X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/ef546e788203ac3881abe2ddb17f3e24f6524d15..05d83295725e9bb91c1c37108d2d8892ee4a2bfd:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index b1387eb49..1b024f8f5 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 @@ -4397,7 +4400,6 @@ 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 +4408,6 @@ 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%&" @@ -4518,14 +4519,17 @@ 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 +6395,11 @@ 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_& @@ -6668,6 +6670,11 @@ 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 depands 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 diong 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 @@ -6684,7 +6691,6 @@ 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 @@ -6694,7 +6700,7 @@ 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. -.wen +.cindex "tainted data" "de-tainting" .next .cindex "query-style lookup" "definition of" The &'query-style'& type accepts a generalized database query. No particular @@ -6787,15 +6793,12 @@ 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. @@ -6819,7 +6822,6 @@ ${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 @@ -6872,6 +6874,29 @@ 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" @@ -7070,7 +7095,6 @@ passed to a Redis database. See section &<>&. &(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 &<>&. @@ -8033,14 +8057,12 @@ 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 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 @@ -8074,7 +8096,6 @@ 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, semicolon separated: .code @@ -8083,7 +8104,6 @@ ${lookup mysql{servers=master; UPDATE ...} } The new version avoids potential issues with tainted arguments in the query, for explicit expansion. &*Note*&: server specifications in list-style lookups are still problematic. -.wen .section "Special MySQL features" "SECID73" @@ -8135,12 +8155,10 @@ SQLite is different to the other SQL lookups because a filename is required in addition to the SQL query. An SQLite database is a single file, and there is no daemon as in the other SQL databases. -.new .oindex &%sqlite_dbfile%& The preferred way of specifying the file is by using the &%sqlite_dbfile%& option, set to an absolute path. -.wen A deprecated method is available, prefixing the query with the filename separated by white space. This means that the path name cannot contain white space. @@ -8149,7 +8167,6 @@ It also means that the query cannot use any tainted values, as that taints the entire query including the filename - resulting in a refusal to open the file. -.new Here is a lookup expansion example: .code sqlite_dbfile = /some/thing/sqlitedb @@ -8161,7 +8178,6 @@ In a list, the syntax is similar. For example: domainlist relay_to_domains = sqlite;\ select * from relays where ip='$sender_host_address'; .endd -.wen The only character affected by the &%quote_sqlite%& operator is a single quote, which it doubles. @@ -8351,7 +8367,6 @@ 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 @@ -8375,7 +8390,6 @@ 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 @@ -8438,7 +8452,6 @@ 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 @@ -8448,7 +8461,6 @@ 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 @@ -8543,9 +8555,7 @@ 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 @@ -8560,9 +8570,7 @@ 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 @@ -8613,9 +8621,7 @@ 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 @@ -8718,13 +8720,11 @@ 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" @@ -10033,11 +10033,9 @@ 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 &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*& @@ -10170,6 +10168,18 @@ extracted is used. You can use &`fail`& instead of {<&'string3'&>} as in a string extract. +.new +.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*" +.citem quoting "for list" +.citem 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{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&& {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" This is the first of one of two different types of lookup item, which are both @@ -10387,7 +10397,6 @@ Example: ${readsocket{/socket/name}{request string}{3s:shutdown=no}} .endd -.new The following option names are recognised: .ilist &*cache*& @@ -10409,7 +10418,6 @@ 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 @@ -10611,6 +10619,14 @@ ${sort {${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" @@ -11673,6 +11689,13 @@ 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" @@ -11922,15 +11945,12 @@ 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 @@ -12432,14 +12452,12 @@ 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 looking up the value in a local (therefore trusted) database. Often &$domain_data$& is usable in this role. -.wen .vitem &$domain_data$& @@ -12634,7 +12652,6 @@ 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. @@ -12652,7 +12669,6 @@ 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 @@ -12694,9 +12710,7 @@ 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. -.new The &%check_local_user%& router option also sets this variable. -.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 @@ -12712,7 +12726,6 @@ 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. @@ -12721,7 +12734,6 @@ 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 "&$local_scan_data$&" @@ -13378,7 +13390,6 @@ 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. @@ -13388,7 +13399,6 @@ 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). @@ -13765,6 +13775,17 @@ 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 "&$tls_sni$&" @@ -14769,6 +14790,7 @@ 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" @@ -15097,11 +15119,9 @@ 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%&. @@ -15428,11 +15448,9 @@ 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. @@ -15451,14 +15469,12 @@ 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 @@ -15550,7 +15566,6 @@ 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. @@ -15560,7 +15575,6 @@ 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 @@ -15659,10 +15673,8 @@ 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" @@ -16626,7 +16638,6 @@ 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. @@ -16641,7 +16652,6 @@ to Exim. If the Exim command line uses a &%-oX%& option and does not use &%-oP%& then a notifier socket is not created. -.wen .option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation" @@ -16953,6 +16963,17 @@ 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%&" @@ -17574,12 +17595,10 @@ 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 @@ -17762,41 +17781,46 @@ See section &<>& for more details. This option is available when Exim is compiled with SPF support. See section &<>& for more details. -.new .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 following placeholders (along with Exim variables) are allowed -in the template (this list is compiled from the libspf2 sources): +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 -&*L*&: Envelope sender's local part. +&*%_*&: A space. +.next +&*%{L}*&: Envelope sender's local part. .next -&*S*&: Envelope sender. +&*%{S}*&: Envelope sender. .next -&*O*&: Envelope sender's domain. +&*%{O}*&: Envelope sender's domain. .next -&*D*&: Current(?) domain. +&*%{D}*&: Current(?) domain. .next -&*I*&: SMTP client Ip. +&*%{I}*&: SMTP client Ip. .next -&*C*&: SMTP client pretty IP. +&*%{C}*&: SMTP client pretty IP. .next -&*T*&: Epoch time (UTC). +&*%{T}*&: Epoch time (UTC). .next -&*P*&: SMTP client domain name. +&*%{P}*&: SMTP client domain name. .next -&*V*&: IP version. +&*%{V}*&: IP version. .next -&*H*&: EHLO/HELO domain. +&*%{H}*&: EHLO/HELO domain. .next -&*R*&: Receiving domain. +&*%{R}*&: Receiving domain. .endlist The capitalized placeholders do proper URL encoding, if you use them -lowercased, no encoding takes place. A note on using Exim variables: As -currenty the SPF library is initialized already during the EHLO phase, -the amount of variables available for expansion is quite limited. -.wen +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 @@ -18320,6 +18344,14 @@ 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" @@ -18516,11 +18548,9 @@ 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%&. @@ -19006,9 +19036,7 @@ 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 @@ -19121,11 +19149,9 @@ 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$&. -.wen When an address is being verified, &%local_part_prefix%& affects only the behaviour of the router. If the callout feature of verification is in use, this @@ -20960,7 +20986,6 @@ is not the case when the file contains syntactically valid items that happen to yield empty addresses, for example, items containing only RFC 2822 address comments. -.new .cindex "tainted data" "in filenames" .cindex redirect "tainted data" Tainted data may not be used for a filename. @@ -20971,7 +20996,6 @@ as they are provided by a potential attacker. In the examples above, &$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$&). -.wen @@ -21198,11 +21222,9 @@ It must be given as .code list1: :include:/opt/lists/list1 .endd -.new .cindex "tainted data" "in filenames" .cindex redirect "tainted data" Tainted data may not be used for a filename. -.wen .next .cindex "address redirection" "to black hole" .cindex "delivery" "discard" @@ -22211,9 +22233,7 @@ Each list item is separately expanded. If the result of the expansion is an empty string, or if the expansion is forced to fail, no action is taken. Other expansion failures are treated as errors and cause the delivery to be deferred. -.new If an item ends in *, it will match any header with the given prefix. -.wen Matching headers are omitted from the message as it is transported, as described in section &<>&. Header removal can also be specified by @@ -22768,14 +22788,12 @@ If &%file%& or &%directory%& is set for a delivery from a redirection, it is used to determine the file or directory name for the delivery. Normally, the contents of &$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$& cannot be used directly as a component of a path. It can however be used as the key for a lookup which returns a path (or component). -.wen .cindex "Sieve filter" "configuring &(appendfile)&" @@ -24213,11 +24231,9 @@ directories are also controllable. See chapter &<>& for details of the local delivery environment and chapter &<>& for a discussion of local delivery batching. -.new .cindex "tainted data" "in pipe command" .cindex pipe "tainted data" Tainted data may not be used for the command name. -.wen .section "Concurrent delivery" "SECID140" @@ -25359,9 +25375,7 @@ unauthenticated. See also &%hosts_require_auth%&, and chapter .cindex "RFC 3030" "CHUNKING" This option provides a list of servers to which, provided they announce CHUNKING support, Exim will attempt to use BDAT commands rather than DATA. -.new Unless DKIM signing is being done, -.wen BDAT will not be used in conjunction with a transport filter. .option hosts_try_dane smtp "host list&!!" * @@ -25459,6 +25473,20 @@ so can cause parallel connections to the same host if &%remote_max_parallel%& permits this. +.new +.option message_linelength_limit smtp integer 998 +.cindex "line length" limit +This option sets the maximum line length, in bytes, that the transport +will send. Any messages with lines exceeding the given value +will fail and a failure-DSN ("bounce") message will if possible be returned +to the sender. +The default value is that defined by the SMTP standards. + +It is generally wise to also check in the data ACL so that messages +received via SMTP can be refused without producing a bounce. +.wen + + .option multi_domain smtp boolean&!! true .vindex "&$domain$&" When this option is set, the &(smtp)& transport can handle a number of @@ -25640,6 +25668,14 @@ is used in different ways by OpenSSL and GnuTLS (see sections ciphers is a preference order. +.new +.option tls_resumption_hosts smtp "host list&!!" unset +.cindex TLS resumption +This option controls which connections to use the TLS resumption feature. +See &<>& for details. +.wen + + .option tls_sni smtp string&!! unset .cindex "TLS" "Server Name Indication" @@ -27872,7 +27908,6 @@ connection, a client certificate has been verified, the &"valid-client-cert"& option is passed. When authentication succeeds, the identity of the user who authenticated is placed in &$auth1$&. -.new The Dovecot configuration to match the above wil look something like: .code @@ -27892,7 +27927,6 @@ conf.d/10-auth.conf :- auth_mechanisms = plain login ntlm .endd -.wen .ecindex IIDdcotauth1 .ecindex IIDdcotauth2 @@ -27919,7 +27953,6 @@ scale to handle future authentication mechanisms, so no guarantee can be made that any particular new authentication mechanism will be supported without code changes in Exim. -.new The library is expected to add support in an upcoming realease for the SCRAM-SHA-256 method. The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined @@ -27943,9 +27976,7 @@ the password to be used, in clear. .option client_username gsasl string&!! unset This option is exapanded before use, and should result in the account name to be used. -.wen -.new .option client_spassword gsasl string&!! unset If a SCRAM mechanism is being used and this option is set it is used in preference to &%client_password%&. @@ -27954,7 +27985,6 @@ a 40 (for SHA-1) or 64 (for SHA-256) character string with the PBKDF2-prepared password, hex-encoded. Note that this value will depend on the salt and iteration-count supplied by the server. -.wen @@ -27972,12 +28002,10 @@ This should have meant that certificate identity and verification becomes a non-issue, as a man-in-the-middle attack will cause the correct client and server to see different identifiers and authentication will fail. -.new This is only usable by mechanisms which support "channel binding"; at time of writing, that's the SCRAM family. When using this feature the "-PLUS" variants of the method names need to be used. -.wen This defaults off to ensure smooth upgrade across Exim releases, in case this option causes some clients to start failing. Some future release @@ -28033,7 +28061,6 @@ Some mechanisms will use this data. .option server_scram_iter gsasl string&!! 4096 This option provides data for the SCRAM family of mechanisms. -.new The &$auth1$&, &$auth2$& and &$auth3$& variables are available when this option is expanded. @@ -28044,21 +28071,17 @@ a compute cost factor imposed on the client either the iteration count or the salt). A minimum value of 4096 is required by the standards for all current SCRAM mechanism variants. -.wen .option server_scram_salt gsasl string&!! unset This option provides data for the SCRAM family of mechanisms. -.new The &$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 @@ -28084,7 +28107,6 @@ 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`& @@ -29470,6 +29492,100 @@ 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 @@ -31099,7 +31215,6 @@ 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%&" @@ -31124,7 +31239,6 @@ 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" @@ -32592,6 +32706,15 @@ 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" @@ -32625,6 +32748,9 @@ 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 @@ -32954,6 +33080,38 @@ 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 @@ -34271,10 +34429,8 @@ 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 @@ -34955,7 +35111,6 @@ 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. @@ -34964,7 +35119,6 @@ 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 @@ -37078,13 +37232,11 @@ 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%& @@ -38089,6 +38241,7 @@ 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 @@ -38490,6 +38643,14 @@ 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" &%tls_sni%&: When a message is received over an encrypted connection, and @@ -39035,6 +39196,10 @@ 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 @@ -40448,8 +40613,8 @@ 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" @@ -40654,9 +40819,7 @@ 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 @@ -40907,10 +41070,8 @@ 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 @@ -41083,10 +41244,8 @@ variables: .vindex &%spf_smtp_comment_template%& This contains a string that can be used in a SMTP response to the calling party. Useful for "fail". -.new The string is generated by the SPF library from the template configured in the main config option &%spf_smtp_comment_template%&. -.wen .endlist @@ -41147,6 +41306,108 @@ 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} {$original_domain}} +.endd + + +.wen + + + .section DMARC SECDMARC .cindex DMARC verification @@ -41181,10 +41442,8 @@ during domain parsing. Maintained by Mozilla, the most current version can be downloaded from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat). See also the util/renew-opendmarc-tlds.sh script. -.new The default for the option is unset. If not set, DMARC processing is disabled. -.wen The &%dmarc_history_file%& option, if set @@ -41713,9 +41972,7 @@ Events have names which correspond to the point in process at which they fire. The name is placed in the variable &$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