X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/ecc5f51aca286f528e46dade1cf50776e8e38d02..ddf1b11a732e293cd242c80bc63d459dda595bf4:/doc/doc-docbook/spec.xfpt?ds=sidebyside diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 174873d07..a6d477680 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -2627,6 +2627,8 @@ users to set envelope senders. .cindex "&'From:'& header line" .cindex "&'Sender:'& header line" +.cindex "header lines" "From:" +.cindex "header lines" "Sender:" For a trusted user, there is never any check on the contents of the &'From:'& header line, and a &'Sender:'& line is never added. Furthermore, any existing &'Sender:'& line in incoming local (non-TCP/IP) messages is not removed. @@ -5134,7 +5136,11 @@ with the characters &"0x"&, in which case the remainder is interpreted as a hexadecimal number. If an integer value is followed by the letter K, it is multiplied by 1024; if -it is followed by the letter M, it is multiplied by 1024x1024. When the values +it is followed by the letter M, it is multiplied by 1024x1024; +.new +if by the letter G, 1024x1024x1024. +.wen +When the values of integer option settings are output, values which are an exact multiple of 1024 or 1024x1024 are sometimes, but not always, printed using the letters K and M. The printing style is independent of the actual input format that was @@ -6262,7 +6268,11 @@ Chapter &<>& covers both. Exim supports the use of regular expressions in many of its options. It uses the PCRE regular expression library; this provides regular expression matching that is compatible with Perl 5. The syntax and semantics of -regular expressions is discussed in many Perl reference books, and also in +regular expressions is discussed in +.new +online Perl manpages, in +.wen +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/)). @@ -9213,8 +9223,8 @@ The environment is adjusted by the &%keep_environment%& and .cindex "&%extract%&" "substrings by key" The key and <&'string1'&> are first expanded separately. Leading and trailing white space is removed from the key (but not from any of the strings). The key -must not consist entirely of digits. The expanded <&'string1'&> must be of the -form: +must not be empty and must not consist entirely of digits. +The expanded <&'string1'&> must be of the form: .display <&'key1'&> = <&'value1'&> <&'key2'&> = <&'value2'&> ... .endd @@ -10090,6 +10100,21 @@ Last:user@example.com user@example.com .endd +.new +.vitem &*${base32:*&<&'digits'&>&*}*& +.cindex "&%base32%& expansion item" +.cindex "expansion" "conversion to base 32" +The string must consist entirely of decimal digits. The number is converted to +base 32 and output as a (empty, for zero) string of characters. +Only lowercase letters are used. + +.vitem &*${base32d:*&<&'base-32&~digits'&>&*}*& +.cindex "&%base32d%& expansion item" +.cindex "expansion" "conversion to base 32" +The string must consist entirely of base-32 digits. +The number is converted to decimal and output as a string. +.wen + .vitem &*${base62:*&<&'digits'&>&*}*& .cindex "&%base62%& expansion item" .cindex "expansion" "conversion to base 62" @@ -10141,6 +10166,15 @@ escape sequences starting with a backslash. Whether characters with the most significant bit set (so-called &"8-bit characters"&) count as printing or not is controlled by the &%print_topbitchars%& option. +.new +.vitem &*${escape8bit:*&<&'string'&>&*}*& +.cindex "expansion" "escaping 8-bit characters" +.cindex "&%escape8bit%& expansion item" +If the string contains and characters with the most significant bit set, +they are converted to escape sequences starting with a backslash. +Backslashes and DEL characters are also converted. +.wen + .vitem &*${eval:*&<&'string'&>&*}*&&~and&~&*${eval10:*&<&'string'&>&*}*& .cindex "expansion" "expression evaluation" @@ -10514,7 +10548,7 @@ variables or headers inside regular expressions. .cindex "SHA-1 hash" .cindex "expansion" "SHA-1 hashing" .cindex certificate fingerprint -.cindex "&%sha2%& expansion item" +.cindex "&%sha1%& expansion item" The &%sha1%& operator computes the SHA-1 hash value of the string, and returns it as a 40-digit hexadecimal number, in which any letters are in upper case. @@ -10522,16 +10556,38 @@ If the string is a single variable of type certificate, returns the SHA-1 hash fingerprint of the certificate. -.vitem &*${sha256:*&<&'certificate'&>&*}*& +.vitem &*${sha256:*&<&'string'&>&*}*& .cindex "SHA-256 hash" .cindex certificate fingerprint .cindex "expansion" "SHA-256 hashing" .cindex "&%sha256%& expansion item" -The &%sha256%& operator computes the SHA-256 hash fingerprint of the -certificate, +.new +The &%sha256%& operator computes the SHA-256 hash value of the string and returns it as a 64-digit hexadecimal number, in which any letters are in upper case. -Only arguments which are a single variable of certificate type are supported. +.wen + +If the string is a single variable of type certificate, +returns the SHA-256 hash fingerprint of the certificate. + + +.new +.vitem &*${sha3:*&<&'string'&>&*}*& &&& + &*${sha3_:*&<&'string'&>&*}*& +.cindex "SHA3 hash" +.cindex "expansion" "SHA3 hashing" +.cindex "&%sha3%& expansion item" +The &%sha3%& operator computes the SHA3-256 hash value of the string +and returns +it as a 64-digit hexadecimal number, in which any letters are in upper case. + +If a number is appended, separated by an underbar, it specifies +the output length. Values of 224, 256, 384 and 512 are accepted; +with 256 being the default. + +The &%sha3%& expansion item is only supported if Exim has been +compiled with GnuTLS 3.5.0 or later. +.wen .vitem &*${stat:*&<&'string'&>&*}*& @@ -12816,7 +12872,7 @@ When a message is received from a remote host over an encrypted SMTP connection, this variable is set to the cipher suite that was negotiated, for example DES-CBC3-SHA. In other circumstances, in particular, for message received over unencrypted connections, the variable is empty. Testing -&$tls_cipher$& for emptiness is one way of distinguishing between encrypted and +&$tls_in_cipher$& for emptiness is one way of distinguishing between encrypted and non-encrypted connections during ACL processing. The deprecated &$tls_cipher$& variable is the same as &$tls_in_cipher$& during message reception, @@ -12951,8 +13007,7 @@ or external command, as described above. It is also used during a .vitem &$verify_mode$& .vindex "&$verify_mode$&" -While a router or transport is being run in verify mode -or for cutthrough delivery, +While a router or transport is being run in verify mode or for cutthrough delivery, contains "S" for sender-verification or "R" for recipient-verification. Otherwise, empty. @@ -13779,6 +13834,7 @@ See also the &'Policy controls'& section above. .table2 .row &%accept_8bitmime%& "advertise 8BITMIME" .row &%auth_advertise_hosts%& "advertise AUTH to these hosts" +.row &%chunking_advertise_hosts%& "advertise CHUNKING to these hosts" .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts" .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts" .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP" @@ -14268,11 +14324,15 @@ $primary_hostname-$tod_epoch-testing See section &<>& for details of how this value is used. -.option check_log_inodes main integer 0 +.new +.option check_log_inodes main integer 100 +.wen See &%check_spool_space%& below. -.option check_log_space main integer 0 +.new +.option check_log_space main integer 10M +.wen See &%check_spool_space%& below. .oindex "&%check_rfc2047_length%&" @@ -14287,11 +14347,15 @@ of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is set false, Exim recognizes encoded words of any length. -.option check_spool_inodes main integer 0 +.new +.option check_spool_inodes main integer 100 +.wen See &%check_spool_space%& below. -.option check_spool_space main integer 0 +.new +.option check_spool_space main integer 10M +.wen .cindex "checking disk space" .cindex "disk space, checking" .cindex "spool directory" "checking space" @@ -14302,7 +14366,7 @@ message is accepted. .vindex "&$log_space$&" .vindex "&$spool_inodes$&" .vindex "&$spool_space$&" -When any of these options are set, they apply to all incoming messages. If you +When any of these options are nonzero, they apply to all incoming messages. If you want to apply different checks to different kinds of message, you can do so by testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and &$spool_space$& in an ACL with appropriate additional conditions. @@ -14311,7 +14375,7 @@ testing the variables &$log_inodes$&, &$log_space$&, &$spool_inodes$&, and &%check_spool_space%& and &%check_spool_inodes%& check the spool partition if either value is greater than zero, for example: .code -check_spool_space = 10M +check_spool_space = 100M check_spool_inodes = 100 .endd The spool partition is the one that contains the directory defined by @@ -14330,12 +14394,29 @@ SIZE parameter on the MAIL command, its value is added to the &%check_spool_space%& is zero, unless &%no_smtp_check_spool_space%& is set. The values for &%check_spool_space%& and &%check_log_space%& are held as a -number of kilobytes. If a non-multiple of 1024 is specified, it is rounded up. +number of kilobytes (though specified in bytes). +If a non-multiple of 1024 is specified, it is rounded up. For non-SMTP input and for batched SMTP input, the test is done at start-up; on failure a message is written to stderr and Exim exits with a non-zero code, as it obviously cannot send an error message of any kind. +.new +There is a slight performance penalty for these checks. +Versions of Exim preceding 4.88 had these disabled by default; +high-rate intallations confident they will never run out of resources +may wish to deliberately disable them. +.wen + +.new +.option chunking_advertise_hosts main "host list&!!" * +.cindex CHUNKING advertisement +.cindex "RFC 3030" "CHUNKING" +The CHUNKING extension (RFC3030) will be advertised in the EHLO message to +these hosts. +Hosts may use the BDAT command as an alternate to DATA. +.wen + .option daemon_smtp_ports main string &`smtp`& .cindex "port" "for daemon" .cindex "TCP/IP" "setting listening ports" @@ -15955,7 +16036,7 @@ the daemon's command line. .new .cindex queues named -.condex "named queues" +.cindex "named queues" To set limits for different named queues use an expansion depending on the &$queue_name$& variable. .wen @@ -16975,7 +17056,7 @@ in IKE is assigned number 23. Otherwise, the option must expand to the name used by Exim for any of a number of DH primes specified in RFC 2409, RFC 3526 and RFC 5114. As names, Exim uses -"ike" followed by the number used by IKE, of "default" which corresponds to +"ike" followed by the number used by IKE, or "default" which corresponds to "ike23". The available primes are: @@ -17550,7 +17631,7 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence. .cindex "DNSSEC" "MX lookup" .cindex "security" "MX lookup" .cindex "DNS" "DNSSEC" -DNS lookups for domains matching &%dnssec_request_domains%& will be done with +DNS lookups for domains matching &%dnssec_require_domains%& will be done with the dnssec request bit set. Any returns not having the Authenticated Data bit (AD bit) set will be ignored and logged as a host-lookup failure. This applies to all of the SRV, MX, AAAA, A lookup sequence. @@ -19851,12 +19932,17 @@ list1: :include:/opt/lists/list1 .endd .next .cindex "address redirection" "to black hole" -Sometimes you want to throw away mail to a particular local part. Making the -&%data%& option expand to an empty string does not work, because that causes -the router to decline. Instead, the alias item +.cindex "delivery" "discard" +.cindex "delivery" "blackhole" .cindex "black hole" .cindex "abandoning mail" -&':blackhole:'& can be used. It does what its name implies. No delivery is +Sometimes you want to throw away mail to a particular local part. Making the +&%data%& option expand to an empty string does not work, because that causes +the router to decline. Instead, the alias item +.code +:blackhole: +.endd +can be used. It does what its name implies. No delivery is done, and no error message is generated. This has the same effect as specifying &_/dev/null_& as a destination, but it can be independently disabled. @@ -20826,7 +20912,7 @@ is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. Unlike most options, &%headers_remove%& can be specified multiple times -for a router; all listed headers are removed. +for a transport; all listed headers are removed. &*Warning*&: Because of the separate expansion of the list items, items that contain a list separator must have it doubled. @@ -23594,7 +23680,7 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence. .cindex "DNSSEC" "MX lookup" .cindex "security" "MX lookup" .cindex "DNS" "DNSSEC" -DNS lookups for domains matching &%dnssec_request_domains%& will be done with +DNS lookups for domains matching &%dnssec_require_domains%& will be done with the dnssec request bit set. Any returns not having the Authenticated Data bit (AD bit) set will be ignored and logged as a host-lookup failure. This applies to all of the SRV, MX, AAAA, A lookup sequence. @@ -23849,6 +23935,16 @@ connects. If authentication fails, Exim will try to transfer the message unauthenticated. See also &%hosts_require_auth%&, and chapter &<>& for details of authentication. +.new +.option hosts_try_chunking smtp "host list&!!" * +.cindex CHUNKING "enabling, in client" +.cindex BDAT "SMTP command" +.cindex "RFC 3030" "CHUNKING" +This option provides a list of server to which, provided they announce +CHUNKING support, Exim will attempt to use BDAT commands rather than DATA. +BDAT will not be used in conjuction with a transport filter. +.wen + .option hosts_try_prdr smtp "host list&!!" * .cindex "PRDR" "enabling, optional in client" This option provides a list of servers to which, provided they announce @@ -27719,6 +27815,17 @@ received, before the final response to the DATA command is sent. This is the ACL specified by &%acl_smtp_data%&, which is the second ACL that is associated with the DATA command. +.new +.cindex CHUNKING "BDAT command" +.cindex BDAT "SMTP command" +.cindex "RFC 3030" CHUNKING +If CHUNKING was advertised and a BDAT command sequence is received, +the &%acl_smtp_predata%& ACL is not run. +. XXX why not? It should be possible, for the first BDAT. +The &%acl_smtp_data%& is run after the last BDAT command and all of +the data specified is received. +.wen + For both of these ACLs, it is not possible to reject individual recipients. An error response rejects the entire message. Unfortunately, it is known that some MTAs do not treat hard (5&'xx'&) responses to the DATA command (either @@ -28040,7 +28147,7 @@ provides a means of specifying an &"and"& conjunction between conditions. For example: .code deny dnslists = list1.example -dnslists = list2.example + dnslists = list2.example .endd If there are no conditions, the verb is always obeyed. Exim stops evaluating the conditions and modifiers when it reaches a condition that fails. What @@ -28062,8 +28169,8 @@ after &%endpass%&, the ACL returns &"deny"&. Consider this statement, used to check a RCPT command: .code accept domains = +local_domains -endpass -verify = recipient + endpass + verify = recipient .endd If the recipient domain does not match the &%domains%& condition, control passes to the next statement. If it does match, the recipient is verified, and @@ -28714,7 +28821,7 @@ Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. -.vitem &*control&~=&~cutthrough_delivery*& +.vitem &*control&~=&~cutthrough_delivery/*&<&'options'&> .cindex "&ACL;" "cutthrough routing" .cindex "cutthrough" "requesting" This option requests delivery be attempted while the item is being received. @@ -28754,11 +28861,20 @@ It is not supported for messages received with the SMTP PRDR option in use. Should the ultimate destination system positively accept or reject the mail, a corresponding indication is given to the source system and nothing is queued. -If there is a temporary error the item is queued for later delivery in the -usual fashion. If the item is successfully delivered in cutthrough mode +If the item is successfully delivered in cutthrough mode the delivery log lines are tagged with ">>" rather than "=>" and appear before the acceptance "<=" line. +.new +If there is a temporary error the item is queued for later delivery in the +usual fashion. +This behaviour can be adjusted by appending the option &*defer=*&<&'value'&> +to the control; the default value is &"spool"& and the alternate value +&"pass"& copies an SMTP defer response from the target back to the initiator +and does not queue the message. +Note that this is independent of any receipient verify conditions in the ACL. +.wen + Delivery in this mode avoids the generation of a bounce mail to a (possibly faked) sender when the destination system is doing content-scan based rejection. @@ -28772,13 +28888,18 @@ 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 +option. +.new +Logging may be stopped, and the file removed, with the &'kill'& option. +.wen +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 + control = debug/kill .endd @@ -29017,7 +29138,7 @@ any ACL verb, including &%deny%& (though this is potentially useful only in a RCPT ACL). Headers will not be added to the message if the modifier is used in -DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing. +DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing. Leading and trailing newlines are removed from the data for the &%add_header%& modifier; if it then @@ -29118,8 +29239,8 @@ receiving a message). The message must ultimately be accepted for with any ACL verb, including &%deny%&, though this is really not useful for any verb that doesn't result in a delivered message. -Headers will not be removed to the message if the modifier is used in -DATA, MIME or DKIM ACLs for messages delivered by cutthrough routing. +Headers will not be removed from the message if the modifier is used in +DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing. More than one header can be removed at the same time by using a colon separated list of header names. The header matching is case insensitive. Wildcards are @@ -31497,7 +31618,7 @@ condition defers. Unix and TCP socket specifications may be mixed in any order. Each element of the list is a list itself, space-separated by default -and changeable in the usual way. +and changeable in the usual way; take care to not double the separator. For TCP socket specifications a host name or IP (v4 or v6, but subject to list-separator quoting rules) address can be used, @@ -31624,6 +31745,11 @@ spam bar is 50 characters. A multiline text table, containing the full SpamAssassin report for the message. Useful for inclusion in headers or reject messages. This variable is only usable in a DATA-time ACL. +.new +Beware that SpamAssassin may return non-ASCII characters, especially +when running in country-specific locales, which are not legal +unencoded in headers. +.wen .vitem &$spam_action$& For SpamAssassin either 'reject' or 'no action' depending on the @@ -33209,6 +33335,7 @@ incoming SMTP message from a source that is not permitted to send them. .section "Resent- header lines" "SECID220" .cindex "&%Resent-%& header lines" +.cindex "header lines" "Resent-" RFC 2822 makes provision for sets of header lines starting with the string &`Resent-`& to be added to a message when it is resent by the original recipient to somebody else. These headers are &'Resent-Date:'&, @@ -33265,6 +33392,7 @@ existing &'Bcc:'& is not removed. .section "The Date: header line" "SECID223" .cindex "&'Date:'& header line" +.cindex "header lines" "Date:" If a locally-generated or submission-mode message has no &'Date:'& header line, Exim adds one, using the current date and time, unless the &%suppress_local_fixups%& control has been specified. @@ -33282,6 +33410,7 @@ messages. .section "The Envelope-to: header line" "SECID225" .cindex "&'Envelope-to:'& header line" +.cindex "header lines" "Envelope-to:" .oindex "&%envelope_to_remove%&" &'Envelope-to:'& header lines are not part of the standard RFC 2822 header set. Exim can be configured to add them to the final delivery of messages. (See the @@ -33293,6 +33422,7 @@ messages. .section "The From: header line" "SECTthefrohea" .cindex "&'From:'& header line" +.cindex "header lines" "From:" .cindex "Sendmail compatibility" "&""From""& line" .cindex "message" "submission" .cindex "submission mode" @@ -33336,6 +33466,7 @@ name as described in section &<>&. .section "The Message-ID: header line" "SECID226" .cindex "&'Message-ID:'& header line" +.cindex "header lines" "Message-ID:" .cindex "message" "submission" .oindex "&%message_id_header_text%&" If a locally-generated or submission-mode incoming message does not contain a @@ -33351,6 +33482,7 @@ in this header line by setting the &%message_id_header_text%& and/or .section "The Received: header line" "SECID227" .cindex "&'Received:'& header line" +.cindex "header lines" "Received:" A &'Received:'& header line is added at the start of every message. The contents are defined by the &%received_header_text%& configuration option, and Exim automatically adds a semicolon and a timestamp to the configured string. @@ -33367,6 +33499,7 @@ changed to the time of acceptance, which is (apart from a small delay while the .section "The References: header line" "SECID228" .cindex "&'References:'& header line" +.cindex "header lines" "References:" Messages created by the &(autoreply)& transport include a &'References:'& header line. This is constructed according to the rules that are described in section 3.64 of RFC 2822 (which states that replies should contain such a @@ -33381,6 +33514,7 @@ incoming message. If there are more than 12, the first one and then the final .section "The Return-path: header line" "SECID229" .cindex "&'Return-path:'& header line" +.cindex "header lines" "Return-path:" .oindex "&%return_path_remove%&" &'Return-path:'& header lines are defined as something an MTA may insert when it does the final delivery of messages. (See the generic &%return_path_add%& @@ -33393,6 +33527,7 @@ default), Exim removes &'Return-path:'& header lines from incoming messages. .section "The Sender: header line" "SECTthesenhea" .cindex "&'Sender:'& header line" .cindex "message" "submission" +.cindex "header lines" "Sender:" For a locally-originated message from an untrusted user, Exim may remove an existing &'Sender:'& header line, and it may add a new one. You can modify these actions by setting the &%local_sender_retain%& option true, the @@ -35361,6 +35496,7 @@ picked out by the distinctive two-character flags that immediately follow the timestamp. The flags are: .display &`<=`& message arrival +&`(=`& message fakereject &`=>`& normal message delivery &`->`& additional address in same delivery &`>>`& cutthrough message delivery @@ -35588,14 +35724,17 @@ the following table: &`CV `& certificate verification status &`D `& duration of &"no mail in SMTP session"& &`DN `& distinguished name from peer certificate +&`DS `& DNSSEC secured lookups &`DT `& on &`=>`& lines: time taken for a delivery &`F `& sender address (on delivery lines) &`H `& host name and IP address &`I `& local interface used +&`K `& CHUNKING extension used &`id `& message id for incoming message &`P `& on &`<=`& lines: protocol used &` `& on &`=>`& and &`**`& lines: return path -&`PRX `& on &'<='& and&`=>`& lines: proxy address +&`PRDR`& PRDR extension used +&`PRX `& on &`<=`& and &`=>`& lines: proxy address &`Q `& alternate queue name &`QT `& on &`=>`& lines: time spent on queue so far &` `& on &"Completed"& lines: time spent on queue @@ -35679,6 +35818,7 @@ selection marked by asterisks: &` deliver_time `& time taken to perform delivery &` delivery_size `& add &`S=`&&'nnn'& to => lines &`*dnslist_defer `& defers of DNS list (aka RBL) lookups +&` dnssec `& DNSSEC secured lookups &`*etrn `& ETRN commands &`*host_lookup_failed `& as it says &` ident_timeout `& timeout for ident connection @@ -35786,6 +35926,14 @@ the &"=>"& line, tagged with S=. &%dnslist_defer%&: A log entry is written if an attempt to look up a host in a DNS black list suffers a temporary error. .next +.cindex log dnssec +.cindex dnssec logging +&%dnssec%&: For message acceptance and (attempted) delivery log lines, when +dns lookups gave secure results a tag of DS is added. +For acceptance this covers the reverse and forward lookups for host name verification. +It does not cover helo-name verification. +For delivery this covers the SRV, MX, A and/or AAAA lookups. +.next .cindex "log" "ETRN commands" .cindex "ETRN" "logging" &%etrn%&: Every valid ETRN command that is received is logged, before the ACL @@ -37985,14 +38133,14 @@ DKIM is documented in RFC 4871. DKIM support is compiled into Exim by default if TLS support is present. It can be disabled by setting DISABLE_DKIM=yes in &_Local/Makefile_&. -Exim's DKIM implementation allows to +Exim's DKIM implementation allows for .olist -Sign outgoing messages: This function is implemented in the SMTP transport. +Signing outgoing messages: This function is implemented in the SMTP transport. It can co-exist with all other Exim features (including transport filters) except cutthrough delivery. .next -Verify signatures in incoming messages: This is implemented by an additional +Verifying 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 @@ -38021,7 +38169,7 @@ senders). .section "Signing outgoing messages" "SECDKIMSIGN" .cindex "DKIM" "signing" -Signing is implemented by setting private options on the SMTP transport. +Signing is enabled by setting private options on the SMTP transport. These options take (expandable) strings as arguments. .option dkim_domain smtp string&!! unset @@ -38078,7 +38226,7 @@ used. .section "Verifying DKIM signatures in incoming mail" "SECID514" .cindex "DKIM" "verification" -Verification of DKIM signatures in incoming email is implemented via the +Verification of DKIM signatures in SMTP incoming email is implemented via the &%acl_smtp_dkim%& ACL. By default, this ACL is called once for each syntactically(!) correct signature in the incoming message. A missing ACL definition defaults to accept. @@ -38131,6 +38279,7 @@ available (from most to least important): The signer that is being evaluated in this ACL run. This can be a domain or an identity. This is one of the list items from the expanded main option &%dkim_verify_signers%& (see above). + .vitem &%$dkim_verify_status%& A string describing the general status of the signature. One of .ilist @@ -38145,6 +38294,7 @@ available in &%$dkim_verify_reason%&. .next &%pass%&: The signature passed verification. It is valid. .endlist + .vitem &%$dkim_verify_reason%& A string giving a little bit more detail when &%$dkim_verify_status%& is either "fail" or "invalid". One of @@ -38164,51 +38314,73 @@ could not be verified. This may mean that headers were modified, re-written or otherwise changed in a way which is incompatible with DKIM verification. It may of course also mean that the signature is forged. .endlist + .vitem &%$dkim_domain%& The signing domain. IMPORTANT: This variable is only populated if there is an actual signature in the message for the current domain or identity (as reflected by &%$dkim_cur_signer%&). + .vitem &%$dkim_identity%& The signing identity, if present. IMPORTANT: This variable is only populated if there is an actual signature in the message for the current domain or identity (as reflected by &%$dkim_cur_signer%&). + .vitem &%$dkim_selector%& The key record selector string. + .vitem &%$dkim_algo%& The algorithm used. One of 'rsa-sha1' or 'rsa-sha256'. + .vitem &%$dkim_canon_body%& The body canonicalization method. One of 'relaxed' or 'simple'. + .vitem &%dkim_canon_headers%& The header canonicalization method. One of 'relaxed' or 'simple'. + .vitem &%$dkim_copiedheaders%& A transcript of headers and their values which are included in the signature (copied from the 'z=' tag of the signature). +.new +Note that RFC6376 requires that verification fail if the From: header is +not included in the signature. Exim does not enforce this; sites wishing +strict enforcement should code the check explicitly. +.wen + .vitem &%$dkim_bodylength%& The number of signed body bytes. If zero ("0"), the body is unsigned. If no limit was set by the signer, "9999999999999" is returned. This makes sure that this variable always expands to an integer value. + .vitem &%$dkim_created%& UNIX timestamp reflecting the date and time when the signature was created. When this was not specified by the signer, "0" is returned. + .vitem &%$dkim_expires%& UNIX timestamp reflecting the date and time when the signer wants the signature to be treated as "expired". When this was not specified by the signer, "9999999999999" is returned. This makes it possible to do useful integer size comparisons against this value. + .vitem &%$dkim_headernames%& A colon-separated list of names of headers included in the signature. + .vitem &%$dkim_key_testing%& "1" if the key record has the "testing" flag set, "0" if not. + .vitem &%$dkim_key_nosubdomains%& "1" if the key record forbids subdomaining, "0" otherwise. + .vitem &%$dkim_key_srvtype%& Service type (tag s=) from the key record. Defaults to "*" if not specified in the key record. + .vitem &%$dkim_key_granularity%& Key granularity (tag g=) from the key record. Defaults to "*" if not specified in the key record. + .vitem &%$dkim_key_notes%& Notes from the key record (tag n=). + .vitem &%$dkim_key_length%& Number of bits in the key. .endlist @@ -38223,13 +38395,18 @@ for a match against the domain or identity that the ACL is currently verifying verb to a group of domains or identities. For example: .code -# Warn when Mail purportedly from GMail has no signature at all -warn log_message = GMail sender without DKIM signature +# Warn when Mail purportedly from GMail has no gmail signature +warn log_message = GMail sender without gmail.com DKIM signature sender_domains = gmail.com dkim_signers = gmail.com dkim_status = none .endd +.new +Note that the above does not check for a total lack of DKIM signing; +for that check for empty &$h_DKIM-Signature:$& in the data ACL. +.wen + .vitem &%dkim_status%& ACL condition that checks a colon-separated list of possible DKIM verification results against the actual result of verification. This is typically used @@ -38440,7 +38617,7 @@ form of the name. Log lines and Received-by: header lines will acquire a "utf8" prefix on the protocol element, eg. utf8esmtp. -The following expansion operator can be used: +The following expansion operators can be used: .code ${utf8_domain_to_alabel:str} ${utf8_domain_from_alabel:str}