X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/5d9c27ecfbf6ac99d49c3e72e14737e1407c8d59..5ca6d115da010e279c2f928990b3c8d220378f24:/doc/doc-docbook/spec.xfpt?ds=inline diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index fa29a2524..6a671cd42 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -1,4 +1,4 @@ -. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.57 2009/10/16 08:49:47 tom Exp $ +. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.66 2009/11/05 19:37:00 nm4 Exp $ . . ///////////////////////////////////////////////////////////////////////////// . This is the primary source of the Exim Manual. It is an xfpt document that is @@ -172,15 +172,13 @@ Specification of the Exim Mail Transfer Agent The Exim MTA -09 June 2009 -PhilipHazel -PH -University of Cambridge Computing Service -
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
+5 November 2009 +EximMaintainers +EM 4.70 - 10 June 2009 - PH + 5 November 2009 + EM 2009University of Cambridge @@ -728,12 +726,14 @@ 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 @@ -2221,12 +2221,14 @@ 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 @@ -2989,11 +2991,13 @@ 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%&" @@ -5891,9 +5895,11 @@ 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 @@ -5913,12 +5919,14 @@ 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 @@ -6138,7 +6146,7 @@ IPv6 addresses must be enclosed in quotes to prevent the first internal colon being interpreted as a key terminator. For example: .code 1.2.3.4: data for 1.2.3.4 -192.168.0.0/16 data for 192.168.0.0/16 +192.168.0.0/16: data for 192.168.0.0/16 "abcd::cdab": data for abcd::cdab "abcd:abcd::/32" data for abcd:abcd::/32 .endd @@ -9742,6 +9750,7 @@ 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" @@ -9757,6 +9766,7 @@ For example, .code ${if bool{$acl_m_privileged_sender} ... .endd +.wen .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "expansion" "encrypted comparison" @@ -10209,10 +10219,12 @@ 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:$auth3}} .endd +.wen .vitem &*queue_running*& .cindex "queue runner" "detecting when delivering from" .cindex "expansion" "queue runner test" @@ -10999,10 +11011,12 @@ doing a delivery in maildir format, the value of &$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$&" -While running an ACL at the time of an SMTP RCPT command, &$message_size$& +While running a per message ACL (mail/rcpt/predata), &$message_size$& contains the size supplied on the MAIL command, or -1 if no size was given. The value may not, of course, be truthful. +.wen .vitem &$mime_$&&'xxx'& A number of variables whose names start with &$mime$& are @@ -12368,6 +12382,7 @@ listed in more than one group. .row &%gnutls_require_kx%& "control GnuTLS key exchanges" .row &%gnutls_require_mac%& "control GnuTLS MAC algorithms" .row &%gnutls_require_protocols%& "control GnuTLS protocols" +.row &%gnutls_compat_mode%& "use GnuTLS compatibility mode" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" .row &%tls_certificate%& "location of server certificate" .row &%tls_crl%& "certificate revocation list" @@ -13367,6 +13382,12 @@ 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 @@ -13438,10 +13459,10 @@ do. By default, Exim just checks the syntax of HELO and EHLO commands (see &%helo_accept_junk_hosts%& and &%helo_allow_chars%&). However, some sites like to do more extensive checking of the data supplied by these commands. The ACL -condition &`verify`& &`=`& &`helo`& is provided to make this possible. +condition &`verify = helo`& is provided to make this possible. Formerly, it was necessary also to set this option (&%helo_try_verify_hosts%&) to force the check to occur. From release 4.53 onwards, this is no longer -necessary. If the check has not been done before &`verify`& &`=`& &`helo`& is +necessary. If the check has not been done before &`verify = helo`& is encountered, it is done at that time. Consequently, this option is obsolete. Its specification is retained here for backwards compatibility. @@ -13463,7 +13484,7 @@ 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" @@ -13519,8 +13540,8 @@ 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`& @@ -17840,10 +17861,12 @@ redirection items of the form :defer: :fail: .endd -respectively. When a redirection list contains such an item, it applies to the -entire redirection; any other items in the list are ignored (&':blackhole:'& is -different). Any text following &':fail:'& or &':defer:'& is placed in the error -text associated with the failure. For example, an alias file might contain: +.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 @@ -18987,10 +19010,12 @@ 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 @@ -21467,6 +21492,13 @@ client. For details, see section &<>&. 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 +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" .cindex "EHLO" "argument, setting" @@ -23559,6 +23591,7 @@ login: 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 @@ -23566,7 +23599,7 @@ 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" @@ -24443,13 +24476,10 @@ unencrypted. The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)& transport provide the client with a certificate, which is passed to the server if it requests it. If the server is Exim, it will request a certificate only if -&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&: -These options must be set in the &(smtp)& transport for Exim to use TLS when it -is operating as a client. Exim does not assume that a server certificate (set -by the global options of the same name) should also be used when operating as a -client. +&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. -If &%tls_verify_certificates%& is set, it must name a file or, +If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it +must name a file or, for OpenSSL only (not GnuTLS), a directory, that contains a collection of expected server certificates. The client verifies the server's certificate against this collection, taking into account any revoked certificates that are @@ -24461,6 +24491,14 @@ 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 "&$host_address$&" All the TLS options in the &(smtp)& transport are expanded before use, with @@ -24795,7 +24833,7 @@ 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 @@ -24803,6 +24841,7 @@ 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%& @@ -25796,7 +25835,7 @@ 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). @@ -25809,7 +25848,7 @@ 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 @@ -25838,12 +25877,12 @@ 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 @@ -26989,7 +27028,7 @@ entry must set the rate for the same key (otherwise it will always be zero). For example: .code acl_check_connect: - deny ratelimit = 100 / 5m / strict / noupdate + deny ratelimit = 100 / 5m / strict / per_cmd / noupdate log_message = RATE: $sender_rate/$sender_rate_period \ (max $sender_rate_limit) .endd @@ -27584,10 +27623,12 @@ the third string (in this case &"1"&), whether or not the cryptographic and timeout checks succeed. The &$prvscheck_result$& variable contains the result of the checks (empty for failure, &"1"& for success). +.new There is one more issue you must consider when implementing prvs-signing: you have to ensure that the routers accept prvs-signed addresses and deliver them correctly. The easiest way to handle this is to use a &(redirect)& router to remove the signature with a configuration along these lines: +.wen .code batv_redirect: driver = redirect @@ -34300,6 +34341,7 @@ unqualified domain &'foundation'&. . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// +.new .chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&& "DKIM Support" .cindex "DKIM" @@ -34406,39 +34448,48 @@ runtime of the ACL. Calling the ACL only for existing signatures is not sufficient to build more advanced policies. For that reason, the global option &%dkim_verify_signers%&, and a global expansion variable -&%$dkim_signing_domains%& exist. +&%$dkim_signers%& exist. The global option &%dkim_verify_signers%& can be set to a colon-separated list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is called. It is expanded when the message has been received. At this point, -the expansion variable &%$dkim_signing_domains%& already contains a colon- -separated list of signer domains for the message. When &%dkim_verify_signers%& -is not specified in the main configuration, it defaults as: +the expansion variable &%$dkim_signers%& already contains a colon- +separated list of signer domains and identities for the message. When +&%dkim_verify_signers%& is not specified in the main configuration, +it defaults as: .code -dkim_verify_signers = $dkim_signing_domains +dkim_verify_signers = $dkim_signers .endd This leads to the default behaviour of calling &%acl_smtp_dkim%& for each DKIM signature in the message. Current DKIM verifiers may want to explicitly call the ACL for known domains or identities. This would be achieved as follows: .code -dkim_verify_signers = paypal.com:ebay.com:$dkim_signing_domains +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 that have signatures in the message. You can -also be more creative in constructing your policy. Example: +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: .code -dkim_verify_signers = $sender_address_domain:$dkim_signing_domains +dkim_verify_signers = $sender_address_domain:$dkim_signers .endd +If a domain or identity is listed several times in the (expanded) value of +&%dkim_verify_signers%&, the ACL is only called once for that domain or identity. + + Inside the &%acl_smtp_dkim%&, the following expansion variables are available (from most to least important): .vlist +.vitem &%$dkim_cur_signer%& +The signer that is being evaluated in this ACL run. This can be domain or +an identity. This is one of the list items from the expanded main option +&%dkim_verify_signers%& (see above). .vitem &%$dkim_verify_status%& A string describing the general status of the signature. One of .ilist &%none%&: There is no signature in the message for the current domain or -identity. +identity (as reflected by &%$dkim_cur_signer%&). .next &%invalid%&: The signature could not be verified due to a processing error. More detail is available in &%$dkim_verify_reason%&. @@ -34469,14 +34520,12 @@ DKIM verification. It may of course also mean that the signature is forged. .endlist .vitem &%$dkim_domain%& The signing domain. IMPORTANT: This variable is only populated if there is -ab actual signature in the message. It does NOT neccessarily carry the -domain that is currently being evaluated. Please use the &%dkim_signers%& ACL -condition for that. +an actual signature in the message for the current domain or identity (as +reflected by &%$dkim_cur_signer%&). .vitem &%$dkim_identity%& -The signing identity. IMPORTANT: This variable is only populated if there is -ab actual signature in the message. It does NOT neccessarily carry the -identity that is currently being evaluated. Please use the &%dkim_signers%& ACL -condition for that. +The signing identity, if present. IMPORTANT: This variable is only populated +if there is an actual signature in the message for the current domain or +identity (as reflected by &%$dkim_cur_signer%&). .vitem &%$dkim_selector%& The key record selector string .vitem &%$dkim_algo%& @@ -34521,8 +34570,9 @@ In addition, two ACL conditions are provided: .vlist .vitem &%dkim_signers%& ACL condition that checks a colon-separated list of domains or identities -for a match against the domain or identity that the ACL is currently verifying. -This is typically used to restrict an ACL verb to a group of domains or identities, like: +for a match against the domain or identity that the ACL is currently verifying +(reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL +verb to a group of domains or identities, like: .code # Warn when message apparently from GMail has no signature at all @@ -34548,7 +34598,7 @@ The possible status keywords are: 'none','invalid','fail' and 'pass'. Please see the documentation of the &%$dkim_verify_status%& expansion variable above for more information of what they mean. .endlist - +.wen . //////////////////////////////////////////////////////////////////////////// . ////////////////////////////////////////////////////////////////////////////