X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/66581d1e830f4e68f2b074b8d79a80645c6a72ea..0a34949459c8ec5f79599a458704b7b11cdbb248:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index b2c40e48a..15b3a2b89 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -47,8 +47,8 @@ . the element must also be updated for each new edition. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.71" -.set version "4.72" +.set previousversion "4.72" +.set version "4.73" .set ACL "access control lists (ACLs)" .set I "    " @@ -176,8 +176,8 @@ EximMaintainers EM - 4.72 - 29 May 2010 + 4.73 + 19 Nov 2010 EM 2009University of Cambridge @@ -1544,7 +1544,6 @@ If a host is unreachable for a period of time, a number of messages may be waiting for it by the time it recovers, and sending them in a single SMTP connection is clearly beneficial. Whenever a delivery to a remote host is deferred, - .cindex "hints database" Exim makes a note in its hints database, and whenever a successful SMTP delivery has happened, it looks to see if any other messages are waiting @@ -1894,6 +1893,7 @@ given in chapter &<>&. .section "Use of tcpwrappers" "SECID27" +.new .cindex "tcpwrappers, building Exim to support" .cindex "USE_TCP_WRAPPERS" .cindex "TCP_WRAPPERS_DAEMON_NAME" @@ -1924,7 +1924,7 @@ can be changed at build time by setting TCP_WRAPPERS_DAEMON_NAME in in &_Local/Makefile_&, or by setting tcp_wrappers_daemon_name in the configure file. Consult the &'tcpwrappers'& documentation for further details. - +.wen .section "Including support for IPv6" "SECID28" @@ -1946,6 +1946,36 @@ support has not been tested for some time. +.section "Dynamically loaded lookup module support" "SECTdynamicmodules" +.cindex "lookup modules" +.cindex "dynamic modules" +.cindex ".so building" +On some platforms, Exim supports not compiling all lookup types directly into +the main binary, instead putting some into external modules which can be loaded +on demand. +This permits packagers to build Exim with support for lookups with extensive +library dependencies without requiring all users to install all of those +dependencies. +Most, but not all, lookup types can be built this way. + +Set &`LOOKUP_MODULE_DIR`& to the directory into which the modules will be +installed; Exim will only load modules from that directory, as a security +measure. You will need to set &`CFLAGS_DYNAMIC`& if not already defined +for your OS; see &_OS/Makefile-Linux_& for an example. +Some other requirements for adjusting &`EXTRALIBS`& may also be necessary, +see &_src/EDITME_& for details. + +Then, for each module to be loaded dynamically, define the relevant +&`LOOKUP_`&<&'lookup_type'&> flags to have the value "2" instead of "yes". +For example, this will build in lsearch but load sqlite and mysql support +on demand: +.code +LOOKUP_LSEARCH=yes +LOOKUP_SQLITE=2 +LOOKUP_MYSQL=2 +.endd + + .section "The building process" "SECID29" .cindex "build directory" Once &_Local/Makefile_& (and &_Local/eximon.conf_&, if required) have been @@ -2609,10 +2639,12 @@ This option causes Exim to output a few sentences stating what it is. The same output is generated if the Exim binary is called with no options and no arguments. +.new .vitem &%--version%& .oindex "&%--version%&" This option is an alias for &%-bV%& and causes version information to be displayed. +.wen .vitem &%-B%&<&'type'&> .oindex "&%-B%&" @@ -3179,6 +3211,7 @@ above concerning senders and qualification do not apply. In this situation, Exim behaves in exactly the same way as it does when receiving a message via the listening daemon. +.new .vitem &%-bmalware%&&~<&'filename'&> .oindex "&%-bmalware%&" .cindex "testing", "malware" @@ -3198,6 +3231,7 @@ This option requires admin privileges. The &%-bmalware%& option will not be extended to be more generally useful, there are better tools for file-scanning. This option exists to help administrators verify their Exim and AV scanner configuration. +.wen .vitem &%-bt%& .oindex "&%-bt%&" @@ -3250,7 +3284,7 @@ doing such tests. .cindex "version number of Exim" This option causes Exim to write the current version number, compilation number, and compilation date of the &'exim'& binary to the standard output. -It also lists the DBM library this is being used, the optional modules (such as +It also lists the DBM library that is being used, the optional modules (such as specific lookup types), the drivers that are included in the binary, and the name of the run time configuration file that is in use. @@ -3319,6 +3353,7 @@ This option acts like &%-bv%&, but verifies the address as a sender rather than a recipient address. This affects any rewriting and qualification that might happen. +.new .vitem &%-C%&&~<&'filelist'&> .oindex "&%-C%&" .cindex "configuration file" "alternate" @@ -3334,12 +3369,15 @@ proceeding any further along the list, and an error is generated. 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_PREFIX_LIST file is defined in &_Local/Makefile_&, -root privilege is retained for any configuration file which matches a prefix -listed in that file. - -Leaving TRUSTED_CONFIG_PREFIX_LIST unset precludes the possibility of testing -a configuration using &%-C%& right through message reception and delivery, +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 @@ -3364,7 +3402,9 @@ syntactically correct, but cannot be used for test deliveries, unless the caller is privileged, or unless it is an exotic configuration that does not require privilege. No check is made on the owner or group of the files specified by this option. +.wen +.new .vitem &%-D%&<&'macro'&>=<&'value'&> .oindex "&%-D%&" .cindex "macro" "setting on command line" @@ -3397,6 +3437,7 @@ example: exim '-D ABC = something' ... .endd &%-D%& may be repeated up to 10 times on a command line. +.wen .vitem &%-d%&<&'debug&~options'&> .oindex "&%-d%&" @@ -4497,6 +4538,7 @@ most configurations, this specifies a single file. However, it is permitted to give a colon-separated list of file names, in which case Exim uses the first existing file in the list. +.new .cindex "EXIM_USER" .cindex "EXIM_GROUP" .cindex "CONFIGURE_OWNER" @@ -4527,7 +4569,7 @@ configuration to a new file of that name if it did not previously exist. If CONFIGURE_FILE is a list, no default is automatically installed. Chapter &<>& is a &"walk-through"& discussion of the default configuration. - +.wen .section "Using a different configuration file" "SECID40" @@ -4536,15 +4578,16 @@ 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 unless the argument for &%-C%& is identical to the built-in value from -CONFIGURE_FILE) or matches a prefix listed in the TRUSTED_CONFIG_PREFIX_LIST -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%&, if root privilege has been dropped. +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_PREFIX_LIST file. This locks out the possibility -of testing a configuration using &%-C%& right through message reception and +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 @@ -4565,6 +4608,7 @@ non-privileged user causes Exim to discard its root privilege. If DISABLE_D_OPTION is defined in &_Local/Makefile_&, the use of &%-D%& is completely disabled, and its use causes an immediate error exit. +.new The WHITELIST_D_MACROS option in &_Local/Makefile_& permits the binary builder to declare certain macro names trusted, such that root privilege will not necessarily be discarded. @@ -4574,6 +4618,7 @@ values are acceptable, then Exim will not give up root privilege if the caller is root, the Exim run-time user, or the CONFIGURE_OWNER, if set. This is a transition mechanism and is expected to be removed in the future. Acceptable values for the macros satisfy the regexp: &`^[A-Za-z0-9_/.-]*$`& +.wen Some sites may wish to use the same Exim binary on different machines that share a file system, but to use different configuration files on each machine. @@ -6677,7 +6722,6 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. -.new .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 @@ -6689,7 +6733,6 @@ ${lookup dnsdb{>\n; txt=a.b.example}} .endd It is permitted to specify a space as the separator character. Further white space is ignored. -.wen .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" @@ -9653,6 +9696,7 @@ srandomdev() or srandom(), or a custom implementation even weaker than random(). +.new .vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*& .cindex "expansion" "IP address" This operator reverses an IP address; for IPv4 addresses, the result is in @@ -9666,6 +9710,7 @@ returns .code 4.2.0.192 and 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 .endd +.wen .vitem &*${rfc2047:*&<&'string'&>&*}*& @@ -9829,6 +9874,8 @@ lower case), signifying multiplication by 1024 or 1024*1024, respectively. As a special case, the numerical value of an empty string is taken as zero. + +.new .vitem &*bool&~{*&<&'string'&>&*}*& .cindex "expansion" "boolean parsing" .cindex "&%bool%& expansion condition" @@ -9844,6 +9891,8 @@ For example: .code ${if bool{$acl_m_privileged_sender} ... .endd +.wen + .vitem &*bool_lax&~{*&<&'string'&>&*}*& .cindex "expansion" "boolean parsing" @@ -14028,6 +14077,7 @@ an oversized message is logged in both the main and the reject logs. See also the generic transport option &%message_size_limit%&, which limits the size of message that an individual transport can process. +.new If you use a virus-scanner and set this option to to a value larger than the maximum size that your virus-scanner is configured to support, you may get failures triggered by large mails. The right size to configure for the @@ -14035,6 +14085,7 @@ virus-scanner depends upon what data is passed and the options in use but it's probably safest to just set it to a little larger than this value. Eg, with a default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M, some problems may result. +.wen .option move_frozen_messages main boolean false @@ -14088,6 +14139,7 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. +.new .option openssl_options main "string list" +dont_insert_empty_fragments .cindex "OpenSSL "compatibility options" This option allows an administrator to adjust the SSL options applied @@ -14116,6 +14168,7 @@ An example: .code openssl_options = -all +microsoft_big_sslv3_buffer .endd +.wen .option oracle_servers main "string list" unset @@ -15218,6 +15271,7 @@ contains the pipe command. This specifies the transport driver that is to be used when a &%mail%& command is used in a system filter. +.new .option system_filter_user main string unset .cindex "uid (user id)" "system filter" If this option is set to root, the system filter is run in the main Exim @@ -15232,6 +15286,7 @@ 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. +.wen .option tcp_nodelay main boolean true @@ -15713,8 +15768,10 @@ router is skipped, and the address is offered to the next one. If the result is any other value, the router is run (as this is the last precondition to be evaluated, all the other preconditions must be true). +.new This option is unique in that multiple &%condition%& options may be present. All &%condition%& options must succeed. +.wen The &%condition%& option provides a means of applying custom conditions to the running of routers. Note that in the case of a simple conditional expansion, @@ -15726,12 +15783,14 @@ Because of the default behaviour of the string expansion, this is equivalent to .code condition = ${if >{$message_age}{600}{true}{}} .endd +.new A multiple condition example, which succeeds: .code condition = ${if >{$message_age}{600}} condition = ${if !eq{${lc:$local_part}}{postmaster}} condition = foobar .endd +.wen If the expansion fails (other than forced failure) delivery is deferred. Some of the other precondition options are common special cases that could in fact be specified using &%condition%&. @@ -21168,6 +21227,7 @@ sought in the PATH directories, in the usual way. &*Warning*&: This does not apply to a command specified as a transport filter. +.new .option permit_coredump pipe boolean false Normally Exim inhibits core-dumps during delivery. If you have a need to get a core-dump of a pipe command, enable this command. This enables core-dumps @@ -21177,6 +21237,7 @@ for it and that this only be enabled when needed, as the risk of excessive resource consumption can be quite high. Note also that Exim is typically installed as a setuid binary and most operating systems will inhibit coredumps of these by default, so further OS-specific action may be required. +.wen .option pipe_as_creator pipe boolean false @@ -23721,7 +23782,7 @@ 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} \ @@ -24935,6 +24996,19 @@ and try again later, but that is their problem, though it does waste some of your resources. +.new +.section "The SMTP DKIM ACL" "SECTDKIMACL" +The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support +enabled (which is the default). + +The ACL test specified by &%acl_smtp_dkim%& happens after a message has been +received, and is executed for each DKIM signature found in a message. If not +otherwise specified, the default action is to accept. + +For details on the operation of DKIM, see chapter &<>&. +.wen + + .section "The SMTP MIME ACL" "SECID194" The &%acl_smtp_mime%& option is available only when Exim is compiled with the content-scanning extension. For details, see chapter &<>&. @@ -25831,6 +25905,7 @@ warn control = caseful_local_part Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. +.new .vitem &*control&~=&~debug/*&<&'options'&> .cindex "&ACL;" "enabling debug logging" .cindex "debugging" "enabling from an ACL" @@ -25847,6 +25922,7 @@ contexts): control = debug/opts=+expand+acl control = debug/tag=.$message_exim_id/opts=+expand .endd +.wen .vitem &*control&~=&~enforce_sync*& &&& &*control&~=&~no_enforce_sync*& @@ -28143,8 +28219,10 @@ If your virus scanner cannot unpack MIME and TNEF containers itself, you should use the &%demime%& condition (see section &<>&) before the &%malware%& condition. +.new Beware the interaction of Exim's &%message_size_limit%& with any size limits imposed by your anti-virus scanner. +.wen Here is a very simple scanning example: .code @@ -28266,10 +28344,12 @@ SpamAssassin profile has been matched or exceeded. If you want to use the &%spam%& condition for its side effects (see the variables below), you can make it always return &"true"& by appending &`:true`& to the username. +.new .cindex "spam scanning" "returned variables" When the &%spam%& condition is run, it sets up a number of expansion variables. These variables are saved with the received message, thus they are available for use at delivery time. +.wen .vlist .vitem &$spam_score$& @@ -30968,8 +31048,8 @@ 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 @@ -33820,17 +33900,18 @@ 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 a non-trusted configuration file (i.e. the default configuration file or -one which is trusted by virtue of matching a prefix listed in the -TRUSTED_CONFIG_PREFIX_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%& +.new +If a non-trusted configuration file (i.e. not the default configuration file +or one which is trusted by virtue of being listed in the TRUSTED_CONFIG_LIST +file) is specified with &%-C%&, or if macros are given with &%-D%& (but see +the next item), then root privilege is retained only if the caller of Exim is +root. This locks out the possibility of testing a configuration using &%-C%& right through message reception and delivery, even if the caller is root. The reception works, but by that time, Exim is running as the Exim user, so when it re-execs to regain privilege for the delivery, the use of &%-C%& causes privilege to be lost. However, root can test reception and delivery using two separate commands. +.wen .next The WHITELIST_D_MACROS build option declares some macros to be safe to override with &%-D%& if the real uid is one of root, the Exim run-time user or the @@ -34157,6 +34238,13 @@ arbitrary program's being run as exim, not as root. +.section "Dynamic module directory" "SECTdynmoddir" +Any dynamically loadable modules must be installed into the directory +defined in &`LOOKUP_MODULE_DIR`& in &_Local/Makefile_& for Exim to permit +loading it. + + + .section "Use of sprintf()" "SECID279" .cindex "&[sprintf()]&" A large number of occurrences of &"sprintf"& in the code are actually calls to