X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/71e1673fc67e46389d29b88b2e8930f5294ea380..8332bd723731cee805a58ed9f2c29f2472d63836:/doc/doc-docbook/spec.xfpt?ds=sidebyside diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index c9bafdd74..c1f845eaf 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1,5 +1,3 @@ -. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.64 2009/10/27 14:42:57 nm4 Exp $ -. . ///////////////////////////////////////////////////////////////////////////// . This is the primary source of the Exim Manual. It is an xfpt document that is . converted into DocBook XML for subsequent conversion into printing and online @@ -47,8 +45,8 @@ . the element must also be updated for each new edition. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.69" -.set version "4.70" +.set previousversion "4.75" +.set version "4.77" .set ACL "access control lists (ACLs)" .set I "    " @@ -172,17 +170,15 @@ Specification of the Exim Mail Transfer Agent The Exim MTA -27 October 2009 -PhilipHazel -PH -University of Cambridge Computing Service -
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
+06 May 2011 +EximMaintainers +EM - 4.70 - 27 October 2009 - PH + 4.77 + 10 Oct 2011 + EM -2009University of Cambridge +2011University of Cambridge .literal off @@ -368,6 +364,7 @@ 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. @@ -471,10 +468,10 @@ first to check that you are not duplicating a previous entry. The following Exim mailing lists exist: .table2 140pt +.row &'exim-announce@exim.org'& "Moderated, low volume announcements list" .row &'exim-users@exim.org'& "General discussion list" .row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc." -.row &'exim-announce@exim.org'& "Moderated, low volume announcements list" -.row &'exim-future@exim.org'& "Discussion of long-term development" +.row &'exim-cvs@exim.org'& "Automated commit messages from the VCS" .endtable You can subscribe to these lists, change your existing subscriptions, and view @@ -728,14 +725,12 @@ 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 -.new 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). -.wen .next .cindex "cdb" "acknowledgment" Support for the cdb (Constant DataBase) lookup method is provided by code @@ -1548,7 +1543,6 @@ If a host is unreachable for a period of time, a number of messages may be waiting for it by the time it recovers, and sending them in a single SMTP connection is clearly beneficial. Whenever a delivery to a remote host is deferred, - .cindex "hints database" Exim makes a note in its hints database, and whenever a successful SMTP delivery has happened, it looks to see if any other messages are waiting @@ -1558,7 +1552,6 @@ one connection. - .section "Permanent delivery failure" "SECID21" .cindex "delivery" "permanent failure" .cindex "bounce message" "when generated" @@ -1875,6 +1868,14 @@ SUPPORT_TLS=yes TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto TLS_INCLUDE=-I/usr/local/openssl/include/ .endd +.new +.cindex "pkg-config" "OpenSSL" +If you have &'pkg-config'& available, then instead you can just use: +.code +SUPPORT_TLS=yes +USE_OPENSSL_PC=openssl +.endd +.wen .cindex "USE_GNUTLS" If GnuTLS is installed, you should set .code @@ -1890,6 +1891,16 @@ USE_GNUTLS=yes TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt TLS_INCLUDE=-I/usr/gnu/include .endd +.new +.cindex "pkg-config" "GnuTLS" +If you have &'pkg-config'& available, then instead you can just use: +.code +SUPPORT_TLS=yes +USE_GNUTLS=yes +USE_GNUTLS_PC=gnutls +.endd +.wen + You do not need to set TLS_INCLUDE if the relevant directory is already specified in INCLUDE. Details of how to configure Exim to make use of TLS are given in chapter &<>&. @@ -1898,8 +1909,11 @@ given in chapter &<>&. .section "Use of tcpwrappers" "SECID27" + .cindex "tcpwrappers, building Exim to support" .cindex "USE_TCP_WRAPPERS" +.cindex "TCP_WRAPPERS_DAEMON_NAME" +.cindex "tcp_wrappers_daemon_name" Exim can be linked with the &'tcpwrappers'& library in order to check incoming SMTP calls using the &'tcpwrappers'& control files. This may be a convenient alternative to Exim's own checking facilities for installations that are @@ -1914,18 +1928,20 @@ USE_TCP_WRAPPERS=yes CFLAGS=-O -I/usr/local/include EXTRALIBS_EXIM=-L/usr/local/lib -lwrap .endd -in &_Local/Makefile_&. The name to use in the &'tcpwrappers'& control files is -&"exim"&. For example, the line +in &_Local/Makefile_&. The daemon name to use in the &'tcpwrappers'& control +files is &"exim"&. For example, the line .code exim : LOCAL 192.168.1. .friendly.domain.example .endd in your &_/etc/hosts.allow_& file allows connections from the local host, from the subnet 192.168.1.0/24, and from all hosts in &'friendly.domain.example'&. -All other connections are denied. Consult the &'tcpwrappers'& documentation for +All other connections are denied. The daemon name used by &'tcpwrappers'& +can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in +in &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the +configure file. Consult the &'tcpwrappers'& documentation for further details. - .section "Including support for IPv6" "SECID28" .cindex "IPv6" "including support for" Exim contains code for use on systems that have IPv6 support. Setting @@ -1945,6 +1961,36 @@ support has not been tested for some time. +.section "Dynamically loaded lookup module support" "SECTdynamicmodules" +.cindex "lookup modules" +.cindex "dynamic modules" +.cindex ".so building" +On some platforms, Exim supports not compiling all lookup types directly into +the main binary, instead putting some into external modules which can be loaded +on demand. +This permits packagers to build Exim with support for lookups with extensive +library dependencies without requiring all users to install all of those +dependencies. +Most, but not all, lookup types can be built this way. + +Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be +installed; Exim will only load modules from that directory, as a security +measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined +for your OS; see &_OS/Makefile-Linux_& for an example. +Some other requirements for adjusting &`EXTRALIBS`& may also be necessary, +see &_src/EDITME_& for details. + +Then, for each module to be loaded dynamically, define the relevant +&`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes". +For example, this will build in lsearch but load sqlite and mysql support +on demand: +.code +LOOKUP_LSEARCH=yes +LOOKUP_SQLITE=2 +LOOKUP_MYSQL=2 +.endd + + .section "The building process" "SECID29" .cindex "build directory" Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been @@ -2082,6 +2128,28 @@ files or libraries are required. When a lookup type is not included in the binary, attempts to configure Exim to use it cause run time configuration errors. +.new +.cindex "pkg-config" "lookups" +.cindex "pkg-config" "authenticators" +Many systems now use a tool called &'pkg-config'& to encapsulate information +about how to compile against a library; Exim has some initial support for +being able to use pkg-config for lookups and authenticators. For any given +makefile variable which starts &`LOOKUP_`& or &`AUTH_`&, you can add a new +variable with the &`_PC`& suffix in the name and assign as the value the +name of the package to be queried. The results of querying via the +&'pkg-config'& command will be added to the appropriate Makefile variables +with &`+=`& directives, so your version of &'make'& will need to support that +syntax. For instance: +.code +LOOKUP_SQLITE=yes +LOOKUP_SQLITE_PC=sqlite3 +AUTH_GSASL=yes +AUTH_GSASL_PC=libgsasl +AUTH_HEIMDAL_GSSAPI=yes +AUTH_HEIMDAL_GSSAPI_PC=heimdal-gssapi +.endd +.wen + .cindex "Perl" "including support for" Exim can be linked with an embedded Perl interpreter, allowing Perl subroutines to be called during string expansion. To enable this facility, @@ -2223,14 +2291,12 @@ configuration. (If a default alias file is created, its name &'is'& modified.) For backwards compatibility, ROOT is used if DESTDIR is not set, but this usage is deprecated. -.new .cindex "installing Exim" "what is not installed" Running &'make install'& does not copy the Exim 4 conversion script &'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. -.wen For the utility programs, old versions are renamed by adding the suffix &_.O_& to their names. The Exim binary itself, however, is handled differently. It is @@ -2610,6 +2676,11 @@ This option causes Exim to output a few sentences stating what it is. The same output is generated if the Exim binary is called with no options and no arguments. +.vitem &%--version%& +.oindex "&%--version%&" +This option is an alias for &%-bV%& and causes version information to be +displayed. + .vitem &%-B%&<&'type'&> .oindex "&%-B%&" .cindex "8-bit characters" @@ -2993,13 +3064,11 @@ using one of the words &%router_list%&, &%transport_list%&, or settings can be obtained by using &%routers%&, &%transports%&, or &%authenticators%&. -.new .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. -.wen .vitem &%-bp%& .oindex "&%-bp%&" @@ -3177,6 +3246,26 @@ 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. +.vitem &%-bmalware%&&~<&'filename'&> +.oindex "&%-bmalware%&" +.cindex "testing", "malware" +.cindex "malware scan test" +This debugging option causes Exim to scan the given file, +using the malware scanning framework. The option of &%av_scanner%& influences +this option, so if &%av_scanner%&'s value is dependent upon an expansion then +the expansion should have defaults which apply to this invocation. ACLs are +not invoked, so if &%av_scanner%& references an ACL variable then that variable +will never be populated and &%-bmalware%& will fail. + +Exim will have changed working directory before resolving the filename, so +using fully qualified pathnames is advisable. Exim will be running as the Exim +user when it tries to open the file, rather than as the invoking user. +This option requires admin privileges. + +The &%-bmalware%& option will not be extended to be more generally useful, +there are better tools for file-scanning. This option exists to help +administrators verify their Exim and AV scanner configuration. + .vitem &%-bt%& .oindex "&%-bt%&" .cindex "testing" "addresses" @@ -3228,7 +3317,7 @@ 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. @@ -3309,25 +3398,23 @@ 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 @@ -3348,6 +3435,7 @@ caller is privileged, or unless it is an exotic configuration that does not require privilege. No check is made on the owner or group of the files specified by this option. + .vitem &%-D%&<&'macro'&>=<&'value'&> .oindex "&%-D%&" .cindex "macro" "setting on command line" @@ -3357,6 +3445,14 @@ 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 @@ -3373,6 +3469,7 @@ exim '-D ABC = something' ... .endd &%-D%& may be repeated up to 10 times on a command line. + .vitem &%-d%&<&'debug&~options'&> .oindex "&%-d%&" .cindex "debugging" "list of selectors" @@ -3753,7 +3850,7 @@ written to the standard output. This option can be used only by an admin user. .vitem &%-Mvc%&&~<&'message&~id'&> .oindex "&%-Mvc%&" .cindex "message" "listing in RFC 2822 format" -.cindex "listing" "message in RFC 2922 format" +.cindex "listing" "message in RFC 2822 format" This option causes a copy of the complete message (header lines plus body) to be written to the standard output in RFC 2822 format. This option can be used only by an admin user. @@ -4479,17 +4576,21 @@ 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 @@ -4505,21 +4606,24 @@ configuration. .cindex "configuration file" "alternate" A one-off alternate configuration can be specified by the &%-C%& command line option, which may specify a single file or a list of files. However, when -&%-C%& is used, Exim gives up its root privilege, unless called by root or the -Exim user (or unless the argument for &%-C%& is identical to the built-in value -from CONFIGURE_FILE). &%-C%& is useful mainly for checking the syntax of -configuration files before installing them. No owner or group checks are done -on a configuration file specified by &%-C%&. - -The privileged use of &%-C%& by the Exim user can be locked out by setting -ALT_CONFIG_ROOT_ONLY in &_Local/Makefile_& when building Exim. However, -if you do this, you also lock out the possibility of testing a -configuration using &%-C%& right through message reception and delivery, even -if the caller is root. The reception works, but by that time, Exim is running -as the Exim user, so when it re-execs to regain privilege for the delivery, the -use of &%-C%& causes privilege to be lost. However, root can test reception and -delivery using two separate commands (one to put a message on the queue, using -&%-odq%&, and another to do the delivery, using &%-M%&). +&%-C%& is used, Exim gives up its root privilege, unless called by root (or +unless the argument for &%-C%& is identical to the built-in value from +CONFIGURE_FILE), or is listed in the TRUSTED_CONFIG_LIST file and the caller +is the Exim user or the user specified in the CONFIGURE_OWNER setting. &%-C%& +is useful mainly for checking the syntax of configuration files before +installing them. No owner or group checks are done on a configuration file +specified by &%-C%&, if root privilege has been dropped. + +Even the Exim user is not trusted to specify an arbitrary configuration file +with the &%-C%& option to be used with root privileges, unless that file is +listed in the TRUSTED_CONFIG_LIST file. This locks out the possibility of +testing a configuration using &%-C%& right through message reception and +delivery, even if the caller is root. The reception works, but by that time, +Exim is running as the Exim user, so when it re-execs to regain privilege for +the delivery, the use of &%-C%& causes privilege to be lost. However, root +can test reception and delivery using two separate commands (one to put a +message on the queue, using &%-odq%&, and another to do the delivery, using +&%-M%&). If ALT_CONFIG_PREFIX is defined &_in Local/Makefile_&, it specifies a prefix string with which any file named in a &%-C%& command line option must @@ -4534,6 +4638,16 @@ non-privileged user causes Exim to discard its root privilege. If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is completely disabled, and its use causes an immediate error exit. +The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder +to declare certain macro names trusted, such that root privilege will not +necessarily be discarded. +WHITELIST_D_MACROS defines a colon-separated list of macros which are +considered safe and, if &%-D%& only supplies macros from this list, and the +values are acceptable, then Exim will not give up root privilege if the caller +is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a +transition mechanism and is expected to be removed in the future. Acceptable +values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`& + Some sites may wish to use the same Exim binary on different machines that share a file system, but to use different configuration files on each machine. If CONFIGURE_FILE_USE_NODE is defined in &_Local/Makefile_&, Exim first @@ -5897,11 +6011,9 @@ 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 &<>&. -.new Beware that the sequence of the parameters to PLAIN and LOGIN differ; the usercode and password are in different positions. &<>& covers both. -.wen .ecindex IIDconfiwal @@ -5921,14 +6033,12 @@ regular expressions is discussed in many Perl reference books, and also in Jeffrey Friedl's &'Mastering Regular Expressions'&, which is published by O'Reilly (see &url(http://www.oreilly.com/catalog/regex2/)). -.new The documentation for the syntax and semantics of the regular expressions that 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. -.wen 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 @@ -6113,13 +6223,26 @@ using Berkeley DB versions 3 or 4, it opens existing databases for reading with the DB_UNKNOWN option. This enables it to handle any of the types of database that the library supports, and can be useful for accessing DBM files created by other applications. (For earlier DB versions, DB_HASH is always used.) +.new +.next +.cindex "lookup" "dbmjz" +.cindex "lookup" "dbm &-- embedded NULs" +.cindex "sasldb2" +.cindex "dbmjz lookup type" +&(dbmjz)&: This is the same as &(dbm)&, except that the lookup key is +interpreted as an Exim list; the elements of the list are joined together with +ASCII NUL characters to form the lookup key. An example usage would be to +authenticate incoming SMTP calls using the passwords from Cyrus SASL's +&_/etc/sasldb2_& file with the &(gsasl)& authenticator or Exim's own +&(cram_md5)& authenticator. +.wen .next .cindex "lookup" "dbmnz" .cindex "lookup" "dbm &-- terminating zero" .cindex "binary zero" "in lookup key" .cindex "Courier" .cindex "&_/etc/userdbshadow.dat_&" -.cindex "dmbnz lookup type" +.cindex "dbmnz lookup type" &(dbmnz)&: This is the same as &(dbm)&, except that a terminating binary zero is not included in the key that is passed to the DBM library. You may need this if you want to look up data in files that are created by or shared with some @@ -6640,6 +6763,18 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. +.cindex "TXT record" "in &(dnsdb)& lookup" +For TXT records with multiple items of data, only the first item is returned, +unless a separator for them is specified using a comma after the separator +character followed immediately by the TXT record item separator. To concatenate +items without a separator, use a semicolon instead. +.code +${lookup dnsdb{>\n,: txt=a.b.example}} +${lookup dnsdb{>\n; txt=a.b.example}} +.endd +It is permitted to specify a space as the separator character. Further +white space is ignored. + .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" By default, both the preference value and the host name are returned for @@ -6784,6 +6919,10 @@ The URL may begin with &`ldap`& or &`ldaps`& if your LDAP library supports secure (encrypted) LDAP connections. The second of these ensures that an encrypted TLS connection is used. +With sufficiently modern LDAP libraries, Exim supports forcing TLS over regular +LDAP connections, rather than the SSL-on-connect &`ldaps`&. +See the &%ldap_start_tls%& option. + .section "LDAP quoting" "SECID68" .cindex "LDAP" "quoting" @@ -7693,7 +7832,7 @@ pattern must be an appropriate query for the lookup type, as described in chapter &<>&. For example: .code hold_domains = mysql;select domain from holdlist \ - where domain = '$domain'; + where domain = '${quote_mysql:$domain}'; .endd In most cases, the data that is looked up is not used (so for an SQL query, for example, it doesn't matter what field you select). Exim is interested only in @@ -8397,6 +8536,13 @@ start of a portion of the string that is interpreted and replaced as described below in section &<>& onwards. Backslash is used as an escape character, as described in the following section. +Whether a string is expanded depends upon the context. Usually this is solely +dependent upon the option for which a value is sought; in this documentation, +options for which string expansion is performed are marked with † after +the data type. ACL rules always expand strings. A couple of expansion +conditions do not expand some of the brace-delimited branches, for security +reasons. + .section "Literal text in expanded strings" "SECTlittext" @@ -9591,6 +9737,32 @@ For single-key lookup types, no quoting is ever necessary and this operator yields an unchanged string. +.vitem &*${randint:*&<&'n'&>&*}*& +.cindex "random number" +This operator returns a somewhat random number which is less than the +supplied number and is at least 0. The quality of this randomness depends +on how Exim was built; the values are not suitable for keying material. +If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. +Otherwise, the implementation may be arc4random(), random() seeded by +srandomdev() or srandom(), or a custom implementation even weaker than +random(). + + +.vitem &*${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 ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3} +.endd +returns +.code +4.2.0.192 and 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 +.endd + + .vitem &*${rfc2047:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "expansion operator" @@ -9752,23 +9924,41 @@ 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 +In all cases, a relative comparator OP is testing if <&'string1'&> OP +<&'string2'&>; the above example is checking if &$message_size$& is larger than +10M, not if 10M is larger than &$message_size$&. + + .vitem &*bool&~{*&<&'string'&>&*}*& .cindex "expansion" "boolean parsing" .cindex "&%bool%& expansion condition" This condition turns a string holding a true or false representation into a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"& (case-insensitively); also positive integer numbers map to true if non-zero, -false if zero. Leading whitespace is ignored. +false if zero. +An empty string is treated as false. +Leading and trailing whitespace is ignored; +thus a string consisting only of whitespace is false. All other string values will result in expansion failure. When combined with ACL variables, this expansion condition will let you make decisions in one place and act on those decisions in another place. -For example, +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" @@ -9956,6 +10146,25 @@ string is lexically greater than the second string. For &%gt%& the comparison includes the case of letters, whereas for &%gti%& the comparison is case-independent. +.new +.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& + &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& +.cindex "string" "comparison" +.cindex "list" "iterative conditions" +Both strings are expanded; the second string is treated as a list of simple +strings; if the first string is a member of the second, then the condition +is true. + +These are simpler to use versions of the more powerful &*forany*& condition. +Examples, and the &*forany*& equivalents: +.code +${if inlist{needle}{foo:needle:bar}} + ${if forany{foo:needle:bar}{eq{$item}{needle}}} +${if inlisti{Needle}{fOo:NeeDLE:bAr}} + ${if forany{fOo:NeeDLE:bAr}{eqi{$item}{Needle}}} +.endd +.wen + .vitem &*isip&~{*&<&'string'&>&*}*& &&& &*isip4&~{*&<&'string'&>&*}*& &&& &*isip6&~{*&<&'string'&>&*}*& @@ -10066,10 +10275,12 @@ See &*match_local_part*&. .vitem &*match_ip&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "&%match_ip%& expansion condition" +.new This condition matches an IP address to a list of IP address patterns. It must be followed by two argument strings. The first (after expansion) must be an IP -address or an empty string. The second (after expansion) is a restricted host +address or an empty string. The second (not expanded) is a restricted host list that can match only an IP address, not a host name. For example: +.wen .code ${if match_ip{$sender_host_address}{1.2.3.4:5.6.7.8}{...}{...}} .endd @@ -10115,6 +10326,11 @@ just as easy to use the fact that a lookup is itself a condition, and write: .endd .endlist ilist +.new +Note that <&'string2'&> is not itself subject to string expansion, unless +Exim was built with the EXPAND_LISTMATCH_RHS option. +.wen + Consult section &<>& for further details of these patterns. .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& @@ -10142,6 +10358,11 @@ item can be used, as in all address lists, to cause subsequent items to have their local parts matched casefully. Domains are always matched caselessly. +.new +Note that <&'string2'&> is not itself subject to string expansion, unless +Exim was built with the EXPAND_LISTMATCH_RHS option. +.wen + &*Note*&: Host lists are &'not'& supported in this way. This is because hosts have two identities: a name and an IP address, and it is not clear how to specify cleanly how such a test would work. However, IP addresses can be @@ -10221,12 +10442,10 @@ configuration, you might have this: .code server_condition = ${if pwcheck{$auth1:$auth2}} .endd -.new Again, for a PLAIN authenticator configuration, this would be: .code server_condition = ${if pwcheck{$auth2:$auth3}} .endd -.wen .vitem &*queue_running*& .cindex "queue runner" "detecting when delivering from" .cindex "expansion" "queue runner test" @@ -10489,6 +10708,15 @@ is empty and &$authentication_failed$& is set to &"1"&). Failure includes any negative response to an AUTH command, including (for example) an attempt to use an undefined mechanism. +.new +.vitem &$av_failed$& +.cindex "content scanning" "AV scanner failure" +This variable is available when Exim is compiled with the content-scanning +extension. It is set to &"0"& by default, but will be set to &"1"& if any +problem occurs with the virus scanner (specified by &%av_scanner%&) during +the ACL malware condition. +.wen + .vitem &$body_linecount$& .cindex "message body" "line count" .cindex "body of message" "line count" @@ -10502,7 +10730,7 @@ number of lines in the message's body. See also &$message_linecount$&. .cindex "binary zero" "in message body" .vindex "&$body_zerocount$&" When a message is being received or delivered, this variable contains the -number of binary zero bytes in the message's body. +number of binary zero bytes (ASCII NULs) in the message's body. .vitem &$bounce_recipient$& .vindex "&$bounce_recipient$&" @@ -10990,8 +11218,15 @@ number of lines received. Before delivery happens (that is, before filters, routers, and transports run) the count is increased to include the &'Received:'& header line that Exim standardly adds, and also any other header lines that are added by ACLs. The blank line that separates the message header -from the body is not counted. Here is an example of the use of this variable in -a DATA ACL: +from the body is not counted. + +As with the special case of &$message_size$&, during the expansion of the +appendfile transport's maildir_tag option in maildir format, the value of +&$message_linecount$& is the precise size of the number of newlines in the +file that has been written (minus one for the blank line between the +header and the body). + +Here is an example of the use of this variable in a DATA ACL: .code deny message = Too many lines in message header condition = \ @@ -11013,12 +11248,10 @@ doing a delivery in maildir format, the value of &$message_size$& is the precise size of the file that has been written. See also &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&. -.new .cindex "RCPT" "value of &$message_size$&" While running a per message ACL (mail/rcpt/predata), &$message_size$& contains the size supplied on the MAIL command, or -1 if no size was given. The value may not, of course, be truthful. -.wen .vitem &$mime_$&&'xxx'& A number of variables whose names start with &$mime$& are @@ -11615,6 +11848,16 @@ command in a filter file. Its use is explained in the description of that command, which can be found in the separate document entitled &'Exim's interfaces to mail filtering'&. +.new +.vitem &$tls_bits$& +.vindex "&$tls_bits$&" +Contains an approximation of the TLS cipher's bit-strength; the meaning of +this depends upon the TLS implementation used. +If TLS has not been negotiated, the value will be 0. +The value of this is automatically fed into the Cyrus SASL authenticator +when acting as a server, to specify the "external SSF" (a SASL term). +.wen + .vitem &$tls_certificate_verified$& .vindex "&$tls_certificate_verified$&" This variable is set to &"1"& if a TLS certificate was verified when the @@ -12254,7 +12497,14 @@ listed in more than one group. .section "Data lookups" "SECID101" .table2 .row &%ibase_servers%& "InterBase servers" +.row &%ldap_ca_cert_dir%& "dir of CA certs to verify LDAP server's" +.row &%ldap_ca_cert_file%& "file of CA certs to verify LDAP server's" +.row &%ldap_cert_file%& "client cert file for LDAP" +.row &%ldap_cert_key%& "client key file for LDAP" +.row &%ldap_cipher_suite%& "TLS negotiation preference control" .row &%ldap_default_servers%& "used if no server in query" +.row &%ldap_require_cert%& "action to take without LDAP server cert" +.row &%ldap_start_tls%& "require TLS within LDAP" .row &%ldap_version%& "set protocol version" .row &%lookup_open_max%& "lookup files held open" .row &%mysql_servers%& "default MySQL servers" @@ -12330,6 +12580,7 @@ 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" @@ -12385,6 +12636,7 @@ listed in more than one group. .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" @@ -12532,6 +12784,7 @@ See also the &'Policy controls'& section above. .row &%dns_ipv4_lookup%& "only v4 lookup for these domains" .row &%dns_retrans%& "parameter for resolver" .row &%dns_retry%& "parameter for resolver" +.row &%dns_use_edns0%& "parameter for resolver" .row &%hold_domains%& "hold delivery for these domains" .row &%local_interfaces%& "for routing checks" .row &%queue_domains%& "no immediate delivery for these" @@ -12784,17 +13037,17 @@ saying &"keep on trying, even though there are big problems"&. &%ignore_bounce_errors_after%&. It is retained for compatibility, but it is not thought to be very useful any more, and its use should probably be avoided. + .option av_scanner main string "see below" This option is available if Exim is built with the content-scanning extension. It specifies which anti-virus scanner to use. The default value is: .code sophie:/var/run/sophie .endd -If the value of &%av_scanner%& starts with dollar character, it is expanded +If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. See section &<>& for further details. - .option bi_command main string unset .oindex "&%-bi%&" This option supplies the name of a command that is run when Exim is called with @@ -12897,7 +13150,7 @@ section &<>& for details of the caching. This option defines the &"random"& local part that can be used as part of callout verification. The default value is .code -$primary_host_name-$tod_epoch-testing +$primary_hostname-$tod_epoch-testing .endd See section &<>& for details of how this value is used. @@ -13164,6 +13417,19 @@ to set in them. See &%dns_retrans%& above. +.new +.option dns_use_edns0 main integer -1 +.cindex "DNS" "resolver options" +.cindex "DNS" "EDNS0" +If this option is set to a non-negative number then Exim will initialise the +DNS resolver library to either use or not use EDNS0 extensions, overriding +the system default. A value of 0 coerces EDNS0 off, a value of 1 coerces EDNS0 +on. + +If the resolver library does not support EDNS0 then this option has no effect. +.wen + + .option drop_cr main boolean false This is an obsolete option that is now a no-op. It used to affect the way Exim handled CR and LF characters in incoming messages. What happens now is @@ -13384,12 +13650,10 @@ server. For details, see section &<>&. This option controls the protocols when GnuTLS is used in an Exim server. For details, see section &<>&. -.new .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. -.wen .option headers_charset main string "see below" This option sets a default character set for translating from encoded MIME @@ -13464,7 +13728,7 @@ to do more extensive checking of the data supplied by these commands. The ACL 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. @@ -13486,7 +13750,7 @@ 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" @@ -13542,8 +13806,8 @@ 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`& @@ -13665,6 +13929,46 @@ next attempt to deliver such a message, it gets removed. The incident is logged. +.option ldap_ca_cert_dir main string unset +.cindex "LDAP", "TLS CA certificate directory" +This option indicates which directory contains CA certificates for verifying +a TLS certificate presented by an LDAP server. +While Exim does not provide a default value, your SSL library may. +Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP +and constrained to be a directory. + + +.option ldap_ca_cert_file main string unset +.cindex "LDAP", "TLS CA certificate file" +This option indicates which file contains CA certificates for verifying +a TLS certificate presented by an LDAP server. +While Exim does not provide a default value, your SSL library may. +Analogous to &%tls_verify_certificates%& but as a client-side option for LDAP +and constrained to be a file. + + +.option ldap_cert_file main string unset +.cindex "LDAP" "TLS client certificate file" +This option indicates which file contains an TLS client certificate which +Exim should present to the LDAP server during TLS negotiation. +Should be used together with &%ldap_cert_key%&. + + +.option ldap_cert_key main string unset +.cindex "LDAP" "TLS client key file" +This option indicates which file contains the secret/private key to use +to prove identity to the LDAP server during TLS negotiation. +Should be used together with &%ldap_cert_file%&, which contains the +identity to be proven. + + +.option ldap_cipher_suite main string unset +.cindex "LDAP" "TLS cipher suite" +This controls the TLS cipher-suite negotiation during TLS negotiation with +the LDAP server. See &<>& for more details of the format of +cipher-suite options with OpenSSL (as used by LDAP client libraries). + + .option ldap_default_servers main "string list" unset .cindex "LDAP" "default servers" This option provides a list of LDAP servers which are tried in turn when an @@ -13673,6 +13977,25 @@ details of LDAP queries. This option is available only when Exim has been built with LDAP support. +.option ldap_require_cert main string unset. +.cindex "LDAP" "policy for LDAP server TLS cert presentation" +This should be one of the values "hard", "demand", "allow", "try" or "never". +A value other than one of these is interpreted as "never". +See the entry "TLS_REQCERT" in your system man page for ldap.conf(5). +Although Exim does not set a default, the LDAP library probably defaults +to hard/demand. + + +.option ldap_start_tls main boolean false +.cindex "LDAP" "whether or not to negotiate TLS" +If set, Exim will attempt to negotiate TLS with the LDAP server when +connecting on a regular LDAP port. This is the LDAP equivalent of SMTP's +"STARTTLS". This is distinct from using "ldaps", which is the LDAP form +of SSL-on-connect. +In the event of failure to negotiate TLS, the action taken is controlled +by &%ldap_require_cert%&. + + .option ldap_version main integer unset .cindex "LDAP" "protocol version, forcing" This option can be used to force Exim to set a specific protocol version for @@ -13946,6 +14269,18 @@ an oversized message is logged in both the main and the reject logs. See also the generic transport option &%message_size_limit%&, which limits the size of message that an individual transport can process. +If you use a virus-scanner and set this option to to a value larger than the +maximum size that your virus-scanner is configured to support, you may get +failures triggered by large mails. The right size to configure for the +virus-scanner depends upon what data is passed and the options in use but it's +probably safest to just set it to a little larger than this value. Eg, with a +default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M, +some problems may result. + +A value of 0 will disable size limit checking; Exim will still advertise the +SIZE extension in an EHLO response, but without a limit, so as to permit +SMTP clients to still indicate the message size along with the MAIL verb. + .option move_frozen_messages main boolean false .cindex "frozen messages" "moving" @@ -13998,6 +14333,36 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. +.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 + + .option oracle_servers main "string list" unset .cindex "Oracle" "server list" This option provides a list of Oracle servers and associated connection data, @@ -15098,11 +15463,13 @@ contains the pipe command. This specifies the transport driver that is to be used when a &%mail%& command is used in a system filter. + .option system_filter_user main string unset .cindex "uid (user id)" "system filter" -If this option is not set, the system filter is run in the main Exim delivery -process, as root. When the option is set, the system filter runs in a separate -process, as the given user. Unless the string consists entirely of digits, it +If this option is set to root, the system filter is run in the main Exim +delivery process, as root. Otherwise, the system filter runs in a separate +process, as the given user, defaulting to the Exim run-time user. +Unless the string consists entirely of digits, it is looked up in the password data. Failure to find the named user causes a configuration error. The gid is either taken from the password data, or specified by &%system_filter_group%&. When the uid is specified numerically, @@ -15110,8 +15477,7 @@ specified by &%system_filter_group%&. When the uid is specified numerically, If the system filter generates any pipe, file, or reply deliveries, the uid under which the filter is run is used when transporting them, unless a -transport option overrides. Normally you should set &%system_filter_user%& if -your system filter generates these kinds of delivery. +transport option overrides. .option tcp_nodelay main boolean true @@ -15256,6 +15622,13 @@ 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" @@ -15593,6 +15966,9 @@ router is skipped, and the address is offered to the next one. If the result is any other value, the router is run (as this is the last precondition to be evaluated, all the other preconditions must be true). +This option is unique in that multiple &%condition%& options may be present. +All &%condition%& options must succeed. + The &%condition%& option provides a means of applying custom conditions to the running of routers. Note that in the case of a simple conditional expansion, the default expansion values are exactly what is wanted. For example: @@ -15603,12 +15979,19 @@ Because of the default behaviour of the string expansion, this is equivalent to .code condition = ${if >{$message_age}{600}{true}{}} .endd + +A multiple condition example, which succeeds: +.code +condition = ${if >{$message_age}{600}} +condition = ${if !eq{${lc:$local_part}}{postmaster}} +condition = foobar +.endd + If the expansion fails (other than forced failure) delivery is deferred. Some of the other precondition options are common special cases that could in fact be specified using &%condition%&. - .option debug_print routers string&!! unset .cindex "testing" "variables in drivers" If this option is set and debugging is enabled (see the &%-d%& command line @@ -17863,12 +18246,10 @@ redirection items of the form :defer: :fail: .endd -.new 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: -.wen .code X.Employee: :fail: Gone away, no forwarding address .endd @@ -19012,12 +19393,10 @@ destination. The process that writes the message to the filter, the filter itself, and the original process that reads the result and delivers it are all run in parallel, like a shell pipeline. -.new The filter can perform any transformations it likes, but of course should take 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. -.wen .cindex "content scanning" "per user" A transport filter can be used to provide content-scanning on a per-user basis @@ -19688,13 +20067,16 @@ This option applies only to deliveries in maildir format, and is described in section &<>& below. -.option maildir_use_size_file appendfile boolean false +.new +.option maildir_use_size_file appendfile&!! boolean false .cindex "maildir format" "&_maildirsize_& file" -Setting this option true enables support for &_maildirsize_& files. Exim +The result of string expansion for this option must be a valid boolean value. +If it is true, it enables support for &_maildirsize_& files. Exim creates a &_maildirsize_& file in a maildir if one does not exist, taking the quota from the &%quota%& option of the transport. If &%quota%& is unset, the value is zero. See &%maildir_quota_directory_regex%& above and section &<>& below for further details. +.wen .option maildirfolder_create_regex appendfile string unset .cindex "maildir format" "&_maildirfolder_& file" @@ -19895,6 +20277,7 @@ The regular expression should not assume that the length is at the end of the file name (even though &%maildir_tag%& puts it there) because maildir MUAs sometimes add other information onto the ends of message file names. +Section &<>& contains further information. .option quota_warn_message appendfile string&!! "see below" @@ -20309,6 +20692,7 @@ tag is added to its name. However, if adding the tag takes the length of the name to the point where the test &[stat()]& call fails with ENAMETOOLONG, the tag is dropped and the maildir file is created with no tag. + .vindex "&$message_size$&" Tags can be used to encode the size of files in their names; see &%quota_size_regex%& above for an example. The expansion of &%maildir_tag%& @@ -20318,8 +20702,19 @@ forced to fail, the tag is ignored, but a non-forced failure causes delivery to be deferred. The expanded tag may contain any printing characters except &"/"&. Non-printing characters in the string are ignored; if the resulting string is empty, it is ignored. If it starts with an alphanumeric character, a leading -colon is inserted. +colon is inserted; this default has not proven to be the path that popular +maildir implementations have chosen (but changing it in Exim would break +backwards compatibility). +For one common implementation, you might set: +.code +maildir_tag = ,S=${message_size} +.endd +but you should check the documentation of the other software to be sure. + +It is advisable to also set &%quota_size_regex%& when setting &%maildir_tag%& +as this allows Exim to extract the size from your tag, instead of having to +&[stat()]& each message file. .section "Using a maildirsize file" "SECID136" @@ -20745,9 +21140,14 @@ later"&. In this case, delivery is deferred. Details of a permanent failure are logged, but are not included in the bounce message, which merely contains &"local delivery failed"&. +If the command exits on a signal and the &%freeze_signal%& option is set then +the message will be frozen in the queue. If that option is not set, a bounce +will be sent as normal. + If the return code is greater than 128 and the command being run is a shell script, it normally means that the script was terminated by a signal whose -value is the return code minus 128. +value is the return code minus 128. The &%freeze_signal%& option does not +apply in this case. If Exim is unable to run the command (that is, if &[execve()]& fails), the return code is set to 127. This is the value that a shell returns if it is @@ -20956,6 +21356,14 @@ is set, failure to exec is treated specially, and causes the message to be frozen, whatever the setting of &%ignore_status%&. +.option freeze_signal pipe boolean false +.cindex "signal exit" +.cindex "&(pipe)& transport", "signal exit" +Normally if the process run by a command in a pipe transport exits on a signal, +a bounce message is sent. If &%freeze_signal%& is set, the message will be +frozen in Exim's queue instead. + + .option ignore_status pipe boolean false If this option is true, the status returned by the subprocess that is set up to run the command is ignored, and Exim behaves as if zero had been returned. @@ -21043,6 +21451,17 @@ sought in the PATH directories, in the usual way. &*Warning*&: This does not apply to a command specified as a transport filter. +.option permit_coredump pipe boolean false +Normally Exim inhibits core-dumps during delivery. If you have a need to get +a core-dump of a pipe command, enable this command. This enables core-dumps +during delivery and affects both the Exim binary and the pipe command run. +It is recommended that this option remain off unless and until you have a need +for it and that this only be enabled when needed, as the risk of excessive +resource consumption can be quite high. Note also that Exim is typically +installed as a setuid binary and most operating systems will inhibit coredumps +of these by default, so further OS-specific action may be required. + + .option pipe_as_creator pipe boolean false .cindex "uid (user id)" "local delivery" If the generic &%user%& option is not set and this option is true, the delivery @@ -21183,6 +21602,7 @@ procmail_pipe: envelope_to_add check_string = "From " escape_string = ">From " + umask = 077 user = $local_part group = mail @@ -21482,24 +21902,22 @@ being used, names are looked up using &[gethostbyname()]& instead of using the DNS. Of course, that function may in fact use the DNS, but it may also consult other sources of information such as &_/etc/hosts_&. -.option gnutls_require_kx main string unset +.option gnutls_require_kx smtp string unset This option controls the key exchange mechanisms when GnuTLS is used in an Exim client. For details, see section &<>&. -.option gnutls_require_mac main string unset +.option gnutls_require_mac smtp string unset This option controls the MAC algorithms when GnuTLS is used in an Exim client. For details, see section &<>&. -.option gnutls_require_protocols main string unset +.option gnutls_require_protocols smtp string unset This option controls the protocols when GnuTLS is used in an Exim client. For details, see section &<>&. -.new -.option gnutls_compat_mode main boolean unset +.option gnutls_compat_mode smtp boolean unset This option controls whether GnuTLS is used in compatibility mode in an Exim server. This reduces security slightly, but improves interworking with older implementations of TLS. -.wen .option helo_data smtp string&!! "see below" .cindex "HELO" "argument, setting" @@ -21750,12 +22168,22 @@ is deferred. .option protocol smtp string smtp .cindex "LMTP" "over TCP/IP" +.cindex "ssmtp protocol" "outbound" +.cindex "TLS" "SSL-on-connect outbound" +.vindex "&$port$&" If this option is set to &"lmtp"& instead of &"smtp"&, the default value for the &%port%& option changes to &"lmtp"&, and the transport operates the LMTP protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local deliveries into closed message stores. Exim also has support for running LMTP over a pipe to a local process &-- see chapter &<>&. +.new +If this option is set to &"smtps"&, the default vaule for the &%port%& option +changes to &"smtps"&, and the transport initiates TLS immediately after +connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. +The Internet standards bodies strongly discourage use of this mode. +.wen + .option retry_include_ip_address smtp boolean true Exim normally includes both the host name and the IP address in the key it @@ -23042,15 +23470,29 @@ included by setting .code AUTH_CRAM_MD5=yes AUTH_CYRUS_SASL=yes +.new +AUTH_DOVECOT=yes +AUTH_GSASL=yes +AUTH_HEIMDAL_GSSAPI=yes +.wen AUTH_PLAINTEXT=yes AUTH_SPA=yes .endd in &_Local/Makefile_&, respectively. The first of these supports the CRAM-MD5 authentication mechanism (RFC 2195), and the second provides an interface to -the Cyrus SASL authentication library. The third can be configured to support +the Cyrus SASL authentication library. +.new +The third is an interface to Dovecot's authentication system, delegating the +work via a socket interface. +The fourth provides an interface to the GNU SASL authentication library, which +provides mechanisms but typically not data sources. +The fifth provides direct access to Heimdal GSSAPI, geared for Kerberos, but +supporting setting a server keytab. +The sixth can be configured to support the PLAIN authentication mechanism (RFC 2595) or the LOGIN mechanism, which is -not formally documented, but used by several MUAs. The fourth authenticator +not formally documented, but used by several MUAs. The seventh authenticator supports Microsoft's &'Secure Password Authentication'& mechanism. +.wen The authenticators are configured using the same syntax as other drivers (see section &<>&). If no authenticators are required, no @@ -23082,6 +23524,30 @@ The remainder of this chapter covers the generic options for the authenticators, followed by general discussion of the way authentication works in Exim. +.new +&*Beware:*& the meaning of &$auth1$&, &$auth2$&, ... varies on a per-driver and +per-mechanism basis. Please read carefully to determine which variables hold +account labels such as usercodes and which hold passwords or other +authenticating data. + +Note that some mechanisms support two different identifiers for accounts: the +&'authentication id'& and the &'authorization id'&. The contractions &'authn'& +and &'authz'& are commonly encountered. The American spelling is standard here. +Conceptually, authentication data such as passwords are tied to the identifier +used to authenticate; servers may have rules to permit one user to act as a +second user, so that after login the session is treated as though that second +user had logged in. That second user is the &'authorization id'&. A robust +configuration might confirm that the &'authz'& field is empty or matches the +&'authn'& field. Often this is just ignored. The &'authn'& can be considered +as verified data, the &'authz'& as an unverified request which the server might +choose to honour. + +A &'realm'& is a text string, typically a domain name, presented by a server +to a client to help it select an account and credentials to use. In some +mechanisms, the client and server provably agree on the realm, but clients +typically can not treat the realm as secure data to be blindly trusted. +.wen + .section "Generic options for authenticators" "SECID168" @@ -23128,6 +23594,11 @@ This option must be set for a &%plaintext%& server authenticator, where it is used directly to control authentication. See section &<>& for details. +.new +For the &(gsasl)& authenticator, this option is required for various +mechanisms; see chapter &<>& for details. +.wen + For the other authenticators, &%server_condition%& can be used as an additional authentication or authorization mechanism that is applied after the other authenticator conditions succeed. If it is set, it is expanded when the @@ -23586,14 +24057,13 @@ login: driver = plaintext public_name = LOGIN server_prompts = Username:: : Password:: - server_condition = ${if and{{ + 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=$auth1,ou=people,o=example.org .endd -.new We have to check that the username is not empty before using it, because LDAP does not permit empty DN components. We must also use the &%quote_ldap_dn%& operator to correctly quote the DN for authentication. However, the basic @@ -23601,7 +24071,6 @@ operator to correctly quote the DN for authentication. However, the basic correct one to use for the password, because quoting is needed only to make the password conform to the Exim syntax. At the LDAP level, the password is an uninterpreted string. -.wen .section "Support for different kinds of authentication" "SECID174" @@ -23734,6 +24203,20 @@ lookup_cram: Note that this expansion explicitly forces failure if the lookup fails because &$auth1$& contains an unknown user name. +.new +As another example, if you wish to re-use a Cyrus SASL sasldb2 file without +using the relevant libraries, you need to know the realm to specify in the +lookup and then ask for the &"userPassword"& attribute for that user in that +realm, with: +.code +cyrusless_crammd5: + driver = cram_md5 + public_name = CRAM-MD5 + server_secret = ${lookup{$auth1:mail.example.org:userPassword}\ + dbmjz{/etc/sasldb2}} + server_set_id = $auth1 +.endd +.wen .section "Using cram_md5 as a client" "SECID177" .cindex "options" "&(cram_md5)& authenticator (client)" @@ -23807,10 +24290,17 @@ be set in &_exim.conf_& in your SASL directory. If you are using GSSAPI for Kerberos, note that because of limitations in the GSSAPI interface, changing the server keytab might need to be communicated down to the Kerberos layer independently. The mechanism for doing so is dependent upon the Kerberos -implementation. For example, for Heimdal, the environment variable KRB5_KTNAME +implementation. +.new +For example, for older releases of Heimdal, the environment variable KRB5_KTNAME may be set to point to an alternative keytab file. Exim will pass this variable through from its own inherited environment when started as root or the Exim user. The keytab file needs to be readable by the Exim user. +With newer releases of Heimdal, a setuid Exim may cause Heimdal to discard the +environment variable. In practice, for those releases, the Cyrus authenticator +is not a suitable interface for GSSAPI (Kerberos) support. Instead, consider +the &(heimdal_gssapi)& authenticator, described in chapter &<>& +.wen .section "Using cyrus_sasl as a server" "SECID178" @@ -23841,8 +24331,10 @@ sasl: server_set_id = $auth1 .endd -.option server_realm cyrus_sasl string unset +.new +.option server_realm cyrus_sasl string&!! unset This specifies the SASL realm that the server claims to be in. +.wen .option server_service cyrus_sasl string &`smtp`& @@ -23913,6 +24405,217 @@ who authenticated is placed in &$auth1$&. .ecindex IIDdcotauth2 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// +.new +.chapter "The gsasl authenticator" "CHAPgsasl" +.scindex IIDgsaslauth1 "&(gsasl)& authenticator" +.scindex IIDgsaslauth2 "authenticators" "&(gsasl)&" +.cindex "authentication" "GNU SASL" +.cindex "authentication" "SASL" +.cindex "authentication" "EXTERNAL" +.cindex "authentication" "ANONYMOUS" +.cindex "authentication" "PLAIN" +.cindex "authentication" "LOGIN" +.cindex "authentication" "DIGEST-MD5" +.cindex "authentication" "CRAM-MD5" +.cindex "authentication" "SCRAM-SHA-1" +The &(gsasl)& authenticator provides server integration for the GNU SASL +library and the mechanisms it provides. This is new as of the 4.78 release +and there are a few areas where the library does not let Exim smoothly +scale to handle future authentication mechanisms, so no guarantee can be +made that any particular new authentication mechanism will be supported +without code changes in Exim. + + +.option server_channelbinding gsasl bool false +Some authentication mechanisms are able to use external context at both ends +of the session to bind the authentication to that context, and fail the +authentication process if that context differs. Specifically, some TLS +ciphersuites can provide identifying information about the cryptographic +context. + +This means that certificate identity and verification becomes a non-issue, +as a man-in-the-middle attack will cause the correct client and server to +see different identifiers and authentication will fail. + +This is currently only supported when using the GnuTLS library. This is +only usable by mechanisms which support "channel binding"; at time of +writing, that's the SCRAM family. + +This defaults off to ensure smooth upgrade across Exim releases, in case +this option causes some clients to start failing. Some future release +of Exim may switch the default to be true. + + +.option server_hostname gsasl string&!! "see below" +This option selects the hostname that is used when communicating with the +library. The default value is &`$primary_hostname`&. +Some mechanisms will use this data. + + +.option server_mech gsasl string "see below" +This option selects the authentication mechanism this driver should use. The +default is the value of the generic &%public_name%& option. This option allows +you to use a different underlying mechanism from the advertised name. For +example: +.code +sasl: + driver = gsasl + public_name = X-ANYTHING + server_mech = CRAM-MD5 + server_set_id = $auth1 +.endd + + +.option server_password gsasl string&!! unset +Various mechanisms need access to the cleartext password on the server, so +that proof-of-possession can be demonstrated on the wire, without sending +the password itself. + +The data available for lookup varies per mechanism. +In all cases, &$auth1$& is set to the &'authentication id'&. +The &$auth2$& variable will always be the &'authorization id'& (&'authz'&) +if available, else the empty string. +The &$auth3$& variable will always be the &'realm'& if available, +else the empty string. + +A forced failure will cause authentication to defer. + +If using this option, it may make sense to set the &%server_condition%& +option to be simply "true". + + +.option server_realm gsasl string&!! unset +This specifies the SASL realm that the server claims to be in. +Some mechanisms will use this data. + + +.option server_scram_iter gsasl string&!! unset +This option provides data for the SCRAM family of mechanisms. +&$auth1$& is not available at evaluation time. +(This may change, as we receive feedback on use) + + +.option server_scram_salt gsasl string&!! unset +This option provides data for the SCRAM family of mechanisms. +&$auth1$& is not available at evaluation time. +(This may change, as we receive feedback on use) + + +.option server_service gsasl string &`smtp`& +This is the SASL service that the server claims to implement. +Some mechanisms will use this data. + + +.section "&(gsasl)& auth variables" "SECTgsaslauthvar" +.vindex "&$auth1$&, &$auth2$&, etc" +These may be set when evaluating specific options, as detailed above. +They will also be set when evaluating &%server_condition%&. + +Unless otherwise stated below, the &(gsasl)& integration will use the following +meanings for these variables: + +.ilist +.vindex "&$auth1$&" +&$auth1$&: the &'authentication id'& +.next +.vindex "&$auth2$&" +&$auth2$&: the &'authorization id'& +.next +.vindex "&$auth3$&" +&$auth3$&: the &'realm'& +.endlist + +On a per-mechanism basis: + +.ilist +.cindex "authentication" "EXTERNAL" +EXTERNAL: only &$auth1$& is set, to the possibly empty &'authorization id'&; +the &%server_condition%& option must be present. +.next +.cindex "authentication" "ANONYMOUS" +ANONYMOUS: only &$auth1$& is set, to the possibly empty &'anonymous token'&; +the &%server_condition%& option must be present. +.next +.cindex "authentication" "GSSAPI" +GSSAPI: &$auth1$& will be set to the &'GSSAPI Display Name'&; +&$auth2$& will be set to the &'authorization id'&, +the &%server_condition%& option must be present. +.endlist + +An &'anonymous token'& is something passed along as an unauthenticated +identifier; this is analogous to FTP anonymous authentication passing an +email address, or software-identifier@, as the "password". + + +An example showing the password having the realm specified in the callback +and demonstrating a Cyrus SASL to GSASL migration approach is: +.code +gsasl_cyrusless_crammd5: + driver = gsasl + public_name = CRAM-MD5 + server_realm = imap.example.org + server_password = ${lookup{$auth1:$auth3:userPassword}\ + dbmjz{/etc/sasldb2}{$value}fail} + server_set_id = ${quote:$auth1} + server_condition = yes +.endd + +.wen + +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.new +.chapter "The heimdal_gssapi authenticator" "CHAPheimdalgss" +.scindex IIDheimdalgssauth1 "&(heimdal_gssapi)& authenticator" +.scindex IIDheimdalgssauth2 "authenticators" "&(heimdal_gssapi)&" +.cindex "authentication" "GSSAPI" +.cindex "authentication" "Kerberos" +The &(heimdal_gssapi)& authenticator provides server integration for the +Heimdal GSSAPI/Kerberos library, permitting Exim to set a keytab pathname +reliably. + +.option server_hostname heimdal_gssapi string&!! "see below" +This option selects the hostname that is used, with &%server_service%&, +for constructing the GSS server name, as a &'GSS_C_NT_HOSTBASED_SERVICE'& +identifier. The default value is &`$primary_hostname`&. + +.option server_keytab heimdal_gssapi string&!! unset +If set, then Heimdal will not use the system default keytab (typically +&_/etc/krb5.keytab_&) but instead the pathname given in this option. +The value should be a pathname, with no &"file:"& prefix. + +.option server_service heimdal_gssapi string&!! "smtp" +This option specifies the service identifier used, in conjunction with +&%server_hostname%&, for building the identifer for finding credentials +from the keytab. + + +.section "&(heimdal_gssapi)& auth variables" "SECTheimdalgssauthvar" +Beware that these variables will typically include a realm, thus will appear +to be roughly like an email address already. The &'authzid'& in &$auth2$& is +not verified, so a malicious client can set it to anything. + +The &$auth1$& field should be safely trustable as a value from the Key +Distribution Center. Note that these are not quite email addresses. +Each identifier is for a role, and so the left-hand-side may include a +role suffix. For instance, &"joe/admin@EXAMPLE.ORG"&. + +.vindex "&$auth1$&, &$auth2$&, etc" +.ilist +.vindex "&$auth1$&" +&$auth1$&: the &'authentication id'&, set to the GSS Display Name. +.next +.vindex "&$auth2$&" +&$auth2$&: the &'authorization id'&, sent within SASL encapsulation after +authentication. If that was empty, this will also be set to the +GSS Display Name. +.endlist + +.wen + . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -24277,8 +24980,14 @@ DHE_DSS). The default list contains RSA, DHE_DSS, DHE_RSA. For &%gnutls_require_mac%&, the recognized names are SHA (synonym SHA1), and MD5. The default list contains SHA, MD5. -For &%gnutls_require_protocols%&, the recognized names are TLS1 and SSL3. -The default list contains TLS1, SSL3. +.new +For &%gnutls_require_protocols%&, the recognized names are TLS1.2, TLS1.1, +TLS1.0, (TLS1) and SSL3. +The default list contains TLS1.2, TLS1.1, TLS1.0, SSL3. +TLS1 is an alias for TLS1.0, for backwards compatibility. +For sufficiently old versions of the GnuTLS library, TLS1.2 or TLS1.1 might +not be supported and will not be recognised by Exim. +.wen In a server, the order of items in these lists is unimportant. The server advertises the availability of all the relevant cipher suites. However, in a @@ -24493,13 +25202,11 @@ list of permitted cipher suites. If either of these checks fails, delivery to the current host is abandoned, and the &(smtp)& transport tries to deliver to alternative hosts, if any. -.new &*Note*&: These options must be set in the &(smtp)& transport for Exim to use TLS when it is operating as a client. Exim does not assume that a server certificate (set by the global options of the same name) should also be used when operating as a client. -.wen .vindex "&$host$&" .vindex "&$host_address$&" @@ -24804,6 +25511,17 @@ and try again later, but that is their problem, though it does waste some of your resources. +.section "The SMTP DKIM ACL" "SECTDKIMACL" +The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support +enabled (which is the default). + +The ACL test specified by &%acl_smtp_dkim%& happens after a message has been +received, and is executed for each DKIM signature found in a message. If not +otherwise specified, the default action is to accept. + +For details on the operation of DKIM, see chapter &<>&. + + .section "The SMTP MIME ACL" "SECID194" The &%acl_smtp_mime%& option is available only when Exim is compiled with the content-scanning extension. For details, see chapter &<>&. @@ -24835,7 +25553,6 @@ client are given temporary error responses until QUIT is received or the connection is closed. In these special cases, the QUIT ACL does not run. -.new .section "The not-QUIT ACL" "SECTNOTQUITACL" .vindex &$acl_smtp_notquit$& The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when @@ -24843,7 +25560,6 @@ an SMTP session ends without sending QUIT. However, when Exim itself is is bad trouble, such as being unable to write to its log files, this ACL is not run, because it might try to do things (such as write to log files) that make the situation even worse. -.wen Like the QUIT ACL, this ACL is provided to make it possible to do customized logging or to gather statistics, and its outcome is ignored. The &%delay%& @@ -25702,6 +26418,25 @@ warn control = caseful_local_part Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. + +.vitem &*control&~=&~debug/*&<&'options'&> +.cindex "&ACL;" "enabling debug logging" +.cindex "debugging" "enabling from an ACL" +This control turns on debug logging, almost as though Exim had been invoked +with &`-d`&, with the output going to a new logfile, by default called +&'debuglog'&. The filename can be adjusted with the &'tag'& option, which +may access any variables already defined. The logging may be adjusted with +the &'opts'& option, which takes the same values as the &`-d`& command-line +option. Some examples (which depend on variables that don't exist in all +contexts): +.code + control = debug + control = debug/tag=.$sender_host_address + control = debug/opts=+expand+acl + control = debug/tag=.$message_exim_id/opts=+expand +.endd + + .vitem &*control&~=&~enforce_sync*& &&& &*control&~=&~no_enforce_sync*& .cindex "SMTP" "synchronization checking" @@ -25837,7 +26572,7 @@ This control is permitted only for the MAIL, RCPT, and start of data ACLs (the latter is the one defined by &%acl_smtp_predata%&). Setting it tells Exim that the current message is a submission from a local MUA. In this case, Exim operates in &"submission mode"&, and applies certain fixups to the message if -necessary. For example, it add a &'Date:'& header line if one is not present. +necessary. For example, it adds a &'Date:'& header line if one is not present. This control is not permitted in the &%acl_smtp_data%& ACL, because that is too late (the message has already been created). @@ -25850,7 +26585,7 @@ that may be received in the same SMTP connection. .vitem &*control&~=&~suppress_local_fixups*& .cindex "submission fixups, suppressing" This control applies to locally submitted (non TCP/IP) messages, and is the -complement of &`control`& &`=`& &`submission`&. It disables the fixups that are +complement of &`control = submission`&. It disables the fixups that are normally applied to locally-submitted messages. Specifically: .ilist @@ -25879,12 +26614,12 @@ All four possibilities for message fixups can be specified: .ilist Locally submitted, fixups applied: the default. .next -Locally submitted, no fixups applied: use &`control`& &`=`& -&`suppress_local_fixups`&. +Locally submitted, no fixups applied: use +&`control = suppress_local_fixups`&. .next Remotely submitted, no fixups applied: the default. .next -Remotely submitted, fixups applied: use &`control`& &`=`& &`submission`&. +Remotely submitted, fixups applied: use &`control = submission`&. .endlist @@ -26906,69 +27641,118 @@ rate at which a recipient receives messages, you can use the key &`$local_part@$domain`& with the &%per_rcpt%& option (see below) in a RCPT ACL. -Internally, Exim 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. +Each &%ratelimit%& condition can have up to four options. A &%per_*%& option +specifies what Exim measures the rate of, for example messages or recipients +or bytes. You can adjust the measurement using the &%unique=%& and/or +&%count=%& options. You can also control when Exim updates the recorded rate +using a &%strict%&, &%leaky%&, or &%readonly%& option. The options are +separated by a slash, like the other parameters. They may appear in any order. + +Internally, Exim appends the smoothing constant &'p'& onto the lookup key with +any options that alter the meaning of the stored data. The limit &'m'& is not +stored, so you can alter the configured maximum rate and Exim will still +remember clients' past behaviour. If you change the &%per_*%& mode or add or +remove the &%unique=%& option, the lookup key changes so Exim will forget past +behaviour. The lookup key is not affected by changes to the update mode and +the &%count=%& option. -Each &%ratelimit%& condition can have up to three options. One option -specifies what Exim measures the rate of, and the second specifies how Exim -handles excessively fast clients. The third option can be &`noupdate`&, to -disable updating of the ratelimiting database (see section &<>&). -The options are separated by a slash, like the other parameters. They may -appear in any order. .section "Ratelimit options for what is being measured" "ratoptmea" -The &%per_conn%& option limits the client's connection rate. +.cindex "rate limiting" "per_* options" +The &%per_conn%& option limits the client's connection rate. It is not +normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or +&%acl_not_smtp_start%& ACLs. The &%per_mail%& option limits the client's rate of sending messages. This is -the default if none of the &%per_*%& options is specified. - -The &%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 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 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. +the default if none of the &%per_*%& options is specified. It can be used in +&%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&, +&%acl_smtp_data%&, or &%acl_not_smtp%&. + +The &%per_byte%& option limits the sender's email bandwidth. It can be used in +the same ACLs as the &%per_mail%& option, though it is best to use this option +in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is +used in an earlier ACL, Exim relies on the SIZE parameter given by the client +in its MAIL command, which may be inaccurate or completely missing. You can +follow the limit &'m'& in the configuration with K, M, or G to specify limits +in kilobytes, megabytes, or gigabytes, respectively. + +The &%per_rcpt%& option causes Exim to limit the rate at which recipients are +accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, +&%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In +&%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other +ACLs the rate is updated with the total recipient count in one go. Note that +in either case the rate limiting engine will see a message with many +recipients as a large high-speed burst. + +The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the +number of different recipients that the client has sent messages to in the +last time period. That is, if the client repeatedly sends messages to the same +recipient, its measured rate is not increased. This option can only be used in +&%acl_smtp_rcpt%&. The &%per_cmd%& option causes Exim to recompute the rate every time the -condition is processed. This can be used to limit the SMTP command rate. -This command is essentially an alias of &%per_rcpt%& to make it clear -that the effect is to limit the rate at which individual commands, -rather than recipients, are accepted. +condition is processed. This can be used to limit the rate of any SMTP +command. If it is used in multiple ACLs it can limit the aggregate rate of +multiple different commands. + +The &%count=%& option can be used to alter how much Exim adds to the client's +measured rate. For example, the &%per_byte%& option is equivalent to +&`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim +increases the measured rate by one (except for the &%per_rcpt%& option in ACLs +other than &%acl_smtp_rcpt%&). The count does not have to be an integer. + +The &%unique=%& option is described in section &<>& below. + -.section "Ratelimit options for handling fast clients" "ratophanfas" +.section "Ratelimit update modes" "ratoptupd" +.cindex "rate limiting" "reading data without updating" +You can specify one of three options with the &%ratelimit%& condition to +control when its database is updated. This section describes the &%readonly%& +mode, and the next section describes the &%strict%& and &%leaky%& modes. + +If the &%ratelimit%& condition is used in &%readonly%& mode, Exim looks up a +previously-computed rate to check against the limit. + +For example, you can test the client's sending rate and deny it access (when +it is too fast) in the connect ACL. If the client passes this check then it +can go on to send a message, in which case its recorded rate will be updated +in the MAIL ACL. Subsequent connections from the same client will check this +new rate. +.code +acl_check_connect: + deny ratelimit = 100 / 5m / readonly + log_message = RATE CHECK: $sender_rate/$sender_rate_period \ + (max $sender_rate_limit) +# ... +acl_check_mail: + warn ratelimit = 100 / 5m / strict + log_message = RATE UPDATE: $sender_rate/$sender_rate_period \ + (max $sender_rate_limit) +.endd + +If Exim encounters multiple &%ratelimit%& conditions with the same key when +processing a message then it may increase the client's measured rate more than +it should. For example, this will happen if you check the &%per_rcpt%& option +in both &%acl_smtp_rcpt%& and &%acl_smtp_data%&. However it's OK to check the +same &%ratelimit%& condition multiple times in the same ACL. You can avoid any +multiple update problems by using the &%readonly%& option on later ratelimit +checks. + +The &%per_*%& options described above do not make sense in some ACLs. If you +use a &%per_*%& option in an ACL where it is not normally permitted then the +update mode defaults to &%readonly%& and you cannot specify the &%strict%& or +&%leaky%& modes. In other ACLs the default update mode is &%leaky%& (see the +next section) so you must specify the &%readonly%& option explicitly. + + +.section "Ratelimit options for handling fast clients" "ratoptfast" +.cindex "rate limiting" "strict and leaky modes" If a client's average rate is greater than the maximum, the rate limiting engine can react in two possible ways, depending on the presence of the -&%strict%& or &%leaky%& options. This is independent of the other +&%strict%& or &%leaky%& update modes. This is independent of the other counter-measures (such as rejecting the message) that may be specified by the -rest of the ACL. The default mode is leaky, which avoids a sender's -over-aggressive retry rate preventing it from getting any email through. +rest of the ACL. -The &%strict%& option means that the client's recorded rate is always -updated. The effect of this is that Exim measures the client's average rate -of attempts to send email, which can be much higher than the maximum 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) -.endd The &%leaky%& (default) option means that the client's recorded rate is not updated if it is above the limit. The effect of this is that Exim measures the client's average rate of successfully sent email, which cannot be greater than @@ -26976,6 +27760,59 @@ the maximum allowed. If the client is over the limit it may suffer some counter-measures (as specified in the ACL), but it will still be able to send email at the configured maximum rate, whatever the rate of its attempts. This is generally the better choice if you have clients that retry automatically. +For example, it does not prevent a sender with an over-aggressive retry rate +from getting any email through. + +The &%strict%& option means that the client's recorded rate is always +updated. The effect of this is that Exim measures the client's average rate +of attempts to send email, which can be much higher than the maximum it is +actually allowed. If the client is over the limit it may be subjected to +counter-measures by the ACL. It must slow down and allow sufficient time to +pass that its computed rate falls below the maximum before it can send email +again. The time (the number of smoothing periods) it must wait and not +attempt to send mail can be calculated with this formula: +.code + ln(peakrate/maxrate) +.endd + + +.section "Limiting the rate of different events" "ratoptuniq" +.cindex "rate limiting" "counting unique events" +The &%ratelimit%& &%unique=%& option controls a mechanism for counting the +rate of different events. For example, the &%per_addr%& option uses this +mechanism to count the number of different recipients that the client has +sent messages to in the last time period; it is equivalent to +&`per_rcpt/unique=$local_part@$domain`&. You could use this feature to +measure the rate that a client uses different sender addresses with the +options &`per_mail/unique=$sender_address`&. + +For each &%ratelimit%& key Exim stores the set of &%unique=%& values that it +has seen for that key. The whole set is thrown away when it is older than the +rate smoothing period &'p'&, so each different event is counted at most once +per period. In the &%leaky%& update mode, an event that causes the client to +go over the limit is not added to the set, in the same way that the client's +recorded rate is not updated in the same situation. + +When you combine the &%unique=%& and &%readonly%& options, the specific +&%unique=%& value is ignored, and Exim just retrieves the client's stored +rate. + +The &%unique=%& mechanism needs more space in the ratelimit database than the +other &%ratelimit%& options in order to store the event set. The number of +unique values is potentially as large as the rate limit, so the extra space +required increases with larger limits. + +The uniqueification is not perfect: there is a small probability that Exim +will think a new event has happened before. If the sender's rate is less than +the limit, Exim should be more than 99.9% correct. However in &%strict%& mode +the measured rate can go above the limit, in which case Exim may under-count +events by a significant margin. Fortunately, if the rate is high enough (2.7 +times the limit) that the false positive rate goes above 9%, then Exim will +throw away the over-full event set before the measured rate falls below the +limit. Therefore the only harm should be that exceptionally high sending rates +are logged incorrectly; any countermeasures you configure will be as effective +as intended. + .section "Using rate limiting" "useratlim" Exim's other ACL facilities are used to define what counter-measures are taken @@ -27019,36 +27856,6 @@ this means that Exim will lose its hints data after a reboot (including retry hints, the callout cache, and ratelimit data). -.section "Reading ratelimit data without updating" "rearatdat" -.cindex "rate limitint" "reading data without updating" -If the &%noupdate%& option is present on a &%ratelimit%& ACL condition, Exim -computes the rate and checks the limit as normal, but it does not update the -saved data. This means that, in relevant ACLs, it is possible to lookup the -existence of a specified (or auto-generated) ratelimit key without incrementing -the ratelimit counter for that key. In order for this to be useful, another ACL -entry must set the rate for the same key (otherwise it will always be zero). -For example: -.code -acl_check_connect: - deny ratelimit = 100 / 5m / strict / per_cmd / noupdate - log_message = RATE: $sender_rate/$sender_rate_period \ - (max $sender_rate_limit) -.endd -.display -&'... some other logic and tests...'& -.endd -.code -acl_check_mail: - warn ratelimit = 100 / 5m / strict / per_cmd - condition = ${if le{$sender_rate}{$sender_rate_limit}} - logwrite = RATE UPDATE: $sender_rate/$sender_rate_period \ - (max $sender_rate_limit) -.endd -In this example, the rate is tested and used to deny access (when it is too -high) in the connect ACL, but the actual computation of the remembered rate -happens later, on a per-command basis, in another ACL. - - .section "Address verification" "SECTaddressverification" .cindex "verifying address" "options for" @@ -27323,7 +28130,7 @@ check for a &"random"& local part at the same domain. The local part is not really random &-- it is defined by the expansion of the option &%callout_random_local_part%&, which defaults to .code -$primary_host_name-$tod_epoch-testing +$primary_hostname-$tod_epoch-testing .endd The idea here is to try to determine whether the remote host accepts all local parts without checking. If it does, there is no point in doing callouts for @@ -27625,12 +28432,10 @@ the third string (in this case &"1"&), whether or not the cryptographic and timeout checks succeed. The &$prvscheck_result$& variable contains the result of the checks (empty for failure, &"1"& for success). -.new 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: -.wen .code batv_redirect: driver = redirect @@ -27815,6 +28620,7 @@ It supports a &"generic"& interface to scanners called via the shell, and specialized interfaces for &"daemon"& type virus scanners, which are resident in memory and thus are much faster. + .oindex "&%av_scanner%&" You can set the &%av_scanner%& option in first part of the Exim configuration file to specify which scanner to use, together with any additional options that @@ -27826,7 +28632,7 @@ 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 @@ -27840,6 +28646,7 @@ example: av_scanner = aveserver:/var/run/aveserver .endd + .vitem &%clamd%& .cindex "virus scanners" "clamd" This daemon-type scanner is GPL and free. You can get it at @@ -27850,8 +28657,16 @@ 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. @@ -27991,6 +28806,9 @@ If your virus scanner cannot unpack MIME and TNEF containers itself, you should use the &%demime%& condition (see section &<>&) before the &%malware%& condition. +Beware the interaction of Exim's &%message_size_limit%& with any size limits +imposed by your anti-virus scanner. + Here is a very simple scanning example: .code deny message = This message contains malware ($malware_name) @@ -28113,9 +28931,8 @@ it always return &"true"& by appending &`:true`& to the username. .cindex "spam scanning" "returned variables" When the &%spam%& condition is run, it sets up a number of expansion -variables. With the exception of &$spam_score_int$&, these are usable only -within ACLs; their values are not retained with the message and so cannot be -used at delivery time. +variables. These variables are saved with the received message, thus they are +available for use at delivery time. .vlist .vitem &$spam_score$& @@ -28126,11 +28943,7 @@ for inclusion in log or reject messages. The spam score of the message, multiplied by ten, as an integer value. For 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. 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. +The integer value is useful for numeric comparisons in conditions. .vitem &$spam_bar$& A string consisting of a number of &"+"& or &"-"& characters, representing the @@ -30330,8 +31143,8 @@ 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. @@ -30817,8 +31630,8 @@ 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 @@ -31755,8 +32568,8 @@ log_file_path = $spool_directory/log/%slog If you do not specify anything at build time or run time, that is where the logs are written. -A log file path may also contain &`%D`& if datestamped log file names are in -use &-- see section &<>& below. +A log file path may also contain &`%D`& or &`%M`& if datestamped log file names +are in use &-- see section &<>& below. Here are some examples of possible settings: .display @@ -31800,14 +32613,15 @@ renamed. .cindex "log" "datestamped files" Instead of cycling the main and reject log files by renaming them periodically, some sites like to use files whose names contain a datestamp, -for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_&. -Exim has support for this way of working. It is enabled by setting the -&%log_file_path%& option to a path that includes &`%D`& at the point where the -datestamp is required. For example: +for example, &_mainlog-20031225_&. The datestamp is in the form &_yyyymmdd_& or +&_yyyymm_&. Exim has support for this way of working. It is enabled by setting +the &%log_file_path%& option to a path that includes &`%D`& or &`%M`& at the +point where the datestamp is required. For example: .code log_file_path = /var/spool/exim/log/%slog-%D log_file_path = /var/log/exim-%s-%D.log log_file_path = /var/spool/exim/log/%D-%slog +log_file_path = /var/log/exim/%s.%M .endd As before, &`%s`& is replaced by &"main"& or &"reject"&; the following are examples of names generated by the above examples: @@ -31815,6 +32629,7 @@ examples of names generated by the above examples: /var/spool/exim/log/mainlog-20021225 /var/log/exim-reject-20021225.log /var/spool/exim/log/20021225-mainlog +/var/log/exim/main.200212 .endd When this form of log file is specified, Exim automatically switches to new files at midnight. It does not make any attempt to compress old logs; you @@ -31823,14 +32638,16 @@ run &'exicyclog'& with this form of logging. The location of the panic log is also determined by &%log_file_path%&, but it is not datestamped, because rotation of the panic log does not make sense. -When generating the name of the panic log, &`%D`& is removed from the string. -In addition, if it immediately follows a slash, a following non-alphanumeric -character is removed; otherwise a preceding non-alphanumeric character is -removed. Thus, the three examples above would give these panic log names: +When generating the name of the panic log, &`%D`& or &`%M`& are removed from +the string. In addition, if it immediately follows a slash, a following +non-alphanumeric character is removed; otherwise a preceding non-alphanumeric +character is removed. Thus, the four examples above would give these panic +log names: .code /var/spool/exim/log/paniclog /var/log/exim-panic.log /var/spool/exim/log/paniclog +/var/log/exim/panic .endd @@ -33669,15 +34486,26 @@ which only root has access, this guards against someone who has broken into the Exim account from running a privileged Exim with an arbitrary configuration file, and using it to break into other accounts. .next -If ALT_CONFIG_ROOT_ONLY is defined, root privilege is retained for &%-C%& -and &%-D%& only if the caller of Exim is root. Without it, the Exim user may -also use &%-C%& and &%-D%& and retain privilege. Setting this option locks out -the possibility of testing a configuration using &%-C%& right through message -reception and delivery, even if the caller is root. The reception works, but by -that time, Exim is running as the Exim user, so when it re-execs to regain -privilege for the delivery, the use of &%-C%& causes privilege to be lost. -However, root can test reception and delivery using two separate commands. -ALT_CONFIG_ROOT_ONLY is not set by default. + +If a non-trusted configuration file (i.e. not the default configuration file +or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST +file) is specified with &%-C%&, or if macros are given with &%-D%& (but see +the next item), then root privilege is retained only if the caller of Exim is +root. This locks out the possibility of testing a configuration using &%-C%& +right through message reception and delivery, even if the caller is root. The +reception works, but by that time, Exim is running as the Exim user, so when +it re-execs to regain privilege for the delivery, the use of &%-C%& causes +privilege to be lost. However, root can test reception and delivery using two +separate commands. + +.next +The WHITELIST_D_MACROS build option declares some macros to be safe to override +with &%-D%& if the real uid is one of root, the Exim run-time user or the +CONFIGURE_OWNER, if defined. The potential impact of this option is limited by +requiring the run-time value supplied to &%-D%& to match a regex that errs on +the restrictive side. Requiring build-time selection of safe macros is onerous +but this option is intended solely as a transition mechanism to permit +previously-working configurations to continue to work after release 4.73. .next If DISABLE_D_OPTION is defined, the use of the &%-D%& command line option is disabled. @@ -33691,7 +34519,6 @@ is permitted to modify the runtime file from using Exim as a way to get root. - .section "Root privilege" "SECID270" .cindex "setuid" .cindex "root privilege" @@ -33733,11 +34560,13 @@ 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%&" @@ -33994,6 +34823,12 @@ arbitrary program's being run as exim, not as root. +.section "Dynamic module directory" "SECTdynmoddir" +Any dynamically loadable modules must be installed into the directory +defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit +loading it. + + .section "Use of sprintf()" "SECID279" .cindex "&[sprintf()]&" A large number of occurrences of &"sprintf"& in the code are actually calls to @@ -34343,7 +35178,6 @@ unqualified domain &'foundation'&. . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// -.new .chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&& "DKIM Support" .cindex "DKIM" @@ -34358,7 +35192,7 @@ 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 context. +different signature contexts. .endlist In typical Exim style, the verification implementation does not include any @@ -34386,19 +35220,19 @@ 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 +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 +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 &%$dkim_domain%&. .option dkim_private_key smtp string&!! unset -MANDATORY +MANDATORY: This sets the private key to use. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion variables to determine the private key to use. The result can either @@ -34414,14 +35248,14 @@ is set. .endlist .option dkim_canon smtp string&!! unset -OPTIONAL +OPTIONAL: This option sets the canonicalization method used when signing a message. The DKIM RFC currently supports two methods: "simple" and "relaxed". The option defaults to "relaxed" when unset. Note: the current implementation only supports using the same canonicalization method for both headers and body. .option dkim_strict smtp string&!! unset -OPTIONAL +OPTIONAL: This option defines how Exim behaves when signing a message that should be signed fails for some reason. When the expansion evaluates to either "1" or "true", Exim will defer. Otherwise Exim will send the message @@ -34429,7 +35263,7 @@ unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion variables here. .option dkim_sign_headers smtp string&!! unset -OPTIONAL +OPTIONAL: When set, this option must expand to (or be specified as) a colon-separated list of header names. Headers with these names will be included in the message signature. When unspecified, the header names recommended in RFC4871 will be @@ -34455,8 +35289,8 @@ more advanced policies. For that reason, the global option The global option &%dkim_verify_signers%& can be set to a colon-separated list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is called. It is expanded when the message has been received. At this point, -the expansion variable &%$dkim_signers%& already contains a colon- -separated list of signer domains and identities for the message. When +the expansion variable &%$dkim_signers%& already contains a colon-separated +list of signer domains and identities for the message. When &%dkim_verify_signers%& is not specified in the main configuration, it defaults as: .code @@ -34470,7 +35304,7 @@ dkim_verify_signers = paypal.com:ebay.com:$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. Example: +You can also be more creative in constructing your policy. For example: .code dkim_verify_signers = $sender_address_domain:$dkim_signers .endd @@ -34482,9 +35316,10 @@ If a domain or identity is listed several times in the (expanded) value of Inside the &%acl_smtp_dkim%&, the following expansion variables are available (from most to least important): + .vlist .vitem &%$dkim_cur_signer%& -The signer that is being evaluated in this ACL run. This can be domain or +The signer that is being evaluated in this ACL run. This can be a domain or an identity. This is one of the list items from the expanded main option &%dkim_verify_signers%& (see above). .vitem &%$dkim_verify_status%& @@ -34529,7 +35364,7 @@ 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 +The key record selector string. .vitem &%$dkim_algo%& The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'. .vitem &%$dkim_canon_body%& @@ -34555,7 +35390,7 @@ integer size comparisons against this value. 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%& +.vitem &%$nosubdomains%& "1" if the key record forbids subdomaining, "0" otherwise. .vitem &%$dkim_key_srvtype%& Service type (tag s=) from the key record. Defaults to "*" if not specified @@ -34564,7 +35399,7 @@ in the key record. Key granularity (tag g=) from the key record. Defaults to "*" if not specified in the key record. .vitem &%$dkim_key_notes%& -Notes from the key record (tag n=) +Notes from the key record (tag n=). .endlist In addition, two ACL conditions are provided: @@ -34574,7 +35409,7 @@ In addition, two ACL conditions are provided: ACL condition that checks a colon-separated list of domains or identities for a match against the domain or identity that the ACL is currently verifying (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL -verb to a group of domains or identities, like: +verb to a group of domains or identities. For example: .code # Warn when message apparently from GMail has no signature at all @@ -34600,7 +35435,6 @@ 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 -.wen . //////////////////////////////////////////////////////////////////////////// . ////////////////////////////////////////////////////////////////////////////