the actual building takes place. In most cases, Exim can discover the machine
architecture and operating system for itself, but the defaults can be
overridden if necessary.
+.cindex compiler requirements
+.cindex compiler version
+A C99-capable compiler will be required for the build.
.section "PCRE library" "SECTpcre"
the same lookup again. Otherwise, because each Exim process caches the results
of lookups, you will just get the same result as before.
+.new
+Macro processing is done on lines before string-expansion: new macros can be
+defined and macros will be expanded.
+Because macros in the config file are often used for secrets, those are only
+available to admin users.
+.wen
+
.vitem &%-bem%&&~<&'filename'&>
.oindex "&%-bem%&"
.cindex "testing" "string expansion"
SMTP protocol names (see the description of &$received_protocol$& in section
&<<SECTexpvar>>&). For &%-bs%&, the protocol is always &"local-"& followed by
one of those same names. For &%-bS%& (batched SMTP) however, the protocol can
-be set by &%-oMr%&.
+be set by &%-oMr%&. Repeated use of this option is not supported.
.vitem &%-oMs%&&~<&'host&~name'&>
.oindex "&%-oMs%&"
Note the Exim already has two private options, &%-pd%& and &%-ps%&, that refer
to embedded Perl. It is therefore impossible to set a protocol value of &`d`&
or &`s`& using this option (but that does not seem a real limitation).
+Repeated use of this option is not supported.
.vitem &%-q%&
.oindex "&%-q%&"
${sg{abcdefabcdef}{abc}{xyz}}
.endd
yields &"xyzdefxyzdef"&. Because all three arguments are expanded before use,
-if any $ or \ characters are required in the regular expression or in the
+if any $, } or \ characters are required in the regular expression or in the
substitution string, they have to be escaped. For example:
.code
${sg{abcdef}{^(...)(...)\$}{\$2\$1}}
.code
${addresses:>& Chief <ceo@up.stairs>, sec@base.ment (dogsbody)}
.endd
-expands to &`ceo@up.stairs&&sec@base.ment`&. Compare the &*address*& (singular)
+expands to &`ceo@up.stairs&&sec@base.ment`&. The string is expanded
+first, so if the expanded string starts with >, it may change the output
+separator unintentionally. This can be avoided by setting the output
+separator explicitly:
+.code
+${addresses:>:$h_from:}
+.endd
+
+Compare the &*address*& (singular)
expansion item, which extracts the working address from a single RFC2822
address. See the &*filter*&, &*map*&, and &*reduce*& items for ways of
processing lists.
${if match_domain{a.b.c}{x.y.z:a.b.c:p.q.r}{yes}{no}}
.endd
In each case, the second argument may contain any of the allowable items for a
-list of the appropriate type. Also, because the second argument (after
-expansion) is a standard form of list, it is possible to refer to a named list.
+list of the appropriate type. Also, because the second argument
+is a standard form of list, it is possible to refer to a named list.
Thus, you can use conditions like this:
.code
${if match_domain{$domain}{+local_domains}{...
.vindex "&$config_file$&"
The name of the main configuration file Exim is using.
+.vitem &$dkim_verify_status$& &&&
+Results of DKIM verification.
+For details see chapter &<<CHAPdkim>>&.
+
.vitem &$dkim_cur_signer$& &&&
- &$dkim_verify_status$& &&&
&$dkim_verify_reason$& &&&
&$dkim_domain$& &&&
&$dkim_identity$& &&&
This variable contains the number of bytes in the longest line that was
received as part of the message, not counting the line termination
character(s).
+.new
+It is not valid if the &%spool_files_wireformat%& option is used.
+.wen
.vitem &$message_age$&
.cindex "message" "age of"
separates the body from the header. Newlines are included in the count. See
also &$message_size$&, &$body_linecount$&, and &$body_zerocount$&.
+.new
+If the spool file is wireformat
+(see the &%spool_files_wireformat%& main option)
+the CRLF line-terminators are included in the count.
+.wen
+
.vitem &$message_exim_id$&
.vindex "&$message_exim_id$&"
When a message is being received or delivered, this variable contains the
In the MAIL and RCPT ACLs, the value is zero because at that stage the
message has not yet been received.
+.new
+This variable is not valid if the &%spool_files_wireformat%& option is used.
+.wen
+
.vitem &$message_size$&
.cindex "size" "of message"
.cindex "message" "size"
space removed. Following the introduction of &$smtp_command$&, this variable is
somewhat redundant, but is retained for backwards compatibility.
+.new
+.vitem &$smtp_command_history$&
+.cindex SMTP "command history"
+.vindex "&$smtp_command_history$&"
+A comma-separated list (with no whitespace) of the most-recent SMTP commands
+received, in time-order left to right. Only a limited number of commands
+are remembered.
+.wen
+
.vitem &$smtp_count_at_connection_start$&
.vindex "&$smtp_count_at_connection_start$&"
This variable is set greater than zero only in processes spawned by the Exim
&%certextract%& expansion item, &%md5%&, &%sha1%& or &%sha256%& operator,
or a &%def%& condition.
+.new
+&*Note*&: Under current versions of OpenSSL, when a list of more than one
+file is used for &%tls_certificate%&, this variable is not reliable.
+.wen
+
.vitem &$tls_in_peercert$&
.vindex "&$tls_in_peercert$&"
This variable refers to the certificate presented by the peer of an
.section "Privilege controls" "SECID98"
.table2
.row &%admin_groups%& "groups that are Exim admin users"
+.row &%commandline_checks_require_admin%& "require admin for various checks"
.row &%deliver_drop_privilege%& "drop root for delivery processes"
.row &%local_from_check%& "insert &'Sender:'& if necessary"
.row &%local_from_prefix%& "for testing &'From:'& for local sender"
these hosts.
Hosts may use the BDAT command as an alternate to DATA.
+.new
+.option commandline_checks_require_admin main boolean &`false`&
+.cindex "restricting access to features"
+This option restricts various basic checking features to require an
+administrative user.
+This affects most of the &%-b*%& options, such as &%-be%&.
+.wen
+
.option debug_store main boolean &`false`&
.cindex debugging "memory corruption"
.cindex memory debugging
.option prod_requires_admin main boolean true
+.cindex "restricting access to features"
.oindex "&%-M%&"
.oindex "&%-R%&"
.oindex "&%-q%&"
The &%-M%&, &%-R%&, and &%-q%& command-line options require the caller to be an
admin user unless &%prod_requires_admin%& is set false. See also
-&%queue_list_requires_admin%&.
+&%queue_list_requires_admin%& and &%commandline_checks_require_admin%&.
.option qualify_domain main string "see below"
.option queue_list_requires_admin main boolean true
+.cindex "restricting access to features"
.oindex "&%-bp%&"
The &%-bp%& command-line option, which lists the messages that are on the
queue, requires the caller to be an admin user unless
-&%queue_list_requires_admin%& is set false. See also &%prod_requires_admin%&.
+&%queue_list_requires_admin%& is set false.
+See also &%prod_requires_admin%& and &%commandline_checks_require_admin%&.
.option queue_only main boolean false
Currently it is only done for messages received using the EMSTP CHUNKING
option.
+The following variables will not have useful values:
+.code
+$max_received_linelength
+$body_linecount
+$body_zerocount
+.endd
+
Users of the local_scan() API (see &<<CHAPlocalscan>>&),
and any external programs which are passed a reference to a message data file
(except via the &"regex"&, &"malware"& or &"spam"&) ACL conditions)
is not required the &%tls_advertise_hosts%& option should be set empty.
-.option tls_certificate main string&!! unset
+.option tls_certificate main string list&!! unset
.cindex "TLS" "server certificate; location of"
.cindex "certificate" "server, location of"
-The value of this option is expanded, and must then be the absolute path to a
-file which contains the server's certificates. The server's private key is also
+.new
+The value of this option is expanded, and must then be a list of absolute paths to
+files which contains the server's certificates. Commonly only one file is
+needed.
+.wen
+The server's private key is also
assumed to be in this file if &%tls_privatekey%& is unset. See chapter
&<<CHAPTLS>>& for further details.
use when sending messages as a client, you must set the &%tls_certificate%&
option in the relevant &(smtp)& transport.
+.new
+&*Note*&: If you use filenames based on IP addresses, change the list
+separator in the usual way to avoid confusion under IPv6.
+
+&*Note*&: Under current versions of OpenSSL, when a list of more than one
+file is used, the &$tls_in_ourcert$& veriable is unreliable.
+
+&*Note*&: OCSP stapling is not usable when a list of more than one file is used.
+.wen
+
If the option contains &$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
Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
+.new
+For GnuTLS 3.5.6 or later the expanded value of this option can be a list
+of files, to match a list given for the &%tls_certificate%& option.
+The ordering of the two lists must match.
+.wen
+
.option tls_on_connect_ports main "string list" unset
.cindex SSMTP
-.option tls_privatekey main string&!! 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 the absolute path to a
-file which contains the server's private key. If this option is unset, or if
+.new
+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.
+.wen
+If this option is unset, or if
the expansion is forced to fail, or the result is an empty string, the private
key is assumed to be in the same file as the server's certificates. See chapter
&<<CHAPTLS>>& for further details.
lookup first. Only if that gives a definite &"no such host"& is the local
function called.
+&*Compatibility*&: From Exim 4.85 until fixed for 4.90, there was an
+inadvertent constraint that a transport name as an option had to be the last
+option specified.
+
If no IP address for a host can be found, what happens is controlled by the
.option forbid_blackhole redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, the &':blackhole:'& item may not appear in a
redirection list.
.option forbid_exim_filter redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is set true, only Sieve filters are permitted when
&%allow_filter%& is true.
.option forbid_file redirect boolean false
+.cindex "restricting access to features"
.cindex "delivery" "to file; forbidding"
+.cindex "filter" "locking out certain features"
.cindex "Sieve filter" "forbidding delivery to a file"
.cindex "Sieve filter" "&""keep""& facility; disabling"
If this option is true, this router may not generate a new address that
.option forbid_filter_dlfunc redirect boolean false
+.cindex "restricting access to features"
.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filters are not allowed to
make use of the &%dlfunc%& expansion facility to run dynamically loaded
functions.
.option forbid_filter_existstest redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
.cindex "expansion" "statting a file"
If this option is true, string expansions in Exim filters are not allowed to
make use of the &%exists%& condition or the &%stat%& expansion item.
.option forbid_filter_logwrite redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, use of the logging facility in Exim filters is not
permitted. Logging is in any case available only if the filter is being run
under some unprivileged uid (which is normally the case for ordinary users'
.option forbid_filter_lookup redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%lookup%& items.
.option forbid_filter_perl redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
This option has an effect only if Exim is built with embedded Perl support. If
it is true, string expansions in Exim filter files are not allowed to make use
of the embedded Perl support.
.option forbid_filter_readfile redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%readfile%& items.
.option forbid_filter_readsocket redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%readsocket%& items.
.option forbid_filter_reply redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, this router may not generate an automatic reply
message. Automatic replies can be generated only from Exim or Sieve filter
files, not from traditional forward files. This option is forced to be true if
.option forbid_filter_run redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, string expansions in Exim filter files are not allowed
to make use of &%run%& items.
.option forbid_include redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is true, items of the form
.code
:include:<path name>
.option forbid_pipe redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
.cindex "delivery" "to pipe; forbidding"
If this option is true, this router may not generate a new address which
specifies delivery to a pipe, either from an Exim filter or from a conventional
.option forbid_sieve_filter redirect boolean false
+.cindex "restricting access to features"
+.cindex "filter" "locking out certain features"
If this option is set true, only Exim filters are permitted when
&%allow_filter%& is true.
The value of the option is expanded, and must then be a numerical value
(decimal point allowed), optionally followed by one of the letters K, M, or G,
-for kilobytes, megabytes, or gigabytes. If Exim is running on a system with
+for kilobytes, megabytes, or gigabytes, optionally followed by a slash
+and further option modifiers. If Exim is running on a system with
large file support (Linux and FreeBSD have this), mailboxes larger than 2G can
be handled.
+The option modifier &%no_check%& can be used to force delivery even if the over
+quota condition is met. The quota gets updated as usual.
+
&*Note*&: A value of zero is interpreted as &"no quota"&.
The expansion happens while Exim is running as root, before it changes uid for
failure causes delivery to be deferred. A value of zero is interpreted as
&"no quota"&.
+The option modifier &%no_check%& can be used to force delivery even if the over
+quota condition is met. The quota gets updated as usual.
.option quota_is_inclusive appendfile boolean true
See &%quota%& above.
.option dkim_private_key smtp string&!! unset
.option dkim_canon smtp string&!! unset
.option dkim_strict smtp string&!! unset
-.option dkim_sign_headers smtp string&!! unset
+.option dkim_sign_headers smtp string&!! "per RFC"
+.option dkim_hash smtp string&!! sha256
+.option dkim_identity smtp string&!! unset
DKIM signing options. For details see section &<<SECDKIMSIGN>>&.
CHUNKING support, Exim will attempt to use BDAT commands rather than DATA.
BDAT will not be used in conjunction with a transport filter.
-.option hosts_try_fastopen smtp "host list!!" unset
+.option hosts_try_fastopen smtp "host list&!!" unset
.cindex "fast open, TCP" "enabling, in client"
.cindex "TCP Fast Open" "enabling, in client"
.cindex "RFC 7413" "TCP Fast Open"
On (at least some) current Linux distributions the facility must be enabled
in the kernel by the sysadmin before the support is usable.
+There is no option for control of the server side; if the system supports
+it it is always enebled. Note that legthy operations in the connect ACL,
+such as DNSBL lookups, will still delay the emission of the SMTP banner.
.option hosts_try_prdr smtp "host list&!!" *
.cindex "PRDR" "enabling, optional in client"
(If an API is found to let OpenSSL be configured in this way,
let the Exim Maintainers know and we'll likely use it).
.next
+.new
+With GnuTLS, if an explicit list is used for the &%tls_privatekey%& main option
+main option, it must be ordered to match the &%tls_certificate%& list.
+.wen
+.next
Some other recently added features may only be available in one or the other.
This should be documented with the feature. If the documentation does not
explicitly state that the feature is infeasible in the other TLS
{HIGH:!MD5:!SHA1}}
.endd
+.new
+This example will prefer ECDSA-authenticated ciphers over RSA ones:
+.code
+tls_require_ciphers = ECDSA:RSA:!COMPLEMENTOFDEFAULT
+.endd
+.wen
.section "Requiring specific ciphers or other parameters in GnuTLS" &&&
Further protection requires some further configuration at the server end.
-It is rumoured that all existing clients that support TLS/SSL use RSA
-encryption. To make this work you need to set, in the server,
+To make TLS work you need to set, in the server,
.code
tls_certificate = /some/file/name
tls_privatekey = /some/file/name
certificates that need to be sent to the client to enable it to authenticate
the server's certificate.
+.new
+For dual-stack (eg. RSA and ECDSA) configurations, these options can be
+colon-separated lists of file paths. Ciphers using given authentication
+algorithms require the presence of a suitable certificate to supply the
+public-key. The server selects among the certificates to present to the
+client depending on the selected cipher, hence the priority ordering for
+ciphers will affect which certificate is used.
+.wen
+
If you do not understand about certificates and keys, please try to find a
source of this background information, which is not Exim-specific. (There are a
few comments below in section &<<SECTcerandall>>&.)
"SECTmulmessam"
.cindex "multiple SMTP deliveries with TLS"
.cindex "TLS" "multiple message deliveries"
+.new
Exim sends multiple messages down the same TCP/IP connection by starting up
an entirely new delivery process for each message, passing the socket from
one process to the next. This implementation does not fit well with the use
of TLS, because there is quite a lot of state information associated with a TLS
connection, not just a socket identification. Passing all the state information
-to a new process is not feasible. Consequently, Exim shuts down an existing TLS
-session before passing the socket to a new process. The new process may then
+to a new process is not feasible. Consequently, for sending using TLS Exim
+starts an additional proxy process for handling the encryption, piping the
+unencrypted data stream from and to the delivery processes.
+
+An older mode of operation can be enabled on a per-host basis by the
+&%hosts_noproxy_tls%& option on the &(smtp)& transport. If the host matches
+this list the proxy process descibed above is not used; instead Exim
+.wen
+shuts down an existing TLS session being run by the delivery process
+before passing the socket to a new process. The new process may then
try to start a new TLS session, and if successful, may try to re-authenticate
if AUTH is in use, before sending the next message.
.vitem &*udpsend*&&~=&~<&'parameters'&>
+.cindex "UDP communications"
This modifier sends a UDP packet, for purposes such as statistics
collection or behaviour monitoring. The parameters are expanded, and
the result of the expansion must be a colon-separated list consisting
Note also that headers cannot be
modified by any of the post-data ACLs (DATA, MIME and DKIM).
Headers may be modified by routers (subject to the above) and transports.
+.new
+The Received-By: header is generated as soon as the body reception starts,
+rather than the traditional time after the full message is received;
+this will affect the timestamp.
+.wen
All the usual ACLs are called; if one results in the message being
rejected, all effort spent in delivery (including the costs on
item creates a signed address, and the &%prvscheck%& expansion item checks one.
The syntax of these expansion items is described in section
&<<SECTexpansionitems>>&.
+The validity period on signed addresses is seven days.
As an example, suppose the secret per-address keys are stored in an MySQL
database. A query to look up the key for an address could be defined as a macro
a commandline to send (may include a single %s which will be replaced with
the path to the mail file to be scanned),
an RE to trigger on from the returned data,
-an RE to extract malware_name from the returned data.
+and an RE to extract malware_name from the returned data.
For example:
.code
-av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)\$
+av_scanner = sock:127.0.0.1 6001:%s:(SPAM|VIRUS):(.*)$
.endd
-Default for the socket specifier is &_/tmp/malware.sock_&.
-Default for the commandline is &_%s\n_&.
-Both regular-expressions are required.
+.new
+Note that surrounding whitespace is stripped from each option, meaning
+there is no way to specify a trailing newline.
+The socket specifier and both regular-expressions are required.
+Default for the commandline is &_%s\n_& (note this does have a trailing newline);
+specify an empty element to get this.
+.wen
.vitem &%sophie%&
.cindex "virus scanners" "Sophos and Sophie"
.vlist
.vitem &*int&~body_linecount*&
This variable contains the number of lines in the message's body.
+.new
+It is not valid if the &%spool_files_wireformat%& option is used.
+.wen
.vitem &*int&~body_zerocount*&
This variable contains the number of binary zero bytes in the message's body.
+.new
+It is not valid if the &%spool_files_wireformat%& option is used.
+.wen
.vitem &*unsigned&~int&~debug_selector*&
This variable is set to zero when no debugging is taking place. Otherwise, it
&`SNI `& server name indication from TLS client hello
&`ST `& shadow transport name
&`T `& on &`<=`& lines: message subject (topic)
+&`TFO `& connection took advantage of TCP Fast Open
&` `& on &`=>`& &`**`& and &`==`& lines: transport name
&`U `& local user or RFC 1413 identity
&`X `& TLS cipher suite
&` incoming_interface `& local interface on <= and => lines
&` incoming_port `& remote port on <= lines
&`*lost_incoming_connection `& as it says (includes timeouts)
+&` millisec `& millisecond timestamps and QT,DT,D times
&` outgoing_interface `& local interface on => lines
&` outgoing_port `& add remote port to => lines
&`*queue_run `& start and end queue runs
.cindex "log" "delivery duration"
&%deliver_time%&: For each delivery, the amount of real time it has taken to
perform the actual delivery is logged as DT=<&'time'&>, for example, &`DT=1s`&.
+If millisecond logging is enabled, short times will be shown with greater
+precision, eg. &`DT=0.304`&.
.next
.cindex "log" "message size on delivery"
.cindex "size" "of message"
&%lost_incoming_connection%&: A log line is written when an incoming SMTP
connection is unexpectedly dropped.
.next
+.new
+.cindex "log" "millisecond timestamps"
+.cindex millisecond logging
+.cindex timstamps "millisecond, in logs"
+&%millisec%&: Timestamps have a period and three decimal places of finer granularity
+appended to the seconds value.
+.wen
+.next
.cindex "log" "outgoing interface"
.cindex "log" "local interface"
.cindex "log" "local address and port"
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.
+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
unprivileged), Exim must be built to allow group read access to its spool
files.
+.new
+By default, regular users are trusted to perform basic testing and
+introspection commands, as themselves. This setting can be tightened by
+setting the &%commandline_checks_require_admin%& option.
+This affects most of the checking options,
+such as &%-be%& and anything else &%-b*%&.
+.wen
.section "Spool files" "SECID275"
-J file and uses it to update the -H file before starting the next delivery
attempt.
+.new
+Files whose names end with -K or .eml may also be seen in the spool.
+These are temporaries used for DKIM or malware processing, when that is used.
+They should be tidied up by normal operations; any old ones are probably
+relics of crashes and can be removed.
+.wen
+
.section "Format of the -H file" "SECID282"
.cindex "uid (user id)" "in spool file"
.cindex "gid (group id)" "in spool file"
If a message was scanned by SpamAssassin, this is present. It records the value
of &$spam_score_int$&.
+.new
.vitem &%-spool_file_wireformat%&
The -D file for this message is in wire-format (for ESMTP CHUNKING)
rather than Unix-format.
The line-ending is CRLF rather than newline.
There is still, however, no leading-dot-stuffing.
+.wen
.vitem &%-tls_certificate_verified%&
A TLS certificate was received from the client that sent this message, and the
.ecindex IIDforspo2
.ecindex IIDforspo3
+.new
+.section "Format of the -D file" "SECID282a"
+The data file is traditionally in Unix-standard format: lines are ended with
+an ASCII newline character.
+However, when the &%spool_wireformat%& main option is used some -D files
+can have an alternate format.
+This is flagged by a &%-spool_file_wireformat%& line in the corresponding -H file.
+The -D file lines (not including the first name-component line) are
+suitable for direct copying to the wire when transmitting using the
+ESMTP CHUNKING option, meaning lower processing overhead.
+Lines are terminated with an ASCII CRLF pair.
+There is no dot-stuffing (and no dot-termination).
+.wen
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
.wen
If it is empty after expansion, DKIM signing is not done.
-.option dkim_selector smtp string&!! unset
+.option dkim_selector smtp string list&!! unset
This sets the key selector string.
-You can use the &%$dkim_domain%& expansion variable to look up a matching selector.
-The result is put in the expansion
+.new
+After expansion, which can use &$dkim_domain$&, this can be a list.
+Each element in turn is put in the expansion
variable &%$dkim_selector%& which may be used in the &%dkim_private_key%&
option along with &%$dkim_domain%&.
-If the option is empty after expansion, DKIM signing is not done.
+If the option is empty after expansion, DKIM signing is not done for this domain.
+.wen
.option dkim_private_key smtp string&!! unset
This sets the private key to use.
.endlist
If the option is empty after expansion, DKIM signing is not done.
+.new
+.option dkim_hash smtp string&!! sha256
+Can be set alternatively to &"sha1"& to use an alternate hash
+method. Note that sha1 is now condidered insecure, and deprecated.
+
+.option dkim_identity smtp string&!! unset
+If set after expansion, the value is used to set an "i=" tag in
+the signing header. The DKIM standards restrict the permissible
+syntax of this optional tag to a mail address, with possibly-empty
+local part, an @, and a domain identical to or subdomain of the "d="
+tag value. Note that Exim does not check the value.
+.wen
+
.option dkim_canon smtp string&!! unset
This option sets the canonicalization method used when signing a message.
The DKIM RFC currently supports two methods: "simple" and "relaxed".
unsigned. You can use the &%$dkim_domain%& and &%$dkim_selector%& expansion
variables here.
-.option dkim_sign_headers smtp string&!! unset
-If set, this option must expand to (or be specified as) a colon-separated
-list of header names. Headers with these names will be included in the message
-signature.
-When unspecified, the header names recommended in RFC4871 will be used.
+.option dkim_sign_headers smtp string&!! "see below"
+If set, this option must expand to a colon-separated
+list of header names.
+.new
+Headers with these names, or the absence or such a header, will be included
+in the message signature.
+When unspecified, the header names listed in RFC4871 will be used,
+whether or not each header is present in the message.
+The default list is available for the expansion in the macro
+"_DKIM_SIGN_HEADERS".
+
+If a name is repeated, multiple headers by that name (or the absence therof)
+will be signed. The textually later headers in the headers part of the
+message are signed first, if there are multiples.
+
+A name can be prefixed with either an '=' or a '+' character.
+If an '=' prefix is used, all headers that are present with this name
+will be signed.
+If a '+' prefix if used, all headers that are present with this name
+will be signed, and one signtature added for a missing header with the
+name will be appended.
+.wen
.section "Verifying DKIM signatures in incoming mail" "SECID514"
syntactically(!) correct signature in the incoming message.
A missing ACL definition defaults to accept.
If any ACL call does not accept, the message is not accepted.
-If a cutthrough delivery was in progress for the message it is
+If a cutthrough delivery was in progress for the message, that is
summarily dropped (having wasted the transmission effort).
To evaluate the signature in the ACL a large number of expansion variables
If a domain or identity is listed several times in the (expanded) value of
&%dkim_verify_signers%&, the ACL is only called once for that domain or identity.
+.new
+If multiple signatures match a domain (or identity), the ACL is called once
+for each matching signature.
+.wen
+
Inside the &%acl_smtp_dkim%&, the following expansion variables are
available (from most to least important):
&%dkim_verify_signers%& (see above).
.vitem &%$dkim_verify_status%&
-A string describing the general status of the signature. One of
+Within the DKIM ACL,
+a string describing the general status of the signature. One of
.ilist
&%none%&: There is no signature in the message for the current domain or
identity (as reflected by &%$dkim_cur_signer%&).
&%pass%&: The signature passed verification. It is valid.
.endlist
+.new
+This variable can be overwritten using an ACL 'set' modifier.
+This might, for instance, be done to enforce a policy restriction on
+hash-method or key-size:
+.code
+ warn condition = ${if eq {$dkim_algo}{rsa-sha1}}
+ condition = ${if eq {$dkim_verify_status}{pass}}
+ logwrite = NOTE: forcing dkim verify fail (was pass)
+ set dkim_verify_status = fail
+ set dkim_verify_reason = hash too weak
+.endd
+
+After all the DKIM ACL runs have completed, the value becomes a
+colon-separated list of the values after each run.
+.wen
+
.vitem &%$dkim_verify_reason%&
A string giving a little bit more detail when &%$dkim_verify_status%& is either
"fail" or "invalid". One of
DKIM verification. It may of course also mean that the signature is forged.
.endlist
+.new
+This variable can be overwritten using an ACL 'set' modifier.
+.wen
+
.vitem &%$dkim_domain%&
The signing domain. IMPORTANT: This variable is only populated if there is
an actual signature in the message for the current domain or identity (as
.vitem &%$dkim_canon_body%&
The body canonicalization method. One of 'relaxed' or 'simple'.
-.vitem &%dkim_canon_headers%&
+.vitem &%$dkim_canon_headers%&
The header canonicalization method. One of 'relaxed' or 'simple'.
.vitem &%$dkim_copiedheaders%&
git://git.exim.org / users / jgh / exim.git / blobdiff