X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/210f147e47759d98c1220a6c3b8bf185743a31df..dce7179da790a596fcf724774a751db65f4adcb0:/doc/doc-docbook/spec.xfpt?ds=sidebyside diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index a4bbac4bf..7ab482c3c 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1,5 +1,3 @@ -. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.28 2008/01/17 12:56:12 nm4 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 @@ -43,16 +41,19 @@ .book . ///////////////////////////////////////////////////////////////////////////// -. These definitions set some parameters and save some typing. Remember that -. the element must also be updated for each new edition. +. These definitions set some parameters and save some typing. +. Update the Copyright year (only) when changing content. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.69" -.set version "4.70" +.set previousversion "4.80" +.include ./local_params .set ACL "access control lists (ACLs)" .set I "    " +.macro copyyear +2012 +.endmacro . ///////////////////////////////////////////////////////////////////////////// . Additional xfpt markup used by this document, over and above the default @@ -172,17 +173,23 @@ Specification of the Exim Mail Transfer Agent The Exim MTA -23 August 2007 -PhilipHazel -PH -University of Cambridge Computing Service -
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
+ +.fulldate + +EximMaintainers +EM - 4.68 - 23 August 2007 - PH + +.version + + +.fulldate + + EM -2007University of Cambridge + +.copyyear + University of Cambridge .literal off @@ -367,9 +374,11 @@ 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. +This edition of the Exim specification applies to version &version() of Exim. Substantive changes from the &previousversion; edition are marked in some renditions of the document; this paragraph is so marked if the rendition is capable of showing a change indicator. @@ -430,8 +439,6 @@ 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 @@ -456,12 +463,12 @@ Squared, formerly Planet Online Ltd, whose support I gratefully acknowledge. .cindex "FAQ" 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 &new("(&url(http://wiki.exim.org))"), +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 &new("&url(http://bugs.exim.org)"). 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. @@ -472,10 +479,10 @@ first to check that you are not duplicating a previous entry. 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 You can subscribe to these lists, change your existing subscriptions, and view @@ -500,8 +507,8 @@ 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 &new("can be emailed to &'bugs@exim.org'& or reported -via the Bugzilla (&url(http://bugs.exim.org)).") However, if you are unsure +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. @@ -537,10 +544,23 @@ 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 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 &_nigel-pubkey.asc_&. The signatures for the tar bundles are -in: +.new +The distributions will be PGP signed by an individual key of the Release +Coordinator. This key will have a uid containing an email address in the +&'exim.org'& domain and will have signatures from other people, including +other Exim maintainers. We expect that the key will be in the "strong set" of +PGP keys. There should be a trust path to that key from Nigel Metheringham's +PGP key, a version of which can be found in the release directory in the file +&_nigel-pubkey.asc_&. All keys used will be available in public keyserver pools, +such as &'pool.sks-keyservers.net'&. + +At time of last update, releases were being made by Phil Pennock and signed with +key &'0x403043153903637F'&, although that key is expected to be replaced in 2013. +A trust path from Nigel's key to Phil's can be observed at +&url(https://www.security.spodhuis.org/exim-trustpath). +.wen + +The signatures for the tar bundles are in: .display &_exim-n.nn.tar.gz.asc_& &_exim-n.nn.tar.bz2.asc_& @@ -726,15 +746,15 @@ the Exim documentation, &"spool"& is always used in the first sense. .cindex "incorporated code" .cindex "regular expressions" "library" .cindex "PCRE" +.cindex "OpenDMARC" 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 to a cut down version of PCRE -used to be distributed in the directory &_src/pcre_&. However, this is -no longer the case and you will need to use a system PCRE library or -obtain and install the full version of the library from +© 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" @@ -851,6 +871,14 @@ ARISING OUT OF OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE. .endblockquote +.next +.cindex "opendmarc" "acknowledgment" +The DMARC implementation uses the OpenDMARC library which is Copyrighted by +The Trusted Domain Project. Portions of Exim source which use OpenDMARC +derived code are indicated in the respective source files. The full OpenDMARC +license is provided in the LICENSE.opendmarc file contained in the distributed +source code. + .next Many people have contributed code fragments, some large, some small, that were not covered by any specific licence requirements. It is assumed that the @@ -1353,6 +1381,8 @@ Setting the &%verify%& option actually sets two options, &%verify_sender%& and &%verify_recipient%&, which independently control the use of the router for sender and recipient verification. You can set these options directly if you want a router to be used for only one type of verification. +Note that cutthrough delivery is classed as a recipient verification +for this purpose. .next If the &%address_test%& option is set false, the router is skipped when Exim is run with the &%-bt%& option to test an address routing. This can be helpful @@ -1362,6 +1392,7 @@ having to simulate the effect of the scanner. .next Routers can be designated for use only when verifying an address, as opposed to routing it for delivery. The &%verify_only%& option controls this. +Again, cutthrough delibery counts as a verification. .next Individual routers can be explicitly skipped when running the routers to check an address given in the SMTP EXPN command (see the &%expn%& option). @@ -1548,7 +1579,6 @@ 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 @@ -1558,7 +1588,6 @@ one connection. - .section "Permanent delivery failure" "SECID21" .cindex "delivery" "permanent failure" .cindex "bounce message" "when generated" @@ -1609,7 +1638,7 @@ for only a short time (see &%timeout_frozen_after%& and .section "Unpacking" "SECID23" Exim is distributed as a gzipped or bzipped tar file which, when unpacked, creates a directory with the name of the current release (for example, -&_exim-&version;_&) into which the following files are placed: +&_exim-&version()_&) into which the following files are placed: .table2 140pt .irow &_ACKNOWLEDGMENTS_& "contains some acknowledgments" @@ -1654,17 +1683,20 @@ architecture and operating system for itself, but the defaults can be overridden if necessary. -.section "PCRE library" "SECTdb" +.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 set the PCRE_LIBS -and INCLUDE directives appropriately. If your operating system has no +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/). .section "DBM libraries" "SECTdb" .cindex "DBM libraries" "discussion of" @@ -1875,6 +1907,12 @@ SUPPORT_TLS=yes TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto TLS_INCLUDE=-I/usr/local/openssl/include/ .endd +.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 .cindex "USE_GNUTLS" If GnuTLS is installed, you should set .code @@ -1890,6 +1928,14 @@ USE_GNUTLS=yes TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt TLS_INCLUDE=-I/usr/gnu/include .endd +.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 + 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 &<>&. @@ -1898,8 +1944,11 @@ 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 @@ -1914,18 +1963,20 @@ 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 +&_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 @@ -1945,6 +1996,36 @@ 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 @@ -2082,6 +2163,26 @@ 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. +.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 + .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, @@ -2225,16 +2326,15 @@ 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. For the utility programs, old versions are renamed by adding the suffix &_.O_& to their names. The Exim binary itself, however, is handled differently. It is installed under a name that includes the version number and the compile number, -for example &_exim-&version;-1_&. The script then arranges for a symbolic link +for example &_exim-&version()-1_&. The script then arranges for a symbolic link called &_exim_& to point to the binary. If you are updating a previous version of Exim, the script takes care to ensure that the name &_exim_& is never absent from the directory (as seen by other processes). @@ -2609,6 +2709,20 @@ 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. + +.new +.vitem &%-Ac%& &&& + &%-Am%& +.oindex "&%-Ac%&" +.oindex "&%-Am%&" +These options are used by Sendmail for selecting configuration files and are +ignored by Exim. +.wen + .vitem &%-B%&<&'type'&> .oindex "&%-B%&" .cindex "8-bit characters" @@ -2868,11 +2982,39 @@ use the &'exim_dbmbuild'& utility, or some other means, to rebuild alias files if this is required. If the &%bi_command%& option is not set, calling Exim with &%-bi%& is a no-op. +.new +. // Keep :help first, then the rest in alphabetical order +.vitem &%-bI:help%& +.oindex "&%-bI:help%&" +.cindex "querying exim information" +We shall provide various options starting &`-bI:`& for querying Exim for +information. The output of many of these will be intended for machine +consumption. This one is not. The &%-bI:help%& option asks Exim for a +synopsis of supported options beginning &`-bI:`&. Use of any of these +options shall cause Exim to exit after producing the requested output. + +.vitem &%-bI:dscp%& +.oindex "&%-bI:dscp%&" +.cindex "DSCP" "values" +This option causes Exim to emit an alphabetically sorted list of all +recognised DSCP names. + +.vitem &%-bI:sieve%& +.oindex "&%-bI:sieve%&" +.cindex "Sieve filter" "capabilities" +This option causes Exim to emit an alphabetically sorted list of all supported +Sieve protocol extensions on stdout, one per line. This is anticipated to be +useful for ManageSieve (RFC 5804) implementations, in providing that protocol's +&`SIEVE`& capability response line. As the precise list may depend upon +compile-time build options, which this option will adapt to, this is the only +way to guarantee a correct response. +.wen + .vitem &%-bm%& .oindex "&%-bm%&" .cindex "local message reception" This option runs an Exim receiving process that accepts an incoming, -locally-generated message on the current input. The recipients are given as the +locally-generated message on the standard input. The recipients are given as the command arguments (except when &%-t%& is also present &-- see below). Each argument can be a comma-separated list of RFC 2822 addresses. This is the default option for selecting the overall action of an Exim call; it is assumed @@ -2914,6 +3056,26 @@ 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" @@ -2961,6 +3123,12 @@ configuration file is output. If a list of configuration files was supplied, the value that is output here is the name of the file that was actually used. +.new +.cindex "options" "hiding name of" +If the &%-n%& flag is given, then for most modes of &%-bP%& operation the +name will not be output. +.wen + .cindex "daemon" "process id (pid)" .cindex "pid (process id)" "of daemon" If &%log_file_path%& or &%pid_file_path%& are given, the names of the @@ -2978,6 +3146,7 @@ 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: @@ -2991,6 +3160,11 @@ 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%&" @@ -3219,7 +3393,7 @@ 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. @@ -3288,6 +3462,23 @@ 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" @@ -3300,25 +3491,23 @@ 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 @@ -3339,6 +3528,7 @@ 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" @@ -3348,6 +3538,14 @@ 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 @@ -3364,6 +3562,7 @@ 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" @@ -3532,8 +3731,19 @@ if &%-f%& is also present, it overrides &"From&~"&. .vitem &%-G%& .oindex "&%-G%&" -.cindex "Sendmail compatibility" "&%-G%& option ignored" -This is a Sendmail option which is ignored by Exim. +.cindex "submission fixups, suppressing (command-line)" +.new +This option is equivalent to an ACL applying: +.code +control = suppress_local_fixups +.endd +for every message received. Note that Sendmail will complain about such +bad formatting, where Exim silently just does not fix it up. This may change +in future. + +As this affects audit information, the caller must be a trusted user to use +this option. +.wen .vitem &%-h%&&~<&'number'&> .oindex "&%-h%&" @@ -3551,6 +3761,19 @@ line by itself should not terminate an incoming, non-SMTP message. I can find no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'& command in Solaris 2.4 uses it. See also &%-ti%&. +.new +.vitem &%-L%&&~<&'tag'&> +.oindex "&%-L%&" +.cindex "syslog" "process name; set with flag" +This option is equivalent to setting &%syslog_processname%& in the config +file and setting &%log_file_path%& to &`syslog`&. +Its use is restricted to administrators. The configuration file has to be +read and parsed, to determine access rights, before this is set and takes +effect, so early configuration file errors will not honour this flag. + +The tag should not be longer than 32 characters. +.wen + .vitem &%-M%&&~<&'message&~id'&>&~<&'message&~id'&>&~... .oindex "&%-M%&" .cindex "forcing delivery" @@ -3744,7 +3967,7 @@ 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 2922 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. @@ -3791,9 +4014,9 @@ for that message. .vitem &%-n%& .oindex "&%-n%&" -.cindex "Sendmail compatibility" "&%-n%& option ignored" -This option is interpreted by Sendmail to mean &"no aliasing"&. It is ignored -by Exim. +This option is interpreted by Sendmail to mean &"no aliasing"&. +For normal modes of operation, it is ignored by Exim. +When combined with &%-bP%& it suppresses the name of an option from being output. .vitem &%-O%&&~<&'data'&> .oindex "&%-O%&" @@ -3907,8 +4130,8 @@ message. Provided this error message is successfully sent, the Exim receiving process exits with a return code of zero. If not, the return code is 2 if the problem -is that the original message has no recipients, or 1 any other error. This is -the default &%-oe%&&'x'& option if Exim is called as &'rmail'&. +is that the original message has no recipients, or 1 for any other error. +This is the default &%-oe%&&'x'& option if Exim is called as &'rmail'&. .vitem &%-oem%& .oindex "&%-oem%&" @@ -4121,7 +4344,7 @@ For compatibility with Sendmail, this option is equivalent to It sets the incoming protocol and host name (for trusted callers). The host name and its colon can be omitted when only the protocol is to be set. Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer -to embedded Perl. It is therefore impossible to set a protocol value of &`p`& +to embedded Perl. It is therefore impossible to set a protocol value of &`d`& or &`s`& using this option (but that does not seem a real limitation). .vitem &%-q%& @@ -4328,7 +4551,7 @@ has &'f'& or &'ff'& in its flags, the associated action is taken. .vitem &%-Tqt%&&~<&'times'&> .oindex "&%-Tqt%&" -This an option that is exclusively for use by the Exim testing suite. It is not +This is an option that is exclusively for use by the Exim testing suite. It is not recognized when Exim is run normally. It allows for the setting up of explicit &"queue times"& so that various warning/retry features can be tested. @@ -4412,6 +4635,13 @@ AIX uses &%-x%& for a private purpose (&"mail from a local mail program has National Language Support extended characters in the body of the mail item"&). It sets &%-x%& when calling the MTA from its &%mail%& command. Exim ignores this option. + +.new +.vitem &%-X%&&~<&'logfile'&> +.oindex "&%-X%&" +This option is interpreted by Sendmail to cause debug information to be sent +to the named file. It is ignored by Exim. +.wen .endlist .ecindex IIDclo1 @@ -4470,17 +4700,21 @@ 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 @@ -4496,21 +4730,24 @@ 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 @@ -4525,6 +4762,16 @@ 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 @@ -4721,7 +4968,7 @@ 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 @@ -5158,7 +5405,7 @@ it is unset, Exim uses the &[uname()]& system function to obtain the host name. The first three non-comment configuration lines are as follows: .code -domainlist local_domains = @ +domainlist local_domains = @ domainlist relay_to_domains = hostlist relay_from_hosts = 127.0.0.1 .endd @@ -5500,7 +5747,7 @@ examples described in &<>&. This means that no client can in fact authenticate until you complete the authenticator definitions. .code require message = relay not permitted - domains = +local_domains : +relay_domains + domains = +local_domains : +relay_to_domains .endd This statement rejects the address if its domain is neither a local domain nor one of the domains for which this host is a relay. @@ -5862,7 +6109,7 @@ The example PLAIN authenticator looks like this: # server_set_id = $auth2 # server_prompts = : # server_condition = Authentication is not yet configured -# server_advertise_condition = ${if def:tls_cipher } +# server_advertise_condition = ${if def:tls_in_cipher } .endd And the example LOGIN authenticator looks like this: .code @@ -5871,7 +6118,7 @@ And the example LOGIN authenticator looks like this: # server_set_id = $auth1 # server_prompts = <| Username: | Password: # server_condition = Authentication is not yet configured -# server_advertise_condition = ${if def:tls_cipher } +# server_advertise_condition = ${if def:tls_in_cipher } .endd The &%server_set_id%& option makes Exim remember the authenticated username @@ -5881,12 +6128,16 @@ that it implements the details of the specific authentication mechanism, i.e. PLAIN or LOGIN. The &%server_advertise_condition%& setting controls when Exim offers authentication to clients; in the examples, this is only when TLS or SSL has been started, so to enable the authenticators you also -need to add support for TLS as described in &<>&. +need to add support for TLS as described in section &<>&. The &%server_condition%& setting defines how to verify that the username and 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 &<>&. +expression like one of the examples in chapter &<>&. + +Beware that the sequence of the parameters to PLAIN and LOGIN differ; the +usercode and password are in different positions. +Chapter &<>& covers both. .ecindex IIDconfiwal @@ -5907,13 +6158,11 @@ 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 @@ -5952,47 +6201,6 @@ $ 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 &$2$&. - - - - - - . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -6140,12 +6348,23 @@ 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.) .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. +.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 @@ -6174,7 +6393,7 @@ 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 @@ -6637,8 +6856,8 @@ 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 +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: @@ -6666,6 +6885,21 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. +.cindex "TXT record" "in &(dnsdb)& lookup" +.cindex "SPF record" "in &(dnsdb)& lookup" +For TXT records with multiple items of data, only the first item is returned, +unless a separator for them is specified using a comma after the separator +character followed immediately by the TXT record item separator. To concatenate +items without a separator, use a semicolon instead. For SPF records the +default behaviour is to concatenate multiple items without using a separator. +.code +${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 @@ -6713,6 +6947,14 @@ has two space-separated fields: an authorization code and a target host name. The authorization code can be &"Y"& for yes, &"N"& for no, &"X"& for explicit authorization required but absent, or &"?"& for unknown. +.cindex "A+" "in &(dnsdb)& lookup" +The pseudo-type A+ performs an A6 lookup (if configured) followed by an AAAA +and then an A lookup. All results are returned; defer processing +(see below) is handled separately for each lookup. Example: +.code +${lookup dnsdb {>; a+=$sender_helo_name}} +.endd + .section "Multiple dnsdb lookups" "SECID67" In the previous sections, &(dnsdb)& lookups for a single domain are described. @@ -6810,6 +7052,10 @@ 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" @@ -7156,9 +7402,9 @@ 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. -&new("(For MySQL and PostgreSQL only, the global option need not be set if all +(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 +&<>&.) 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: @@ -7218,13 +7464,13 @@ mysql_servers = slave1/db/name/pw:\ .endd In an updating lookup, you could then write: .code -${lookup mysql{servers=master; UPDATE ...} +${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 -${lookup pgsql{servers=master/db/name/pw; UPDATE ...} +${lookup pgsql{servers=master/db/name/pw; UPDATE ...} } .endd @@ -7283,7 +7529,7 @@ ${lookup sqlite {/some/thing/sqlitedb \ .endd In a list, the syntax is similar. For example: .code -domainlist relay_domains = sqlite;/some/thing/sqlitedb \ +domainlist relay_to_domains = sqlite;/some/thing/sqlitedb \ select * from relays where ip='$sender_host_address'; .endd The only character affected by the &%quote_sqlite%& operator is a single @@ -7365,13 +7611,13 @@ subject is not in the set. If the end of the list is reached without the subject having matched any of the patterns, it is in the set if the last item was a negative one, but not if it was a positive one. For example, the list in .code -domainlist relay_domains = !a.b.c : *.b.c +domainlist relay_to_domains = !a.b.c : *.b.c .endd matches any domain ending in &'.b.c'& except for &'a.b.c'&. Domains that match neither &'a.b.c'& nor &'*.b.c'& do not match, because the last item in the list is positive. However, if the setting were .code -domainlist relay_domains = !a.b.c +domainlist relay_to_domains = !a.b.c .endd then all domains other than &'a.b.c'& would match because the last item in the list is negative. In other words, a list that ends with a negative item behaves @@ -7475,7 +7721,7 @@ the words &%domainlist%&, &%hostlist%&, &%addresslist%&, or &%localpartlist%&, respectively. Then there follows the name that you are defining, followed by an equals sign and the list itself. For example: .code -hostlist relay_hosts = 192.168.23.0/24 : my.friend.example +hostlist relay_from_hosts = 192.168.23.0/24 : my.friend.example addresslist bad_senders = cdb;/etc/badsenders .endd A named list may refer to other named lists: @@ -7719,7 +7965,7 @@ 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:$domain}'; .endd In most cases, the data that is looked up is not used (so for an SQL query, for example, it doesn't matter what field you select). Exim is interested only in @@ -7942,7 +8188,7 @@ case the IP address is used on its own. There are several types of pattern that require Exim to know the name of the remote host. These are either wildcard patterns or lookups by name. (If a complete hostname is given without any wildcarding, it is used to find an IP -address to match against, as described in the section &<>& +address to match against, as described in section &<>& above.) If the remote host name is not already known when Exim encounters one of these @@ -8111,7 +8357,7 @@ use masked IP addresses in database queries, you can use the &%mask%& expansion operator. If the query contains a reference to &$sender_host_name$&, Exim automatically -looks up the host name if has not already done so. (See section +looks up the host name if it has not already done so. (See section &<>& for comments on finding host names.) Historical note: prior to release 4.30, Exim would always attempt to find a @@ -8311,7 +8557,7 @@ but the separating colon must still be included at line breaks. White space surrounding the colons is ignored. For example: .code aol.com: spammer1 : spammer2 : ^[0-9]+$ : -spammer3 : spammer4 + spammer3 : spammer4 .endd As in all colon-separated lists in Exim, a colon can be included in an item by doubling. @@ -8423,6 +8669,13 @@ 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" @@ -8549,6 +8802,23 @@ string easier to understand. This item inserts &"basic"& header lines. It is described with the &%header%& expansion item below. + +.vitem "&*${acl{*&<&'name'&>&*}{*&<&'arg'&>&*}...}*&" +.cindex "expansion" "calling an acl" +.cindex "&%acl%&" "call from expansion" +The name and zero to nine argument strings are first expanded separately. The expanded +arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order. +Any unused are made empty. The variable &$acl_narg$& is set to the number of +arguments. The named ACL (see chapter &<>&) is called +and may use the variables; if another acl expansion is used the values +are restored after it returns. If the ACL sets +a value using a "message =" modifier and returns accept or deny, the value becomes +the result of the expansion. +If no message is set and the ACL returns accept or deny +the expansion result is an empty string. +If the ACL returns defer the result is a forced-fail. Otherwise the expansion fails. + + .vitem "&*${dlfunc{*&<&'file'&>&*}{*&<&'function'&>&*}{*&<&'arg'&>&*}&&& {*&<&'arg'&>&*}...}*&" .cindex &%dlfunc%& @@ -9179,6 +9449,20 @@ can be the word &"fail"& (not in braces) to force expansion failure if the command does not succeed. If both strings are omitted, the result is contents of the standard output/error on success, and nothing on failure. +.vindex "&$run_in_acl$&" +The standard output/error of the command is put in the variable &$value$&. +In this ACL example, the output of a command is logged for the admin to +troubleshoot: +.code +warn condition = ${run{/usr/bin/id}{yes}{no}} + log_message = Output of id: $value +.endd +If the command requires shell idioms, such as the > redirect operator, the +shell must be invoked directly, such as with: +.code +${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}} +.endd + .vindex "&$runrc$&" The return code from the command is put in the variable &$runrc$&, and this remains set afterwards, so in a filter file you can do things like this: @@ -9358,6 +9642,7 @@ environments where Exim uses base 36 instead of base 62 for its message identifiers, base-36 digits. The number is converted to decimal and output as a string. + .vitem &*${domain:*&<&'string'&>&*}*& .cindex "domain" "extraction" .cindex "expansion" "domain extraction" @@ -9402,9 +9687,10 @@ decimal, even if they start with a leading zero; hexadecimal numbers are not permitted. This can be useful when processing numbers extracted from dates or times, which often do have leading zeros. -A number may be followed by &"K"& or &"M"& to multiply it by 1024 or 1024*1024, +A number may be followed by &"K"&, &"M"& or &"G"& to multiply it by 1024, 1024*1024 +or 1024*1024*1024, respectively. Negative numbers are supported. The result of the computation is -a decimal representation of the answer (without &"K"& or &"M"&). For example: +a decimal representation of the answer (without &"K"&, &"M"& or &"G"&). For example: .display &`${eval:1+1} `& yields 2 @@ -9491,6 +9777,16 @@ This operator converts a hex string into one that is base64 encoded. This can be useful for processing the output of the MD5 and SHA-1 hashing functions. + +.vitem &*${hexquote:*&<&'string'&>&*}*& +.cindex "quoting" "hex-encoded unprintable characters" +.cindex "&%hexquote%& expansion item" +This operator converts non-printable characters in a string into a hex +escape form. Byte values between 33 (!) and 126 (~) inclusive are left +as is, and other byte values are converted to &`\xNN`&, for example a +byt value 127 is converted to &`\x7f`&. + + .vitem &*${lc:*&<&'string'&>&*}*& .cindex "case forcing in strings" .cindex "string" "case forcing" @@ -9516,6 +9812,25 @@ See the description of the general &%length%& item above for details. Note that when &%length%& is used as an operator. +.vitem &*${listcount:*&<&'string'&>&*}*& +.cindex "expansion" "list item count" +.cindex "list" "item count" +.cindex "list" "count of items" +.cindex "&%listcount%& expansion item" +The string is interpreted as a list and the number of items is returned. + + +.vitem &*${listnamed:*&<&'name'&>&*}*&&~and&~&*${list_*&<&'type'&>&*name*&>&*}*& +.cindex "expansion" "named list" +.cindex "&%listnamed%& expansion item" +The name is interpreted as a named list and the content of the list is returned, +expanding any referenced lists, re-quoting as needed for colon-separation. +If the optional type if given it must be one of "a", "d", "h" or "l" +and selects address-, domain-, host- or localpart- lists to search among respectively. +Otherwise all types are searched in an undefined order and the first +matching list is returned. + + .vitem &*${local_part:*&<&'string'&>&*}*& .cindex "expansion" "local part extraction" .cindex "&%local_part%& expansion item" @@ -9617,6 +9932,36 @@ For single-key lookup types, no quoting is ever necessary and this operator yields an unchanged string. +.vitem &*${randint:*&<&'n'&>&*}*& +.cindex "random number" +This operator returns a somewhat random number which is less than the +supplied number and is at least 0. The quality of this randomness depends +on how Exim was built; the values are not suitable for keying material. +If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. +If Exim is linked against GnuTLS then gnutls_rnd(GNUTLS_RND_NONCE) is used, +for versions of GnuTLS with that function. +Otherwise, the implementation may be arc4random(), random() seeded by +srandomdev() or srandom(), or a custom implementation even weaker than +random(). + + +.vitem &*${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:192.0.2.127} +.endd +returns +.code +4.2.0.192 +f.7.2.0.0.0.0.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" @@ -9773,11 +10118,62 @@ ${if >{$message_size}{10M} ... .endd Note that the general negation operator provides for inequality testing. The two strings must take the form of optionally signed decimal integers, -optionally followed by one of the letters &"K"& or &"M"& (in either upper or -lower case), signifying multiplication by 1024 or 1024*1024, respectively. +optionally followed by one of the letters &"K"&, &"M"& or &"G"& (in either upper or +lower case), signifying multiplication by 1024, 1024*1024 or 1024*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 &*acl&~{{*&<&'name'&>&*}{*&<&'arg1'&>&*}&&& + {*&<&'arg2'&>&*}...}*& +.cindex "expansion" "calling an acl" +.cindex "&%acl%&" "expansion condition" +The name and zero to nine argument strings are first expanded separately. The expanded +arguments are assigned to the variables &$acl_arg1$& to &$acl_arg9$& in order. +Any unused are made empty. The variable &$acl_narg$& is set to the number of +arguments. The named ACL (see chapter &<>&) is called +and may use the variables; if another acl expansion is used the values +are restored after it returns. If the ACL sets +a value using a "message =" modifier the variable $value becomes +the result of the expansion, otherwise it is empty. +If the ACL returns accept the condition is true; if deny, false. +If the ACL returns defer the result is a forced-fail. + +.vitem &*bool&~{*&<&'string'&>&*}*& +.cindex "expansion" "boolean parsing" +.cindex "&%bool%& expansion condition" +This condition turns a string holding a true or false representation into +a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"& +(case-insensitively); also positive integer numbers map to true if non-zero, +false if zero. +An empty string is treated as false. +Leading and trailing whitespace is ignored; +thus a string consisting only of whitespace is false. +All other string values will result in expansion failure. + +When combined with ACL variables, this expansion condition will let you +make decisions in one place and act on those decisions in another place. +For example: +.code +${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" @@ -9941,6 +10337,8 @@ ${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}} The value of &$item$& is saved and restored while &*forany*& or &*forall*& is being processed, to enable these expansion items to be nested. +To scan a named list, expand it with the &*listnamed*& operator. + .vitem &*ge&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& &*gei&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -9964,6 +10362,23 @@ 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. +.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 + .vitem &*isip&~{*&<&'string'&>&*}*& &&& &*isip4&~{*&<&'string'&>&*}*& &&& &*isip6&~{*&<&'string'&>&*}*& @@ -10076,7 +10491,7 @@ See &*match_local_part*&. .cindex "&%match_ip%& expansion condition" 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: .code ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}} @@ -10123,6 +10538,9 @@ just as easy to use the fact that a lookup is itself a condition, and write: .endd .endlist ilist +Note that <&'string2'&> is not itself subject to string expansion, unless +Exim was built with the EXPAND_LISTMATCH_RHS option. + Consult section &<>& for further details of these patterns. .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -10150,6 +10568,9 @@ 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. +Note that <&'string2'&> is not itself subject to string expansion, unless +Exim was built with the EXPAND_LISTMATCH_RHS option. + &*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 @@ -10229,6 +10650,10 @@ 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:$auth3}} +.endd .vitem &*queue_running*& .cindex "queue runner" "detecting when delivering from" .cindex "expansion" "queue runner test" @@ -10457,6 +10882,16 @@ the value of &$authenticated_id$& is normally the login name of the calling process. However, a trusted user can override this by means of the &%-oMai%& command line option. +.vitem &$authenticated_fail_id$& +.cindex "authentication" "fail" "id" +.vindex "&$authenticated_fail_id$&" +When an authentication attempt fails, the variable &$authenticated_fail_id$& +will contain the failed authentication id. If more than one authentication +id is attempted, it will contain only the last one. The variable is +available for processing in the ACL's, generally the quit or notquit ACL. +A message to a local recipient could still be accepted without requiring +authentication, which means this variable could also be visible in all of +the ACL's as well. @@ -10491,6 +10926,13 @@ is empty and &$authentication_failed$& is set to &"1"&). Failure includes any negative response to an AUTH command, including (for example) an attempt to use an undefined mechanism. +.vitem &$av_failed$& +.cindex "content scanning" "AV scanner failure" +This variable is available when Exim is compiled with the content-scanning +extension. It is set to &"0"& by default, but will be set to &"1"& if any +problem occurs with the virus scanner (specified by &%av_scanner%&) during +the ACL malware condition. + .vitem &$body_linecount$& .cindex "message body" "line count" .cindex "body of message" "line count" @@ -10504,7 +10946,7 @@ number of lines in the message's body. See also &$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$&" @@ -10663,6 +11105,12 @@ inserting the message header line with the given name. Note that the name must be terminated by colon or white space, because it may contain a wide variety of characters. Note also that braces must &'not'& be used. +.vitem &$headers_added$& +.vindex "&$headers_added$&" +Within an ACL this variable contains the headers added so far by +the ACL modifier add_header (section &<>&). +The headers are a newline-separated list. + .vitem &$home$& .vindex "&$home$&" When the &%check_local_user%& option is set for a router, the user's home @@ -10762,7 +11210,7 @@ This is an obsolete name for &$received_port$&. .vitem &$item$& .vindex "&$item$&" This variable is used during the expansion of &*forall*& and &*forany*& -conditions (see section &<>&), and &*filter*&, &*man*&, and +conditions (see section &<>&), and &*filter*&, &*map*&, and &*reduce*& items (see section &<>&). In other circumstances, it is empty. @@ -10992,8 +11440,15 @@ number of lines received. Before delivery happens (that is, before filters, routers, and transports run) the count is increased to include the &'Received:'& header line that Exim standardly adds, and also any other header lines that are added by ACLs. The blank line that separates the message header -from the body is not counted. Here is an example of the use of this variable in -a DATA ACL: +from the body is not counted. + +As with the special case of &$message_size$&, during the expansion of the +appendfile transport's maildir_tag option in maildir format, the value of +&$message_linecount$& is the precise size of the number of newlines in the +file that has been written (minus one for the blank line between the +header and the body). + +Here is an example of the use of this variable in a DATA ACL: .code deny message = Too many lines in message header condition = \ @@ -11016,7 +11471,7 @@ precise size of the file that has been written. See also &$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$& contains the size supplied on the MAIL command, or -1 if no size was given. The value may not, of course, be truthful. @@ -11326,6 +11781,12 @@ envelope sender. .vindex "&$return_size_limit$&" This is an obsolete name for &$bounce_return_size_limit$&. +.vitem &$router_name$& +.cindex "router" "name" +.cindex "name" "of router" +.vindex "&$router_name$&" +During the running of a router this variable contains its name. + .vitem &$runrc$& .cindex "return code" "from &%run%& expansion" .vindex "&$runrc$&" @@ -11417,6 +11878,31 @@ driver that successfully authenticated the client from which the message was received. It is empty if there was no successful authentication. See also &$authenticated_id$&. +.new +.vitem &$sender_host_dnssec$& +.vindex "&$sender_host_dnssec$&" +If &$sender_host_name$& has been populated (by reference, &%hosts_lookup%& or +otherwise) then this boolean will have been set true if, and only if, the +resolver library states that the reverse DNS was authenticated data. At all +other times, this variable is false. + +It is likely that you will need to coerce DNSSEC support on in the resolver +library, by setting: +.code +dns_use_dnssec = 1 +.endd + +Exim does not perform DNSSEC validation itself, instead leaving that to a +validating resolver (eg, unbound, or bind with suitable configuration). + +Exim does not (currently) check to see if the forward DNS was also secured +with DNSSEC, only the reverse DNS. + +If you have changed &%host_lookup_order%& so that &`bydns`& is not the first +mechanism in the list, then this variable will be false. +.wen + + .vitem &$sender_host_name$& .vindex "&$sender_host_name$&" When a message is received from a remote host, this variable contains the @@ -11615,12 +12101,43 @@ command in a filter file. Its use is explained in the description of that command, which can be found in the separate document entitled &'Exim's interfaces to mail filtering'&. -.vitem &$tls_certificate_verified$& -.vindex "&$tls_certificate_verified$&" +.vitem &$tls_in_bits$& +.vindex "&$tls_in_bits$&" +Contains an approximation of the TLS cipher's bit-strength +on the inbound connection; the meaning of +this depends upon the TLS implementation used. +If TLS has not been negotiated, the value will be 0. +The value of this is automatically fed into the Cyrus SASL authenticator +when acting as a server, to specify the "external SSF" (a SASL term). + +The deprecated &$tls_bits$& variable refers to the inbound side +except when used in the context of an outbound SMTP delivery, when it refers to +the outbound. + +.vitem &$tls_out_bits$& +.vindex "&$tls_out_bits$&" +Contains an approximation of the TLS cipher's bit-strength +on an outbound SMTP connection; the meaning of +this depends upon the TLS implementation used. +If TLS has not been negotiated, the value will be 0. + +.vitem &$tls_in_certificate_verified$& +.vindex "&$tls_in_certificate_verified$&" This variable is set to &"1"& if a TLS certificate was verified when the message was received, and &"0"& otherwise. -.vitem &$tls_cipher$& +The deprecated &$tls_certificate_verfied$& variable refers to the inbound side +except when used in the context of an outbound SMTP delivery, when it refers to +the outbound. + +.vitem &$tls_out_certificate_verified$& +.vindex "&$tls_out_certificate_verified$&" +This variable is set to &"1"& if a TLS certificate was verified when an +outbound SMTP connection was made, +and &"0"& otherwise. + +.vitem &$tls_in_cipher$& +.vindex "&$tls_in_cipher$&" .vindex "&$tls_cipher$&" When a message is received from a remote host over an encrypted SMTP connection, this variable is set to the cipher suite that was negotiated, for @@ -11629,21 +12146,59 @@ received over unencrypted connections, the variable is empty. Testing &$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$& is cleared before any outgoing SMTP connection is made, +The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception, +but in the context of an outward SMTP delivery taking place via the &(smtp)& transport +becomes the same as &$tls_out_cipher$&. + +.vitem &$tls_out_cipher$& +.vindex "&$tls_out_cipher$&" +This variable is +cleared before any outgoing SMTP connection is made, and then set to the outgoing cipher suite if one is negotiated. See chapter &<>& for details of TLS support and chapter &<>& for details of the &(smtp)& transport. -.vitem &$tls_peerdn$& +.vitem &$tls_in_peerdn$& +.vindex "&$tls_in_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$& during subsequent processing. &new("Like &$tls_cipher$&, the -value is retained during message delivery, except during outbound SMTP -deliveries.") +&$tls_in_peerdn$& during subsequent processing. + +The deprecated &$tls_peerdn$& variable refers to the inbound side +except when used in the context of an outbound SMTP delivery, when it refers to +the outbound. + +.vitem &$tls_out_peerdn$& +.vindex "&$tls_out_peerdn$&" +When a message is being delivered to a remote host over an encrypted SMTP +connection, and Exim is configured to request a certificate from the server, +the value of the Distinguished Name of the certificate is made available in the +&$tls_out_peerdn$& during subsequent processing. + +.vitem &$tls_in_sni$& +.vindex "&$tls_in_sni$&" +.vindex "&$tls_sni$&" +.cindex "TLS" "Server Name Indication" +When a TLS session is being established, if the client sends the Server +Name Indication extension, the value will be placed in this variable. +If the variable appears in &%tls_certificate%& then this option and +some others, described in &<>&, +will be re-expanded early in the TLS session, to permit +a different certificate to be presented (and optionally a different key to be +used) to the client, based upon the value of the SNI extension. + +The deprecated &$tls_sni$& variable refers to the inbound side +except when used in the context of an outbound SMTP delivery, when it refers to +the outbound. + +.vitem &$tls_out_sni$& +.vindex "&$tls_out_sni$&" +.cindex "TLS" "Server Name Indication" +During outbound +SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on +the transport. .vitem &$tod_bsdinbox$& .vindex "&$tod_bsdinbox$&" @@ -11654,6 +12209,10 @@ files, for example: Thu Oct 17 17:14:09 1995. .vindex "&$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$&" A full version of the time and date, for example: Wed, 16 Oct 1995 09:51:40 @@ -11682,6 +12241,12 @@ This variable contains the numerical value of the local timezone, for example: This variable contains the UTC date and time in &"Zulu"& format, as specified by ISO 8601, for example: 20030221154023Z. +.vitem &$transport_name$& +.cindex "transport" "name" +.cindex "name" "of transport" +.vindex "&$transport_name$&" +During the running of a transport, this variable contains its name. + .vitem &$value$& .vindex "&$value$&" This variable contains the result of an expansion lookup, extraction operation, @@ -12093,7 +12658,7 @@ local_interfaces = 0.0.0.0 : 127.0.0.1.26 .endd To specify listening on the default port on specific interfaces only: .code -local_interfaces = 192.168.34.67 : 192.168.34.67 +local_interfaces = 10.0.0.67 : 192.168.34.67 .endd &*Warning*&: Such a setting excludes listening on the loopback interfaces. @@ -12186,7 +12751,7 @@ listed in more than one group. .row &%disable_ipv6%& "do no IPv6 processing" .row &%keep_malformed%& "for broken files &-- should not happen" .row &%localhost_number%& "for unique message ids in clusters" -.row &new(&%message_body_newlines%&) "retain newlines in &$message_body$&" +.row &%message_body_newlines%& "retain newlines in &$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" @@ -12253,13 +12818,20 @@ listed in more than one group. .section "Data lookups" "SECID101" .table2 -.row &new(&%ibase_servers%&) "InterBase servers" +.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 &new(&%mysql_servers%&) "default MySQL servers" -.row &new(&%oracle_servers%&) "Oracle servers" -.row &new(&%pgsql_servers%&) "default PostgreSQL servers" +.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 @@ -12302,7 +12874,7 @@ 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 &new(&%queue_only_load_latch%&) "don't re-evaluate load for each message" +.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" @@ -12330,6 +12902,7 @@ 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" @@ -12381,12 +12954,13 @@ listed in more than one group. .section "TLS" "SECID108" .table2 -.row &%gnutls_require_kx%& "control GnuTLS key exchanges" -.row &%gnutls_require_mac%& "control GnuTLS MAC algorithms" -.row &%gnutls_require_protocols%& "control GnuTLS protocols" +.row &%gnutls_compat_mode%& "use GnuTLS compatibility mode" +.row &%gnutls_enable_pkcs11%& "allow GnuTLS to autoload PKCS11 modules" +.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" @@ -12531,13 +13105,15 @@ 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_dnssec%& "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 &new(&%queue_only_load_latch%&) "don't re-evaluate load for each message" +.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" @@ -12574,14 +13150,28 @@ See also the &'Policy controls'& section above. Those options that undergo string expansion before use are marked with †. -.option accept_8bitmime main boolean false +.option accept_8bitmime main boolean true .cindex "8BITMIME" .cindex "8-bit characters" +.cindex "log" "selectors" +.cindex "log" "8BITMIME" 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 + +To log received 8BITMIME status use +.code +log_selector = +8bitmime +.endd .option acl_not_smtp main string&!! unset .cindex "&ACL;" "for non-SMTP messages" @@ -12762,10 +13352,10 @@ If you want to advertise the availability of AUTH only when the connection is encrypted using TLS, you can make use of the fact that the value of this option is expanded, with a setting like this: .code -auth_advertise_hosts = ${if eq{$tls_cipher}{}{}{*}} +auth_advertise_hosts = ${if eq{$tls_in_cipher}{}{}{*}} .endd -.vindex "&$tls_cipher$&" -If &$tls_cipher$& is empty, the session is not encrypted, and the result of +.vindex "&$tls_in_cipher$&" +If &$tls_in_cipher$& is empty, the session is not encrypted, and the result of the expansion is empty, thus matching no hosts. Otherwise, the result of the expansion is *, which matches all hosts. @@ -12783,17 +13373,17 @@ 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 @@ -12896,7 +13486,7 @@ 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. @@ -13118,7 +13708,7 @@ 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. &new(Slashes) 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 @@ -13163,6 +13753,29 @@ to set in them. See &%dns_retrans%& above. +.new +.option dns_use_dnssec main integer -1 +.cindex "DNS" "resolver options" +.cindex "DNS" "DNSSEC" +If this option is set to a non-negative number then Exim will initialise the +DNS resolver library to either use or not use DNSSEC, overriding the system +default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. + +If the resolver library does not support DNSSEC then this option has no effect. +.wen + + +.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. + + .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 @@ -13371,17 +13984,22 @@ gecos_name = $1 See &%gecos_name%& above. -.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_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 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 &<>&. +.new +option gnutls_enable_pkcs11 main boolean unset +This option will let GnuTLS (2.12.0 or later) autoload PKCS11 modules with +the p11-kit configuration files in &_/etc/pkcs11/modules/_&. + +See +&url(http://www.gnutls.org/manual/gnutls.html#Smart-cards-and-HSMs) +for documentation. +.wen + .option headers_charset main string "see below" @@ -13454,10 +14072,10 @@ 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. @@ -13479,7 +14097,7 @@ 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" @@ -13535,8 +14153,8 @@ 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`& @@ -13658,6 +14276,46 @@ 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 @@ -13666,6 +14324,25 @@ 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 @@ -13939,6 +14616,18 @@ 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" @@ -13991,6 +14680,105 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. +.option openssl_options main "string list" "+no_sslv2" +.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. + +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. + +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 +&`safari_ecdhe_ecdsa_bug`& +.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 + +.new +As an aside, the &`safari_ecdhe_ecdsa_bug`& item is a misnomer and affects +all clients connecting using the MacOS SecureTransport TLS facility prior +to MacOS 10.8.4, including email clients. If you see old MacOS clients failing +to negotiate TLS then this option value might help, provided that your OpenSSL +release is new enough to contain this work-around. This may be a situation +where you have to upgrade OpenSSL to get buggy clients working. +.wen + + .option oracle_servers main "string list" unset .cindex "Oracle" "server list" This option provides a list of Oracle servers and associated connection data, @@ -14316,7 +15104,7 @@ received_header_text = Received: \ ${if def:sender_helo_name {(helo=$sender_helo_name)\n\t}}}}\ by $primary_hostname \ ${if def:received_protocol {with $received_protocol}} \ - ${if def:tls_cipher {($tls_cipher)\n\t}}\ + ${if def:tls_in_cipher {($tls_in_cipher)\n\t}}\ (Exim $version_number)\n\t\ ${if def:sender_address \ {(envelope-from <$sender_address>)\n\t}}\ @@ -14560,7 +15348,7 @@ live with. . Allow this long option name to split; give it unsplit as a fifth argument . for the automatic .oindex that is generated by .option. -.option "smtp_accept_max_per_ &~&~connection" main integer 1000 &&& +.option "smtp_accept_max_per_connection" main integer 1000 &&& smtp_accept_max_per_connection .cindex "SMTP" "limiting incoming message count" .cindex "limit" "messages per SMTP connection" @@ -15091,11 +15879,13 @@ 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, @@ -15103,8 +15893,7 @@ 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 @@ -15178,6 +15967,10 @@ 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. +If the option contains &$tls_out_sni$& 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. .option tls_crl main string&!! unset .cindex "TLS" "server certificate revocation list" @@ -15185,13 +15978,83 @@ 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. +See &<>& for discussion of when this option might be re-expanded. + + +.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. + +Note that the value passed to GnuTLS for *generating* a new prime may be a +little less than this figure, because GnuTLS is inexact and may produce a +larger prime than requested. + .option tls_dhparam main string&!! unset .cindex "TLS" "D-H parameters for server" -The value of this option is expanded, and must then be the absolute path to -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. +The value of this option is expanded and indicates the source of DH parameters +to be used by Exim. + +If it is a filename starting with a &`/`&, then it names a file from which DH +parameters should be loaded. If the file exists, it should hold a PEM-encoded +PKCS#3 representation of the DH prime. If the file does not exist, for +OpenSSL it is an error. For GnuTLS, Exim will attempt to create the file and +fill it with a generated DH prime. For OpenSSL, if the DH bit-count from +loading the file is greater than &%tls_dh_max_bits%& then it will be ignored, +and treated as though the &%tls_dhparam%& were set to "none". + +If this option expands to the string "none", then no DH parameters will be +loaded by Exim. + +If this option expands to the string "historic" and Exim is using GnuTLS, then +Exim will attempt to load a file from inside the spool directory. If the file +does not exist, Exim will attempt to create it. +See section &<>& for further details. + +If Exim is using OpenSSL and this option is empty or unset, then Exim will load +a default DH prime; the default is the 2048 bit prime described in section +2.2 of RFC 5114, "2048-bit MODP Group with 224-bit Prime Order Subgroup", which +in IKE is assigned number 23. + +Otherwise, the option must expand to the name used by Exim for any of a number +of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses +"ike" followed by the number used by IKE, of "default" which corresponds to +"ike23". + +The available primes are: +&`ike1`&, &`ike2`&, &`ike5`&, +&`ike14`&, &`ike15`&, &`ike16`&, &`ike17`&, &`ike18`&, +&`ike22`&, &`ike23`& (aka &`default`&) and &`ike24`&. + +Some of these will be too small to be accepted by clients. +Some may be too large to be accepted by clients. + +The TLS protocol does not negotiate an acceptable size for this; clients tend +to hard-drop connections if what is offered by the server is unacceptable, +whether too large or too small, and there's no provision for the client to +tell the server what these constraints are. Thus, as a server operator, you +need to make an educated guess as to what is most likely to work for your +userbase. + +Some known size constraints suggest that a bit-size in the range 2048 to 2236 +is most likely to maximise interoperability. The upper bound comes from +applications using the Mozilla Network Security Services (NSS) library, which +used to set its &`DH_MAX_P_BITS`& upper-bound to 2236. This affects many +mail user agents (MUAs). The lower bound comes from Debian installs of Exim4 +prior to the 4.80 release, as Debian used to patch Exim to raise the minimum +acceptable bound from 1024 to 2048. .option tls_on_connect_ports main "string list" unset @@ -15210,6 +16073,8 @@ 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. +See &<>& for discussion of when this option might be re-expanded. + .option tls_remember_esmtp main boolean false .cindex "TLS" "esmtp state; remembering" @@ -15249,6 +16114,18 @@ 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. + +See &<>& for discussion of when this option might be re-expanded. + +A forced expansion failure or setting to an empty string is equivalent to +being unset. + .option tls_verify_hosts main "host list&!!" unset .cindex "TLS" "client certificate verification" @@ -15586,6 +16463,9 @@ 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 unusual 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: @@ -15596,16 +16476,24 @@ 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:$local_part}}{postmaster}} +condition = foobar +.endd + If the expansion fails (other than forced failure) delivery is deferred. Some of the other precondition options are common special cases that could in fact be specified using &%condition%&. - .option debug_print routers string&!! unset .cindex "testing" "variables in drivers" If this option is set and debugging is enabled (see the &%-d%& command line -option), the string is expanded and included in the debugging output. +option) or in address-testing mode (see the &%-bt%& command line option), +the string is expanded and included in the debugging output. If expansion of the string fails, the error message is written to the debugging output, and Exim carries on processing. This option is provided to help with checking out the values of variables and @@ -15614,6 +16502,7 @@ option appears not to be working, &%debug_print%& can be used to output the variables it references. The output happens after checks for &%domains%&, &%local_parts%&, and &%check_local_user%& but before any other preconditions are tested. A newline is added to the text if it does not end with one. +The variable &$router_name$& contains the name of the router. @@ -15775,6 +16664,9 @@ The &%headers_add%& option is expanded after &%errors_to%&, but before the expansion is forced to fail, the option has no effect. Other expansion failures are treated as configuration errors. +Unlike most options, &%headers_add%& can be specified multiple times +for a router; all listed headers are added. + &*Warning 1*&: The &%headers_add%& option cannot be used for a &(redirect)& router that has the &%one_time%& option set. @@ -15808,6 +16700,9 @@ The &%headers_remove%& option is expanded after &%errors_to%& and the option has no effect. Other expansion failures are treated as configuration errors. +Unlike most options, &%headers_remove%& can be specified multiple times +for a router; all listed headers are removed. + &*Warning 1*&: The &%headers_remove%& option cannot be used for a &(redirect)& router that has the &%one_time%& option set. @@ -16444,7 +17339,8 @@ Setting this option has the effect of setting &%verify_sender%& and .cindex "EXPN" "with &%verify_only%&" .oindex "&%-bv%&" .cindex "router" "used only when verifying" -If this option is set, the router is used only when verifying an address or +If this option is set, the router is used only when verifying an address, +delivering in cutthrough mode or testing with the &%-bv%& option, not when actually doing a delivery, testing with the &%-bt%& option, or running the SMTP EXPN command. It can be further restricted to verifying only senders or recipients by means of @@ -16458,7 +17354,8 @@ user or group. .option verify_recipient routers&!? boolean true If this option is false, the router is skipped when verifying recipient -addresses +addresses, +delivering in cutthrough mode or testing recipient verification using &%-bv%&. See section &<>& for a list of the order in which preconditions are evaluated. @@ -16559,6 +17456,38 @@ look for A or AAAA records, unless the domain matches &%mx_domains%&, in which case routing fails. +.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 + + .section "Private options for dnslookup" "SECID118" @@ -17782,6 +18711,18 @@ quote just the command. An item such as .endd is interpreted as a pipe with a rather strange command name, and no arguments. +.new +Note that the above example assumes that the text comes from a lookup source +of some sort, so that the quotes are part of the data. If composing a +redirect router with a &%data%& option directly specifying this command, the +quotes will be used by the configuration parser to define the extent of one +string, but will not be passed down into the redirect router itself. There +are two main approaches to get around this: escape quotes to be part of the +data itself, or avoid using this mechanism and instead create a custom +transport with the &%command%& option set and reference that transport from +an &%accept%& router. +.wen + .next .cindex "file" "in redirection list" .cindex "address redirection" "to file" @@ -17856,10 +18797,10 @@ 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 @@ -18722,6 +19663,8 @@ so on when debugging driver configurations. For example, if a &%headers_add%& option is not working properly, &%debug_print%& could be used to output the variables it references. A newline is added to the text if it does not end with one. +The variables &$transport_name$& and &$router_name$& contain the name of the +transport and the router that called it. .option delivery_date_add transports boolean false @@ -18767,6 +19710,9 @@ routers. If the result of the expansion is an empty string, or if the expansion is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. +Unlike most options, &%headers_add%& can be specified multiple times +for a transport; all listed headers are added. + .option headers_only transports boolean false @@ -18789,6 +19735,9 @@ routers. If the result of the expansion is an empty string, or if the expansion is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. +Unlike most options, &%headers_remove%& can be specified multiple times +for a router; all listed headers are added. + .option headers_rewrite transports string unset @@ -19004,11 +19953,9 @@ 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 @@ -19095,7 +20042,7 @@ message, which happens if the &%return_message%& option is set. .option transport_filter_timeout transports time 5m .cindex "transport" "filter, timeout" -When Exim is reading the output of a transport filter, it a applies a timeout +When Exim is reading the output of a transport filter, it applies a timeout that can be set by this option. Exceeding the timeout is normally treated as a temporary delivery failure. However, if a transport filter is used with a &(pipe)& transport, a timeout in the transport filter is treated in the same @@ -19679,9 +20626,10 @@ This option applies only to deliveries in maildir format, and is described in section &<>& below. -.option maildir_use_size_file appendfile boolean false +.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 @@ -19886,6 +20834,7 @@ 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" @@ -20300,6 +21249,7 @@ 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$&" Tags can be used to encode the size of files in their names; see &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%& @@ -20309,8 +21259,19 @@ forced to fail, the tag is ignored, but a non-forced failure causes delivery to be deferred. The expanded tag may contain any printing characters except &"/"&. Non-printing characters in the string are ignored; if the resulting string is empty, it is ignored. If it starts with an alphanumeric character, a leading -colon is inserted. +colon is inserted; this default has not proven to be the path that popular +maildir implementations have chosen (but changing it in Exim would break +backwards compatibility). +For one common implementation, you might set: +.code +maildir_tag = ,S=${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" @@ -20651,8 +21612,8 @@ 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. &new("Delivery -is deferred, and will be tried again later.") Here is an example of a typical +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: @@ -20697,10 +21658,10 @@ that are routed to the transport. .vindex "&$address_pipe$&" A router redirects an address directly to a pipe command (for example, from an alias or forward file). In this case, &$address_pipe$& contains the text of the -pipe command, and the &%command%& option on the transport is ignored. If only -one address is being transported (&%batch_max%& is not greater than one, or -only one address was redirected to this pipe command), &$local_part$& contains -the local part that was redirected. +pipe command, and the &%command%& option on the transport is ignored unless +&%force_command%& is set. If only one address is being transported +(&%batch_max%& is not greater than one, or only one address was redirected to +this pipe command), &$local_part$& contains the local part that was redirected. .endlist @@ -20736,9 +21697,14 @@ 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 @@ -20803,6 +21769,15 @@ inserted in the argument list at that point &'as a separate argument'&. This avoids any problems with spaces or shell metacharacters, and is of use when a &(pipe)& transport is handling groups of addresses in a batch. +If &%force_command%& is enabled on the transport, Special handling takes place +for an argument that consists of precisely the text &`$address_pipe`&. It +is handled similarly to &$pipe_addresses$& above. It is expanded and each +argument is inserted in the argument list at that point +&'as a separate argument'&. The &`$address_pipe`& item does not need to be +the only item in the argument; in fact, if it were then &%force_command%& +should behave as a no-op. Rather, it should be used to adjust the command +run while preserving the argument vector separation. + After splitting up into arguments and expansion, the resulting command is run in a subprocess directly from the transport, &'not'& under a shell. The message that is being delivered is supplied on the standard input, and the @@ -20947,6 +21922,31 @@ 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 force_command pipe boolean false +.cindex "force command" +.cindex "&(pipe)& transport", "force command" +Normally when a router redirects an address directly to a pipe command +the &%command%& option on the transport is ignored. If &%force_command%& +is set, the &%command%& option will used. This is especially +useful for forcing a wrapper or additional argument to be added to the +command. For example: +.code +command = /usr/bin/remote_exec myhost -- $address_pipe +force_command +.endd + +Note that &$address_pipe$& is handled specially in &%command%& when +&%force_command%& is set, expanding out to the original argument vector as +separate items, similarly to a Unix shell &`"$@"`& construct. + .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. @@ -21034,6 +22034,17 @@ 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 @@ -21174,6 +22185,7 @@ procmail_pipe: envelope_to_add check_string = "From " escape_string = ">From " + umask = 077 user = $local_part group = mail @@ -21282,17 +22294,23 @@ that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&, .section "Use of $tls_cipher and $tls_peerdn" "usecippeer" +.vindex &$tls_bits$& .vindex &$tls_cipher$& .vindex &$tls_peerdn$& -At the start of a run of the &(smtp)& transport, the values of &$tls_cipher$& -and &$tls_peerdn$& are the values that were set when the message was received. +.vindex &$tls_sni$& +At the start of a run of the &(smtp)& transport, the values of &$tls_bits$&, +&$tls_cipher$&, &$tls_peerdn$& and &$tls_sni$& +are the values that were set when the message was received. These are the values that are used for options that are expanded before any -SMTP connections are made. Just before each connection is made, these two +SMTP connections are made. Just before each connection is made, these four variables are emptied. If TLS is subsequently started, they are set to the appropriate values for the outgoing connection, and these are the values that are in force when any authenticators are run and when the &%authenticated_sender%& option is expanded. +These variables are deprecated in favour of &$tls_in_cipher$& et. al. +and will be removed in a future release. + .section "Private options for smtp" "SECID146" .cindex "options" "&(smtp)& transport" @@ -21330,7 +22348,7 @@ ignored. The expansion happens after the outgoing connection has been made and TLS started, if required. This means that the &$host$&, &$host_address$&, -&$tls_cipher$&, and &$tls_peerdn$& variables are set according to the +&$tls_out_cipher$&, and &$tls_out_peerdn$& variables are set according to the particular connection. If the SMTP session is not authenticated, the expansion of @@ -21426,6 +22444,22 @@ See the &%search_parents%& option in chapter &<>& for more details. +.new +.option dscp smtp string&!! unset +.cindex "DCSP" "outbound" +This option causes the DSCP value associated with a socket to be set to one +of a number of fixed strings or to numeric value. +The &%-bI:dscp%& option may be used to ask Exim which names it knows of. +Common values include &`throughput`&, &`mincost`&, and on newer systems +&`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F. + +The outbound packets from Exim will be marked with this value in the header +(for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee +that these values will have any effect, not be stripped by networking +equipment, or do much of anything without cooperation with your Network +Engineer and those of all network operators between the source and destination. +.wen + .option fallback_hosts smtp "string list" unset .cindex "fallback" "hosts specified on transport" @@ -21473,17 +22507,10 @@ 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_&. -.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 &<>&. +.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. .option helo_data smtp string&!! "see below" .cindex "HELO" "argument, setting" @@ -21566,6 +22593,13 @@ that matches this list, even if the server host advertises PIPELINING support. Exim will not try to start a TLS session when delivering to any host that matches this list. See chapter &<>& for details of TLS. +.option hosts_verify_avoid_tls smtp "host list&!!" * +.cindex "TLS" "avoiding for certain hosts" +Exim will not try to start a TLS session for a verify callout, +or when delivering in cutthrough mode, +to any host that matches this list. +Note that the default is to not use TLS. + .option hosts_max_try smtp integer 5 .cindex "host" "maximum number to try" @@ -21655,8 +22689,8 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter .vindex "&$host$&" .vindex "&$host_address$&" This option specifies which interface to bind to when making an outgoing SMTP -call. &new("The value is an IP address, not an interface name such as -&`eth0`&.") Do not confuse this with the interface address that was used when a +call. The value is an IP address, not an interface name such as +&`eth0`&. Do not confuse this with the interface address that was used when a message was received, which is in &$received_ip_address$&, formerly known as &$interface_address$&. The name was changed to minimize confusion with the outgoing interface address. There is no variable that contains an outgoing @@ -21734,12 +22768,20 @@ is deferred. .option protocol smtp string smtp .cindex "LMTP" "over TCP/IP" +.cindex "ssmtp protocol" "outbound" +.cindex "TLS" "SSL-on-connect outbound" +.vindex "&$port$&" If this option is set to &"lmtp"& instead of &"smtp"&, the default value for the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local deliveries into closed message stores. Exim also has support for running LMTP over a pipe to a local process &-- see chapter &<>&. +If this option is set to &"smtps"&, the default vaule for the &%port%& option +changes to &"smtps"&, and the transport initiates TLS immediately after +connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. +The Internet standards bodies strongly discourage use of this mode. + .option retry_include_ip_address smtp boolean true Exim normally includes both the host name and the IP address in the key it @@ -21822,6 +22864,19 @@ This option specifies a certificate revocation list. The expanded value must be the name of a file that contains a CRL in PEM format. +.new +.option tls_dh_min_bits smtp integer 1024 +.cindex "TLS" "Diffie-Hellman minimum acceptable size" +When establishing a TLS session, if a ciphersuite which uses Diffie-Hellman +key agreement is negotiated, the server will provide a large prime number +for use. This option establishes the minimum acceptable size of that number. +If the parameter offered by the server is too small, then the TLS handshake +will fail. + +Only supported when using GnuTLS. +.wen + + .option tls_privatekey smtp string&!! unset .cindex "TLS" "client private key, location of" .vindex "&$host$&" @@ -21851,6 +22906,22 @@ ciphers is a preference order. +.option tls_sni smtp string&!! unset +.cindex "TLS" "Server Name Indication" +.vindex "&$tls_sni$&" +If this option is set then it sets the $tls_out_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. + +Note that for OpenSSL, this feature requires a build of OpenSSL that supports +TLS extensions. + + + + .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 @@ -22282,11 +23353,9 @@ rewriting rule is skipped unless the relevant addresses are being processed. &`s`& rewrite the &'Sender:'& header &`t`& rewrite the &'To:'& header .endd -.new "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. -.wen You should be particularly careful about rewriting &'Sender:'& headers, and restrict this to special known cases in your own domains. @@ -23028,14 +24097,24 @@ included by setting .code AUTH_CRAM_MD5=yes AUTH_CYRUS_SASL=yes +AUTH_DOVECOT=yes +AUTH_GSASL=yes +AUTH_HEIMDAL_GSSAPI=yes 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. +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. The authenticators are configured using the same syntax as other drivers (see @@ -23068,6 +24147,28 @@ The remainder of this chapter covers the generic options for the authenticators, followed by general discussion of the way authentication works in Exim. +&*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. + .section "Generic options for authenticators" "SECID168" @@ -23080,11 +24181,14 @@ When Exim is authenticating as a client, it skips any authenticator whose 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}{}} +client_condition = ${if !eq{$tls_out_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 client_set_id authenticators string&!! unset +When client authentication succeeds, this condition is expanded; the +result is used in the log lines for outbound messasges. +Typically it will be the user name used for authentication. .option driver authenticators string unset @@ -23114,6 +24218,9 @@ This option must be set for a &%plaintext%& server authenticator, where it is used directly to control authentication. See section &<>& for details. +For the &(gsasl)& authenticator, this option is required for various +mechanisms; see chapter &<>& for details. + 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 @@ -23241,10 +24348,10 @@ authentication mechanisms. For example, it can be used to restrict the advertisement of a particular mechanism to encrypted connections, by a setting such as: .code -server_advertise_condition = ${if eq{$tls_cipher}{}{no}{yes}} +server_advertise_condition = ${if eq{$tls_in_cipher}{}{no}{yes}} .endd -.vindex "&$tls_cipher$&" -If the session is encrypted, &$tls_cipher$& is not empty, and so the expansion +.vindex "&$tls_in_cipher$&" +If the session is encrypted, &$tls_in_cipher$& is not empty, and so the expansion yields &"yes"&, which allows the advertisement to happen. When an Exim server receives an AUTH command from a client, it rejects it @@ -23451,7 +24558,8 @@ to be returned. If the result of a successful expansion is an empty string, expansion is &"1"&, &"yes"&, or &"true"&, authentication succeeds and the generic &%server_set_id%& option is expanded and saved in &$authenticated_id$&. For any other result, a temporary error code is returned, with the expanded -string as the error text. +string as the error text, and the failed id saved in +&$authenticated_fail_id$&. &*Warning*&: If you use a lookup in the expansion to find the user's password, be sure to make the authentication fail if the user is unknown. @@ -23572,18 +24680,21 @@ 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=$auth1,ou=people,o=example.org .endd -Note the use of the &%quote_ldap_dn%& operator to correctly quote the DN for -authentication. However, the basic &%quote%& operator, rather than any of the -LDAP quoting operators, is the correct one to use for the password, because -quoting is needed only to make the password conform to the Exim syntax. At the -LDAP level, the password is an uninterpreted string. - +We have to check that the username is not empty before using it, because LDAP +does not permit empty DN components. We must also use the &%quote_ldap_dn%& +operator to correctly quote the DN for authentication. However, the basic +&%quote%& operator, rather than any of the LDAP quoting operators, is the +correct one to use for the password, because quoting is needed only to make +the password conform to the Exim syntax. At the LDAP level, the password is an +uninterpreted string. .section "Support for different kinds of authentication" "SECID174" @@ -23716,6 +24827,18 @@ lookup_cram: Note that this expansion explicitly forces failure if the lookup fails because &$auth1$& contains an unknown user name. +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 .section "Using cram_md5 as a client" "SECID177" .cindex "options" "&(cram_md5)& authenticator (client)" @@ -23789,10 +24912,16 @@ 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. + +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 &<>& .section "Using cyrus_sasl as a server" "SECID178" @@ -23823,7 +24952,7 @@ sasl: server_set_id = $auth1 .endd -.option server_realm cyrus_sasl string unset +.option server_realm cyrus_sasl string&!! unset This specifies the SASL realm that the server claims to be in. @@ -23844,7 +24973,7 @@ 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, @@ -23877,7 +25006,7 @@ dovecot_plain: driver = dovecot public_name = PLAIN server_socket = /var/run/dovecot/auth-client - server_set_id = $auth1 + server_set_id = $auth2 dovecot_ntlm: driver = dovecot @@ -23895,6 +25024,213 @@ who authenticated is placed in &$auth1$&. .ecindex IIDdcotauth2 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// +.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 + + +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.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$&: the &'authorization id'&, sent within SASL encapsulation after +authentication. If that was empty, this will also be set to the +GSS Display Name. +.endlist + + . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -24079,34 +25415,54 @@ There are some differences in usage when using GnuTLS instead of OpenSSL: The &%tls_verify_certificates%& option must contain the name of a file, not the name of a directory (for OpenSSL it can be either). .next -The &%tls_dhparam%& option is ignored, because early versions of GnuTLS had no -facility for varying its Diffie-Hellman parameters. I understand that this has -changed, but Exim has not been updated to provide this facility. +The default value for &%tls_dhparam%& differs for historical reasons. .next -.vindex "&$tls_peerdn$&" +.vindex "&$tls_in_peerdn$&" +.vindex "&$tls_out_peerdn$&" Distinguished Name (DN) strings reported by the OpenSSL library use a slash for separating fields; GnuTLS uses commas, in accordance with RFC 2253. This -affects the value of the &$tls_peerdn$& variable. +affects the value of the &$tls_in_peerdn$& and &$tls_out_peerdn$& variables. .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 &<>&. +.next +.new +The &%tls_dh_min_bits%& SMTP transport option is only honoured by GnuTLS. +When using OpenSSL, this option is ignored. +(If an API is found to let OpenSSL be configured in this way, +let the Exim Maintainers know and we'll likely use it). +.wen +.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. .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" +This section only applies if &%tls_dhparam%& is set to &`historic`& or to +an explicit path; if the latter, then the text about generation still applies, +but not the chosen filename. +By default, as of Exim 4.80 a hard-coded D-H prime is used. +See the documentation of &%tls_dhparam%& for more information. + +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 @@ -24115,6 +25471,10 @@ place, new Exim processes immediately start using it. For maximum security, the parameters that are stored in this file should be recalculated periodically, the frequency depending on your paranoia level. +If you are avoiding using the fixed D-H primes published in RFCs, then you +are concerned about some advanced attacks and will wish to do this; if you do +not regenerate then you might as well stick to the standard primes. + Arranging this is easy in principle; just delete the file when you want new values to be computed. However, there may be a problem. The calculation of new parameters needs random numbers, and these are obtained from &_/dev/random_&. @@ -24123,26 +25483,54 @@ 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 +# openssl dhparam -noout -text -in new-params | head +[ check the first line, make sure it's not more than 2236; + if it is, then go back to the start ("rm") and repeat + until the size generated is at most the size requested ] # 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. + +In fact, the requested value will be *lower* than &%tls_dh_max_bits%&, to +increase the chance of the generated prime actually being within acceptable +bounds, as GnuTLS has been observed to overshoot. Note the check step in the +procedure above. There is no sane procedure available to Exim to double-check +the size of the generated prime, so it might still be too large. + .section "Requiring specific ciphers in OpenSSL" "SECTreqciphssl" .cindex "TLS" "requiring specific ciphers (OpenSSL)" @@ -24151,7 +25539,10 @@ 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 @@ -24188,6 +25579,24 @@ includes any ciphers already present they will be ignored: that is, they will not be moved to the end of the list. .endlist +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 + .section "Requiring specific ciphers or other parameters in GnuTLS" &&& @@ -24197,78 +25606,44 @@ 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.gnutls.org/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.gnutls.org/manual/gnutls.html#Listing-the-ciphersuites-in-a-priority-string, 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 .section "Configuring an Exim server to use TLS" "SECID182" @@ -24328,13 +25703,22 @@ this). There is one other option that may be needed in other situations. If tls_dhparam = /some/file/name .endd is set, the SSL library is initialized for the use of Diffie-Hellman ciphers -with the parameters contained in the file. This increases the set of cipher -suites that the server supports. See the command +with the parameters contained in the file. +Set this to &`none`& to disable use of DH entirely, by making no prime +available: +.code +tls_dhparam = none +.endd +This may also be set to a string identifying a standard prime to be used for +DH; if it is set to &`default`& or, for OpenSSL, is unset, then the prime +used is &`ike23`&. There are a few standard primes available, see the +documentation for &%tls_dhparam%& for the complete list. + +See the command .code openssl dhparam .endd -for a way of generating this data. At present, &%tls_dhparam%& is used only -when Exim is linked with OpenSSL. It is ignored if GnuTLS is being used. +for a way of generating file data. The strings supplied for these three options are expanded every time a client host connects. It is therefore possible to use different certificates and keys @@ -24344,15 +25728,13 @@ forced to fail, Exim behaves as if the option is not set. .cindex "cipher" "logging" .cindex "log" "TLS cipher" -.vindex "&$tls_cipher$&" -The variable &$tls_cipher$& is set to the cipher suite that was negotiated for +.vindex "&$tls_in_cipher$&" +The variable &$tls_in_cipher$& is set to the cipher suite that was negotiated for an incoming TLS connection. It is included in the &'Received:'& header of an 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. -&new("(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 @@ -24361,6 +25743,9 @@ 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. +For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged +(again depending on the &%tls_cipher%& log selector). + .section "Requesting and verifying client certificates" "SECID183" .cindex "certificate" "verification of client" @@ -24397,17 +25782,17 @@ fact that no certificate was verified, and vary their actions accordingly. For example, you can insist on a certificate before accepting a message for relaying, but not when the message is destined for local delivery. -.vindex "&$tls_peerdn$&" +.vindex "&$tls_in_peerdn$&" When a client supplies a certificate (whether it verifies or not), the value of the Distinguished Name of the certificate is made available in the variable -&$tls_peerdn$& during subsequent processing of the message. +&$tls_in_peerdn$& during subsequent processing of the message. .cindex "log" "distinguished name" Because it is often a long text string, it is not included in the log line or &'Received:'& header by default. You can arrange for it to be logged, keyed by &"DN="&, by setting the &%tls_peerdn%& log selector, and you can use &%received_header_text%& to change the &'Received:'& header. When no -certificate is supplied, &$tls_peerdn$& is empty. +certificate is supplied, &$tls_in_peerdn$& is empty. .section "Revoked certificates" "SECID184" @@ -24460,13 +25845,10 @@ 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 @@ -24478,6 +25860,12 @@ 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 @@ -24485,9 +25873,12 @@ 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 &$tls_cipher$& -.vindex &$tls_peerdn$& -Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$& +.vindex &$tls_out_bits$& +.vindex &$tls_out_cipher$& +.vindex &$tls_out_peerdn$& +.vindex &$tls_out_sni$& +Before an SMTP connection is established, the +&$tls_out_bits$&, &$tls_out_cipher$&, &$tls_out_peerdn$& and &$tls_out_sni$& 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 @@ -24495,6 +25886,80 @@ outgoing connection. +.section "Use of TLS Server Name Indication" "SECTtlssni" +.cindex "TLS" "Server Name Indication" +.vindex "&$tls_in_sni$&" +.oindex "&%tls_in_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 &$tls_out_sni$& variable will be set to this string +for the lifetime of the client connection (including during authentication). + +Except during SMTP client sessions, if &$tls_in_sni$& 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_in_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). + + + .section "Multiple messages on the same encrypted TCP/IP connection" &&& "SECTmulmessam" .cindex "multiple SMTP deliveries with TLS" @@ -24570,6 +26035,8 @@ install if the receiving end is a client MUA that can interact with a user. .cindex "certificate" "self-signed" You can create a self-signed certificate using the &'req'& command provided with OpenSSL, like this: +. ==== Do not shorten the duration here without reading and considering +. ==== the text below. Please leave it at 9999 days. .code openssl req -x509 -newkey rsa:1024 -keyout file1 -out file2 \ -days 9999 -nodes @@ -24582,6 +26049,22 @@ that you are prompted for, and any use that is made of the key causes more prompting for the passphrase. This is not helpful if you are going to use this certificate and key in an MTA, where prompting is not possible. +. ==== I expect to still be working 26 years from now. The less technical +. ==== debt I create, in terms of storing up trouble for my later years, the +. ==== happier I will be then. We really have reached the point where we +. ==== should start, at the very least, provoking thought and making folks +. ==== pause before proceeding, instead of leaving all the fixes until two +. ==== years before 2^31 seconds after the 1970 Unix epoch. +. ==== -pdp, 2012 +NB: we are now past the point where 9999 days takes us past the 32-bit Unix +epoch. If your system uses unsigned time_t (most do) and is 32-bit, then +the above command might produce a date in the past. Think carefully about +the lifetime of the systems you're deploying, and either reduce the duration +of the certificate or reconsider your platform deployment. (At time of +writing, reducing the duration is the most likely choice, but the inexorable +progression of time takes us steadily towards an era where this will not +be a sensible resolution). + A self-signed certificate made in this way is sufficient for testing, and may be adequate for all your requirements if you are mainly interested in encrypting transfers, and not in secure identification. @@ -24672,7 +26155,7 @@ 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 &new(&%acl_smtp_notquit%&) "ACL for non-QUIT terminations" +.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" @@ -24780,11 +26263,29 @@ before or after the data) correctly &-- they keep the message on their queues and try again later, but that is their problem, though it does waste some of your resources. +The &%acl_smtp_data%& ACL is run after both the &%acl_smtp_dkim%& and +the &%acl_smtp_mime%& ACLs. + + +.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. + +This ACL is evaluated before &%acl_smtp_mime%& and &%acl_smtp_data%&. + +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 &<>&. +This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&. + .section "The QUIT ACL" "SECTQUITACL" .cindex "QUIT, ACL for" @@ -24812,10 +26313,10 @@ 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" -The not-QUIT ACL, specified by &%smtp_notquit_acl%&, is run in most cases when -an SMTP session ends without sending QUIT. However, when Exim itself is is bad +.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 in 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. @@ -25126,7 +26627,7 @@ 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. @@ -25169,8 +26670,8 @@ duplicates to be written, use the &%logwrite%& modifier instead. If &%log_message%& is not present, a &%warn%& verb just checks its conditions and obeys any &"immediate"& modifiers (such as &%control%&, &%set%&, -&%logwrite%&, and &%add_header%&) that appear before the first failing -condition. There is more about adding header lines in section +&%logwrite%&, &%add_header%&, and &%remove_header%&) that appear before the +first failing condition. There is more about adding header lines in section &<>&. If any condition on a &%warn%& statement cannot be completed (that is, there is @@ -25288,7 +26789,7 @@ others specify text for messages that are used when access is denied or a warning is generated. The &%control%& modifier affects the way an incoming message is handled. -The positioning of the modifiers in an ACL statement important, because the +The positioning of the modifiers in an ACL statement is important, because the processing of a verb ceases as soon as its outcome is known. Only those modifiers that have already been encountered will take effect. For example, consider this use of the &%message%& modifier: @@ -25409,12 +26910,12 @@ If you want to apply a control unconditionally, you can use it with a .vitem &*delay*&&~=&~<&'time'&> .cindex "&%delay%& ACL modifier" .oindex "&%-bh%&" -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. +This modifier may appear in any ACL except notquit. 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. Like &%control%&, &%delay%& can be used with &%accept%& or &%deny%&, for example: @@ -25461,7 +26962,7 @@ confusing to some people, so the use of &%endpass%& is no longer recommended as This modifier sets up a message that is used as part of the log message if the ACL denies access or a &%warn%& statement's conditions are true. For example: .code -require log_message = wrong cipher suite $tls_cipher +require log_message = wrong cipher suite $tls_in_cipher encrypted = DES-CBC3-SHA .endd &%log_message%& is also used when recipients are discarded by &%discard%&. For @@ -25516,7 +27017,8 @@ 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'&> @@ -25611,10 +27113,31 @@ all the conditions are true, wherever it appears in an ACL command, whereas effect. +.vitem &*remove_header*&&~=&~<&'text'&> +This modifier specifies one or more header names in a colon-separated list + that are to be removed from an incoming message, assuming, of course, that +the message is ultimately accepted. For details, see section &<>&. + + .vitem &*set*&&~<&'acl_name'&>&~=&~<&'value'&> .cindex "&%set%& ACL modifier" This modifier puts a value into one of the ACL variables (see section &<>&). + + +.vitem &*udpsend*&&~=&~<&'parameters'&> +This modifier sends a UDP packet, for purposes such as statistics +collection or behaviour monitoring. The parameters are expanded, and +the result of the expansion must be a colon-separated list consisting +of a destination server, port number, and the packet contents. The +server can be specified as a host name or IPv4 or IPv6 address. The +separator can be changed with the usual angle bracket syntax. For +example, you might want to collect information on which hosts connect +when: +.code +udpsend = <; 2001:dB8::dead:beef ; 1234 ;\ + $tod_zulu $sender_host_address +.endd .endlist @@ -25676,6 +27199,77 @@ warn control = caseful_local_part Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. + +.new +.vitem &*control&~=&~cutthrough_delivery*& +.cindex "&ACL;" "cutthrough routing" +.cindex "cutthrough" "requesting" +This option requests delivery be attempted while the item is being received. +It is usable in the RCPT ACL and valid only for single-recipient mails forwarded +from one SMTP connection to another. If a recipient-verify callout connection is +requested in the same ACL it is held open and used for the data, otherwise one is made +after the ACL completes. Note that routers are used in verify mode. + +Should the ultimate destination system positively accept or reject the mail, +a corresponding indication is given to the source system and nothing is queued. +If there is a temporary error the item is queued for later delivery in the +usual fashion. If the item is successfully delivered in cutthrough mode the log line +is tagged with ">>" rather than "=>" and appears before the acceptance "<=" +line. + +Delivery in this mode avoids the generation of a bounce mail to a (possibly faked) +sender when the destination system is doing content-scan based rejection. +.wen + + +.new +.vitem &*control&~=&~debug/*&<&'options'&> +.cindex "&ACL;" "enabling debug logging" +.cindex "debugging" "enabling from an ACL" +This control turns on debug logging, almost as though Exim had been invoked +with &`-d`&, with the output going to a new logfile, by default called +&'debuglog'&. The filename can be adjusted with the &'tag'& option, which +may access any variables already defined. The logging may be adjusted with +the &'opts'& option, which takes the same values as the &`-d`& command-line +option. Some examples (which depend on variables that don't exist in all +contexts): +.code + control = debug + control = debug/tag=.$sender_host_address + control = debug/opts=+expand+acl + control = debug/tag=.$message_exim_id/opts=+expand +.endd +.wen + + +.new +.vitem &*control&~=&~dkim_disable_verify*& +.cindex "disable DKIM verify" +.cindex "DKIM" "disable verify" +This control turns off DKIM verification processing entirely. For details on +the operation and configuration of DKIM, see chapter &<>&. +.wen + + +.new +.vitem &*control&~=&~dscp/*&<&'value'&> +.cindex "&ACL;" "setting DSCP value" +.cindex "DSCP" "inbound" +This option causes the DSCP value associated with the socket for the inbound +connection to be adjusted to a given value, given as one of a number of fixed +strings or to numeric value. +The &%-bI:dscp%& option may be used to ask Exim which names it knows of. +Common values include &`throughput`&, &`mincost`&, and on newer systems +&`ef`&, &`af41`&, etc. Numeric values may be in the range 0 to 0x3F. + +The outbound packets from Exim will be marked with this value in the header +(for IPv4, the TOS field; for IPv6, the TCLASS field); there is no guarantee +that these values will have any effect, not be stripped by networking +equipment, or do much of anything without cooperation with your Network +Engineer and those of all network operators between the source and destination. +.wen + + .vitem &*control&~=&~enforce_sync*& &&& &*control&~=&~no_enforce_sync*& .cindex "SMTP" "synchronization checking" @@ -25811,7 +27405,7 @@ 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). @@ -25824,7 +27418,7 @@ 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 @@ -25853,12 +27447,12 @@ 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 @@ -25866,7 +27460,7 @@ Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&. .section "Adding header lines in ACLs" "SECTaddheadacl" .cindex "header lines" "adding in an ACL" .cindex "header lines" "position of added lines" -.cindex "&%message%& ACL modifier" +.cindex "&%add_header%& ACL modifier" The &%add_header%& modifier can be used to add one or more extra header lines to an incoming message, as in this example: .code @@ -25881,7 +27475,9 @@ receiving a message). The message must ultimately be accepted for any ACL verb, including &%deny%& (though this is potentially useful only in a RCPT ACL). -If the data for the &%add_header%& modifier contains one or more newlines that +Leading and trailing newlines are removed from +the data for the &%add_header%& modifier; if it then +contains one or more newlines that are not followed by a space or a tab, it is assumed to contain multiple header lines. Each one is checked for valid syntax; &`X-ACL-Warn:`& is added to the front of any line that is not a valid header line. @@ -25899,7 +27495,9 @@ message is rejected after DATA or by the non-SMTP ACL, all added header lines are included in the entry that is written to the reject log. .cindex "header lines" "added; visibility of" -Header lines are not visible in string expansions until they are added to the +Header lines are not visible in string expansions +of message headers +until they are added to the message. It follows that header lines defined in the MAIL, RCPT, and predata ACLs are not visible until the DATA ACL and MIME ACLs are run. Similarly, header lines that are added by the DATA or MIME ACLs are not visible in those @@ -25908,7 +27506,9 @@ passing data between (for example) the MAIL and RCPT ACLs. If you want to do this, you can use ACL variables, as described in section &<>&. -The &%add_header%& modifier acts immediately it is encountered during the +The list of headers yet to be added is given by the &%$headers_added%& variable. + +The &%add_header%& modifier acts immediately as it is encountered during the processing of an ACL. Notice the difference between these two cases: .display &`accept add_header = ADDED: some text`& @@ -25957,10 +27557,81 @@ system filter or in a router or transport. +.section "Removing header lines in ACLs" "SECTremoveheadacl" +.cindex "header lines" "removing in an ACL" +.cindex "header lines" "position of removed lines" +.cindex "&%remove_header%& ACL modifier" +The &%remove_header%& modifier can be used to remove one or more header lines +from an incoming message, as in this example: +.code +warn message = Remove internal headers + remove_header = x-route-mail1 : x-route-mail2 +.endd +The &%remove_header%& modifier is permitted in the MAIL, RCPT, PREDATA, DATA, +MIME, and non-SMTP ACLs (in other words, those that are concerned with +receiving a message). The message must ultimately be accepted for +&%remove_header%& to have any significant effect. You can use &%remove_header%& +with any ACL verb, including &%deny%&, though this is really not useful for +any verb that doesn't result in a delivered message. + +More than one header can be removed at the same time by using a colon separated +list of header names. The header matching is case insensitive. Wildcards are +not permitted, nor is list expansion performed, so you cannot use hostlists to +create a list of headers, however both connection and message variable expansion +are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example: +.code +warn hosts = +internal_hosts + set acl_c_ihdrs = x-route-mail1 : x-route-mail2 +warn message = Remove internal headers + remove_header = $acl_c_ihdrs +.endd +Removed header lines are accumulated during the MAIL, RCPT, and predata ACLs. +They are removed from the message before processing the DATA and MIME ACLs. +There is no harm in attempting to remove the same header twice nor is removing +a non-existent header. Further header lines to be removed may be accumulated +during the DATA and MIME ACLs, after which they are removed from the message, +if present. In the case of non-SMTP messages, headers to be removed are +accumulated during the non-SMTP ACLs, and are removed from the message after +all the ACLs have run. If a message is rejected after DATA or by the non-SMTP +ACL, there really is no effect because there is no logging of what headers +would have been removed. + +.cindex "header lines" "removed; visibility of" +Header lines are not visible in string expansions until the DATA phase when it +is received. Any header lines removed in the MAIL, RCPT, and predata ACLs are +not visible in the DATA ACL and MIME ACLs. Similarly, header lines that are +removed by the DATA or MIME ACLs are still visible in those ACLs. Because of +this restriction, you cannot use header lines as a way of controlling data +passed between (for example) the MAIL and RCPT ACLs. If you want to do this, +you should instead use ACL variables, as described in section +&<>&. + +The &%remove_header%& modifier acts immediately as it is encountered during the +processing of an ACL. Notice the difference between these two cases: +.display +&`accept remove_header = X-Internal`& +&` `&<&'some condition'&> + +&`accept `&<&'some condition'&> +&` remove_header = X-Internal`& +.endd +In the first case, the header line is always removed, whether or not the +condition is true. In the second case, the header line is removed only if the +condition is true. Multiple occurrences of &%remove_header%& may occur in the +same ACL statement. All those that are encountered before a condition fails +are honoured. + +&*Warning*&: This facility currently applies only to header lines that are +present during ACL processing. It does NOT remove header lines that are added +in a system filter or in a router or transport. + + + + .section "ACL conditions" "SECTaclconditions" .cindex "&ACL;" "conditions; list of" -Some of conditions listed in this section are available only when Exim is +Some of the conditions listed in this section are available only when Exim is compiled with the content-scanning extension. They are included here briefly for completeness. More detailed descriptions can be found in the discussion on content scanning in chapter &<>&. @@ -25978,6 +27649,7 @@ The conditions are as follows: .vitem &*acl&~=&~*&<&'name&~of&~acl&~or&~ACL&~string&~or&~file&~name&~'&> .cindex "&ACL;" "nested" .cindex "&ACL;" "indirect" +.cindex "&ACL;" "arguments" .cindex "&%acl%& ACL condition" The possible values of the argument are the same as for the &%acl_smtp_%&&'xxx'& options. The named or inline ACL is run. If it returns @@ -25987,6 +27659,12 @@ condition is on a &%warn%& verb. In that case, a &"defer"& return makes the condition false. This means that further processing of the &%warn%& verb ceases, but processing of the ACL continues. +If the argument is a named ACL, up to nine space-separated optional values +can be appended; they appear within the called ACL in $acl_arg1 to $acl_arg9, +and $acl_narg is set to the count of values. +Previous values of these variables are restored after the call returns. +The name and values are expanded separately. + If the nested &%acl%& returns &"drop"& and the outer condition denies access, the connection is dropped. If it returns &"discard"&, the verb must be &%accept%& or &%discard%&, and the action is taken immediately &-- no further @@ -26075,7 +27753,7 @@ encrypted = * .endd -.vitem &*hosts&~=&~*&<&'&~host&~list'&> +.vitem &*hosts&~=&~*&<&'host&~list'&> .cindex "&%hosts%& ACL condition" .cindex "host" "ACL checking" .cindex "&ACL;" "testing the client host" @@ -26362,7 +28040,9 @@ 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 : \ @@ -26733,7 +28413,7 @@ dnslists = a.b.c!&0.0.0.1 If the DNS lookup yields both 127.0.0.1 and 127.0.0.2, the condition is false because 127.0.0.1 matches. .next -If &`!==`& or &`!=&&`& is used, the condition is true there is at least one +If &`!==`& or &`!=&&`& is used, the condition is true if there is at least one looked up IP address that does not match. Consider: .code dnslists = a.b.c!=&0.0.0.1 @@ -26854,7 +28534,7 @@ 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 @@ -26863,83 +28543,133 @@ 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$& is only meaningful if the client has -authenticated, and you can check with the &%authenticated%& ACL condition. +authenticated (which you can check with the &%authenticated%& ACL condition). + +The lookup key does not have to identify clients: If you want to limit the +rate at which a recipient receives messages, you can use the key +&`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT +ACL. -If you want to limit the rate at which a recipient receives messages, you can -use the key &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in -a RCPT ACL. +Each &%ratelimit%& condition can have up to 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. -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. +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. -Each &%ratelimit%& condition can have up to three options. One option -specifies what Exim measures the rate of, and the second specifies how Exim -handles excessively fast clients. The third option can be &`noupdate`&, to -disable updating of the ratelimiting database (see section &<>&). -The options are separated by a slash, like the other parameters. They may -appear in any order. .section "Ratelimit options for what is being measured" "ratoptmea" -The &%per_conn%& option limits the client's connection rate. +.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_mail%& option limits the client's rate of sending messages. This is -the default if none of the &%per_*%& options is specified. +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_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. +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. -.new -The &%per_rcpt%& option causes Exim to limit the rate at which -recipients are accepted. To be effective, it would need to be used in -either the &%acl_smtp_rcpt%& or the &%acl_not_smtp%& ACL. In the -&%acl_smtp_rcpt%& ACL, the number of recipients is incremented by one. -In the case of a locally submitted message in the &%acl_not_smtp%& ACL, -the number of recipients incremented is equal to &%$recipients_count%& -for the entire message. Note that in either case the rate limiting -engine will see a message with many recipients as a large high-speed -burst. +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 &%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. -This command is essentially an alias of &%per_rcpt%& to make it clear -that the effect is to limit the rate at which individual commands, -rather than recipients, are accepted. -.wen +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. -.section "Ratelimit options for handling fast clients" "ratophanfas" +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. +rest of the ACL. -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 &new("it is actually -allowed. If the client is over the limit it may be subjected to -counter-measures in the ACL 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%& (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 @@ -26947,6 +28677,59 @@ 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 @@ -26990,36 +28773,6 @@ this means that Exim will lose its hints data after a reboot (including retry hints, the callout cache, and ratelimit data). -.section "Reading ratelimit data without updating" "rearatdat" -.cindex "rate limitint" "reading data without updating" -If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim -computes the rate and checks the limit as normal, but it does not update the -saved data. This means that, in relevant ACLs, it is possible to lookup the -existence of a specified (or auto-generated) ratelimit key without incrementing -the ratelimit counter for that key. In order for this to be useful, another ACL -entry must set the rate for the same key (otherwise it will always be zero). -For example: -.code -acl_check_connect: - deny ratelimit = 100 / 5m / strict / noupdate - log_message = RATE: $sender_rate/$sender_rate_period \ - (max $sender_rate_limit) -.endd -.display -&'... some other logic and tests...'& -.endd -.code -acl_check_mail: - warn ratelimit = 100 / 5m / strict / per_cmd - condition = ${if le{$sender_rate}{$sender_rate_limit}} - logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \ - (max $sender_rate_limit) -.endd -In this example, the rate is tested and used to deny access (when it is too -high) in the connect ACL, but the actual computation of the remembered rate -happens later, on a per-command basis, in another ACL. - - .section "Address verification" "SECTaddressverification" .cindex "verifying address" "options for" @@ -27155,6 +28908,9 @@ following SMTP commands are sent: LHLO is used instead of HELO if the transport's &%protocol%& option is set to &"lmtp"&. +The callout may use EHLO, AUTH and/or STARTTLS given appropriate option +settings. + A recipient callout check is similar. By default, it also uses an empty address for the sender. This default is chosen because most hosts do not make use of the sender address when verifying a recipient. Using the same address means @@ -27294,7 +29050,7 @@ check for a &"random"& local part at the same domain. The local part is not really random &-- it is defined by the expansion of the option &%callout_random_local_part%&, which defaults to .code -$primary_host_name-$tod_epoch-testing +$primary_hostname-$tod_epoch-testing .endd The idea here is to try to determine whether the remote host accepts all local parts without checking. If it does, there is no point in doing callouts for @@ -27596,19 +29352,8 @@ the third string (in this case &"1"&), whether or not the cryptographic and timeout checks succeed. The &$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 @@ -27681,16 +29426,16 @@ Suppose your LAN is 192.168.45.0/24. In the main part of the configuration, you put the following definitions: .code -domainlist local_domains = my.dom1.example : my.dom2.example -domainlist relay_domains = friend1.example : friend2.example -hostlist relay_hosts = 192.168.45.0/24 +domainlist local_domains = my.dom1.example : my.dom2.example +domainlist relay_to_domains = friend1.example : friend2.example +hostlist relay_from_hosts = 192.168.45.0/24 .endd Now you can use these definitions in the ACL that is run for every RCPT command: .code acl_check_rcpt: - accept domains = +local_domains : +relay_domains - accept hosts = +relay_hosts + accept domains = +local_domains : +relay_to_domains + accept hosts = +relay_from_hosts .endd The first statement accepts any RCPT command that contains an address in the local or relay domains. For any other domain, control passes to the second @@ -27795,6 +29540,7 @@ 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 @@ -27806,7 +29552,7 @@ 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 @@ -27820,6 +29566,7 @@ 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 @@ -27830,8 +29577,16 @@ 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. @@ -27971,6 +29726,9 @@ 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) @@ -28047,6 +29805,10 @@ 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: @@ -28089,9 +29851,8 @@ 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 &$spam_score$& @@ -28100,11 +29861,9 @@ 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 @@ -28117,14 +29876,15 @@ 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 @@ -28167,7 +29927,7 @@ 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 &new(&'Content-Type:'&) header line. When a call to a MIME +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. @@ -30042,6 +31802,10 @@ headers_add = X-added-header: added by $primary_hostname\n\ .endd Exim does not check the syntax of these added header lines. +Multiple &%headers_add%& options for a single router or transport can be +specified; the values will be concatenated (with a separating newline +added) before expansion. + The result of expanding &%headers_remove%& must consist of a colon-separated list of header names. This is confusing, because header names themselves are often terminated by colons. In this case, the colons are the list separators, @@ -30049,6 +31813,11 @@ not part of the names. For example: .code headers_remove = return-receipt-to:acknowledge-to .endd + +Multiple &%headers_remove%& options for a single router or transport can be +specified; the values will be concatenated (with a separating colon +added) before expansion. + When &%headers_add%& or &%headers_remove%& is specified on a router, its value is expanded at routing time, and then associated with all addresses that are accepted by that router, and also with any new addresses that it generates. If @@ -30287,6 +32056,8 @@ required for the transaction. If the remote server advertises support for the STARTTLS command, and Exim was built to support TLS encryption, it tries to start a TLS session unless the server matches &%hosts_avoid_tls%&. See chapter &<>& for more details. +Either a match in that or &%hosts_verify_avoid_tls%& apply when the transport +is called for verification. If the remote server advertises support for the AUTH command, Exim scans the authenticators configuration for any suitable client settings, as described @@ -30303,8 +32074,8 @@ 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. @@ -30790,8 +32561,8 @@ 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 @@ -31728,8 +33499,8 @@ 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 @@ -31773,14 +33544,15 @@ 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: @@ -31788,6 +33560,7 @@ 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 @@ -31796,14 +33569,16 @@ 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 @@ -31906,6 +33681,7 @@ timestamp. The flags are: &`<=`& message arrival &`=>`& normal message delivery &`->`& additional address in same delivery +&`>>`& cutthrough message delivery &`*>`& delivery suppressed by &%-N%& &`**`& delivery failed; address bounced &`==`& delivery deferred; temporary problem @@ -32005,6 +33781,11 @@ intermediate address(es) exist between the original and the final address, the last of these is given in parentheses after the final address. The R and T fields record the router and transport that were used to process the address. +If SMTP AUTH was used for the delivery there is an additional item A= +followed by the name of the authenticator that was used. +If an authenticated identification was set up by the authenticator's &%client_set_id%& +option, this is logged too, separated by a colon from the authenticator name. + If a shadow transport was run after a successful local delivery, the log line for the successful delivery has an item added on the end, of the form .display @@ -32020,6 +33801,12 @@ flagged with &`->`& instead of &`=>`&. When two or more messages are delivered down a single SMTP connection, an asterisk follows the IP address in the log lines for the second and subsequent messages. +.cindex "delivery" "cutthrough; logging" +.cindex "cutthrough" "logging" +When delivery is done in cutthrough mode it is flagged with &`>>`& and the log +line precedes the reception line, since cutthrough waits for a possible +rejection from the destination in case it can reject the sourced item. + The generation of a reply message by a filter file gets logged as a &"delivery"& to the addressee, preceded by &">"&. @@ -32112,7 +33899,7 @@ at the end of its processing. A summary of the field identifiers that are used in log lines is shown in the following table: .display -&`A `& authenticator name (and optional id) +&`A `& authenticator name (and optional id and sender) &`C `& SMTP confirmation on delivery &` `& command list for &"no mail in SMTP session"& &`CV `& certificate verification status @@ -32196,6 +33983,7 @@ log_selector = +arguments -retry_defer The list of optional log items is in the following table, with the default selection marked by asterisks: .display +&` 8bitmime `& received 8BITMIME status &`*acl_warn_skipped `& skipped &%warn%& statement in ACL &` address_rewrite `& address rewriting &` all_parents `& all parents in => lines @@ -32225,9 +34013,10 @@ selection marked by asterisks: &`*sender_verify_fail `& sender verification failures &`*size_reject `& rejection because too big &`*skip_delivery `& delivery skipped in a queue run -&` smtp_confirmation `& SMTP confirmation on => lines +&`*smtp_confirmation `& SMTP confirmation on => lines &` smtp_connection `& SMTP connections &` smtp_incomplete_transaction`& incomplete SMTP transactions +&` smtp_mailauth `& AUTH argument to MAIL commands &` smtp_no_mail `& session with no MAIL commands &` smtp_protocol_error `& SMTP protocol errors &` smtp_syntax_error `& SMTP syntax errors @@ -32235,6 +34024,7 @@ selection marked by asterisks: &` 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 @@ -32242,6 +34032,14 @@ selection marked by asterisks: More details on each of these items follows: .ilist +.cindex "8BITMIME" +.cindex "log" "8BITMIME" +&%8bitmime%&: This causes Exim to log any 8BITMIME status of received messages, +which may help in tracking down interoperability issues with ancient MTAs +that are not 8bit clean. This is added to the &"<="& line, tagged with +&`M8S=`& and a value of &`0`&, &`7`& or &`8`&, corresponding to "not given", +&`7BIT`& and &`8BITMIME`& respectively. +.next .cindex "&%warn%& ACL verb" "log when skipping" &%acl_warn_skipped%&: When an ACL &%warn%& statement is skipped because one of its conditions cannot be evaluated, a log line to this effect is written if @@ -32487,6 +34285,11 @@ 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. .next +&%smtp_mailauth%&: A third subfield with the authenticated sender, +colon-separated, is appended to the A= item for a message arrival or delivery +log line, if an AUTH argument to the SMTP MAIL command (see &<>&) +was accepted or used. +.next .cindex "log" "SMTP protocol error" .cindex "SMTP" "logging protocol error" &%smtp_protocol_error%&: A log line is written for every SMTP protocol error @@ -32530,6 +34333,12 @@ 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. @@ -32652,14 +34461,14 @@ options are available: .vlist .vitem &*-f*&&~<&'regex'&> -Match the sender address. The field that is tested is enclosed in angle -brackets, so you can test for bounce messages with +Match the sender address using a case-insensitive search. The field that is +tested is enclosed in angle brackets, so you can test for bounce messages with .code exiqgrep -f '^<>$' .endd .vitem &*-r*&&~<&'regex'&> -Match a recipient address. The field that is tested is not enclosed in angle -brackets. +Match a recipient address using a case-insensitve search. The field that is +tested is not enclosed in angle brackets. .vitem &*-s*&&~<&'regex'&> Match against the size field. @@ -33320,6 +35129,12 @@ 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 @@ -33642,15 +35457,26 @@ 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. @@ -33664,7 +35490,6 @@ 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" @@ -33706,11 +35531,13 @@ 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%&" @@ -33865,6 +35692,50 @@ are given in chapter &<>&. +.section "Running local commands" "SECTsecconslocalcmds" +There are a number of ways in which an administrator can configure Exim to run +commands based upon received, untrustworthy, data. Further, in some +configurations a user who can control a &_.forward_& file can also arrange to +run commands. Configuration to check includes, but is not limited to: + +.ilist +Use of &%use_shell%& in the pipe transport: various forms of shell command +injection may be possible with this option present. It is dangerous and should +be used only with considerable caution. Consider constraints which whitelist +allowed characters in a variable which is to be used in a pipe transport that +has &%use_shell%& enabled. +.next +A number of options such as &%forbid_filter_run%&, &%forbid_filter_perl%&, +&%forbid_filter_dlfunc%& and so forth which restrict facilities available to +&_.forward_& files in a redirect router. If Exim is running on a central mail +hub to which ordinary users do not have shell access, but home directories are +NFS mounted (for instance) then administrators should review the list of these +forbid options available, and should bear in mind that the options that may +need forbidding can change as new features are added between releases. +.next +The &%${run...}%& expansion item does not use a shell by default, but +administrators can configure use of &_/bin/sh_& as part of the command. +Such invocations should be viewed with prejudicial suspicion. +.next +Administrators who use embedded Perl are advised to explore how Perl's +taint checking might apply to their usage. +.next +Use of &%${expand...}%& is somewhat analagous to shell's eval builtin and +administrators are well advised to view its use with suspicion, in case (for +instance) it allows a local-part to contain embedded Exim directives. +.next +Use of &%${match_local_part...}%& and friends becomes more dangerous if +Exim was built with EXPAND_LISTMATCH_RHS defined: the second string in +each can reference arbitrary lists and files, rather than just being a list +of opaque strings. +The EXPAND_LISTMATCH_RHS option was added and set false by default because of +real-world security vulnerabilities caused by its use with untrustworthy data +injected in, for SQL injection attacks. +Consider the use of the &%inlisti%& expansion condition instead. +.endlist + + + .section "IPv4 source routing" "SECID272" .cindex "source routing" "in IP packets" .cindex "IP source routing" @@ -33967,6 +35838,12 @@ 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 @@ -34313,13 +36190,279 @@ unqualified domain &'foundation'&. .ecindex IIDforspo2 .ecindex IIDforspo3 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.chapter "Support for DKIM (DomainKeys Identified Mail)" "CHAPdkim" &&& + "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 &%$dkim_cur_signer%&). This is typically used to restrict an ACL +verb to a group of domains or identities. For example: +.code +# Warn when Mail purportedly from GMail has no signature at all +warn log_message = GMail sender without DKIM signature + sender_domains = gmail.com + dkim_signers = gmail.com + dkim_status = none +.endd +.vitem &%dkim_status%& +ACL condition that checks a colon-separated list of possible DKIM verification +results against the actual result of verification. This is typically used +to restrict an ACL verb to a list of verification outcomes, for example: + +.code +deny message = Mail from Paypal with invalid/missing signature + sender_domains = paypal.com:paypal.de + dkim_signers = paypal.com:paypal.de + dkim_status = none:invalid:fail +.endd + +The possible status keywords are: 'none','invalid','fail' and 'pass'. Please +see the documentation of the &%$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" @@ -34347,6 +36490,12 @@ Add to &_src/config.h.defaults_& the line: Edit &_src/drtables.c_&, adding conditional code to pull in the private header and create a table entry as is done for all the other drivers and lookup types. .next +Edit &_scripts/lookups-Makefile_& if this is a new lookup; there is a for-loop +near the bottom, ranging the &`name_mod`& variable over a list of all lookups. +Add your &`NEWDRIVER`& to that list. +As long as the dynamic module would be named &_newdriver.so_&, you can use the +simple form that most lookups have. +.next Edit &_Makefile_& in the appropriate sub-directory (&_src/routers_&, &_src/transports_&, &_src/auths_&, or &_src/lookups_&); add a line for the new driver or lookup type and add it to the definition of OBJ.