X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/711df2d9898cf331b49a32e5b1ae9979c9c9cdcb..33191679e1a86ba6d9c38a74d07:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index dc441df2f..fa73e5081 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1,4 +1,4 @@ -. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.26 2007/10/24 17:47:31 fanf2 Exp $ +. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.88 2010/06/14 18:51:09 pdp Exp $ . . ///////////////////////////////////////////////////////////////////////////// . This is the primary source of the Exim Manual. It is an xfpt document that is @@ -47,8 +47,8 @@ . the element must also be updated for each new edition. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.67" -.set version "4.68" +.set previousversion "4.72" +.set version "4.74" .set ACL "access control lists (ACLs)" .set I "    " @@ -172,17 +172,15 @@ 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
+29 May 2010 +EximMaintainers +EM - 4.68 - 23 August 2007 - PH + 4.73 + 19 Nov 2010 + EM -2007University of Cambridge +2009University of Cambridge .literal off @@ -367,6 +365,7 @@ 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. @@ -430,8 +429,6 @@ 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 +453,12 @@ 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. @@ -491,19 +488,17 @@ Please ask Debian-specific questions on this list and not on the general Exim lists. .section "Exim training" "SECID4" -.new .cindex "training courses" Training courses in Cambridge (UK) used to be run annually by the author of Exim, before he retired. At the time of writing, there are no plans to run further Exim courses in Cambridge. However, if that changes, relevant information will be posted at &url(http://www-tus.csx.cam.ac.uk/courses/exim/). -.wen .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. @@ -539,13 +534,13 @@ The &_.bz2_& file is usually a lot smaller than the &_.gz_& file. .cindex "distribution" "signing details" .cindex "distribution" "public key" .cindex "public key for signed distribution" -The distributions are currently signed with Philip Hazel's GPG key. The +The distributions are currently signed with Nigel Metheringham's GPG key. The corresponding public key is available from a number of keyservers, and there is -also a copy in the file &_Public-Key_&. The signatures for the tar bundles are +also a copy in the file &_nigel-pubkey.asc_&. The signatures for the tar bundles are in: .display -&_exim-n.nn.tar.gz.sig_& -&_exim-n.nn.tar.bz2.sig_& +&_exim-n.nn.tar.gz.asc_& +&_exim-n.nn.tar.bz2.asc_& .endd For each released version, the log of changes is made separately available in a separate file in the directory &_ChangeLogs_& so that it is possible to @@ -731,12 +726,11 @@ the Exim documentation, &"spool"& is always used in the first sense. A number of pieces of external code are included in the Exim distribution. .ilist -Regular expressions are supported in the main Exim program and in the Exim -monitor using the freely-distributable PCRE library, copyright © -University of Cambridge. The source is distributed in the directory -&_src/pcre_&. However, this is a cut-down version of PCRE. If you want to use -the PCRE library in other programs, you should obtain and install the full -version of the library from +Regular expressions are supported in the main Exim program and in the +Exim monitor using the freely-distributable PCRE library, copyright +© University of Cambridge. The source to PCRE is no longer shipped with +Exim, so you will need to use the version of PCRE shipped with your system, +or obtain and install the full version of the library from &url(ftp://ftp.csx.cam.ac.uk/pub/software/programming/pcre). .next .cindex "cdb" "acknowledgment" @@ -1550,7 +1544,6 @@ 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 @@ -1656,6 +1649,18 @@ architecture and operating system for itself, but the defaults can be overridden if necessary. +.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 +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/). + .section "DBM libraries" "SECTdb" .cindex "DBM libraries" "discussion of" .cindex "hints database" "DBM files used for" @@ -1888,8 +1893,11 @@ given in chapter &<>&. .section "Use of tcpwrappers" "SECID27" +.new .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 @@ -1904,16 +1912,19 @@ USE_TCP_WRAPPERS=yes CFLAGS=-O -I/usr/local/include EXTRALIBS_EXIM=-L/usr/local/lib -lwrap .endd -in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is -&"exim"&. For example, the line +in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control +files is &"exim"&. For example, the line .code exim : LOCAL 192.168.1. .friendly.domain.example .endd in your &_/etc/hosts.allow_& file allows connections from the local host, from the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&. -All other connections are denied. Consult the &'tcpwrappers'& documentation for +All other connections are denied. The daemon name used by &'tcpwrappers'& +can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in +in &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the +configure file. Consult the &'tcpwrappers'& documentation for further details. - +.wen .section "Including support for IPv6" "SECID28" @@ -1935,6 +1946,36 @@ 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 @@ -2215,9 +2256,8 @@ but this usage is deprecated. .cindex "installing Exim" "what is not installed" Running &'make install'& does not copy the Exim 4 conversion script -&'convert4r4'&, or the &'pcretest'& test program. You will probably run the -first of these only once (if you are upgrading from Exim 3), and the second -isn't really part of Exim. None of the documentation files in the &_doc_& +&'convert4r4'&. You will probably run this only once if you are +upgrading from Exim 3. None of the documentation files in the &_doc_& directory are copied, except for the info files when you have set INFO_DIRECTORY, as described in section &<>& below. @@ -2599,6 +2639,13 @@ 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. +.new +.vitem &%--version%& +.oindex "&%--version%&" +This option is an alias for &%-bV%& and causes version information to be +displayed. +.wen + .vitem &%-B%&<&'type'&> .oindex "&%-B%&" .cindex "8-bit characters" @@ -2968,6 +3015,7 @@ 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: @@ -2981,6 +3029,11 @@ 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%&" @@ -3158,6 +3211,28 @@ above concerning senders and qualification do not apply. In this situation, Exim behaves in exactly the same way as it does when receiving a message via the listening daemon. +.new +.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. +.wen + .vitem &%-bt%& .oindex "&%-bt%&" .cindex "testing" "addresses" @@ -3209,7 +3284,7 @@ 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. @@ -3278,6 +3353,7 @@ 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. +.new .vitem &%-C%&&~<&'filelist'&> .oindex "&%-C%&" .cindex "configuration file" "alternate" @@ -3290,25 +3366,23 @@ 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 @@ -3328,7 +3402,9 @@ syntactically correct, but cannot be used for test deliveries, unless the 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. +.wen +.new .vitem &%-D%&<&'macro'&>=<&'value'&> .oindex "&%-D%&" .cindex "macro" "setting on command line" @@ -3338,6 +3414,14 @@ 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 @@ -3353,6 +3437,7 @@ example: exim '-D ABC = something' ... .endd &%-D%& may be repeated up to 10 times on a command line. +.wen .vitem &%-d%&<&'debug&~options'&> .oindex "&%-d%&" @@ -3731,15 +3816,13 @@ by an admin user. This option causes the contents of the message body (-D) spool file to be written to the standard output. This option can be used only by an admin user. -.new .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. -.wen .vitem &%-Mvh%&&~<&'message&~id'&> .oindex "&%-Mvh%&" @@ -4455,6 +4538,7 @@ most configurations, this specifies a single file. However, it is permitted to give a colon-separated list of file names, in which case Exim uses the first existing file in the list. +.new .cindex "EXIM_USER" .cindex "EXIM_GROUP" .cindex "CONFIGURE_OWNER" @@ -4462,17 +4546,21 @@ 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 @@ -4481,28 +4569,31 @@ configuration to a new file of that name if it did not previously exist. If CONFIGURE_FILE is a list, no default is automatically installed. Chapter &<>& is a &"walk-through"& discussion of the default configuration. - +.wen .section "Using a different configuration file" "SECID40" .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 @@ -4517,6 +4608,18 @@ 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. +.new +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_/.-]*$`& +.wen + 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 @@ -4556,13 +4659,11 @@ addresses and determine how the message is to be delivered (see chapters define mechanisms for copying messages to destinations (see chapters &<>&&--&<>&). .next -.new &'retry'&: Retry rules, for use when a message cannot be delivered immediately. If there is no retry section, or if it is empty (that is, no retry rules are defined), Exim will not retry deliveries. In this situation, temporary errors are treated the same as permanent errors. Retry rules are discussed in chapter &<>&. -.wen .next &'rewrite'&: Global address rewriting rules, for use when a message arrives and when new addresses are generated during delivery. Rewriting is discussed in @@ -4715,7 +4816,7 @@ 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 @@ -5821,11 +5922,9 @@ This causes any temporarily failing address to be retried every 15 minutes for 1.5 until 16 hours have passed, then every 6 hours up to 4 days. If an address is not delivered after 4 days of temporary failure, it is bounced. -.new If the retry section is removed from the configuration, or is empty (that is, if no retry rules are defined), Exim will not retry deliveries. This turns temporary errors into permanent errors. -.wen .section "Rewriting configuration" "SECID58" @@ -5884,6 +5983,10 @@ password are correct. In the examples it just produces an error message. To make the authenticators work, you can use a string expansion expression like one of the examples in &<>&. +Beware that the sequence of the parameters to PLAIN and LOGIN differ; the +usercode and password are in different positions. &<>& +covers both. + .ecindex IIDconfiwal @@ -5903,13 +6006,11 @@ 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 @@ -5948,47 +6049,6 @@ $ 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 &$2$&. - - - - - - . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -6151,7 +6211,6 @@ calls using the passwords from Courier's &_/etc/userdbshadow.dat_& file. Exim's utility program for creating DBM files (&'exim_dbmbuild'&) includes the zeros by default, but has an option to omit them (see section &<>&). .next -.new .cindex "lookup" "dsearch" .cindex "dsearch lookup type" &(dsearch)&: The given file must be a directory; this is searched for an entry @@ -6161,7 +6220,6 @@ the lookup is the name of the entry, which may be a file, directory, symbolic link, or any other kind of directory entry. An example of how this lookup can be used to support virtual domains is given in section &<>&. -.wen .next .cindex "lookup" "iplsearch" .cindex "iplsearch lookup type" @@ -6172,7 +6230,7 @@ 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 @@ -6664,6 +6722,18 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. +.cindex "TXT record" "in &(dnsdb)& lookup" +For TXT records with multiple items of data, only the first item is returned, +unless a separator for them is specified using a comma after the separator +character followed immediately by the TXT record item separator. To concatenate +items without a separator, use a semicolon instead. +.code +${lookup dnsdb{>\n,: txt=a.b.example}} +${lookup dnsdb{>\n; txt=a.b.example}} +.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 @@ -7154,9 +7224,9 @@ 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: @@ -7170,14 +7240,12 @@ option. Here is an example where two MySQL servers are listed: hide mysql_servers = localhost/users/root/secret:\ otherhost/users/root/othersecret .endd -.new For MySQL and PostgreSQL, a host may be specified as <&'name'&>:<&'port'&> but because this is a colon-separated list, the colon has to be doubled. For each query, these parameter groups are tried in order until a connection is made and a query is successfully processed. The result of a query may be that no data is found, but that is still a successful query. In other words, the list of servers provides a backup facility, not a list of different places to look. -.wen The &%quote_mysql%&, &%quote_pgsql%&, and &%quote_oracle%& expansion operators convert newline, tab, carriage return, and backspace to \n, \t, \r, and \b @@ -7187,7 +7255,6 @@ addition, escapes the percent and underscore characters. This cannot be done for MySQL because these escapes are not recognized in contexts where these characters are not special. -.new .section "Specifying the server in the query" "SECTspeserque" For MySQL and PostgreSQL lookups (but not currently for Oracle and InterBase), it is possible to specify a list of servers with an individual query. This is @@ -7219,15 +7286,14 @@ 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 -.wen .section "Special MySQL features" "SECID73" @@ -7594,7 +7660,6 @@ as set by the &%primary_hostname%& option (or defaulted). This makes it possible to use the same configuration file on several different hosts that differ only in their names. .next -.new .cindex "@[] in a domain list" .cindex "domain list" "matching local IP interfaces" .cindex "domain literal" @@ -7604,7 +7669,6 @@ only if that IP address is recognized as local for email routing purposes. The &%local_interfaces%& and &%extra_local_interfaces%& options can be used to control which of a host's several IP addresses are treated as local. In today's Internet, the use of domain literals is controversial. -.wen .next .cindex "@mx_any" .cindex "@mx_primary" @@ -7666,7 +7730,6 @@ list item such as &`*key.ex`& matches &'donkey.ex'& as well as &'cipher.key.ex'&. .next -.new .cindex "regular expressions" "in domain list" .cindex "domain list" "matching regular expression" If a pattern starts with a circumflex character, it is treated as a regular @@ -7676,7 +7739,6 @@ Email domains are case-independent, so this regular expression match is by default case-independent, but you can make it case-dependent by starting it with &`(?-i)`&. References to descriptions of the syntax of regular expressions are given in chapter &<>&. -.wen &*Warning*&: Because domain lists are expanded before being processed, you must escape any backslash and dollar characters in the regular expression, or @@ -7919,7 +7981,6 @@ mask, and this is used as the lookup key. For example, if the host's IP address is 192.168.34.6, the key that is looked up for the above example is &"192.168.34.0/24"&. -.new When an IPv6 address is converted to a string, dots are normally used instead of colons, so that keys in &(lsearch)& files need not contain colons (which terminate &(lsearch)& keys). This was implemented some time before the ability @@ -7934,7 +7995,6 @@ Ideally, it would be nice to tidy up this anomalous situation by changing to colons in all cases, given that quoting is now available for &(lsearch)&. However, this would be an incompatible change that might break some existing configurations. -.wen &*Warning*&: Specifying &%net32-%& (for an IPv4 address) or &%net128-%& (for an IPv6 address) is not the same as specifying just &%net-%& without a number. In @@ -7990,7 +8050,6 @@ the host name. For example, &`*.b.c`& matches all hosts whose names end in requirement. Other kinds of wildcarding require the use of a regular expression. .next -.new .cindex "regular expressions" "in host list" .cindex "host list" "regular expression in" If the item starts with &"^"& it is taken to be a regular expression which is @@ -7999,7 +8058,6 @@ expression match is by default case-independent, but you can make it case-dependent by starting it with &`(?-i)`&. References to descriptions of the syntax of regular expressions are given in chapter &<>&. For example, -.wen .code ^(a|b)\.c\.d$ .endd @@ -8027,10 +8085,8 @@ name (see section &<>&), or it may need to look up a host name from an IP address (see section &<>&). In either case, the behaviour when it fails to find the information it is seeking is the same. -.new &*Note*&: This section applies to permanent lookup failures. It does &'not'& apply to temporary DNS errors, whose handling is described in the next section. -.wen .cindex "&`+include_unknown`&" .cindex "&`+ignore_unknown`&" @@ -8066,7 +8122,6 @@ list. The effect of each one lasts until the next, or until the end of the list. -.new .section "Temporary DNS errors when looking up host information" &&& "SECTtemdnserr" .cindex "host" "lookup failures, temporary" @@ -8078,7 +8133,6 @@ host lists can include &`+ignore_defer`& and &`+include_defer`&, analagous to &`+ignore_unknown`& and &`+include_unknown`&, as described in the previous section. These options should be used with care, probably only in non-critical host lists such as whitelists. -.wen @@ -9631,6 +9685,34 @@ For single-key lookup types, no quoting is ever necessary and this operator yields an unchanged string. +.vitem &*${randint:*&<&'n'&>&*}*& +.cindex "random number" +This operator returns a somewhat random number which is less than the +supplied number and is at least 0. The quality of this randomness depends +on how Exim was built; the values are not suitable for keying material. +If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. +Otherwise, the implementation may be arc4random(), random() seeded by +srandomdev() or srandom(), or a custom implementation even weaker than +random(). + + +.new +.vitem &*${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} and ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3} +.endd +returns +.code +4.2.0.192 and 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 +.endd +.wen + + .vitem &*${rfc2047:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "expansion operator" @@ -9658,11 +9740,9 @@ bytes are replaced by question marks. Characters are converted into the character set defined by &%headers_charset%&. Overlong RFC 2047 &"words"& are not recognized unless &%check_rfc2047_length%& is set false. -.new &*Note*&: If you use &%$header%&_&'xxx'&&*:*& (or &%$h%&_&'xxx'&&*:*&) to access a header line, RFC 2047 decoding is done automatically. You do not need to use this operator as well. -.wen @@ -9794,6 +9874,37 @@ lower case), signifying multiplication by 1024 or 1024*1024, respectively. As a special case, the numerical value of an empty string is taken as zero. + +.new +.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. Leading and trailing whitespace is ignored. +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 +.wen + + +.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" @@ -9992,7 +10103,6 @@ The substring is first expanded, and then tested to see if it has the form of an IP address. Both IPv4 and IPv6 addresses are valid for &%isip%&, whereas &%isip4%& and &%isip6%& test specifically for IPv4 or IPv6 addresses. -.new For an IPv4 address, the test is for four dot-separated components, each of which consists of from one to three digits. For an IPv6 address, up to eight colon-separated components are permitted, each containing from one to four @@ -10007,7 +10117,6 @@ host names, or between IPv4 and IPv6 addresses. For example, you could use ${if isip4{$sender_host_address}... .endd to test which IP version an incoming SMTP connection is using. -.wen .vitem &*ldapauth&~{*&<&'ldap&~query'&>&*}*& .cindex "LDAP" "use for authentication" @@ -10247,6 +10356,10 @@ 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:$auth3}} +.endd .vitem &*queue_running*& .cindex "queue runner" "detecting when delivering from" .cindex "expansion" "queue runner test" @@ -10574,7 +10687,6 @@ This variable is available when Exim is compiled with the content-scanning extension and the obsolete &%demime%& condition. For details, see section &<>&. -.new .vitem &$dnslist_domain$& &&& &$dnslist_matched$& &&& &$dnslist_text$& &&& @@ -10588,7 +10700,6 @@ When a DNS (black) list lookup succeeds, these variables are set to contain the following data from the lookup: the list's domain name, the key that was looked up, the contents of any associated TXT record, and the value from the main A record. See section &<>& for more details. -.wen .vitem &$domain$& .vindex "&$domain$&" @@ -10782,7 +10893,7 @@ This is an obsolete name for &$received_port$&. .vitem &$item$& .vindex "&$item$&" This variable is used during the expansion of &*forall*& and &*forany*& -conditions (see section &<>&), and &*filter*&, &*man*&, and +conditions (see section &<>&), and &*filter*&, &*map*&, and &*reduce*& items (see section &<>&). In other circumstances, it is empty. @@ -10930,7 +11041,6 @@ This variable is available when Exim is compiled with the content-scanning extension. It is set to the name of the virus that was found when the ACL &%malware%& condition is true (see section &<>&). -.new .vitem &$max_received_linelength$& .vindex "&$max_received_linelength$&" .cindex "maximum" "line length" @@ -10938,7 +11048,6 @@ when the ACL &%malware%& condition is true (see section &<>&). This variable contains the number of bytes in the longest line that was received as part of the message, not counting the line termination character(s). -.wen .vitem &$message_age$& .cindex "message" "age of" @@ -10958,13 +11067,11 @@ being delivered, and is intended mainly for use in filter files. The maximum number of characters of the body that are put into the variable is set by the &%message_body_visible%& configuration option; the default is 500. -.new .oindex "&%message_body_newlines%&" By default, newlines are converted into spaces in &$message_body$&, to make it easier to search for phrases that might be split over a line break. However, this can be disabled by setting &%message_body_newlines%& to be true. Binary zeros are always converted into spaces. -.wen .vitem &$message_body_end$& .cindex "body of message" "expansion variable" @@ -11040,7 +11147,7 @@ precise size of the file that has been written. See also &$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$& contains the size supplied on the MAIL command, or -1 if no size was given. The value may not, of course, be truthful. @@ -11645,7 +11752,6 @@ This variable is set to &"1"& if a TLS certificate was verified when the message was received, and &"0"& otherwise. .vitem &$tls_cipher$& -.new .vindex "&$tls_cipher$&" When a message is received from a remote host over an encrypted SMTP connection, this variable is set to the cipher suite that was negotiated, for @@ -11660,16 +11766,15 @@ case, &$tls_cipher$& is cleared before any outgoing SMTP connection is made, and then set to the outgoing cipher suite if one is negotiated. See chapter &<>& for details of TLS support and chapter &<>& for details of the &(smtp)& transport. -.wen .vitem &$tls_peerdn$& .vindex "&$tls_peerdn$&" When a message is received from a remote host over an encrypted SMTP connection, and Exim is configured to request a certificate from the client, the value of the Distinguished Name of the certificate is made available in the -&$tls_peerdn$& during subsequent processing. &new("Like &$tls_cipher$&, the +&$tls_peerdn$& during subsequent processing. Like &$tls_cipher$&, the value is retained during message delivery, except during outbound SMTP -deliveries.") +deliveries. .vitem &$tod_bsdinbox$& .vindex "&$tod_bsdinbox$&" @@ -12212,7 +12317,7 @@ listed in more than one group. .row &%disable_ipv6%& "do no IPv6 processing" .row &%keep_malformed%& "for broken files &-- should not happen" .row &%localhost_number%& "for unique message ids in clusters" -.row &new(&%message_body_newlines%&) "retain newlines in &$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" @@ -12279,13 +12384,13 @@ listed in more than one group. .section "Data lookups" "SECID101" .table2 -.row &new(&%ibase_servers%&) "InterBase servers" +.row &%ibase_servers%& "InterBase servers" .row &%ldap_default_servers%& "used if no server in query" .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 @@ -12328,7 +12433,7 @@ 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" @@ -12356,6 +12461,7 @@ 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" @@ -12410,6 +12516,8 @@ listed in more than one group. .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 &%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" @@ -12563,7 +12671,7 @@ See also the &'Policy controls'& section above. .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" @@ -12815,7 +12923,7 @@ 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. @@ -13144,7 +13252,7 @@ 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 @@ -13409,6 +13517,10 @@ server. For details, see section &<>&. This option controls the protocols 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 headers_charset main string "see below" This option sets a default character set for translating from encoded MIME @@ -13480,10 +13592,10 @@ 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. @@ -13505,7 +13617,7 @@ 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" @@ -13561,8 +13673,8 @@ 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`& @@ -13628,13 +13740,11 @@ chapter &<>&, which contains a discussion about local network interfaces and recognizing the local host. -.new .option ibase_servers main "string list" unset .cindex "InterBase" "server list" This option provides a list of InterBase servers and associated connection data, to be used in conjunction with &(ibase)& lookups (see section &<>&). The option is available only if Exim has been built with InterBase support. -.wen @@ -13888,7 +13998,6 @@ this option is set greater than zero, any attempt to call &[getpwnam()]& with an argument that is longer behaves as if &[getpwnam()]& failed. -.new .option message_body_newlines main bool false .cindex "message body" "newlines in variables" .cindex "newline" "in message body variables" @@ -13897,7 +14006,6 @@ an argument that is longer behaves as if &[getpwnam()]& failed. By default, newlines in the message body are replaced by spaces when setting the &$message_body$& and &$message_body_end$& expansion variables. If this option is set true, this no longer happens. -.wen .option message_body_visible main integer 500 @@ -13969,6 +14077,16 @@ 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. +.new +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. +.wen + .option move_frozen_messages main boolean false .cindex "frozen messages" "moving" @@ -14021,6 +14139,38 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. +.new +.option openssl_options main "string list" +dont_insert_empty_fragments +.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. The default +value is one option which happens to have been set historically. You can +remove all options with: +.code +openssl_options = -all +.endd +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 by invoking Exim +with the &%-bV%& flag. + +An example: +.code +openssl_options = -all +microsoft_big_sslv3_buffer +.endd +.wen + + .option oracle_servers main "string list" unset .cindex "Oracle" "server list" This option provides a list of Oracle servers and associated connection data, @@ -14234,7 +14384,6 @@ causes Exim to behave as if &%queue_smtp_domains%& were set to &"*"& whenever .option queue_only_load main fixed-point unset -.new .cindex "load average" .cindex "queueing incoming messages" .cindex "message" "queueing by load" @@ -14244,7 +14393,6 @@ happens during local or remote SMTP input, all subsequent messages received on the same SMTP connection are queued by default, whatever happens to the load in the meantime, but this can be changed by setting &%queue_only_load_latch%& false. -.wen Deliveries will subsequently be performed by queue runner processes. This option has no effect on ancient operating systems on which Exim cannot @@ -14252,7 +14400,6 @@ determine the load average. See also &%deliver_queue_load_max%& and &%smtp_load_reserve%&. -.new .option queue_only_load_latch main boolean true .cindex "load average" "re-evaluating per message" When this option is true (the default), once one message has been queued @@ -14265,7 +14412,6 @@ circumstances such as very long-lived connections from scanning appliances where this is not the best strategy. In such cases, &%queue_only_load_latch%& should be set false. This causes the value of the load average to be re-evaluated for each message. -.wen .option queue_only_override main boolean true @@ -14628,7 +14774,6 @@ doing this processing, it cannot accept any other incoming connections. .option smtp_accept_queue main integer 0 -.new .cindex "SMTP" "incoming connection count" .cindex "queueing incoming messages" .cindex "message" "queueing by SMTP connection count" @@ -14638,7 +14783,6 @@ on the queue; no delivery processes are started automatically. The count is fixed at the start of an SMTP connection. It cannot be updated in the subprocess that receives messages, and so the queueing or not queueing applies to all messages received in the same connection. -.wen A value of zero implies no limit, and clearly any non-zero value is useful only if it is less than the &%smtp_accept_max%& value (unless that is zero). See @@ -15127,11 +15271,13 @@ contains the pipe command. This specifies the transport driver that is to be used when a &%mail%& command is used in a system filter. +.new .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, @@ -15139,8 +15285,8 @@ 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. +.wen .option tcp_nodelay main boolean true @@ -15285,6 +15431,13 @@ 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. + .option tls_verify_hosts main "host list&!!" unset .cindex "TLS" "client certificate verification" @@ -15295,7 +15448,6 @@ certificates from clients. The expected certificates are defined by either &%tls_verify_hosts%& or &%tls_try_verify_hosts%& is set and &%tls_verify_certificates%& is not set. -.new Any client that matches &%tls_verify_hosts%& is constrained by &%tls_verify_certificates%&. When the client initiates a TLS session, it must present one of the listed certificates. If it does not, the connection is @@ -15303,7 +15455,6 @@ aborted. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require the host to use TLS. It can still send SMTP commands through unencrypted connections. Forcing a client to use TLS has to be done separately using an ACL to reject inappropriate commands when the connection is not encrypted. -.wen A weaker form of checking is provided by &%tls_try_verify_hosts%&. If a client matches this option (but not &%tls_verify_hosts%&), Exim requests a @@ -15624,6 +15775,11 @@ 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). +.new +This option is unique in that multiple &%condition%& options may be present. +All &%condition%& options must succeed. +.wen + 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: @@ -15634,6 +15790,14 @@ Because of the default behaviour of the string expansion, this is equivalent to .code condition = ${if >{$message_age}{600}{true}{}} .endd +.new +A multiple condition example, which succeeds: +.code +condition = ${if >{$message_age}{600}} +condition = ${if !eq{${lc:$local_part}}{postmaster}} +condition = foobar +.endd +.wen 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%&. @@ -15954,14 +16118,12 @@ real_localuser: check_local_user transport = local_delivery .endd -.new For security, it would probably be a good idea to restrict the use of this router to locally-generated messages, using a condition such as this: .code condition = ${if match {$sender_host_address}\ {\N^(|127\.0\.0\.1)$\N}} .endd -.wen If both &%local_part_prefix%& and &%local_part_suffix%& are set for a router, both conditions must be met if not optional. Care must be taken if wildcards @@ -16071,7 +16233,6 @@ applies to all of them. .option pass_router routers string unset -.new .cindex "router" "go to after &""pass""&" Routers that recognize the generic &%self%& option (&(dnslookup)&, &(ipliteral)&, and &(manualroute)&) are able to return &"pass"&, forcing @@ -16082,7 +16243,6 @@ of another router. However (unlike &%redirect_router%&) the named router must be below the current router, to avoid loops. Note that this option applies only to the special case of &"pass"&. It does not apply when a router returns &"decline"& because it cannot handle an address. -.wen @@ -17898,10 +18058,10 @@ 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 @@ -18503,14 +18663,12 @@ real_localuser: local_part_prefix = real- transport = local_delivery .endd -.new For security, it would probably be a good idea to restrict the use of this router to locally-generated messages, using a condition such as this: .code condition = ${if match {$sender_host_address}\ {\N^(|127\.0\.0\.1)$\N}} .endd -.wen .option syntax_errors_text redirect string&!! unset @@ -19048,11 +19206,9 @@ 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 @@ -19805,10 +19961,8 @@ in which case it is: message_prefix = "From ${if def:return_path{$return_path}\ {MAILER-DAEMON}} $tod_bsdinbox\n" .endd -.new &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of &`\n`& to &`\r\n`& in &%message_prefix%&. -.wen .option message_suffix appendfile string&!! "see below" The string specified here is expanded and output at the end of every message. @@ -19818,10 +19972,8 @@ setting .code message_suffix = .endd -.new &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of &`\n`& to &`\r\n`& in &%message_suffix%&. -.wen .option mode appendfile "octal integer" 0600 If the output file is created, it is given this mode. If it already exists and @@ -20003,14 +20155,12 @@ This option causes lines to be terminated with the two-character CRLF sequence of batched SMTP, the byte sequence written to the file is then an exact image of what would be sent down a real SMTP connection. -.new &*Note:*& The contents of the &%message_prefix%& and &%message_suffix%& options (which are used to supply the traditional &"From&~"& and blank line separators in Berkeley-style mailboxes) are written verbatim, so must contain their own carriage return characters if these are needed. In cases where these options have non-empty defaults, the values end with a single linefeed, so they must be changed to end with &`\r\n`& if &%use_crlf%& is set. -.wen .option use_fcntl_lock appendfile boolean "see below" @@ -20701,8 +20851,8 @@ 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: @@ -21058,10 +21208,8 @@ setting .code message_prefix = .endd -.new &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of &`\n`& to &`\r\n`& in &%message_prefix%&. -.wen .option message_suffix pipe string&!! "see below" @@ -21071,10 +21219,8 @@ The suffix can be suppressed by setting .code message_suffix = .endd -.new &*Note:*& If you set &%use_crlf%& true, you must change any occurrences of &`\n`& to &`\r\n`& in &%message_suffix%&. -.wen .option path pipe string "see below" @@ -21088,6 +21234,19 @@ sought in the PATH directories, in the usual way. &*Warning*&: This does not apply to a command specified as a transport filter. +.new +.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. +.wen + + .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 @@ -21184,13 +21343,11 @@ This option causes lines to be terminated with the two-character CRLF sequence of batched SMTP, the byte sequence written to the pipe is then an exact image of what would be sent down a real SMTP connection. -.new The contents of the &%message_prefix%& and &%message_suffix%& options are written verbatim, so must contain their own carriage return characters if these are needed. When &%use_bsmtp%& is not set, the default values for both &%message_prefix%& and &%message_suffix%& end with a single linefeed, so their values must be changed to end with &`\r\n`& if &%use_crlf%& is set. -.wen .option use_shell pipe boolean false @@ -21230,6 +21387,7 @@ procmail_pipe: envelope_to_add check_string = "From " escape_string = ">From " + umask = 077 user = $local_part group = mail @@ -21337,7 +21495,6 @@ that are in force when the &%helo_data%&, &%hosts_try_auth%&, &%interface%&, &%serialize_hosts%&, and the various TLS options are expanded. -.new .section "Use of $tls_cipher and $tls_peerdn" "usecippeer" .vindex &$tls_cipher$& .vindex &$tls_peerdn$& @@ -21349,7 +21506,6 @@ variables are emptied. If TLS is subsequently started, they are set to the appropriate values for the outgoing connection, and these are the values that are in force when any authenticators are run and when the &%authenticated_sender%& option is expanded. -.wen .section "Private options for smtp" "SECID146" @@ -21386,12 +21542,10 @@ forced to fail, the option is ignored. Other expansion failures cause delivery to be deferred. If the result of expansion is an empty string, that is also ignored. -.new The expansion happens after the outgoing connection has been made and TLS started, if required. This means that the &$host$&, &$host_address$&, &$tls_cipher$&, and &$tls_peerdn$& variables are set according to the particular connection. -.wen If the SMTP session is not authenticated, the expansion of &%authenticated_sender%& still happens (and can cause the delivery to be @@ -21533,18 +21687,23 @@ being used, names are looked up using &[gethostbyname()]& instead of using the DNS. Of course, that function may in fact use the DNS, but it may also consult other sources of information such as &_/etc/hosts_&. -.option gnutls_require_kx main string unset +.option gnutls_require_kx smtp string unset This option controls the key exchange mechanisms when GnuTLS is used in an Exim client. For details, see section &<>&. -.option gnutls_require_mac main string unset +.option gnutls_require_mac smtp string unset This option controls the MAC algorithms when GnuTLS is used in an Exim client. For details, see section &<>&. -.option gnutls_require_protocols main string unset +.option gnutls_require_protocols smtp string unset This option controls the protocols when GnuTLS is used in an Exim client. For details, see section &<>&. +.option gnutls_compat_mode smtp boolean unset +This option controls whether GnuTLS is used in compatibility mode in an Exim +server. This reduces security slightly, but improves interworking with older +implementations of TLS. + .option helo_data smtp string&!! "see below" .cindex "HELO" "argument, setting" .cindex "EHLO" "argument, setting" @@ -21715,8 +21874,8 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter .vindex "&$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 @@ -22479,7 +22638,6 @@ can be done on the rewritten addresses. .chapter "Retry configuration" "CHAPretry" .scindex IIDretconf1 "retry" "configuration, description of" .scindex IIDregconf2 "configuration file" "retry section" -.new The &"retry"& section of the runtime configuration file contains a list of retry rules that control how often Exim tries to deliver messages that cannot be delivered at the first attempt. If there are no retry rules (the section is @@ -22488,7 +22646,6 @@ errors are treated as permanent. The default configuration contains a single, general-purpose retry rule (see section &<>&). The &%-brt%& command line option can be used to test which retry rule will be used for a given address, domain and error. -.wen The most common cause of retries is temporary failure to deliver to a remote host because the host is down, or inaccessible because of a network problem. @@ -23134,7 +23291,6 @@ in Exim. .cindex "authentication" "generic options" .cindex "options" "generic; for authenticators" -.new .option client_condition authenticators string&!! unset When Exim is authenticating as a client, it skips any authenticator whose &%client_condition%& expansion yields &"0"&, &"no"&, or &"false"&. This can be @@ -23146,7 +23302,6 @@ client_condition = ${if !eq{$tls_cipher}{}} (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.) -.wen .option driver authenticators string unset @@ -23634,18 +23789,20 @@ 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="cn=${quote_ldap_dn:$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" @@ -23906,7 +24063,7 @@ 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, @@ -23939,7 +24096,7 @@ dovecot_plain: driver = dovecot public_name = PLAIN server_socket = /var/run/dovecot/auth-client - server_set_id = $auth1 + server_set_id = $auth2 dovecot_ntlm: driver = dovecot @@ -24164,11 +24321,11 @@ sections &<>& and &<>&. .section "GnuTLS parameter computation" "SECID181" -GnuTLS uses RSA and D-H parameters that may take a substantial amount of time +GnuTLS uses D-H parameters that may take a substantial amount of time to compute. It is unreasonable to re-compute them for every TLS session. Therefore, Exim keeps this data in a file in its spool directory, called &_gnutls-params_&. The file is owned by the Exim user and is readable only by -its owner. Every Exim process that start up GnuTLS reads the RSA and D-H +its owner. Every Exim process that start up GnuTLS reads the D-H parameters from this file. If the file does not exist, the first Exim process that needs it computes the data and writes it to a temporary file which is renamed once it is complete. It does not matter if several Exim processes do @@ -24413,17 +24570,15 @@ incoming message (by default &-- you can, of course, change this), and it is also included in the log line that records a message's arrival, keyed by &"X="&, unless the &%tls_cipher%& log selector is turned off. The &%encrypted%& condition can be used to test for specific cipher suites in ACLs. -&new("(For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section -&<>&.)") +(For outgoing SMTP deliveries, &$tls_cipher$& is reset &-- see section +&<>&.) -.new Once TLS has been established, the ACLs that run for subsequent SMTP commands can check the name of the cipher suite and vary their actions accordingly. The cipher suite names vary, depending on which TLS library is being used. For example, OpenSSL uses the name DES-CBC3-SHA for the cipher suite which in other contexts is known as TLS_RSA_WITH_3DES_EDE_CBC_SHA. Check the OpenSSL or GnuTLS documentation for more details. -.wen .section "Requesting and verifying client certificates" "SECID183" @@ -24524,13 +24679,10 @@ 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 @@ -24542,6 +24694,12 @@ 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$&" All the TLS options in the &(smtp)& transport are expanded before use, with @@ -24549,7 +24707,6 @@ All the TLS options in the &(smtp)& transport are expanded before use, with which the client is connected. Forced failure of an expansion causes Exim to behave as if the relevant option were unset. -.new .vindex &$tls_cipher$& .vindex &$tls_peerdn$& Before an SMTP connection is established, the &$tls_cipher$& and &$tls_peerdn$& @@ -24557,7 +24714,6 @@ variables are emptied. (Until the first connection, they contain the values that were set when the message was received.) If STARTTLS is subsequently successfully obeyed, these variables are set to the relevant values for the outgoing connection. -.wen @@ -24738,7 +24894,7 @@ options in the main part of the configuration. These options are: .irow &%acl_smtp_mail%& "ACL for MAIL" .irow &%acl_smtp_mailauth%& "ACL for the AUTH parameter of MAIL" .irow &%acl_smtp_mime%& "ACL for content-scanning MIME parts" -.irow &new(&%acl_smtp_notquit%&) "ACL for non-QUIT terminations" +.irow &%acl_smtp_notquit%& "ACL for non-QUIT terminations" .irow &%acl_smtp_predata%& "ACL at start of DATA command" .irow &%acl_smtp_quit%& "ACL for QUIT" .irow &%acl_smtp_rcpt%& "ACL for RCPT" @@ -24847,6 +25003,19 @@ and try again later, but that is their problem, though it does waste some of your resources. +.new +.section "The SMTP DKIM ACL" "SECTDKIMACL" +The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support +enabled (which is the default). + +The ACL test specified by &%acl_smtp_dkim%& happens after a message has been +received, and is executed for each DKIM signature found in a message. If not +otherwise specified, the default action is to accept. + +For details on the operation of DKIM, see chapter &<>&. +.wen + + .section "The SMTP MIME ACL" "SECID194" The &%acl_smtp_mime%& option is available only when Exim is compiled with the content-scanning extension. For details, see chapter &<>&. @@ -24878,10 +25047,9 @@ client are given temporary error responses until QUIT is received or the connection is closed. In these special cases, the QUIT ACL does not run. - -.new .section "The not-QUIT ACL" "SECTNOTQUITACL" -The not-QUIT ACL, specified by &%smtp_notquit_acl%&, is run in most cases when +.vindex &$acl_smtp_notquit$& +The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when an SMTP session ends without sending QUIT. However, when Exim itself is is bad trouble, such as being unable to write to its log files, this ACL is not run, because it might try to do things (such as write to log files) that make the @@ -24914,7 +25082,6 @@ With the exception of the &`acl-drop`& case, the default message can be overridden by the &%message%& modifier in the not-QUIT ACL. In the case of a &%drop%& verb in another ACL, it is the message from the other ACL that is used. -.wen .section "Finding an ACL to use" "SECID195" @@ -25194,7 +25361,7 @@ 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. @@ -25584,7 +25751,8 @@ 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'&> @@ -25744,6 +25912,25 @@ warn control = caseful_local_part Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. +.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 + .vitem &*control&~=&~enforce_sync*& &&& &*control&~=&~no_enforce_sync*& .cindex "SMTP" "synchronization checking" @@ -25879,7 +26066,7 @@ 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). @@ -25892,7 +26079,7 @@ 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 @@ -25921,12 +26108,12 @@ 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 @@ -26430,7 +26617,9 @@ 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 : \ @@ -26591,10 +26780,8 @@ dnslists = sbl.spahmaus.org/<|192.168.2.3|192.168.5.6|... Thus, this example checks whether or not the IP addresses of the sender domain's mail servers are on the Spamhaus black list. -.new The key that was used for a successful DNS list lookup is put into the variable &$dnslist_matched$& (see section &<>&). -.wen @@ -26620,7 +26807,6 @@ see section &<>& for details of how they are checked. .section "Variables set from DNS lists" "SECID204" -.new .cindex "expansion" "variables, set from DNS list" .cindex "DNS list" "variables set from" .vindex "&$dnslist_domain$&" @@ -26646,7 +26832,6 @@ deny dnslists = spamhaus.example/<|192.168.1.2|192.168.6.7|... .endd If this condition succeeds, the value in &$dnslist_matched$& might be &`192.168.6.7`& (for example). -.wen If more than one address record is returned by the DNS lookup, all the IP addresses are included in &$dnslist_value$&, separated by commas and spaces. @@ -26926,7 +27111,7 @@ parameter &'m'& is the maximum number of messages that a client is permitted to send in each time interval. It also specifies the number of messages permitted in a fast burst. By increasing both &'m'& and &'p'& but keeping &'m/p'& constant, you can allow a client to send more messages in a burst without -changing its overall sending rate limit. Conversely, if &'m'& and &'p'& are +changing its long-term sending rate limit. Conversely, if &'m'& and &'p'& are both small, messages must be sent at an even rate. There is a script in &_util/ratelimit.pl_& which extracts sending rates from @@ -26935,36 +27120,33 @@ when deploying the &%ratelimit%& ACL condition. The script prints usage instructions when it is run with no arguments. The key is used to look up the data for calculating the client's average -sending rate. This data is stored in a database maintained by Exim in its spool -directory, alongside the retry and other hints databases. The default key is -&$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$& is only meaningful if the client has -authenticated, and you can check with the &%authenticated%& ACL condition. +authenticated (which you can check with the &%authenticated%& ACL condition). -.new -If you want to limit the rate at which a recipient receives messages, you can -use the key &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in -a RCPT ACL. -.wen +The lookup key does not have to identify clients: If you want to limit the +rate at which a recipient receives messages, you can use the key +&`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT +ACL. -Internally, Exim includes the smoothing constant &'p'& and the options in the +Internally, Exim appends the smoothing constant &'p'& and the options onto 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. -.new 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. -.wen .section "Ratelimit options for what is being measured" "ratoptmea" The &%per_conn%& option limits the client's connection rate. @@ -26974,16 +27156,17 @@ the default if none of the &%per_*%& options is specified. The &%per_byte%& option limits the sender's email bandwidth. Note that it is best to use this option in the DATA ACL; if it is used in an earlier ACL it -relies on the SIZE parameter on the MAIL command, which may be inaccurate or -completely missing. You can follow the limit &'m'& in the configuration with K, -M, or G to specify limits in kilobytes, megabytes, or gigabytes, respectively. +relies on the SIZE parameter specified 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. 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%& +the number of recipients is incremented by the &%$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. @@ -27002,17 +27185,18 @@ counter-measures (such as rejecting the message) that may be specified by the rest of the ACL. The default mode is leaky, which avoids a sender's over-aggressive retry rate preventing it from getting any email through. -The &%strict%& option means that the client's recorded rate is always updated. -The effect of this is that Exim measures the client's average rate of attempts -to send email, which can be much higher than the maximum &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: +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 until it slows down below the maximum rate. If +the client stops attempting to send email for the time specified in the &'p'& +parameter then its computed rate will decay exponentially to 37% of its peak +value. 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) + 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 @@ -27064,7 +27248,6 @@ this means that Exim will lose its hints data after a reboot (including retry hints, the callout cache, and ratelimit data). -.new .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 @@ -27076,7 +27259,7 @@ 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 + deny ratelimit = 100 / 5m / strict / per_cmd / noupdate log_message = RATE: $sender_rate/$sender_rate_period \ (max $sender_rate_limit) .endd @@ -27093,7 +27276,6 @@ acl_check_mail: In this example, the rate is tested and used to deny access (when it is too high) in the connect ACL, but the actual computation of the remembered rate happens later, on a per-command basis, in another ACL. -.wen @@ -27672,19 +27854,8 @@ the third string (in this case &"1"&), whether or not the cryptographic and timeout checks succeed. The &$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 @@ -27882,7 +28053,7 @@ 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 @@ -27906,8 +28077,16 @@ 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. @@ -28047,6 +28226,11 @@ If your virus scanner cannot unpack MIME and TNEF containers itself, you should use the &%demime%& condition (see section &<>&) before the &%malware%& condition. +.new +Beware the interaction of Exim's &%message_size_limit%& with any size limits +imposed by your anti-virus scanner. +.wen + Here is a very simple scanning example: .code deny message = This message contains malware ($malware_name) @@ -28123,6 +28307,10 @@ 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: @@ -28163,11 +28351,12 @@ SpamAssassin profile has been matched or exceeded. If you want to use the &%spam%& condition for its side effects (see the variables below), you can make it always return &"true"& by appending &`:true`& to the username. +.new .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. +.wen .vlist .vitem &$spam_score$& @@ -28176,11 +28365,10 @@ 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 @@ -28193,14 +28381,15 @@ 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 @@ -28243,7 +28432,7 @@ 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. @@ -28796,23 +28985,19 @@ out the values of all the &[local_scan()]& options. .section "Available Exim variables" "SECID208" -.new .cindex "&[local_scan()]& function" "available Exim variables" The header &_local_scan.h_& gives you access to a number of C variables. These are the only ones that are guaranteed to be maintained from release to release. Note, however, that you can obtain the value of any Exim expansion variable, including &$recipients$&, by calling &'expand_string()'&. The exported C variables are as follows: -.wen .vlist .vitem &*int&~body_linecount*& -.new This variable contains the number of lines in the message's body. .vitem &*int&~body_zerocount*& This variable contains the number of binary zero bytes in the message's body. -.wen .vitem &*unsigned&~int&~debug_selector*& This variable is set to zero when no debugging is taking place. Otherwise, it @@ -30383,8 +30568,8 @@ 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. @@ -30870,8 +31055,8 @@ 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 @@ -33722,15 +33907,26 @@ 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. +.new +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. +.wen +.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. @@ -33786,11 +33982,13 @@ 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%&" @@ -34047,6 +34245,13 @@ 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 @@ -34393,13 +34598,270 @@ unqualified domain &'foundation'&. .ecindex IIDforspo2 .ecindex IIDforspo3 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&& + "DKIM Support" +.cindex "DKIM" + +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: +.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 &%$dkim_key_nosubdomaining%& +"1" if the key record forbids subdomaining, "0" otherwise. +.vitem &%$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 &%$dkim_cur_signer%&). This is typically used to restrict an ACL +verb to a group of domains or identities. For example: + +.code +# Warn when message apparently from GMail has no signature at all +warn log_message = GMail sender without DKIM signature + sender_domains = gmail.com + dkim_signers = gmail.com + dkim_status = none +.endd + +.vitem &%dkim_status%& +ACL condition that checks a colon-separated list of possible DKIM verification +results agains the actual result of verification. This is typically used +to restrict an ACL verb to a list of verification outcomes, like: + +.code +deny message = Message from Paypal with invalid or missing signature + sender_domains = paypal.com:paypal.de + dkim_signers = paypal.com:paypal.de + dkim_status = none:invalid:fail +.endd + +The possible status keywords are: 'none','invalid','fail' and 'pass'. Please +see the documentation of the &%$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"