be removed from the list, and any item that does not start with an -exclamation mark causes a new entry to be added to the list. Unrecognized -items in the list are ignored. Thus: -.code -tls_require_ciphers = !ARCFOUR -.endd -allows all the defaults except ARCFOUR, whereas -.code -tls_require_ciphers = AES : 3DES -.endd -allows only cipher suites that use AES or 3DES. - -For &%tls_require_ciphers%& the recognized names are AES_256, AES_128, AES -(both of the preceding), 3DES, ARCFOUR_128, ARCFOUR_40, and ARCFOUR (both of -the preceding). The default list does not contain all of these; it just has -AES_256, AES_128, 3DES, and ARCFOUR_128. - -For &%gnutls_require_kx%&, the recognized names are DHE_RSA, RSA (which -includes DHE_RSA), DHE_DSS, and DHE (which includes both DHE_RSA and -DHE_DSS). The default list contains RSA, DHE_DSS, DHE_RSA. - -For &%gnutls_require_mac%&, the recognized names are SHA (synonym SHA1), and -MD5. The default list contains SHA, MD5. - -For &%gnutls_require_protocols%&, the recognized names are TLS1 and SSL3. -The default list contains TLS1, SSL3. - -In a server, the order of items in these lists is unimportant. The server -advertises the availability of all the relevant cipher suites. However, in a -client, the order in the &%tls_require_ciphers%& list specifies a preference -order for the cipher algorithms. The first one in the client's list that is -also advertised by the server is tried first. The default order is as listed -above. +The GnuTLS library allows the caller to provide a "priority string", documented +as part of the &[gnutls_priority_init]& function. This is very similar to the +ciphersuite specification in OpenSSL. + +The &%tls_require_ciphers%& option is treated as the GnuTLS priority string. + +The &%tls_require_ciphers%& option is available both as an global option, +controlling how Exim behaves as a server, and also as an option of the +&(smtp)& transport, controlling how Exim behaves as a client. In both cases +the value is string expanded. The resulting string is not an Exim list and +the string is given to the GnuTLS library, so that Exim does not need to be +aware of future feature enhancements of GnuTLS. + +Documentation of the strings accepted may be found in the GnuTLS manual, under +"Priority strings". This is online as +&url(http://www.gnu.org/software/gnutls/manual/html_node/Priority-Strings.html), +but beware that this relates to GnuTLS 3, which may be newer than the version +installed on your system. If you are using GnuTLS 3, +&url(http://www.gnu.org/software/gnutls/manual/html_node/Listing-the-ciphersuites-in-a-priority-string.html, then the example code) +on that site can be used to test a given string. + +Prior to Exim 4.80, an older API of GnuTLS was used, and Exim supported three +additional options, "&%gnutls_require_kx%&", "&%gnutls_require_mac%&" and +"&%gnutls_require_protocols%&". &%tls_require_ciphers%& was an Exim list. + +This example will let the library defaults be permitted on the MX port, where +there's probably no identity verification anyway, and lowers security further +by increasing compatibility; but this ups the ante on the submission ports +where the administrator might have some influence on the choice of clients +used: +.code +# GnuTLS variant +tls_require_ciphers = ${if =={$received_port}{25}\ + {NORMAL:%COMPAT}\ + {SECURE128}} +.endd .wen - .section "Configuring an Exim server to use TLS" "SECID182" .cindex "TLS" "configuring an Exim server" When Exim has been built with TLS support, it advertises the availability of @@ -24160,16 +25293,17 @@ incoming message (by default &-- you can, of course, change this), and it is also included in the log line that records a message's arrival, keyed by &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%& condition can be used to test for specific cipher suites in ACLs. - -The ACLs that run for subsequent SMTP commands can check the name of the cipher -suite and vary their actions accordingly. The cipher suite names are those used -by OpenSSL. These may differ from the names used elsewhere. For example, -OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts -is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL +(For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section +&<>&.) + +Once TLS has been established, the ACLs that run for subsequent SMTP commands +can check the name of the cipher suite and vary their actions accordingly. The +cipher suite names vary, depending on which TLS library is being used. For +example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other +contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS documentation for more details. - .section "Requesting and verifying client certificates" "SECID183" .cindex "certificate" "verification of client" .cindex "TLS" "client certificate verification" @@ -24265,17 +25399,13 @@ negotiation fails, Exim closes the current connection (because it is in an unknown state), opens a new one to the same host, and then tries the delivery unencrypted. - The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)& transport provide the client with a certificate, which is passed to the server if it requests it. If the server is Exim, it will request a certificate only if -&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&: -These options must be set in the &(smtp)& transport for Exim to use TLS when it -is operating as a client. Exim does not assume that a server certificate (set -by the global options of the same name) should also be used when operating as a -client. +&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. -If &%tls_verify_certificates%& is set, it must name a file or, +If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it +must name a file or, for OpenSSL only (not GnuTLS), a directory, that contains a collection of expected server certificates. The client verifies the server's certificate against this collection, taking into account any revoked certificates that are @@ -24287,6 +25417,12 @@ list of permitted cipher suites. If either of these checks fails, delivery to the current host is abandoned, and the &(smtp)& transport tries to deliver to alternative hosts, if any. + &*Note*&: +These options must be set in the &(smtp)& transport for Exim to use TLS when it +is operating as a client. Exim does not assume that a server certificate (set +by the global options of the same name) should also be used when operating as a +client. + .vindex "&$host$&" .vindex "&$host_address$&" All the TLS options in the &(smtp)& transport are expanded before use, with @@ -24294,6 +25430,93 @@ All the TLS options in the &(smtp)& transport are expanded before use, with which the client is connected. Forced failure of an expansion causes Exim to behave as if the relevant option were unset. +.vindex &$tls_bits$& +.vindex &$tls_cipher$& +.vindex &$tls_peerdn$& +.vindex &$tls_sni$& +Before an SMTP connection is established, the +&$tls_bits$&, &$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$& +variables are emptied. (Until the first connection, they contain the values +that were set when the message was received.) If STARTTLS is subsequently +successfully obeyed, these variables are set to the relevant values for the +outgoing connection. + + + +.new +.section "Use of TLS Server Name Indication" "SECTtlssni" +.cindex "TLS" "Server Name Indication" +.vindex "&$tls_sni$&" +.oindex "&%tls_sni%&" +With TLS1.0 or above, there is an extension mechanism by which extra +information can be included at various points in the protocol. One of these +extensions, documented in RFC 6066 (and before that RFC 4366) is +&"Server Name Indication"&, commonly &"SNI"&. This extension is sent by the +client in the initial handshake, so that the server can examine the servername +within and possibly choose to use different certificates and keys (and more) +for this session. + +This is analagous to HTTP's &"Host:"& header, and is the main mechanism by +which HTTPS-enabled web-sites can be virtual-hosted, many sites to one IP +address. + +With SMTP to MX, there are the same problems here as in choosing the identity +against which to validate a certificate: you can't rely on insecure DNS to +provide the identity which you then cryptographically verify. So this will +be of limited use in that environment. + +With SMTP to Submission, there is a well-defined hostname which clients are +connecting to and can validate certificates against. Thus clients &*can*& +choose to include this information in the TLS negotiation. If this becomes +wide-spread, then hosters can choose to present different certificates to +different clients. Or even negotiate different cipher suites. + +The &%tls_sni%& option on an SMTP transport is an expanded string; the result, +if not empty, will be sent on a TLS session as part of the handshake. There's +nothing more to it. Choosing a sensible value not derived insecurely is the +only point of caution. The &$tls_sni$& variable will be set to this string +for the lifetime of the client connection (including during authentication). + +Except during SMTP client sessions, if &$tls_sni$& is set then it is a string +received from a client. +It can be logged with the &%log_selector%& item &`+tls_sni`&. + +If the string &`tls_sni`& appears in the main section's &%tls_certificate%& +option (prior to expansion) then the following options will be re-expanded +during TLS session handshake, to permit alternative values to be chosen: + +.ilist +.vindex "&%tls_certificate%&" +&%tls_certificate%& +.next +.vindex "&%tls_crl%&" +&%tls_crl%& +.next +.vindex "&%tls_privatekey%&" +&%tls_privatekey%& +.next +.vindex "&%tls_verify_certificates%&" +&%tls_verify_certificates%& +.endlist + +Great care should be taken to deal with matters of case, various injection +attacks in the string (&`../`& or SQL), and ensuring that a valid filename +can always be referenced; it is important to remember that &$tls_sni$& is +arbitrary unverified data provided prior to authentication. + +The Exim developers are proceeding cautiously and so far no other TLS options +are re-expanded. + +When Exim is built againt OpenSSL, OpenSSL must have been built with support +for TLS Extensions. This holds true for OpenSSL 1.0.0+ and 0.9.8+ with +enable-tlsext in EXTRACONFIGURE. If you invoke &(openssl s_client -h)& and +see &`-servername`& in the output, then OpenSSL has support. + +When Exim is built against GnuTLS, SNI support is available as of GnuTLS +0.5.10. (Its presence predates the current API which Exim uses, so if Exim +built, then you have SNI support). +.wen + .section "Multiple messages on the same encrypted TCP/IP connection" &&& @@ -24473,6 +25696,7 @@ options in the main part of the configuration. These options are: .irow &%acl_smtp_mail%& "ACL for MAIL" .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL" .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts" +.irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations" .irow &%acl_smtp_predata%& "ACL at start of DATA command" .irow &%acl_smtp_quit%& "ACL for QUIT" .irow &%acl_smtp_rcpt%& "ACL for RCPT" @@ -24507,8 +25731,8 @@ in any of these ACLs. The &%acl_not_smtp_start%& ACL is run right at the start of receiving a non-SMTP message, before any of the message has been read. (This is the -analogue of the &%acl_smtp_predata%& ACL for SMTP input.) &new("In the case of -batched SMTP input, it runs after the DATA command has been reached.") The +analogue of the &%acl_smtp_predata%& ACL for SMTP input.) In the case of +batched SMTP input, it runs after the DATA command has been reached. The result of this ACL is ignored; it cannot be used to reject a message. If you really need to, you could set a value in an ACL variable here and reject based on that in the &%acl_not_smtp%& ACL. However, this ACL can be used to set @@ -24581,6 +25805,17 @@ and try again later, but that is their problem, though it does waste some of your resources. +.section "The SMTP DKIM ACL" "SECTDKIMACL" +The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support +enabled (which is the default). + +The ACL test specified by &%acl_smtp_dkim%& happens after a message has been +received, and is executed for each DKIM signature found in a message. If not +otherwise specified, the default action is to accept. + +For details on the operation of DKIM, see chapter &<>&. + + .section "The SMTP MIME ACL" "SECID194" The &%acl_smtp_mime%& option is available only when Exim is compiled with the content-scanning extension. For details, see chapter &<>&. @@ -24612,6 +25847,42 @@ client are given temporary error responses until QUIT is received or the connection is closed. In these special cases, the QUIT ACL does not run. +.section "The not-QUIT ACL" "SECTNOTQUITACL" +.vindex &$acl_smtp_notquit$& +The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when +an SMTP session ends without sending QUIT. However, when Exim itself is is bad +trouble, such as being unable to write to its log files, this ACL is not run, +because it might try to do things (such as write to log files) that make the +situation even worse. + +Like the QUIT ACL, this ACL is provided to make it possible to do customized +logging or to gather statistics, and its outcome is ignored. The &%delay%& +modifier is forbidden in this ACL, and the only permitted verbs are &%accept%& +and &%warn%&. + +.vindex &$smtp_notquit_reason$& +When the not-QUIT ACL is running, the variable &$smtp_notquit_reason$& is set +to a string that indicates the reason for the termination of the SMTP +connection. The possible values are: +.table2 +.irow &`acl-drop`& "Another ACL issued a &%drop%& command" +.irow &`bad-commands`& "Too many unknown or non-mail commands" +.irow &`command-timeout`& "Timeout while reading SMTP commands" +.irow &`connection-lost`& "The SMTP connection has been lost" +.irow &`data-timeout`& "Timeout while reading message data" +.irow &`local-scan-error`& "The &[local_scan()]& function crashed" +.irow &`local-scan-timeout`& "The &[local_scan()]& function timed out" +.irow &`signal-exit`& "SIGTERM or SIGINT" +.irow &`synchronization-error`& "SMTP synchronization error" +.irow &`tls-failed`& "TLS failed to start" +.endtable +In most cases when an SMTP connection is closed without having received QUIT, +Exim sends an SMTP response message before actually closing the connection. +With the exception of the &`acl-drop`& case, the default message can be +overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a +&%drop%& verb in another ACL, it is the message from the other ACL that is +used. + .section "Finding an ACL to use" "SECID195" .cindex "&ACL;" "finding which to use" @@ -24848,7 +26119,7 @@ statement), &%message%& can be used to vary the message that is sent when an SMTP command is accepted. For example, in a RCPT ACL you could have: .display &`accept `&<&'some conditions'&> -&` message = OK, I'll allow you through today`& +&` message = OK, I will allow you through today`& .endd You can specify an SMTP response code, optionally followed by an &"extended response code"& at the start of the message, but the first digit must be the @@ -24890,7 +26161,7 @@ the sending entity receives a &"success"& response. However, &%discard%& causes recipients to be discarded. If it is used in an ACL for RCPT, just the one recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the message's recipients are discarded. Recipients that are discarded before DATA -do not appear in the log line when the &%log_recipients%& log selector is set. +do not appear in the log line when the &%received_recipients%& log selector is set. If the &%log_message%& modifier is set when &%discard%& operates, its contents are added to the line that is automatically written to the log. @@ -24914,15 +26185,13 @@ The connection is always dropped after sending a 550 response. statement. If any of the conditions are not met, the ACL returns &"deny"&. For example, when checking a RCPT command, .code -.new require message = Sender did not verify verify = sender -.wen .endd passes control to subsequent statements only if the message's sender can be -verified. Otherwise, it rejects the command. &new("Note the positioning of the +verified. Otherwise, it rejects the command. Note the positioning of the &%message%& modifier, before the &%verify%& condition. The reason for this is -discussed in section &<>&.") +discussed in section &<>&. .next .cindex "&%warn%& ACL verb" @@ -25096,7 +26365,6 @@ This modifier specifies one or more header lines that are to be added to an incoming message, assuming, of course, that the message is ultimately accepted. For details, see section &<>&. -.new .vitem &*continue*&&~=&~<&'text'&> .cindex "&%continue%& ACL modifier" .cindex "database" "updating in ACL" @@ -25112,7 +26380,6 @@ Instead, all you need is .display &`continue = `&<&'some expansion'&> .endd -.wen .vitem &*control*&&~=&~<&'text'&> .cindex "&%control%& ACL modifier" @@ -25177,14 +26444,12 @@ If you want to apply a control unconditionally, you can use it with a .vitem &*delay*&&~=&~<&'time'&> .cindex "&%delay%& ACL modifier" .oindex "&%-bh%&" -.new This modifier may appear in any ACL. It causes Exim to wait for the time interval before proceeding. However, when testing Exim using the &%-bh%& option, the delay is not actually imposed (an appropriate message is output instead). The time is given in the usual Exim notation, and the delay happens as soon as the modifier is processed. In an SMTP session, pending output is flushed before the delay is imposed. -.wen Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for example: @@ -25207,7 +26472,6 @@ warn ...some conditions... accept ... .endd -.new If &%delay%& is encountered when the SMTP PIPELINING extension is in use, responses to several commands are no longer buffered and sent in one packet (as they would normally be) because all output is flushed before imposing the @@ -25215,7 +26479,6 @@ delay. This optimization is disabled so that a number of small delays do not appear to the client as one large aggregated delay that might provoke an unwanted timeout. You can, however, disable output flushing for &%delay%& by using a &%control%& modifier to set &%no_delay_flush%&. -.wen .vitem &*endpass*& @@ -25288,7 +26551,8 @@ ACL fragment writes no logging information when access is denied: &` log_reject_target =`& .endd This modifier can be used in SMTP and non-SMTP ACLs. It applies to both -permanent and temporary rejections. +permanent and temporary rejections. Its effect lasts for the rest of the +current ACL. .vitem &*logwrite*&&~=&~<&'text'&> @@ -25448,6 +26712,25 @@ warn control = caseful_local_part Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. + +.vitem &*control&~=&~debug/*&<&'options'&> +.cindex "&ACL;" "enabling debug logging" +.cindex "debugging" "enabling from an ACL" +This control turns on debug logging, almost as though Exim had been invoked +with &`-d`&, with the output going to a new logfile, by default called +&'debuglog'&. The filename can be adjusted with the &'tag'& option, which +may access any variables already defined. The logging may be adjusted with +the &'opts'& option, which takes the same values as the &`-d`& command-line +option. Some examples (which depend on variables that don't exist in all +contexts): +.code + control = debug + control = debug/tag=.$sender_host_address + control = debug/opts=+expand+acl + control = debug/tag=.$message_exim_id/opts=+expand +.endd + + .vitem &*control&~=&~enforce_sync*& &&& &*control&~=&~no_enforce_sync*& .cindex "SMTP" "synchronization checking" @@ -25508,7 +26791,6 @@ This modifier can optionally be followed by &`/no_tell`&. If the global option is told about the freezing), provided all the &*control=freeze*& modifiers that are obeyed for the current message have the &`/no_tell`& option. -.new .vitem &*control&~=&~no_delay_flush*& .cindex "SMTP" "output flushing, disabling for delay" Exim normally flushes SMTP output before implementing a delay in an ACL, to @@ -25522,7 +26804,6 @@ Exim normally flushes SMTP output before performing a callout in an ACL, to avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in use. This control, as long as it is encountered before the &%verify%& condition that causes the callout, disables such output flushing. -.wen .vitem &*control&~=&~no_mbox_unspool*& This control is available when Exim is compiled with the content scanning @@ -25559,7 +26840,6 @@ line is output. The setting of the switch can, of course, be made conditional on the calling host. Its effect lasts until the end of the SMTP connection. -.new .vitem &*control&~=&~no_pipelining*& .cindex "PIPELINING" "suppressing advertising" This control turns off the advertising of the PIPELINING extension to SMTP in @@ -25567,7 +26847,6 @@ the current session. To be useful, it must be obeyed before Exim sends its response to an EHLO command. Therefore, it should normally appear in an ACL controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also &%pipelining_advertise_hosts%&. -.wen .vitem &*control&~=&~queue_only*& .oindex "&%queue_only%&" @@ -25587,7 +26866,7 @@ This control is permitted only for the MAIL, RCPT, and start of data ACLs (the latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that the current message is a submission from a local MUA. In this case, Exim operates in &"submission mode"&, and applies certain fixups to the message if -necessary. For example, it add a &'Date:'& header line if one is not present. +necessary. For example, it adds a &'Date:'& header line if one is not present. This control is not permitted in the &%acl_smtp_data%& ACL, because that is too late (the message has already been created). @@ -25600,7 +26879,7 @@ that may be received in the same SMTP connection. .vitem &*control&~=&~suppress_local_fixups*& .cindex "submission fixups, suppressing" This control applies to locally submitted (non TCP/IP) messages, and is the -complement of &`control`& &`=`& &`submission`&. It disables the fixups that are +complement of &`control = submission`&. It disables the fixups that are normally applied to locally-submitted messages. Specifically: .ilist @@ -25618,10 +26897,8 @@ used only in the &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, and &%acl_not_smtp_start%& ACLs, because it has to be set before the message's data is read. -.new &*Note:*& This control applies only to the current message, not to any others that are being submitted at the same time using &%-bs%& or &%-bS%&. -.wen .endlist vlist @@ -25631,12 +26908,12 @@ All four possibilities for message fixups can be specified: .ilist Locally submitted, fixups applied: the default. .next -Locally submitted, no fixups applied: use &`control`& &`=`& -&`suppress_local_fixups`&. +Locally submitted, no fixups applied: use +&`control = suppress_local_fixups`&. .next Remotely submitted, no fixups applied: the default. .next -Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&. +Remotely submitted, fixups applied: use &`control = submission`&. .endlist @@ -25805,9 +27082,9 @@ negative. This condition is available only when Exim is compiled with the content-scanning extension, and it is allowed only in the ACL defined by &%acl_smtp_mime%&. It causes the current MIME part to be decoded into a file. -&new("If all goes well, the condition is true. It is false only if there are +If all goes well, the condition is true. It is false only if there are problems such as a syntax error or a memory shortage. For more details, see -chapter &<>&.") +chapter &<>&. .vitem &*demime&~=&~*&<&'extension&~list'&> .cindex "&%demime%& ACL condition" @@ -25824,7 +27101,7 @@ This condition checks for entries in DNS black lists. These are also known as &"RBL lists"&, after the original Realtime Blackhole List, but note that the use of the lists at &'mail-abuse.org'& now carries a charge. There are too many different variants of this condition to describe briefly here. See sections -&<>&--&<>& for details. +&<>&&--&<>& for details. .vitem &*domains&~=&~*&<&'domain&~list'&> .cindex "&%domains%& ACL condition" @@ -26140,7 +27417,9 @@ verified as a sender. .cindex "&ACL;" "testing a DNS list" In its simplest form, the &%dnslists%& condition tests whether the calling host is on at least one of a number of DNS lists by looking up the inverted IP -address in one or more DNS domains. For example, if the calling host's IP +address in one or more DNS domains. (Note that DNS list domains are not mail +domains, so the &`+`& syntax for named lists doesn't work - it is used for +special options instead.) For example, if the calling host's IP address is 192.168.62.43, and the ACL statement is .code deny dnslists = blackholes.mail-abuse.org : \ @@ -26301,6 +27580,8 @@ dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|... Thus, this example checks whether or not the IP addresses of the sender domain's mail servers are on the Spamhaus black list. +The key that was used for a successful DNS list lookup is put into the variable +&$dnslist_matched$& (see section &<>&). @@ -26322,21 +27603,42 @@ The values used on the RBL+ list are: .endd Section &<>& below describes how you can distinguish between different values. Some DNS lists may return more than one address record; -&new("see section &<>& for details of how they are checked.") +see section &<>& for details of how they are checked. + .section "Variables set from DNS lists" "SECID204" +.cindex "expansion" "variables, set from DNS list" .cindex "DNS list" "variables set from" .vindex "&$dnslist_domain$&" +.vindex "&$dnslist_matched$&" .vindex "&$dnslist_text$&" .vindex "&$dnslist_value$&" -When an entry is found in a DNS list, the variable &$dnslist_domain$& -contains the name of the domain that matched, and &$dnslist_value$& contains -the data from the entry. If more than one address record is returned by the DNS -lookup, all the IP addresses are included in &$dnslist_value$&, separated by -commas and spaces. The variable &$dnslist_text$& contains the contents of any -associated TXT record. For lists such as RBL+ the TXT record for a merged entry -is often not very meaningful. See section &<>& for a way of -obtaining more information. +When an entry is found in a DNS list, the variable &$dnslist_domain$& contains +the name of the overall domain that matched (for example, +&`spamhaus.example`&), &$dnslist_matched$& contains the key within that domain +(for example, &`192.168.5.3`&), and &$dnslist_value$& contains the data from +the DNS record. When the key is an IP address, it is not reversed in +&$dnslist_matched$& (though it is, of course, in the actual lookup). In simple +cases, for example: +.code +deny dnslists = spamhaus.example +.endd +the key is also available in another variable (in this case, +&$sender_host_address$&). In more complicated cases, however, this is not true. +For example, using a data lookup (as described in section &<>&) +might generate a dnslists lookup like this: +.code +deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|... +.endd +If this condition succeeds, the value in &$dnslist_matched$& might be +&`192.168.6.7`& (for example). + +If more than one address record is returned by the DNS lookup, all the IP +addresses are included in &$dnslist_value$&, separated by commas and spaces. +The variable &$dnslist_text$& contains the contents of any associated TXT +record. For lists such as RBL+ the TXT record for a merged entry is often not +very meaningful. See section &<>& for a way of obtaining more +information. You can use the DNS list variables in &%message%& or &%log_message%& modifiers &-- although these appear before the condition in the ACL, they are not @@ -26359,9 +27661,9 @@ For example, deny dnslists = rblplus.mail-abuse.org=127.0.0.2 .endd rejects only those hosts that yield 127.0.0.2. Without this additional data, -any address record is considered to be a match. &new("For the moment, we assume +any address record is considered to be a match. For the moment, we assume that the DNS lookup returns just one record. Section &<>& -describes how multiple records are handled.") +describes how multiple records are handled. More than one IP address may be given for checking, using a comma as a separator. These are alternatives &-- if any one of them matches, the @@ -26442,7 +27744,6 @@ which is less clear, and harder to maintain. -.new .section "Handling multiple DNS records from a DNS list" "SECThanmuldnsrec" A DNS lookup for a &%dnslists%& condition may return more than one DNS record, thereby providing more than one IP address. When an item in a &%dnslists%& list @@ -26503,7 +27804,6 @@ for the condition to be false. .endlist When the DNS lookup yields only a single IP address, there is no difference between &`=`& and &`==`& and between &`&&`& and &`=&&`&. -.wen @@ -26583,7 +27883,7 @@ deny condition = ${if isip4{$sender_host_address}} dnslists = some.list.example .endd -.section "Rate limiting senders" "SECTratelimiting" +.section "Rate limiting incoming messages" "SECTratelimiting" .cindex "rate limiting" "client sending" .cindex "limiting client sending rates" .oindex "&%smtp_ratelimit_*%&" @@ -26611,7 +27911,7 @@ parameter &'m'& is the maximum number of messages that a client is permitted to send in each time interval. It also specifies the number of messages permitted in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'& constant, you can allow a client to send more messages in a burst without -changing its overall sending rate limit. Conversely, if &'m'& and &'p'& are +changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are both small, messages must be sent at an even rate. There is a script in &_util/ratelimit.pl_& which extracts sending rates from @@ -26620,71 +27920,195 @@ when deploying the &%ratelimit%& ACL condition. The script prints usage instructions when it is run with no arguments. The key is used to look up the data for calculating the client's average -sending rate. This data is stored in a database maintained by Exim in its spool -directory, alongside the retry and other hints databases. The default key is -&$sender_host_address$&, which applies the limit to each client host IP address. +sending rate. This data is stored in Exim's spool directory, alongside the +retry and other hints databases. The default key is &$sender_host_address$&, +which means Exim computes the sending rate of each client host IP address. By changing the key you can change how Exim identifies clients for the purpose of ratelimiting. For example, to limit the sending rate of each authenticated user, independent of the computer they are sending from, set the key to &$authenticated_id$&. You must ensure that the lookup key is meaningful; for example, &$authenticated_id$& is only meaningful if the client has -authenticated, and you can check with the &%authenticated%& ACL condition. +authenticated (which you can check with the &%authenticated%& ACL condition). -Internally, Exim includes the smoothing constant &'p'& and the options in the -lookup key because they alter the meaning of the stored data. This is not true -for the limit &'m'&, so you can alter the configured maximum rate and Exim will -still remember clients' past behaviour, but if you alter the other ratelimit -parameters Exim forgets past behaviour. +The lookup key does not have to identify clients: If you want to limit the +rate at which a recipient receives messages, you can use the key +&`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT +ACL. -Each &%ratelimit%& condition can have up to two options. The first option -specifies what Exim measures the rate of, and the second specifies how Exim -handles excessively fast clients. The options are separated by a slash, like -the other parameters. +Each &%ratelimit%& condition can have up to four options. A &%per_*%& option +specifies what Exim measures the rate of, for example messages or recipients +or bytes. You can adjust the measurement using the &%unique=%& and/or +&%count=%& options. You can also control when Exim updates the recorded rate +using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are +separated by a slash, like the other parameters. They may appear in any order. -The &%per_conn%& option limits the client's connection rate. +Internally, Exim appends the smoothing constant &'p'& onto the lookup key with +any options that alter the meaning of the stored data. The limit &'m'& is not +stored, so you can alter the configured maximum rate and Exim will still +remember clients' past behaviour. If you change the &%per_*%& mode or add or +remove the &%unique=%& option, the lookup key changes so Exim will forget past +behaviour. The lookup key is not affected by changes to the update mode and +the &%count=%& option. -The &%per_mail%& option limits the client's rate of sending messages. This is -the default if none of the &%per_*%& options is specified. -The &%per_byte%& option limits the sender's email bandwidth. Note that it is -best to use this option in the DATA ACL; if it is used in an earlier ACL it -relies on the SIZE parameter on the MAIL command, which may be inaccurate or -completely missing. You can follow the limit &'m'& in the configuration with K, -M, or G to specify limits in kilobytes, megabytes, or gigabytes, respectively. +.section "Ratelimit options for what is being measured" "ratoptmea" +.cindex "rate limiting" "per_* options" +The &%per_conn%& option limits the client's connection rate. It is not +normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or +&%acl_not_smtp_start%& ACLs. -The &%per_cmd%& option causes Exim to recompute the rate every time the -condition is processed. This can be used to limit the SMTP command rate. The -alias &%per_rcpt%& is provided for use in the RCPT ACL instead of &%per_cmd%& -to make it clear that the effect is to limit the rate at which recipients are -accepted. Note that in this case the rate limiting engine will see a message -with many recipients as a large high-speed burst. +The &%per_mail%& option limits the client's rate of sending messages. This is +the default if none of the &%per_*%& options is specified. It can be used in +&%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&, +&%acl_smtp_data%&, or &%acl_not_smtp%&. + +The &%per_byte%& option limits the sender's email bandwidth. It can be used in +the same ACLs as the &%per_mail%& option, though it is best to use this option +in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is +used in an earlier ACL, Exim relies on the SIZE parameter given by the client +in its MAIL command, which may be inaccurate or completely missing. You can +follow the limit &'m'& in the configuration with K, M, or G to specify limits +in kilobytes, megabytes, or gigabytes, respectively. + +The &%per_rcpt%& option causes Exim to limit the rate at which recipients are +accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, +&%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In +&%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other +ACLs the rate is updated with the total recipient count in one go. Note that +in either case the rate limiting engine will see a message with many +recipients as a large high-speed burst. + +The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the +number of different recipients that the client has sent messages to in the +last time period. That is, if the client repeatedly sends messages to the same +recipient, its measured rate is not increased. This option can only be used in +&%acl_smtp_rcpt%&. +The &%per_cmd%& option causes Exim to recompute the rate every time the +condition is processed. This can be used to limit the rate of any SMTP +command. If it is used in multiple ACLs it can limit the aggregate rate of +multiple different commands. + +The &%count=%& option can be used to alter how much Exim adds to the client's +measured rate. For example, the &%per_byte%& option is equivalent to +&`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim +increases the measured rate by one (except for the &%per_rcpt%& option in ACLs +other than &%acl_smtp_rcpt%&). The count does not have to be an integer. + +The &%unique=%& option is described in section &<>& below. + + +.section "Ratelimit update modes" "ratoptupd" +.cindex "rate limiting" "reading data without updating" +You can specify one of three options with the &%ratelimit%& condition to +control when its database is updated. This section describes the &%readonly%& +mode, and the next section describes the &%strict%& and &%leaky%& modes. + +If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a +previously-computed rate to check against the limit. + +For example, you can test the client's sending rate and deny it access (when +it is too fast) in the connect ACL. If the client passes this check then it +can go on to send a message, in which case its recorded rate will be updated +in the MAIL ACL. Subsequent connections from the same client will check this +new rate. +.code +acl_check_connect: + deny ratelimit = 100 / 5m / readonly + log_message = RATE CHECK: $sender_rate/$sender_rate_period \ + (max $sender_rate_limit) +# ... +acl_check_mail: + warn ratelimit = 100 / 5m / strict + log_message = RATE UPDATE: $sender_rate/$sender_rate_period \ + (max $sender_rate_limit) +.endd + +If Exim encounters multiple &%ratelimit%& conditions with the same key when +processing a message then it may increase the client's measured rate more than +it should. For example, this will happen if you check the &%per_rcpt%& option +in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the +same &%ratelimit%& condition multiple times in the same ACL. You can avoid any +multiple update problems by using the &%readonly%& option on later ratelimit +checks. + +The &%per_*%& options described above do not make sense in some ACLs. If you +use a &%per_*%& option in an ACL where it is not normally permitted then the +update mode defaults to &%readonly%& and you cannot specify the &%strict%& or +&%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the +next section) so you must specify the &%readonly%& option explicitly. + + +.section "Ratelimit options for handling fast clients" "ratoptfast" +.cindex "rate limiting" "strict and leaky modes" If a client's average rate is greater than the maximum, the rate limiting engine can react in two possible ways, depending on the presence of the -&%strict%& or &%leaky%& options. This is independent of the other +&%strict%& or &%leaky%& update modes. This is independent of the other counter-measures (such as rejecting the message) that may be specified by the -rest of the ACL. The default mode is leaky, which avoids a sender's -over-aggressive retry rate preventing it from getting any email through. - -The &%strict%& option means that the client's recorded rate is always updated. -The effect of this is that Exim measures the client's average rate of attempts -to send email, which can be much higher than the maximum. If the client is over -the limit it will be subjected to counter-measures until it slows down below -the maximum rate. The smoothing period determines the time it takes for a high -sending rate to decay exponentially to 37% of its peak value, which means that -you can work out the time (the number of smoothing periods) that a client is -subjected to counter-measures after an over-limit burst with this formula: -.code -ln(peakrate/maxrate) -.endd -The &%leaky%& option means that the client's recorded rate is not updated if it -is above the limit. The effect of this is that Exim measures the client's -average rate of successfully sent email, which cannot be greater than the -maximum. If the client is over the limit it may suffer some +rest of the ACL. + +The &%leaky%& (default) option means that the client's recorded rate is not +updated if it is above the limit. The effect of this is that Exim measures the +client's average rate of successfully sent email, which cannot be greater than +the maximum allowed. If the client is over the limit it may suffer some counter-measures (as specified in the ACL), but it will still be able to send email at the configured maximum rate, whatever the rate of its attempts. This is generally the better choice if you have clients that retry automatically. - +For example, it does not prevent a sender with an over-aggressive retry rate +from getting any email through. + +The &%strict%& option means that the client's recorded rate is always +updated. The effect of this is that Exim measures the client's average rate +of attempts to send email, which can be much higher than the maximum it is +actually allowed. If the client is over the limit it may be subjected to +counter-measures by the ACL. It must slow down and allow sufficient time to +pass that its computed rate falls below the maximum before it can send email +again. The time (the number of smoothing periods) it must wait and not +attempt to send mail can be calculated with this formula: +.code + ln(peakrate/maxrate) +.endd + + +.section "Limiting the rate of different events" "ratoptuniq" +.cindex "rate limiting" "counting unique events" +The &%ratelimit%& &%unique=%& option controls a mechanism for counting the +rate of different events. For example, the &%per_addr%& option uses this +mechanism to count the number of different recipients that the client has +sent messages to in the last time period; it is equivalent to +&`per_rcpt/unique=$local_part@$domain`&. You could use this feature to +measure the rate that a client uses different sender addresses with the +options &`per_mail/unique=$sender_address`&. + +For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it +has seen for that key. The whole set is thrown away when it is older than the +rate smoothing period &'p'&, so each different event is counted at most once +per period. In the &%leaky%& update mode, an event that causes the client to +go over the limit is not added to the set, in the same way that the client's +recorded rate is not updated in the same situation. + +When you combine the &%unique=%& and &%readonly%& options, the specific +&%unique=%& value is ignored, and Exim just retrieves the client's stored +rate. + +The &%unique=%& mechanism needs more space in the ratelimit database than the +other &%ratelimit%& options in order to store the event set. The number of +unique values is potentially as large as the rate limit, so the extra space +required increases with larger limits. + +The uniqueification is not perfect: there is a small probability that Exim +will think a new event has happened before. If the sender's rate is less than +the limit, Exim should be more than 99.9% correct. However in &%strict%& mode +the measured rate can go above the limit, in which case Exim may under-count +events by a significant margin. Fortunately, if the rate is high enough (2.7 +times the limit) that the false positive rate goes above 9%, then Exim will +throw away the over-full event set before the measured rate falls below the +limit. Therefore the only harm should be that exceptionally high sending rates +are logged incorrectly; any countermeasures you configure will be as effective +as intended. + + +.section "Using rate limiting" "useratlim" Exim's other ACL facilities are used to define what counter-measures are taken when the rate limit is exceeded. This might be anything from logging a warning (for example, while measuring existing sending rates in order to define @@ -26726,6 +28150,7 @@ this means that Exim will lose its hints data after a reboot (including retry hints, the callout cache, and ratelimit data). + .section "Address verification" "SECTaddressverification" .cindex "verifying address" "options for" .cindex "policy control" "address verification" @@ -26873,13 +28298,11 @@ Exim tries the next host, if any. If there is a problem with all the remote hosts, the ACL yields &"defer"&, unless the &%defer_ok%& parameter of the &%callout%& option is given, in which case the condition is forced to succeed. -.new .cindex "SMTP" "output flushing, disabling for callout" A callout may take a little time. For this reason, Exim normally flushes SMTP output before performing a callout in an ACL, to avoid unexpected timeouts in clients when the SMTP PIPELINING extension is in use. The flushing can be disabled by using a &%control%& modifier to set &%no_callout_flush%&. -.wen @@ -27001,7 +28424,7 @@ check for a &"random"& local part at the same domain. The local part is not really random &-- it is defined by the expansion of the option &%callout_random_local_part%&, which defaults to .code -$primary_host_name-$tod_epoch-testing +$primary_hostname-$tod_epoch-testing .endd The idea here is to try to determine whether the remote host accepts all local parts without checking. If it does, there is no point in doing callouts for @@ -27303,19 +28726,8 @@ the third string (in this case &"1"&), whether or not the cryptographic and timeout checks succeed. The &$prvscheck_result$& variable contains the result of the checks (empty for failure, &"1"& for success). -There are two more issues you must consider when implementing prvs-signing. -Firstly, you need to ensure that prvs-signed addresses are not blocked by your -ACLs. A prvs-signed address contains a slash character, but the default Exim -configuration contains this statement in the RCPT ACL: -.code -deny message = Restricted characters in address - domains = +local_domains - local_parts = ^[.] : ^.*[@%!/|] -.endd -This is a conservative rule that blocks local parts that contain slashes. You -should remove the slash in the last line. - -Secondly, you have to ensure that the routers accept prvs-signed addresses and +There is one more issue you must consider when implementing prvs-signing: +you have to ensure that the routers accept prvs-signed addresses and deliver them correctly. The easiest way to handle this is to use a &(redirect)& router to remove the signature with a configuration along these lines: .code @@ -27502,6 +28914,7 @@ It supports a &"generic"& interface to scanners called via the shell, and specialized interfaces for &"daemon"& type virus scanners, which are resident in memory and thus are much faster. + .oindex "&%av_scanner%&" You can set the &%av_scanner%& option in first part of the Exim configuration file to specify which scanner to use, together with any additional options that @@ -27513,7 +28926,7 @@ If you do not set &%av_scanner%&, it defaults to .code av_scanner = sophie:/var/run/sophie .endd -If the value of &%av_scanner%& starts with dollar character, it is expanded +If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. The following scanner types are supported in this release: .vlist @@ -27527,6 +28940,7 @@ example: av_scanner = aveserver:/var/run/aveserver .endd + .vitem &%clamd%& .cindex "virus scanners" "clamd" This daemon-type scanner is GPL and free. You can get it at @@ -27537,8 +28951,16 @@ required: either the path and name of a UNIX socket file, or a hostname or IP number, and a port, separated by space, as in the second of these examples: .code av_scanner = clamd:/opt/clamd/socket -av_scanner = clamd:192.168.2.100 1234 -.endd +av_scanner = clamd:192.0.2.3 1234 +av_scanner = clamd:192.0.2.3 1234:local +.endd +If the value of av_scanner points to a UNIX socket file or contains the local +keyword, then the ClamAV interface will pass a filename containing the data +to be scanned, which will should normally result in less I/O happening and be +more efficient. Normally in the TCP case, the data is streamed to ClamAV as +Exim does not assume that there is a common filesystem with the remote host. +There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should +you be running a version of ClamAV prior to 0.95. If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for contributing the code for this scanner. @@ -27678,6 +29100,9 @@ If your virus scanner cannot unpack MIME and TNEF containers itself, you should use the &%demime%& condition (see section &<>&) before the &%malware%& condition. +Beware the interaction of Exim's &%message_size_limit%& with any size limits +imposed by your anti-virus scanner. + Here is a very simple scanning example: .code deny message = This message contains malware ($malware_name) @@ -27754,6 +29179,10 @@ condition defers. &*Warning*&: It is not possible to use the UNIX socket connection method with multiple &%spamd%& servers. +The &%spamd_address%& variable is expanded before use if it starts with +a dollar sign. In this case, the expansion may return a string that is +used as the list so that multiple spamd servers can be the result of an +expansion. .section "Calling SpamAssassin from an Exim ACL" "SECID206" Here is a simple example of the use of the &%spam%& condition in a DATA ACL: @@ -27796,9 +29225,8 @@ it always return &"true"& by appending &`:true`& to the username. .cindex "spam scanning" "returned variables" When the &%spam%& condition is run, it sets up a number of expansion -variables. With the exception of &$spam_score_int$&, these are usable only -within ACLs; their values are not retained with the message and so cannot be -used at delivery time. +variables. These variables are saved with the received message, thus they are +available for use at delivery time. .vlist .vitem &$spam_score$& @@ -27807,11 +29235,9 @@ for inclusion in log or reject messages. .vitem &$spam_score_int$& The spam score of the message, multiplied by ten, as an integer value. For -example &"34"& or &"305"&. This is useful for numeric comparisons in -conditions. This variable is special; its value is saved with the message, and -written to Exim's spool file. This means that it can be used during the whole -life of the message on your Exim system, in particular, in routers or -transports during the later delivery phase. +example &"34"& or &"305"&. It may appear to disagree with &$spam_score$& +because &$spam_score$& is rounded and &$spam_score_int$& is truncated. +The integer value is useful for numeric comparisons in conditions. .vitem &$spam_bar$& A string consisting of a number of &"+"& or &"-"& characters, representing the @@ -27824,14 +29250,15 @@ A multiline text table, containing the full SpamAssassin report for the message. Useful for inclusion in headers or reject messages. .endlist -The &%spam%& condition caches its results. If you call it again with the same -user name, it does not scan again, but rather returns the same values as -before. +The &%spam%& condition caches its results unless expansion in +spamd_address was used. If you call it again with the same user name, it +does not scan again, but rather returns the same values as before. -The &%spam%& condition returns DEFER if there is any error while running the -message through SpamAssassin. If you want to treat DEFER as FAIL (to pass on to -the next ACL statement block), append &`/defer_ok`& to the right-hand side of -the spam condition, like this: +The &%spam%& condition returns DEFER if there is any error while running +the message through SpamAssassin or if the expansion of spamd_address +failed. If you want to treat DEFER as FAIL (to pass on to the next ACL +statement block), append &`/defer_ok`& to the right-hand side of the +spam condition, like this: .code deny message = This message was classified as SPAM spam = joe/defer_ok @@ -27871,13 +29298,13 @@ specifies an ACL that is used for the MIME parts of non-SMTP messages. These options may both refer to the same ACL if you want the same processing in both cases. -These ACLs are called (possibly many times) just before the -&%acl_smtp_data%& ACL in the case of an SMTP message, or just before the -&%acl_not_smtp%& ACL in the case of a non-SMTP message. However, a MIME ACL -is called only if the message contains a &'MIME-Version:'& header line. When a -call to a MIME ACL does not yield &"accept"&, ACL processing is aborted and the -appropriate result code is sent to the client. In the case of an SMTP message, -the &%acl_smtp_data%& ACL is not called when this happens. +These ACLs are called (possibly many times) just before the &%acl_smtp_data%& +ACL in the case of an SMTP message, or just before the &%acl_not_smtp%& ACL in +the case of a non-SMTP message. However, a MIME ACL is called only if the +message contains a &'Content-Type:'& header line. When a call to a MIME +ACL does not yield &"accept"&, ACL processing is aborted and the appropriate +result code is sent to the client. In the case of an SMTP message, the +&%acl_smtp_data%& ACL is not called when this happens. You cannot use the &%malware%& or &%spam%& conditions in a MIME ACL; these can only be used in the DATA or non-SMTP ACLs. However, you can use the &%regex%& @@ -27913,9 +29340,9 @@ the full path and file name. If the string does not start with a slash, it is used as the filename, and the default path is then used. .endlist -&new("The &%decode%& condition normally succeeds. It is only false for syntax -errors or unusual circumstances such as memory shortages.") -You can easily decode a file with its original, proposed filename using +The &%decode%& condition normally succeeds. It is only false for syntax +errors or unusual circumstances such as memory shortages. You can easily decode +a file with its original, proposed filename using .code decode = $mime_filename .endd @@ -28430,11 +29857,17 @@ out the values of all the &[local_scan()]& options. .cindex "&[local_scan()]& function" "available Exim variables" The header &_local_scan.h_& gives you access to a number of C variables. These are the only ones that are guaranteed to be maintained from release to release. -Note, however, that you can obtain the value of any Exim variable, -&new("including &$recipients$&,") by calling &'expand_string()'&. The exported -variables are as follows: +Note, however, that you can obtain the value of any Exim expansion variable, +including &$recipients$&, by calling &'expand_string()'&. The exported +C variables are as follows: .vlist +.vitem &*int&~body_linecount*& +This variable contains the number of lines in the message's body. + +.vitem &*int&~body_zerocount*& +This variable contains the number of binary zero bytes in the message's body. + .vitem &*unsigned&~int&~debug_selector*& This variable is set to zero when no debugging is taking place. Otherwise, it is a bitmap of debugging selectors. Two bits are identified for use in @@ -30004,8 +31437,8 @@ If a message contains a number of different addresses, all those with the same characteristics (for example, the same envelope sender) that resolve to the same set of hosts, in the same order, are sent in a single SMTP transaction, even if they are for different domains, unless there are more than the setting -of the &%max_rcpts%& option in the &(smtp)& transport allows, in which case -they are split into groups containing no more than &%max_rcpts%& addresses +of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case +they are split into groups containing no more than &%max_rcpt%&s addresses each. If &%remote_max_parallel%& is greater than one, such groups may be sent in parallel sessions. The order of hosts with identical MX values is not significant when checking whether addresses can be batched in this way. @@ -30491,8 +31924,8 @@ rejected (there seems little point) but instead just get qualified. HELO and EHLO act as RSET; VRFY, EXPN, ETRN and HELP, act as NOOP; QUIT quits. -No policy checking is done for BSMTP input. That is, no ACL is run at anytime. -In this respect it is like non-SMTP local input. +Minimal policy checking is done for BSMTP input. Only the non-SMTP +ACL is run in the same way as for non-SMTP local input. If an error is detected while reading a message, including a missing &"."& at the end, Exim gives up immediately. It writes details of the error to the @@ -31288,7 +32721,7 @@ are ever generated. No retry data is maintained, and any retry rules are ignored. .next A number of Exim options are overridden: &%deliver_drop_privilege%& is forced -true, &%max_rcpt%& in the smtp transport is forced to &"unlimited"&, +true, &%max_rcpt%& in the &(smtp)& transport is forced to &"unlimited"&, &%remote_max_parallel%& is forced to one, and fallback hosts are ignored. .endlist @@ -31372,14 +32805,12 @@ example: .endd .endlist -.new .cindex "log" "process ids in" .cindex "pid (process id)" "in log lines" Exim does not include its process id in log lines by default, but you can request that it does so by specifying the &`pid`& log selector (see section &<>&). When this is set, the process id is output, in square brackets, immediately after the time and date. -.wen @@ -31431,8 +32862,8 @@ log_file_path = $spool_directory/log/%slog If you do not specify anything at build time or run time, that is where the logs are written. -A log file path may also contain &`%D`& if datestamped log file names are in -use &-- see section &<>& below. +A log file path may also contain &`%D`& or &`%M`& if datestamped log file names +are in use &-- see section &<>& below. Here are some examples of possible settings: .display @@ -31476,14 +32907,15 @@ renamed. .cindex "log" "datestamped files" Instead of cycling the main and reject log files by renaming them periodically, some sites like to use files whose names contain a datestamp, -for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&. -Exim has support for this way of working. It is enabled by setting the -&%log_file_path%& option to a path that includes &`%D`& at the point where the -datestamp is required. For example: +for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or +&_yyyymm_&. Exim has support for this way of working. It is enabled by setting +the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the +point where the datestamp is required. For example: .code log_file_path = /var/spool/exim/log/%slog-%D log_file_path = /var/log/exim-%s-%D.log log_file_path = /var/spool/exim/log/%D-%slog +log_file_path = /var/log/exim/%s.%M .endd As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are examples of names generated by the above examples: @@ -31491,6 +32923,7 @@ examples of names generated by the above examples: /var/spool/exim/log/mainlog-20021225 /var/log/exim-reject-20021225.log /var/spool/exim/log/20021225-mainlog +/var/log/exim/main.200212 .endd When this form of log file is specified, Exim automatically switches to new files at midnight. It does not make any attempt to compress old logs; you @@ -31499,14 +32932,16 @@ run &'exicyclog'& with this form of logging. The location of the panic log is also determined by &%log_file_path%&, but it is not datestamped, because rotation of the panic log does not make sense. -When generating the name of the panic log, &`%D`& is removed from the string. -In addition, if it immediately follows a slash, a following non-alphanumeric -character is removed; otherwise a preceding non-alphanumeric character is -removed. Thus, the three examples above would give these panic log names: +When generating the name of the panic log, &`%D`& or &`%M`& are removed from +the string. In addition, if it immediately follows a slash, a following +non-alphanumeric character is removed; otherwise a preceding non-alphanumeric +character is removed. Thus, the four examples above would give these panic +log names: .code /var/spool/exim/log/paniclog /var/log/exim-panic.log /var/spool/exim/log/paniclog +/var/log/exim/panic .endd @@ -31817,13 +33252,9 @@ the following table: .display &`A `& authenticator name (and optional id) &`C `& SMTP confirmation on delivery -.new &` `& command list for &"no mail in SMTP session"& -.wen &`CV `& certificate verification status -.new &`D `& duration of &"no mail in SMTP session"& -.wen &`DN `& distinguished name from peer certificate &`DT `& on &`=>`& lines: time taken for a delivery &`F `& sender address (on delivery lines) @@ -31922,9 +33353,7 @@ selection marked by asterisks: &`*queue_run `& start and end queue runs &` queue_time `& time on queue for one recipient &` queue_time_overall `& time on queue for whole message -.new &` pid `& Exim process id -.wen &` received_recipients `& recipients on <= lines &` received_sender `& sender on <= lines &`*rejected_header `& header contents on reject log @@ -31937,15 +33366,14 @@ selection marked by asterisks: &` smtp_confirmation `& SMTP confirmation on => lines &` smtp_connection `& SMTP connections &` smtp_incomplete_transaction`& incomplete SMTP transactions -.new &` smtp_no_mail `& session with no MAIL commands -.wen &` smtp_protocol_error `& SMTP protocol errors &` smtp_syntax_error `& SMTP syntax errors &` subject `& contents of &'Subject:'& on <= lines &` tls_certificate_verified `& certificate verification status &`*tls_cipher `& TLS cipher suite on <= and => lines &` tls_peerdn `& TLS peer DN on <= and => lines +&` tls_sni `& TLS SNI on <= lines &` unknown_in_list `& DNS lookup failed in list match &` all `& all of the above @@ -32058,12 +33486,10 @@ containing => tags) following the IP address. This option is not included in the default setting, because for most ordinary configurations, the remote port number is always 25 (the SMTP port). .next -.new .cindex "log" "process ids in" .cindex "pid (process id)" "in log lines" &%pid%&: The current process id is added to every log line, in square brackets, immediately after the time and date. -.wen .next .cindex "log" "queue run" .cindex "queue runner" "logging" @@ -32173,7 +33599,6 @@ RSET, QUIT, loss of connection, or otherwise, the incident is logged, and the message sender plus any accepted recipients are included in the log line. This can provide evidence of dictionary attacks. .next -.new .cindex "log" "non-MAIL SMTP sessions" .cindex "MAIL" "logging session without" &%smtp_no_mail%&: A line is written to the main log whenever an accepted SMTP @@ -32200,7 +33625,6 @@ than 20 commands, they are all listed. If there were more than 20 commands, the last 20 are listed, preceded by &"..."&. However, with the default setting of 10 for &%smtp_accep_max_nonmail%&, the connection will in any case have been aborted before 20 non-mail commands are processed. -.wen .next .cindex "log" "SMTP protocol error" .cindex "SMTP" "logging protocol error" @@ -32245,6 +33669,12 @@ connection, the cipher suite used is added to the log line, preceded by X=. connection, and a certificate is supplied by the remote host, the peer DN is added to the log line, preceded by DN=. .next +.cindex "log" "TLS SNI" +.cindex "TLS" "logging SNI" +&%tls_sni%&: When a message is received over an encrypted connection, and +the remote host provided the Server Name Indication extension, the SNI is +added to the log line, preceded by SNI=. +.next .cindex "log" "DNS failure in list" &%unknown_in_list%&: This setting causes a log entry to be written when the result of a list match is failure because a DNS lookup failed. @@ -32462,7 +33892,6 @@ extracts all the log entries for the relevant message, not just those that match the pattern. Thus, &'exigrep'& can extract complete log entries for a given message, or all mail for a given user, or for a given host, for example. The input files can be in Exim log format or syslog format. -.new If a matching log line is not associated with a specific message, it is included in &'exigrep'&'s output without any additional lines. The usage is: .display @@ -32486,7 +33915,6 @@ regular expression. The &%-v%& option inverts the matching condition. That is, a line is selected if it does &'not'& match the pattern. -.wen If the location of a &'zcat'& command is known from the definition of ZCAT_COMMAND in &_Local/Makefile_&, &'exigrep'& automatically passes any file @@ -33037,6 +34465,12 @@ End In order to see the contents of messages on the queue, and to operate on them, &'eximon'& must either be run as root or by an admin user. +The command-line parameters of &'eximon'& are passed to &_eximon.bin_& and may +contain X11 resource parameters interpreted by the X11 library. In addition, +if the first parameter starts with the string "gdb" then it is removed and the +binary is invoked under gdb (the parameter is used as the gdb command-name, so +versioned variants of gdb can be invoked). + The monitor's window is divided into three parts. The first contains one or more stripcharts and two action buttons, the second contains a &"tail"& of the main log file, and the third is a display of the queue of messages awaiting @@ -33359,15 +34793,26 @@ which only root has access, this guards against someone who has broken into the Exim account from running a privileged Exim with an arbitrary configuration file, and using it to break into other accounts. .next -If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%& -and &%-D%& only if the caller of Exim is root. Without it, the Exim user may -also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out -the possibility of testing a configuration using &%-C%& right through message -reception and delivery, even if the caller is root. The reception works, but by -that time, Exim is running as the Exim user, so when it re-execs to regain -privilege for the delivery, the use of &%-C%& causes privilege to be lost. -However, root can test reception and delivery using two separate commands. -ALT_CONFIG_ROOT_ONLY is not set by default. + +If a non-trusted configuration file (i.e. not the default configuration file +or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST +file) is specified with &%-C%&, or if macros are given with &%-D%& (but see +the next item), then root privilege is retained only if the caller of Exim is +root. This locks out the possibility of testing a configuration using &%-C%& +right through message reception and delivery, even if the caller is root. The +reception works, but by that time, Exim is running as the Exim user, so when +it re-execs to regain privilege for the delivery, the use of &%-C%& causes +privilege to be lost. However, root can test reception and delivery using two +separate commands. + +.next +The WHITELIST_D_MACROS build option declares some macros to be safe to override +with &%-D%& if the real uid is one of root, the Exim run-time user or the +CONFIGURE_OWNER, if defined. The potential impact of this option is limited by +requiring the run-time value supplied to &%-D%& to match a regex that errs on +the restrictive side. Requiring build-time selection of safe macros is onerous +but this option is intended solely as a transition mechanism to permit +previously-working configurations to continue to work after release 4.73. .next If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option is disabled. @@ -33381,7 +34826,6 @@ is permitted to modify the runtime file from using Exim as a way to get root. - .section "Root privilege" "SECID270" .cindex "setuid" .cindex "root privilege" @@ -33423,11 +34867,13 @@ uid and gid in the following cases: .oindex "&%-D%&" If the &%-C%& option is used to specify an alternate configuration file, or if the &%-D%& option is used to define macro values for the configuration, and the -calling process is not running as root or the Exim user, the uid and gid are -changed to those of the calling process. -However, if ALT_CONFIG_ROOT_ONLY is defined in &_Local/Makefile_&, only -root callers may use &%-C%& and &%-D%& without losing privilege, and if -DISABLE_D_OPTION is set, the &%-D%& option may not be used at all. +calling process is not running as root, the uid and gid are changed to those of +the calling process. +However, if DISABLE_D_OPTION is defined in &_Local/Makefile_&, the &%-D%& +option may not be used at all. +If WHITELIST_D_MACROS is defined in &_Local/Makefile_&, then some macro values +can be supplied if the calling process is running as root, the Exim run-time +user or CONFIGURE_OWNER, if defined. .next .oindex "&%-be%&" .oindex "&%-bf%&" @@ -33684,6 +35130,12 @@ arbitrary program's being run as exim, not as root. +.section "Dynamic module directory" "SECTdynmoddir" +Any dynamically loadable modules must be installed into the directory +defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit +loading it. + + .section "Use of sprintf()" "SECID279" .cindex "&[sprintf()]&" A large number of occurrences of &"sprintf"& in the code are actually calls to @@ -33751,11 +35203,8 @@ If the message is in MIME format, you must take care not to break it. If the message is cryptographically signed, any change will invalidate the signature. .endlist -.new All in all, modifying -D files is fraught with danger. -.wen -.new Files whose names end with -J may also be seen in the &_input_& directory (or its subdirectories when &%split_spool_directory%& is set). These are journal files, used to record addresses to which the message has been delivered during @@ -33765,7 +35214,6 @@ is some kind of crash (for example, a power outage) before this happens, the -J file remains in existence. When Exim next processes the message, it notices the -J file and uses it to update the -H file before starting the next delivery attempt. -.wen .section "Format of the -H file" "SECID282" .cindex "uid (user id)" "in spool file" @@ -33773,7 +35221,7 @@ attempt. The second line of the -H file contains the login name for the uid of the process that called Exim to read the message, followed by the numerical uid and gid. For a locally generated message, this is normally the user who sent the -message. For a message received over TCP/IP &new("via the daemon"), it is +message. For a message received over TCP/IP via the daemon, it is normally the Exim user. The third line of the file contains the address of the message's sender as @@ -34034,13 +35482,279 @@ unqualified domain &'foundation'&. .ecindex IIDforspo2 .ecindex IIDforspo3 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.chapter "Support for DKIM (DomainKeys Identified Mail)" "CHID12" &&& + "DKIM Support" +.cindex "DKIM" + +DKIM is a mechanism by which messages sent by some entity can be provably +linked to a domain which that entity controls. It permits reputation to +be tracked on a per-domain basis, rather than merely upon source IP address. +DKIM is documented in RFC 4871. + +Since version 4.70, DKIM support is compiled into Exim by default. It can be +disabled by setting DISABLE_DKIM=yes in Local/Makefile. + +Exim's DKIM implementation allows to +.olist +Sign outgoing messages: This function is implemented in the SMTP transport. +It can co-exist with all other Exim features, including transport filters. +.next +Verify signatures in incoming messages: This is implemented by an additional +ACL (acl_smtp_dkim), which can be called several times per message, with +different signature contexts. +.endlist + +In typical Exim style, the verification implementation does not include any +default "policy". Instead it enables you to build your own policy using +Exim's standard controls. + +Please note that verification of DKIM signatures in incoming mail is turned +on by default for logging purposes. For each signature in incoming email, +exim will log a line displaying the most important signature details, and the +signature status. Here is an example (with line-breaks added for clarity): +.code +2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: + d=facebookmail.com s=q1-2009b + c=relaxed/relaxed a=rsa-sha1 + i=@facebookmail.com t=1252484542 [verification succeeded] +.endd +You might want to turn off DKIM verification processing entirely for internal +or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL +control modifier. This should typically be done in the RCPT ACL, at points +where you accept mail from relay sources (internal hosts or authenticated +senders). + + +.section "Signing outgoing messages" "SECID513" +.cindex "DKIM" "signing" + +Signing is implemented by setting private options on the SMTP transport. +These options take (expandable) strings as arguments. + +.option dkim_domain smtp string&!! unset +MANDATORY: +The domain you want to sign with. The result of this expanded +option is put into the &%$dkim_domain%& expansion variable. + +.option dkim_selector smtp string&!! unset +MANDATORY: +This sets the key selector string. You can use the &%$dkim_domain%& expansion +variable to look up a matching selector. The result is put in the expansion +variable &%$dkim_selector%& which should be used in the &%dkim_private_key%& +option along with &%$dkim_domain%&. + +.option dkim_private_key smtp string&!! unset +MANDATORY: +This sets the private key to use. You can use the &%$dkim_domain%& and +&%$dkim_selector%& expansion variables to determine the private key to use. +The result can either +.ilist +be a valid RSA private key in ASCII armor, including line breaks. +.next +start with a slash, in which case it is treated as a file that contains +the private key. +.next +be "0", "false" or the empty string, in which case the message will not +be signed. This case will not result in an error, even if &%dkim_strict%& +is set. +.endlist + +.option dkim_canon smtp string&!! unset +OPTIONAL: +This option sets the canonicalization method used when signing a message. +The DKIM RFC currently supports two methods: "simple" and "relaxed". +The option defaults to "relaxed" when unset. Note: the current implementation +only supports using the same canonicalization method for both headers and body. + +.option dkim_strict smtp string&!! unset +OPTIONAL: +This option defines how Exim behaves when signing a message that +should be signed fails for some reason. When the expansion evaluates to +either "1" or "true", Exim will defer. Otherwise Exim will send the message +unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion +variables here. + +.option dkim_sign_headers smtp string&!! unset +OPTIONAL: +When set, this option must expand to (or be specified as) a colon-separated +list of header names. Headers with these names will be included in the message +signature. When unspecified, the header names recommended in RFC4871 will be +used. + + +.section "Verifying DKIM signatures in incoming mail" "SECID514" +.cindex "DKIM" "verification" + +Verification of DKIM signatures in incoming email is implemented via the +&%acl_smtp_dkim%& ACL. By default, this ACL is called once for each +syntactically(!) correct signature in the incoming message. + +To evaluate the signature in the ACL a large number of expansion variables +containing the signature status and its details are set up during the +runtime of the ACL. + +Calling the ACL only for existing signatures is not sufficient to build +more advanced policies. For that reason, the global option +&%dkim_verify_signers%&, and a global expansion variable +&%$dkim_signers%& exist. + +The global option &%dkim_verify_signers%& can be set to a colon-separated +list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is +called. It is expanded when the message has been received. At this point, +the expansion variable &%$dkim_signers%& already contains a colon-separated +list of signer domains and identities for the message. When +&%dkim_verify_signers%& is not specified in the main configuration, +it defaults as: +.code +dkim_verify_signers = $dkim_signers +.endd +This leads to the default behaviour of calling &%acl_smtp_dkim%& for each +DKIM signature in the message. Current DKIM verifiers may want to explicitly +call the ACL for known domains or identities. This would be achieved as follows: +.code +dkim_verify_signers = paypal.com:ebay.com:$dkim_signers +.endd +This would result in &%acl_smtp_dkim%& always being called for "paypal.com" +and "ebay.com", plus all domains and identities that have signatures in the message. +You can also be more creative in constructing your policy. For example: +.code +dkim_verify_signers = $sender_address_domain:$dkim_signers +.endd +If a domain or identity is listed several times in the (expanded) value of +&%dkim_verify_signers%&, the ACL is only called once for that domain or identity. +Inside the &%acl_smtp_dkim%&, the following expansion variables are +available (from most to least important): + + +.vlist +.vitem &%$dkim_cur_signer%& +The signer that is being evaluated in this ACL run. This can be a domain or +an identity. This is one of the list items from the expanded main option +&%dkim_verify_signers%& (see above). +.vitem &%$dkim_verify_status%& +A string describing the general status of the signature. One of +.ilist +&%none%&: There is no signature in the message for the current domain or +identity (as reflected by &%$dkim_cur_signer%&). +.next +&%invalid%&: The signature could not be verified due to a processing error. +More detail is available in &%$dkim_verify_reason%&. +.next +&%fail%&: Verification of the signature failed. More detail is +available in &%$dkim_verify_reason%&. +.next +&%pass%&: The signature passed verification. It is valid. +.endlist +.vitem &%$dkim_verify_reason%& +A string giving a litte bit more detail when &%$dkim_verify_status%& is either +"fail" or "invalid". One of +.ilist +&%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public +key for the domain could not be retrieved. This may be a temporary problem. +.next +&%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key +record for the domain is syntactically invalid. +.next +&%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated +body hash does not match the one specified in the signature header. This +means that the message body was modified in transit. +.next +&%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature +could not be verified. This may mean that headers were modified, +re-written or otherwise changed in a way which is incompatible with +DKIM verification. It may of course also mean that the signature is forged. +.endlist +.vitem &%$dkim_domain%& +The signing domain. IMPORTANT: This variable is only populated if there is +an actual signature in the message for the current domain or identity (as +reflected by &%$dkim_cur_signer%&). +.vitem &%$dkim_identity%& +The signing identity, if present. IMPORTANT: This variable is only populated +if there is an actual signature in the message for the current domain or +identity (as reflected by &%$dkim_cur_signer%&). +.vitem &%$dkim_selector%& +The key record selector string. +.vitem &%$dkim_algo%& +The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'. +.vitem &%$dkim_canon_body%& +The body canonicalization method. One of 'relaxed' or 'simple'. +.vitem &%dkim_canon_headers%& +The header canonicalization method. One of 'relaxed' or 'simple'. +.vitem &%$dkim_copiedheaders%& +A transcript of headers and their values which are included in the signature +(copied from the 'z=' tag of the signature). +.vitem &%$dkim_bodylength%& +The number of signed body bytes. If zero ("0"), the body is unsigned. If no +limit was set by the signer, "9999999999999" is returned. This makes sure +that this variable always expands to an integer value. +.vitem &%$dkim_created%& +UNIX timestamp reflecting the date and time when the signature was created. +When this was not specified by the signer, "0" is returned. +.vitem &%$dkim_expires%& +UNIX timestamp reflecting the date and time when the signer wants the +signature to be treated as "expired". When this was not specified by the +signer, "9999999999999" is returned. This makes it possible to do useful +integer size comparisons against this value. +.vitem &%$dkim_headernames%& +A colon-separated list of names of headers included in the signature. +.vitem &%$dkim_key_testing%& +"1" if the key record has the "testing" flag set, "0" if not. +.vitem &%$nosubdomains%& +"1" if the key record forbids subdomaining, "0" otherwise. +.vitem &%$dkim_key_srvtype%& +Service type (tag s=) from the key record. Defaults to "*" if not specified +in the key record. +.vitem &%$dkim_key_granularity%& +Key granularity (tag g=) from the key record. Defaults to "*" if not specified +in the key record. +.vitem &%$dkim_key_notes%& +Notes from the key record (tag n=). +.endlist + +In addition, two ACL conditions are provided: + +.vlist +.vitem &%dkim_signers%& +ACL condition that checks a colon-separated list of domains or identities +for a match against the domain or identity that the ACL is currently verifying +(reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL +verb to a group of domains or identities. For example: + +.code +# Warn when Mail purportedly from GMail has no signature at all +warn log_message = GMail sender without DKIM signature + sender_domains = gmail.com + dkim_signers = gmail.com + dkim_status = none +.endd + +.vitem &%dkim_status%& +ACL condition that checks a colon-separated list of possible DKIM verification +results agains the actual result of verification. This is typically used +to restrict an ACL verb to a list of verification outcomes, for example: + +.code +deny message = Mail from Paypal with invalid/missing signature + sender_domains = paypal.com:paypal.de + dkim_signers = paypal.com:paypal.de + dkim_status = none:invalid:fail +.endd + +The possible status keywords are: 'none','invalid','fail' and 'pass'. Please +see the documentation of the &%$dkim_verify_status%& expansion variable above +for more information of what they mean. +.endlist + . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// -.chapter "Adding new drivers or lookup types" "CHID12" &&& +.chapter "Adding new drivers or lookup types" "CHID13" &&& "Adding drivers or lookups" .cindex "adding drivers" .cindex "new drivers, adding"