X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/599fc3c68f5e942c1d662012053ecfc6ea26bd49..210135138f6150c46e8abc54f6ccf82a860d510f:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index cf227ccf6..d0c3e7846 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -45,7 +45,7 @@ . Update the Copyright year (only) when changing content. . ///////////////////////////////////////////////////////////////////////////// -.set previousversion "4.93" +.set previousversion "4.94" .include ./local_params .set ACL "access control lists (ACLs)" @@ -1409,11 +1409,9 @@ the set of local parts that it defines. If &%local_part_prefix%& or &%local_part_suffix%& is in use, the prefix or suffix is removed from the local part before this check. If you want to do precondition tests on local parts that include affixes, you can do so by using a &%condition%& option (see below) -.new that uses the variables &$local_part$&, &$local_part_prefix$&, &$local_part_prefix_v$&, &$local_part_suffix$& and &$local_part_suffix_v$& as necessary. -.wen .next .vindex "&$local_user_uid$&" .vindex "&$local_user_gid$&" @@ -3871,13 +3869,11 @@ This option is not intended for use by external callers. It is used internally by Exim in conjunction with the &%-MC%& option. It signifies that the remote host supports the ESMTP &_DSN_& extension. -.new .vitem &%-MCd%& .oindex "&%-MCd%&" This option is not intended for use by external callers. It is used internally by Exim in conjunction with the &%-d%& option to pass on an information string on the purpose of the process. -.wen .vitem &%-MCG%&&~<&'queue&~name'&> .oindex "&%-MCG%&" @@ -3906,6 +3902,13 @@ together with the file descriptor number of an open pipe. Closure of the pipe signals the final completion of the sequence of processes that are passing messages through the same SMTP connection. +.new +.vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&> +.oindex "&%-MCq%&" +This option is not intended for use by external callers. It is used internally +by Exim to implement quota checking for local users. +.wen + .vitem &%-MCS%& .oindex "&%-MCS%&" This option is not intended for use by external callers. It is used internally @@ -3919,6 +3922,18 @@ This option is not intended for use by external callers. It is used internally by Exim in conjunction with the &%-MC%& option, and passes on the fact that the host to which Exim is connected supports TLS encryption. +.new +.vitem &%-MCr%&&~<&'SNI'&> &&& + &%-MCs%&&~<&'SNI'&> +.oindex "&%-MCs%&" +.oindex "&%-MCr%&" +These options are not intended for use by external callers. It is used internally +by Exim in conjunction with the &%-MCt%& option, and passes on the fact that +a TLS Server Name Indication was sent as part of the channel establishment. +The argument gives the SNI string. +The "r" variant indicates a DANE-verified connection. +.wen + .vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&> .oindex "&%-MCt%&" This option is not intended for use by external callers. It is used internally @@ -4397,7 +4412,6 @@ written. When &%-oX%& is used with &%-bd%&, or when &%-q%& with a time is used without &%-bd%&, this is the only way of causing Exim to write a pid file, because in those cases, the normal pid file is not used. -.new .vitem &%-oPX%& .oindex "&%-oPX%&" .cindex "pid (process id)" "of daemon" @@ -4406,7 +4420,6 @@ This option is not intended for general use. The daemon uses it when terminating due to a SIGTEM, possibly in combination with &%-oP%&&~<&'path'&>. It causes the pid file to be removed. -.wen .vitem &%-or%&&~<&'time'&> .oindex "&%-or%&" @@ -4440,6 +4453,27 @@ of the syntax, and how it interacts with configuration file options, are given in chapter &<>&. When &%-oX%& is used to start a daemon, no pid file is written unless &%-oP%& is also present to specify a pid filename. +.new +.vitem &%-oY%& +.oindex &%-oY%& +.cindex "daemon notifier socket" +This option controls the creation of an inter-process communications endpoint +by the Exim daemon. +It is only relevant when the &%-bd%& (start listening daemon) option is also +given. +Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%& +option is also present. +If this option is given then the socket will not be created. This could be +required if the system is running multiple daemons. + +The socket is currently used for +.ilist +fast ramp-up of queue runner processes +.next +obtaining a current queue size +.endlist +.wen + .vitem &%-pd%& .oindex "&%-pd%&" .cindex "Perl" "starting the interpreter" @@ -4518,14 +4552,17 @@ appear in the correct order. Each flag is described in a separate item below. .cindex "queue" "routing" .cindex "routing" "whole queue before delivery" .cindex "first pass routing" +.cindex "queue runner" "two phase" An option starting with &%-qq%& requests a two-stage queue run. In the first stage, the queue is scanned as if the &%queue_smtp_domains%& option matched every domain. Addresses are routed, local deliveries happen, but no remote transports are run. -.new Performance will be best if the &%queue_run_in_order%& option is false. -.wen +If that is so and the &%queue_fast_ramp%& option is true then +in the first phase of the run, +once a threshold number of messages are routed for a given host, +a delivery process is forked in parallel with the rest of the scan. .cindex "hints database" "remembering routing" The hints database that remembers which messages are waiting for specific hosts @@ -6391,13 +6428,11 @@ local_delivery: This &(appendfile)& transport is used for local delivery to user mailboxes in traditional BSD mailbox format. -.new We prefer to avoid using &$local_part$& directly to define the mailbox filename, as it is provided by a potential bad actor. Instead we use &$local_part_data$&, the result of looking up &$local_part$& in the user database (done by using &%check_local_user%& in the the router). -.wen By default &(appendfile)& runs under the uid and gid of the local user, which requires the sticky bit to be set on the &_/var/mail_& @@ -6604,14 +6639,15 @@ cause parts of the string to be replaced by data that is obtained from the lookup. Lookups of this type are conditional expansion items. Different results can be defined for the cases of lookup success and failure. See chapter &<>&, where string expansions are described in detail. -The key for the lookup is specified as part of the string expansion. +The key for the lookup is &*specified*& as part of the string expansion. .next Lists of domains, hosts, and email addresses can contain lookup requests as a way of avoiding excessively long linear lists. In this case, the data that is returned by the lookup is often (but not always) discarded; whether the lookup succeeds or fails is what really counts. These kinds of list are described in chapter &<>&. -The key for the lookup is given by the context in which the list is expanded. +The key for the lookup is &*implicit*&, +given by the context in which the list is expanded. .endlist String expansions, lists, and lookups interact with each other in such a way @@ -6646,7 +6682,8 @@ The result of the expansion is not tainted. In the second example, the lookup is a single item in a domain list. It causes Exim to use a lookup to see if the domain that is being processed can be found -in the file. The file could contains lines like this: +in the file. +The file could contains lines like this: .code domain1: domain2: @@ -6663,6 +6700,18 @@ If the value of &$sender_host_address$& is 192.168.5.6, expansion of the first &%domains%& setting above generates the second setting, which therefore causes a second lookup to occur. +.new +The lookup type may optionally be followed by a comma +and a comma-separated list of options. +Each option is a &"name=value"& pair. +Whether an option is meaningful depends on the lookup type. + +All lookups support the option &"cache=no_rd"&. +If this is given then the cache that Exim manages for lookup results +is not checked before doing the lookup. +The result of the lookup is still written to the cache. +.wen + The rest of this chapter describes the different lookup types that are available. Any of them can be used in any part of the configuration where a lookup is permitted. @@ -6677,10 +6726,16 @@ Two different types of data lookup are implemented: The &'single-key'& type requires the specification of a file in which to look, and a single key to search for. The key must be a non-empty string for the lookup to succeed. The lookup type determines how the file is searched. -.new .cindex "tainted data" "single-key lookups" The file string may not be tainted -.wen + +.cindex "tainted data" "de-tainting" +All single-key lookups support the option &"ret=key"&. +If this is given and the lookup +(either underlying implementation or cached value) +returns data, the result is replaced with a non-tainted +version of the lookup key. +.cindex "tainted data" "de-tainting" .next .cindex "query-style lookup" "definition of" The &'query-style'& type accepts a generalized database query. No particular @@ -6773,15 +6828,12 @@ by default, but has an option to omit them (see section &<>&). .cindex "lookup" "dsearch" .cindex "dsearch lookup type" &(dsearch)&: The given file must be an -.new absolute -.wen directory path; this is searched for an entry whose name is the key by calling the &[lstat()]& function. The key may not contain any forward slash characters. If &[lstat()]& succeeds then so does the lookup. -.new .cindex "tainted data" "dsearch result" The result is regarded as untainted. @@ -6805,7 +6857,6 @@ ${lookup {passwd} dsearch,filter=file {/etc}} .endd The default matching is for any entry type, including directories and symlinks. -.wen An example of how this lookup can be used to support virtual domains is given in section @@ -6841,6 +6892,13 @@ the implicit key is the host's IP address rather than its name (see section &*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this notation before executing the lookup.) + +.new +One option is supported, "ret=full", to request the return of the entire line +rather than omitting the key porttion. +Note however that the key portion will have been de-quoted. +.wen + .next .cindex lookup json .cindex json "lookup type" @@ -6858,6 +6916,29 @@ The final resulting element can be a simple JSON type or a JSON object or array; for the latter two a string-representation of the JSON is returned. For elements of type string, the returned value is de-quoted. + + +.new +.next +.cindex LMDB +.cindex lookup lmdb +.cindex database lmdb +&(lmdb)&: The given file is an LMDB database. +LMDB is a memory-mapped key-value store, +with API modeled loosely on that of BerkeleyDB. +See &url(https://symas.com/products/lightning-memory-mapped-database/) +for the feature set and operation modes. + +Exim provides read-only access via the LMDB C library. +The library can be obtained from &url(https://github.com/LMDB/lmdb) +or your operating system package repository. +To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&. + +You will need to separately create the LMDB database file, +possibly using the &"mdb_load"& utility. +.wen + + .next .cindex "linear search" .cindex "lookup" "lsearch" @@ -7054,11 +7135,7 @@ passed to a Redis database. See section &<>&. .cindex "sqlite lookup type" .cindex "lookup" "sqlite" &(sqlite)&: The format of the query is -new -an optional filename -.wen -followed by an SQL statement -that is passed to an SQLite database. See section &<>&. +an SQL statement that is passed to an SQLite database. See section &<>&. .next &(testdb)&: This is a lookup type that is used for testing Exim. It is @@ -8019,14 +8096,12 @@ The &%quote_redis%& expansion operator escapes whitespace and backslash characters with a backslash. .section "Specifying the server in the query" "SECTspeserque" -.new For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase), it is possible to specify a list of servers with an individual query. This is done by appending a comma-separated option to the query type: .display -.endd &`,servers=`&&'server1:server2:server3:...'& -.wen +.endd Each item in the list may take one of two forms: .olist If it contains no slashes it is assumed to be just a host name. The appropriate @@ -8060,8 +8135,7 @@ option, you can still update it by a query of this form: ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} } .endd -.new -An older syntax places the servers speciification before the qury, +An older syntax places the servers specification before the query, semicolon separated: .code ${lookup mysql{servers=master; UPDATE ...} } @@ -8069,7 +8143,6 @@ ${lookup mysql{servers=master; UPDATE ...} } The new version avoids potential issues with tainted arguments in the query, for explicit expansion. &*Note*&: server specifications in list-style lookups are still problematic. -.wen .section "Special MySQL features" "SECID73" @@ -8123,19 +8196,26 @@ daemon as in the other SQL databases. .new .oindex &%sqlite_dbfile%& -The preferred way of specifying the file is by using the -&%sqlite_dbfile%& option, set to -an absolute path. +There are two ways of +specifying the file. +The first is is by using the &%sqlite_dbfile%& main option. +The second, which allows separate files for each query, +is to use an option appended, comma-separated, to the &"sqlite"& +lookup type word. The option is the word &"file"&, then an equals, +then the filename. +The filename in this case cannot contain whitespace or open-brace charachters. .wen + A deprecated method is available, prefixing the query with the filename separated by white space. -This means that the path name cannot contain white space. +This means that .cindex "tainted data" "sqlite file" -It also means that the query cannot use any tainted values, as that taints +the query cannot use any tainted values, as that taints the entire query including the filename - resulting in a refusal to open the file. -.new +In all the above cases the filename must be an absolute path. + Here is a lookup expansion example: .code sqlite_dbfile = /some/thing/sqlitedb @@ -8147,7 +8227,6 @@ In a list, the syntax is similar. For example: domainlist relay_to_domains = sqlite;\ select * from relays where ip='$sender_host_address'; .endd -.wen The only character affected by the &%quote_sqlite%& operator is a single quote, which it doubles. @@ -8337,7 +8416,6 @@ in the previous section. You could also use the &(wildlsearch)& or -.new .section "Results of list checking" SECTlistresults The primary result of doing a list check is a truth value. In some contexts additional information is stored @@ -8361,7 +8439,6 @@ will store a result in the &$recipient_data$& variable. The detail of the additional information depends on the type of match and is given below as the &*value*& information. -.wen @@ -8424,7 +8501,6 @@ domainlist dom2 = !a.b : *.b where &'x.y'& does not match. It's best to avoid negation altogether in referenced lists if you can. -.new .cindex "hiding named list values" .cindex "named lists" "hiding value of" Some named list definitions may contain sensitive data, for example, passwords for @@ -8434,7 +8510,6 @@ word &"hide"&. For example: .code hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ... .endd -.wen Named lists may have a performance advantage. When Exim is routing an @@ -8529,9 +8604,7 @@ as set by the &%primary_hostname%& option (or defaulted). This makes it possible to use the same configuration file on several different hosts that differ only in their names. -.new The value for a match will be the primary host name. -.wen .next @@ -8546,9 +8619,7 @@ control which of a host's several IP addresses are treated as local. In today's Internet, the use of domain literals is controversial; see the &%allow_domain_literals%& main option. -.new The value for a match will be the string &`@[]`&. -.wen .next @@ -8599,9 +8670,7 @@ involved, it is easiest to change the delimiter for the main list as well: domains = >&) to specify that it is not to be expanded (unless you really do want to build a regular expression by expansion, of course). -.new The value for a match will be the list element string (starting with the circumflex). Additionally, &$0$& will be set to the string matching the regular expression, and &$1$& (onwards) to any submatches identified by parentheses. -.wen @@ -8704,13 +8769,11 @@ variable and can be referred to in other options. The value will be untainted. .next -.new If the pattern starts with the name of a lookup type of either kind (single-key or query-style) it may be followed by a comma and options, The options are lookup-type specific and consist of a comma-separated list. Each item starts with a tag and and equals "=". -.wen .next .cindex "domain list" "matching literal domain name" @@ -8721,8 +8784,13 @@ The value for a match will be the list element string. .cindex "tainted data" "de-tainting" Note that this is commonly untainted (depending on the way the list was created). +Specifically, explicit text in the configuration file in not tainted. This is a useful way of obtaining an untainted equivalent to the domain, for later operations. + +However if the list (including one-element lists) +is created by expanding a variable containing tainted data, +it is tainted and so will the match value be. .endlist @@ -9395,6 +9463,9 @@ become case-sensitive after &"+caseful"& has been seen. .section "Local part lists" "SECTlocparlis" .cindex "list" "local part list" .cindex "local part" "list" +These behave in the same way as domain and host lists, with the following +changes: + Case-sensitivity in local part lists is handled in the same way as for address lists, as just described. The &"+caseful"& item can be used if required. In a setting of the &%local_parts%& option in a router with &%caseful_local_part%& @@ -9439,10 +9510,22 @@ the data type. ACL rules always expand strings. A couple of expansion conditions do not expand some of the brace-delimited branches, for security reasons, .cindex "tainted data" expansion +.cindex "tainted data" definition .cindex expansion "tainted data" and expansion of data deriving from the sender (&"tainted data"&) is not permitted. +.new +Common ways of obtaining untainted equivalents of variables with +tainted values +.cindex "tainted data" "de-tainting" +come down to using the tainted value as a lookup key in a trusted database. +This database could be the filesystem structure, +or the password file, +or accessed via a DBMS. +Specific methods are indexed under &"de-tainting"&. +.wen + .section "Literal text in expanded strings" "SECTlittext" @@ -10019,11 +10102,9 @@ newline at the very end. For the &%header%& and &%bheader%& expansion, for those headers that contain lists of addresses, a comma is also inserted at the junctions between headers. This does not happen for the &%rheader%& expansion. -.new .cindex "tainted data" When the headers are from an incoming message, the result of expanding any of these variables is tainted. -.wen .vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*& @@ -10156,12 +10237,21 @@ extracted is used. You can use &`fail`& instead of {<&'string3'&>} as in a string extract. -.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&& - {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" -This is the first of one of two different types of lookup item, which are both -described in the next item. +.new +.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*& +.cindex quoting "for list" +.cindex list quoting +This item doubles any occurrence of the separator character +in the given string. +An empty string is replaced with a single space. +This converts the string into a safe form for use as a list element, +in a list using the given separator. +.wen + -.vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&& +.vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&& + {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&& + "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&& {*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" .cindex "expansion" "lookup in" .cindex "file" "lookups" @@ -10373,7 +10463,6 @@ Example: ${readsocket{/socket/name}{request string}{3s:shutdown=no}} .endd -.new The following option names are recognised: .ilist &*cache*& @@ -10395,7 +10484,6 @@ Controls the use of TLS on the connection. Values are &"yes"& or &"no"& (the default). If it is enabled, a shutdown as descripbed above is never done. .endlist -.wen A fourth argument allows you to change any newlines that are in the data @@ -10597,6 +10685,14 @@ ${sort {${lookup dnsdb{>:,,mx=example.com}}} {<} {${listextract{1}{<,$item}}}} will sort an MX lookup into priority order. + +.new +.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*& +SRS encoding. See SECT &<>& for details. +.wen + + + .vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& .cindex "&%substr%& expansion item" .cindex "substring extraction" @@ -11575,6 +11671,11 @@ condition is true if the named file (or directory) exists. The existence test is done by calling the &[stat()]& function. The use of the &%exists%& test in users' filter files may be locked out by the system administrator. +.new +&*Note:*& Testing a path using this condition is not a sufficient way of +de-tainting it. +.wen + .vitem &*first_delivery*& .cindex "delivery" "first" .cindex "first delivery" @@ -11659,6 +11760,13 @@ includes the case of letters, whereas for &%gti%& the comparison is case-independent. Case and collation order are defined per the system C locale. + +.new +.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*& +SRS decode. See SECT &<>& for details. +.wen + + .vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "string" "comparison" @@ -11908,15 +12016,12 @@ request, for a password, so the data consists of just two strings. There can be problems if any of the strings are permitted to contain colon characters. In the usual way, these have to be doubled to avoid being taken as -separators. If the data is being inserted from a variable, the &%sg%& expansion -item can be used to double any existing colons. For example, the configuration +separators. +The &%listquote%& expansion item can be used for this. +For example, the configuration of a LOGIN authenticator might contain this setting: .code -server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}} -.endd -For a PLAIN authenticator you could use: -.code -server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}} +server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}} .endd In some operating systems, PAM authentication can be done only from a process running as root. Since Exim is running as the Exim user when receiving @@ -12311,13 +12416,6 @@ contain the trailing slash. If &$config_file$& does not contain a slash, .vindex "&$config_file$&" The name of the main configuration file Exim is using. -.vitem &$dmarc_domain_policy$& &&& - &$dmarc_status$& &&& - &$dmarc_status_text$& &&& - &$dmarc_used_domains$& -Results of DMARC verification. -For details see section &<>&. - .vitem &$dkim_verify_status$& Results of DKIM verification. For details see section &<>&. @@ -12350,6 +12448,13 @@ When a message has been received this variable contains a colon-separated list of signer domains and identities for the message. For details see section &<>&. +.vitem &$dmarc_domain_policy$& &&& + &$dmarc_status$& &&& + &$dmarc_status_text$& &&& + &$dmarc_used_domains$& +Results of DMARC verification. +For details see section &<>&. + .vitem &$dnslist_domain$& &&& &$dnslist_matched$& &&& &$dnslist_text$& &&& @@ -12418,29 +12523,34 @@ When the &%smtp_etrn_command%& option is being expanded, &$domain$& contains the complete argument of the ETRN command (see section &<>&). .endlist -.new .cindex "tainted data" If the origin of the data is an incoming message, -the result of expanding this variable is tainted. -When un untainted version is needed, one should be obtained from +the result of expanding this variable is tainted and may not +be further expanded or used as a filename. +When an untainted version is needed, one should be obtained from looking up the value in a local (therefore trusted) database. Often &$domain_data$& is usable in this role. -.wen .vitem &$domain_data$& .vindex "&$domain_data$&" -When the &%domains%& option on a router matches a domain by -means of a lookup, the data read by the lookup is available during the running -of the router as &$domain_data$&. In addition, if the driver routes the +When the &%domains%& condition on a router +.new +or an ACL +matches a domain +against a list, the match value is copied to &$domain_data$&. +This is an enhancement over previous versions of Exim, when it only +applied to the data read by a lookup. +For details on match values see section &<>& et. al. +.wen + +If the router routes the address to a transport, the value is available in that transport. If the transport is handling multiple addresses, the value from the first address is used. -&$domain_data$& is also set when the &%domains%& condition in an ACL matches a -domain by means of a lookup. The data read by the lookup is available during -the rest of the ACL statement. In all other situations, this variable expands -to nothing. +&$domain_data$& set in an ACL is available during +the rest of the ACL statement. .vitem &$exim_gid$& .vindex "&$exim_gid$&" @@ -12620,10 +12730,10 @@ Global address rewriting happens when a message is received, so the value of because a message may have many recipients and the system filter is called just once. -.new .cindex "tainted data" If the origin of the data is an incoming message, -the result of expanding this variable is tainted. +the result of expanding this variable is tainted and +may not be further expanded or used as a filename. &*Warning*&: the content of this variable is usually provided by a potential attacker. @@ -12638,7 +12748,6 @@ rather than this variable. Often &$local_part_data$& is usable in this role. If needed, use a router &%address_data%& or &%set%& option for the retrieved data. -.wen When a message is being delivered to a file, pipe, or autoreply transport as a result of aliasing or forwarding, &$local_part$& is set to the local part of @@ -12674,20 +12783,16 @@ to process local parts in a case-dependent manner in a router, you can set the .vitem &$local_part_data$& .vindex "&$local_part_data$&" -When the &%local_parts%& option on a router matches a local part by means of a -lookup, the data read by the lookup is available during the running of the -router as &$local_part_data$&. In addition, if the driver routes the address -to a transport, the value is available in that transport. If the transport is -handling multiple addresses, the value from the first address is used. - +When the &%local_parts%& condition on a router or ACL +matches a local part list .new -The &%check_local_user%& router option also sets this variable. +the match value is copied to &$local_part_data$&. +This is an enhancement over previous versions of Exim, when it only +applied to the data read by a lookup. +For details on match values see section &<>& et. al. .wen -&$local_part_data$& is also set when the &%local_parts%& condition in an ACL -matches a local part by means of a lookup. The data read by the lookup is -available during the rest of the ACL statement. In all other situations, this -variable expands to nothing. +The &%check_local_user%& router option also sets this variable. .vindex &$local_part_prefix$& &&& &$local_part_prefix_v$& &&& @@ -12698,7 +12803,6 @@ If a local part prefix or suffix has been recognized, it is not included in the value of &$local_part$& during routing and subsequent delivery. The values of any prefix or suffix are in &$local_part_prefix$& and &$local_part_suffix$&, respectively. -.new .cindex "tainted data" If the specification did not include a wildcard then the affix variable value is not tainted. @@ -12707,7 +12811,6 @@ If the affix specification included a wildcard then the portion of the affix matched by the wildcard is in &$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate, and both the whole and varying values are tainted. -.wen .vitem &$local_scan_data$& .vindex "&$local_scan_data$&" @@ -13049,6 +13152,8 @@ The name of the spool queue in use; empty for the default queue. .cindex "spool" "number of messages" This variable contains the number of messages queued. It is evaluated on demand, but no more often than once every minute. +If there is no daemon notifier socket open, the value will be +an empty string. .vitem &$r_...$& .vindex &$r_...$& @@ -13364,7 +13469,6 @@ library, by setting: dns_dnssec_ok = 1 .endd -.new In addition, on Linux with glibc 2.31 or newer the resolver library will default to stripping out a successful validation status. This will break a previously working Exim installation. @@ -13374,7 +13478,6 @@ glibc to pass through any successful validation with a new option in .code options trust-ad .endd -.wen Exim does not perform DNSSEC validation itself, instead leaving that to a validating resolver (e.g. unbound, or bind with suitable configuration). @@ -13751,10 +13854,23 @@ the value of the Distinguished Name of the certificate is made available in the If certificate verification fails it may refer to a failing chain element which is not the leaf. + +.new +.vitem &$tls_in_resumption$& &&& + &$tls_out_resumption$& +.vindex &$tls_in_resumption$& +.vindex &$tls_out_resumption$& +.cindex TLS resumption +Observability for TLS session resumption. See &<>& for details. +.wen + + .vitem &$tls_in_sni$& .vindex "&$tls_in_sni$&" .vindex "&$tls_sni$&" .cindex "TLS" "Server Name Indication" +.cindex "TLS" SNI +.cindex SNI "observability on server" When a TLS session is being established, if the client sends the Server Name Indication extension, the value will be placed in this variable. If the variable appears in &%tls_certificate%& then this option and @@ -13770,6 +13886,8 @@ the outbound. .vitem &$tls_out_sni$& .vindex "&$tls_out_sni$&" .cindex "TLS" "Server Name Indication" +.cindex "TLS" SNI +.cindex SNI "observability in client" During outbound SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on the transport. @@ -14564,6 +14682,7 @@ listed in more than one group. .row &%percent_hack_domains%& "recognize %-hack for these domains" .row &%spamd_address%& "set interface to SpamAssassin" .row &%strict_acl_vars%& "object to unset ACL variables" +.row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&" .endtable @@ -14650,6 +14769,9 @@ See also the &'Policy controls'& section above. .row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures" .row &%dkim_verify_min_keysizes%& "DKIM key sizes accepted for signatures" .row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run" +.row &%dmarc_forensic_sender%& "DMARC sender for report messages" +.row &%dmarc_history_file%& "DMARC results log" +.row &%dmarc_tld_file%& "DMARC toplevel domains file" .row &%host_lookup%& "host name looked up for these hosts" .row &%host_lookup_order%& "order of DNS and local name lookups" .row &%recipient_unqualified_hosts%& "may send unqualified recipients" @@ -14751,6 +14873,7 @@ See also the &'Policy controls'& section above. .row &%hold_domains%& "hold delivery for these domains" .row &%local_interfaces%& "for routing checks" .row &%queue_domains%& "no immediate delivery for these" +.row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run" .row &%queue_only%& "no immediate delivery at all" .row &%queue_only_file%& "no immediate delivery if file exists" .row &%queue_only_load%& "no immediate delivery if load is high" @@ -15079,11 +15202,9 @@ required, it must come from the &%-oA%& command line option. This option defines a template file containing paragraphs of text to be used for constructing bounce messages. Details of the file's contents are given in chapter &<>&. -.new .cindex bounce_message_file "tainted data" The option is expanded to give the file path, which must be absolute and untainted. -.wen See also &%warn_message_file%&. @@ -15410,11 +15531,9 @@ etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines to handle IPv6 literal addresses. -.new .option dkim_verify_hashes main "string list" "sha256 : sha512" .cindex DKIM "selecting signature algorithms" This option gives a list of hash types which are acceptable in signatures, -.wen and an order of processing. Signatures with algorithms not in the list will be ignored. @@ -15433,14 +15552,12 @@ and an order of processing. Signatures with algorithms not in the list will be ignored. -.new .option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250" This option gives a list of key sizes which are acceptable in signatures. The list is keyed by the algorithm type for the key; the values are in bits. Signatures with keys smaller than given by this option will fail verification. The default enforces the RFC 8301 minimum key size for RSA signatures. -.wen .option dkim_verify_minimal main boolean false If set to true, verification of signatures will terminate after the @@ -15454,6 +15571,14 @@ the ACL once for each signature in the message. See section &<>&. +.option dmarc_forensic_sender main string&!! unset +.option dmarc_history_file main string unset +.option dmarc_tld_file main string unset +.cindex DMARC "main section options" +These options control DMARC processing. +See section &<>& for details. + + .option dns_again_means_nonexist main "domain list&!!" unset .cindex "DNS" "&""try again""& response; overriding" DNS lookups give a &"try again"& response for the DNS errors @@ -15524,7 +15649,6 @@ default. A value of 0 coerces DNSSEC off, a value of 1 coerces DNSSEC on. If the resolver library does not support DNSSEC then this option has no effect. -.new On Linux with glibc 2.31 or newer this is insufficient, the resolver library will default to stripping out a successful validation status. This will break a previously working Exim installation. @@ -15534,7 +15658,6 @@ glibc to pass through any successful validation with a new option in .code options trust-ad .endd -.wen .option dns_ipv4_lookup main "domain list&!!" unset @@ -15633,10 +15756,8 @@ and RET and ORCPT options on MAIL FROM commands. A NOTIFY=SUCCESS option requests success-DSN messages. A NOTIFY= option with no argument requests that no delay or failure DSNs are sent. -.new &*Note*&: Supplying success-DSN messages has been criticised on privacy grounds; it can leak details of internal forwarding. -.wen .option dsn_from main "string&!!" "see below" .cindex "&'From:'& header line" "in bounces" @@ -16600,7 +16721,6 @@ harm. This option overrides the &%pipe_as_creator%& option of the &(pipe)& transport driver. -.new .option notifier_socket main string "$spool_directory/exim_daemon_notify" This option gives the name for a unix-domain socket on which the daemon listens for work and information-requests. @@ -16610,12 +16730,17 @@ should need to modify the default. The option is expanded before use. If the platform supports Linux-style abstract socket names, the result is used with a nul byte prefixed. -Otherwise, it should be a full path name and use a directory accessible +Otherwise, +.new "if nonempty," +it should be a full path name and use a directory accessible to Exim. -If the Exim command line uses a &%-oX%& option and does not use &%-oP%& -then a notifier socket is not created. +.new +If this option is set as empty, +or the command line &%-oY%& option is used, or .wen +the command line uses a &%-oX%& option and does not use &%-oP%&, +then a notifier socket is not created. .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation" @@ -16927,6 +17052,17 @@ domains that do not match are processed. All other deliveries wait until the next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&. +.new +.option queue_fast_ramp main boolean false +.cindex "queue runner" "two phase" +.cindex "queue" "double scanning" +If set to true, two-phase queue runs, initiated using &%-qq%& on the +command line, may start parallel delivery processes during their first +phase. This will be done when a threshold number of messages have been +routed for a single host. +.wen + + .option queue_list_requires_admin main boolean true .cindex "restricting access to features" .oindex "&%-bp%&" @@ -17183,6 +17319,9 @@ manager, there is no way of controlling the total number of simultaneous deliveries if the configuration allows a delivery attempt as soon as a message is received. +See also the &%max_parallel%& generic transport option, +and the &%serialize_hosts%& smtp transport option. + .cindex "number of deliveries" .cindex "delivery" "maximum number of" If you want to control the total number of deliveries on the system, you @@ -17548,12 +17687,10 @@ example: smtp_etrn_command = /etc/etrn_command $domain \ $sender_host_address .endd -.new If the option is not set, the argument for the ETRN command must be a &'#'& followed by an address string. In this case an &'exim -R '& command is used; if the ETRN ACL has set up a named-queue then &'-MCG '& is appended. -.wen A new process is created to run the command, but Exim does not wait for it to complete. Consequently, its status cannot be checked. If the command cannot be @@ -17736,6 +17873,46 @@ See section &<>& for more details. This option is available when Exim is compiled with SPF support. See section &<>& for more details. +.option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why" +This option is available when Exim is compiled with SPF support. It +allows the customisation of the SMTP comment that the SPF library +generates. You are strongly encouraged to link to your own explanative +site. The template must not contain spaces. If you need spaces in the +output, use the proper placeholder. If libspf2 can not parse the +template, it uses a built-in default broken link. The following placeholders +(along with Exim variables (but see below)) are allowed in the template: +.ilist +&*%_*&: A space. +.next +&*%{L}*&: Envelope sender's local part. +.next +&*%{S}*&: Envelope sender. +.next +&*%{O}*&: Envelope sender's domain. +.next +&*%{D}*&: Current(?) domain. +.next +&*%{I}*&: SMTP client Ip. +.next +&*%{C}*&: SMTP client pretty IP. +.next +&*%{T}*&: Epoch time (UTC). +.next +&*%{P}*&: SMTP client domain name. +.next +&*%{V}*&: IP version. +.next +&*%{H}*&: EHLO/HELO domain. +.next +&*%{R}*&: Receiving domain. +.endlist +The capitalized placeholders do proper URL encoding, if you use them +lowercased, no encoding takes place. This list was compiled from the +libspf2 sources. + +A note on using Exim variables: As +currently the SPF library is initialized before the SMTP EHLO phase, +the variables useful for expansion are quite limited. .option split_spool_directory main boolean false @@ -17887,6 +18064,7 @@ syslog. The value must be no longer than 32 characters. See chapter .option syslog_timestamp main boolean true .cindex "syslog" "timestamps" +.cindex timestamps syslog If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are omitted when these lines are sent to syslog. See chapter &<>& for details of Exim's logging. @@ -18042,6 +18220,7 @@ when a list of more than one file is used, the &$tls_in_ourcert$& variable is unreliable. The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions. +.cindex SNI "selecting server certificate based on" If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then if the OpenSSL build supports TLS extensions and the TLS client sends the Server Name Indication extension, then this option and others documented in @@ -18259,6 +18438,14 @@ preference order of the available ciphers. Details are given in sections &<>& and &<>&. +.new +.option tls_resumption_hosts main "host list&!!" unset +.cindex TLS resumption +This option controls which connections to offer the TLS resumption feature. +See &<>& for details. +.wen + + .option tls_try_verify_hosts main "host list&!!" unset .cindex "TLS" "client certificate verification" .cindex "certificate" "verification of client" @@ -18455,11 +18642,9 @@ for constructing the warning message which is sent by Exim when a message has been in the queue for a specified amount of time, as specified by &%delay_warning%&. Details of the file's contents are given in chapter &<>&. -.new .cindex warn_message_file "tainted data" The option is expanded to give the file path, which must be absolute and untainted. -.wen See also &%bounce_message_file%&. @@ -18945,9 +19130,7 @@ colon-separated (by default, changeable in the usual way &<>& that is associated with any addresses that are accepted by the router. However, the option has no effect when an address is just being verified. Each list item is separately expanded, at transport time. -.new If an item ends in *, it will match any header with the given prefix. -.wen The way in which the text is used to remove header lines at transport time is described in section &<>&. Header lines are not actually removed until @@ -19060,11 +19243,9 @@ command for LMTP, SMTP, and BSMTP deliveries has the prefix removed by default. This behaviour can be overridden by setting &%rcpt_include_affixes%& true on the relevant transport. -.new .vindex &$local_part_prefix_v$& If wildcarding (above) was used then the part of the prefix matching the wildcard is available in &$local_part_prefix_v$&. -.wen When an address is being verified, &%local_part_prefix%& affects only the behaviour of the router. If the callout feature of verification is in use, this @@ -20899,7 +21080,6 @@ is not the case when the file contains syntactically valid items that happen to yield empty addresses, for example, items containing only RFC 2822 address comments. -.new .cindex "tainted data" "in filenames" .cindex redirect "tainted data" Tainted data may not be used for a filename. @@ -20910,7 +21090,6 @@ as they are provided by a potential attacker. In the examples above, &$local_part$& is used for looking up data held locally on the system, and not used directly (the second example derives &$home$& via the passsword file or database, using &$local_part$&). -.wen @@ -21137,11 +21316,9 @@ It must be given as .code list1: :include:/opt/lists/list1 .endd -.new .cindex "tainted data" "in filenames" .cindex redirect "tainted data" Tainted data may not be used for a filename. -.wen .next .cindex "address redirection" "to black hole" .cindex "delivery" "discard" @@ -22150,9 +22327,7 @@ Each list item is separately expanded. If the result of the expansion is an empty string, or if the expansion is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. -.new If an item ends in *, it will match any header with the given prefix. -.wen Matching headers are omitted from the message as it is transported, as described in section &<>&. Header removal can also be specified by @@ -22707,14 +22882,12 @@ If &%file%& or &%directory%& is set for a delivery from a redirection, it is used to determine the file or directory name for the delivery. Normally, the contents of &$address_file$& are used in some way in the string expansion. .endlist -.new .cindex "tainted data" "in filenames" .cindex appendfile "tainted data" Tainted data may not be used for a file or directory name. This means that, for instance, &$local_part$& cannot be used directly as a component of a path. It can however be used as the key for a lookup which returns a path (or component). -.wen .cindex "Sieve filter" "configuring &(appendfile)&" @@ -24152,11 +24325,9 @@ directories are also controllable. See chapter &<>& for details of the local delivery environment and chapter &<>& for a discussion of local delivery batching. -.new .cindex "tainted data" "in pipe command" .cindex pipe "tainted data" Tainted data may not be used for the command name. -.wen .section "Concurrent delivery" "SECID140" @@ -25298,9 +25469,7 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter .cindex "RFC 3030" "CHUNKING" This option provides a list of servers to which, provided they announce CHUNKING support, Exim will attempt to use BDAT commands rather than DATA. -.new Unless DKIM signing is being done, -.wen BDAT will not be used in conjunction with a transport filter. .option hosts_try_dane smtp "host list&!!" * @@ -25398,6 +25567,20 @@ so can cause parallel connections to the same host if &%remote_max_parallel%& permits this. +.new +.option message_linelength_limit smtp integer 998 +.cindex "line length" limit +This option sets the maximum line length, in bytes, that the transport +will send. Any messages with lines exceeding the given value +will fail and a failure-DSN ("bounce") message will if possible be returned +to the sender. +The default value is that defined by the SMTP standards. + +It is generally wise to also check in the data ACL so that messages +received via SMTP can be refused without producing a bounce. +.wen + + .option multi_domain smtp boolean&!! true .vindex "&$domain$&" When this option is set, the &(smtp)& transport can handle a number of @@ -25411,6 +25594,12 @@ It is expanded per-address and can depend on any of &$address_data$&, &$domain_data$&, &$local_part_data$&, &$host$&, &$host_address$& and &$host_port$&. +.new +If the connection is DANE-enabled then this option is ignored; +only messages having the domain used for the DANE TLSA lookup are +sent on the connection. +.wen + .option port smtp string&!! "see below" .cindex "port" "sending TCP/IP" .cindex "TCP/IP" "setting outgoing port" @@ -25579,11 +25768,25 @@ is used in different ways by OpenSSL and GnuTLS (see sections ciphers is a preference order. +.new +.option tls_resumption_hosts smtp "host list&!!" unset +.cindex TLS resumption +This option controls which connections to use the TLS resumption feature. +See &<>& for details. +.wen + + .option tls_sni smtp string&!! unset .cindex "TLS" "Server Name Indication" +.cindex "TLS" SNI +.cindex SNI "setting in client" .vindex "&$tls_sni$&" -If this option is set then it sets the $tls_out_sni variable and causes any +If this option is set +.new +and the connection is not DANE-validated +.wen +then it sets the $tls_out_sni variable and causes any TLS session to pass this value as the Server Name Indication extension to the remote side, which can be used by the remote side to select an appropriate certificate and private key for the session. @@ -27811,7 +28014,6 @@ connection, a client certificate has been verified, the &"valid-client-cert"& option is passed. When authentication succeeds, the identity of the user who authenticated is placed in &$auth1$&. -.new The Dovecot configuration to match the above wil look something like: .code @@ -27831,7 +28033,6 @@ conf.d/10-auth.conf :- auth_mechanisms = plain login ntlm .endd -.wen .ecindex IIDdcotauth1 .ecindex IIDdcotauth2 @@ -27858,7 +28059,6 @@ scale to handle future authentication mechanisms, so no guarantee can be made that any particular new authentication mechanism will be supported without code changes in Exim. -.new The library is expected to add support in an upcoming realease for the SCRAM-SHA-256 method. The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined @@ -27882,9 +28082,7 @@ the password to be used, in clear. .option client_username gsasl string&!! unset This option is exapanded before use, and should result in the account name to be used. -.wen -.new .option client_spassword gsasl string&!! unset If a SCRAM mechanism is being used and this option is set it is used in preference to &%client_password%&. @@ -27893,7 +28091,6 @@ a 40 (for SHA-1) or 64 (for SHA-256) character string with the PBKDF2-prepared password, hex-encoded. Note that this value will depend on the salt and iteration-count supplied by the server. -.wen @@ -27911,12 +28108,10 @@ This should have meant that certificate identity and verification becomes a non-issue, as a man-in-the-middle attack will cause the correct client and server to see different identifiers and authentication will fail. -.new This is only usable by mechanisms which support "channel binding"; at time of writing, that's the SCRAM family. When using this feature the "-PLUS" variants of the method names need to be used. -.wen This defaults off to ensure smooth upgrade across Exim releases, in case this option causes some clients to start failing. Some future release @@ -27972,7 +28167,6 @@ Some mechanisms will use this data. .option server_scram_iter gsasl string&!! 4096 This option provides data for the SCRAM family of mechanisms. -.new The &$auth1$&, &$auth2$& and &$auth3$& variables are available when this option is expanded. @@ -27983,21 +28177,17 @@ a compute cost factor imposed on the client either the iteration count or the salt). A minimum value of 4096 is required by the standards for all current SCRAM mechanism variants. -.wen .option server_scram_salt gsasl string&!! unset This option provides data for the SCRAM family of mechanisms. -.new The &$auth1$&, &$auth2$& and &$auth3$& variables are available when this option is expanded. The value should be a base64-encoded string, of random data typically 4-to-16 bytes long. If unset or empty after expansion the library will provides a value for the protocol conversation. -.wen -.new .option server_key gsasl string&!! unset .option server_skey gsasl string&!! unset These options can be used for the SCRAM family of mechanisms @@ -28023,7 +28213,6 @@ If unset or not of the right length, &%server_password%& will be used. The libgsasl library release includes a utility &'gsasl'& which can be used to generate these values. -.wen .option server_service gsasl string &`smtp`& @@ -28603,6 +28792,12 @@ Some other recently added features may only be available in one or the other. This should be documented with the feature. If the documentation does not explicitly state that the feature is infeasible in the other TLS implementation, then patches are welcome. +.new +.next +The output from "exim -bV" will show which (if any) support was included +in the build. +Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined. +.wen .endlist @@ -29076,6 +29271,61 @@ There is no current way to staple a proof for a client certificate. .endd +.new +.section "Caching of static server configuration items" "SECTserverTLScache" +.cindex certificate caching +.cindex privatekey caching +.cindex crl caching +.cindex ocsp caching +.cindex ciphers caching +.cindex "CA bundle" caching +.cindex "certificate authorities" caching +.cindex tls_certificate caching +.cindex tls_privatekey caching +.cindex tls_crl caching +.cindex tls_ocsp_file caching +.cindex tls_require_ciphers caching +.cindex tls_verify_certificate caching +.cindex caching certificate +.cindex caching privatekey +.cindex caching crl +.cindex caching ocsp +.cindex caching ciphers +.cindex caching "certificate authorities +If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&, +&%tls_crl%& and &%tls_ocsp_file%& have values with no +expandable elements, +then the associated information is loaded at daemon startup. +It is made available +to child processes forked for handling received SMTP connections. + +This caching is currently only supported under Linux. + +If caching is not possible, for example if an item has to be dependent +on the peer host so contains a &$sender_host_name$& expansion, the load +of the associated information is done at the startup of the TLS connection. + +The cache is invalidated and reloaded after any changes to the directories +containing files specified by these options. + +The information specified by the main option &%tls_verify_certificates%& +is similarly cached so long as it specifies files explicitly +or (under GnuTLS) is the string &"system,cache"&. +The latter case is not automatically invaludated; +it is the operator's responsibility to arrange for a daemon restart +any time the system certificate authority bundle is updated. +A HUP signal is sufficient for this. +The value &"system"& results in no caching under GnuTLS. + +The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system" +is acceptable in configurations for the Exim executavble. + +Caching of the system Certificate Authorities bundle can +save siginificant time and processing on every TLS connection +accepted by Exim. +.wen + + .section "Configuring an Exim client to use TLS" "SECTclientTLS" @@ -29116,7 +29366,10 @@ 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 +if it requests it. +This is an optional thing for TLS connections, although either end +may insist on 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*&: Do not use a certificate which has the OCSP-must-staple extension, @@ -29141,8 +29394,14 @@ certificate verification to the listed servers. Verification either must or need not succeed respectively. The &%tls_verify_cert_hostnames%& option lists hosts for which additional -checks are made: that the host name (the one in the DNS A record) -is valid for the certificate. +name checks are made on the server certificate. +.new +The match against this list is, as per other Exim usage, the +IP for the host. That is most closely associated with the +name on the DNS A (or AAAA) record for the host. +However, the name that needs to be in the certificate +is the one at the head of any CNAME chain leading to the A record. +.wen The option defaults to always checking. The &(smtp)& transport has two OCSP-related options: @@ -29190,8 +29449,66 @@ outgoing connection. +.new +.section "Caching of static client configuration items" "SECTclientTLScache" +.cindex certificate caching +.cindex privatekey caching +.cindex crl caching +.cindex ciphers caching +.cindex "CA bundle" caching +.cindex "certificate authorities" caching +.cindex tls_certificate caching +.cindex tls_privatekey caching +.cindex tls_crl caching +.cindex tls_require_ciphers caching +.cindex tls_verify_certificate caching +.cindex caching certificate +.cindex caching privatekey +.cindex caching crl +.cindex caching ciphers +.cindex caching "certificate authorities +If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%& +and &%tls_crl%& have values with no +expandable elements, +then the associated information is loaded per smtp transport +at daemon startup, at the start of a queue run, or on a +command-line specified message delivery. +It is made available +to child processes forked for handling making SMTP connections. + +This caching is currently only supported under Linux. + +If caching is not possible, the load +of the associated information is done at the startup of the TLS connection. + +The cache is invalidated in the daemon +and reloaded after any changes to the directories +containing files specified by these options. + +The information specified by the main option &%tls_verify_certificates%& +is similarly cached so long as it specifies files explicitly +or (under GnuTLS) is the string &"system,cache"&. +The latter case is not automatically invaludated; +it is the operator's responsibility to arrange for a daemon restart +any time the system certificate authority bundle is updated. +A HUP signal is sufficient for this. +The value &"system"& results in no caching under GnuTLS. + +The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system" +is acceptable in configurations for the Exim executavble. + +Caching of the system Certificate Authorities bundle can +save siginificant time and processing on every TLS connection +initiated by Exim. +.wen + + + + .section "Use of TLS Server Name Indication" "SECTtlssni" .cindex "TLS" "Server Name Indication" +.cindex "TLS" SNI +.cindex SNI .vindex "&$tls_in_sni$&" .oindex "&%tls_in_sni%&" With TLS1.0 or above, there is an extension mechanism by which extra @@ -29223,6 +29540,11 @@ nothing more to it. Choosing a sensible value not derived insecurely is the only point of caution. The &$tls_out_sni$& variable will be set to this string for the lifetime of the client connection (including during authentication). +.new +If DANE validated the connection attempt then the value of the &%tls_sni%& option +is forced to the domain part of the recipient address. +.wen + Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string received from a client. It can be logged with the &%log_selector%& item &`+tls_sni`&. @@ -29409,6 +29731,100 @@ Open-source PKI book, available online at .ecindex IIDencsmtp2 +.new +.section "TLS Resumption" "SECTresumption" +.cindex TLS resumption +TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined +in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1 +(or later). + +Session resumption (this is the "stateless" variant) involves the server sending +a "session ticket" to the client on one connection, which can be stored by the +client and used for a later session. The ticket contains sufficient state for +the server to reconstruct the TLS session, avoiding some expensive crypto +calculation and (on TLS1.2) one full packet roundtrip time. + +.ilist +Operational cost/benefit: + + The extra data being transmitted costs a minor amount, and the client has + extra costs in storing and retrieving the data. + + In the Exim/Gnutls implementation the extra cost on an initial connection + which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware. + The saved cost on a subsequent connection is about 4ms; three or more + connections become a net win. On longer network paths, two or more + connections will have an average lower startup time thanks to the one + saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any + packet roundtrips. + +.cindex "hints database" tls + Since a new hints DB is used on the TLS client, + the hints DB maintenance should be updated to additionally handle "tls". + +.next +Security aspects: + + The session ticket is encrypted, but is obviously an additional security + vulnarability surface. An attacker able to decrypt it would have access + all connections using the resumed session. + The session ticket encryption key is not committed to storage by the server + and is rotated regularly (OpenSSL: 1hr, and one previous key is used for + overlap; GnuTLS 6hr but does not specify any overlap). + Tickets have limited lifetime (2hr, and new ones issued after 1hr under + OpenSSL. GnuTLS 2hr, appears to not do overlap). + + There is a question-mark over the security of the Diffie-Helman parameters + used for session negotiation. + +.next +Observability: + + The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X=" + element. + + The variables &$tls_in_resumption$& and &$tls_out_resumption$& + have bits 0-4 indicating respectively + support built, client requested ticket, client offered session, + server issued ticket, resume used. A suitable decode list is provided + in the builtin macro _RESUME_DECODE for in &%listextract%& expansions. + +.next +Control: + +The &%tls_resumption_hosts%& main option specifies a hostlist for which +exim, operating as a server, will offer resumption to clients. +Current best practice is to not offer the feature to MUA connection. +Commonly this can be done like this: +.code +tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}} +.endd +If the peer host matches the list after expansion then resumption +is offered and/or accepted. + +The &%tls_resumption_hosts%& smtp transport option performs the +equivalent function for operation as a client. +If the peer host matches the list after expansion then resumption +is attempted (if a stored session is available) or the information +stored (if supplied by the peer). + + +.next +Issues: + + In a resumed session: +.ilist + The variables &$tls_{in,out}_cipher$& will have values different + to the original (under GnuTLS). +.next + The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response", + and the &%hosts_require_ocsp%& smtp trasnport option will fail. +. XXX need to do something with that hosts_require_ocsp +.endlist + +.endlist +.wen + .section DANE "SECDANE" .cindex DANE @@ -29426,7 +29842,7 @@ by (a) is thought to be smaller than that of the set of root CAs. It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply fail to pass on a server's STARTTLS. -DANE scales better than having to maintain (and side-channel communicate) copies of server certificates +DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates for every possible target server. It also scales (slightly) better than having to maintain on an SMTP client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates. @@ -29571,6 +29987,7 @@ If DANE is requested and useable (see above) the following transport options are tls_verify_certificates tls_crl tls_verify_cert_hostnames + tls_sni .endd If DANE is not usable, whether requested or not, and CA-anchored @@ -31038,7 +31455,6 @@ response to an EHLO command. Therefore, it should normally appear in an ACL controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also &%pipelining_advertise_hosts%&. -.new .vitem &*control&~=&~queue/*&<&'options'&>* &&& &*control&~=&~queue_only*& .oindex "&%queue%&" @@ -31063,7 +31479,6 @@ able to send all such messages on a single connection. The control only applies to the current message, not to any subsequent ones that may be received in the same SMTP connection. -.wen .vitem &*control&~=&~submission/*&<&'options'&> .cindex "message" "submission" @@ -31577,8 +31992,9 @@ send email. Details of how this works are given in section .cindex "header lines" "verifying header names only ASCII" .cindex "verifying" "header names only ASCII" This condition is relevant only in an ACL that is run after a message has been -received, that is, in an ACL specified by &%acl_smtp_data%& or -&%acl_not_smtp%&. It checks all header names (not the content) to make sure +received. +This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&. +It checks all header names (not the content) to make sure there are no non-ASCII characters, also excluding control characters. The allowable characters are decimal ASCII values 33 through 126. @@ -31733,7 +32149,7 @@ Note that '/' is legal in local-parts; if the address may have such (eg. is generated from the received message) they must be protected from the options parsing by doubling: .code -verify = sender=${sg{${address:$h_sender:}}{/}{//}} +verify = sender=${listquote{/}{${address:$h_sender:}}} .endd .endlist @@ -32315,7 +32731,7 @@ in kilobytes, megabytes, or gigabytes, respectively. The &%per_rcpt%& option causes Exim to limit the rate at which recipients are accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, -&%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In +&%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other ACLs the rate is updated with the total (accepted) recipient count in one go. Note that in either case the rate limiting engine will see a message with many @@ -32531,6 +32947,15 @@ The &%success_on_redirect%& option causes verification always to succeed immediately after a successful redirection. By default, if a redirection generates just one address, that address is also verified. See further discussion in section &<>&. +.new +.next +If the &%quota%& option is specified for recipient verify, +successful routing to an appendfile transport is followed by a call into +the transport to evaluate the quota status for the recipient. +No actual delivery is done, but verification will succeed if the quota +is sufficient for the message (if the sender gave a message size) or +not already exceeded (otherwise). +.wen .endlist .cindex "verifying address" "differentiating failures" @@ -32564,6 +32989,9 @@ connection, HELO, or MAIL). &%recipient%&: The RCPT command in a callout was rejected. .next &%postmaster%&: The postmaster check in a callout was rejected. +.new +.next +&%quota%&: The quota check for a local recipient did non pass. .endlist The main use of these variables is expected to be to distinguish between @@ -32893,6 +33321,38 @@ behaviour will be the same. +.new +.section "Quota caching" "SECTquotacache" +.cindex "hints database" "quota cache" +.cindex "quota" "cache, description of" +.cindex "caching" "quota" +Exim caches the results of quota verification +in order to reduce the amount of resources used. +The &"callout"& hints database is used. + +The default cache periods are five minutes for a positive (good) result +and one hour for a negative result. +To change the periods the &%quota%& option can be followed by an equals sign +and a number of optional paramemters, separated by commas. +For example: +.code +verify = recipient/quota=cachepos=1h,cacheneg=1d +.endd +Possible parameters are: +.vlist +.vitem &*cachepos&~=&~*&<&'time&~interval'&> +.cindex "quota cache" "positive entry expiry, specifying" +Set the lifetime for a positive cache entry. +A value of zero seconds is legitimate. + +.vitem &*cacheneg&~=&~*&<&'time&~interval'&> +.cindex "quota cache" "negative entry expiry, specifying" +As above, for a negative entry. + +.vitem &*no_cache*& +Set both positive and negative lifetimes to zero. +.wen + .section "Sender address verification reporting" "SECTsenaddver" .cindex "verifying" "suppressing error details" See section &<>& for a general discussion of @@ -34210,10 +34670,8 @@ HAVE_LOCAL_SCAN=yes LOCAL_SCAN_SOURCE=Local/local_scan.c .endd for example. The function must be called &[local_scan()]&; -.new the source file(s) for it should first #define LOCAL_SCAN and then #include "local_scan.h". -.wen It is called by Exim after it has received a message, when the success return code is about to be sent. This is after all the ACLs have been run. The return code from your @@ -34894,7 +35352,6 @@ dropping of a TCP/IP connection), you can call &'smtp_fflush()'&, which has no arguments. It flushes the output stream, and returns a non-zero value if there is an error. -.new .vitem &*void&~*store_get(int,BOOL)*& This function accesses Exim's internal store (memory) manager. It gets a new chunk of memory whose size is given by the first argument. @@ -34903,7 +35360,6 @@ data possibly coming from an attacker (eg. the message content), FALSE if it is locally-sourced. Exim bombs out if it ever runs out of memory. See the next section for a discussion of memory handling. -.wen .vitem &*void&~*store_get_perm(int,BOOL)*& This function is like &'store_get()'&, but it always gets memory from the @@ -35224,14 +35680,14 @@ address if its delivery failed. .section "Per-address filtering" "SECTperaddfil" -.vindex "&$domain$&" -.vindex "&$local_part$&" +.vindex "&$domain_data$&" +.vindex "&$local_part_data$&" In contrast to the system filter, which is run just once per message for each delivery attempt, it is also possible to set up a system-wide filtering operation that runs once for each recipient address. In this case, variables -such as &$local_part$& and &$domain$& can be used, and indeed, the choice of -filter file could be made dependent on them. This is an example of a router -which implements such a filter: +such as &$local_part_data$& and &$domain_data$& can be used, +and indeed, the choice of filter file could be made dependent on them. +This is an example of a router which implements such a filter: .code central_filter: check_local_user @@ -37017,13 +37473,11 @@ virtual: data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}} no_more .endd -.new The &%domains%& option specifies that the router is to be skipped, unless there is a file in the &_/etc/mail/virtual_& directory whose name is the same as the domain that is being processed. The &(dsearch)& lookup used results in an untainted version of &$domain$& being placed into the &$domain_data$& variable. -.wen When the router runs, it looks up the local part in the file to find a new address (or list of addresses). The &%no_more%& @@ -37054,7 +37508,7 @@ follows: .code my_mailboxes: driver = appendfile - file = /var/mail/$domain/$local_part_data + file = /var/mail/$domain_data/$local_part_data user = mail .endd This uses a directory of mailboxes for each domain. The &%user%& setting is @@ -37094,7 +37548,7 @@ It runs a user's &_.forward_& file for all local parts of the form cases by testing the variable &$local_part_suffix$&. For example: .code if $local_part_suffix contains -special then -save /home/$local_part/Mail/special +save /home/$local_part_data/Mail/special endif .endd If the filter file does not exist, or does not deal with such addresses, they @@ -37759,7 +38213,8 @@ fields record the router and transport that were used to process the address. If SMTP AUTH was used for the delivery there is an additional item A= followed by the name of the authenticator that was used. If an authenticated identification was set up by the authenticator's &%client_set_id%& -option, this is logged too, separated by a colon from the authenticator name. +option, this is logged too, as a second colon-separated list item. +Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item. If a shadow transport was run after a successful local delivery, the log line for the successful delivery has an item added on the end, of the form @@ -38028,6 +38483,7 @@ selection marked by asterisks: &`*tls_certificate_verified `& certificate verification status &`*tls_cipher `& TLS cipher suite on <= and => lines &` tls_peerdn `& TLS peer DN on <= and => lines +&` tls_resumption `& append * to cipher field &` tls_sni `& TLS SNI on <= lines &` unknown_in_list `& DNS lookup failed in list match @@ -38429,8 +38885,17 @@ connection, the cipher suite used is added to the log line, preceded by X=. connection, and a certificate is supplied by the remote host, the peer DN is added to the log line, preceded by DN=. .next +.cindex "log" "TLS resumption" +.cindex "TLS" "logging session resumption" +.new +&%tls_resumption%&: When a message is sent or received over an encrypted +connection and the TLS session resumed one used on a previous TCP connection, +an asterisk is appended to the X= cipher field in the log line. +.wen +.next .cindex "log" "TLS SNI" .cindex "TLS" "logging SNI" +.cindex SNI logging &%tls_sni%&: When a message is received over an encrypted connection, and the remote host provided the Server Name Indication extension, the SNI is added to the log line, preceded by SNI=. @@ -38487,9 +38952,9 @@ the next chapter. The utilities described here are: "check address acceptance from given IP" .irow &<>& &'exim_dbmbuild'& "build a DBM file" .irow &<>& &'exinext'& "extract retry information" -.irow &<>& &'exim_dumpdb'& "dump a hints database" -.irow &<>& &'exim_tidydb'& "clean up a hints database" -.irow &<>& &'exim_fixdb'& "patch a hints database" +.irow &<>& &'exim_dumpdb'& "dump a hints database" +.irow &<>& &'exim_tidydb'& "clean up a hints database" +.irow &<>& &'exim_fixdb'& "patch a hints database" .irow &<>& &'exim_lock'& "lock a mailbox file" .endtable @@ -38974,6 +39439,10 @@ for remote hosts .next &'ratelimit'&: the data for implementing the ratelimit ACL condition .next +.new +&'tls'&: TLS session resumption data +.wen +.next &'misc'&: other hints data .endlist @@ -38991,7 +39460,7 @@ in a transport) -.section "exim_dumpdb" "SECID261" +.section "exim_dumpdb" "SECTdumpdb" .cindex "&'exim_dumpdb'&" The entire contents of a database are written to the standard output by the &'exim_dumpdb'& program, which has no options or arguments other than the @@ -39028,7 +39497,7 @@ cross-references. -.section "exim_tidydb" "SECID262" +.section "exim_tidydb" "SECTtidydb" .cindex "&'exim_tidydb'&" The &'exim_tidydb'& utility program is used to tidy up the contents of a hints database. If run with no options, it removes all records that are more than 30 @@ -39077,7 +39546,7 @@ databases is likely to keep on increasing. -.section "exim_fixdb" "SECID263" +.section "exim_fixdb" "SECTfixdb" .cindex "&'exim_fixdb'&" The &'exim_fixdb'& program is a utility for interactively modifying databases. Its main use is for testing Exim, but it might also be occasionally useful for @@ -40387,8 +40856,8 @@ There is no dot-stuffing (and no dot-termination). . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// -.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&& - "DKIM, SPF and DMARC Support" +.chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&& + "DKIM, SPF, SRS and DMARC Support" .section "DKIM (DomainKeys Identified Mail)" SECDKIM .cindex "DKIM" @@ -40463,7 +40932,7 @@ but for EC keys it is the base64 of the pure key; no ASN.1 wrapping. Signing is enabled by setting private options on the SMTP transport. These options take (expandable) strings as arguments. -.option dkim_domain smtp string list&!! unset +.option dkim_domain smtp "string list&!!" unset The domain(s) you want to sign with. After expansion, this can be a list. Each element in turn, @@ -40473,7 +40942,7 @@ while expanding the remaining signing options. If it is empty after expansion, DKIM signing is not done, and no error will result even if &%dkim_strict%& is set. -.option dkim_selector smtp string list&!! unset +.option dkim_selector smtp "string list&!!" unset This sets the key selector string. After expansion, which can use &$dkim_domain$&, this can be a list. Each element in turn is put in the expansion @@ -40593,9 +41062,7 @@ When unspecified, the header names listed in RFC4871 will be used, whether or not each header is present in the message. The default list is available for the expansion in the macro &"_DKIM_SIGN_HEADERS"& -.new and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&. -.wen If a name is repeated, multiple headers by that name (or the absence thereof) will be signed. The textually later headers in the headers part of the @@ -40846,10 +41313,8 @@ Notes from the key record (tag n=). .vitem &%$dkim_key_length%& Number of bits in the key. -.new Valid only once the key is loaded, which is at the time the header signature is verified, which is after the body hash is. -.wen Note that RFC 8301 says: .code @@ -40975,13 +41440,16 @@ deny spf = fail message = $sender_host_address is not allowed to send mail from \ ${if def:sender_address_domain \ {$sender_address_domain}{$sender_helo_name}}. \ - Please see http://www.open-spf.org/Why?scope=\ - ${if def:sender_address_domain {mfrom}{helo}};\ + Please see http://www.open-spf.org/Why;\ identity=${if def:sender_address_domain \ {$sender_address}{$sender_helo_name}};\ ip=$sender_host_address .endd +Note: The above mentioned URL may not be as helpful as expected. You are +encouraged to replace the link with a link to a site with more +explanations. + When the spf condition has run, it sets up several expansion variables: @@ -41016,8 +41484,11 @@ variables: .vitem &$spf_smtp_comment$& .vindex &$spf_smtp_comment$& +.vindex &%spf_smtp_comment_template%& This contains a string that can be used in a SMTP response to the calling party. Useful for "fail". + The string is generated by the SPF library from the template configured in the main config + option &%spf_smtp_comment_template%&. .endlist @@ -41078,6 +41549,108 @@ The lookup will return the same result strings as can appear in +.section "SRS (Sender Rewriting Scheme)" SECTSRS +.cindex SRS "sender rewriting scheme" + +.new +SRS can be used to modify sender addresses when forwarding so that +SPF verification does not object to them. +It operates by encoding the original envelope sender in a new +sender local part and using a domain run by the forwarding site +as the new domain for the sender. Any DSN message should be returned +to this new sender at the forwarding site, which can extract the +original sender from the coded local part and forward the DSN to +the originator. + +This is a way of avoiding the breakage that SPF does to forwarding. +The constructed local-part will be longer than the original, +leading to possible problems with very long addresses. +The changing of the sender address also hinders the tracing of mail +problems. + +Exim can be built to include native SRS support. To do this +SUPPORT_SRS=yes must be defined in &_Local/Makefile_&. +If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS +will be defined. +The support is limited to SRS0-encoding; SRS1 is not supported. + +.cindex SRS excoding +To encode an address use this expansion item: +.vlist +.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*& +.cindex "&%srs_encode%& expansion item" +.cindex SRS "expansion item" +The first argument should be a secret known and used by all systems +handling the recipient domain for the original message. +There is no need to periodically change this key; a timestamp is also +encoded. +The second argument should be given as the envelope sender address before this +encoding operation. +The third argument should be the recipient domain of the message when +it arrived at this system. +.endlist + +.cindex SRS decoding +To decode an address use this expansion condition: +.vlist +.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*& +The first argument should be the recipient local prt as is was received. +The second argument is the site secret. + +If the messages is not for an SRS-encoded recipient the condition will +return false. If it is, the condition will return true and the variable +&$srs_recipient$& will be set to the decoded (original) value. +.endlist + +Example usage: +.code + #macro + SRS_SECRET = + + #routers + + outbound: + driver = dnslookup + # if outbound, and forwarding has been done, use an alternate transport + domains = ! +my_domains + transport = ${if eq {$local_part@$domain} \ + {$original_local_part@$original_domain} \ + {remote_smtp} {remote_forwarded_smtp}} + + inbound_srs: + driver = redirect + senders = : + domains = +my_domains + # detect inbound bounces which are SRS'd, and decode them + condition = ${if inbound_srs {$local_part} {SRS_SECRET}} + data = $srs_recipient + + inbound_srs_failure: + driver = redirect + senders = : + domains = +my_domains + # detect inbound bounces which look SRS'd but are invalid + condition = ${if inbound_srs {$local_part} {}} + allow_fail + data = :fail: Invalid SRS recipient address + + #... further routers here + + + # transport; should look like the non-forward outbound + # one, plus the max_rcpt and return_path options + remote_forwarded_smtp: + driver = smtp + # modify the envelope from, for mails that we forward + max_rcpt = 1 + return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}} +.endd + + +.wen + + + .section DMARC SECDMARC .cindex DMARC verification @@ -41112,10 +41685,8 @@ during domain parsing. Maintained by Mozilla, the most current version can be downloaded from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat). See also the util/renew-opendmarc-tlds.sh script. -.new The default for the option is unset. If not set, DMARC processing is disabled. -.wen The &%dmarc_history_file%& option, if set @@ -41194,7 +41765,7 @@ mean, refer to the DMARC website above. Valid strings are: &'reject '& The DMARC check failed and the library recommends rejecting the email. &'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection. &'none '& The DMARC check passed and the library recommends no specific action, neutral. -&'norecord '& No policy section in the DMARC record for this sender domain. +&'norecord '& No policy section in the DMARC record for this RFC5322.From field &'nofrom '& Unable to determine the domain of the sender. &'temperror '& Library error or dns error. &'off '& The DMARC check was disabled for this email. @@ -41644,9 +42215,7 @@ Events have names which correspond to the point in process at which they fire. The name is placed in the variable &$event_name$& and the event action expansion must check this, as it will be called for every possible event type. -.new The current list of events is: -.wen .display &`dane:fail after transport `& per connection &`msg:complete after main `& per message