X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/1ae904d586ae0d05bfebf613698d1cb0a25703ab..7482553d06b156505e38b4cb1b72324bcfb62b37:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index 0c5f633fe..cc5198ac5 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 "4.96" +.set previousversion "4.98" .include ./local_params .set ACL "access control lists (ACLs)" @@ -54,7 +54,7 @@ .set drivernamemax "64" .macro copyyear -2022 +2024 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -76,6 +76,16 @@ . --- table with four columns. For cases when the option name is given with . --- a space, so that it can be split, a fifth argument is used for the . --- index entry. +. --- Also one for multiple option def headings be grouped in a single +. --- table (but without the split capability). + +.macro otable +.itable all 0 0 4 8* left 6* center 6* center 6* right +.endmacro + +.macro orow +.row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&" +.endmacro .macro option .arg 5 @@ -84,8 +94,19 @@ .arg -5 .oindex "&%$1%&" .endarg -.itable all 0 0 4 8* left 6* center 6* center 6* right -.row "&%$1%&" "Use: &'$2'&" "Type: &'$3'&" "Default: &'$4'&" +.otable +.orow "$1" "$2" "$3" "$4" +.endtable +.endmacro + +.macro options +.eacharg +.oindex "&%$+1%&" +.endeach 4 +.otable +.eacharg +.orow "$+1" "$+2" "$+3" "$+4" +.endeach 4 .endtable .endmacro @@ -443,10 +464,11 @@ Please do not ask for configuration help in the bug-tracker. The following Exim mailing lists exist: .table2 140pt -.row &'exim-announce@exim.org'& "Moderated, low volume announcements list" -.row &'exim-users@exim.org'& "General discussion list" -.row &'exim-dev@exim.org'& "Discussion of bugs, enhancements, etc." -.row &'exim-cvs@exim.org'& "Automated commit messages from the VCS" +.row &'exim-announce@lists.exim.org'& "Moderated, low volume announcements list" +.row &'exim-users@lists.exim.org'& "General discussion list" +.row &'exim-users-de@lists.exim.org'& "General discussion list in German language" +.row &'exim-dev@lists.exim.org'& "Discussion of bugs, enhancements, etc." +.row &'exim-cvs@lists.exim.org'& "Automated commit messages from the VCS" .endtable You can subscribe to these lists, change your existing subscriptions, and view @@ -948,9 +970,10 @@ User filters are run as part of the routing process, described below. .cindex "base36" .cindex "Darwin" .cindex "Cygwin" -Every message handled by Exim is given a &'message id'& which is sixteen +.cindex "exim_msgdate" +Every message handled by Exim is given a &'message id'& which is 23 characters long. It is divided into three parts, separated by hyphens, for -example &`16VDhn-0001bo-D3`&. Each part is a sequence of letters and digits, +example &`16VDhn-000000001bo-D342`&. Each part is a sequence of letters and digits, normally encoding numbers in base 62. However, in the Darwin operating system (Mac OS X) and when Exim is compiled to run under Cygwin, base 36 (avoiding the use of lower case letters) is used instead, because the message @@ -971,20 +994,24 @@ started to be received, to a granularity of one second. That is, this field contains the number of seconds since the start of the epoch (the normal Unix way of representing the date and time of day). .next -After the first hyphen, the next six characters are the id of the process that -received the message. +After the first hyphen, the next +eleven +characters are the id of the process that received the message. .next -There are two different possibilities for the final two characters: +There are two different possibilities for the final four characters: .olist .oindex "&%localhost_number%&" If &%localhost_number%& is not set, this value is the fractional part of the -time of reception, normally in units of 1/2000 of a second, but for systems +time of reception, normally in units of +microseconds. +but for systems that must use base 36 instead of base 62 (because of case-insensitive file -systems), the units are 1/1000 of a second. +systems), the units are +2 us. .next -If &%localhost_number%& is set, it is multiplied by 200 (100) and added to -the fractional part of the time, which in this case is in units of 1/200 -(1/100) of a second. +If &%localhost_number%& is set, it is multiplied by +500000 (250000) and added to +the fractional part of the time, which in this case is in units of 2 us (4 us). .endlist .endlist @@ -994,6 +1021,10 @@ received by the same process, or by another process with the same (re-used) pid, it is guaranteed that the time will be different. In most cases, the clock will already have ticked while the message was being received. +The exim_msgdate utility (see section &<>&) can be +used to display the date, and optionally the process id, of an Exim +Message ID. + .section "Receiving mail" "SECID13" .cindex "receiving mail" @@ -1733,6 +1764,12 @@ distributors have chosen to bundle different libraries with their packaged versions. However, the more recent releases seem to have standardized on the Berkeley DB library. +.new +Ownership of the Berkeley DB library has moved to a major corporation; +development seems to have stalled and documentation is not freely available. +This is probably not tenable for the long term use by Exim. +.wen + Different DBM libraries have different conventions for naming the files they use. When a program opens a file called &_dbmfile_&, there are several possibilities: @@ -1773,6 +1810,9 @@ suited to Exim's usage model. Yet another DBM library, called &'tdb'&, is available from &url(https://sourceforge.net/projects/tdb/files/). It has its own interface, and also operates on a single file. +.next +It is possible to use sqlite3 (&url(https://www.sqlite.org/index.html)) +for the DBM library. .endlist .cindex "USE_DB" @@ -1784,8 +1824,9 @@ USE_DB in an appropriate configuration file (typically .code USE_DB=yes .endd -Similarly, for gdbm you set USE_GDBM, and for tdb you set USE_TDB. An -error is diagnosed if you set more than one of these. +Similarly, for gdbm you set USE_GDBM, for tdb you set USE_TDB, +and for sqlite3 you set USE_SQLITE. +An error is diagnosed if you set more than one of these. You can set USE_NDBM if needed to override an operating system default. At the lowest level, the build-time configuration sets none of these options, @@ -1801,6 +1842,7 @@ in one of these lines: .code DBMLIB = -ldb DBMLIB = -ltdb +DBMLIB = -lsqlite3 DBMLIB = -lgdbm -lgdbm_compat .endd The last of those was for a Linux having GDBM provide emulated NDBM facilities. @@ -1816,6 +1858,17 @@ DBMLIB=/usr/local/lib/db-4.1/libdb.a There is further detailed discussion about the various DBM libraries in the file &_doc/dbm.discuss.txt_& in the Exim distribution. +.new +When moving from one DBM library to another, +for the hints databases it suffices to just remove all the files in the +directory named &"db/"& under the spool directory. +This is because hints are only for optimisation and will be rebuilt +during normal operations. +Non-hints DBM databases (used by &"dbm"& lookups in the configuration) +will need individual rebuilds for the new DBM library. +This is not done automatically +.wen + .section "Pre-building configuration" "SECID25" @@ -2810,6 +2863,12 @@ of Exim is installed. It is not necessary to do this when other files that are referenced from the configuration (for example, alias files) are changed, because these are reread each time they are used. +Either a SIGTERM or a SIGINT signal should be used to cause the daemon +to cleanly shut down. +Subprocesses handling recceiving or delivering messages, +or for scanning the queue, +will not be affected by the termination of the daemon process. + .cmdopt -bdf This option has the same effect as &%-bd%& except that it never disconnects from the controlling terminal, even when no debugging is specified. @@ -2846,11 +2905,12 @@ defined and macros will be expanded. Because macros in the config file are often used for secrets, those are only available to admin users. -.new The word &"set"& at the start of a line, followed by a single space, is recognised specially as defining a value for a variable. +.cindex "tainted data" "expansion testing" +If the sequence &",t"& is inserted before the space, +the value is marked as tainted. The syntax is otherwise the same as the ACL modifier &"set ="&. -.wen .cmdopt -bem <&'filename'&> .cindex "testing" "string expansion" @@ -3060,7 +3120,7 @@ options, as appropriate. The &%-bnq%& option (see below) provides a way of suppressing this for special cases. Policy checks on the contents of local messages can be enforced by means of -the non-SMTP ACL. See chapter &<>& for details. +the non-SMTP ACL. See section &<>& for details. .cindex "return code" "for &%-bm%&" The return code is zero if the message is successfully accepted. Otherwise, the @@ -3258,6 +3318,12 @@ to the standard output. It is restricted to admin users, unless &%queue_list_requires_admin%& is set false. +.cmdopt -bpi +.cindex queue "list of message IDs" +This option operates like &%-bp%&, but only outputs message ids +(one per line). + + .cmdopt -bpr This option operates like &%-bp%&, but the output is not sorted into chronological order of message arrival. This can speed it up when there are @@ -3267,6 +3333,9 @@ going to be post-processed in a way that doesn't need the sorting. .cmdopt -bpra This option is a combination of &%-bpr%& and &%-bpa%&. +.cmdopt -bpri +This option is a combination of &%-bpr%& and &%-bpi%&. + .cmdopt -bpru This option is a combination of &%-bpr%& and &%-bpu%&. @@ -3327,7 +3396,7 @@ dots doubled), terminated by a line containing just a single dot. An error is provoked if the terminating dot is missing. A further message may then follow. As for other local message submissions, the contents of incoming batch SMTP -messages can be checked using the non-SMTP ACL (see chapter &<>&). +messages can be checked using the non-SMTP ACL (see section &<>&). Unqualified addresses are automatically qualified using &%qualify_domain%& and &%qualify_recipient%&, as appropriate, unless the &%-bnq%& option is used. @@ -3967,7 +4036,7 @@ user. This option requests Exim to give up trying to deliver the listed messages, including any that are frozen. However, if any of the messages are active, their status is not altered. For non-bounce messages, a delivery error message -is sent to the sender, containing the text &"cancelled by administrator"&. +is sent to the sender. Bounce messages are just discarded. This option can be used only by an admin user. @@ -4397,13 +4466,17 @@ 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. +If this option is given then the socket will not be created. This is required +if the system is running multiple daemons, in which case it should +be used on all. +The features supported by the socket will not be available in such cases. The socket is currently used for .ilist fast ramp-up of queue runner processes .next +caching compiled regexes +.next obtaining a current queue size .endlist @@ -4489,22 +4562,30 @@ every domain. Addresses are routed, local deliveries happen, but no remote transports are run. Performance will be best if the &%queue_run_in_order%& option is false. -If that is so and the &%queue_fast_ramp%& option is true then -in the first phase of the run, +If that is so and +the &%queue_fast_ramp%& option is true +and a daemon-notifier socket is available +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 -is updated, as if delivery to those hosts had been deferred. After this is -complete, a second, normal queue scan happens, with routing and delivery taking -place as normal. Messages that are routed to the same host should mostly be +is updated, as if delivery to those hosts had been deferred. + +After the first queue scan complete, +a second, normal queue scan is done, with routing and delivery taking +place as normal. +Messages that are routed to the same host should mostly be delivered down a single SMTP .cindex "SMTP" "passed connection" .cindex "SMTP" "multiple deliveries" .cindex "multiple SMTP deliveries" connection because of the hints that were set up during the first queue scan. -This option may be useful for hosts that are connected to the Internet + +Two-phase queue runs should be used on systems which, even intermittently, +have a large queue (such as mailing-list operators). +They may also be useful for hosts that are connected to the Internet intermittently. .vitem &%-q[q]i...%& @@ -4591,6 +4672,13 @@ combined daemon at system boot time is to use a command such as Such a daemon listens for incoming SMTP calls, and also starts a queue runner process every 30 minutes. +.cindex "named queues" "queue runners" +It is possible to set up runners for multiple named queues within one daemon, +For example: +.code +exim -qGhipri/2m -q10m -qqGmailinglist/1h +.endd + When a daemon is started by &%-q%& with a time value, but without &%-bd%&, no pid file is written unless one is explicitly requested by the &%-oP%& option. @@ -4646,7 +4734,7 @@ all selected messages, not just the first; frozen messages are included when The &%-R%& option makes it straightforward to initiate delivery of all messages to a given domain after a host has been down for some time. When the SMTP -command ETRN is accepted by its ACL (see chapter &<>&), its default +command ETRN is accepted by its ACL (see section &<>&), its default effect is to run Exim with the &%-R%& option, but it can be configured to run an arbitrary command instead. @@ -5103,6 +5191,10 @@ The following classes of macros are defined: &` _DRIVER_ROUTER_* `& router drivers &` _DRIVER_TRANSPORT_* `& transport drivers &` _DRIVER_AUTHENTICATOR_* `& authenticator drivers +&` _EXP_COND_* `& expansion conditions +&` _EXP_ITEM_* `& expansion items +&` _EXP_OP_* `& expansion operators +&` _EXP_VAR_* `& expansion variables &` _LOG_* `& log_selector values &` _OPT_MAIN_* `& main config options &` _OPT_ROUTERS_* `& generic router options @@ -6602,7 +6694,7 @@ file that is searched could contain lines like this: When the lookup succeeds, the result of the expansion is a list of domains (and possibly other types of item that are allowed in domain lists). .cindex "tainted data" "de-tainting" -.cindex "de-tainting" "using a lookup expansion"" +.cindex "de-tainting" "using a lookup expansion" The result of the expansion is not tainted. .next @@ -6671,8 +6763,14 @@ version of the lookup key. The &'query-style'& type accepts a generalized database query. No particular key value is assumed by Exim for query-style lookups. You can use whichever Exim variables you need to construct the database query. + +For the string-expansion kind of lookups, the query is given in the first +bracketed argument of the &${lookup ...}$& expansion. +For the list-argument kind of lookup the query is given by the remainder of the +list item after the first semicolon. + .cindex "tainted data" "quoting for lookups" -If tainted data is used in the query then it should be quuted by +If tainted data is used in the query then it should be quoted by using the &*${quote_*&<&'lookup-type'&>&*:*&<&'string'&>&*}*& expansion operator appropriate for the lookup. .endlist @@ -6767,7 +6865,8 @@ by default, but has an option to omit them (see section &<>&). .cindex "dsearch lookup type" The given file must be an absolute 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. +Unless the options (below) permit a path, +the key may not contain any forward slash characters. If &[lstat()]& succeeds then so does the lookup. .cindex "tainted data" "dsearch result" The result is regarded as untainted. @@ -6776,7 +6875,7 @@ Options for the lookup can be given by appending them after the word "dsearch", separated by a comma. Options, if present, are a comma-separated list having each element starting with a tag name and an equals. -Two options are supported, for the return value and for filtering match +Three options are supported, for the return value and for filtering match candidates. The "ret" option requests an alternate result value of the entire path for the entry. Example: @@ -6784,6 +6883,7 @@ the entire path for the entry. Example: ${lookup {passwd} dsearch,ret=full {/etc}} .endd The default result is just the requested entry. + The "filter" option requests that only directory entries of a given type are matched. The match value is one of "file", "dir" or "subdir" (the latter not matching "." or ".."). Example: @@ -6793,6 +6893,14 @@ ${lookup {passwd} dsearch,filter=file {/etc}} The default matching is for any entry type, including directories and symlinks. +The "key" option relaxes the restriction that only a simple path component can +be searched for, to permit a sequence of path components. Example: +.code +${lookup {foo/bar} dsearch,key=path {/etc}} +.endd +If this option is used, a ".." component in the key is specifically disallowed. +The default operation is that the key may only be a single path component. + An example of how this lookup can be used to support virtual domains is given in section &<>&. @@ -6822,8 +6930,8 @@ key is found. The first key that matches is used; there is no attempt to find a lookup types support only literal keys. &*Warning 2*&: In a host list, you must always use &(net-iplsearch)& so that -the implicit key is the host's IP address rather than its name (see section -&<>&). +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 @@ -7079,7 +7187,6 @@ not likely to be useful in normal operation. .subsection whoson .cindex "whoson lookup type" .cindex "lookup" "whoson" -. --- still http:-only, 2018-09-07 &'Whoson'& (&url(http://whoson.sourceforge.net)) is a protocol that allows a server to check whether a particular (dynamically allocated) IP address is currently allocated to a known (trusted) user and, optionally, to @@ -7262,6 +7369,11 @@ dot-separated components; a key such as &`*fict.example`& in a database file is useless, because the asterisk in a partial matching subject key is always followed by a dot. +When the lookup is done from a string-expansion, +the variables &$1$& and &$2$& contain the wild and non-wild parts of the key +during the expansion of the replacement text. +They return to their previous values at the end of the lookup item. + @@ -7312,10 +7424,13 @@ of the following form is provided: .code ${quote_:} .endd -For example, the safest way to write the NIS+ query is +For example, the way to write the NIS+ query is .code [name="${quote_nisplus:$local_part}"] .endd +.cindex "tainted data" "in lookups" +&*All*& tainted data used in a query-style lookup must be quoted +using a mechanism appropriate for the lookup type. See chapter &<>& for full coverage of string expansions. The quote operator can be used for all lookup types, but has no effect for single-key lookups, since no quoting is ever needed in their key strings. @@ -7800,7 +7915,8 @@ connection timeout (the system timeout is used), no user or password, no limit on the number of entries returned, and no time limit on queries. When a DN is quoted in the USER= setting for LDAP authentication, Exim -removes any URL quoting that it may contain before passing it LDAP. Apparently +removes any URL quoting that it may contain before passing it to the LDAP library. +Apparently some libraries do this for themselves, but some do not. Removing the URL quoting has two advantages: @@ -8074,13 +8190,18 @@ option, you can still update it by a query of this form: ${lookup pgsql,servers=master/db/name/pw {UPDATE ...} } .endd -An older syntax places the servers specification before the query, +A now-deprecated syntax places the servers specification before the query, semicolon separated: .code ${lookup mysql{servers=master; UPDATE ...} } .endd -The new version avoids potential issues with tainted -arguments in the query, for explicit expansion. +The new version avoids issues with tainted +arguments explicitly expanded as part of the query. +The entire string within the braces becomes tainted, +including the server sepcification - which is not permissible. +If the older sytax is used, a warning message will be logged. +This syntax will be removed in a future release. + &*Note*&: server specifications in list-style lookups are still problematic. @@ -8108,6 +8229,9 @@ or delete command), the result of the lookup is the number of rows affected. anything (for example, setting a field to the value it already has), the result is zero because no rows are affected. +To get an encryted connection, use a Mysql option file with the required +parameters for the connection. + .subsection "Special PostgreSQL features" SECID74 PostgreSQL lookups can also use Unix domain socket connections to the database. @@ -8136,7 +8260,7 @@ daemon as in the other SQL databases. .oindex &%sqlite_dbfile%& There are two ways of specifying the file. -The first is is by using the &%sqlite_dbfile%& main option. +The first 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, @@ -8257,6 +8381,9 @@ type of match and is given below as the &*value*& information. .section "Expansion of lists" "SECTlistexpand" .cindex "expansion" "of lists" Each list is expanded as a single string before it is used. +.cindex "tainted data" tracking +&*Note*&: As a result, if any componend was tainted then the +entire result string becomes tainted. &'Exception: the router headers_remove option, where list-item splitting is done before string-expansion.'& @@ -9138,8 +9265,9 @@ is not used. &*Reminder*&: With this kind of pattern, you must have host &'names'& as keys in the file, not IP addresses. If you want to do lookups based on IP -addresses, you must precede the search type with &"net-"& (see section -&<>&). There is, however, no reason why you could not use +addresses, you must precede the search type with &"net-"& +(see section &<>&). +There is, however, no reason why you could not use two items in the same list, one doing an address lookup and one doing a name lookup, both using the same file. @@ -9452,6 +9580,9 @@ start of a portion of the string that is interpreted and replaced as described below in section &<>& onwards. Backslash is used as an escape character, as described in the following section. +.cindex "tainted data" tracking +If any porttion of the result string is tainted, the entire result is. + Whether a string is expanded depends upon the context. Usually this is solely dependent upon the option for which a value is sought; in this documentation, options for which string expansion is performed are marked with † after @@ -9524,7 +9655,6 @@ value. Nevertheless the &%-be%& option can be useful for checking out file and database lookups, and the use of expansion operators such as &%sg%&, &%substr%& and &%nhash%&. -.new When reading lines from the standard input, macros can be defined and ACL variables can be set. For example: @@ -9533,7 +9663,6 @@ MY_MACRO = foo set acl_m_myvar = bar .endd Such macros and variables can then be used in later input lines. -.wen Exim gives up its root privilege when it is called with the &%-be%& option, and instead runs under the uid and gid it was called with, to prevent users from @@ -9649,7 +9778,8 @@ Example use (as an ACL modifier): .code add_header = :at_start:${authresults {$primary_hostname}} .endd -This is safe even if no authentication results are available. +This is safe even if no authentication results are available +and would generally be placed in the DATA ACL. .vitem "&*${certextract{*&<&'field'&>&*}{*&<&'certificate'&>&*}&&& @@ -9907,8 +10037,10 @@ leading and trailing quotes are removed from the returned value. After expansion, <&'string'&> is interpreted as a list, colon-separated by default, but the separator can be changed in the usual way (&<>&). For each item -in this list, its value is place in &$item$&, and then the condition is -evaluated. If the condition is true, &$item$& is added to the output as an +in this list, its value is placed in &$item$&, and then the condition is +evaluated. +Any modification of &$value$& by this evaluation is discarded. +If the condition is true, &$item$& is added to the output as an item in a new list; if the condition is false, the item is discarded. The separator used for the output list is the same as the one used for the input, but a separator setting is not included in the output. For example: @@ -9916,7 +10048,8 @@ input, but a separator setting is not included in the output. For example: ${filter{a:b:c}{!eq{$item}{b}}} .endd yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored -to what it was before. See also the &%map%& and &%reduce%& expansion items. +to what it was before. +See also the &%map%& and &%reduce%& expansion items. .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& @@ -10435,6 +10568,11 @@ Defines whether or not a write-shutdown is done on the connection after sending the request. Values are &"yes"& (the default) or &"no"& (preferred, eg. by some webservers). +.next +&*sni*& +Controls the use of Server Name Identification on the connection. +Any nonempty value will be the SNI sent; TLS will be forced. + .next &*tls*& Controls the use of TLS on the connection. @@ -10507,20 +10645,32 @@ At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are restored to what they were before. See also the &%filter%& and &%map%& expansion items. +. A bit of a special-case logic error in writing an expansion; +. probably not worth including in the mainline of documentation. +. If only we had footnotes (the html output variant is the problem). +. +. .new +. &*Note*&: if an &'expansion condition'& is used in <&'string3'&> +. and that condition modifies &$value$&, +. then the string expansions dependent on the condition cannot use +. the &$value$& of the reduce iteration. +. .wen + .vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*& This item inserts &"raw"& header lines. It is described with the &%header%& expansion item in section &<>& above. -.vitem "&*${run <&'options'&> {*&<&'command&~arg&~list'&>&*}{*&<&'string1'&>&*}&&& +.vitem "&*${run<&'options'&> {*&<&'command&~string'&>&*}{*&<&'string1'&>&*}&&& {*&<&'string2'&>&*}}*&" .cindex "expansion" "running a command" .cindex "&%run%& expansion item" This item runs an external command, as a subprocess. -One option is supported after the word &'run'&, comma-separated. +One option is supported after the word &'run'&, comma-separated +and without whitespace. If the option &'preexpand'& is not used, -the command string is split into individual arguments by spaces -and then each argument is expanded. +the command string before expansion is split into individual arguments by spaces +and then each argument is separately expanded. Then the command is run in a separate process, but under the same uid and gid. As in other command executions from Exim, a shell is not used by default. If the command requires @@ -10532,9 +10682,9 @@ potential attacker; a careful assessment for security vulnerabilities should be done. If the option &'preexpand'& is used, -the command and its arguments are first expanded as one string. The result is -split apart into individual arguments by spaces, and then the command is run -as above. +the command string is first expanded as a whole. +The expansion result is split apart into individual arguments by spaces, +and then the command is run as above. Since the arguments are split by spaces, when there is a variable expansion which has an empty result, it will cause the situation that the argument will simply be omitted when the program is actually executed by Exim. If the @@ -10576,6 +10726,7 @@ shell must be invoked directly, such as with: .code ${run{/bin/bash -c "/usr/bin/id >/tmp/id"}{yes}{yes}} .endd +Note that &$value$& will not persist beyond the reception of a single message. .vindex "&$runrc$&" The return code from the command is put in the variable &$runrc$&, and this @@ -10998,6 +11149,22 @@ abbreviation &%h%& can be used when &%hash%& is used as an operator. +.vitem &*${headerwrap_*&<&'cols'&>&*_*&<&'limit'&>&*:*&<&'string'&>&*}*& +.cindex header "wrapping operator" +.cindex expansion "header wrapping" +This operator line-wraps its argument in a way useful for headers. +The &'cols'& value gives the column number to wrap after, +the &'limit'& gives a limit number of result characters to truncate at. +Either just the &'limit'& and the preceding underbar, or both, can be omitted; +the defaults are 80 and 998. +Wrapping will be inserted at a space if possible before the +column number is reached. +Whitespace at a chosen wrap point is removed. +A line-wrap consists of a newline followed by a tab, +and the tab is counted as 8 columns. + + + .vitem &*${hex2b64:*&<&'hexstring'&>&*}*& .cindex "base64 encoding" "conversion from hex" .cindex "expansion" "hex to base64" @@ -11431,6 +11598,17 @@ literal question mark). .cindex "&%utf8_localpart_from_alabel%& expansion item" These convert EAI mail name components between UTF-8 and a-label forms. For information on internationalisation support see &<>&. + + +.vitem &*${xtextd:*&<&'string'&>&*}*& +.cindex "text forcing in strings" +.cindex "string" "xtext decoding" +.cindex "xtext" +.cindex "&%xtextd%& expansion item" +This performs xtext decoding of the string (per RFC 3461 section 4). + + + .endlist @@ -11659,6 +11837,7 @@ Consider using a dsearch lookup. .cindex "first delivery" .cindex "expansion" "first delivery test" .cindex "&%first_delivery%& expansion condition" +.cindex retry condition This condition, which has no data, is true during a message's first delivery attempt. It is false during any subsequent delivery attempts. @@ -11686,10 +11865,11 @@ all items in the list, the overall condition is true. .endlist Note that negation of &*forany*& means that the condition must be false for all items for the overall condition to succeed, and negation of &*forall*& means -that the condition must be false for at least one item. In this example, the -list separator is changed to a comma: +that the condition must be false for at least one item. + +Example: .code -${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}} +${if forany{$recipients_list}{match{$item}{^user3@}}{yes}{no}} .endd The value of &$item$& is saved and restored while &%forany%& or &%forall%& is being processed, to enable these expansion items to be nested. @@ -11743,8 +11923,8 @@ Case and collation order are defined per the system C locale. SRS decode. See SECT &<>& for details. -.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&& - &*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& +.vitem &*inlist&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*& &&& + &*inlisti&~{*&<&'subject'&>&*}{*&<&'list'&>&*}*& .cindex "string" "comparison" .cindex "list" "iterative conditions" Both strings are expanded; the second string is treated as a list of simple @@ -11918,7 +12098,8 @@ where the first item in the list is the empty string. .next The item @[] matches any of the local host's interface addresses. .next -Single-key lookups are assumed to be like &"net-"& style lookups in host lists, +Single-key lookups are assumed to be like &"net-"& style lookups in host lists +(see section &<>&), even if &`net-`& is not specified. There is never any attempt to turn the IP address into a host name. The most common type of linear search for &*match_ip*& is likely to be &*iplsearch*&, in which the file can contain CIDR @@ -11944,6 +12125,10 @@ Exim was built with the EXPAND_LISTMATCH_RHS option. Consult section &<>& for further details of these patterns. +The variable &$value$& will be set for a successful match and can be +used in the success clause of an &%if%& expansion item using the condition. +Any previous &$value$& is restored after the if. + .vitem &*match_local_part&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& .cindex "domain list" "in expansion condition" .cindex "address list" "in expansion condition" @@ -13288,10 +13473,18 @@ The main use of this variable is expected to be to distinguish between rejections of MAIL and rejections of RCPT. .tvar &$recipients$& -This variable contains a list of envelope recipients for a message. A comma and -a space separate the addresses in the replacement text. However, the variable -is not generally available, to prevent exposure of Bcc recipients in -unprivileged users' filter files. You can use &$recipients$& only in these +.tvar &$recipients_list$& +These variables both contain the envelope recipients for a message. + +The first uses a comma and a space separate the addresses in the replacement text. +&*Note*&: an address can legitimately contain a comma; +this variable is not intended for further processing. + +The second is a proper Exim list; colon-separated. + +However, the variables +are not generally available, to prevent exposure of Bcc recipients in +unprivileged users' filter files. You can use either of them only in these cases: .olist @@ -13355,7 +13548,8 @@ This is an obsolete name for &$bounce_return_size_limit$&. .cindex "router" "name" .cindex "name" "of router" .vindex "&$router_name$&" -During the running of a router this variable contains its name. +During the running of a router, or a transport called, +this variable contains the router name. .vitem &$runrc$& .cindex "return code" "from &%run%& expansion" @@ -13646,6 +13840,11 @@ there actually are, because many other connections may come and go while a single connection is being processed. When a child process terminates, the daemon decrements its copy of the variable. +.vitem &$smtp_notquit_reason$& +.vindex "&$smtp_notquit_reason$&" +When the not-QUIT ACL is running, this variable is set to a string +that indicates the reason for the termination of the SMTP connection. + .vitem "&$sn0$& &-- &$sn9$&" These variables are copies of the values of the &$n0$& &-- &$n9$& accumulators that were current at the end of the system filter file. This allows a system @@ -14661,6 +14860,7 @@ listed in more than one group. .row &%acl_smtp_rcpt%& "ACL for RCPT" .row &%acl_smtp_starttls%& "ACL for STARTTLS" .row &%acl_smtp_vrfy%& "ACL for VRFY" +.row &%acl_smtp_wellknown%& "ACL for WELLKNOWN" .row &%av_scanner%& "specify virus scanner" .row &%check_rfc2047_length%& "check length of RFC 2047 &""encoded &&& words""&" @@ -14821,11 +15021,13 @@ See also the &'Policy controls'& section above. .row &%dsn_advertise_hosts%& "advertise DSN extensions to these hosts" .row &%ignore_fromline_hosts%& "allow &""From ""& from these hosts" .row &%ignore_fromline_local%& "allow &""From ""& from local SMTP" +.row &%limits_advertise_hosts%& "advertise LIMITS to these hosts" .row &%pipelining_advertise_hosts%& "advertise pipelining to these hosts" .row &%pipelining_connect_advertise_hosts%& "advertise pipelining to these hosts" .row &%prdr_enable%& "advertise PRDR to all hosts" .row &%smtputf8_advertise_hosts%& "advertise SMTPUTF8 to these hosts" .row &%tls_advertise_hosts%& "advertise TLS to these hosts" +.row &%wellknown_advertise_hosts%& "advertise WELLKNOWN to these hosts" .endtable @@ -14949,7 +15151,7 @@ log_selector = +8bitmime .cindex "&ACL;" "for non-SMTP messages" .cindex "non-SMTP messages" "ACLs for" This option defines the ACL that is run when a non-SMTP message has been -read and is on the point of being accepted. See chapter &<>& for +read and is on the point of being accepted. See section &<>& for further details. .option acl_not_smtp_mime main string&!! unset @@ -14961,24 +15163,26 @@ SMTP messages. .cindex "&ACL;" "at start of non-SMTP message" .cindex "non-SMTP messages" "ACLs for" This option defines the ACL that is run before Exim starts reading a -non-SMTP message. See chapter &<>& for further details. +non-SMTP message. See section &<>& for further details. .option acl_smtp_auth main string&!! unset .cindex "&ACL;" "setting up for SMTP commands" .cindex "AUTH" "ACL for" This option defines the ACL that is run when an SMTP AUTH command is -received. See chapter &<>& for further details. +received. +See chapter &<>& for general information on ACLs, and chapter +&<>& for details of authentication. .option acl_smtp_connect main string&!! unset .cindex "&ACL;" "on SMTP connection" This option defines the ACL that is run when an SMTP connection is received. -See chapter &<>& for further details. +See section &<>& for further details. .option acl_smtp_data main string&!! unset .cindex "DATA" "ACL for" This option defines the ACL that is run after an SMTP DATA command has been processed and the message itself has been received, but before the final -acknowledgment is sent. See chapter &<>& for further details. +acknowledgment is sent. See section &<>& for further details. .option acl_smtp_data_prdr main string&!! accept .cindex "PRDR" "ACL for" @@ -14989,7 +15193,7 @@ This option defines the ACL that, if the PRDR feature has been negotiated, is run for each recipient after an SMTP DATA command has been processed and the message itself has been received, but before the -acknowledgment is sent. See chapter &<>& for further details. +acknowledgment is sent. See section &<>& for further details. .option acl_smtp_dkim main string&!! unset .cindex DKIM "ACL for" @@ -15000,8 +15204,11 @@ See section &<>& for further details. .option acl_smtp_etrn main string&!! unset .cindex "ETRN" "ACL for" +.cindex "ETRN" advertisement This option defines the ACL that is run when an SMTP ETRN command is -received. See chapter &<>& for further details. +received. +If no value is set then the ETRN facility is not advertised. +See chapter &<>& for further details. .option acl_smtp_expn main string&!! unset .cindex "EXPN" "ACL for" @@ -15012,7 +15219,7 @@ received. See chapter &<>& for further details. .cindex "EHLO" "ACL for" .cindex "HELO" "ACL for" This option defines the ACL that is run when an SMTP EHLO or HELO -command is received. See chapter &<>& for further details. +command is received. See section &<>& for further details. .option acl_smtp_mail main string&!! unset @@ -15023,7 +15230,8 @@ received. See chapter &<>& for further details. .option acl_smtp_mailauth main string&!! unset .cindex "AUTH" "on MAIL command" This option defines the ACL that is run when there is an AUTH parameter on -a MAIL command. See chapter &<>& for details of ACLs, and chapter +a MAIL command. +See chapter &<>& for general information on ACLs, and chapter &<>& for details of authentication. .option acl_smtp_mime main string&!! unset @@ -15036,7 +15244,7 @@ section &<>& for details. .cindex "not-QUIT, ACL for" This option defines the ACL that is run when an SMTP session ends without a QUIT command being received. -See chapter &<>& for further details. +See section &<>& for further details. .option acl_smtp_predata main string&!! unset This option defines the ACL that is run when an SMTP DATA command is @@ -15051,7 +15259,7 @@ received. See chapter &<>& for further details. .option acl_smtp_rcpt main string&!! unset .cindex "RCPT" "ACL for" This option defines the ACL that is run when an SMTP RCPT command is -received. See chapter &<>& for further details. +received. See section &<>& for further details. .option acl_smtp_starttls main string&!! unset .cindex "STARTTLS, ACL for" @@ -15063,6 +15271,11 @@ received. See chapter &<>& for further details. This option defines the ACL that is run when an SMTP VRFY command is received. See chapter &<>& for further details. +.option acl_smtp_wellknown main string&!! unset +.cindex "WELLKNOWN, ACL for" +This option defines the ACL that is run when an SMTP WELLKNOWN command is +received. See section &<>& for further details. + .option add_environment main "string list" empty .cindex "environment" "set values" This option adds individual environment variables that the @@ -15322,11 +15535,8 @@ $primary_hostname-$tod_epoch-testing See section &<>& for details of how this value is used. -.option check_log_inodes main integer 100 -See &%check_spool_space%& below. - - -.option check_log_space main integer 10M +.options check_log_inodes main integer 100 &&& + check_log_space main integer 10M See &%check_spool_space%& below. .oindex "&%check_rfc2047_length%&" @@ -15341,11 +15551,8 @@ of the RFC, generates overlong encoded words. If &%check_rfc2047_length%& is set false, Exim recognizes encoded words of any length. -.option check_spool_inodes main integer 100 -See &%check_spool_space%& below. - - -.option check_spool_space main integer 10M +.options check_spool_inodes main integer 100 &&& + check_spool_space main integer 10M .cindex "checking disk space" .cindex "disk space, checking" .cindex "spool directory" "checking space" @@ -15424,17 +15631,15 @@ This option specifies one or more default SMTP ports on which the Exim daemon listens. See chapter &<>& for details of how it is used. For backward compatibility, &%daemon_smtp_port%& (singular) is a synonym. -.option daemon_startup_retries main integer 9 +.options daemon_startup_retries main integer 9 &&& + daemon_startup_sleep main time 30s .cindex "daemon startup, retrying" -This option, along with &%daemon_startup_sleep%&, controls the retrying done by +These options control the retrying done by the daemon at startup when it cannot immediately bind a listening socket (typically because the socket is already in use): &%daemon_startup_retries%& defines the number of retries after the first failure, and &%daemon_startup_sleep%& defines the length of time to wait between retries. -.option daemon_startup_sleep main time 30s -See &%daemon_startup_retries%&. - .option delay_warning main "time list" 24h .cindex "warning of delay" .cindex "delay warning, specifying" @@ -15576,9 +15781,9 @@ 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 +.option dmarc_forensic_sender main string&!! unset &&& + dmarc_history_file main string unset &&& + dmarc_tld_file main string unset .cindex DMARC "main section options" These options control DMARC processing. See section &<>& for details. @@ -15597,7 +15802,10 @@ by a setting such as this: .code dns_again_means_nonexist = *.in-addr.arpa .endd -This option applies to all DNS lookups that Exim does. It also applies when the +This option applies to all DNS lookups that Exim does, +except for TLSA lookups (where knowing about such failures +is security-relevant). +It also applies when the &[gethostbyname()]& or &[getipnodebyname()]& functions give temporary errors, since these are most likely to be caused by DNS lookup problems. The &(dnslookup)& router has some options of its own for controlling what happens @@ -15937,6 +16145,7 @@ search the file multiple times for non-existent users, and also cause delay. .option freeze_tell main "string list, comma separated" unset .cindex "freezing messages" "sending a message when freezing" +.cindex "frozen messages" "sending a message when freezing" On encountering certain errors, or when configured to do so in a system filter, ACL, or special router, Exim freezes a message. This means that no further delivery attempts take place until an administrator thaws the message, or the @@ -15952,7 +16161,8 @@ log. If you configure freezing in a filter or ACL, you must arrange for any logging that you require. -.option gecos_name main string&!! unset +.options gecos_name main string&!! unset &&& + gecos_pattern main string unset .cindex "HP-UX" .cindex "&""gecos""& field, parsing" Some operating systems, notably HP-UX, use the &"gecos"& field in the system @@ -15977,9 +16187,6 @@ gecos_pattern = ([^,]*) gecos_name = $1 .endd -.option gecos_pattern main string unset -See &%gecos_name%& above. - .option gnutls_compat_mode main boolean unset This option controls whether GnuTLS is used in compatibility mode in an Exim @@ -16043,11 +16250,13 @@ set. .cindex "EHLO" "underscores in" .cindex "underscore in EHLO/HELO" This option can be set to a string of rogue characters that are permitted in -all EHLO and HELO names in addition to the standard letters, digits, -hyphens, and dots. If you really must allow underscores, you can set +non-ip-literal EHLO and HELO names in addition to the standard letters, digits, +hyphens, and dots. For examplem if you really must allow underscores, +you can set .code helo_allow_chars = _ .endd +This option does not apply to names that look like ip-literals. Note that the value is one string, not a list. @@ -16177,6 +16386,9 @@ This option is obsolete, and retained only for backward compatibility, because nowadays the ACL specified by &%acl_smtp_connect%& can also reject incoming connections immediately. +If the connection is on a TLS-on-connect port then the TCP connection is +just dropped. Otherwise, an SMTP error is sent first. + The ability to give an immediate rejection (either by this option or using an ACL) is provided for use in unusual cases. Many hosts will just try again, sometimes without much delay. Normally, it is better to use an ACL to reject @@ -16196,10 +16408,8 @@ local processes, you must create a host list with an empty item. For example: .code hosts_connection_nolog = : .endd -.new The hosts affected by this option also do not log "no MAIL in SMTP connection" lines, as may commonly be produced by a monitoring system. -.wen .option hosts_require_alpn main "host list&!!" unset @@ -16278,7 +16488,8 @@ dealing with other kinds of frozen message, see &%auto_thaw%& and &%timeout_frozen_after%&. -.option ignore_fromline_hosts main "host list&!!" unset +.options ignore_fromline_hosts main "host list&!!" unset &&& + ignore_fromline_local main boolean false .cindex "&""From""& line" .cindex "UUCP" "&""From""& line" Some broken SMTP clients insist on sending a UUCP-like &"From&~"& line before @@ -16290,8 +16501,6 @@ process rather than a remote host, and is using &%-bs%& to inject the messages, &%ignore_fromline_local%& must be set to achieve this effect. -.option ignore_fromline_local main boolean false -See &%ignore_fromline_hosts%& above. .option keep_environment main "string list" unset .cindex "environment" "values from" @@ -16411,6 +16620,16 @@ has been built with LDAP support. +.option limits_advertise_hosts main "host list&!!" * +.cindex LIMITS "suppressing advertising" +.cindex "ESMTP extensions" LIMITS +This option can be used to suppress the advertisement of the SMTP +LIMITS extension (RFC 9422) to specific hosts. +If permitted, Exim as a servier will advertise in the EHLO response +the limit for RCPT commands set by the &%recipients_max%& option (if it is set) +and the limit for MAIL commands set by the &%smtp_accept_max_per_connection%& +option. + .option local_from_check main boolean true .cindex "&'Sender:'& header line" "disabling addition of" .cindex "&'From:'& header line" "disabling checking of" @@ -16446,7 +16665,8 @@ has more details about &'Sender:'& processing. -.option local_from_prefix main string unset +.options local_from_prefix main string unset &&& + local_from_suffix main string unset When Exim checks the &'From:'& header line of locally submitted messages for matching the login id (see &%local_from_check%& above), it can be configured to ignore certain prefixes and suffixes in the local part of the address. This is @@ -16466,10 +16686,6 @@ matches the actual sender address that is constructed from the login name and qualify domain. -.option local_from_suffix main string unset -See &%local_from_prefix%& above. - - .option local_interfaces main "string list" "see below" This option controls which network interfaces are used by the daemon for listening; they are also used to identify the local host when routing. Chapter @@ -16511,15 +16727,21 @@ See also the ACL modifier &`control = suppress_local_fixups`&. Section .option localhost_number main string&!! unset .cindex "host" "locally unique number for" .cindex "message ids" "with multiple hosts" +.cindex multiple "systems sharing a spool" +.cindex "multiple hosts" "sharing a spool" +.cindex "shared spool directory" +.cindex "spool directory" sharing .vindex "&$localhost_number$&" Exim's message ids are normally unique only within the local host. If -uniqueness among a set of hosts is required, each host must set a different +uniqueness among a set of hosts is required +(eg. because they share a spool directory), +each host must set a different value for the &%localhost_number%& option. The string is expanded immediately after reading the configuration file (so that a number can be computed from the host name, for example) and the result of the expansion must be a number in the range 0&--16 (or 0&--10 on operating systems with case-insensitive file systems). This is available in subsequent string expansions via the variable -&$localhost_number$&. When &%localhost_number is set%&, the final two +&$localhost_number$&. When &%localhost_number%& is set, the final four characters of the message id, instead of just being a fractional part of the time, are computed from the time and the local host number as described in section &<>&. @@ -16875,7 +17097,6 @@ to be used in conjunction with &(oracle)& lookups (see section &<>&). The option is available only if Exim has been built with Oracle support. -.new .option panic_coredump main boolean false This option is rarely needed but can help for some debugging investigations. If set, when an internal error is detected by Exim which is sufficient @@ -16886,7 +17107,6 @@ then a coredump is requested. Note that most systems require additional administrative configuration to permit write a core file for a setuid program, which is Exim's common installed configuration. -.wen .option percent_hack_domains main "domain list&!!" unset .cindex "&""percent hack""&" @@ -16909,16 +17129,11 @@ a good idea to reject recipient addresses with percent characters in their local parts. Exim's default configuration does this. -.option perl_at_start main boolean false -.cindex "Perl" -This option is available only when Exim is built with an embedded Perl -interpreter. See chapter &<>& for details of its use. - - -.option perl_startup main string unset +.options perl_at_start main boolean false &&& + perl_startup main string unset .cindex "Perl" -This option is available only when Exim is built with an embedded Perl -interpreter. See chapter &<>& for details of its use. +These options are available only when Exim is built with an embedded Perl +interpreter. See chapter &<>& for details of their use. .option perl_taintmode main boolean false .cindex "Perl" @@ -17130,7 +17345,7 @@ and &%-odi%& command line options override &%queue_only%& unless &%queue_only_load%&, and &%smtp_accept_queue%&. -.option queue_only_file main string unset +.option queue_only_file main "string list" unset .cindex "queueing incoming messages" .cindex "message" "queueing by file existence" This option can be set to a colon-separated list of absolute path names, each @@ -17318,16 +17533,24 @@ or if the message was submitted locally (not using TCP/IP), and the &%-bnq%& option was not set. -.option recipients_max main integer 50000 +.option recipients_max main integer&!! 50000 .cindex "limit" "number of recipients" .cindex "recipient" "maximum number" -If this option is set greater than zero, it specifies the maximum number of +If the value resulting from expanding this option +is set greater than zero, it specifies the maximum number of original recipients for any message. Additional recipients that are generated by aliasing or forwarding do not count. SMTP messages get a 452 response for all recipients over the limit; earlier recipients are delivered as normal. Non-SMTP messages with too many recipients are failed, and no deliveries are done. +For SMTP message the expansion is done after the connection is +accepted (but before any SMTP conversation) and may depend on +the IP addresses and port numbers of the connection. +&*Note*&: If an expansion is used for the option, +care should be taken that a resonable value results for +non-SMTP messages. + .cindex "RCPT" "maximum number of incoming" &*Note*&: The RFCs specify that an SMTP server should accept at least 100 RCPT commands in a single message. @@ -17667,13 +17890,16 @@ This facility is only available on Linux. .cindex "banner for SMTP" .cindex "welcome banner for SMTP" .cindex "customizing" "SMTP banner" -This string, which is expanded every time it is used, is output as the initial +If a connect ACL does not supply a message, +this string (which is expanded every time it is used) is output as the initial positive response to an SMTP connection. The default setting is: .code smtp_banner = $smtp_active_hostname ESMTP Exim \ $version_number $tod_full .endd -Failure to expand the string causes a panic error. If you want to create a +Failure to expand the string causes a panic error; +a forced fail just closes the connection. +If you want to create a multiline response to the initial SMTP connection, use &"\n"& in the string at appropriate points, but not at the end. Note that the 220 code is not included in this string. Exim adds it automatically (several times in the case of a @@ -17808,7 +18034,9 @@ non-SMTP command lines are sent first. -.option smtp_ratelimit_hosts main "host list&!!" unset +.options smtp_ratelimit_hosts main "host list&!!" unset &&& + smtp_ratelimit_mail main string unset &&& + smtp_ratelimit_rcpt main string unset .cindex "SMTP" "rate limiting" .cindex "limit" "rate of message arrival" .cindex "RCPT" "rate limiting" @@ -17851,13 +18079,6 @@ seconds, increasing by a factor of 1.05 each time. The second setting applies delays to RCPT commands when more than four occur in a single message. -.option smtp_ratelimit_mail main string unset -See &%smtp_ratelimit_hosts%& above. - - -.option smtp_ratelimit_rcpt main string unset -See &%smtp_ratelimit_hosts%& above. - .option smtp_receive_timeout main time&!! 5m .cindex "timeout" "for SMTP input" @@ -18258,7 +18479,7 @@ is not required the &%tls_advertise_hosts%& option should be set empty. .cindex ALPN "set acceptable names for server" If this option is set, the TLS library supports ALPN, -and the client offers either more than +and the client offers either more than one ALPN name or a name which does not match the list, the TLS connection is declined. @@ -18415,20 +18636,23 @@ prior to the 4.80 release, as Debian used to patch Exim to raise the minimum acceptable bound from 1024 to 2048. -.option tls_eccurve main string&!! &`auto`& +.option tls_eccurve main string list&!! &`auto`& .cindex TLS "EC cryptography" -This option selects a EC curve for use by Exim when used with OpenSSL. -It has no effect when Exim is used with GnuTLS. +This option selects EC curves for use by Exim when used with OpenSSL. +It has no effect when Exim is used with GnuTLS +(the equivalent can be done using a priority string for the +&%tls_require_ciphers%& option). -After expansion it must contain a valid EC curve parameter, such as -&`prime256v1`&, &`secp384r1`&, or &`P-512`&. Consult your OpenSSL manual -for valid selections. +After expansion it must contain +one or (only for OpenSSL versiona 1.1.1 onwards) more +EC curve names, such as &`prime256v1`&, &`secp384r1`&, or &`P-521`&. +Consult your OpenSSL manual for valid curve names. For OpenSSL versions before (and not including) 1.0.2, the string &`auto`& selects &`prime256v1`&. For more recent OpenSSL versions &`auto`& tells the library to choose. -If the option expands to an empty string, no EC curves will be enabled. +If the option expands to an empty string, the effect is undefined. .option tls_ocsp_file main string&!! unset @@ -18719,6 +18943,12 @@ absolute and untainted. See also &%bounce_message_file%&. +.option wellknown_advertise_hosts main boolean unset +.cindex WELLKNOWN advertisement +.cindex "ESMTP extensions" WELLKNOWN +This option enables the advertising of the SMTP WELLKNOWN extension. +See also the &%acl_smtp_wellknown%& ACL (&<>&). + .option write_rejectlog main boolean true .cindex "reject log" "disabling" If this option is set false, Exim no longer writes anything to the reject log. @@ -19022,12 +19252,25 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence. .cindex "router" "restricting to specific domains" .vindex "&$domain_data$&" If this option is set, the router is skipped unless the current domain matches -the list. If the match is achieved by means of a file lookup, the data that the -lookup returned for the domain is placed in &$domain_data$& for use in string +the list. +The data returned by the list check +is placed in &$domain_data$& for use in string expansions of the driver's private options and in the transport. See section &<>& for a list of the order in which preconditions are evaluated. +A complex example, using a file like: +.code +alice@dom1 +bill@dom1 +maggie@dom1 +.endd +and checking both domain and local_part +.code +domains = ${domain:${lookup {$local_part@$domain} lseach,ret=key {/path/to/accountsfile}}} +local_parts = ${local_part:${lookup {$local_part@$domain} lseach,ret=key {/path/to/accountsfile}}} +.endd + .option driver routers string unset @@ -19391,7 +19634,7 @@ example: local_parts = dbm;/usr/local/specials/$domain_data .endd .vindex "&$local_part_data$&" -If the match is achieved by a lookup, the data that the lookup returned +the data returned by the list check for the local part is placed in the variable &$local_part_data$& for use in expansions of the router's private options or in the transport. You might use this option, for @@ -21980,6 +22223,12 @@ subject to address rewriting. Otherwise, they are treated like new addresses and are rewritten according to the global rewriting rules. +.option sieve_inbox redirect string&!! &"inbox"& +.new +The value of this option is passed to a Sieve filter to specify the +name of the mailbox used for "keep" operations (explicit or implicit). +.wen + .option sieve_subaddress redirect string&!! unset The value of this option is passed to a Sieve filter to specify the :subaddress part of an address. @@ -22363,7 +22612,7 @@ its removal from incoming messages, so that delivered messages can safely be resent to other recipients. &*Note:*& If used on a transport handling multiple recipients -(the smtp transport unless &%rcpt_max%& is 1, the appendfile, pipe or lmtp +(the smtp transport unless &%max_rcpt%& is 1, the appendfile, pipe or lmtp transport if &%batch_max%& is greater than 1) then information about Bcc recipients will be leaked. Doing so is generally not advised. @@ -22656,8 +22905,11 @@ If unset, or expanding to an empty string, no filtering is done. When the message is about to be written out, the command specified by &%transport_filter%& is started up in a separate, parallel process, and the entire message, including the header lines, is passed to it on its standard -input (this in fact is done from a third process, to avoid deadlock). The -command must be specified as an absolute path. +input (this in fact is done from a third process, to avoid deadlock). +The command must be specified as an absolute path. + +The process run by the command must use its standard input as the message +data to be transformed, and write the results on its standard output. The lines of the message that are written to the transport filter are terminated by newline (&"\n"&). The message is passed to the filter before any @@ -22727,7 +22979,17 @@ example: transport_filter = '/bin/cmd${if eq{$host}{a.b.c}{1}{2}}' .endd This runs the command &(/bin/cmd1)& if the host name is &'a.b.c'&, and -&(/bin/cmd2)& otherwise. If double quotes had been used, they would have been +&(/bin/cmd2)& otherwise. + +Option strings in general have any fully-surrounding double quote wrapping +removed early in parsing (see &<>&). +Then, for this option, quotes protect against whitespace being +regarded as a separator while splitting into the command argument vector. +Either double or single quotes can be used here; +the former interprets backlash-quoted charachters +and the latter does not. + +If double quotes had been used in this example, they would have been stripped by Exim when it read the option's value. When the value is used, if the single quotes were missing, the line would be split into two items, &`/bin/cmd${if`& and &`eq{$host}{a.b.c}{1}{2}`&, and an error would occur when @@ -23003,7 +23265,11 @@ fileinto "folder23"; .endd In this situation, the expansion of &%file%& or &%directory%& in the transport must transform the relative path into an appropriate absolute filename. In the -case of Sieve filters, the name &'inbox'& must be handled. It is the name that +case of Sieve filters, the name &'inbox'& must be handled. It is the +.new +default +.wen +name that is used as a result of a &"keep"& action in the filter. This example shows one way of handling this requirement: .code @@ -23019,6 +23285,12 @@ With this setting of &%file%&, &'inbox'& refers to the standard mailbox location, absolute paths are used without change, and other folders are in the &_mail_& directory within the home directory. +.new +An alternative for the &"keep"& aspect is to use the &%sieve_inbox%& option +on the redirect router that calls the Sieve filter, +to explicitly set the filename used. +.wen + &*Note 1*&: While processing an Exim filter, a relative path such as &_folder23_& is turned into an absolute path if a home directory is known to the router. In particular, this is the case if &%check_local_user%& is set. If @@ -23029,6 +23301,10 @@ path to the transport. &*Note 2*&: An absolute path in &$address_file$& is not treated specially; the &%file%& or &%directory%& option is still used if it is set. +.new +&*Note 3*&: Permitting a user to enable writes to an absolute path +may be a security issue. +.wen @@ -24331,7 +24607,7 @@ when the message is specified by the transport. .cindex "transports" "&(lmtp)&" .cindex "&(lmtp)& transport" .cindex "LMTP" "over a pipe" -.cindex "LMTP" "over a socket" +.cindex "LMTP" "over a unix-domain socket" The &(lmtp)& transport runs the LMTP protocol (RFC 2033) over a pipe to a specified command or by interacting with a Unix domain socket. @@ -24682,7 +24958,7 @@ Exim, and each argument is separately expanded, as described in section No part of the resulting command may be tainted. -.option environment pipe string&!! unset +.option environment pipe "string list&!!" unset .cindex "&(pipe)& transport" "environment for command" .cindex "environment" "&(pipe)& transport" This option is used to add additional variables to the environment in which the @@ -25188,6 +25464,11 @@ over a single TCP/IP connection. If the value is zero, there is no limit. For testing purposes, this value can be overridden by the &%-oB%& command line option. +.cindex "ESMTP extensions" LIMITS +If the peer advertises a LIMITS extension with a MAILMAX value, +and either TLSS is in use or was not advertised, +that value also constrains the result of this option. + .option dane_require_tls_ciphers smtp string&!! unset .cindex "TLS" "requiring specific ciphers for DANE" @@ -25400,15 +25681,22 @@ load-balancer, matching the session stored in the client's cache. Exim can pull out a server name, if there is one, from the response to the client's SMTP EHLO command. -The default value of this option: +For normal STARTTLS use, the default value of this option: .code ${if and { {match {$host} {.outlook.com\$}} \ {match {$item} {\N^250-([\w.]+)\s\N}} \ } {$1}} .endd suffices for one known case. + During the expansion of this option the &$item$& variable will have the server's EHLO response. + +For TLS-on-connect connections we do not have an EHLO +response to use. Because of this the default value of this option is +set to a static string for those cases, meaning that resumption will +always be attempted if permitted by the &%tls_resumption_hosts%& option. + The result of the option expansion is included in the key used to store and retrieve the TLS session, for session resumption. @@ -25591,12 +25879,16 @@ hard failure if required. See also &%hosts_try_auth%&, and chapter &<>& for details of authentication. -.option hosts_request_ocsp smtp "host list&!!" * +.option hosts_request_ocsp smtp "host list&!!" "see below" .cindex "TLS" "requiring for certain servers" Exim will request a Certificate Status on a TLS session for any host that matches this list. &%tls_verify_certificates%& should also be set for the transport. +The default is &"**"& if DANE is not in use for the connection, +or if DANE-TA us used. +It is empty if DANE-EE is used. + .option hosts_require_alpn smtp "host list&!!" unset .cindex ALPN "require negotiation in client" .cindex TLS ALPN @@ -25738,18 +26030,31 @@ If this option is set true when the &%protocol%& option is set to &"lmtp"&, the string &`IGNOREQUOTA`& is added to RCPT commands, provided that the LMTP server has advertised support for IGNOREQUOTA in its response to the LHLO command. -.option max_rcpt smtp integer 100 +.option max_rcpt smtp integer&!! 100 .cindex "RCPT" "maximum number of outgoing" -This option limits the number of RCPT commands that are sent in a single -SMTP message transaction. Each set of addresses is treated independently, and +This option, +after expansion, +limits the number of RCPT commands that are sent in a single +SMTP message transaction. +A value setting of zero disables the limit. + +If a constant is given, +each set of addresses is treated independently, and so can cause parallel connections to the same host if &%remote_max_parallel%& -permits this. A value setting of zero disables the limit. +permits this. + +.cindex "ESMTP extensions" LIMITS +If the peer advertises a LIMITS extension with a RCPTMAX value, +and either TLSS is in use or was not advertised, +that value also constrains the result of this option +and no parallel connections will be caused on meeting the RCPTMAX limit. .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 +(before a transport filter, if any) 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. @@ -25775,6 +26080,12 @@ 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. +.cindex "ESMTP extensions" LIMITS +If the peer advertises a LIMITS extension with a RCPTDOMAINMAX value, +and either TLSS is in use or was not advertised, +this option is regarded as being false. + + .option port smtp string&!! "see below" .cindex "port" "sending TCP/IP" .cindex "TCP/IP" "setting outgoing port" @@ -25808,6 +26119,9 @@ protocol (RFC 2033) instead of SMTP. This protocol is sometimes used for local deliveries into closed message stores. Exim also has support for running LMTP over a pipe to a local process &-- see chapter &<>&. +&*Note*&: When using LMTP it should be considered whether the default values +for some other features, such as DANE, are appropriate. + If this option is set to &"smtps"&, the default value for the &%port%& option changes to &"smtps"&, and the transport initiates TLS immediately after connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade. @@ -26016,7 +26330,8 @@ This option give a list of hosts for which, while verifying the server certificate, checks will be included on the host name (note that this will generally be the result of a DNS MX lookup) -versus Subject and Subject-Alternate-Name fields. Wildcard names are permitted +versus the Subject-Alternate-Name (or, if none, Subject-Name) fields. +Wildcard names are permitted, limited to being the initial component of a 3-or-more component FQDN. There is no equivalent checking on client certificates. @@ -26066,7 +26381,7 @@ If both this option and &%tls_try_verify_hosts%& are unset operation is as if this option selected all hosts. &*Warning*&: Including a host in &%tls_verify_hosts%& does not require that connections use TLS. -Fallback to in-clear communication will be done unless restricted by +Fallback to in-clear communication will be done unless restricted by the &%hosts_require_tls%& option. .option utf8_downconvert smtp integer&!! -1 @@ -27550,7 +27865,6 @@ no successful authentication. Successful authentication sets up information used by the &%authresults%& expansion item. -.new .cindex authentication "failure event, server" If an authenticator is run and does not succeed, an event (see &<>&) of type "auth:fail" is raised. @@ -27561,7 +27875,6 @@ will be valid. If the event is serviced and a string is returned then the string will be logged instead of the default log line. See <> for details on events. -.wen .section "Testing server authentication" "SECID169" @@ -27640,7 +27953,6 @@ Exim abandons trying to send the message to the host for the moment. It will try again later. If there are any backup hosts available, they are tried in the usual way. -.new .next .cindex authentication "failure event, client" If the response to authentication is a permanent error (5&'xx'& code), @@ -27650,7 +27962,6 @@ While the event is being processed the variable will be valid. If the event is serviced and a string is returned then the string will be logged. See <> for details on events. -.wen .next If the response to authentication is a permanent error (5&'xx'& code), Exim @@ -28207,7 +28518,7 @@ Dovecot 2 POP/IMAP server, which can support a number of authentication methods. Note that Dovecot must be configured to use auth-client not auth-userdb. If you are using Dovecot to authenticate POP/IMAP clients, it might be helpful to use the same mechanisms for SMTP authentication. This is a server -authenticator only. There is only one option: +authenticator only. There is only one non-generic option: .option server_socket dovecot string unset @@ -28219,6 +28530,7 @@ authenticators for different mechanisms. For example: dovecot_plain: driver = dovecot public_name = PLAIN + server_advertise_condition = ${if def:tls_in_cipher} server_socket = /var/run/dovecot/auth-client server_set_id = $auth1 @@ -28228,6 +28540,11 @@ dovecot_ntlm: server_socket = /var/run/dovecot/auth-client server_set_id = $auth1 .endd + +&*Note*&: plaintext authentication methods such as PLAIN and LOGIN +should not be advertised on cleartext SMTP connections. +See the discussion in section &<>&. + If the SMTP connection is encrypted, or if &$sender_host_address$& is equal to &$received_ip_address$& (that is, the connection is local), the &"secured"& option is passed in the Dovecot authentication command. If, for a TLS @@ -28826,9 +29143,10 @@ for which it must have been requested via the (see &<>&). If an authenticator of this type is configured it is -run before any SMTP-level communication is done, +run immediately after a TLS connection being negotiated +(due to either STARTTLS or TLS-on-connect) and can authenticate the connection. -If it does, SMTP authentication is not offered. +If it does, SMTP authentication is not subsequently offered. A maximum of one authenticator of this type may be present. @@ -29034,8 +29352,8 @@ When using OpenSSL, this option is ignored. (If an API is found to let OpenSSL be configured in this way, let the Exim Maintainers know and we'll likely use it). .next -With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option -main option, it must be ordered to match the &%tls_certificate%& list. +With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option, +it must be ordered to match the &%tls_certificate%& list. .next Some other recently added features may only be available in one or the other. This should be documented with the feature. If the documentation does not @@ -29386,7 +29704,7 @@ For outgoing SMTP deliveries, &$tls_out_cipher$& is used and logged (again depending on the &%tls_cipher%& log selector). -.subsection "Requesting and verifying client certificates" SECID183 +.subsection "Requesting and verifying client certificates" .cindex "certificate" "verification of client" .cindex "TLS" "client certificate verification" If you want an Exim server to request a certificate when negotiating a TLS @@ -29439,86 +29757,7 @@ Because it is often a long text string, it is not included in the log line or certificate is supplied, &$tls_in_peerdn$& is empty. -.section "Revoked certificates" "SECID184" -.cindex "TLS" "revoked certificates" -.cindex "revocation list" -.cindex "certificate" "revocation list" -.cindex "OCSP" "stapling" -Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when -certificates are revoked. If you have such a list, you can pass it to an Exim -server using the global option called &%tls_crl%& and to an Exim client using -an identically named option for the &(smtp)& transport. In each case, the value -of the option is expanded and must then be the name of a file that contains a -CRL in PEM format. -The downside is that clients have to periodically re-download a potentially huge -file from every certificate authority they know of. - -The way with most moving parts at query time is Online Certificate -Status Protocol (OCSP), where the client verifies the certificate -against an OCSP server run by the CA. This lets the CA track all -usage of the certs. It requires running software with access to the -private key of the CA, to sign the responses to the OCSP queries. OCSP -is based on HTTP and can be proxied accordingly. - -The only widespread OCSP server implementation (known to this writer) -comes as part of OpenSSL and aborts on an invalid request, such as -connecting to the port and then disconnecting. This requires -re-entering the passphrase each time some random client does this. - -The third way is OCSP Stapling; in this, the server using a certificate -issued by the CA periodically requests an OCSP proof of validity from -the OCSP server, then serves it up inline as part of the TLS -negotiation. This approach adds no extra round trips, does not let the -CA track users, scales well with number of certs issued by the CA and is -resilient to temporary OCSP server failures, as long as the server -starts retrying to fetch an OCSP proof some time before its current -proof expires. The downside is that it requires server support. - -Unless Exim is built with the support disabled, -or with GnuTLS earlier than version 3.3.16 / 3.4.8 -support for OCSP stapling is included. - -There is a global option called &%tls_ocsp_file%&. -The file specified therein is expected to be in DER format, and contain -an OCSP proof. Exim will serve it as part of the TLS handshake. This -option will be re-expanded for SNI, if the &%tls_certificate%& option -contains &`tls_in_sni`&, as per other TLS options. - -Exim does not at this time implement any support for fetching a new OCSP -proof. The burden is on the administrator to handle this, outside of -Exim. The file specified should be replaced atomically, so that the -contents are always valid. Exim will expand the &%tls_ocsp_file%& option -on each connection, so a new file will be handled transparently on the -next connection. - -When built with OpenSSL Exim will check for a valid next update timestamp -in the OCSP proof; if not present, or if the proof has expired, it will be -ignored. - -For the client to be able to verify the stapled OCSP the server must -also supply, in its stapled information, any intermediate -certificates for the chain leading to the OCSP proof from the signer -of the server certificate. There may be zero or one such. These -intermediate certificates should be added to the server OCSP stapling -file named by &%tls_ocsp_file%&. - -Note that the proof only covers the terminal server certificate, -not any of the chain from CA to it. - -There is no current way to staple a proof for a client certificate. - -.code - A helper script "ocsp_fetch.pl" for fetching a proof from a CA - OCSP server is supplied. The server URL may be included in the - server certificate, if the CA is helpful. - - One failure mode seen was the OCSP Signer cert expiring before the end - of validity of the OCSP proof. The checking done by Exim/OpenSSL - noted this as invalid overall, but the re-fetch script did not. -.endd - - -.section "Caching of static server configuration items" "SECTserverTLScache" +.subsection "Caching of static server configuration items" "SSECTserverTLScache" .cindex certificate caching .cindex privatekey caching .cindex crl caching @@ -29564,10 +29803,10 @@ 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. +is acceptable in configurations for the Exim executable. Caching of the system Certificate Authorities bundle can -save siginificant time and processing on every TLS connection +save significant time and processing on every TLS connection accepted by Exim. @@ -29737,10 +29976,10 @@ 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. +is acceptable in configurations for the Exim executable. Caching of the system Certificate Authorities bundle can -save siginificant time and processing on every TLS connection +save significant time and processing on every TLS connection initiated by Exim. @@ -29824,6 +30063,7 @@ When Exim is built against GnuTLS, SNI support is available as of GnuTLS 0.5.10. (Its presence predates the current API which Exim uses, so if Exim built, then you have SNI support). +.subsection ALPN .cindex TLS ALPN .cindex ALPN "general information" .cindex TLS "Application Layer Protocol Names" @@ -29834,7 +30074,7 @@ connection. The client for the connection proposes a set of protocol names, and the server responds with a selected one. It is not, as of 2021, commonly used for SMTP connections. -However, to guard against misirected or malicious use of web clients +However, to guard against misdirected or malicious use of web clients (which often do use ALPN) against MTA ports, Exim by default check that there is no incompatible ALPN specified by a client for a TLS connection. If there is, the connection is rejected. @@ -29844,7 +30084,7 @@ The behaviour of both client and server can be configured using the options &%tls_alpn%& and &%hosts_require_alpn%&. There are no variables providing observability. Some feature-specific logging may appear on denied connections, but this -depends on the behavious of the peer +depends on the behaviour of the peer (not all peers can send a feature-specific TLS Alert). This feature is available when Exim is built with @@ -29993,6 +30233,94 @@ For information on creating self-signed CA certificates and using them to sign user certificates, see the &'General implementation overview'& chapter of the Open-source PKI book, available online at &url(https://sourceforge.net/projects/ospkibook/). + + +.subsection "Revoked certificates" +.cindex "TLS" "revoked certificates" +.cindex "revocation list" +.cindex "certificate" "revocation list" +.cindex "OCSP" "stapling" +There are three ways for a certificate to be made unusable +before its expiry. + +.ilist +Certificate issuing authorities issue Certificate Revocation Lists (CRLs) when +certificates are revoked. If you have such a list, you can pass it to an Exim +server using the global option called &%tls_crl%& and to an Exim client using +an identically named option for the &(smtp)& transport. In each case, the value +of the option is expanded and must then be the name of a file that contains a +CRL in PEM format. +The downside is that clients have to periodically re-download a potentially huge +file from every certificate authority they know of. + +.next +The way with most moving parts at query time is Online Certificate +Status Protocol (OCSP), where the client verifies the certificate +against an OCSP server run by the CA. This lets the CA track all +usage of the certs. It requires running software with access to the +private key of the CA, to sign the responses to the OCSP queries. OCSP +is based on HTTP and can be proxied accordingly. + +The only widespread OCSP server implementation (known to this writer) +comes as part of OpenSSL and aborts on an invalid request, such as +connecting to the port and then disconnecting. This requires +re-entering the passphrase each time some random client does this. + +.next +The third way is OCSP Stapling; in this, the server using a certificate +issued by the CA periodically requests an OCSP proof of validity from +the OCSP server, then serves it up inline as part of the TLS +negotiation. This approach adds no extra round trips, does not let the +CA track users, scales well with number of certs issued by the CA and is +resilient to temporary OCSP server failures, as long as the server +starts retrying to fetch an OCSP proof some time before its current +proof expires. The downside is that it requires server support. + +Unless Exim is built with the support disabled, +or with GnuTLS earlier than version 3.3.16 / 3.4.8 +support for OCSP stapling is included. + +There is a global option called &%tls_ocsp_file%&. +The file specified therein is expected to be in DER format, and contain +an OCSP proof. Exim will serve it as part of the TLS handshake. This +option will be re-expanded for SNI, if the &%tls_certificate%& option +contains &`tls_in_sni`&, as per other TLS options. + +Exim does not at this time implement any support for fetching a new OCSP +proof. The burden is on the administrator to handle this, outside of +Exim. The file specified should be replaced atomically, so that the +contents are always valid. Exim will expand the &%tls_ocsp_file%& option +on each connection, so a new file will be handled transparently on the +next connection. + +When built with OpenSSL Exim will check for a valid next update timestamp +in the OCSP proof; if not present, or if the proof has expired, it will be +ignored. + +For the client to be able to verify the stapled OCSP the server must +also supply, in its stapled information, any intermediate +certificates for the chain leading to the OCSP proof from the signer +of the server certificate. There may be zero or one such. These +intermediate certificates should be added to the server OCSP stapling +file named by &%tls_ocsp_file%&. + +Note that the proof only covers the terminal server certificate, +not any of the chain from CA to it. + +There is no current way to staple a proof for a client certificate. + +.code + A helper script "ocsp_fetch.pl" for fetching a proof from a CA + OCSP server is supplied. The server URL may be included in the + server certificate, if the CA is helpful. + + One failure mode seen was the OCSP Signer cert expiring before the end + of validity of the OCSP proof. The checking done by Exim/OpenSSL + noted this as invalid overall, but the re-fetch script did not. +.endd +.endlist + + .ecindex IIDencsmtp1 .ecindex IIDencsmtp2 @@ -30110,18 +30438,24 @@ DANE scales better than having to maintain (and communicate via side-channel) co 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. -DANE requires a server operator to do three things: 1) run DNSSEC. This provides assurance to clients +DANE requires a server operator to do three things: +.olist +Run DNSSEC. This provides assurance to clients that DNS lookups they do for the server have not been tampered with. The domain MX record applying to this server, its A record, its TLSA record and any associated CNAME records must all be covered by DNSSEC. -2) add TLSA DNS records. These say what the server certificate for a TLS connection should be. -3) offer a server certificate, or certificate chain, in TLS connections which is is anchored by one of the TLSA records. +.next +Add TLSA DNS records. These say what the server certificate for a TLS connection should be. +.next +Offer a server certificate, or certificate chain, in TLS connections which is anchored by one of the TLSA records. +.endlist There are no changes to Exim specific to server-side operation of DANE. Support for client-side operation of DANE can be included at compile time by defining SUPPORT_DANE=yes in &_Local/Makefile_&. If it has been included, the macro "_HAVE_DANE" will be defined. +.subsection "DNS records" A TLSA record consist of 4 fields, the "Certificate Usage", the "Selector", the "Matching type", and the "Certificate Association Data". For a detailed description of the TLSA record see @@ -30202,6 +30536,7 @@ libraries. This means no MD5 and no SHA-1. SHA2-256 is the minimum for reliable interoperability (and probably the maximum too, in 2018). +.subsection "Interaction with OCSP" The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise be limited by the DNS TTL on the TLSA records). However, this is likely to only be usable with DANE-TA. NOTE: the default of requesting OCSP for all hosts is modified iff DANE is in use, to: @@ -30222,6 +30557,7 @@ This modification of hosts_request_ocsp is only done if it has the default value those who use &%hosts_require_ocsp%&, should consider the interaction with DANE in their OCSP settings. +.subsection "Client configuration" For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%& and &%dane_require_tls_ciphers%&. The &"require"& variant will result in failure if the target host is not @@ -30260,6 +30596,7 @@ verification evaluation is wanted, the above variables should be set appropriate The router and transport option &%dnssec_request_domains%& must not be set to &"never"&, and &%dnssec_require_domains%& is ignored. +.subsection Observability If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane". There is a new variable &$tls_out_dane$& which will have "yes" if @@ -30275,13 +30612,20 @@ required. This is intended to support TLS-reporting as defined in The &$event_data$& will be one of the Result Types defined in Section 4.3 of that document. +.subsection General Under GnuTLS, DANE is only supported from version 3.0.0 onwards. -DANE is specified in published RFCs and decouples certificate authority trust +DANE is specified in RFC 6698. It decouples certificate authority trust selection from a "race to the bottom" of "you must trust everything for mail -to get through". There is an alternative technology called MTA-STS, which -instead publishes MX trust anchor information on an HTTPS website. At the -time this text was last updated, MTA-STS was still a draft, not yet an RFC. +to get through". +It does retain the need to trust the assurances provided by the DNSSEC tree. + +There is an alternative technology called MTA-STS (RFC 8461), which +instead publishes MX trust anchor information on an HTTPS website. +The discovery of the address for that website does not (per standard) +require DNSSEC, and could be regarded as being less secure than DANE +as a result. + Exim has no support for MTA-STS as a client, but Exim mail server operators can choose to publish information describing their TLS configuration using MTA-STS to let those clients who do use that protocol derive trust @@ -30352,6 +30696,7 @@ options in the main part of the configuration. These options are: .cindex "RCPT" "ACL for" .cindex "STARTTLS, ACL for" .cindex "VRFY" "ACL for" +.cindex "WELLKNOWN" "ACL for" .cindex "SMTP" "connection, ACL for" .cindex "non-SMTP messages" "ACLs for" .cindex "MIME content scanning" "ACL for" @@ -30378,6 +30723,7 @@ options in the main part of the configuration. These options are: .irow &%acl_smtp_rcpt%& "ACL for RCPT" .irow &%acl_smtp_starttls%& "ACL for STARTTLS" .irow &%acl_smtp_vrfy%& "ACL for VRFY" +.irow &%acl_smtp_wellknown%& "ACL for WELLKNOWN" .endtable For example, if you set @@ -30393,7 +30739,7 @@ trying to deliver the message. It is therefore recommended that you do as much testing as possible at RCPT time. -.subsection "The non-SMTP ACLs" SECID190 +.subsection "The non-SMTP ACLs" SECnonSMTP .cindex "non-SMTP messages" "ACLs for" The non-SMTP ACLs apply to all non-interactive incoming messages, that is, they apply to batched SMTP as well as to non-SMTP messages. (Batched SMTP is not @@ -30427,7 +30773,7 @@ kind of rejection is treated as permanent, because there is no way of sending a temporary error for these kinds of message. -.subsection "The SMTP connect ACL" SECID191 +.subsection "The SMTP connect ACL" SECconnectACL .cindex "SMTP" "connection, ACL for" .oindex &%smtp_banner%& The ACL test specified by &%acl_smtp_connect%& happens at the start of an SMTP @@ -30437,11 +30783,12 @@ accepted by an &%accept%& verb that has a &%message%& modifier, the contents of the message override the banner message that is otherwise specified by the &%smtp_banner%& option. -For tls-on-connect connections, the ACL is run after the TLS connection -is accepted (however, &%host_reject_connection%& is tested before). +For tls-on-connect connections, the ACL is run before the TLS connection +is accepted; if the ACL does not accept then the TCP connection is dropped without +any TLS startup attempt and without any SMTP response being transmitted. -.subsection "The EHLO/HELO ACL" SECID192 +.subsection "The EHLO/HELO ACL" SECheloACL .cindex "EHLO" "ACL for" .cindex "HELO" "ACL for" The ACL test specified by &%acl_smtp_helo%& happens when the client issues an @@ -30462,7 +30809,7 @@ affect the EHLO options that are listed on the second and subsequent lines of an EHLO response. -.subsection "The DATA ACLs" SECID193 +.subsection "The DATA ACLs" SECdataACLS .cindex "DATA" "ACLs for" Two ACLs are associated with the DATA command, because it is two-stage command, with two responses being sent to the client. @@ -30505,6 +30852,10 @@ and the &%acl_smtp_mime%& ACLs. The &%acl_smtp_dkim%& ACL is available only when Exim is compiled with DKIM support enabled (which is the default). +If, for a specific message, an ACL control +&*dkim_disable_verify*& +has been set, this &%acl_smtp_dkim%& ACL is not called. + The ACL test specified by &%acl_smtp_dkim%& happens after a message has been received, and is executed for each DKIM signature found in a message. If not otherwise specified, the default action is to accept. @@ -30555,6 +30906,60 @@ This ACL is evaluated after &%acl_smtp_dkim%& but before &%acl_smtp_data%&. If the ACL is not defined, processing completes as if the feature was not requested by the client. +.subsection "The SMTP WELLKNOWN ACL" SECTWELLKNOWNACL +.cindex "WELLKNOWN" "ACL for" +.oindex "&%acl_smtp_wellknown%&" +The &%acl_smtp_wellknown%& ACL is available only when Exim is compiled +with WELLKNOWN support enabled. + +The ACL determines the response to an SMTP WELLKNOWN command, using the normal +accept/defer/deny verbs for the response code, +and a new &"control=wellknown"& modifier. +This modifier takes a single option, separated by a '/' +character, which must be the name of a file containing the response +cleartext. The modifier is expanded before use in the usual way before +it is used. The configuration is responsible for picking a suitable file +to return and, most importantly, not returning any unexpected file. +The argument for the SMTP verb will be available in the &$smtp_command_argument$& +variable and can be used for building the file path. +If the file path given in the modifier is empty or inacessible, the control will +fail. + +For example: +.code + check_wellknown: + accept control = wellknown/\ + ${lookup {${xtextd:$smtp_command_argument}} \ + dsearch,key=path,filter=file,ret=full \ + {$spooldir/wellknown.d}} +.endd +File content will be encoded in &"xtext"& form, and line-wrapping +for line-length limitation will be done before transmission. +A response summary line will be prepended, with the (pre-encoding) file size. + +The above example uses the expansion operator ${xtextd:} +which is needed to decode the xtext-encoded key from the SMTP verb. + +Under the util directory there is a "mailtest" utility which can be used +to test/retrieve WELLKNOWN items. Syntax is +.code + mailtest -h host.example.com -w security.txt +.endd + +WELLKNOWN is a ESMTP extension providing access to extended +information about the server. It is modelled on the webserver +facilities documented in RFC 8615 and can be used for a security.txt +file and could be used for ACME handshaking (RFC 8555). + +Exim will advertise WELLKNOWN support in the EHLO response +.oindex &%wellknown_advertise_hosts%& +(conditional on a new option &%wellknown_advertise_hosts%&) +and service WELLKNOWN smtp verbs having a single parameter +giving a key for an item of "site-wide metadata". +The verb and key are separated by whitespace, +and the key is xtext-encoded (per RFC 3461 section 4). + + .subsection "The QUIT ACL" SECTQUITACL .cindex "QUIT, ACL for" The ACL for the SMTP QUIT command is anomalous, in that the outcome of the ACL @@ -30725,12 +31130,13 @@ For &%acl_not_smtp%&, &%acl_smtp_auth%&, &%acl_smtp_connect%&, &%acl_smtp_mime%&, &%acl_smtp_predata%&, and &%acl_smtp_starttls%&, the action when the ACL is not defined is &"accept"&. -For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, and -&%acl_smtp_vrfy%&), the action when the ACL is not defined is &"deny"&. -This means that &%acl_smtp_rcpt%& must be defined in order to receive any -messages over an SMTP connection. For an example, see the ACL in the default -configuration file. - +For the others (&%acl_smtp_etrn%&, &%acl_smtp_expn%&, &%acl_smtp_rcpt%&, +&%acl_smtp_vrfy%& +and &%acl_smtp_wellknown%&), +the action when the ACL +is not defined is &"deny"&. This means that &%acl_smtp_rcpt%& must be +defined in order to receive any messages over an SMTP connection. +For an example, see the ACL in the default configuration file. @@ -30802,7 +31208,8 @@ option to do this.) .section "Format of an ACL" "SECID199" .cindex "&ACL;" "format of" .cindex "&ACL;" "verbs, definition of" -An individual ACL consists of a number of statements. Each statement starts +An individual ACL definition consists of a number of statements. +Each statement starts with a verb, optionally followed by a number of conditions and &"modifiers"&. Modifiers can change the way the verb operates, define error and log messages, set variables, insert delays, and vary the processing of accepted messages. @@ -30821,6 +31228,9 @@ happens then depends on the verb (and in one case, on a special modifier). Not all the conditions make sense at every testing point. For example, you cannot test a sender address in the ACL that is run for a VRFY command. +The definition of an ACL ends where another starts, +or a different configuration section starts. + .section "ACL verbs" "SECID200" The ACL verbs are as follows: @@ -31364,8 +31774,11 @@ the message modifier cannot override the 221 response code. The text in a &%message%& modifier is literal; any quotes are taken as literals, but because the string is expanded, backslash escapes are processed -anyway. If the message contains newlines, this gives rise to a multi-line SMTP +anyway. +If the message contains newlines, this gives rise to a multi-line SMTP response. +A long message line will also be split into multi-line SMTP responses, +on word boundaries if possible. .vindex "&$acl_verify_message$&" While the text is being expanded, the &$acl_verify_message$& variable @@ -31589,7 +32002,7 @@ pretrigger=<&'size'&> This option specifies a memory buffuer to be used immediate writes to file are done as normal. trigger=<&'reason'&> This option selects cause for the pretrigger buffer - see above) to be copied to file. A reason of $*now* + see above) to be copied to file. A reason of &*now*& take effect immediately; one of &*paniclog*& triggers on a write to the panic log. .endd @@ -31659,6 +32072,7 @@ work with. .vitem &*control&~=&~fakedefer/*&<&'message'&> .cindex "fake defer" .cindex "defer, fake" +.cindex fakedefer This control works in exactly the same way as &%fakereject%& (described below) except that it causes an SMTP 450 response after the message data instead of a 550 response. You must take care when using &%fakedefer%& because it causes the @@ -31668,6 +32082,7 @@ use &%fakedefer%& if the message is to be delivered normally. .vitem &*control&~=&~fakereject/*&<&'message'&> .cindex "fake rejection" .cindex "rejection, fake" +.cindex fakereject This control is permitted only for the MAIL, RCPT, and DATA ACLs, in other words, only when an SMTP message is being received. If Exim accepts the message, instead the final 250 response, a 550 rejection message is sent. @@ -31826,6 +32241,11 @@ that are being submitted at the same time using &%-bs%& or &%-bS%&. This control enables conversion of UTF-8 in message envelope addresses to a-label form. For details see section &<>&. + +.vitem &*control&~=&~wellknown*& +This control sets up a response data file for a WELLKNOWN SMTP command. +It may only be used in an ACL servicing that command. +For details see section &<>&. .endlist vlist @@ -31969,8 +32389,22 @@ Headers will not be removed from the message if the modifier is used in DATA, MIME or DKIM ACLs for a message delivered by cutthrough routing. More than one header can be removed at the same time by using a colon separated -list of header names. The header matching is case insensitive. Wildcards are -not permitted, nor is list expansion performed, so you cannot use hostlists to +list of header specifiers. +If a specifier does not start with a circumflex (^) +then it is treated as a header name. +The header name matching is case insensitive. +If it does, then it is treated as a (front-anchored) +regular expression applied to the whole header. + +&*Note*&: The colon terminating a header name will need to be doubled +if used in an RE, and there can legitimately be whitepace before it. + +Example: +.code +remove_header = \N^(?i)Authentication-Results\s*::\s*example.org;\N +.endd + +List expansion is not performed, so you cannot use hostlists to create a list of headers, however both connection and message variable expansion are performed (&%$acl_c_*%& and &%$acl_m_*%&), illustrated in this example: .code @@ -31979,14 +32413,14 @@ warn hosts = +internal_hosts warn message = Remove internal headers remove_header = $acl_c_ihdrs .endd -Header names for removal are accumulated during the MAIL, RCPT, and predata ACLs. +Header specifiers for removal are accumulated during the MAIL, RCPT, and predata ACLs. Matching header lines are removed from the message before processing the DATA and MIME ACLs. If multiple header lines match, all are removed. There is no harm in attempting to remove the same header twice nor in removing -a non-existent header. Further header lines to be removed may be accumulated -during the DATA and MIME ACLs, after which they are removed from the message, -if present. In the case of non-SMTP messages, headers to be removed are -accumulated during the non-SMTP ACLs, and are removed from the message after +a non-existent header. Further header specifiers for removal may be accumulated +during the DATA and MIME ACLs, after which matching headers are removed +if present. In the case of non-SMTP messages, remove specifiers are +accumulated during the non-SMTP ACLs, and are acted on after all the ACLs have run. If a message is rejected after DATA or by the non-SMTP ACL, there really is no effect because there is no logging of what headers would have been removed. @@ -32969,7 +33403,7 @@ address you should specify alternate list separators for both the outer The &%seen%& ACL condition can be used to test whether a situation has been previously met. It uses a hints database to record a timestamp against a key. -host. The syntax of the condition is: +The syntax of the condition is: .display &`seen =`& <&'optional flag'&><&'time interval'&> &`/`& <&'options'&> .endd @@ -33087,16 +33521,23 @@ the &%count=%& option. .subsection "Ratelimit options for what is being measured" ratoptmea .cindex "rate limiting" "per_* options" -The &%per_conn%& option limits the client's connection rate. It is not +.vlist +.vitem per_conn +.cindex "rate limiting" per_conn +This option limits the client's connection rate. It is not normally used in the &%acl_not_smtp%&, &%acl_not_smtp_mime%&, or &%acl_not_smtp_start%& ACLs. -The &%per_mail%& option limits the client's rate of sending messages. This is +.vitem per_mail +.cindex "rate limiting" per_conn +This option limits the client's rate of sending messages. This is the default if none of the &%per_*%& options is specified. It can be used in &%acl_smtp_mail%&, &%acl_smtp_rcpt%&, &%acl_smtp_predata%&, &%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_not_smtp%&. -The &%per_byte%& option limits the sender's email bandwidth. It can be used in +.vitem per_byte +.cindex "rate limiting" per_conn +This option limits the sender's email bandwidth. It can be used in the same ACLs as the &%per_mail%& option, though it is best to use this option in the &%acl_smtp_mime%&, &%acl_smtp_data%& or &%acl_not_smtp%& ACLs; if it is used in an earlier ACL, Exim relies on the SIZE parameter given by the client @@ -33104,7 +33545,9 @@ in its MAIL command, which may be inaccurate or completely missing. You can follow the limit &'m'& in the configuration with K, M, or G to specify limits in kilobytes, megabytes, or gigabytes, respectively. -The &%per_rcpt%& option causes Exim to limit the rate at which recipients are +.vitem per_rcpt +.cindex "rate limiting" per_rcpt +This 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%&, or &%acl_smtp_data%& ACLs. In &%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other @@ -33112,24 +33555,37 @@ ACLs the rate is updated with the total (accepted) recipient count in one go. No in either case the rate limiting engine will see a message with many recipients as a large high-speed burst. -The &%per_addr%& option is like the &%per_rcpt%& option, except it counts the +.vitem per_addr +.cindex "rate limiting" per_addr +This option is like the &%per_rcpt%& option, except it counts the number of different recipients that the client has sent messages to in the last time period. That is, if the client repeatedly sends messages to the same recipient, its measured rate is not increased. This option can only be used in &%acl_smtp_rcpt%&. -The &%per_cmd%& option causes Exim to recompute the rate every time the +.vitem per_cmd +.cindex "rate limiting" per_cmd +This option causes Exim to recompute the rate every time the condition is processed. This can be used to limit the rate of any SMTP command. If it is used in multiple ACLs it can limit the aggregate rate of multiple different commands. -The &%count=%& option can be used to alter how much Exim adds to the client's -measured rate. For example, the &%per_byte%& option is equivalent to -&`per_mail/count=$message_size`&. If there is no &%count=%& option, Exim +.vitem count +.cindex "rate limiting" count +This option can be used to alter how much Exim adds to the client's +measured rate. +A value is required, after an equals sign. +For example, the &%per_byte%& option is equivalent to +&`per_mail/count=$message_size`&. +If there is no &%count=%& option, Exim increases the measured rate by one (except for the &%per_rcpt%& option in ACLs -other than &%acl_smtp_rcpt%&). The count does not have to be an integer. +other than &%acl_smtp_rcpt%&). +The count does not have to be an integer. -The &%unique=%& option is described in section &<>& below. +.vitem unique +.cindex "rate limiting" unique +This option is described in section &<>& below. +.endlist .subsection "Ratelimit update modes" ratoptupd @@ -34779,13 +35235,11 @@ If the string does not start with a slash, it is used as the filename, and the default path is then used. .endlist The &%decode%& condition normally succeeds. It is only false for syntax -errors or unusual circumstances such as memory shortages. You can easily decode -a file with its original, proposed filename using -.code -decode = $mime_filename -.endd -However, you should keep in mind that &$mime_filename$& might contain -anything. If you place files outside of the default path, they are not +errors or unusual circumstances such as memory shortages. +The variable &$mime_filename$& will have the suggested name for the file. +Note however that this might contain anything, and is very difficult +to safely use as all or even part of the filename. +If you place files outside of the default path, they are not automatically unlinked. For RFC822 attachments (these are messages attached to messages, with a @@ -35100,9 +35554,10 @@ The arguments are as follows: (the -D file). The file is open for reading and writing, but updating it is not recommended. &*Warning*&: You must &'not'& close this file descriptor. -The descriptor is positioned at character 19 of the file, which is the first -character of the body itself, because the first 19 characters are the message -id followed by &`-D`& and a newline. If you rewind the file, you should use the +The descriptor is positioned at character 26 of the file, which is the first +character of the body itself, because the first 26 characters (19 characters +before Exim 4.97) are the message id followed by &`-D`& and a newline. +If you rewind the file, you should use the macro SPOOL_DATA_START_OFFSET to reset to the start of the data, just in case this changes in some future version. .next @@ -35816,6 +36271,7 @@ The system filter is run at the start of a delivery attempt, before any routing is done. If a message fails to be completely delivered at the first attempt, the system filter is run again at the start of every retry. If you want your filter to do something only once per message, you can make use +.cindex retry condition of the &%first_delivery%& condition in an &%if%& command in the filter to prevent it happening on retries. @@ -36217,8 +36673,6 @@ other MTAs, the way Exim handles line endings for all messages is now as follows: .ilist -LF not preceded by CR is treated as a line ending. -.next CR is treated as a line ending; if it is immediately followed by LF, the LF is ignored. .next @@ -36233,7 +36687,10 @@ people trying to play silly games. .next If the first header line received in a message ends with CRLF, a subsequent bare LF in a header line is treated in the same way as a bare CR in a header -line. +line and a bare LF in a body line is replaced with a space. +.next +If the first header line received in a message does not end with CRLF, a subsequent +LF not preceded by CR is treated as a line ending. .endlist @@ -36883,12 +37340,8 @@ See the next section for more detail about error handling. .cindex "SMTP" "batching over TCP/IP" When a message is successfully delivered over a TCP/IP SMTP connection, Exim looks in the hints database for the transport to see if there are any queued -messages waiting for the host to which it is connected. If it finds one, it -creates a new Exim process using the &%-MC%& option (which can only be used by -a process running as root or the Exim user) and passes the TCP/IP socket to it -so that it can deliver another message using the same socket. The new process -does only those deliveries that are routed to the connected host, and may in -turn pass the socket on to a third process, and so on. +messages waiting for the host to which it is connected. +If it finds one, it arranges to attempt that message on the same connection. The &%connection_max_messages%& option of the &(smtp)& transport can be used to limit the number of messages sent down a single TCP/IP connection. @@ -37226,6 +37679,14 @@ RCPT failures. .subsection "The ETRN command" SECTETRN .cindex "ETRN" "processing" .cindex "ESMTP extensions" ETRN +Most modern installations never need to use this. +It is used for managing messages queued for an intermittently-connecting +destination (eg. one using a dialup connection). + +.oindex "&%acl_smtp_etrn%&" +The command is only available if permitted by an ACL +specfied by the main-section &%acl_smtp_etrn%& option. + RFC 1985 describes an ESMTP command called ETRN that is designed to overcome the security problems of the TURN command (which has fallen into disuse). When Exim receives an ETRN command on a TCP/IP connection, it runs @@ -38707,6 +39168,7 @@ the following table: .display &`A `& authenticator name (and optional id and sender) &`C `& SMTP confirmation on delivery +&`Ci `& connection identifier &` `& command list for &"no mail in SMTP session"& &`CV `& certificate verification status &`D `& duration of &"no mail in SMTP session"& @@ -38795,7 +39257,7 @@ logging and the message has a DKIM signature header. .section "Reducing or increasing what is logged" "SECTlogselector" .cindex "log" "selectors" By setting the &%log_selector%& global option, you can disable some of Exim's -default logging, or you can request additional logging. The value of +default logging to the main log, or you can request additional logging. The value of &%log_selector%& is made up of names preceded by plus or minus characters. For example: .code @@ -38809,18 +39271,19 @@ selection marked by asterisks: .irow &`address_rewrite`&   "address rewriting" .irow &`all_parents`&   "all parents in => lines" .irow &`arguments`&   "command line arguments" +.irow &`connection_id`&   "connection identifier" .irow &`connection_reject`& * "connection rejections" .irow &`delay_delivery`& * "immediate delivery delayed" .irow &`deliver_time`&   "time taken to attempt delivery" .irow &`delivery_size`&   "add &`S=`&&'nnn'& to => lines" .irow &`dkim`& * "DKIM verified domain on <= lines" -.irow &`dkim_verbose`&   "separate full DKIM verification result line, per signature" +.irow &`dkim_verbose`&   "separate full DKIM verification result line, per signature; DKIM signing" .irow &`dnslist_defer`& * "defers of DNS list (aka RBL) lookups" .irow &`dnssec`&   "DNSSEC secured lookups" .irow &`etrn`& * "ETRN commands" .irow &`host_lookup_failed`& * "as it says" .irow &`ident_timeout`&   "timeout for ident connection" -.irow &`incoming_interface`&   "local interface on <= and => lines" +.irow &`incoming_interface`&   "local interface & port on <= and => lines" .irow &`incoming_port`&   "remote port on <= lines" .irow &`lost_incoming_connection`& * "as it says (includes timeouts)" .irow &`millisec`&   "millisecond timestamps and RT,QT,DT,D times" @@ -38858,7 +39321,7 @@ selection marked by asterisks: .irow &`tls_peerdn`&   "TLS peer DN on <= and => lines" .irow &`tls_resumption`&   "append * to cipher field" .irow &`tls_sni`&   "TLS SNI on <= lines" -.irow &`unknown_in_list`&   "DNS lookup failed in list match" +.irow &`unknown_in_list`&   "lookup failed in list match" .irow &`all`&   "&*all of the above*&" .endtable See also the &%slow_lookup_log%& main configuration option, @@ -38904,6 +39367,12 @@ because the arguments are checked before the configuration file is read. The only way to log such cases is to interpose a script such as &_util/logargs.sh_& between the caller and Exim. .next +.cindex "log" "connection identifier" +&%connection_identifier%&: An identifier for the accepted connection is added to +connection start and end lines and to message accept lines. +The identifier is tagged by Ci=. +The value is PID-based, so will reset on reboot and will wrap. +.next .cindex "log" "connection rejections" &%connection_reject%&: A log entry is written whenever an incoming SMTP connection is rejected, for whatever reason. @@ -38934,6 +39403,8 @@ verifies successfully a tag of DKIM is added, with one of the verified domains. .cindex log "DKIM verification" .cindex DKIM "verification logging" &%dkim_verbose%&: A log entry is written for each attempted DKIM verification. +Also, on message delivery lines signing information (domain and selector) +is added, tagged with DKIM=. .next .cindex "log" "dnslist defer" .cindex "DNS list" "logging defer" @@ -39271,7 +39742,8 @@ added to the log line, preceded by SNI=. .next .cindex "log" "DNS failure in list" &%unknown_in_list%&: This setting causes a log entry to be written when the -result of a list match is failure because a DNS lookup failed. +result of a list match is failure because a DNS lookup failed, or because +a bad IP address was in the list. .endlist @@ -39325,6 +39797,7 @@ the next chapter. The utilities described here are: .irow &<>& &'exim_tidydb'& "clean up a hints database" .irow &<>& &'exim_fixdb'& "patch a hints database" .irow &<>& &'exim_lock'& "lock a mailbox file" +.irow &<>& &'exim_msgdate'& "Message Ids for humans (exim_msgdate)" .endtable Another utility that might be of use to sites with many MTAs is Tom Kistner's @@ -39826,18 +40299,20 @@ for remote hosts The &'misc'& database is used for .ilist -Serializing ETRN runs (when &%smtp_etrn_serialize%& is set) -.next Serializing delivery to a specific host (when &%serialize_hosts%& is set in an &(smtp)& transport) .next Limiting the concurrency of specific transports (when &%max_parallel%& is set in a transport) +.next +Recording EHLO-time facilities advertised by hosts +.next +Serializing ETRN runs (when &%smtp_etrn_serialize%& is set) .endlist -.section "exim_dumpdb" "SECTdumpdb" +.subsection "exim_dumpdb" "SECTdumpdb" .cindex "&'exim_dumpdb'&" The entire contents of a database are written to the standard output by the &'exim_dumpdb'& program, @@ -39879,7 +40354,7 @@ cross-references. -.section "exim_tidydb" "SECTtidydb" +.subsection "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 @@ -39928,7 +40403,7 @@ databases is likely to keep on increasing. -.section "exim_fixdb" "SECTfixdb" +.subsection "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 @@ -40048,9 +40523,16 @@ exim_lock -q /var/spool/mail/spqr \ .endd Note that if a command is supplied, it must be entirely contained within the second argument &-- hence the quotes. -.ecindex IIDutils +.section "Message Ids for humans (exim_msgdate)" "SECTexim_msgdate" +.cindex "exim_msgdate" +The &'exim_msgdate'& utility is written by Andrew Aitchison and included in the Exim distribution. +This Perl script converts an Exim Mesage ID back into a human readable form. +For details of &'exim_msgdate'&'s options, run &'exim_msgdate'& with the &%--help%& option. + +Section &<>& (Message identification) describes Exim Mesage IDs. +.ecindex IIDutils . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// @@ -41269,8 +41751,9 @@ Exim's DKIM implementation allows for .olist Signing outgoing messages: This function is implemented in the SMTP transport. It can co-exist with all other Exim features -(including transport filters) -except cutthrough delivery. +(including transport filters) except cutthrough delivery. +However, signing options may not depend on headers modified by +routers, the transport or a transport filter. .next Verifying signatures in incoming messages: This is implemented by an additional ACL (acl_smtp_dkim), which can be called several times per message, with @@ -41456,7 +41939,7 @@ variables here. .option dkim_sign_headers smtp string&!! "see below" If set, this option must expand to a colon-separated list of header names. -Headers with these names, or the absence or such a header, will be included +Headers with these names, or the absence of such a header, will be included in the message signature. When unspecified, the header names listed in RFC4871 will be used, whether or not each header is present in the message. @@ -41478,10 +41961,9 @@ name will be appended. .option dkim_timestamps smtp integer&!! unset This option controls the inclusion of timestamp information in the signature. If not set, no such information will be included. -Otherwise, must be an unsigned number giving an offset in seconds from the current time -for the expiry tag -(eg. 1209600 for two weeks); -both creation (t=) and expiry (x=) tags will be included. +Otherwise, must be an unsigned number giving an offset in seconds from the +current time for the expiry tag (e.g. 1209600 for two weeks); both creation +(t=) and expiry (x=) tags will be included unless the offset is 0 (no expiry). RFC 6376 lists these tags as RECOMMENDED. @@ -41491,8 +41973,9 @@ RFC 6376 lists these tags as RECOMMENDED. Verification of DKIM signatures in SMTP incoming email is done for all messages for which an ACL control &%dkim_disable_verify%& has not been set. + .cindex DKIM "selecting signature algorithms" -Individual classes of signature algorithm can be ignored by changing +Individual classes of DKIM signature algorithm can be ignored by changing the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&. The &%dkim_verify_minimal%& option can be set to cease verification processing for a message once the first passing signature is found. @@ -41505,7 +41988,7 @@ For most purposes the default option settings suffice and the remainder of this section can be ignored. The results of verification are made available to the -&%acl_smtp_dkim%& ACL, which can examine and modify them. +&%acl_smtp_dkim%& ACL, which (for complex needs) can examine and modify them. A missing ACL definition defaults to accept. By default, the ACL is called once for each syntactically(!) correct signature in the incoming message. @@ -41570,6 +42053,12 @@ an identity. This is one of the list items from the expanded main option &%dkim_verify_signers%& (see above). .vitem &%$dkim_verify_status%& +So long as a DKIM ACL is defined +(it need do no more than accept, which is the default), +after all the DKIM ACL runs have completed, the value becomes a +colon-separated list of the values after each run. +The value is maintained for the MIME, PRDR and DATA ACLs. + Within the DKIM ACL, a string describing the general status of the signature. One of .ilist @@ -41598,11 +42087,6 @@ hash-method or key-size: set dkim_verify_reason = hash too weak or key too short .endd -So long as a DKIM ACL is defined (it need do no more than accept), -after all the DKIM ACL runs have completed, the value becomes a -colon-separated list of the values after each run. -This is maintained for the mime, prdr and data ACLs. - .vitem &%$dkim_verify_reason%& A string giving a little bit more detail when &%$dkim_verify_status%& is either "fail" or "invalid". One of @@ -41733,7 +42217,9 @@ In addition, two ACL conditions are provided: .vitem &%dkim_signers%& ACL condition that checks a colon-separated list of domains or identities for a match against the domain or identity that the ACL is currently verifying -(reflected by &%$dkim_cur_signer%&). This is typically used to restrict an ACL +(reflected by &%$dkim_cur_signer%&). +This condition is only usable in a DKIM ACL. +This is typically used to restrict an ACL verb to a group of domains or identities. For example: .code @@ -41749,7 +42235,16 @@ for that check for empty &$h_DKIM-Signature:$& in the data ACL. .vitem &%dkim_status%& ACL condition that checks a colon-separated list of possible DKIM verification -results against the actual result of verification. This is typically used +results against the actual result of verification, +given by &$dkim_verify_status$& if that is non-empty or "none" if empty. +This condition may be used in DKIM, MIME, PRDR and DATA ACLs. + +A basic verification might be: +.code +deny !dkim_status = pass:none:invalid +.endd + +A more complex use could be to restrict an ACL verb to a list of verification outcomes, for example: .code @@ -41762,6 +42257,10 @@ deny sender_domains = paypal.com:paypal.de The possible status keywords are: 'none','invalid','fail' and 'pass'. Please see the documentation of the &%$dkim_verify_status%& expansion variable above for more information of what they mean. + +The condition is true if the status +(or any of the list of status values) +is any one of the supplied list. .endlist @@ -41958,10 +42457,16 @@ The lookup will return the same result strings as can appear in .subsection "SRS (Sender Rewriting Scheme)" SECTSRS .cindex SRS "sender rewriting scheme" +.cindex VERP "variable envelope return path" 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 +It can also be used to identify a received bounce message as +likely (or not) having been trigged by a message from the +local system, and for identifying dead addresses in mailing lists. +It is one implementation of a VERP (Variable Envelope Return Path) method. + +SRS 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 @@ -41995,18 +42500,28 @@ encoding operation. If this value is empty the the expansion result will be empty. The third argument should be the recipient domain of the message when it arrived at this system. +All arguments are expanded before use. + +The result of the expansion is the replacement envelope-from (return path) +to be used. .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 first argument should be the recipient local part as it was received. The second argument is the site secret. +Both arguments are expanded before use. 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 +return false. +If it is, the condition will return true and the variable &$srs_recipient$& will be set to the decoded (original) value. + +If the second argument is empty then the condition returns true if +the first argument is in valid SRS formet, else false. +The variable &$srs_recipient$& is not set for this case. .endlist Example usage: @@ -42041,15 +42556,17 @@ Example usage: allow_fail data = :fail: Invalid SRS recipient address - #... further routers here + #... further routers here get inbound_srs-redirected recipients + # and any that were not SRS'd # 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 + # single-recipient so that $original_domain is valid max_rcpt = 1 + # modify the envelope from, for mails that we forward return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}} .endd @@ -42156,7 +42673,7 @@ the DATA acl. .subsection ACL SSECDMARCACL .cindex DMARC "ACL condition" -DMARC checks cam be run on incoming SMTP messages by using the +DMARC checks can be run on incoming SMTP messages by using the &"dmarc_status"& ACL condition in the DATA ACL. You are required to call the &"spf"& condition first in the ACLs, then the &"dmarc_status"& condition. Putting this condition in the ACLs is required in order @@ -42630,6 +43147,7 @@ The current list of events is: .itable all 0 0 4 25* left 10* center 15* center 50* left .row auth:fail after both "per driver per authentication attempt" .row dane:fail after transport "per connection" +.row dns:fail after both "per lookup" .row msg:complete after main "per message" .row msg:defer after transport "per message per delivery try" .row msg:delivery after transport "per recipient" @@ -42663,6 +43181,7 @@ with the event type: .itable all 0 0 2 20* left 80* left .row auth:fail "smtp response" .row dane:fail "failure reason" +.row dns:fail "failure reason, key and lookup-type" .row msg:defer "error string" .row msg:delivery "smtp confirmation message" .row msg:fail:internal "failure reason" @@ -42704,14 +43223,17 @@ All other message types ignore the result string, and no other use is made of it. For a tcp:connect event, if the connection is being made to a proxy -then the address and port variables will be that of the proxy and not -the target system. +then the &$host_address$& and &$host_port$& variables +will be that of the proxy and not the target system. For tls:cert events, if GnuTLS is in use this will trigger only per chain element received on the connection. For OpenSSL it will trigger for every chain element including those loaded locally. +For dns:fail events from dnsdb lookups, a &"defer_never"& option does not +affect the reporting of DNS_AGAIN. + . //////////////////////////////////////////////////////////////////////////// . ////////////////////////////////////////////////////////////////////////////