.cindex headers "authentication-results:"
.cindex authentication "expansion item"
This item returns a string suitable for insertion as an
-&'Authentication-Results"'&
+&'Authentication-Results:'&
header line.
The given <&'authserv-id'&> is included in the result; typically this
will be a domain name identifying the system performing the authentications.
${filter{a:b:c}{!eq{$item}{b}}}
.endd
yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored
-to what it was before. See also the &*map*& and &*reduce*& expansion items.
+to what it was before. See also the &%map%& and &%reduce%& expansion items.
.vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
${map{a:b:c}{[$item]}} ${map{<- x-y-z}{($item)}}
.endd
expands to &`[a]:[b]:[c] (x)-(y)-(z)`&. At the end of the expansion, the
-value of &$item$& is restored to what it was before. See also the &*filter*&
-and &*reduce*& expansion items.
+value of &$item$& is restored to what it was before. See also the &%filter%&
+and &%reduce%& expansion items.
.vitem &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*&
.cindex "expansion" "numeric hash"
list is assigned to &$item$&, in turn, and <&'string3'&> is expanded for each of
them. The result of that expansion is assigned to &$value$& before the next
iteration. When the end of the list is reached, the final value of &$value$& is
-added to the expansion output. The &*reduce*& expansion item can be used in a
+added to the expansion output. The &%reduce%& expansion item can be used in a
number of ways. For example, to add up a list of numbers:
.code
${reduce {<, 1,2,3}{0}{${eval:$value+$item}}}
${reduce {3:0:9:4:6}{0}{${if >{$item}{$value}{$item}{$value}}}}
.endd
At the end of a &*reduce*& expansion, the values of &$item$& and &$value$& are
-restored to what they were before. See also the &*filter*& and &*map*&
+restored to what they were before. See also the &%filter%& and &%map%&
expansion items.
.vitem &*$rheader_*&<&'header&~name'&>&*:*&&~or&~&*$rh_*&<&'header&~name'&>&*:*&
${addresses:>:$h_from:}
.endd
-Compare the &*address*& (singular)
+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
+address. See the &%filter%&, &%map%&, and &%reduce%& items for ways of
processing lists.
To clarify "list of addresses in RFC 2822 format" mentioned above, Exim follows
.code
${if forany{<, $recipients}{match{$item}{^user3@}}{yes}{no}}
.endd
-The value of &$item$& is saved and restored while &*forany*& or &*forall*& is
+The value of &$item$& is saved and restored while &%forany%& or &%forall%& is
being processed, to enable these expansion items to be nested.
To scan a named list, expand it with the &*listnamed*& operator.
.vindex "&$config_file$&"
The name of the main configuration file Exim is using.
+.new
+.vitem &$dmarc_domain_policy$& &&&
+ &$dmarc_status$& &&&
+ &$dmarc_status_text$& &&&
+ &$dmarc_used_domains$&
+Results of DMARC verification.
+For details see section &<<SECDMARC>>&.
+.wen
+
.vitem &$dkim_verify_status$&
Results of DKIM verification.
For details see section &<<SECDKIMVFY>>&.
.cindex authentication "expansion item"
Performing these checks sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
.vitem &$host_lookup_failed$&
.cindex "UTF-8" "in domain name"
Lots of discussion is going on about internationalized domain names. One
camp is strongly in favour of just using UTF-8 characters, and it seems
-that at least two other MTAs permit this. This option allows Exim users to
-experiment if they wish.
+that at least two other MTAs permit this.
+This option allows Exim users to experiment if they wish.
If it is set true, Exim's domain parsing function allows valid
UTF-8 multicharacters to appear in domain name components, in addition to
-letters, digits, and hyphens. However, just setting this option is not
-enough; if you want to look up these domain names in the DNS, you must also
+letters, digits, and hyphens.
+
+.new
+If Exim is built with internationalization support
+and the SMTPUTF8 ESMTP option is in use (see chapter &<<CHAPi18n>>&)
+this option can be left as default.
+.wen
+Without that,
+if you want to look up such domain names in the DNS, you must also
adjust the value of &%dns_check_names_pattern%& to match the extended form. A
suitable setting is:
.code
Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later).
-For GnuTLS 3.5.6 or later the expanded value of this option can be a list
+.new
+For OpenSSL 1.1.0 or later, and
+.wen
+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.
-The file(s) should be in DER format
+.new
+The file(s) should be in DER format,
+except for GnuTLS 3.6.3 or later when an optional filetype prefix
+can be used. The prefix must be one of "DER" or "PEM", followed by
+a single space. If one is used it sets the format for subsequent
+files in the list; the initial format is DER.
+When a PEM format file is used it may contain multiple proofs,
+for multiple certificate chain element proofs under TLS1.3.
+.wen
.option tls_on_connect_ports main "string list" unset
.cindex SSMTP
.cindex authentication "expansion item"
Successful authentication sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
-.chapter "DKIM and SPF" "CHAPdkim" &&&
- "DKIM and SPF Support"
-.cindex "DKIM"
+.chapter "DKIM, SPF and DMARC" "CHAPdkim" &&&
+ "DKIM, SPF and DMARC Support"
.section "DKIM (DomainKeys Identified Mail)" SECDKIM
+.cindex "DKIM"
DKIM is a mechanism by which messages sent by some entity can be provably
linked to a domain which that entity controls. It permits reputation to
.cindex authentication "expansion item"
Performing verification sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
.new
For most purposes the default option settings suffice and the remainder
For verification, an ACL condition and an expansion lookup are provided.
.cindex authentication "expansion item"
Performing verification sets up information used by the
-&$authresults$& expansion item.
+&%authresults%& expansion item.
.cindex SPF "ACL condition"
+
+.new
+.section DMARC SECDMARC
+.cindex DMARC verification
+
+DMARC combines feedback from SPF, DKIM, and header From: in order
+to attempt to provide better indicators of the authenticity of an
+email. This document does not explain the fundamentals; you
+should read and understand how it works by visiting the website at
+&url(http://www.dmarc.org/).
+
+If Exim is built with DMARC support,
+the libopendmarc library is used.
+
+For building Exim yourself, obtain the library from
+&url(http://sourceforge.net/projects/opendmarc/)
+to obtain a copy, or find it in your favorite rpm package
+repository. You will need to attend to the local/Makefile feature
+SUPPORT_DMARC and the associated LDFLAGS addition.
+This description assumes
+that headers will be in /usr/local/include, and that the libraries
+are in /usr/local/lib.
+
+. subsection
+
+There are three main-configuration options:
+.cindex DMARC "configuration options"
+
+The &%dmarc_tld_file%& option
+.oindex &%dmarc_tld_file%&
+defines the location of a text file of valid
+top level domains the opendmarc library uses
+during domain parsing. Maintained by Mozilla,
+the most current version can be downloaded
+from a link at &url(https://publicsuffix.org/list/, currently pointing
+at https://publicsuffix.org/list/public_suffix_list.dat)
+See also util/renew-opendmarc-tlds.sh script.
+The default for the option is /etc/exim/opendmarc.tlds.
+
+
+The &%dmarc_history_file%& option, if set
+.oindex &%dmarc_history_file%&
+defines the location of a file to log results
+of dmarc verification on inbound emails. The
+contents are importable by the opendmarc tools
+which will manage the data, send out DMARC
+reports, and expire the data. Make sure the
+directory of this file is writable by the user
+exim runs as.
+The default is unset.
+
+The &%dmarc_forensic_sender%& option
+.oindex &%dmarc_forensic_sender%&
+defines an alternate email address to use when sending a
+forensic report detailing alignment failures
+if a sender domain's dmarc record specifies it
+and you have configured Exim to send them.
+If set, this is expanded and used for the
+From: header line; the address is extracted
+from it and used for the envelope from.
+If not set (the default), the From: header is expanded from
+the dsn_from option, and <> is used for the
+envelope from.
+
+. I wish we had subsections...
+
+.cindex DMARC controls
+By default, the DMARC processing will run for any remote,
+non-authenticated user. It makes sense to only verify DMARC
+status of messages coming from remote, untrusted sources. You can
+use standard conditions such as hosts, senders, etc, to decide that
+DMARC verification should *not* be performed for them and disable
+DMARC with a control setting:
+.code
+ control = dmarc_disable_verify
+.endd
+A DMARC record can also specify a "forensic address", which gives
+exim an email address to submit reports about failed alignment.
+Exim does not do this by default because in certain conditions it
+results in unintended information leakage (what lists a user might
+be subscribed to, etc). You must configure exim to submit forensic
+reports to the owner of the domain. If the DMARC record contains a
+forensic address and you specify the control statement below, then
+exim will send these forensic emails. It's also advised that you
+configure a dmarc_forensic_sender because the default sender address
+construction might be inadequate.
+.code
+ control = dmarc_enable_forensic
+.endd
+(AGAIN: You can choose not to send these forensic reports by simply
+not putting the dmarc_enable_forensic control line at any point in
+your exim config. If you don't tell it to send them, it will not
+send them.)
+
+There are no options to either control. Both must appear before
+the DATA acl.
+
+. subsection
+
+DMARC checks cam be run on incoming SMTP messages by using the
+"dmarc_status" ACL condition in the DATA ACL. You are required to
+call the "spf" condition first in the ACLs, then the "dmarc_status"
+condition. Putting this condition in the ACLs is required in order
+for a DMARC check to actually occur. All of the variables are set
+up before the DATA ACL, but there is no actual DMARC check that
+occurs until a "dmarc_status" condition is encountered in the ACLs.
+
+The dmarc_status condition takes a list of strings on its
+right-hand side. These strings describe recommended action based
+on the DMARC check. To understand what the policy recommendations
+mean, refer to the DMARC website above. Valid strings are:
+.display
+&'accept '& The DMARC check passed and the library recommends accepting the email.
+&'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.
+&'nofrom '& Unable to determine the domain of the sender.
+&'temperror '& Library error or dns error.
+&'off '& The DMARC check was disabled for this email.
+.endd
+You can prefix each string with an exclamation mark to invert its
+meaning, for example "!accept" will match all results but
+"accept". The string list is evaluated left-to-right in a
+short-circuit fashion. When a string matches the outcome of the
+DMARC check, the condition succeeds. If none of the listed
+strings matches the outcome of the DMARC check, the condition
+fails.
+
+Of course, you can also use any other lookup method that Exim
+supports, including LDAP, Postgres, MySQL, etc, as long as the
+result is a list of colon-separated strings.
+
+Performing the check sets up information used by the
+&%authresults%& expansion item.
+
+Several expansion variables are set before the DATA ACL is
+processed, and you can use them in this ACL. The following
+expansion variables are available:
+
+&$dmarc_status$&
+.vindex &$dmarc_status$&
+.cindex DMARC result
+is a one word status indicating what the DMARC library
+thinks of the email. It is a combination of the results of
+DMARC record lookup and the SPF/DKIM/DMARC processing results
+(if a DMARC record was found). The actual policy declared
+in the DMARC record is in a separate expansion variable.
+
+&$dmarc_status_text$&
+.vindex &$dmarc_status_text$&
+is a slightly longer, human readable status.
+
+&$dmarc_used_domain$&
+.vindex &$dmarc_used_domain$&
+is the domain which DMARC used to look up the DMARC policy record.
+
+&$dmarc_domain_policy$&
+.vindex &$dmarc_domain_policy$&
+is the policy declared in the DMARC record. Valid values
+are "none", "reject" and "quarantine". It is blank when there
+is any error, including no DMARC record.
+
+. subsection
+
+By default, Exim's DMARC configuration is intended to be
+non-intrusive and conservative. To facilitate this, Exim will not
+create any type of logging files without explicit configuration by
+you, the admin. Nor will Exim send out any emails/reports about
+DMARC issues without explicit configuration by you, the admin (other
+than typical bounce messages that may come about due to ACL
+processing or failure delivery issues).
+
+In order to log statistics suitable to be imported by the opendmarc
+tools, you need to:
+.ilist
+Configure the global setting dmarc_history_file
+.next
+Configure cron jobs to call the appropriate opendmarc history
+import scripts and truncating the dmarc_history_file
+.endlist
+
+In order to send forensic reports, you need to:
+.ilist
+Configure the global setting dmarc_forensic_sender
+.next
+Configure, somewhere before the DATA ACL, the control option to
+enable sending DMARC forensic reports
+.endlist
+
+. subsection
+
+Example usage:
+.code
+(RCPT ACL)
+ warn domains = +local_domains
+ hosts = +local_hosts
+ control = dmarc_disable_verify
+
+ warn !domains = +screwed_up_dmarc_records
+ control = dmarc_enable_forensic
+
+ warn condition = (lookup if destined to mailing list)
+ set acl_m_mailing_list = 1
+
+(DATA ACL)
+ warn dmarc_status = accept : none : off
+ !authenticated = *
+ log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain
+
+ warn dmarc_status = !accept
+ !authenticated = *
+ log_message = DMARC DEBUG: '$dmarc_status' for $dmarc_used_domain
+
+ warn dmarc_status = quarantine
+ !authenticated = *
+ set $acl_m_quarantine = 1
+ # Do something in a transport with this flag variable
+
+ deny condition = ${if eq{$dmarc_domain_policy}{reject}}
+ condition = ${if eq{$acl_m_mailing_list}{1}}
+ message = Messages from $dmarc_used_domain break mailing lists
+
+ deny dmarc_status = reject
+ !authenticated = *
+ message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT
+
+ warn add_header = :at_start:${authresults {$primary_hostname}}
+.endd
+
+.wen
+
+
+
+
. ////////////////////////////////////////////////////////////////////////////
. ////////////////////////////////////////////////////////////////////////////
git://git.exim.org / users / heiko / exim.git / blobdiff