. Update the Copyright year (only) when changing content.
. /////////////////////////////////////////////////////////////////////////////
-.set previousversion "4.93"
+.set previousversion "4.94"
.include ./local_params
.set ACL "access control lists (ACLs)"
.set I " "
+.set drivernamemax "64"
+
.macro copyyear
2020
.endmacro
.macro index
.echo "** Don't use .index; use .cindex or .oindex or .vindex"
.endmacro
+
+
+. use this for a concept-index entry for a header line
+.macro chindex
+.cindex "&'$1'& header line"
+.cindex "header lines" $1
+.endmacro
. ////////////////////////////////////////////////////////////////////////////
. This chunk of literal XML implements index entries of the form "x, see y" and
. "x, see also y". However, the DocBook DTD doesn't allow <indexterm> entries
. at the top level, so we have to put the .chapter directive first.
+
+. These do not turn up in the HTML output, unfortunately. The PDF does get them.
. /////////////////////////////////////////////////////////////////////////////
.chapter "Introduction" "CHID1"
<secondary>failure report</secondary>
<see><emphasis>bounce message</emphasis></see>
</indexterm>
+<indexterm role="concept">
+ <primary>de-tainting</primary>
+ <see><emphasis>tainting, de-tainting</emphasis></see>
+</indexterm>
+<indexterm role="concept">
+ <primary>detainting</primary>
+ <see><emphasis>tainting, de-tainting</emphasis></see>
+</indexterm>
<indexterm role="concept">
<primary>dialup</primary>
<see><emphasis>intermittently connected hosts</emphasis></see>
<primary>zero, binary</primary>
<see><emphasis>binary zero</emphasis></see>
</indexterm>
+<indexterm role="concept">
+ <primary>headers</primary>
+ <see><emphasis>header lines</emphasis></see>
+</indexterm>
.literal off
.next
Individual routers can be explicitly skipped when running the routers to
check an address given in the SMTP EXPN command (see the &%expn%& option).
+
.next
If the &%domains%& option is set, the domain of the address must be in the set
of domains that it defines.
+.new
+.cindex "tainted data" "de-tainting"
+A match verifies the variable &$domain$& (which carries tainted data)
+and assigns an untainted value to the &$domain_data$& variable.
+Such an untainted value is often needed in the transport.
+For specifics of the matching operation and the resulting untainted value,
+refer to section &<<SECTdomainlist>>&.
+
+When an untainted value is wanted, use this option
+rather than the generic &%condition%& option.
+.wen
+
.next
.vindex "&$local_part_prefix$&"
.vindex "&$local_part_prefix_v$&"
.vindex "&$local_part_suffix_v$&"
.cindex affix "router precondition"
If the &%local_parts%& option is set, the local part of the address must be in
-the set of local parts that it defines. If &%local_part_prefix%& or
+the set of local parts that it defines.
+.new
+A match verifies the variable &$local_part$& (which carries tainted data)
+and assigns an untainted value to the &$local_part_data$& variable.
+Such an untainted value is often needed in the transport.
+For specifics of the matching operation and the resulting untainted value,
+refer to section &<<SECTlocparlis>>&.
+
+When an untainted value is wanted, use this option
+rather than the generic &%condition%& option.
+.wen
+
+If &%local_part_prefix%& or
&%local_part_suffix%& is in use, the prefix or suffix is removed from the local
part before this check. If you want to do precondition tests on local parts
that include affixes, you can do so by using a &%condition%& option (see below)
-.new
that uses the variables &$local_part$&, &$local_part_prefix$&,
&$local_part_prefix_v$&, &$local_part_suffix$&
and &$local_part_suffix_v$& as necessary.
-.wen
+
.next
.vindex "&$local_user_uid$&"
.vindex "&$local_user_gid$&"
local user are placed in &$local_user_uid$& and &$local_user_gid$& and the
user's home directory is placed in &$home$&; these values can be used in the
remaining preconditions.
+
.next
If the &%router_home_directory%& option is set, it is expanded at this point,
because it overrides the value of &$home$&. If this expansion were left till
later, the value of &$home$& as set by &%check_local_user%& would be used in
subsequent tests. Having two different values of &$home$& in the same router
could lead to confusion.
+
.next
If the &%senders%& option is set, the envelope sender address must be in the
set of addresses that it defines.
+
.next
If the &%require_files%& option is set, the existence or non-existence of
specified files is tested.
+
.next
.cindex "customizing" "precondition"
If the &%condition%& option is set, it is evaluated and tested. This option
uses an expanded string to allow you to set up your own custom preconditions.
Expanded strings are described in chapter &<<CHAPexpand>>&.
+
+.new
+Note that while using
+this option for address matching technically works,
+it does not set any de-tainted values.
+Such values are often needed, either for router-specific options or
+for transport options.
+Using the &%domains%& and &%local_parts%& options is usually the most
+convenient way to obtain them.
+.wen
.endlist
See the &%untrusted_set_sender%& option for a way of permitting non-trusted
users to set envelope senders.
-.cindex "&'From:'& header line"
-.cindex "&'Sender:'& header line"
-.cindex "header lines" "From:"
-.cindex "header lines" "Sender:"
+.chindex From:
+.chindex Sender:
For a trusted user, there is never any check on the contents of the &'From:'&
header line, and a &'Sender:'& line is never added. Furthermore, any existing
&'Sender:'& line in incoming local (non-TCP/IP) messages is not removed.
.cindex "Solaris" "&'mail'& command"
.cindex "dot" "in incoming non-SMTP message"
This option, which has the same effect as &%-oi%&, specifies that a dot on a
-line by itself should not terminate an incoming, non-SMTP message. I can find
-no documentation for this option in Solaris 2.4 Sendmail, but the &'mailx'&
-command in Solaris 2.4 uses it. See also &%-ti%&.
+line by itself should not terminate an incoming, non-SMTP message.
+Solaris 2.4 (SunOS 5.4) Sendmail has a similar &%-i%& processing option
+&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf),
+p. 1M-529), and therefore a &%-oi%& command line option, which both are used
+by its &'mailx'& command.
.vitem &%-L%&&~<&'tag'&>
.oindex "&%-L%&"
active (in the middle of a delivery attempt), it is not altered. This option
can be used only by an admin user.
-.vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&~<&'sequence&~number'&>&&&
+.vitem "&%-MC%&&~<&'transport'&>&~<&'hostname'&>&&&
+ &~<&'host&~IP'&>&&&
+ &~<&'sequence&~number'&>&&&
&~<&'message&~id'&>"
.oindex "&%-MC%&"
.cindex "SMTP" "passed connection"
by Exim in conjunction with the &%-MC%& option. It signifies that the
remote host supports the ESMTP &_DSN_& extension.
-.new
.vitem &%-MCd%&
.oindex "&%-MCd%&"
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the &%-d%& option
to pass on an information string on the purpose of the process.
-.wen
.vitem &%-MCG%&&~<&'queue&~name'&>
.oindex "&%-MCG%&"
by Exim in conjunction with the &%-MC%& option. It signifies that a
remote host supports the ESMTP &_CHUNKING_& extension.
+.new
+.vitem &%-MCL%&
+.oindex "&%-MCL%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option. It signifies that the server to
+which Exim is connected advertised limits on numbers of mails, recipients or
+recipient domains.
+The limits are given by the following three arguments.
+.wen
+
.vitem &%-MCP%&
.oindex "&%-MCP%&"
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the &%-MC%& option. It signifies that the server to
which Exim is connected supports pipelining.
+.new
+.vitem &%-MCp%&
+.oindex "&%-MCp%&"
+This option is not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MC%& option. It signifies that the connection
+t a remote server is via a SOCKS proxy, using addresses and ports given by
+the following four arguments.
+.wen
+
.vitem &%-MCQ%&&~<&'process&~id'&>&~<&'pipe&~fd'&>
.oindex "&%-MCQ%&"
This option is not intended for use by external callers. It is used internally
signals the final completion of the sequence of processes that are passing
messages through the same SMTP connection.
+.new
+.vitem &%-MCq%&&~<&'recipient&~address'&>&~<&'size'&>
+.oindex "&%-MCq%&"
+This option is not intended for use by external callers. It is used internally
+by Exim to implement quota checking for local users.
+.wen
+
.vitem &%-MCS%&
.oindex "&%-MCS%&"
This option is not intended for use by external callers. It is used internally
by Exim in conjunction with the &%-MC%& option, and passes on the fact that the
host to which Exim is connected supports TLS encryption.
+.new
+.vitem &%-MCr%&&~<&'SNI'&> &&&
+ &%-MCs%&&~<&'SNI'&>
+.oindex "&%-MCs%&"
+.oindex "&%-MCr%&"
+These options are not intended for use by external callers. It is used internally
+by Exim in conjunction with the &%-MCt%& option, and passes on the fact that
+a TLS Server Name Indication was sent as part of the channel establishment.
+The argument gives the SNI string.
+The "r" variant indicates a DANE-verified connection.
+.wen
+
.vitem &%-MCt%&&~<&'IP&~address'&>&~<&'port'&>&~<&'cipher'&>
.oindex "&%-MCt%&"
This option is not intended for use by external callers. It is used internally
.vitem &%-m%&
.oindex "&%-m%&"
-This is apparently a synonym for &%-om%& that is accepted by Sendmail, so Exim
-treats it that way too.
+This is a synonym for &%-om%& that is accepted by Sendmail
+(&url(https://docs.oracle.com/cd/E19457-01/801-6680-1M/801-6680-1M.pdf)
+p. 1M-258), so Exim treats it that way too.
.vitem &%-N%&
.oindex "&%-N%&"
without &%-bd%&, this is the only way of causing Exim to write a pid file,
because in those cases, the normal pid file is not used.
-.new
.vitem &%-oPX%&
.oindex "&%-oPX%&"
.cindex "pid (process id)" "of daemon"
The daemon uses it when terminating due to a SIGTEM, possibly in
combination with &%-oP%&&~<&'path'&>.
It causes the pid file to be removed.
-.wen
.vitem &%-or%&&~<&'time'&>
.oindex "&%-or%&"
in chapter &<<CHAPinterfaces>>&. When &%-oX%& is used to start a daemon, no pid
file is written unless &%-oP%& is also present to specify a pid filename.
+.new
+.vitem &%-oY%&
+.oindex &%-oY%&
+.cindex "daemon notifier socket"
+This option controls the creation of an inter-process communications endpoint
+by the Exim daemon.
+It is only relevant when the &%-bd%& (start listening daemon) option is also
+given.
+Normally the daemon creates this socket, unless a &%-oX%& and &*no*& &%-oP%&
+option is also present.
+If this option is given then the socket will not be created. This could be
+required if the system is running multiple daemons.
+
+The socket is currently used for
+.ilist
+fast ramp-up of queue runner processes
+.next
+obtaining a current queue size
+.endlist
+.wen
+
.vitem &%-pd%&
.oindex "&%-pd%&"
.cindex "Perl" "starting the interpreter"
.cindex "queue" "routing"
.cindex "routing" "whole queue before delivery"
.cindex "first pass routing"
+.cindex "queue runner" "two phase"
An option starting with &%-qq%& requests a two-stage queue run. In the first
stage, the queue is scanned as if the &%queue_smtp_domains%& option matched
every domain. Addresses are routed, local deliveries happen, but no remote
transports are run.
-.new
Performance will be best if the &%queue_run_in_order%& option is false.
-.wen
+If that is so and the &%queue_fast_ramp%& option is true then
+in the first phase of the run,
+once a threshold number of messages are routed for a given host,
+a delivery process is forked in parallel with the rest of the scan.
.cindex "hints database" "remembering routing"
The hints database that remembers which messages are waiting for specific hosts
.vitem &%-t%&
.oindex "&%-t%&"
.cindex "recipient" "extracting from header lines"
-.cindex "&'Bcc:'& header line"
-.cindex "&'Cc:'& header line"
-.cindex "&'To:'& header line"
+.chindex Bcc:
+.chindex Cc:
+.chindex To:
When Exim is receiving a locally-generated, non-SMTP message on its standard
input, the &%-t%& option causes the recipients of the message to be obtained
from the &'To:'&, &'Cc:'&, and &'Bcc:'& header lines in the message instead of
contains two IP addresses, the IPv4 address 127.0.0.1 and the IPv6 address ::1.
&*Note*&: Although leading and trailing white space is ignored in individual
-list items, it is not ignored when parsing the list. The space after the first
-colon in the example above is necessary. If it were not there, the list would
+list items, it is not ignored when parsing the list. The spaces around the first
+colon in the example above are necessary. If they were not there, the list would
be interpreted as the two items 127.0.0.1:: and 1.
.section "Changing list separators" "SECTlistsepchange"
imposes a security risk (e.g. PATH). There are two lists:
&%keep_environment%& for the variables to import as they are, and
&%add_environment%& for variables we want to set to a fixed value.
-Note that TZ is handled separately, by the $%timezone%$ runtime
+Note that TZ is handled separately, by the &%timezone%& runtime
option and by the TIMEZONE_DEFAULT buildtime option.
.code
# keep_environment = ^LDAP
# request with your smarthost provider to get things fixed:
hosts_require_tls = *
tls_verify_hosts = *
- # As long as tls_verify_hosts is enabled, this won't matter, but if you
- # have to comment it out then this will at least log whether you succeed
- # or not:
+ # As long as tls_verify_hosts is enabled, this this will have no effect,
+ # but if you have to comment it out then this will at least log whether
+ # you succeed or not:
tls_try_verify_hosts = *
#
# The SNI name should match the name which we'll expect to verify;
This &(appendfile)& transport is used for local delivery to user mailboxes in
traditional BSD mailbox format.
-.new
We prefer to avoid using &$local_part$& directly to define the mailbox filename,
as it is provided by a potential bad actor.
Instead we use &$local_part_data$&,
the result of looking up &$local_part$& in the user database
(done by using &%check_local_user%& in the the router).
-.wen
By default &(appendfile)& runs under the uid and gid of the
local user, which requires the sticky bit to be set on the &_/var/mail_&
lookup. Lookups of this type are conditional expansion items. Different results
can be defined for the cases of lookup success and failure. See chapter
&<<CHAPexpand>>&, where string expansions are described in detail.
-The key for the lookup is specified as part of the string expansion.
+The key for the lookup is &*specified*& as part of the string expansion.
.next
Lists of domains, hosts, and email addresses can contain lookup requests as a
way of avoiding excessively long linear lists. In this case, the data that is
returned by the lookup is often (but not always) discarded; whether the lookup
succeeds or fails is what really counts. These kinds of list are described in
chapter &<<CHAPdomhosaddlists>>&.
-The key for the lookup is given by the context in which the list is expanded.
+The key for the lookup is &*implicit*&,
+given by the context in which the list is expanded.
.endlist
String expansions, lists, and lookups interact with each other in such a way
In the second example, the lookup is a single item in a domain list. It causes
Exim to use a lookup to see if the domain that is being processed can be found
-in the file. The file could contains lines like this:
+in the file.
+The file could contains lines like this:
.code
domain1:
domain2:
The lookup type may optionally be followed by a comma
and a comma-separated list of options.
Each option is a &"name=value"& pair.
-Whether an option is meaningful depands on the lookup type.
+Whether an option is meaningful depends on the lookup type.
+
+All lookups support the option &"cache=no_rd"&.
+If this is given then the cache that Exim manages for lookup results
+is not checked before doing the lookup.
+The result of the lookup is still written to the cache.
.wen
The rest of this chapter describes the different lookup types that are
The &'single-key'& type requires the specification of a file in which to look,
and a single key to search for. The key must be a non-empty string for the
lookup to succeed. The lookup type determines how the file is searched.
-.new
.cindex "tainted data" "single-key lookups"
The file string may not be tainted
(either underlying implementation or cached value)
returns data, the result is replaced with a non-tainted
version of the lookup key.
-.wen
+.cindex "tainted data" "de-tainting"
.next
.cindex "query-style lookup" "definition of"
The &'query-style'& type accepts a generalized database query. No particular
.cindex "lookup" "dsearch"
.cindex "dsearch lookup type"
&(dsearch)&: The given file must be an
-.new
absolute
-.wen
directory path; this is searched for an entry
whose name is the key by calling the &[lstat()]& function.
The key may not
contain any forward slash characters.
If &[lstat()]& succeeds then so does the lookup.
-.new
.cindex "tainted data" "dsearch result"
The result is regarded as untainted.
.endd
The default matching is for any entry type, including directories
and symlinks.
-.wen
An example of how this
lookup can be used to support virtual domains is given in section
&*Warning 3*&: Do not use an IPv4-mapped IPv6 address for a key; use the
IPv4, in dotted-quad form. (Exim converts IPv4-mapped IPv6 addresses to this
notation before executing the lookup.)
+
+.new
+One option is supported, "ret=full", to request the return of the entire line
+rather than omitting the key porttion.
+Note however that the key portion will have been de-quoted.
+.wen
+
.next
.cindex lookup json
.cindex json "lookup type"
or array; for the latter two a string-representation of the JSON
is returned.
For elements of type string, the returned value is de-quoted.
+
+
+.new
+.next
+.cindex LMDB
+.cindex lookup lmdb
+.cindex database lmdb
+&(lmdb)&: The given file is an LMDB database.
+LMDB is a memory-mapped key-value store,
+with API modeled loosely on that of BerkeleyDB.
+See &url(https://symas.com/products/lightning-memory-mapped-database/)
+for the feature set and operation modes.
+
+Exim provides read-only access via the LMDB C library.
+The library can be obtained from &url(https://github.com/LMDB/lmdb)
+or your operating system package repository.
+To enable LMDB support in Exim set LOOKUP_LMDB=yes in &_Local/Makefile_&.
+
+You will need to separately create the LMDB database file,
+possibly using the &"mdb_load"& utility.
+.wen
+
+
.next
.cindex "linear search"
.cindex "lookup" "lsearch"
.cindex "sqlite lookup type"
.cindex "lookup" "sqlite"
&(sqlite)&: The format of the query is
-new
-an optional filename
-.wen
-followed by an SQL statement
-that is passed to an SQLite database. See section &<<SECTsqlite>>&.
+an SQL statement that is passed to an SQLite database. See section &<<SECTsqlite>>&.
.next
&(testdb)&: This is a lookup type that is used for testing Exim. It is
escapes whitespace and backslash characters with a backslash.
.section "Specifying the server in the query" "SECTspeserque"
-.new
For MySQL, PostgreSQL and Redis lookups (but not currently for Oracle and InterBase),
it is possible to specify a list of servers with an individual query. This is
done by appending a comma-separated option to the query type:
.display
-.endd
&`,servers=`&&'server1:server2:server3:...'&
-.wen
+.endd
Each item in the list may take one of two forms:
.olist
If it contains no slashes it is assumed to be just a host name. The appropriate
${lookup pgsql,servers=master/db/name/pw {UPDATE ...} }
.endd
-.new
-An older syntax places the servers speciification before the qury,
+An older syntax places the servers specification before the query,
semicolon separated:
.code
${lookup mysql{servers=master; UPDATE ...} }
The new version avoids potential issues with tainted
arguments in the query, for explicit expansion.
&*Note*&: server specifications in list-style lookups are still problematic.
-.wen
.section "Special MySQL features" "SECID73"
.new
.oindex &%sqlite_dbfile%&
-The preferred way of specifying the file is by using the
-&%sqlite_dbfile%& option, set to
-an absolute path.
+There are two ways of
+specifying the file.
+The first is is by using the &%sqlite_dbfile%& main option.
+The second, which allows separate files for each query,
+is to use an option appended, comma-separated, to the &"sqlite"&
+lookup type word. The option is the word &"file"&, then an equals,
+then the filename.
+The filename in this case cannot contain whitespace or open-brace charachters.
.wen
+
A deprecated method is available, prefixing the query with the filename
separated by white space.
-This means that the path name cannot contain white space.
+This means that
.cindex "tainted data" "sqlite file"
-It also means that the query cannot use any tainted values, as that taints
+the query cannot use any tainted values, as that taints
the entire query including the filename - resulting in a refusal to open
the file.
-.new
+In all the above cases the filename must be an absolute path.
+
Here is a lookup expansion example:
.code
sqlite_dbfile = /some/thing/sqlitedb
domainlist relay_to_domains = sqlite;\
select * from relays where ip='$sender_host_address';
.endd
-.wen
The only character affected by the &%quote_sqlite%& operator is a single
quote, which it doubles.
-.new
.section "Results of list checking" SECTlistresults
The primary result of doing a list check is a truth value.
In some contexts additional information is stored
A &%local_parts%& router option or &%local_parts%& ACL condition
will store a result in the &$local_part_data$& variable.
.vitem domains
+.new
A &%domains%& router option or &%domains%& ACL condition
+will store a result in the &$domain_data$& variable.
+.wen
.vitem senders
A &%senders%& router option or &%senders%& ACL condition
will store a result in the &$sender_data$& variable.
The detail of the additional information depends on the
type of match and is given below as the &*value*& information.
-.wen
where &'x.y'& does not match. It's best to avoid negation altogether in
referenced lists if you can.
-.new
.cindex "hiding named list values"
.cindex "named lists" "hiding value of"
Some named list definitions may contain sensitive data, for example, passwords for
.code
hide domainlist filter_for_domains = ldap;PASS=secret ldap::/// ...
.endd
-.wen
Named lists may have a performance advantage. When Exim is routing an
possible to use the same configuration file on several different hosts that
differ only in their names.
-.new
The value for a match will be the primary host name.
-.wen
.next
In today's Internet, the use of domain literals is controversial;
see the &%allow_domain_literals%& main option.
-.new
The value for a match will be the string &`@[]`&.
-.wen
.next
domains = <? @mx_any/ignore=<;127.0.0.1;::1 ? \
an.other.domain ? ...
.endd
-.new
The value for a match will be the list element string (starting &`@mx_`&).
-.wen
.next
list item such as &`*key.ex`& matches &'donkey.ex'& as well as
&'cipher.key.ex'&.
-.new
The value for a match will be the list element string (starting with the asterisk).
Additionally, &$0$& will be set to the matched string
and &$1$& to the variable portion which the asterisk matched.
-.wen
.next
.cindex "regular expressions" "in domain list"
it is not to be expanded (unless you really do want to build a regular
expression by expansion, of course).
-.new
The value for a match will be the list element string (starting with the circumflex).
Additionally, &$0$& will be set to the string matching the regular expression,
and &$1$& (onwards) to any submatches identified by parentheses.
-.wen
.cindex "tainted data" "de-tainting"
The value will be untainted.
+.new
+&*Note*&: If the data result of the lookup (as opposed to the key)
+is empty, then this empty value is stored in &$domain_data$&.
+The option to return the key for the lookup, as the value,
+may be what is wanted.
+.wen
+
.next
Any of the single-key lookup type names may be preceded by
The value will be untainted.
.next
-.new
If the pattern starts with the name of a lookup type
of either kind (single-key or query-style) it may be
followed by a comma and options,
The options are lookup-type specific and consist of a comma-separated list.
-Each item starts with a tag and and equals "=".
-.wen
+Each item starts with a tag and and equals "=" sign.
.next
.cindex "domain list" "matching literal domain name"
.cindex "tainted data" "de-tainting"
Note that this is commonly untainted
(depending on the way the list was created).
+Specifically, explicit text in the configuration file in not tainted.
This is a useful way of obtaining an untainted equivalent to
the domain, for later operations.
+
+However if the list (including one-element lists)
+is created by expanding a variable containing tainted data,
+it is tainted and so will the match value be.
.endlist
.endd
.next
.cindex "CIDR notation"
-If the pattern is an IP address followed by a slash and a mask length (for
-example 10.11.42.0/24), it is matched against the IP address of the subject
-host under the given mask. This allows, an entire network of hosts to be
+If the pattern is an IP address followed by a slash and a mask length, for
+example
+.code
+10.11.42.0/24
+.endd
+, it is matched against the IP address of the subject
+host under the given mask. This allows an entire network of hosts to be
included (or excluded) by a single item. The mask uses CIDR notation; it
specifies the number of address bits that must match, starting from the most
significant end of the address.
.section "Local part lists" "SECTlocparlis"
.cindex "list" "local part list"
.cindex "local part" "list"
+These behave in the same way as domain and host lists, with the following
+changes:
+
Case-sensitivity in local part lists is handled in the same way as for address
lists, as just described. The &"+caseful"& item can be used if required. In a
setting of the &%local_parts%& option in a router with &%caseful_local_part%&
conditions do not expand some of the brace-delimited branches, for security
reasons,
.cindex "tainted data" expansion
+.cindex "tainted data" definition
.cindex expansion "tainted data"
and expansion of data deriving from the sender (&"tainted data"&)
-is not permitted.
+.new
+is not permitted (including acessing a file using a tainted name).
+The main config option &%allow_insecure_tainted_data%& can be used as
+mitigation during uprades to more secure configurations.
+.wen
+
+.new
+Common ways of obtaining untainted equivalents of variables with
+tainted values
+.cindex "tainted data" "de-tainting"
+come down to using the tainted value as a lookup key in a trusted database.
+This database could be the filesystem structure,
+or the password file,
+or accessed via a DBMS.
+Specific methods are indexed under &"de-tainting"&.
+.wen
.vitem "&*${authresults{*&<&'authserv-id'&>&*}}*&"
.cindex authentication "results header"
-.cindex headers "authentication-results:"
+.chindex Authentication-Results:
.cindex authentication "expansion item"
This item returns a string suitable for insertion as an
&'Authentication-Results:'&
Header lines that are added in a RCPT ACL (for example)
are saved until the message's incoming header lines are available, at which
point they are added.
-When any of the above ACLs ar
+When any of the above ACLs are
running, however, header lines added by earlier ACLs are visible.
Upper case and lower case letters are synonymous in header names. If the
those headers that contain lists of addresses, a comma is also inserted at the
junctions between headers. This does not happen for the &%rheader%& expansion.
-.new
-.cindex "tainted data"
+.cindex "tainted data" "message headers"
When the headers are from an incoming message,
the result of expanding any of these variables is tainted.
-.wen
.vitem &*${hmac{*&<&'hashname'&>&*}{*&<&'secret'&>&*}{*&<&'string'&>&*}}*&
You can use &`fail`& instead of {<&'string3'&>} as in a string extract.
-.vitem "&*${lookup{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
- {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
-This is the first of one of two different types of lookup item, which are both
-described in the next item.
+.new
+.vitem &*${listquote{*&<&'separator'&>&*}{*&<&'string'&>&*}}*&
+.cindex quoting "for list"
+.cindex list quoting
+This item doubles any occurrence of the separator character
+in the given string.
+An empty string is replaced with a single space.
+This converts the string into a safe form for use as a list element,
+in a list using the given separator.
+.wen
+
-.vitem "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
+.vitem "&*${lookup&~{*&<&'key'&>&*}&~*&<&'search&~type'&>&*&~&&&
+ {*&<&'file'&>&*}&~{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&" &&&
+ "&*${lookup&~*&<&'search&~type'&>&*&~{*&<&'query'&>&*}&~&&&
{*&<&'string1'&>&*}&~{*&<&'string2'&>&*}}*&"
.cindex "expansion" "lookup in"
.cindex "file" "lookups"
name of the subroutine, is nine.
The return value of the subroutine is inserted into the expanded string, unless
-the return value is &%undef%&. In that case, the expansion fails in the same
-way as an explicit &"fail"& on a lookup item. The return value is a scalar.
-Whatever you return is evaluated in a scalar context. For example, if you
-return the name of a Perl vector, the return value is the size of the vector,
+the return value is &%undef%&. In that case, the entire expansion is
+forced to fail, in the same way as an explicit &"fail"& on a lookup item
+does (see section &<<SECTforexpfai>>&). Whatever you return is evaluated
+in a scalar context, thus the return value is a scalar. For example, if you
+return a Perl vector, the return value is the size of the vector,
not its contents.
If the subroutine exits by calling Perl's &%die%& function, the expansion fails
.cindex "expansion" "inserting an entire file"
.cindex "file" "inserting into expansion"
.cindex "&%readfile%& expansion item"
-The filename and end-of-line string are first expanded separately. The file is
+The filename and end-of-line (eol) string are first expanded separately. The file is
then read, and its contents replace the entire item. All newline characters in
the file are replaced by the end-of-line string if it is present. Otherwise,
newlines are left in the string.
Only a single host name may be given, but if looking it up yields more than
one IP address, they are each tried in turn until a connection is made. For
both kinds of socket, Exim makes a connection, writes the request string
-unless it is an empty string; and no terminating NUL is ever sent)
+(unless it is an empty string; no terminating NUL is ever sent)
and reads from the socket until an end-of-file
is read. A timeout of 5 seconds is applied. Additional, optional arguments
extend what can be done. Firstly, you can vary the timeout. For example:
${readsocket{/socket/name}{request string}{3s:shutdown=no}}
.endd
-.new
The following option names are recognised:
.ilist
&*cache*&
Values are &"yes"& or &"no"& (the default).
If it is enabled, a shutdown as descripbed above is never done.
.endlist
-.wen
A fourth argument allows you to change any newlines that are in the data
will sort an MX lookup into priority order.
+
+.new
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+SRS encoding. See SECT &<<SECTSRS>>& for details.
+.wen
+
+
+
.vitem &*${substr{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "&%substr%& expansion item"
.cindex "substring extraction"
.vitem &*${escape8bit:*&<&'string'&>&*}*&
.cindex "expansion" "escaping 8-bit characters"
.cindex "&%escape8bit%& expansion item"
-If the string contains and characters with the most significant bit set,
+If the string contains any characters with the most significant bit set,
they are converted to escape sequences starting with a backslash.
Backslashes and DEL characters are also converted.
and selects address-, domain-, host- or localpart- lists to search among respectively.
Otherwise all types are searched in an undefined order and the first
matching list is returned.
+.new
+&*Note*&: Neither string-expansion of lists referenced by named-list syntax elements,
+nor expansion of lookup elements, is done by the &%listnamed%& operator.
+.wen
.vitem &*${local_part:*&<&'string'&>&*}*&
The parsing correctly handles SMTPUTF8 Unicode in the string.
-.vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
+.vitem &*${mask:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*& &&&
+ &*${mask_n:*&<&'IP&~address'&>&*/*&<&'bit&~count'&>&*}*&
.cindex "masked IP address"
.cindex "IP address" "masking"
.cindex "CIDR notation"
.code
${mask:10.111.131.206/28}
.endd
-returns the string &"10.111.131.192/28"&. Since this operation is expected to
-be mostly used for looking up masked addresses in files, the result for an IPv6
+returns the string &"10.111.131.192/28"&.
+
+Since this operation is expected to
+be mostly used for looking up masked addresses in files, the
+.new
+normal
+.wen
+result for an IPv6
address uses dots to separate components instead of colons, because colon
terminates a key string in lsearch files. So, for example,
.code
.code
3ffe.ffff.836f.0a00.000a.0800.2000.0000/99
.endd
+.new
+If the optional form &*mask_n*& is used, IPv6 address result are instead
+returned in normailsed form, using colons and with zero-compression.
+.wen
Letters in IPv6 addresses are always output in lower case.
.cindex "expansion" "string length"
.cindex "string" "length in expansion"
.cindex "&%strlen%& expansion item"
-The item is replace by the length of the expanded string, expressed as a
+The item is replaced by the length of the expanded string, expressed as a
decimal number. &*Note*&: Do not confuse &%strlen%& with &%length%&.
All measurement is done in bytes and is not UTF-8 aware.
is done by calling the &[stat()]& function. The use of the &%exists%& test in
users' filter files may be locked out by the system administrator.
+.new
+&*Note:*& Testing a path using this condition is not a sufficient way of
+de-tainting it.
+Consider using a dsearch lookup.
+.wen
+
.vitem &*first_delivery*&
.cindex "delivery" "first"
.cindex "first delivery"
case-independent.
Case and collation order are defined per the system C locale.
+
+.new
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+SRS decode. See SECT &<<SECTSRS>>& for details.
+.wen
+
+
.vitem &*inlist&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*& &&&
&*inlisti&~{*&<&'string1'&>&*}{*&<&'string2'&>&*}*&
.cindex "string" "comparison"
There can be problems if any of the strings are permitted to contain colon
characters. In the usual way, these have to be doubled to avoid being taken as
-separators. If the data is being inserted from a variable, the &%sg%& expansion
-item can be used to double any existing colons. For example, the configuration
+separators.
+The &%listquote%& expansion item can be used for this.
+For example, the configuration
of a LOGIN authenticator might contain this setting:
.code
-server_condition = ${if pam{$auth1:${sg{$auth2}{:}{::}}}}
-.endd
-For a PLAIN authenticator you could use:
-.code
-server_condition = ${if pam{$auth2:${sg{$auth3}{:}{::}}}}
+server_condition = ${if pam{$auth1:${listquote{:}{$auth2}}}}
.endd
In some operating systems, PAM authentication can be done only from a process
running as root. Since Exim is running as the Exim user when receiving
.vitem &$acl_verify_message$&
.vindex "&$acl_verify_message$&"
After an address verification has failed, this variable contains the failure
-message. It retains its value for use in subsequent modifiers. The message can
-be preserved by coding like this:
+message. It retains its value for use in subsequent modifiers of the verb.
+The message can be preserved by coding like this:
.code
warn !verify = sender
set acl_m0 = $acl_verify_message
You can use &$acl_verify_message$& during the expansion of the &%message%& or
&%log_message%& modifiers, to include information about the verification
failure.
+.new
+&*Note*&: The variable is cleared at the end of processing the ACL verb.
+.wen
.vitem &$address_data$&
.vindex "&$address_data$&"
When, as a result of aliasing or forwarding, a message is directed to a pipe,
this variable holds the pipe command when the transport is running.
-.vitem "&$auth1$& &-- &$auth3$&"
+.vitem "&$auth1$& &-- &$auth4$&"
.vindex "&$auth1$&, &$auth2$&, etc"
These variables are used in SMTP authenticators (see chapters
&<<CHAPplaintext>>&&--&<<CHAPtlsauth>>&). Elsewhere, they are empty.
the complete argument of the ETRN command (see section &<<SECTETRN>>&).
.endlist
-.new
.cindex "tainted data"
If the origin of the data is an incoming message,
-the result of expanding this variable is tainted.
-When un untainted version is needed, one should be obtained from
+the result of expanding this variable is tainted and may not
+be further expanded or used as a filename.
+When an untainted version is needed, one should be obtained from
looking up the value in a local (therefore trusted) database.
Often &$domain_data$& is usable in this role.
-.wen
.vitem &$domain_data$&
.vindex "&$domain_data$&"
-When the &%domains%& option on a router matches a domain by
-means of a lookup, the data read by the lookup is available during the running
-of the router as &$domain_data$&. In addition, if the driver routes the
+When the &%domains%& condition on a router
+.new
+or an ACL
+matches a domain
+against a list, the match value is copied to &$domain_data$&.
+This is an enhancement over previous versions of Exim, when it only
+applied to the data read by a lookup.
+For details on match values see section &<<SECTlistresults>>& et. al.
+.wen
+
+If the router routes the
address to a transport, the value is available in that transport. If the
transport is handling multiple addresses, the value from the first address is
used.
-&$domain_data$& is also set when the &%domains%& condition in an ACL matches a
-domain by means of a lookup. The data read by the lookup is available during
-the rest of the ACL statement. In all other situations, this variable expands
-to nothing.
+&$domain_data$& set in an ACL is available during
+the rest of the ACL statement.
.vitem &$exim_gid$&
.vindex "&$exim_gid$&"
because a message may have many recipients and the system filter is called just
once.
-.new
.cindex "tainted data"
If the origin of the data is an incoming message,
-the result of expanding this variable is tainted.
+the result of expanding this variable is tainted and
+may not be further expanded or used as a filename.
&*Warning*&: the content of this variable is usually provided by a potential
attacker.
Often &$local_part_data$& is usable in this role.
If needed, use a router &%address_data%& or &%set%& option for
the retrieved data.
-.wen
When a message is being delivered to a file, pipe, or autoreply transport as a
result of aliasing or forwarding, &$local_part$& is set to the local part of
.vitem &$local_part_data$&
.vindex "&$local_part_data$&"
-When the &%local_parts%& option on a router matches a local part by means of a
-lookup, the data read by the lookup is available during the running of the
-router as &$local_part_data$&. In addition, if the driver routes the address
-to a transport, the value is available in that transport. If the transport is
-handling multiple addresses, the value from the first address is used.
-
+When the &%local_parts%& condition on a router or ACL
+matches a local part list
.new
-The &%check_local_user%& router option also sets this variable.
+the match value is copied to &$local_part_data$&.
+This is an enhancement over previous versions of Exim, when it only
+applied to the data read by a lookup.
+For details on match values see section &<<SECTlistresults>>& et. al.
.wen
-&$local_part_data$& is also set when the &%local_parts%& condition in an ACL
-matches a local part by means of a lookup. The data read by the lookup is
-available during the rest of the ACL statement. In all other situations, this
-variable expands to nothing.
+The &%check_local_user%& router option also sets this variable.
.vindex &$local_part_prefix$& &&&
&$local_part_prefix_v$& &&&
value of &$local_part$& during routing and subsequent delivery. The values of
any prefix or suffix are in &$local_part_prefix$& and
&$local_part_suffix$&, respectively.
-.new
.cindex "tainted data"
If the specification did not include a wildcard then
the affix variable value is not tainted.
the affix matched by the wildcard is in
&$local_part_prefix_v$& or &$local_part_suffix_v$& as appropriate,
and both the whole and varying values are tainted.
-.wen
.vitem &$local_scan_data$&
.vindex "&$local_scan_data$&"
contains the size supplied on the MAIL command, or -1 if no size was given. The
value may not, of course, be truthful.
-.vitem &$mime_$&&'xxx'&
+.vitem &$mime_anomaly_level$& &&&
+ &$mime_anomaly_text$& &&&
+ &$mime_boundary$& &&&
+ &$mime_charset$& &&&
+ &$mime_content_description$& &&&
+ &$mime_content_disposition$& &&&
+ &$mime_content_id$& &&&
+ &$mime_content_size$& &&&
+ &$mime_content_transfer_encoding$& &&&
+ &$mime_content_type$& &&&
+ &$mime_decoded_filename$& &&&
+ &$mime_filename$& &&&
+ &$mime_is_coverletter$& &&&
+ &$mime_is_multipart$& &&&
+ &$mime_is_rfc822$& &&&
+ &$mime_part_count$&
A number of variables whose names start with &$mime$& are
available when Exim is compiled with the content-scanning extension. For
details, see section &<<SECTscanmimepart>>&.
This variable is set to &"yes"& if PRDR was requested by the client for the
current message, otherwise &"no"&.
-.vitem &$prvscheck_address$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$prvscheck_keynum$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
-which is described in sections &<<SECTexpansionitems>>& and
-&<<SECTverifyPRVS>>&.
-
-.vitem &$prvscheck_result$&
-This variable is used in conjunction with the &%prvscheck%& expansion item,
+.vitem &$prvscheck_address$& &&&
+ &$prvscheck_keynum$& &&&
+ &$prvscheck_result$&
+These variables are used in conjunction with the &%prvscheck%& expansion item,
which is described in sections &<<SECTexpansionitems>>& and
&<<SECTverifyPRVS>>&.
.cindex "spool" "number of messages"
This variable contains the number of messages queued.
It is evaluated on demand, but no more often than once every minute.
+If there is no daemon notifier socket open, the value will be
+an empty string.
.vitem &$r_...$&
.vindex &$r_...$&
dns_dnssec_ok = 1
.endd
-.new
In addition, on Linux with glibc 2.31 or newer the resolver library will
default to stripping out a successful validation status.
This will break a previously working Exim installation.
.code
options trust-ad
.endd
-.wen
Exim does not perform DNSSEC validation itself, instead leaving that to a
validating resolver (e.g. unbound, or bind with suitable configuration).
example, a system filter could set a value indicating how likely it is that a
message is junk mail.
-.vitem &$spam_$&&'xxx'&
+.vitem &$spam_score$& &&&
+ &$spam_score_int$& &&&
+ &$spam_bar$& &&&
+ &$spam_report$& &&&
+ &$spam_action$&
A number of variables whose names start with &$spam$& are available when Exim
is compiled with the content-scanning extension. For details, see section
&<<SECTscanspamass>>&.
If certificate verification fails it may refer to a failing chain element
which is not the leaf.
+
+.new
+.vitem &$tls_in_resumption$& &&&
+ &$tls_out_resumption$&
+.vindex &$tls_in_resumption$&
+.vindex &$tls_out_resumption$&
+.cindex TLS resumption
+Observability for TLS session resumption. See &<<SECTresumption>>& for details.
+.wen
+
+
.vitem &$tls_in_sni$&
.vindex "&$tls_in_sni$&"
.vindex "&$tls_sni$&"
.cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI "observability on server"
When a TLS session is being established, if the client sends the Server
Name Indication extension, the value will be placed in this variable.
If the variable appears in &%tls_certificate%& then this option and
.vitem &$tls_out_sni$&
.vindex "&$tls_out_sni$&"
.cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI "observability in client"
During outbound
SMTP deliveries, this variable reflects the value of the &%tls_sni%& option on
the transport.
option to a true value. To avoid breaking existing installations, it
defaults to false.
+.new
+&*Note*&: This is entirely separate from Exim's tainted-data tracking.
+.wen
+
.section "Calling Perl subroutines" "SECID86"
When the configuration file includes a &%perl_startup%& option you can make use
.section "Miscellaneous" "SECID96"
.table2
+.row &%add_environment%& "environment variables"
+.row &%allow_insecure_tainted_data%& "turn taint errors into warnings"
.row &%bi_command%& "to run for &%-bi%& command line option"
.row &%debug_store%& "do extra internal checks"
.row &%disable_ipv6%& "do no IPv6 processing"
+.row &%keep_environment%& "environment variables"
.row &%keep_malformed%& "for broken files &-- should not happen"
.row &%localhost_number%& "for unique message ids in clusters"
.row &%message_body_newlines%& "retain newlines in &$message_body$&"
.row &%notifier_socket%& "override compiled-in value"
.row &%pid_file_path%& "override compiled-in value"
.row &%queue_run_max%& "maximum simultaneous queue runners"
+.row &%smtp_backlog_monitor%& "level to log listen backlog"
.endtable
.row &%local_scan_timeout%& "timeout for &[local_scan()]&"
.row &%message_size_limit%& "for all messages"
.row &%percent_hack_domains%& "recognize %-hack for these domains"
+.row &%proxy_protocol_timeout%& "timeout for proxy protocol negotiation"
.row &%spamd_address%& "set interface to SpamAssassin"
.row &%strict_acl_vars%& "object to unset ACL variables"
.row &%spf_smtp_comment_template%& "template for &$spf_smtp_comment$&"
.table2
.row &%gnutls_compat_mode%& "use GnuTLS compatibility mode"
.row &%gnutls_allow_auto_pkcs11%& "allow GnuTLS to autoload PKCS11 modules"
+.row &%hosts_require_alpn%& "mandatory ALPN"
.row &%openssl_options%& "adjust OpenSSL compatibility options"
.row &%tls_advertise_hosts%& "advertise TLS to these hosts"
+.row &%tls_alpn%& "acceptable protocol names"
.row &%tls_certificate%& "location of server certificate"
.row &%tls_crl%& "certificate revocation list"
.row &%tls_dh_max_bits%& "clamp D-H bit count suggestion"
.row &%hold_domains%& "hold delivery for these domains"
.row &%local_interfaces%& "for routing checks"
.row &%queue_domains%& "no immediate delivery for these"
+.row &%queue_fast_ramp%& "parallel delivery with 2-phase queue run"
.row &%queue_only%& "no immediate delivery at all"
.row &%queue_only_file%& "no immediate delivery if file exists"
.row &%queue_only_load%& "no immediate delivery if load is high"
configuration). This &"magic string"& matches the domain literal form of all
the local host's IP addresses.
+.new
+.option allow_insecure_tainted_data main boolean false
+.cindex "de-tainting"
+.oindex "allow_insecure_tainted_data"
+The handling of tainted data may break older (pre 4.94) configurations.
+Setting this option to "true" turns taint errors (which result in a temporary
+message rejection) into warnings. This option is meant as mitigation only
+and deprecated already today. Future releases of Exim may ignore it.
+The &%taint%& log selector can be used to suppress even the warnings.
+.wen
+
+
.option allow_mx_to_ip main boolean false
.cindex "MX record" "pointing to IP address"
This option defines a template file containing paragraphs of text to be used
for constructing bounce messages. Details of the file's contents are given in
chapter &<<CHAPemsgcust>>&.
-.new
.cindex bounce_message_file "tainted data"
The option is expanded to give the file path, which must be
absolute and untainted.
-.wen
See also &%warn_message_file%&.
to handle IPv6 literal addresses.
-.new
.option dkim_verify_hashes main "string list" "sha256 : sha512"
.cindex DKIM "selecting signature algorithms"
This option gives a list of hash types which are acceptable in signatures,
-.wen
and an order of processing.
Signatures with algorithms not in the list will be ignored.
Signatures with algorithms not in the list will be ignored.
-.new
.option dkim_verify_min_keysizes main "string list" "rsa=1024 ed25519=250"
This option gives a list of key sizes which are acceptable in signatures.
The list is keyed by the algorithm type for the key; the values are in bits.
Signatures with keys smaller than given by this option will fail verification.
The default enforces the RFC 8301 minimum key size for RSA signatures.
-.wen
.option dkim_verify_minimal main boolean false
If set to true, verification of signatures will terminate after the
If the resolver library does not support DNSSEC then this option has no effect.
-.new
On Linux with glibc 2.31 or newer this is insufficient, the resolver library
will default to stripping out a successful validation status.
This will break a previously working Exim installation.
.code
options trust-ad
.endd
-.wen
.option dns_ipv4_lookup main "domain list&!!" unset
A NOTIFY=SUCCESS option requests success-DSN messages.
A NOTIFY= option with no argument requests that no delay or failure DSNs
are sent.
-.new
&*Note*&: Supplying success-DSN messages has been criticised
on privacy grounds; it can leak details of internal forwarding.
-.wen
.option dsn_from main "string&!!" "see below"
.cindex "&'From:'& header line" "in bounces"
If the &%smtp_connection%& log selector is not set, this option has no effect.
+.new
+.option hosts_require_alpn main "host list&!!" unset
+.cindex ALPN "require negotiation in server"
+.cindex TLS ALPN
+.cindex TLS "Application Layer Protocol Names"
+If the TLS library supports ALPN
+then a successful negotiation of ALPN will be required for any client
+matching the list, for TLS to be used.
+See also the &%tls_alpn%& option.
+
+&*Note*&: prevention of fallback to in-clear connection is not
+managed by this option, and should be done separately.
+.wen
+
.option hosts_proxy main "host list&!!" unset
.cindex proxy "proxy protocol"
transport driver.
-.new
.option notifier_socket main string "$spool_directory/exim_daemon_notify"
This option gives the name for a unix-domain socket on which the daemon
listens for work and information-requests.
The option is expanded before use.
If the platform supports Linux-style abstract socket names, the result
is used with a nul byte prefixed.
-Otherwise, it should be a full path name and use a directory accessible
+Otherwise,
+.new "if nonempty,"
+it should be a full path name and use a directory accessible
to Exim.
-If the Exim command line uses a &%-oX%& option and does not use &%-oP%&
-then a notifier socket is not created.
+.new
+If this option is set as empty,
+or the command line &%-oY%& option is used, or
.wen
+the command line uses a &%-oX%& option and does not use &%-oP%&,
+then a notifier socket is not created.
.option openssl_options main "string list" "+no_sslv2 +no_sslv3 +single_dh_use +no_ticket +no_renegotiation"
.option pipelining_connect_advertise_hosts main "host list&!!" *
.cindex "pipelining" "early connection"
.cindex "pipelining" PIPE_CONNECT
-.cindex "ESMTP extensions" X_PIPE_CONNECT
+.cindex "ESMTP extensions" PIPE_CONNECT
If Exim is built with the SUPPORT_PIPE_CONNECT build option
this option controls which hosts the facility is advertised to
and from which pipeline early-connection (before MAIL) SMTP
See also the &%hosts_pipe_connect%& smtp transport option.
-Currently the option name &"X_PIPE_CONNECT"& is used.
+.new
+The SMTP service extension keyword advertised is &"PIPE_CONNECT"&.
+.wen
.option prdr_enable main boolean false
&%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
+.new
+.option proxy_protocol_timeout main time 3s
+.cindex proxy "proxy protocol"
+This option sets the timeout for proxy protocol negotiation.
+For details see section &<<SECTproxyInbound>>&.
+.wen
+
+
.option qualify_domain main string "see below"
.cindex "domain" "for qualifying addresses"
.cindex "address" "qualification"
next queue run. See also &%hold_domains%& and &%queue_smtp_domains%&.
+.new
+.option queue_fast_ramp main boolean false
+.cindex "queue runner" "two phase"
+.cindex "queue" "double scanning"
+If set to true, two-phase queue runs, initiated using &%-qq%& on the
+command line, may start parallel delivery processes during their first
+phase. This will be done when a threshold number of messages have been
+routed for a single host.
+.wen
+
+
.option queue_list_requires_admin main boolean true
.cindex "restricting access to features"
.oindex "&%-bp%&"
option was not set.
-.option recipients_max main integer 0
+.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
deliveries if the configuration allows a delivery attempt as soon as a message
is received.
+See also the &%max_parallel%& generic transport option,
+and the &%serialize_hosts%& smtp transport option.
+
.cindex "number of deliveries"
.cindex "delivery" "maximum number of"
If you want to control the total number of deliveries on the system, you
. searchable. NM changed this occurrence for bug 1197 to no longer allow
. the option name to split.
-.option "smtp_accept_max_per_connection" main integer 1000 &&&
+.option "smtp_accept_max_per_connection" main integer&!! 1000 &&&
smtp_accept_max_per_connection
.cindex "SMTP" "limiting incoming message count"
.cindex "limit" "messages per SMTP connection"
response is given to subsequent MAIL commands. This limit is a safety
precaution against a client that goes mad (incidents of this type have been
seen).
+.new
+The option is expanded after the HELO or EHLO is received
+and may depend on values available at that time.
+An empty or zero value after expansion removes the limit.
+.wen
.option smtp_accept_max_per_host main string&!! unset
verification if there is no remote transport from which to obtain a
&%helo_data%& value.
+.option smtp_backlog_monitor main integer 0
+.cindex "connection backlog" monitoring
+If this option is set to greater than zero, and the backlog of available
+TCP connections on a socket listening for SMTP is larger than it, a line
+is logged giving the value and the socket address and port.
+The value is retrived jsut before an accept call.
+This facility is only available on Linux.
+
.option smtp_banner main string&!! "see below"
.cindex "SMTP" "welcome banner"
.cindex "banner for SMTP"
.option smtp_connect_backlog main integer 20
-.cindex "connection backlog"
+.cindex "connection backlog" "set maximum"
.cindex "SMTP" "connection backlog"
.cindex "backlog of connections"
This option specifies a maximum number of waiting SMTP connections. Exim passes
smtp_etrn_command = /etc/etrn_command $domain \
$sender_host_address
.endd
-.new
If the option is not set, the argument for the ETRN command must
be a &'#'& followed by an address string.
In this case an &'exim -R <string>'& command is used;
if the ETRN ACL has set up a named-queue then &'-MCG <queue>'& is appended.
-.wen
A new process is created to run the command, but Exim does not wait for it to
complete. Consequently, its status cannot be checked. If the command cannot be
This option is available when Exim is compiled with SPF support.
See section &<<SECSPF>>& for more details.
-.new
.option spf_smtp_comment_template main string&!! "Please%_see%_http://www.open-spf.org/Why"
This option is available when Exim is compiled with SPF support. It
allows the customisation of the SMTP comment that the SPF library
A note on using Exim variables: As
currently the SPF library is initialized before the SMTP EHLO phase,
the variables useful for expansion are quite limited.
-.wen
.option split_spool_directory main boolean false
.option syslog_timestamp main boolean true
.cindex "syslog" "timestamps"
+.cindex timestamps syslog
If &%syslog_timestamp%& is set false, the timestamps on Exim's log lines are
omitted when these lines are sent to syslog. See chapter &<<CHAPlog>>& for
details of Exim's logging.
is not required the &%tls_advertise_hosts%& option should be set empty.
-.option tls_certificate main string list&!! unset
+.new
+.option tls_alpn main "string list&!!" "smtp : esmtp"
+.cindex TLS "Application Layer Protocol Names"
+.cindex TLS ALPN
+.cindex ALPN "set acceptable names for server"
+If this option is set,
+the TLS library supports ALPN,
+and the client offers either more than
+ALPN name or a name which does not match the list,
+the TLS connection is declined.
+.wen
+
+
+.option tls_certificate main "string list&!!" unset
.cindex "TLS" "server certificate; location of"
.cindex "certificate" "server, location of"
The value of this option is expanded, and must then be a list of absolute paths to
file is used, the &$tls_in_ourcert$& variable is unreliable.
The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions.
+.cindex SNI "selecting server certificate based on"
If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then
if the OpenSSL build supports TLS extensions and the TLS client sends the
Server Name Indication extension, then this option and others documented in
&<<SECTtlssni>>& will be re-expanded.
-If this option is unset or empty a fresh self-signed certificate will be
-generated for every connection.
+If this option is unset or empty a self-signed certificate will be
+.new
+used.
+Under Linux this is generated at daemon startup; on other platforms it will be
+generated fresh for every connection.
+.wen
.option tls_crl main string&!! unset
.cindex "TLS" "server certificate revocation list"
-.option tls_privatekey main string list&!! unset
+.option tls_privatekey main "string list&!!" unset
.cindex "TLS" "server private key; location of"
The value of this option is expanded, and must then be a list of absolute paths to
files which contains the server's private keys.
&<<SECTreqciphssl>>& and &<<SECTreqciphgnu>>&.
+.new
+.option tls_resumption_hosts main "host list&!!" unset
+.cindex TLS resumption
+This option controls which connections to offer the TLS resumption feature.
+See &<<SECTresumption>>& for details.
+.wen
+
+
.option tls_try_verify_hosts main "host list&!!" unset
.cindex "TLS" "client certificate verification"
.cindex "certificate" "verification of client"
the value is a file then the certificates are sent by Exim as a server to
connecting clients, defining the list of accepted certificate authorities.
Thus the values defined should be considered public data. To avoid this,
-use the explicit directory version.
+use the explicit directory version. (If your peer is Exim up to 4.85,
+using GnuTLS, you may need to send the CAs (thus using the file
+variant). Otherwise the peer doesn't send its certificate.)
See &<<SECTtlssni>>& for discussion of when this option might be re-expanded.
been in the queue for a specified amount of time, as specified by
&%delay_warning%&. Details of the file's contents are given in chapter
&<<CHAPemsgcust>>&.
-.new
.cindex warn_message_file "tainted data"
The option is expanded to give the file path, which must be
absolute and untainted.
-.wen
See also &%bounce_message_file%&.
provide data for a transport is: &%errors_to%&, &%headers_add%&,
&%headers_remove%&, &%transport%&.
+.new
+The name of a router is limited to be &drivernamemax; ASCII characters long;
+prior to Exim 4.95 names would be silently truncated at this length, but now
+it is enforced.
+.wen
.option address_data routers string&!! unset
local system. The check is done by calling the &[getpwnam()]& function rather
than trying to read &_/etc/passwd_& directly. This means that other methods of
holding password data (such as NIS) are supported. If the local part is a local
-user, &$home$& is set from the password data, and can be tested in other
+user,
+.cindex "tainted data" "de-tainting"
+&$local_part_data$& is set to an untainted version of the local part and
+&$home$& is set from the password data. The latter can be tested in other
preconditions that are evaluated after this one (the order of evaluation is
given in section &<<SECTrouprecon>>&). However, the value of &$home$& can be
overridden by &%router_home_directory%&. If the local part is not a local user,
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set.
+the DNSSEC request bit set.
This applies to all of the SRV, MX, AAAA, A lookup sequence.
.option dnssec_require_domains routers "domain list&!!" unset
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set. Any returns not having the Authenticated Data bit
+the DNSSEC request bit set. Any returns not having the Authenticated Data bit
(AD bit) set will be ignored and logged as a host-lookup failure.
This applies to all of the SRV, MX, AAAA, A lookup sequence.
If this option is set, the router is skipped unless the current domain matches
the list. If the match is achieved by means of a file lookup, the data that the
lookup returned for the domain is placed in &$domain_data$& for use in string
-expansions of the driver's private options. See section &<<SECTrouprecon>>& for
+expansions of the driver's private options and in the transport.
+See section &<<SECTrouprecon>>& for
a list of the order in which preconditions are evaluated.
that is associated with any addresses that are accepted by the router.
However, the option has no effect when an address is just being verified.
Each list item is separately expanded, at transport time.
-.new
If an item ends in *, it will match any header with the given prefix.
-.wen
The way in which
the text is used to remove header lines at transport time is described in
section &<<SECTheadersaddrem>>&. Header lines are not actually removed until
This behaviour can be overridden by setting &%rcpt_include_affixes%& true on
the relevant transport.
-.new
.vindex &$local_part_prefix_v$&
If wildcarding (above) was used then the part of the prefix matching the
wildcard is available in &$local_part_prefix_v$&.
-.wen
When an address is being verified, &%local_part_prefix%& affects only the
behaviour of the router. If the callout feature of verification is in use, this
string is expanded, it is possible to make it depend on the domain, for
example:
.code
-local_parts = dbm;/usr/local/specials/$domain
+local_parts = dbm;/usr/local/specials/$domain_data
.endd
.vindex "&$local_part_data$&"
If the match is achieved by a lookup, the data that the lookup returned
for the local part is placed in the variable &$local_part_data$& for use in
-expansions of the router's private options. You might use this option, for
+expansions of the router's private options or in the transport.
+You might use this option, for
example, if you have a large number of local virtual domains, and you want to
send all postmaster mail to the same place without having to set up an alias in
each virtual domain:
When a router runs, the strings are evaluated in order,
to create variables which are added to the set associated with
the address.
+.new
+This is done immediately after all the preconditions, before the
+evaluation of the &%address_data%& option.
+.wen
The variable is set with the expansion of the value.
The variables can be used by the router options
(not including any preconditions)
yield empty addresses, for example, items containing only RFC 2822 address
comments.
-.new
.cindex "tainted data" "in filenames"
.cindex redirect "tainted data"
Tainted data may not be used for a filename.
In the examples above, &$local_part$& is used for looking up data held locally
on the system, and not used directly (the second example derives &$home$& via
the passsword file or database, using &$local_part$&).
-.wen
.code
list1: :include:/opt/lists/list1
.endd
-.new
.cindex "tainted data" "in filenames"
.cindex redirect "tainted data"
Tainted data may not be used for a filename.
-.wen
.next
.cindex "address redirection" "to black hole"
.cindex "delivery" "discard"
the text is included in the error message that Exim generates.
.cindex "SMTP" "error codes"
-By default, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
+By default for verify, Exim sends a 451 SMTP code for a &':defer:'&, and 550 for
&':fail:'&. However, if the message starts with three digits followed by a
space, optionally followed by an extended code of the form &'n.n.n'&, also
followed by a space, and the very first digit is the same as the default error
.scindex IIDgenoptra1 "generic options" "transport"
.scindex IIDgenoptra2 "options" "generic; for transports"
.scindex IIDgenoptra3 "transport" "generic options for"
+.new
+The name of a transport is limited to be &drivernamemax; ASCII characters long;
+prior to Exim 4.95 names would be silently truncated at this length, but now
+it is enforced.
+.wen
+
The following generic options apply to all transports:
If the result of the expansion is an empty string, or if the expansion
is forced to fail, no action is taken. Other expansion failures are treated as
errors and cause the delivery to be deferred.
-.new
If an item ends in *, it will match any header with the given prefix.
-.wen
Matching headers are omitted from the message as it is transported, as described
in section &<<SECTheadersaddrem>>&. Header removal can also be specified by
.option return_path_add transports boolean false
-.cindex "&'Return-path:'& header line"
+.chindex Return-path:
If this option is true, a &'Return-path:'& header is added to the message.
Although the return path is normally available in the prefix line of BSD
mailboxes, this is commonly not displayed by MUAs, and so the user does not
used to determine the file or directory name for the delivery. Normally, the
contents of &$address_file$& are used in some way in the string expansion.
.endlist
-.new
+If the &%create_file%& option is set to a path which
+matches (see the option definition below for details)
+a file or directory name
+for the delivery, that name becomes de-tainted.
+
.cindex "tainted data" "in filenames"
.cindex appendfile "tainted data"
Tainted data may not be used for a file or directory name.
This means that, for instance, &$local_part$& cannot be used directly
as a component of a path. It can however be used as the key for a lookup
which returns a path (or component).
-.wen
.cindex "Sieve filter" "configuring &(appendfile)&"
delivery, it applies to the top level directory, not the maildir directories
beneath.
+.new
The option must be set to one of the words &"anywhere"&, &"inhome"&, or
-&"belowhome"&. In the second and third cases, a home directory must have been
-set for the transport. This option is not useful when an explicit filename is
+&"belowhome"&, or to an absolute path.
+.wen
+
+In the second and third cases, a home directory must have been
+set for the transport, and the file or directory being created must
+reside within it.
+The "belowhome" checking additionally checks for attempts to use "../"
+to evade the testing.
+This option is not useful when an explicit filename is
given for normal mailbox deliveries. It is intended for the case when filenames
are generated from users' &_.forward_& files. These are usually handled
by an &(appendfile)& transport called &%address_file%&. See also
&%file_must_exist%&.
+.new
+In the fourth case,
+the value given for this option must be an absolute path for an
+existing directory.
+The value is used for checking instead of a home directory;
+checking is done in "belowhome" mode.
+
+.cindex "tainted data" "de-tainting"
+If "belowhome" checking is used, the file or directory path
+becomes de-tainted.
+.wen
+
.option directory appendfile string&!! unset
This option is mutually exclusive with the &%file%& option, but one of &%file%&
(see &%maildir_format%& and &%mailstore_format%&), and see section
&<<SECTopdir>>& for further details of this form of delivery.
+.new
+The result of expansion must not be tainted, unless the &%create_file%& option
+specifies a path.
+.wen
+
.option directory_file appendfile string&!! "see below"
.cindex "base62"
&%use_fcntl_lock%&, &%use_flock_lock%&, or &%use_lockfile%& must be set with
&%file%&.
+.new
+The result of expansion must not be tainted, unless the &%create_file%& option
+specifies a path.
+.wen
+
.cindex "NFS" "lock file"
.cindex "locking files"
.cindex "lock files"
details of the local delivery environment and chapter &<<CHAPbatching>>&
for a discussion of local delivery batching.
-.new
.cindex "tainted data" "in pipe command"
.cindex pipe "tainted data"
Tainted data may not be used for the command name.
-.wen
.section "Concurrent delivery" "SECID140"
.option command_timeout smtp time 5m
+.cindex timeout "smtp transport command"
This sets a timeout for receiving a response to an SMTP command that has been
sent out. It is also used when waiting for the initial banner line from the
remote host. Its value must not be zero.
.option connect_timeout smtp time 5m
+.cindex timeout "smtp transport connect"
This sets a timeout for the &[connect()]& function, which sets up a TCP/IP call
to a remote host. A setting of zero allows the system timeout (typically
several minutes) to act. To have any effect, the value of this option must be
.option data_timeout smtp time 5m
+.cindex timeout "for transmitted SMTP data blocks"
This sets a timeout for the transmission of each block in the data portion of
the message. As a result, the overall timeout for a message depends on the size
of the message. Its value must not be zero. See also &%final_timeout%&.
.option dkim_canon smtp string&!! unset
DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
-.option dkim_domain smtp string list&!! unset
+.option dkim_domain smtp "string list&!!" unset
DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.option dkim_hash smtp string&!! sha256
DKIM signing option. For details see section &<<SECDKIMSIGN>>&.
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_request_domains%& will be done with
-the dnssec request bit set. Setting this transport option is only useful if the
+the DNSSEC request bit set. Setting this transport option is only useful if the
transport overrides or sets the host names. See the &%dnssec_request_domains%&
router option.
.cindex "security" "MX lookup"
.cindex "DNS" "DNSSEC"
DNS lookups for domains matching &%dnssec_require_domains%& will be done with
-the dnssec request bit set. Setting this transport option is only
+the DNSSEC request bit set. Setting this transport option is only
useful if the transport overrides or sets the host names. See the
&%dnssec_require_domains%& router option.
.option final_timeout smtp time 10m
+.cindex timeout "for transmitted SMTP data accept"
This is the timeout that applies while waiting for the response to the final
line containing just &"."& that terminates a message. Its value must not be
zero.
TLS session for any host that matches this list.
&%tls_verify_certificates%& should also be set for the transport.
+.new
+.option hosts_require_alpn smtp "host list&!!" unset
+.cindex ALPN "require negotiation in client"
+.cindex TLS ALPN
+.cindex TLS "Application Layer Protocol Names"
+If the TLS library supports ALPN
+then a successful negotiation of ALPN will be required for any host
+matching the list, for TLS to be used.
+See also the &%tls_alpn%& option.
+
+&*Note*&: prevention of fallback to in-clear connection is not
+managed by this option; see &%hosts_require_tls%&.
+.wen
+
.option hosts_require_dane smtp "host list&!!" unset
.cindex DANE "transport options"
.cindex DANE "requiring for certain servers"
If built with DANE support, Exim will require that a DNSSEC-validated
TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
+and that a DANE-verified TLS connection is made.
There will be no fallback to in-clear communication.
+See the &%dnssec_request_domains%& router and transport options.
See section &<<SECDANE>>&.
+.option hosts_require_helo smtp "host list&!!" *
+.cindex "HELO/EHLO" requiring
+Exim will require an accepted HELO or EHLO command from a host matching
+this list, before accepting a MAIL command.
+
.option hosts_require_ocsp smtp "host list&!!" unset
.cindex "TLS" "requiring for certain servers"
Exim will request, and check for a valid Certificate Status being given, on a
.cindex "authentication" "optional in client"
This option provides a list of servers to which, provided they announce
authentication support, Exim will attempt to authenticate as a client when it
-connects. If authentication fails, Exim will try to transfer the message
-unauthenticated. See also &%hosts_require_auth%&, and chapter
-&<<CHAPSMTPAUTH>>& for details of authentication.
+connects. If authentication fails
+.new
+and &%hosts_require_auth%& permits,
+.wen
+Exim will try to transfer the message unauthenticated.
+See also chapter &<<CHAPSMTPAUTH>>& for details of authentication.
.option hosts_try_chunking smtp "host list&!!" *
.cindex CHUNKING "enabling, in client"
.cindex "RFC 3030" "CHUNKING"
This option provides a list of servers to which, provided they announce
CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
-.new
Unless DKIM signing is being done,
-.wen
BDAT will not be used in conjunction with a transport filter.
.option hosts_try_dane smtp "host list&!!" *
.cindex DANE "transport options"
.cindex DANE "attempting for certain servers"
-If built with DANE support, Exim will require that a DNSSEC-validated
-TLSA record is present for any host matching the list,
-and that a DANE-verified TLS connection is made. See
-the &%dnssec_request_domains%& router and transport options.
-There will be no fallback to in-clear communication.
+.new
+If built with DANE support, Exim will look up a
+TLSA record for any host matching the list,
+If one is found and that lookup was DNSSEC-validated,
+then Exim requires that a DANE-verified TLS connection is made for that host;
+there will be no fallback to in-clear communication.
+.wen
+See the &%dnssec_request_domains%& router and transport options.
See section &<<SECDANE>>&.
.option hosts_try_fastopen smtp "host list&!!" *
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
so can cause parallel connections to the same host if &%remote_max_parallel%&
-permits this.
+permits this. A value setting of zero disables the limit.
+
+
+.new
+.option message_linelength_limit smtp integer 998
+.cindex "line length" limit
+This option sets the maximum line length, in bytes, that the transport
+will send. Any messages with lines exceeding the given value
+will fail and a failure-DSN ("bounce") message will if possible be returned
+to the sender.
+The default value is that defined by the SMTP standards.
+
+It is generally wise to also check in the data ACL so that messages
+received via SMTP can be refused without producing a bounce.
+.wen
.option multi_domain smtp boolean&!! true
&$address_data$&, &$domain_data$&, &$local_part_data$&,
&$host$&, &$host_address$& and &$host_port$&.
+.new
+If the connection is DANE-enabled then this option is ignored;
+only messages having the domain used for the DANE TLSA lookup are
+sent on the connection.
+.wen
+
.option port smtp string&!! "see below"
.cindex "port" "sending TCP/IP"
.cindex "TCP/IP" "setting outgoing port"
changes to &"smtps"&, and the transport initiates TLS immediately after
connecting, as an outbound SSL-on-connect, instead of using STARTTLS to upgrade.
The Internet standards bodies used to strongly discourage use of this mode,
-but as of RFC 8314 it is perferred over STARTTLS for message submission
+but as of RFC 8314 it is preferred over STARTTLS for message submission
(as distinct from MTA-MTA communication).
transport. For details see section &<<SECTproxySOCKS>>&.
+.new
+.option tls_alpn smtp string&!! unset
+.cindex TLS "Application Layer Protocol Names"
+.cindex TLS ALPN
+.cindex ALPN "set name in client"
+If this option is set
+and the TLS library supports ALPN,
+the value given is used.
+
+As of writing no value has been standardised for email use.
+The authors suggest using &"smtp"&.
+.wen
+
+
+
.option tls_certificate smtp string&!! unset
.cindex "TLS" "client certificate, location of"
.cindex "certificate" "client, location of"
ciphers is a preference order.
+.new
+.option tls_resumption_hosts smtp "host list&!!" unset
+.cindex TLS resumption
+This option controls which connections to use the TLS resumption feature.
+See &<<SECTresumption>>& for details.
+.wen
+
+
.option tls_sni smtp string&!! unset
.cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI "setting in client"
.vindex "&$tls_sni$&"
-If this option is set then it sets the $tls_out_sni variable and causes any
+If this option is set
+.new
+and the connection is not DANE-validated
+.wen
+then it sets the $tls_out_sni variable and causes any
TLS session to pass this value as the Server Name Indication extension to
the remote side, which can be used by the remote side to select an appropriate
certificate and private key for the session.
transfer of mail between servers that have no managerial connection with each
other.
+.new
+The name of an authenticator is limited to be &drivernamemax; ASCII characters long;
+prior to Exim 4.95 names would be silently truncated at this length, but now
+it is enforced.
+.wen
+
.cindex "AUTH" "description of"
.cindex "ESMTP extensions" AUTH
Very briefly, the way SMTP authentication works is as follows:
.ilist
The client host must match &%auth_advertise_hosts%& (default *).
.next
-It the &%server_advertise_condition%& option is set, its expansion must not
+If the &%server_advertise_condition%& option is set, its expansion must not
yield the empty string, &"0"&, &"no"&, or &"false"&.
.endlist
.endd
gives an incorrect answer because of the unescaped &"@"& and &"$"& characters.
-If you have the &%mimencode%& command installed, another way to do produce
+If you have the &%mimencode%& command installed, another way to produce
base64-encoded strings is to run the command
.code
echo -e -n `\0user\0password' | mimencode
client_send = ^username^mysecret
.endd
The lack of colons means that the entire text is sent with the AUTH
-command, with the circumflex characters converted to NULs. A similar example
+command, with the circumflex characters converted to NULs.
+.new
+Note that due to the ambiguity of parsing three consectutive circumflex characters
+there is no way to provide a password having a leading circumflex.
+.wen
+
+
+A similar example
that uses the LOGIN mechanism is:
.code
fixed_login:
option is passed. When authentication succeeds, the identity of the user
who authenticated is placed in &$auth1$&.
-.new
-The Dovecot configuration to match the above wil look
+The Dovecot configuration to match the above will look
something like:
.code
conf.d/10-master.conf :-
auth_mechanisms = plain login ntlm
.endd
-.wen
.ecindex IIDdcotauth1
.ecindex IIDdcotauth2
made that any particular new authentication mechanism will be supported
without code changes in Exim.
-.new
The library is expected to add support in an upcoming
realease for the SCRAM-SHA-256 method.
The macro _HAVE_AUTH_GSASL_SCRAM_SHA_256 will be defined
when this happens.
+.new
+To see the list of mechanisms supported by the library run Exim with "auth" debug
+enabled and look for a line containing "GNU SASL supports".
+Note however that some may not have been tested from Exim.
+.wen
+
.option client_authz gsasl string&!! unset
This option can be used to supply an &'authorization id'&
.option client_username gsasl string&!! unset
This option is exapanded before use, and should result in
the account name to be used.
-.wen
-.new
+
.option client_spassword gsasl string&!! unset
+.new
+This option is only supported for library versions 1.9.1 and greater.
+The macro _HAVE_AUTH_GSASL_SCRAM_S_KEY will be defined when this is so.
+.wen
+
If a SCRAM mechanism is being used and this option is set
+and correctly sized
it is used in preference to &%client_password%&.
The value after expansion should be
a 40 (for SHA-1) or 64 (for SHA-256) character string
with the PBKDF2-prepared password, hex-encoded.
+
Note that this value will depend on the salt and iteration-count
supplied by the server.
+The option is expanded before use.
+.new
+During the expansion &$auth1$& is set with the client username,
+&$auth2$& with the iteration count, and
+&$auth3$& with the salt.
+
+The intent of this option
+is to support clients that can cache thes salted password
+to save on recalculation costs.
+The cache lookup should return an unusable value
+(eg. an empty string)
+if the salt or iteration count has changed
+
+If the authentication succeeds then the above variables are set,
+.vindex "&$auth4$&"
+plus the calculated salted password value value in &$auth4$&,
+during the expansion of the &%client_set_id%& option.
+A side-effect of this expansion can be used to prime the cache.
.wen
-
.option server_channelbinding gsasl boolean false
-Do not set this true and rely on the properties
-without consulting a cryptographic engineer.
-
Some authentication mechanisms are able to use external context at both ends
of the session to bind the authentication to that context, and fail the
authentication process if that context differs. Specifically, some TLS
non-issue, as a man-in-the-middle attack will cause the correct client and
server to see different identifiers and authentication will fail.
-.new
This is
only usable by mechanisms which support "channel binding"; at time of
writing, that's the SCRAM family.
When using this feature the "-PLUS" variants of the method names need to be used.
-.wen
This defaults off to ensure smooth upgrade across Exim releases, in case
this option causes some clients to start failing. Some future release
of Exim might have switched the default to be true.
-However, Channel Binding in TLS has proven to be vulnerable in current versions.
-Do not plan to rely upon this feature for security, ever, without consulting
-with a subject matter expert (a cryptographic engineer).
+. However, Channel Binding in TLS has proven to be vulnerable in current versions.
+. Do not plan to rely upon this feature for security, ever, without consulting
+. with a subject matter expert (a cryptographic engineer).
+
+.new
+This option was deprecated in previous releases due to doubts over
+the "Triple Handshake" vulnerability.
+Exim takes suitable precausions (requiring Extended Master Secret if TLS
+Session Resumption was used) for safety.
+.wen
.option server_hostname gsasl string&!! "see below"
.option server_scram_iter gsasl string&!! 4096
This option provides data for the SCRAM family of mechanisms.
-.new
The &$auth1$&, &$auth2$& and &$auth3$& variables are available
when this option is expanded.
either the iteration count or the salt).
A minimum value of 4096 is required by the standards
for all current SCRAM mechanism variants.
-.wen
.option server_scram_salt gsasl string&!! unset
This option provides data for the SCRAM family of mechanisms.
-.new
The &$auth1$&, &$auth2$& and &$auth3$& variables are available
when this option is expanded.
The value should be a base64-encoded string,
of random data typically 4-to-16 bytes long.
If unset or empty after expansion the library will provides a value for the
protocol conversation.
-.wen
-.new
.option server_key gsasl string&!! unset
.option server_skey gsasl string&!! unset
These options can be used for the SCRAM family of mechanisms
The libgsasl library release includes a utility &'gsasl'& which can be used
to generate these values.
-.wen
.option server_service gsasl string &`smtp`&
this authentication method on a secure (eg. under TLS) connection.
One possible use, compatible with the
-K-9 Mail Andoid client (&url(https://k9mail.github.io/)),
+K-9 Mail Android client (&url(https://k9mail.github.io/)),
is for using X509 client certificates.
It thus overlaps in function with the TLS authenticator
This should be documented with the feature. If the documentation does not
explicitly state that the feature is infeasible in the other TLS
implementation, then patches are welcome.
+.new
+.next
+The output from "exim -bV" will show which (if any) support was included
+in the build.
+Also, the macro "_HAVE_OPENSSL" or "_HAVE_GNUTLS" will be defined.
+.wen
.endlist
.endd
+.new
+.section "Caching of static server configuration items" "SECTserverTLScache"
+.cindex certificate caching
+.cindex privatekey caching
+.cindex crl caching
+.cindex ocsp caching
+.cindex ciphers caching
+.cindex "CA bundle" caching
+.cindex "certificate authorities" caching
+.cindex tls_certificate caching
+.cindex tls_privatekey caching
+.cindex tls_crl caching
+.cindex tls_ocsp_file caching
+.cindex tls_require_ciphers caching
+.cindex tls_verify_certificate caching
+.cindex caching certificate
+.cindex caching privatekey
+.cindex caching crl
+.cindex caching ocsp
+.cindex caching ciphers
+.cindex caching "certificate authorities
+If any of the main configuration options &%tls_certificate%&, &%tls_privatekey%&,
+&%tls_crl%& and &%tls_ocsp_file%& have values with no
+expandable elements,
+then the associated information is loaded at daemon startup.
+It is made available
+to child processes forked for handling received SMTP connections.
+
+This caching is currently only supported under Linux and FreeBSD.
+
+If caching is not possible, for example if an item has to be dependent
+on the peer host so contains a &$sender_host_name$& expansion, the load
+of the associated information is done at the startup of the TLS connection.
+
+The cache is invalidated and reloaded after any changes to the directories
+containing files specified by these options.
+
+The information specified by the main option &%tls_verify_certificates%&
+is similarly cached so long as it specifies files explicitly
+or (under GnuTLS) is the string &"system,cache"&.
+The latter case is not automatically invalidated;
+it is the operator's responsibility to arrange for a daemon restart
+any time the system certificate authority bundle is updated.
+A HUP signal is sufficient for this.
+The value &"system"& results in no caching under GnuTLS.
+
+The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
+is acceptable in configurations for the Exim executavble.
+
+Caching of the system Certificate Authorities bundle can
+save siginificant time and processing on every TLS connection
+accepted by Exim.
+.wen
+
+
.section "Configuring an Exim client to use TLS" "SECTclientTLS"
The &%tls_certificate%& and &%tls_privatekey%& options of the &(smtp)&
transport provide the client with a certificate, which is passed to the server
-if it requests it. If the server is Exim, it will request a certificate only if
+if it requests it.
+This is an optional thing for TLS connections, although either end
+may insist on it.
+If the server is Exim, it will request a certificate only if
&%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client.
&*Note*&: Do not use a certificate which has the OCSP-must-staple extension,
or need not succeed respectively.
The &%tls_verify_cert_hostnames%& option lists hosts for which additional
-checks are made: that the host name (the one in the DNS A record)
-is valid for the certificate.
+name checks are made on the server certificate.
+.new
+The match against this list is, as per other Exim usage, the
+IP for the host. That is most closely associated with the
+name on the DNS A (or AAAA) record for the host.
+However, the name that needs to be in the certificate
+is the one at the head of any CNAME chain leading to the A record.
+.wen
The option defaults to always checking.
The &(smtp)& transport has two OCSP-related options:
+.new
+.section "Caching of static client configuration items" "SECTclientTLScache"
+.cindex certificate caching
+.cindex privatekey caching
+.cindex crl caching
+.cindex ciphers caching
+.cindex "CA bundle" caching
+.cindex "certificate authorities" caching
+.cindex tls_certificate caching
+.cindex tls_privatekey caching
+.cindex tls_crl caching
+.cindex tls_require_ciphers caching
+.cindex tls_verify_certificate caching
+.cindex caching certificate
+.cindex caching privatekey
+.cindex caching crl
+.cindex caching ciphers
+.cindex caching "certificate authorities
+If any of the transport configuration options &%tls_certificate%&, &%tls_privatekey%&
+and &%tls_crl%& have values with no
+expandable elements,
+then the associated information is loaded per smtp transport
+at daemon startup, at the start of a queue run, or on a
+command-line specified message delivery.
+It is made available
+to child processes forked for handling making SMTP connections.
+
+This caching is currently only supported under Linux.
+
+If caching is not possible, the load
+of the associated information is done at the startup of the TLS connection.
+
+The cache is invalidated in the daemon
+and reloaded after any changes to the directories
+containing files specified by these options.
+
+The information specified by the main option &%tls_verify_certificates%&
+is similarly cached so long as it specifies files explicitly
+or (under GnuTLS) is the string &"system,cache"&.
+The latter case is not automatically invaludated;
+it is the operator's responsibility to arrange for a daemon restart
+any time the system certificate authority bundle is updated.
+A HUP signal is sufficient for this.
+The value &"system"& results in no caching under GnuTLS.
+
+The macro _HAVE_TLS_CA_CACHE will be defined if the suffix for "system"
+is acceptable in configurations for the Exim executavble.
+
+Caching of the system Certificate Authorities bundle can
+save siginificant time and processing on every TLS connection
+initiated by Exim.
+.wen
+
+
+
+
.section "Use of TLS Server Name Indication" "SECTtlssni"
.cindex "TLS" "Server Name Indication"
+.cindex "TLS" SNI
+.cindex SNI
.vindex "&$tls_in_sni$&"
.oindex "&%tls_in_sni%&"
With TLS1.0 or above, there is an extension mechanism by which extra
only point of caution. The &$tls_out_sni$& variable will be set to this string
for the lifetime of the client connection (including during authentication).
+.new
+If DANE validated the connection attempt then the value of the &%tls_sni%& option
+is forced to the domain part of the recipient address.
+.wen
+
Except during SMTP client sessions, if &$tls_in_sni$& is set then it is a string
received from a client.
It can be logged with the &%log_selector%& item &`+tls_sni`&.
0.5.10. (Its presence predates the current API which Exim uses, so if Exim
built, then you have SNI support).
+.new
+.cindex TLS ALPN
+.cindex ALPN "general information"
+.cindex TLS "Application Layer Protocol Names"
+There is a TLS feature related to SNI
+called Application Layer Protocol Name (ALPN).
+This is intended to declare, or select, what protocol layer will be using a TLS
+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
+(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.
+
+As a client Exim does not supply ALPN by default.
+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
+(not all peers can send a feature-specific TLS Alert).
+
+This feature is available when Exim is built with
+OpenSSL 1.1.0 or later or GnuTLS 3.2.0 or later;
+the macro _HAVE_TLS_ALPN will be defined when this is so.
+.wen
+
.section "Multiple messages on the same encrypted TCP/IP connection" &&&
.section "Certificate chains" "SECID186"
-The file named by &%tls_certificate%& may contain more than one
+A file named by &%tls_certificate%& may contain more than one
certificate. This is useful in the case where the certificate that is being
sent is validated by an intermediate certificate which the other end does
not have. Multiple certificates must be in the correct order in the file.
.ecindex IIDencsmtp2
+.new
+.section "TLS Resumption" "SECTresumption"
+.cindex TLS resumption
+TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined
+in RFC 5077 for 1.2). The support for this requires GnuTLS 3.6.3 or OpenSSL 1.1.1
+(or later).
+
+Session resumption (this is the "stateless" variant) involves the server sending
+a "session ticket" to the client on one connection, which can be stored by the
+client and used for a later session. The ticket contains sufficient state for
+the server to reconstruct the TLS session, avoiding some expensive crypto
+calculation and (on TLS1.2) one full packet roundtrip time.
+
+.ilist
+Operational cost/benefit:
+
+ The extra data being transmitted costs a minor amount, and the client has
+ extra costs in storing and retrieving the data.
+
+ In the Exim/Gnutls implementation the extra cost on an initial connection
+ which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware.
+ The saved cost on a subsequent connection is about 4ms; three or more
+ connections become a net win. On longer network paths, two or more
+ connections will have an average lower startup time thanks to the one
+ saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any
+ packet roundtrips.
+
+.cindex "hints database" tls
+ Since a new hints DB is used on the TLS client,
+ the hints DB maintenance should be updated to additionally handle "tls".
+
+.next
+Security aspects:
+
+ The session ticket is encrypted, but is obviously an additional security
+ vulnarability surface. An attacker able to decrypt it would have access
+ all connections using the resumed session.
+ The session ticket encryption key is not committed to storage by the server
+ and is rotated regularly (OpenSSL: 1hr, and one previous key is used for
+ overlap; GnuTLS 6hr but does not specify any overlap).
+ Tickets have limited lifetime (2hr, and new ones issued after 1hr under
+ OpenSSL. GnuTLS 2hr, appears to not do overlap).
+
+ There is a question-mark over the security of the Diffie-Helman parameters
+ used for session negotiation.
+
+.next
+Observability:
+
+ The &%log_selector%& "tls_resumption" appends an asterisk to the tls_cipher "X="
+ element.
+
+ The variables &$tls_in_resumption$& and &$tls_out_resumption$&
+ have bits 0-4 indicating respectively
+ support built, client requested ticket, client offered session,
+ server issued ticket, resume used. A suitable decode list is provided
+ in the builtin macro _RESUME_DECODE for in &%listextract%& expansions.
+
+.next
+Control:
+
+The &%tls_resumption_hosts%& main option specifies a hostlist for which
+exim, operating as a server, will offer resumption to clients.
+Current best practice is to not offer the feature to MUA connection.
+Commonly this can be done like this:
+.code
+tls_resumption_hosts = ${if inlist {$received_port}{587:465} {:}{*}}
+.endd
+If the peer host matches the list after expansion then resumption
+is offered and/or accepted.
+
+The &%tls_resumption_hosts%& smtp transport option performs the
+equivalent function for operation as a client.
+If the peer host matches the list after expansion then resumption
+is attempted (if a stored session is available) or the information
+stored (if supplied by the peer).
+
+
+.next
+Issues:
+
+ In a resumed session:
+.ilist
+ The variables &$tls_{in,out}_cipher$& will have values different
+ to the original (under GnuTLS).
+.next
+ The variables &$tls_{in,out}_ocsp$& will be "not requested" or "no response",
+ and the &%hosts_require_ocsp%& smtp trasnport option will fail.
+. XXX need to do something with that hosts_require_ocsp
+.endlist
+
+.endlist
+.wen
+
.section DANE "SECDANE"
.cindex DANE
It also allows the server to declare (implicitly) that connections to it should use TLS. An MITM could simply
fail to pass on a server's STARTTLS.
-DANE scales better than having to maintain (and side-channel communicate) copies of server certificates
+DANE scales better than having to maintain (and communicate via side-channel) copies of server certificates
for every possible target server. It also scales (slightly) better than having to maintain on an SMTP
client a copy of the standard CAs bundle. It also means not having to pay a CA for certificates.
DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records.
-A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using dnssec.
+A TLSA lookup will be done if either of the above options match and the host-lookup succeeded using DNSSEC.
If a TLSA lookup is done and succeeds, a DANE-verified TLS connection
will be required for the host. If it does not, the host will not
be used; there is no fallback to non-DANE or non-TLS.
tls_verify_certificates
tls_crl
tls_verify_cert_hostnames
+ tls_sni
.endd
If DANE is not usable, whether requested or not, and CA-anchored
response.
.vindex "&$acl_verify_message$&"
-For ACLs that are called by an &%acl =%& ACL condition, the message is
-stored in &$acl_verify_message$&, from which the calling ACL may use it.
+.new
+While the text is being expanded, the &$acl_verify_message$& variable
+contains any message previously set.
+Afterwards, &$acl_verify_message$& is cleared.
+.wen
If &%message%& is used on a statement that verifies an address, the message
specified overrides any message that is generated by the verification process.
controlled by &%acl_smtp_connect%& or &%acl_smtp_helo%&. See also
&%pipelining_advertise_hosts%&.
-.new
.vitem &*control&~=&~queue/*&<&'options'&>* &&&
&*control&~=&~queue_only*&
.oindex "&%queue%&"
The control only applies to the current message, not to any subsequent ones that
may be received in the same SMTP connection.
-.wen
.vitem &*control&~=&~submission/*&<&'options'&>
.cindex "message" "submission"
non-SMTP ACLs. It causes the incoming message to be scanned for a match with
any of the regular expressions. For details, see chapter &<<CHAPexiscan>>&.
+.new
+.vitem &*seen&~=&~*&<&'parameters'&>
+.cindex "&%sseen%& ACL condition"
+This condition can be used to test if a situation has been previously met,
+for example for greylisting.
+Details are given in section &<<SECTseen>>&.
+.wen
+
.vitem &*sender_domains&~=&~*&<&'domain&~list'&>
.cindex "&%sender_domains%& ACL condition"
.cindex "sender" "ACL checking"
.cindex "header lines" "verifying header names only ASCII"
.cindex "verifying" "header names only ASCII"
This condition is relevant only in an ACL that is run after a message has been
-received, that is, in an ACL specified by &%acl_smtp_data%& or
-&%acl_not_smtp%&. It checks all header names (not the content) to make sure
+received.
+This usually means an ACL specified by &%acl_smtp_data%& or &%acl_not_smtp%&.
+It checks all header names (not the content) to make sure
there are no non-ASCII characters, also excluding control characters. The
allowable characters are decimal ASCII values 33 through 126.
(eg. is generated from the received message)
they must be protected from the options parsing by doubling:
.code
-verify = sender=${sg{${address:$h_sender:}}{/}{//}}
+verify = sender=${listquote{/}{${address:$h_sender:}}}
.endd
.endlist
different values. Some DNS lists may return more than one address record;
see section &<<SECThanmuldnsrec>>& for details of how they are checked.
+.new
+Values returned by a properly running DBSBL should be in the 127.0.0.0/8
+range. If a DNSBL operator loses control of the domain, lookups on it
+may start returning other addresses. Because of this, Exim now ignores
+returned values outside the 127/8 region.
+.wen
+
.section "Variables set from DNS lists" "SECID204"
.cindex "expansion" "variables, set from DNS list"
.endd
which is less clear, and harder to maintain.
+Negation can also be used with a bitwise-and restriction.
+The dnslists condition with only be trus if a result is returned
+by the lookup which, anded with the restriction, is all zeroes.
+For example:
+.code
+deny dnslists = zen.spamhaus.org!&0.255.255.0
+.endd
+
dnslists = <; dnsbl.example.com/<|$acl_m_addrslist
.endd
+
+.new
+.section "Previously seen user and hosts" "SECTseen"
+.cindex "&%sseen%& ACL condition"
+.cindex greylisting
+The &%seen%& ACL condition can be used to test whether a
+situation has been previously met.
+It uses a hints database to record a timestamp against a key.
+host. The syntax of the condition is:
+.display
+&`seen =`& <&'time interval'&> &`/`& <&'options'&>
+.endd
+
+For example,
+.code
+defer seen = -5m / key=${sender_host_address}_$local_part@$domain
+.endd
+in a RCPT ACL will implement simple greylisting.
+
+The parameters for the condition
+are an interval followed, slash-separated, by a list of options.
+The interval is taken as an offset before the current time,
+and used for the test.
+If the interval is preceded by a minus sign then the condition returns
+whether a record is found which is before the test time.
+Otherwise, the condition returns whether one is found which is since the
+test time.
+
+Options are read in order with later ones overriding earlier ones.
+
+The default key is &$sender_host_address$&.
+An explicit key can be set using a &%key=value%& option.
+
+If a &%readonly%& option is given then
+no record create or update is done.
+If a &%write%& option is given then
+a record create or update is always done.
+An update is done if the test is for &"since"&.
+
+Creates and updates are marked with the current time.
+
+Finally, a &"before"& test which succeeds, and for which the record
+is old enough, will be refreshed with a timestamp of the test time.
+This can prevent tidying of the database from removing the entry.
+The interval for this is, by default, 10 days.
+An explicit interval can be set using a
+&%refresh=value%& option.
+
+Note that &"seen"& should be added to the list of hints databases
+for maintenance if this ACL condition is used.
+.wen
+
+
.section "Rate limiting incoming messages" "SECTratelimiting"
.cindex "rate limiting" "client sending"
.cindex "limiting client sending rates"
The &%per_rcpt%& option causes Exim to limit the rate at which recipients are
accepted. It can be used in the &%acl_smtp_rcpt%&, &%acl_smtp_predata%&,
-&%acl_smtp_mime%&, &%acl_smtp_data%&, or &%acl_smtp_rcpt%& ACLs. In
+&%acl_smtp_mime%&, or &%acl_smtp_data%& ACLs. In
&%acl_smtp_rcpt%& the rate is updated one recipient at a time; in the other
ACLs the rate is updated with the total (accepted) recipient count in one go. Note that
in either case the rate limiting engine will see a message with many
immediately after a successful redirection. By default, if a redirection
generates just one address, that address is also verified. See further
discussion in section &<<SECTredirwhilveri>>&.
+.new
+.next
+If the &%quota%& option is specified for recipient verify,
+successful routing to an appendfile transport is followed by a call into
+the transport to evaluate the quota status for the recipient.
+No actual delivery is done, but verification will succeed if the quota
+is sufficient for the message (if the sender gave a message size) or
+not already exceeded (otherwise).
+.wen
.endlist
.cindex "verifying address" "differentiating failures"
If you are writing your own custom rejection message or log message when
denying access, you can use this variable to include information about the
verification failure.
+This variable is cleared at the end of processing the ACL verb.
In addition, &$sender_verify_failure$& or &$recipient_verify_failure$& (as
appropriate) contains one of the following words:
&%recipient%&: The RCPT command in a callout was rejected.
.next
&%postmaster%&: The postmaster check in a callout was rejected.
+.new
+.next
+&%quota%&: The quota check for a local recipient did non pass.
.endlist
The main use of these variables is expected to be to distinguish between
+.new
+.section "Quota caching" "SECTquotacache"
+.cindex "hints database" "quota cache"
+.cindex "quota" "cache, description of"
+.cindex "caching" "quota"
+Exim caches the results of quota verification
+in order to reduce the amount of resources used.
+The &"callout"& hints database is used.
+
+The default cache periods are five minutes for a positive (good) result
+and one hour for a negative result.
+To change the periods the &%quota%& option can be followed by an equals sign
+and a number of optional paramemters, separated by commas.
+For example:
+.code
+verify = recipient/quota=cachepos=1h,cacheneg=1d
+.endd
+Possible parameters are:
+.vlist
+.vitem &*cachepos&~=&~*&<&'time&~interval'&>
+.cindex "quota cache" "positive entry expiry, specifying"
+Set the lifetime for a positive cache entry.
+A value of zero seconds is legitimate.
+
+.vitem &*cacheneg&~=&~*&<&'time&~interval'&>
+.cindex "quota cache" "negative entry expiry, specifying"
+As above, for a negative entry.
+
+.vitem &*no_cache*&
+Set both positive and negative lifetimes to zero.
+.wen
+
.section "Sender address verification reporting" "SECTsenaddver"
.cindex "verifying" "suppressing error details"
See section &<<SECTaddressverification>>& for a general discussion of
LOCAL_SCAN_SOURCE=Local/local_scan.c
.endd
for example. The function must be called &[local_scan()]&;
-.new
the source file(s) for it should first #define LOCAL_SCAN
and then #include "local_scan.h".
-.wen
It is called by
Exim after it has received a message, when the success return code is about to
be sent. This is after all the ACLs have been run. The return code from your
arguments. It flushes the output stream, and returns a non-zero value if there
is an error.
-.new
.vitem &*void&~*store_get(int,BOOL)*&
This function accesses Exim's internal store (memory) manager. It gets a new
chunk of memory whose size is given by the first argument.
FALSE if it is locally-sourced.
Exim bombs out if it ever
runs out of memory. See the next section for a discussion of memory handling.
-.wen
.vitem &*void&~*store_get_perm(int,BOOL)*&
This function is like &'store_get()'&, but it always gets memory from the
.section "Per-address filtering" "SECTperaddfil"
-.vindex "&$domain$&"
-.vindex "&$local_part$&"
+.vindex "&$domain_data$&"
+.vindex "&$local_part_data$&"
In contrast to the system filter, which is run just once per message for each
delivery attempt, it is also possible to set up a system-wide filtering
operation that runs once for each recipient address. In this case, variables
-such as &$local_part$& and &$domain$& can be used, and indeed, the choice of
-filter file could be made dependent on them. This is an example of a router
-which implements such a filter:
+such as &$local_part_data$& and &$domain_data$& can be used,
+and indeed, the choice of filter file could be made dependent on them.
+This is an example of a router which implements such a filter:
.code
central_filter:
check_local_user
.section "Resent- header lines" "SECID220"
-.cindex "&%Resent-%& header lines"
-.cindex "header lines" "Resent-"
+.chindex Resent-
RFC 2822 makes provision for sets of header lines starting with the string
&`Resent-`& to be added to a message when it is resent by the original
recipient to somebody else. These headers are &'Resent-Date:'&,
.section "The Date: header line" "SECID223"
-.cindex "&'Date:'& header line"
-.cindex "header lines" "Date:"
+.cindex Date:
If a locally-generated or submission-mode message has no &'Date:'& header line,
Exim adds one, using the current date and time, unless the
&%suppress_local_fixups%& control has been specified.
.section "The Envelope-to: header line" "SECID225"
-.cindex "&'Envelope-to:'& header line"
-.cindex "header lines" "Envelope-to:"
+.chindex Envelope-to:
.oindex "&%envelope_to_remove%&"
&'Envelope-to:'& header lines are not part of the standard RFC 2822 header set.
Exim can be configured to add them to the final delivery of messages. (See the
.section "The From: header line" "SECTthefrohea"
-.cindex "&'From:'& header line"
-.cindex "header lines" "From:"
+.chindex From:
.cindex "Sendmail compatibility" "&""From""& line"
.cindex "message" "submission"
.cindex "submission mode"
.section "The Message-ID: header line" "SECID226"
-.cindex "&'Message-ID:'& header line"
-.cindex "header lines" "Message-ID:"
+.chindex Message-ID:
.cindex "message" "submission"
.oindex "&%message_id_header_text%&"
If a locally-generated or submission-mode incoming message does not contain a
.section "The Received: header line" "SECID227"
-.cindex "&'Received:'& header line"
-.cindex "header lines" "Received:"
+.chindex Received:
A &'Received:'& header line is added at the start of every message. The
contents are defined by the &%received_header_text%& configuration option, and
Exim automatically adds a semicolon and a timestamp to the configured string.
.section "The References: header line" "SECID228"
-.cindex "&'References:'& header line"
-.cindex "header lines" "References:"
+.chindex References:
Messages created by the &(autoreply)& transport include a &'References:'&
header line. This is constructed according to the rules that are described in
section 3.64 of RFC 2822 (which states that replies should contain such a
.section "The Return-path: header line" "SECID229"
-.cindex "&'Return-path:'& header line"
-.cindex "header lines" "Return-path:"
+.chindex Return-path:
.oindex "&%return_path_remove%&"
&'Return-path:'& header lines are defined as something an MTA may insert when
it does the final delivery of messages. (See the generic &%return_path_add%&
.section "The Sender: header line" "SECTthesenhea"
.cindex "&'Sender:'& header line"
.cindex "message" "submission"
-.cindex "header lines" "Sender:"
+.chindex Sender:
For a locally-originated message from an untrusted user, Exim may remove an
existing &'Sender:'& header line, and it may add a new one. You can modify
these actions by setting the &%local_sender_retain%& option true, the
data = ${lookup{$local_part}lsearch{/etc/mail/virtual/$domain_data}}
no_more
.endd
-.new
The &%domains%& option specifies that the router is to be skipped, unless there
is a file in the &_/etc/mail/virtual_& directory whose name is the same as the
domain that is being processed.
The &(dsearch)& lookup used results in an untainted version of &$domain$&
being placed into the &$domain_data$& variable.
-.wen
When the router runs, it looks up the local
part in the file to find a new address (or list of addresses). The &%no_more%&
.code
my_mailboxes:
driver = appendfile
- file = /var/mail/$domain/$local_part_data
+ file = /var/mail/$domain_data/$local_part_data
user = mail
.endd
This uses a directory of mailboxes for each domain. The &%user%& setting is
cases by testing the variable &$local_part_suffix$&. For example:
.code
if $local_part_suffix contains -special then
-save /home/$local_part/Mail/special
+save /home/$local_part_data/Mail/special
endif
.endd
If the filter file does not exist, or does not deal with such addresses, they
When Exim encounters an empty item in the list, it searches the list defined by
LOG_FILE_PATH, and uses the first item it finds that is neither empty nor
&"syslog"&. This means that an empty item in &%log_file_path%& can be used to
-mean &"use the path specified at build time"&. It no such item exists, log
+mean &"use the path specified at build time"&. If no such item exists, log
files are written in the &_log_& subdirectory of the spool directory. This is
equivalent to the setting:
.code
If SMTP AUTH was used for the delivery there is an additional item A=
followed by the name of the authenticator that was used.
If an authenticated identification was set up by the authenticator's &%client_set_id%&
-option, this is logged too, separated by a colon from the authenticator name.
+option, this is logged too, as a second colon-separated list item.
+Optionally (see the &%smtp_mailauth%& &%log_selector%&) there may be a third list item.
If a shadow transport was run after a successful local delivery, the log line
for the successful delivery has an item added on the end, of the form
When more than one address is included in a single delivery (for example, two
SMTP RCPT commands in one transaction) the second and subsequent addresses are
flagged with &`->`& instead of &`=>`&. When two or more messages are delivered
-down a single SMTP connection, an asterisk follows the IP address in the log
-lines for the second and subsequent messages.
+down a single SMTP connection, an asterisk follows the
+.new
+remote IP address (and port if enabled)
+.wen
+in the log lines for the second and subsequent messages.
When two or more messages are delivered down a single TLS connection, the
DNS and some TLS-related information logged for the first message delivered
will not be present in the log lines for the second and subsequent messages.
&` outgoing_port `& add remote port to => lines
&`*queue_run `& start and end queue runs
&` queue_time `& time on queue for one recipient
+&`*queue_time_exclusive `& exclude recieve time from QT times
&` queue_time_overall `& time on queue for whole message
&` pid `& Exim process id
&` pipelining `& PIPELINING use, on <= and => lines
&` smtp_protocol_error `& SMTP protocol errors
&` smtp_syntax_error `& SMTP syntax errors
&` subject `& contents of &'Subject:'& on <= lines
+&`*taint `& taint errors or warnings
&`*tls_certificate_verified `& certificate verification status
&`*tls_cipher `& TLS cipher suite on <= and => lines
&` tls_peerdn `& TLS peer DN on <= and => lines
+&` tls_resumption `& append * to cipher field
&` tls_sni `& TLS SNI on <= lines
&` unknown_in_list `& DNS lookup failed in list match
client's ident port times out.
.next
.cindex "log" "incoming interface"
+.cindex "log" "outgoing interface"
.cindex "log" "local interface"
.cindex "log" "local address and port"
.cindex "TCP/IP" "logging local address and port"
to the &"<="& line as an IP address in square brackets, tagged by I= and
followed by a colon and the port number. The local interface and port are also
added to other SMTP log lines, for example, &"SMTP connection from"&, to
-rejection lines, and (despite the name) to outgoing &"=>"& and &"->"& lines.
+rejection lines, and (despite the name) to outgoing
+.new
+&"=>"&, &"->"&, &"=="& and &"**"& lines.
+.wen
The latter can be disabled by turning off the &%outgoing_interface%& option.
.next
.cindex log "incoming proxy address"
.cindex "log" "queue time"
&%queue_time%&: The amount of time the message has been in the queue on the
local host is logged as QT=<&'time'&> on delivery (&`=>`&) lines, for example,
-&`QT=3m45s`&. The clock starts when Exim starts to receive the message, so it
-includes reception time as well as the delivery time for the current address.
-This means that it may be longer than the difference between the arrival and
-delivery log line times, because the arrival log line is not written until the
-message has been successfully received.
+&`QT=3m45s`&.
If millisecond logging is enabled, short times will be shown with greater
precision, eg. &`QT=1.578s`&.
.next
&%queue_time_overall%&: The amount of time the message has been in the queue on
the local host is logged as QT=<&'time'&> on &"Completed"& lines, for
-example, &`QT=3m45s`&. The clock starts when Exim starts to receive the
-message, so it includes reception time as well as the total delivery time.
+example, &`QT=3m45s`&.
.next
.cindex "log" "receive duration"
&%receive_time%&: For each message, the amount of real time it has taken to
.cindex "log" "frozen messages; skipped"
.cindex "frozen messages" "logging skipping"
&%skip_delivery%&: A log line is written whenever a message is skipped during a
-queue run because it is frozen or because another process is already delivering
-it.
+queue run because it another process is already delivering it or because
+it is frozen.
.cindex "&""spool file is locked""&"
-The message that is written is &"spool file is locked"&.
+.cindex "&""message is frozen""&"
+The message that is written is either &"spool file is locked"& or
+&"message is frozen"&.
.next
.cindex "log" "smtp confirmation"
.cindex "SMTP" "logging confirmation"
when TLS is in use. The item is &`CV=yes`& if the peer's certificate was
verified
using a CA trust anchor,
-&`CA=dane`& if using a DNS trust anchor,
+&`CV=dane`& if using a DNS trust anchor,
and &`CV=no`& if not.
.next
+.cindex "log" "Taint warnings"
+&%taint%&: Log warnings about tainted data. This selector can't be
+turned of if &%allow_insecure_tainted_data%& is false (which is the
+default).
+.next
.cindex "log" "TLS cipher"
.cindex "TLS" "logging cipher"
&%tls_cipher%&: When a message is sent or received over an encrypted
connection, and a certificate is supplied by the remote host, the peer DN is
added to the log line, preceded by DN=.
.next
+.cindex "log" "TLS resumption"
+.cindex "TLS" "logging session resumption"
+.new
+&%tls_resumption%&: When a message is sent or received over an encrypted
+connection and the TLS session resumed one used on a previous TCP connection,
+an asterisk is appended to the X= cipher field in the log line.
+.wen
+.next
.cindex "log" "TLS SNI"
.cindex "TLS" "logging SNI"
+.cindex SNI logging
&%tls_sni%&: When a message is received over an encrypted connection, and
the remote host provided the Server Name Indication extension, the SNI is
added to the log line, preceded by SNI=.
"check address acceptance from given IP"
.irow &<<SECTdbmbuild>>& &'exim_dbmbuild'& "build a DBM file"
.irow &<<SECTfinindret>>& &'exinext'& "extract retry information"
-.irow &<<SECThindatmai>>& &'exim_dumpdb'& "dump a hints database"
-.irow &<<SECThindatmai>>& &'exim_tidydb'& "clean up a hints database"
-.irow &<<SECThindatmai>>& &'exim_fixdb'& "patch a hints database"
+.irow &<<SECTdumpdb>>& &'exim_dumpdb'& "dump a hints database"
+.irow &<<SECTtidydb>>& &'exim_tidydb'& "clean up a hints database"
+.irow &<<SECTfixdb>>& &'exim_fixdb'& "patch a hints database"
.irow &<<SECTmailboxmaint>>& &'exim_lock'& "lock a mailbox file"
.endtable
.next
&'ratelimit'&: the data for implementing the ratelimit ACL condition
.next
+.new
+&'tls'&: TLS session resumption data
+.wen
+.next
&'misc'&: other hints data
.endlist
-.section "exim_dumpdb" "SECID261"
+.section "exim_dumpdb" "SECTdumpdb"
.cindex "&'exim_dumpdb'&"
The entire contents of a database are written to the standard output by the
-&'exim_dumpdb'& program, which has no options or arguments other than the
-spool and database names. For example, to dump the retry database:
+&'exim_dumpdb'& program,
+.new
+taking as arguments the spool and database names.
+An option &'-z'& may be given to regest times in UTC;
+otherwise times are in the local timezone.
+.wen
+For example, to dump the retry database:
.code
exim_dumpdb /var/spool/exim retry
.endd
-.section "exim_tidydb" "SECID262"
+.section "exim_tidydb" "SECTtidydb"
.cindex "&'exim_tidydb'&"
The &'exim_tidydb'& utility program is used to tidy up the contents of a hints
database. If run with no options, it removes all records that are more than 30
-.section "exim_fixdb" "SECID263"
+.section "exim_fixdb" "SECTfixdb"
.cindex "&'exim_fixdb'&"
The &'exim_fixdb'& program is a utility for interactively modifying databases.
Its main use is for testing Exim, but it might also be occasionally useful for
-getting round problems in a live system. It has no options, and its interface
+getting round problems in a live system. Its interface
is somewhat crude. On entry, it prompts for input with a right angle-bracket. A
key of a database record can then be entered, and the data for that record is
displayed.
sequence of digit pairs for year, month, day, hour, and minute. Colons can be
used as optional separators.
+.new
+Both displayed and input times are in the local timezone by default.
+If an option &'-z'& is used on the command line, displayed times
+are in UTC.
+.wen
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
-.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&&
- "DKIM, SPF and DMARC Support"
+.chapter "DKIM, SPF, SRS and DMARC" "CHAPdkim" &&&
+ "DKIM, SPF, SRS and DMARC Support"
.section "DKIM (DomainKeys Identified Mail)" SECDKIM
.cindex "DKIM"
Signing is enabled by setting private options on the SMTP transport.
These options take (expandable) strings as arguments.
-.option dkim_domain smtp string list&!! unset
+.option dkim_domain smtp "string list&!!" unset
The domain(s) you want to sign with.
After expansion, this can be a list.
Each element in turn,
If it is empty after expansion, DKIM signing is not done,
and no error will result even if &%dkim_strict%& is set.
-.option dkim_selector smtp string list&!! unset
+.option dkim_selector smtp "string list&!!" unset
This sets the key selector string.
After expansion, which can use &$dkim_domain$&, this can be a list.
Each element in turn is put in the expansion
If the option is empty after expansion, DKIM signing is not done for this domain,
and no error will result even if &%dkim_strict%& is set.
+.new
+To do, for example, dual-signing with RSA and EC keys
+this could be be used:
+.code
+dkim_selector = ec_sel : rsa_sel
+dkim_private_key = KEYS_DIR/$dkim_selector
+.endd
+.wen
+
.option dkim_private_key smtp string&!! unset
This sets the private key to use.
You can use the &%$dkim_domain%& and
whether or not each header is present in the message.
The default list is available for the expansion in the macro
&"_DKIM_SIGN_HEADERS"&
-.new
and an oversigning variant is in &"_DKIM_OVERSIGN_HEADERS"&.
-.wen
If a name is repeated, multiple headers by that name (or the absence thereof)
will be signed. The textually later headers in the headers part of the
.vitem &%$dkim_key_length%&
Number of bits in the key.
-.new
Valid only once the key is loaded, which is at the time the header signature
is verified, which is after the body hash is.
-.wen
Note that RFC 8301 says:
.code
.vitem &%temperror%&
This indicates a temporary error during all processing, including Exim's
SPF processing. You may defer messages when this occurs.
+
+.vitem &%invalid%&
+There was an error during processing of the SPF lookup
.endlist
You can prefix each string with an exclamation mark to invert
.vitem &$spf_received$&
.vindex &$spf_received$&
- This contains a complete Received-SPF: header that can be
- added to the message. Please note that according to the SPF
- draft, this header must be added at the top of the header
- list. Please see section 10 on how you can do this.
+ This contains a complete Received-SPF: header (name and
+ content) that can be added to the message. Please note that
+ according to the SPF draft, this header must be added at the
+ top of the header list, i.e. with
+.code
+add_header = :at_start:$spf_received
+.endd
+ See section &<<SECTaddheadacl>>& for further details.
Note: in case of "Best-guess" (see below), the convention is
to put this string in a header called X-SPF-Guess: instead.
.vitem &$spf_result$&
.vindex &$spf_result$&
This contains the outcome of the SPF check in string form,
- one of pass, fail, softfail, none, neutral, permerror or
- temperror.
+ currently one of pass, fail, softfail, none, neutral, permerror,
+ temperror, or &"(invalid)"&.
.vitem &$spf_result_guessed$&
.vindex &$spf_result_guessed$&
.vindex &%spf_smtp_comment_template%&
This contains a string that can be used in a SMTP response
to the calling party. Useful for "fail".
-.new
The string is generated by the SPF library from the template configured in the main config
option &%spf_smtp_comment_template%&.
-.wen
.endlist
+.section "SRS (Sender Rewriting Scheme)" SECTSRS
+.cindex SRS "sender rewriting scheme"
+
+.new
+SRS can be used to modify sender addresses when forwarding so that
+SPF verification does not object to them.
+It operates by encoding the original envelope sender in a new
+sender local part and using a domain run by the forwarding site
+as the new domain for the sender. Any DSN message should be returned
+to this new sender at the forwarding site, which can extract the
+original sender from the coded local part and forward the DSN to
+the originator.
+
+This is a way of avoiding the breakage that SPF does to forwarding.
+The constructed local-part will be longer than the original,
+leading to possible problems with very long addresses.
+The changing of the sender address also hinders the tracing of mail
+problems.
+
+Exim can be built to include native SRS support. To do this
+SUPPORT_SRS=yes must be defined in &_Local/Makefile_&.
+If this has been done, the macros _HAVE_SRS and _HAVE_NATIVE_SRS
+will be defined.
+The support is limited to SRS0-encoding; SRS1 is not supported.
+
+.cindex SRS excoding
+To encode an address use this expansion item:
+.vlist
+.vitem &*${srs_encode&~{*&<&'secret'&>&*}{*&<&'return&~path'&>&*}{*&<&'original&~domain'&>&*}}*&
+.cindex "&%srs_encode%& expansion item"
+.cindex SRS "expansion item"
+The first argument should be a secret known and used by all systems
+handling the recipient domain for the original message.
+There is no need to periodically change this key; a timestamp is also
+encoded.
+The second argument should be given as the envelope sender address before this
+encoding operation.
+The third argument should be the recipient domain of the message when
+it arrived at this system.
+.endlist
+
+.cindex SRS decoding
+To decode an address use this expansion condition:
+.vlist
+.vitem &*inbound_srs&~{*&<&'local&~part'&>&*}{*&<&'secret'&>&*}*&
+The first argument should be the recipient local prt as is was received.
+The second argument is the site secret.
+
+If the messages is not for an SRS-encoded recipient the condition will
+return false. If it is, the condition will return true and the variable
+&$srs_recipient$& will be set to the decoded (original) value.
+.endlist
+
+Example usage:
+.code
+ #macro
+ SRS_SECRET = <pick something unique for your site for this. Use on all MXs.>
+
+ #routers
+
+ outbound:
+ driver = dnslookup
+ # if outbound, and forwarding has been done, use an alternate transport
+ domains = ! +my_domains
+ transport = ${if eq {$local_part@$domain} \
+ {$original_local_part@$original_domain} \
+ {remote_smtp} {remote_forwarded_smtp}}
+
+ inbound_srs:
+ driver = redirect
+ senders = :
+ domains = +my_domains
+ # detect inbound bounces which are SRS'd, and decode them
+ condition = ${if inbound_srs {$local_part} {SRS_SECRET}}
+ data = $srs_recipient
+
+ inbound_srs_failure:
+ driver = redirect
+ senders = :
+ domains = +my_domains
+ # detect inbound bounces which look SRS'd but are invalid
+ condition = ${if inbound_srs {$local_part} {}}
+ allow_fail
+ data = :fail: Invalid SRS recipient address
+
+ #... further routers here
+
+
+ # transport; should look like the non-forward outbound
+ # one, plus the max_rcpt and return_path options
+ remote_forwarded_smtp:
+ driver = smtp
+ # modify the envelope from, for mails that we forward
+ max_rcpt = 1
+ return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}}
+.endd
+
+
+.wen
+
+
+
.section DMARC SECDMARC
.cindex DMARC verification
the most current version can be downloaded
from a link at &url(https://publicsuffix.org/list/public_suffix_list.dat).
See also the util/renew-opendmarc-tlds.sh script.
-.new
The default for the option is unset.
If not set, DMARC processing is disabled.
-.wen
The &%dmarc_history_file%& option, if set
&'reject '& The DMARC check failed and the library recommends rejecting the email.
&'quarantine '& The DMARC check failed and the library recommends keeping it for further inspection.
&'none '& The DMARC check passed and the library recommends no specific action, neutral.
-&'norecord '& No policy section in the DMARC record for this sender domain.
+&'norecord '& No policy section in the DMARC record for this RFC5322.From field
&'nofrom '& Unable to determine the domain of the sender.
&'temperror '& Library error or dns error.
&'off '& The DMARC check was disabled for this email.
The Proxy Protocol header is the first data received on a TCP connection
and is inserted before any TLS-on-connect handshake from the client; Exim
negotiates TLS between Exim-as-server and the remote client, not between
-Exim and the proxy server.
+Exim and the proxy server. The Proxy Protocol header must be received
+within &%proxy_protocol_timeout%&, which defaults to 3s.
The following expansion variables are usable
(&"internal"& and &"external"& here refer to the interfaces
The name is placed in the variable &$event_name$& and the event action
expansion must check this, as it will be called for every possible event type.
-.new
The current list of events is:
-.wen
.display
&`dane:fail after transport `& per connection
&`msg:complete after main `& per message
git://git.exim.org / exim.git / blobdiff