X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/c2fe5cfd1c4ae7b5fcacca7849f4dff5c791fa97..532be4499552dfab0e3173f7d3e85c81e1496147:/doc/doc-docbook/spec.xfpt?ds=sidebyside diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 24d615f14..dd8db2367 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 1.41 2008/04/13 11:45:58 tom Exp $ +. $Cambridge: exim/doc/doc-docbook/spec.xfpt,v 1.83 2010/06/07 07:09:10 pdp Exp $ . . ///////////////////////////////////////////////////////////////////////////// . This is the primary source of the Exim Manual. It is an xfpt document that is @@ -47,8 +47,8 @@ . the element must also be updated for each new edition. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.69" -.set version "4.70" +.set previousversion "4.71" +.set version "4.72" .set ACL "access control lists (ACLs)" .set I "    " @@ -172,17 +172,15 @@ Specification of the Exim Mail Transfer Agent The Exim MTA -23 August 2007 -PhilipHazel -PH -University of Cambridge Computing Service -
New Museums Site, Pembroke Street, Cambridge CB2 3QH, England
+29 May 2010 +EximMaintainers +EM - 4.68 - 23 August 2007 - PH + 4.72 + 29 May 2010 + EM -2007University of Cambridge +2009University of Cambridge .literal off @@ -2606,6 +2604,11 @@ This option causes Exim to output a few sentences stating what it is. The same output is generated if the Exim binary is called with no options and no arguments. +.vitem &%--version%& +.oindex "&%--version%&" +This option is an alias for &%-bV%& and causes version information to be +displayed. + .vitem &%-B%&<&'type'&> .oindex "&%-B%&" .cindex "8-bit characters" @@ -2975,6 +2978,7 @@ local part) and outputs what it finds. .cindex "options" "router &-- extracting" .cindex "options" "transport &-- extracting" +.cindex "options" "authenticator &-- extracting" If one of the words &%router%&, &%transport%&, or &%authenticator%& is given, followed by the name of an appropriate driver instance, the option settings for that driver are output. For example: @@ -2988,6 +2992,11 @@ using one of the words &%router_list%&, &%transport_list%&, or settings can be obtained by using &%routers%&, &%transports%&, or &%authenticators%&. +.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. .vitem &%-bp%& .oindex "&%-bp%&" @@ -3165,6 +3174,17 @@ above concerning senders and qualification do not apply. In this situation, Exim behaves in exactly the same way as it does when receiving a message via the listening daemon. +.vitem &%-bmalware%&&~<&'filename'&> +.oindex "&%-bmalware%&" +.cindex "testing", "malware" +.cindex "malware scan test" +This debugging option causes Exim to scan the given file, +using the malware scanning framework. The option of av_scanner influences +this option, so if av_scanner's value is dependent upon an expansion then +the expansion should have defaults which apply to this invocation. Exim will +have changed working directory before resolving the filename, so using fully +qualified pathnames is advisable. This option requires admin privileges. + .vitem &%-bt%& .oindex "&%-bt%&" .cindex "testing" "addresses" @@ -3741,7 +3761,7 @@ written to the standard output. This option can be used only by an admin user. .vitem &%-Mvc%&&~<&'message&~id'&> .oindex "&%-Mvc%&" .cindex "message" "listing in RFC 2822 format" -.cindex "listing" "message in RFC 2922 format" +.cindex "listing" "message in RFC 2822 format" This option causes a copy of the complete message (header lines plus body) to be written to the standard output in RFC 2822 format. This option can be used only by an admin user. @@ -4718,7 +4738,7 @@ up in a MySQL database. It helps to keep the file less cluttered if long strings such as SQL statements are defined separately as macros, for example: .code ALIAS_QUERY = select mailbox from user where \ - login=${quote_mysql:$local_part}; + login='${quote_mysql:$local_part}'; .endd This can then be used in a &(redirect)& router setting like this: .code @@ -5885,6 +5905,10 @@ 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 &<>&. +Beware that the sequence of the parameters to PLAIN and LOGIN differ; the +usercode and password are in different positions. &<>& +covers both. + .ecindex IIDconfiwal @@ -6128,7 +6152,7 @@ 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 @@ -6620,6 +6644,20 @@ ${lookup dnsdb{>: a=host1.example}} It is permitted to specify a space as the separator character. Further white space is ignored. +.new +.cindex "TXT record" "in &(dnsdb)& lookup" +For TXT records with multiple items of data, only the first item is returned, +unless a separator for them is specified using a comma after the separator +character followed immediately by the TXT record item separator. To concatenate +items without a separator, use a semicolon instead. +.code +${lookup dnsdb{>\n,: txt=a.b.example}} +${lookup dnsdb{>\n; txt=a.b.example}} +.endd +It is permitted to specify a space as the separator character. Further +white space is ignored. +.wen + .section "Pseudo dnsdb record types" "SECID66" .cindex "MX record" "in &(dnsdb)& lookup" By default, both the preference value and the host name are returned for @@ -7172,13 +7210,13 @@ mysql_servers = slave1/db/name/pw:\ .endd In an updating lookup, you could then write: .code -${lookup mysql{servers=master; UPDATE ...} +${lookup mysql{servers=master; UPDATE ...} } .endd That query would then be sent only to the master server. If, on the other hand, the master is not to be used for reading, and so is not present in the global option, you can still update it by a query of this form: .code -${lookup pgsql{servers=master/db/name/pw; UPDATE ...} +${lookup pgsql{servers=master/db/name/pw; UPDATE ...} } .endd @@ -9571,6 +9609,32 @@ For single-key lookup types, no quoting is ever necessary and this operator yields an unchanged string. +.vitem &*${randint:*&<&'n'&>&*}*& +.cindex "random number" +This operator returns a somewhat random number which is less than the +supplied number and is at least 0. The quality of this randomness depends +on how Exim was built; the values are not suitable for keying material. +If Exim is linked against OpenSSL then RAND_pseudo_bytes() is used. +Otherwise, the implementation may be arc4random(), random() seeded by +srandomdev() or srandom(), or a custom implementation even weaker than +random(). + + +.vitem &*${reverse_ip:*&<&'ipaddr'&>&*}*& +.cindex "expansion" "IP address" +This operator reverses an IP address; for IPv4 addresses, the result is in +dotted-quad decimal form, while for IPv6 addreses the result is in +dotted-nibble hexadecimal form. In both cases, this is the "natural" form +for DNS. For example, +.code +${reverse_ip:192.0.2.4} and ${reverse_ip:2001:0db8:c42:9:1:abcd:192.0.2.3} +.endd +returns +.code +4.2.0.192 and 3.0.2.0.0.0.0.c.d.c.b.a.1.0.0.0.9.0.0.0.2.4.c.0.8.b.d.0.1.0.0.2 +.endd + + .vitem &*${rfc2047:*&<&'string'&>&*}*& .cindex "expansion" "RFC 2047" .cindex "RFC 2047" "expansion operator" @@ -9732,6 +9796,22 @@ 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. +.vitem &*bool&~{*&<&'string'&>&*}*& +.cindex "expansion" "boolean parsing" +.cindex "&%bool%& expansion condition" +This condition turns a string holding a true or false representation into +a boolean state. It parses &"true"&, &"false"&, &"yes"& and &"no"& +(case-insensitively); also positive integer numbers map to true if non-zero, +false if zero. Leading whitespace is ignored. +All other string values will result in expansion failure. + +When combined with ACL variables, this expansion condition will let you +make decisions in one place and act on those decisions in another place. +For example: +.code +${if bool{$acl_m_privileged_sender} ... +.endd + .vitem &*crypteq&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "expansion" "encrypted comparison" .cindex "encrypted strings, comparing" @@ -10183,6 +10263,10 @@ configuration, you might have this: .code server_condition = ${if pwcheck{$auth1:$auth2}} .endd +Again, for a PLAIN authenticator configuration, this would be: +.code +server_condition = ${if pwcheck{$auth2:$auth3}} +.endd .vitem &*queue_running*& .cindex "queue runner" "detecting when delivering from" .cindex "expansion" "queue runner test" @@ -10970,7 +11054,7 @@ precise size of the file that has been written. See also &$message_body_size$&, &$body_linecount$&, and &$body_zerocount$&. .cindex "RCPT" "value of &$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. @@ -12284,6 +12368,7 @@ listed in more than one group. .row &%acl_smtp_auth%& "ACL for AUTH" .row &%acl_smtp_connect%& "ACL for connection" .row &%acl_smtp_data%& "ACL for DATA" +.row &%acl_smtp_dkim%& "ACL for DKIM verification" .row &%acl_smtp_etrn%& "ACL for ETRN" .row &%acl_smtp_expn%& "ACL for EXPN" .row &%acl_smtp_helo%& "ACL for EHLO or HELO" @@ -12338,6 +12423,8 @@ 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 &%openssl_options%& "adjust OpenSSL compatibility options" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" .row &%tls_certificate%& "location of server certificate" .row &%tls_crl%& "certificate revocation list" @@ -12743,7 +12830,7 @@ It specifies which anti-virus scanner to use. The default value is: .code sophie:/var/run/sophie .endd -If the value of &%av_scanner%& starts with dollar character, it is expanded +If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. See section &<>& for further details. @@ -13337,6 +13424,10 @@ server. For details, see section &<>&. This option controls the protocols when GnuTLS is used in an Exim server. For details, see section &<>&. +.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. .option headers_charset main string "see below" This option sets a default character set for translating from encoded MIME @@ -13408,10 +13499,10 @@ 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. @@ -13433,7 +13524,7 @@ 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" @@ -13489,8 +13580,8 @@ 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`& @@ -13893,6 +13984,14 @@ an oversized message is logged in both the main and the reject logs. See also the generic transport option &%message_size_limit%&, which limits the size of message that an individual transport can process. +If you use a virus-scanner and set this option to to a value larger than the +maximum size that your virus-scanner is configured to support, you may get +failures triggered by large mails. The right size to configure for the +virus-scanner depends upon what data is passed and the options in use but it's +probably safest to just set it to a little larger than this value. Eg, with a +default Exim message size of 50M and a default ClamAV StreamMaxLength of 10M, +some problems may result. + .option move_frozen_messages main boolean false .cindex "frozen messages" "moving" @@ -13945,6 +14044,36 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. +.option openssl_options main "string list" +dont_insert_empty_fragments +.cindex "OpenSSL "compatibility options" +This option allows an administrator to adjust the SSL options applied +by OpenSSL to connections. It is given as a space-separated list of items, +each one to be +added or -subtracted from the current value. The default +value is one option which happens to have been set historically. You can +remove all options with: +.code +openssl_options = -all +.endd +This option is only available if Exim is built against OpenSSL. The values +available for this option vary according to the age of your OpenSSL install. +The &"all"& value controls a subset of flags which are available, typically +the bug workaround options. The &'SSL_CTX_set_options'& man page will +list the values known on your system and Exim should support all the +&"bug workaround"& options and many of the &"modifying"& options. The Exim +names lose the leading &"SSL_OP_"& and are lower-cased. + +Note that adjusting the options can have severe impact upon the security of +SSL as used by Exim. It is possible to disable safety checks and shoot +yourself in the foot in various unpleasant ways. This option should not be +adjusted lightly. An unrecognised item will be detected at by invoking Exim +with the &%-bV%& flag. + +An example: +.code +openssl_options = -all +microsoft_big_sslv3_buffer +.endd + + .option oracle_servers main "string list" unset .cindex "Oracle" "server list" This option provides a list of Oracle servers and associated connection data, @@ -15540,6 +15669,12 @@ router is skipped, and the address is offered to the next one. If the result is any other value, the router is run (as this is the last precondition to be evaluated, all the other preconditions must be true). +This option is unique in that multiple &%condition%& options may be present. +In this case, the previous statement does not quite apply: the result of each +&%condition%& option must be a string recognised by the &%bool%& expansion +operator, or failure will be forced. The effect is to "and" the conditions +together, as each must pass. + 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: @@ -15550,6 +15685,11 @@ Because of the default behaviour of the string expansion, this is equivalent to .code condition = ${if >{$message_age}{600}{true}{}} .endd +A multiple condition example: +.code +condition = ${if >{$message_age}{600}} +condition = ${if !eq{${lc:$local_part}}{postmaster}} +.endd If the expansion fails (other than forced failure) delivery is deferred. Some of the other precondition options are common special cases that could in fact be specified using &%condition%&. @@ -17810,10 +17950,10 @@ 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: +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: .code X.Employee: :fail: Gone away, no forwarding address .endd @@ -18958,11 +19098,9 @@ filter itself, and the original process that reads the result and delivers it are all run in parallel, like a shell pipeline. The filter can perform any transformations it likes, but of course should take -care not to break RFC 2822 syntax. A demonstration Perl script is provided in -&_util/transport-filter.pl_&; this makes a few arbitrary modifications just to -show the possibilities. 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. +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. .cindex "content scanning" "per user" A transport filter can be used to provide content-scanning on a per-user basis @@ -20988,6 +21126,17 @@ sought in the PATH directories, in the usual way. &*Warning*&: This does not apply to a command specified as a transport filter. +.option permit_coredump pipe boolean false +Normally Exim inhibits core-dumps during delivery. If you have a need to get +a core-dump of a pipe command, enable this command. This enables core-dumps +during delivery and affects both the Exim binary and the pipe command run. +It is recommended that this option remain off unless and until you have a need +for it and that this only be enabled when needed, as the risk of excessive +resource consumption can be quite high. Note also that Exim is typically +installed as a setuid binary and most operating systems will inhibit coredumps +of these by default, so further OS-specific action may be required. + + .option pipe_as_creator pipe boolean false .cindex "uid (user id)" "local delivery" If the generic &%user%& option is not set and this option is true, the delivery @@ -21128,6 +21277,7 @@ procmail_pipe: envelope_to_add check_string = "From " escape_string = ">From " + umask = 077 user = $local_part group = mail @@ -21427,18 +21577,23 @@ being used, names are looked up using &[gethostbyname()]& instead of using the DNS. Of course, that function may in fact use the DNS, but it may also consult other sources of information such as &_/etc/hosts_&. -.option gnutls_require_kx main string unset +.option gnutls_require_kx smtp string unset This option controls the key exchange mechanisms when GnuTLS is used in an Exim client. For details, see section &<>&. -.option gnutls_require_mac main string unset +.option gnutls_require_mac smtp string unset This option controls the MAC algorithms when GnuTLS is used in an Exim client. For details, see section &<>&. -.option gnutls_require_protocols main string unset +.option gnutls_require_protocols smtp string unset This option controls the protocols when GnuTLS is used in an Exim client. For details, see section &<>&. +.option gnutls_compat_mode smtp boolean unset +This option controls whether GnuTLS is used in compatibility mode in an Exim +server. This reduces security slightly, but improves interworking with older +implementations of TLS. + .option helo_data smtp string&!! "see below" .cindex "HELO" "argument, setting" .cindex "EHLO" "argument, setting" @@ -23540,7 +23695,6 @@ the password conform to the Exim syntax. At the LDAP level, the password is an uninterpreted string. - .section "Support for different kinds of authentication" "SECID174" A number of string expansion features are provided for the purpose of interfacing to different ways of user authentication. These include checking @@ -23799,7 +23953,7 @@ sasl_cram_md5: sasl_plain: driver = cyrus_sasl public_name = PLAIN - server_set_id = $auth1 + server_set_id = $auth2 .endd Cyrus SASL does implement the LOGIN authentication method, even though it is not a standard method. It is disabled by default in the source distribution, @@ -23832,7 +23986,7 @@ dovecot_plain: driver = dovecot public_name = PLAIN server_socket = /var/run/dovecot/auth-client - server_set_id = $auth1 + server_set_id = $auth2 dovecot_ntlm: driver = dovecot @@ -24415,13 +24569,10 @@ unencrypted. The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)& transport provide the client with a certificate, which is passed to the server if it requests it. If the server is Exim, it will request a certificate only if -&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. &*Note*&: -These options must be set in the &(smtp)& transport for Exim to use TLS when it -is operating as a client. Exim does not assume that a server certificate (set -by the global options of the same name) should also be used when operating as a -client. +&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. -If &%tls_verify_certificates%& is set, it must name a file or, +If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it +must name a file or, for OpenSSL only (not GnuTLS), a directory, that contains a collection of expected server certificates. The client verifies the server's certificate against this collection, taking into account any revoked certificates that are @@ -24433,6 +24584,12 @@ list of permitted cipher suites. If either of these checks fails, delivery to the current host is abandoned, and the &(smtp)& transport tries to deliver to alternative hosts, if any. + &*Note*&: +These options must be set in the &(smtp)& transport for Exim to use TLS when it +is operating as a client. Exim does not assume that a server certificate (set +by the global options of the same name) should also be used when operating as a +client. + .vindex "&$host$&" .vindex "&$host_address$&" All the TLS options in the &(smtp)& transport are expanded before use, with @@ -24767,9 +24924,9 @@ client are given temporary error responses until QUIT is received or the connection is closed. In these special cases, the QUIT ACL does not run. - .section "The not-QUIT ACL" "SECTNOTQUITACL" -The not-QUIT ACL, specified by &%smtp_notquit_acl%&, is run in most cases when +.vindex &$acl_smtp_notquit$& +The not-QUIT ACL, specified by &%acl_smtp_notquit%&, is run in most cases when 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 @@ -25081,7 +25238,7 @@ the sending entity receives a &"success"& response. However, &%discard%& causes recipients to be discarded. If it is used in an ACL for RCPT, just the one recipient is discarded; if used for MAIL, DATA or in the non-SMTP ACL, all the message's recipients are discarded. Recipients that are discarded before DATA -do not appear in the log line when the &%log_recipients%& log selector is set. +do not appear in the log line when the &%received_recipients%& log selector is set. If the &%log_message%& modifier is set when &%discard%& operates, its contents are added to the line that is automatically written to the log. @@ -25471,7 +25628,8 @@ ACL fragment writes no logging information when access is denied: &` log_reject_target =`& .endd This modifier can be used in SMTP and non-SMTP ACLs. It applies to both -permanent and temporary rejections. +permanent and temporary rejections. Its effect lasts for the rest of the +current ACL. .vitem &*logwrite*&&~=&~<&'text'&> @@ -25631,6 +25789,23 @@ warn control = caseful_local_part Notice that we put back the lower cased version afterwards, assuming that is what is wanted for subsequent tests. +.vitem &*control&~=&~debug/*&<&'options'&> +.cindex "&ACL;" "enabling debug logging" +.cindex "debugging" "enabling from an ACL" +This control turns on debug logging, almost as though Exim had been invoked +with &`-d`&, with the output going to a new logfile, by default called +&'debuglog'&. The filename can be adjusted with the &'tag'& option, which +may access any variables already defined. The logging may be adjusted with +the &'opts'& option, which takes the same values as the &`-d`& command-line +option. Some examples (which depend on variables that don't exist in all +contexts): +.code + control = debug + control = debug/tag=.$sender_host_address + control = debug/opts=+expand+acl + control = debug/tag=.$message_exim_id/opts=+expand +.endd + .vitem &*control&~=&~enforce_sync*& &&& &*control&~=&~no_enforce_sync*& .cindex "SMTP" "synchronization checking" @@ -25766,7 +25941,7 @@ 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). @@ -25779,7 +25954,7 @@ 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 @@ -25808,12 +25983,12 @@ 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 @@ -26959,7 +27134,7 @@ 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 $sender_rate_limit) .endd @@ -27554,19 +27729,8 @@ the third string (in this case &"1"&), whether or not the cryptographic and timeout checks succeed. The &$prvscheck_result$& variable contains the result of the checks (empty for failure, &"1"& for success). -There are two more issues you must consider when implementing prvs-signing. -Firstly, you need to ensure that prvs-signed addresses are not blocked by your -ACLs. A prvs-signed address contains a slash character, but the default Exim -configuration contains this statement in the RCPT ACL: -.code -deny message = Restricted characters in address - domains = +local_domains - local_parts = ^[.] : ^.*[@%!/|] -.endd -This is a conservative rule that blocks local parts that contain slashes. You -should remove the slash in the last line. - -Secondly, you have to ensure that the routers accept prvs-signed addresses and +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: .code @@ -27764,7 +27928,7 @@ If you do not set &%av_scanner%&, it defaults to .code av_scanner = sophie:/var/run/sophie .endd -If the value of &%av_scanner%& starts with dollar character, it is expanded +If the value of &%av_scanner%& starts with a dollar character, it is expanded before use. The following scanner types are supported in this release: .vlist @@ -27788,8 +27952,16 @@ required: either the path and name of a UNIX socket file, or a hostname or IP number, and a port, separated by space, as in the second of these examples: .code av_scanner = clamd:/opt/clamd/socket -av_scanner = clamd:192.168.2.100 1234 -.endd +av_scanner = clamd:192.0.2.3 1234 +av_scanner = clamd:192.0.2.3 1234:local +.endd +If the value of av_scanner points to a UNIX socket file or contains the local +keyword, then the ClamAV interface will pass a filename containing the data +to be scanned, which will should normally result in less I/O happening and be +more efficient. Normally in the TCP case, the data is streamed to ClamAV as +Exim does not assume that there is a common filesystem with the remote host. +There is an option WITH_OLD_CLAMAV_STREAM in &_src/EDITME_& available, should +you be running a version of ClamAV prior to 0.95. If the option is unset, the default is &_/tmp/clamd_&. Thanks to David Saez for contributing the code for this scanner. @@ -27929,6 +28101,9 @@ If your virus scanner cannot unpack MIME and TNEF containers itself, you should use the &%demime%& condition (see section &<>&) before the &%malware%& condition. +Beware the interaction of Exim's &%message_size_limit%& with any size limits +imposed by your anti-virus scanner. + Here is a very simple scanning example: .code deny message = This message contains malware ($malware_name) @@ -28051,9 +28226,8 @@ it always return &"true"& by appending &`:true`& to the username. .cindex "spam scanning" "returned variables" When the &%spam%& condition is run, it sets up a number of expansion -variables. With the exception of &$spam_score_int$&, these are usable only -within ACLs; their values are not retained with the message and so cannot be -used at delivery time. +variables. These variables are saved with the received message, thus they are +available for use at delivery time. .vlist .vitem &$spam_score$& @@ -28064,11 +28238,8 @@ for inclusion in log or reject messages. The spam score of the message, multiplied by ten, as an integer value. For example &"34"& or &"305"&. It may appear to disagree with &$spam_score$& because &$spam_score$& is rounded and &$spam_score_int$& is truncated. -The integer value is useful for numeric comparisons in -conditions. This variable is special; its value is saved with the message, and -written to Exim's spool file. This means that it can be used during the whole -life of the message on your Exim system, in particular, in routers or -transports during the later delivery phase. +The integer value is useful for numeric comparisons in conditions. + .vitem &$spam_bar$& A string consisting of a number of &"+"& or &"-"& characters, representing the @@ -30268,8 +30439,8 @@ If a message contains a number of different addresses, all those with the same characteristics (for example, the same envelope sender) that resolve to the same set of hosts, in the same order, are sent in a single SMTP transaction, even if they are for different domains, unless there are more than the setting -of the &%max_rcpts%& option in the &(smtp)& transport allows, in which case -they are split into groups containing no more than &%max_rcpts%& addresses +of the &%max_rcpt%&s option in the &(smtp)& transport allows, in which case +they are split into groups containing no more than &%max_rcpt%&s addresses each. If &%remote_max_parallel%& is greater than one, such groups may be sent in parallel sessions. The order of hosts with identical MX values is not significant when checking whether addresses can be batched in this way. @@ -34278,13 +34449,270 @@ unqualified domain &'foundation'&. .ecindex IIDforspo2 .ecindex IIDforspo3 +. //////////////////////////////////////////////////////////////////////////// +. //////////////////////////////////////////////////////////////////////////// + +.chapter "Support for DKIM (DomainKeys Identified Mail) - RFC4871" "CHID12" &&& + "DKIM Support" +.cindex "DKIM" + +Since version 4.70, DKIM support is compiled into Exim by default. It can be +disabled by setting DISABLE_DKIM=yes in Local/Makefile. + +Exim's DKIM implementation allows to +.olist +Sign outgoing messages: This function is implemented in the SMTP transport. +It can co-exist with all other Exim features, including transport filters. +.next +Verify signatures in incoming messages: This is implemented by an additional +ACL (acl_smtp_dkim), which can be called several times per message, with +different signature contexts. +.endlist + +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. + +Please note that verification of DKIM signatures in incoming mail is turned +on by default for logging purposes. For each signature in incoming email, +exim will log a line displaying the most important signature details, and the +signature status. Here is an example: +.code +2009-09-09 10:22:28 1MlIRf-0003LU-U3 DKIM: d=facebookmail.com s=q1-2009b c=relaxed/relaxed a=rsa-sha1 i=@facebookmail.com t=1252484542 [verification succeeded] +.endd +You might want to turn off DKIM verification processing entirely for internal +or relay mail sources. To do that, set the &%dkim_disable_verify%& ACL +control modifier. This should typically be done in the RCPT ACL, at points +where you accept mail from relay sources (internal hosts or authenticated +senders). + + +.section "Signing outgoing messages" "SECID513" +.cindex "DKIM" "signing" + +Signing is implemented by setting private options on the SMTP transport. +These options take (expandable) strings as arguments. + +.option dkim_domain smtp string&!! unset +MANDATORY: +The domain you want to sign with. The result of this expanded +option is put into the &%$dkim_domain%& expansion variable. + +.option dkim_selector smtp string&!! unset +MANDATORY: +This sets the key selector string. You can use the &%$dkim_domain%& expansion +variable to look up a matching selector. The result is put in the expansion +variable &%$dkim_selector%& which should be used in the &%dkim_private_key%& +option along with &%$dkim_domain%&. +.option dkim_private_key smtp string&!! unset +MANDATORY: +This sets the private key to use. You can use the &%$dkim_domain%& and +&%$dkim_selector%& expansion variables to determine the private key to use. +The result can either +.ilist +be a valid RSA private key in ASCII armor, including line breaks. +.next +start with a slash, in which case it is treated as a file that contains +the private key. +.next +be "0", "false" or the empty string, in which case the message will not +be signed. This case will not result in an error, even if &%dkim_strict%& +is set. +.endlist +.option dkim_canon smtp string&!! unset +OPTIONAL: +This option sets the canonicalization method used when signing a message. +The DKIM RFC currently supports two methods: "simple" and "relaxed". +The option defaults to "relaxed" when unset. Note: the current implementation +only supports using the same canonicalization method for both headers and body. + +.option dkim_strict smtp string&!! unset +OPTIONAL: +This option defines how Exim behaves when signing a message that +should be signed fails for some reason. When the expansion evaluates to +either "1" or "true", Exim will defer. Otherwise Exim will send the message +unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion +variables here. + +.option dkim_sign_headers smtp string&!! unset +OPTIONAL: +When set, this option must expand to (or be specified as) a colon-separated +list of header names. Headers with these names will be included in the message +signature. When unspecified, the header names recommended in RFC4871 will be +used. + + +.section "Verifying DKIM signatures in incoming mail" "SECID514" +.cindex "DKIM" "verification" + +Verification of DKIM signatures in 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. + +To evaluate the signature in the ACL a large number of expansion variables +containing the signature status and its details are set up during the +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 +&%$dkim_signers%& exist. + +The global option &%dkim_verify_signers%& can be set to a colon-separated +list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is +called. It is expanded when the message has been received. At this point, +the expansion variable &%$dkim_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 = $dkim_signers +.endd +This leads to the default behaviour of calling &%acl_smtp_dkim%& for each +DKIM signature in the message. Current DKIM verifiers may want to explicitly +call the ACL for known domains or identities. This would be achieved as follows: +.code +dkim_verify_signers = paypal.com:ebay.com:$dkim_signers +.endd +This would result in &%acl_smtp_dkim%& always being called for "paypal.com" +and "ebay.com", plus all domains and identities that have signatures in the message. +You can also be more creative in constructing your policy. For example: +.code +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 &%$dkim_cur_signer%& +The signer that is being evaluated in this ACL run. This can be a domain or +an identity. This is one of the list items from the expanded main option +&%dkim_verify_signers%& (see above). +.vitem &%$dkim_verify_status%& +A string describing the general status of the signature. One of +.ilist +&%none%&: There is no signature in the message for the current domain or +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%&. +.next +&%fail%&: Verification of the signature failed. More detail is +available in &%$dkim_verify_reason%&. +.next +&%pass%&: The signature passed verification. It is valid. +.endlist +.vitem &%$dkim_verify_reason%& +A string giving a litte bit more detail when &%$dkim_verify_status%& is either +"fail" or "invalid". One of +.ilist +&%pubkey_unavailable%& (when &%$dkim_verify_status%&="invalid"): The public +key for the domain could not be retrieved. This may be a temporary problem. +.next +&%pubkey_syntax%& (when &%$dkim_verify_status%&="invalid"): The public key +record for the domain is syntactically invalid. +.next +&%bodyhash_mismatch%& (when &%$dkim_verify_status%&="fail"): The calculated +body hash does not match the one specified in the signature header. This +means that the message body was modified in transit. +.next +&%signature_incorrect%& (when &%$dkim_verify_status%&="fail"): The signature +could not be verified. This may mean that headers were modified, +re-written or otherwise changed in a way which is incompatible with +DKIM verification. It may of course also mean that the signature is forged. +.endlist +.vitem &%$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 &%$dkim_copiedheaders%& +A transcript of headers and their values which are included in the signature +(copied from the 'z=' tag of the signature). +.vitem &%$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 &%$dkim_key_nosubdomaining%& +"1" if the key record forbids subdomaining, "0" otherwise. +.vitem &%$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=). +.endlist + +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 +(reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL +verb to a group of domains or identities. For example: + +.code +# Warn when message apparently from GMail has no signature at all +warn log_message = GMail sender without DKIM signature + sender_domains = gmail.com + dkim_signers = gmail.com + dkim_status = none +.endd + +.vitem &%dkim_status%& +ACL condition that checks a colon-separated list of possible DKIM verification +results agains the actual result of verification. This is typically used +to restrict an ACL verb to a list of verification outcomes, like: + +.code +deny message = Message from Paypal with invalid or missing signature + sender_domains = paypal.com:paypal.de + dkim_signers = paypal.com:paypal.de + dkim_status = none:invalid:fail +.endd + +The possible status keywords are: 'none','invalid','fail' and 'pass'. Please +see the documentation of the &%$dkim_verify_status%& expansion variable above +for more information of what they mean. +.endlist . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// -.chapter "Adding new drivers or lookup types" "CHID12" &&& +.chapter "Adding new drivers or lookup types" "CHID13" &&& "Adding drivers or lookups" .cindex "adding drivers" .cindex "new drivers, adding"