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| -rw-r--r-- | doc/doc-docbook/spec.xfpt | 94 |
1 files changed, 59 insertions, 35 deletions
diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 6df8b9084..659a469bf 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -366,6 +366,7 @@ 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. @@ -1540,6 +1541,7 @@ is on a file system where the user is over quota. Exim can be configured to impose its own quotas on local mailboxes; where system quotas are set they will also apply. +.new 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 @@ -1550,7 +1552,7 @@ SMTP delivery has happened, it looks to see if any other messages are waiting for the same host. If any are found, they are sent over the same SMTP connection, subject to a configuration limit as to the maximum number in any one connection. - +.wen @@ -1892,8 +1894,9 @@ given in chapter &<<CHAPTLS>>&. -.section "Use of tcpwrappers" "SECID27" .new +.section "Use of tcpwrappers" "SECID27" + .cindex "tcpwrappers, building Exim to support" .cindex "USE_TCP_WRAPPERS" .cindex "TCP_WRAPPERS_DAEMON_NAME" @@ -1946,6 +1949,7 @@ support has not been tested for some time. +.new .section "Dynamically loaded lookup module support" "SECTdynamicmodules" .cindex "lookup modules" .cindex "dynamic modules" @@ -1974,7 +1978,7 @@ LOOKUP_LSEARCH=yes LOOKUP_SQLITE=2 LOOKUP_MYSQL=2 .endd - +.wen .section "The building process" "SECID29" .cindex "build directory" @@ -3279,6 +3283,7 @@ whose behaviour depends on the contents of an incoming message, you cannot test those conditions using &%-bt%&. The &%-N%& option provides a possible way of doing such tests. +.new .vitem &%-bV%& .oindex "&%-bV%&" .cindex "version number of Exim" @@ -3287,7 +3292,7 @@ number, and compilation date of the &'exim'& binary to the standard output. 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. - +.wen As part of its operation, &%-bV%& causes Exim to read and syntax check its configuration file. However, this is a static check only. It cannot check values that are to be expanded. For example, although a misspelt ACL verb is @@ -3353,7 +3358,6 @@ 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" @@ -3366,6 +3370,7 @@ 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. +.new 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. @@ -3383,7 +3388,7 @@ 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%&). - +.wen 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 start. In addition, the file name must not contain the sequence &`/../`&. @@ -3402,9 +3407,8 @@ 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" @@ -3414,6 +3418,7 @@ 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. +.new 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 @@ -3421,7 +3426,7 @@ 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 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 @@ -3437,7 +3442,7 @@ 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%&" @@ -3816,6 +3821,7 @@ by an admin user. This option causes the contents of the message body (-D) spool file to be written to the standard output. This option can be used only by an admin user. +.new .vitem &%-Mvc%&&~<&'message&~id'&> .oindex "&%-Mvc%&" .cindex "message" "listing in RFC 2822 format" @@ -3823,7 +3829,7 @@ written to the standard output. This option can be used only by an admin user. This option causes a copy of the complete message (header lines plus body) to be written to the standard output in RFC 2822 format. This option can be used only by an admin user. - +.wen .vitem &%-Mvh%&&~<&'message&~id'&> .oindex "&%-Mvh%&" .cindex "listing" "message headers" @@ -4561,7 +4567,7 @@ 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. - +.wen A default configuration file, which will work correctly in simple situations, is provided in the file &_src/configure.default_&. If CONFIGURE_FILE defines just one file name, the installation process copies the default @@ -4569,9 +4575,10 @@ 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 &<<CHAPdefconfil>>& is a &"walk-through"& discussion of the default configuration. -.wen + +.new .section "Using a different configuration file" "SECID40" .cindex "configuration file" "alternate" A one-off alternate configuration can be specified by the &%-C%& command line @@ -4594,7 +4601,7 @@ 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%&). - +.wen 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 start. In addition, the file name must not contain the sequence &"&`/../`&"&. @@ -9894,6 +9901,7 @@ ${if bool{$acl_m_privileged_sender} ... .wen +.new .vitem &*bool_lax&~{*&<&'string'&>&*}*& .cindex "expansion" "boolean parsing" .cindex "&%bool_lax%& expansion condition" @@ -9904,7 +9912,7 @@ 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. - +.wen .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "expansion" "encrypted comparison" .cindex "encrypted strings, comparing" @@ -12917,6 +12925,7 @@ 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. +.new .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: @@ -12925,7 +12934,7 @@ sophie:/var/run/sophie .endd If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. See section &<<SECTscanvirus>>& for further details. - +.wen .option bi_command main string unset @@ -15431,13 +15440,14 @@ 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. +.new 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. - +.wen .option tls_verify_hosts main "host list&!!" unset .cindex "TLS" "client certificate verification" @@ -15780,6 +15790,7 @@ This option is unique in that multiple &%condition%& options may be present. All &%condition%& options must succeed. .wen +.new 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: @@ -15790,18 +15801,18 @@ 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%&. - +.wen .option debug_print routers string&!! unset @@ -23779,6 +23790,7 @@ with the AUTH command (in contravention of the specification of LOGIN), but if the client does not supply it (as is the case for LOGIN clients), the prompt strings are used to obtain two data items. +.new Some clients are very particular about the precise text of the prompts. For example, Outlook Express is reported to recognize only &"Username:"& and &"Password:"&. Here is an example of a LOGIN authenticator that uses those @@ -23803,7 +23815,7 @@ 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" A number of string expansion features are provided for the purpose of @@ -28042,6 +28054,7 @@ 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. +.new .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 @@ -28055,7 +28068,7 @@ av_scanner = sophie:/var/run/sophie .endd 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: - +.wen .vlist .vitem &%aveserver%& .cindex "virus scanners" "Kaspersky" @@ -28067,6 +28080,7 @@ example: av_scanner = aveserver:/var/run/aveserver .endd +.new .vitem &%clamd%& .cindex "virus scanners" "clamd" This daemon-type scanner is GPL and free. You can get it at @@ -28089,7 +28103,7 @@ 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. - +.wen .vitem &%cmdline%& .cindex "virus scanners" "command line interface" This is the keyword for the generic command line scanner interface. It can be @@ -28363,12 +28377,13 @@ available for use at delivery time. The spam score of the message, for example &"3.4"& or &"30.5"&. This is useful for inclusion in log or reject messages. +.new .vitem &$spam_score_int$& The spam score of the message, multiplied by ten, as an integer value. For example &"34"& or &"305"&. It may appear to disagree with &$spam_score$& because &$spam_score$& is rounded and &$spam_score_int$& is truncated. The integer value is useful for numeric comparisons in conditions. - +.wen .vitem &$spam_bar$& A string consisting of a number of &"+"& or &"-"& characters, representing the @@ -31055,9 +31070,10 @@ 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. +.new 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. - +.wen 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 standard output in a stylized way that the calling program should be able to @@ -33902,12 +33918,13 @@ value of the &%-C%& option is identical to the value of CONFIGURE_FILE in &_Local/Makefile_&, Exim ignores &%-C%& and proceeds as usual.) There is no default setting for &%ALT_CONFIG_PREFIX%&. +.new If the permitted configuration files are confined to a directory to 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 -.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 @@ -33918,7 +33935,7 @@ 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 @@ -33937,7 +33954,7 @@ option, but it cannot be overridden; the runtime option adds additional users to the list. The default setting is &"root"&; this prevents a non-root user who is permitted to modify the runtime file from using Exim as a way to get root. .endlist - +.wen @@ -33977,6 +33994,7 @@ abdication; the process cannot regain root afterwards. Prior to release 4.00, After a new Exim process has interpreted its command line options, it changes uid and gid in the following cases: +.new .ilist .oindex "&%-C%&" .oindex "&%-D%&" @@ -34010,7 +34028,7 @@ option). For a daemon, queue runner, delivery, or address testing process, the uid remains as root at this stage, but the gid is changed to the Exim group. .endlist - +.wen The processes that initially retain root privilege behave as follows: .ilist @@ -34245,11 +34263,12 @@ arbitrary program's being run as exim, not as root. +.new .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. - +.wen .section "Use of sprintf()" "SECID279" @@ -34608,6 +34627,7 @@ unqualified domain &'foundation'&. Since version 4.70, DKIM support is compiled into Exim by default. It can be disabled by setting DISABLE_DKIM=yes in Local/Makefile. +.new Exim's DKIM implementation allows to .olist Sign outgoing messages: This function is implemented in the SMTP transport. @@ -34617,7 +34637,7 @@ Verify signatures in incoming messages: This is implemented by an additional ACL (acl_smtp_dkim), which can be called several times per message, with different signature contexts. .endlist - +.wen In typical Exim style, the verification implementation does not include any default "policy". Instead it enables you to build your own policy using Exim's standard controls. @@ -34642,6 +34662,7 @@ senders). Signing is implemented by setting private options on the SMTP transport. These options take (expandable) strings as arguments. +.new .option dkim_domain smtp string&!! unset MANDATORY: The domain you want to sign with. The result of this expanded @@ -34691,7 +34712,7 @@ When set, this option must expand to (or be specified as) a colon-separated list of header names. Headers with these names will be included in the message signature. When unspecified, the header names recommended in RFC4871 will be used. - +.wen .section "Verifying DKIM signatures in incoming mail" "SECID514" .cindex "DKIM" "verification" @@ -34709,6 +34730,7 @@ more advanced policies. For that reason, the global option &%dkim_verify_signers%&, and a global expansion variable &%$dkim_signers%& exist. +.new 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, @@ -34731,7 +34753,7 @@ You can also be more creative in constructing your policy. For example: .code dkim_verify_signers = $sender_address_domain:$dkim_signers .endd - +.wen If a domain or identity is listed several times in the (expanded) value of &%dkim_verify_signers%&, the ACL is only called once for that domain or identity. @@ -34739,6 +34761,7 @@ 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): +.new .vlist .vitem &%$dkim_cur_signer%& The signer that is being evaluated in this ACL run. This can be a domain or @@ -34823,16 +34846,17 @@ in the key record. .vitem &%$dkim_key_notes%& Notes from the key record (tag n=). .endlist - +.wen In addition, two ACL conditions are provided: +.new .vlist .vitem &%dkim_signers%& ACL condition that checks a colon-separated list of domains or identities for a match against the domain or identity that the ACL is currently verifying (reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL verb to a group of domains or identities. For example: - +.wen .code # Warn when message apparently from GMail has no signature at all warn log_message = GMail sender without DKIM signature |