X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/fa7b17bdbc8c055c475a50791627cd75d257f4f3..2b2cfa838f206b5d97a120722861f42780bc6a6a:/doc/doc-docbook/spec.xfpt diff --git a/doc/doc-docbook/spec.xfpt b/doc/doc-docbook/spec.xfpt index a073730c6..bca6689b6 100644 --- a/doc/doc-docbook/spec.xfpt +++ b/doc/doc-docbook/spec.xfpt @@ -52,7 +52,7 @@ .set I "    " .macro copyyear -2018 +2018, 2019 .endmacro . ///////////////////////////////////////////////////////////////////////////// @@ -1886,11 +1886,10 @@ to your &_Local/Makefile_& and rebuild Exim. .section "Including TLS/SSL encryption support" "SECTinctlsssl" .cindex "TLS" "including support for TLS" .cindex "encryption" "including support for" -.cindex "SUPPORT_TLS" .cindex "OpenSSL" "building Exim with" .cindex "GnuTLS" "building Exim with" -Exim can be built to support encrypted SMTP connections, using the STARTTLS -command as per RFC 2487. It can also support legacy clients that expect to +Exim is usually built to support encrypted SMTP connections, using the STARTTLS +command as per RFC 2487. It can also support clients that expect to start a TLS session immediately on connection to a non-standard port (see the &%tls_on_connect_ports%& runtime option and the &%-tls-on-connect%& command line option). @@ -1899,35 +1898,41 @@ If you want to build Exim with TLS support, you must first install either the OpenSSL or GnuTLS library. There is no cryptographic code in Exim itself for implementing SSL. +.new +If you do not want TLS support you should set +.code +DISABLE_TLS=yes +.endd +in &_Local/Makefile_&. +.wen + If OpenSSL is installed, you should set .code -SUPPORT_TLS=yes +USE_OPENSL=yes TLS_LIBS=-lssl -lcrypto .endd in &_Local/Makefile_&. You may also need to specify the locations of the OpenSSL library and include files. For example: .code -SUPPORT_TLS=yes +USE_OPENSL=yes TLS_LIBS=-L/usr/local/openssl/lib -lssl -lcrypto TLS_INCLUDE=-I/usr/local/openssl/include/ .endd .cindex "pkg-config" "OpenSSL" If you have &'pkg-config'& available, then instead you can just use: .code -SUPPORT_TLS=yes +USE_OPENSL=yes USE_OPENSSL_PC=openssl .endd .cindex "USE_GNUTLS" If GnuTLS is installed, you should set .code -SUPPORT_TLS=yes USE_GNUTLS=yes TLS_LIBS=-lgnutls -ltasn1 -lgcrypt .endd in &_Local/Makefile_&, and again you may need to specify the locations of the library and include files. For example: .code -SUPPORT_TLS=yes USE_GNUTLS=yes TLS_LIBS=-L/usr/gnu/lib -lgnutls -ltasn1 -lgcrypt TLS_INCLUDE=-I/usr/gnu/include @@ -1935,7 +1940,6 @@ TLS_INCLUDE=-I/usr/gnu/include .cindex "pkg-config" "GnuTLS" If you have &'pkg-config'& available, then instead you can just use: .code -SUPPORT_TLS=yes USE_GNUTLS=yes USE_GNUTLS_PC=gnutls .endd @@ -2528,6 +2532,8 @@ use of Exim's filtering capabilities, you should make the document entitled If you are already running Exim on your host, building and installing a new version automatically makes it available to MUAs, or any other programs that call the MTA directly. However, if you are running an Exim daemon, you do need +.cindex restart "on HUP signal" +.cindex signal "HUP, to restart" to send it a HUP signal, to make it re-execute itself, and thereby pick up the new binary. You do not need to stop processing mail in order to install a new version of Exim. The install script does not modify an existing runtime @@ -2766,9 +2772,12 @@ used to specify a path on the command line if a pid file is required. The SIGHUP signal .cindex "SIGHUP" +.cindex restart "on HUP signal" +.cindex signal "HUP, to restart" .cindex "daemon" "restarting" .cindex signal "to reload configuration" .cindex daemon "reload configuration" +.cindex reload configuration can be used to cause the daemon to re-execute itself. This should be done whenever Exim's configuration file, or any file that is incorporated into it by means of the &%.include%& facility, is changed, and also whenever a new version @@ -3954,6 +3963,20 @@ is sent to the sender, containing the text &"cancelled by administrator"&. Bounce messages are just discarded. This option can be used only by an admin user. +.new +.vitem &%-MG%&&~<&'queue&~name'&&~<&'message&~id'&>&~<&'message&~id'&>&~... +.oindex "&%-MG%&" +.cindex queue named +.cindex "named queues" +.cindex "queue" "moving messages" +This option requests that each listed message be moved from its current +queue to the given named queue. +The destination queue name argument is required, but can be an empty +string to define the default queue. +If the messages are not currently located in the default queue, +a &%-qG%& option will be required to define the source queue. +.wen + .vitem &%-Mmad%&&~<&'message&~id'&>&~<&'message&~id'&>&~... .oindex "&%-Mmad%&" .cindex "delivery" "cancelling all" @@ -6254,10 +6277,6 @@ Two remote transports and four local transports are defined. remote_smtp: driver = smtp message_size_limit = ${if > {$max_received_linelength}{998} {1}{0}} -.ifdef _HAVE_DANE - dnssec_request_domains = * - hosts_try_dane = * -.endif .ifdef _HAVE_PRDR hosts_try_prdr = * .endif @@ -6266,7 +6285,7 @@ This transport is used for delivering messages over SMTP connections. The list of remote hosts comes from the router. The &%message_size_limit%& usage is a hack to avoid sending on messages with over-long lines. The built-in macro _HAVE_DANE guards configuration -to try to use DNSSEC for all queries and to use DANE for delivery; +to use DANE for delivery; see section &<>& for more details. The &%hosts_try_prdr%& option enables an efficiency SMTP option. It is @@ -6658,11 +6677,10 @@ aliases or other indexed data referenced by an MTA. Information about cdb and tools for building the files can be found in several places: .display &url(https://cr.yp.to/cdb.html) -&url(http://www.corpit.ru/mjt/tinycdb.html) +&url(https://www.corpit.ru/mjt/tinycdb.html) &url(https://packages.debian.org/stable/utils/freecdb) &url(https://github.com/philpennock/cdbtools) (in Go) .endd -. --- 2018-09-07: corpit.ru http:-only A cdb distribution is not needed in order to build Exim with cdb support, because the code for reading cdb files is included directly in Exim itself. However, no means of building or testing cdb files is provided with Exim, so @@ -7324,7 +7342,7 @@ with the lookup. With &"strict"& a response from the DNS resolver that is not labelled as authenticated data is treated as equivalent to a temporary DNS error. -The default is &"never"&. +The default is &"lax"&. See also the &$lookup_dnssec_authenticated$& variable. @@ -9214,7 +9232,13 @@ dependent upon the option for which a value is sought; in this documentation, options for which string expansion is performed are marked with † after the data type. ACL rules always expand strings. A couple of expansion conditions do not expand some of the brace-delimited branches, for security -reasons. +reasons, +.new +.cindex "tainted data" expansion +.cindex expansion "tainted data" +and expansion of data deriving from the sender (&"tainted data"&) +is not permitted. +.wen @@ -9364,7 +9388,7 @@ If the ACL returns defer the result is a forced-fail. Otherwise the expansion f .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. @@ -9648,7 +9672,7 @@ input, but a separator setting is not included in the output. For example: ${filter{a:b:c}{!eq{$item}{b}}} .endd yields &`a:c`&. At the end of the expansion, the value of &$item$& is restored -to what it was before. See also the &*map*& and &*reduce*& expansion items. +to what it was before. See also the &%map%& and &%reduce%& expansion items. .vitem &*${hash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& @@ -9999,8 +10023,8 @@ setting is not included in the output. For example: ${map{a:b:c}{[$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 &*${nhash{*&<&'string1'&>&*}{*&<&'string2'&>&*}{*&<&'string3'&>&*}}*& .cindex "expansion" "numeric hash" @@ -10199,7 +10223,7 @@ assigned to the &$value$& variable. After this, each item in the <&'string1'&> list is assigned to &$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}}} @@ -10210,7 +10234,7 @@ can be found: ${reduce {3:0:9:4:6}{0}{${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'&>&*:*& @@ -10470,9 +10494,9 @@ separator explicitly: ${addresses:>:$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 @@ -11365,7 +11389,7 @@ list separator is changed to a comma: .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. @@ -12066,6 +12090,15 @@ contain the trailing slash. If &$config_file$& does not contain a slash, .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 &<>&. +.wen + .vitem &$dkim_verify_status$& Results of DKIM verification. For details see section &<>&. @@ -12293,7 +12326,7 @@ the result, the name is not accepted, and &$host_lookup_deferred$& is set to .cindex authentication "expansion item" Performing these checks sets up information used by the -&$authresults$& expansion item. +&%authresults%& expansion item. .vitem &$host_lookup_failed$& @@ -13331,6 +13364,9 @@ or a &%def%& condition. &*Note*&: Under versions of OpenSSL preceding 1.1.1, when a list of more than one file is used for &%tls_certificate%&, this variable is not reliable. +.new +The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions. +.wen .vitem &$tls_in_peercert$& .vindex "&$tls_in_peercert$&" @@ -14336,7 +14372,9 @@ listed in more than one group. See also the &'Policy controls'& section above. .table2 -.row &%dkim_verify_signers%& "DKIM domain for which DKIM ACL is run" +.row &%dkim_verify_hashes%& "DKIM hash methods accepted for signatures" +.row &%dkim_verify_keytypes%& "DKIM key types accepted for signatures" +.row &%dkim_verify_signers%& "DKIM domains for which DKIM ACL is run" .row &%host_lookup%& "host name looked up for these hosts" .row &%host_lookup_order%& "order of DNS and local name lookups" .row &%recipient_unqualified_hosts%& "may send unqualified recipients" @@ -14667,13 +14705,20 @@ recommended, except when you have no other choice. .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 &<>&) +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 @@ -15081,6 +15126,27 @@ etc. are ignored. If IP literals are enabled, the &(ipliteral)& router declines to handle IPv6 literal addresses. +.new +.option dkim_verify_hashes main "string list" "sha256 : sha512 : sha1" +.cindex DKIM "selecting signature algorithms" +This option gives a list of hash types which are acceptable in signatures, +and an order of processing. +Signatures with algorithms not in the list will be ignored. + +Note that the presence of sha1 violates RFC 8301. +Signatures using the rsa-sha1 are however (as of writing) still common. +The default inclusion of sha1 may be dropped in a future release. + +.option dkim_verify_keytypes main "string list" "ed25519 : rsa" +This option gives a list of key types which are acceptable in signatures, +and an order of processing. +Signatures with algorithms not in the list will be ignored. + +.option dkim_verify_minimal main boolean false +If set to true, verification of signatures will terminate after the +first success. +.wen + .option dkim_verify_signers main "domain list&!!" $dkim_signers .cindex DKIM "controlling calls to the ACL" This option gives a list of DKIM domains for which the DKIM ACL is run. @@ -16007,6 +16073,10 @@ when Exim is entered, so it can, for example, contain a reference to the host name. If no specific path is set for the log files at compile or runtime, or if the option is unset at runtime (i.e. &`log_file_path = `&) they are written in a sub-directory called &_log_& in Exim's spool directory. +.new +A path must start with a slash. +To send to syslog, use the word &"syslog"&. +.wen Chapter &<>& contains further details about Exim's logging, and section &<>& describes how the contents of &%log_file_path%& are used. If this string is fixed at your installation (contains no expansion @@ -16403,6 +16473,8 @@ and from which pipeline early-connection (before MAIL) SMTP commands are acceptable. When used, the pipelining saves on roundtrip times. +See also the &%hosts_pipe_connect%& smtp transport option. + Currently the option name &"X_PIPE_CONNECT"& is used. .wen @@ -16864,11 +16936,11 @@ it qualifies them only if the message came from a host that matches &%sender_unqualified_hosts%&, or if the message was submitted locally (not using TCP/IP), and the &%-bnq%& option was not set. -.option set_environment main "string list" empty +.option add_environment main "string list" empty .cindex "environment" -This option allows to set individual environment variables that the +This option allows to add individual environment variables that the currently linked libraries and programs in child processes use. The -default list is empty, +default list is empty. .option slow_lookup_log main integer 0 @@ -17610,8 +17682,8 @@ is not required the &%tls_advertise_hosts%& option should be set empty. .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 -files which contains the server's certificates. Commonly only one file is -needed. +files which contain the server's certificates (in PEM format). +Commonly only one file is needed. The server's private key is also assumed to be in this file if &%tls_privatekey%& is unset. See chapter &<>& for further details. @@ -17627,9 +17699,9 @@ separator in the usual way (&<>&) to avoid confusion under IP &*Note*&: Under versions of OpenSSL preceding 1.1.1, when a list of more than one file is used, the &$tls_in_ourcert$& variable is unreliable. - -&*Note*&: OCSP stapling is not usable under OpenSSL -when a list of more than one file is used. +.new +The macro "_TLS_BAD_MULTICERT_IN_OURCERT" will be defined for those versions. +.wen If the option contains &$tls_out_sni$& and Exim is built against OpenSSL, then if the OpenSSL build supports TLS extensions and the TLS client sends the @@ -17680,7 +17752,14 @@ larger prime than requested. The value of this option is expanded and indicates the source of DH parameters to be used by Exim. -&*Note: The Exim Maintainers strongly recommend using a filename with site-generated +.new +This option is ignored for GnuTLS version 3.6.0 and later. +The library manages parameter negotiation internally. +.wen + +&*Note: The Exim Maintainers strongly recommend, +for other TLS library versions, +using a filename with site-generated local DH parameters*&, which has been supported across all versions of Exim. The other specific constants available are a fallback so that even when "unconfigured", Exim can offer Perfect Forward Secrecy in older ciphersuites in TLS. @@ -17775,11 +17854,37 @@ status proof for the server's certificate, as obtained from the Certificate Authority. Usable for GnuTLS 3.4.4 or 3.3.17 or OpenSSL 1.1.0 (or later). +.new +The macro "_HAVE_TLS_OCSP" will be defined for those versions. +.wen -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. +.new +The macro "_HAVE_TLS_OCSP_LIST" will be defined for those versions. +.wen +.new +The file(s) should be in DER format, +except for GnuTLS 3.6.3 or later +or for OpenSSL, +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. +If multiple proofs are wanted, for multiple chain elements +(this only works under TLS1.3) +they must be coded as a combined OCSP response. + +Although GnuTLS will accept PEM files with multiple separate +PEM blobs (ie. separate OCSP responses), it sends them in the +TLS Certificate record interleaved with the certificates of the chain; +although a GnuTLS client is happy with that, an OpenSSL client is not. +.wen .option tls_on_connect_ports main "string list" unset .cindex SSMTP @@ -18297,7 +18402,7 @@ or for any deliveries caused by this router. You should not set this option unless you really, really know what you are doing. See also the generic transport option of the same name. -.option dnssec_request_domains routers "domain list&!!" unset +.option dnssec_request_domains routers "domain list&!!" * .cindex "MX record" "security" .cindex "DNSSEC" "MX lookup" .cindex "security" "MX lookup" @@ -18873,11 +18978,24 @@ latter kind. This option controls whether the local part is used to form the key for retry hints for addresses that suffer temporary errors while being handled by this -router. The default value is true for any router that has &%check_local_user%& +.new +router. The default value is true for any router that has any of +&%check_local_user%&, +&%local_parts%&, +&%condition%&, +&%local_part_prefix%&, +&%local_part_suffix%&, +&%senders%& or +&%require_files%& +.wen set, and false otherwise. Note that this option does not apply to hints keys for transport delays; they are controlled by a generic transport option of the same name. +Failing to set this option when it is needed +(because a remote router handles only some of the local-parts for a domain) +can result in incorrect error messages being generated. + The setting of &%retry_use_local_part%& applies only to the router on which it appears. If the router generates child addresses, they are routed independently; this setting does not become attached to them. @@ -19007,14 +19125,19 @@ matters. .new -.option set routers string unset +.option set routers "string list" unset .cindex router variables -This option may be used multiple times on a router. -Each string given must be of the form $"name = value"$ +This option may be used multiple times on a router; +because of this the list aspect is mostly irrelevant. +The list separator is a semicolon but can be changed in the +usual way. + +Each list-element given must be of the form $"name = value"$ and the names used must start with the string &"r_"&. -Strings are accumulated for each router which is run. +Values containing a list-separator should have them doubled. When a router runs, the strings are evaluated in order, -to create variables. +to create variables which are added to the set associated with +the address. The variable is set with the expansion of the value. The variables can be used by the router options (not including any preconditions) @@ -22807,6 +22930,15 @@ sometimes add other information onto the ends of message filenames. Section &<>& contains further information. +.new +This option should not be used when other message-handling software +may duplicate messages by making hardlinks to the files. When that is done Exim +will count the message size once for each filename, in contrast with the actual +disk usage. When the option is not set, calculating total usage requires +a system-call per file to get the size; the number of links is then available also +as is used to adjust the effective size. +.wen + .option quota_warn_message appendfile string&!! "see below" See below for the use of this option. If it is not set when @@ -24401,15 +24533,23 @@ 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 &<>&. .option dkim_domain smtp string list&!! unset +DKIM signing option. For details see section &<>&. .option dkim_hash smtp string&!! sha256 +DKIM signing option. For details see section &<>&. .option dkim_identity smtp string&!! unset +DKIM signing option. For details see section &<>&. .option dkim_private_key smtp string&!! unset +DKIM signing option. For details see section &<>&. .option dkim_selector smtp string&!! unset +DKIM signing option. For details see section &<>&. .option dkim_strict smtp string&!! unset +DKIM signing option. For details see section &<>&. .option dkim_sign_headers smtp string&!! "per RFC" +DKIM signing option. For details see section &<>&. .option dkim_timestamps smtp string&!! unset -DKIM signing options. For details see section &<>&. +DKIM signing option. For details see section &<>&. .option delay_after_cutoff smtp boolean true @@ -24451,14 +24591,15 @@ See the &%search_parents%& option in chapter &<>& for more details. -.option dnssec_request_domains smtp "domain list&!!" unset +.option dnssec_request_domains smtp "domain list&!!" * .cindex "MX record" "security" .cindex "DNSSEC" "MX lookup" .cindex "security" "MX lookup" .cindex "DNS" "DNSSEC" DNS lookups for domains matching &%dnssec_request_domains%& will be done with -the dnssec request bit set. -This applies to all of the SRV, MX, AAAA, A lookup sequence. +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. @@ -24468,9 +24609,9 @@ This applies to all of the SRV, MX, AAAA, A lookup sequence. .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 -(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. +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. @@ -24629,6 +24770,8 @@ When used, the pipelining saves on roundtrip times. It also turns SMTP into a client-first protocol so combines well with TCP Fast Open. +See also the &%pipelining_connect_advertise_hosts%& main option. + Note: When the facility is used, the transport &%helo_data%& option will be expanded before the &$sending_ip_address$& variable @@ -24749,7 +24892,8 @@ TLS session for any host that matches this list. .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. +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. See section &<>&. @@ -24785,11 +24929,11 @@ 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 lookup a -TLSA record for any host matching the list. -If found and verified by DNSSEC, -a DANE-verified TLS connection is made to that host; -there will be no fallback to in-clear communication. +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. See section &<>&. .option hosts_try_fastopen smtp "host list&!!" * @@ -26628,7 +26772,7 @@ no successful authentication. .cindex authentication "expansion item" Successful authentication sets up information used by the -&$authresults$& expansion item. +&%authresults%& expansion item. @@ -27911,11 +28055,8 @@ to use GnuTLS, you need to set .code USE_GNUTLS=yes .endd -in Local/Makefile, in addition to -.code -SUPPORT_TLS=yes -.endd -You must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the +in Local/Makefile +you must also set TLS_LIBS and TLS_INCLUDE appropriately, so that the include files and libraries for GnuTLS can be found. There are some differences in usage when using GnuTLS instead of OpenSSL: @@ -28472,6 +28613,13 @@ 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 &%tls_verify_hosts%& or &%tls_try_verify_hosts%& matches the client. +.new +Do not use a certificate which has the OCSP-must-staple extension, +for client use (they are usable for server use). +As TLS has no means for the client to staple before TLS 1.3 it will result +in failed connections. +.wen + If the &%tls_verify_certificates%& option is set on the &(smtp)& transport, it specifies a collection of expected server certificates. These may be @@ -28595,7 +28743,7 @@ Great care should be taken to deal with matters of case, various injection attacks in the string (&`../`& or SQL), and ensuring that a valid filename can always be referenced; it is important to remember that &$tls_in_sni$& is arbitrary unverified data provided prior to authentication. -Further, the initial certificate is loaded before SNI is arrived, so +Further, the initial certificate is loaded before SNI has arrived, so an expansion for &%tls_certificate%& must have a default which is used when &$tls_in_sni$& is empty. @@ -28790,7 +28938,12 @@ Support for client-side operation of DANE can be included at compile time by def in &_Local/Makefile_&. If it has been included, the macro "_HAVE_DANE" will be defined. -The TLSA record for the server may have "certificate usage" of DANE-TA(2) or DANE-EE(3). +A TLSA record consist of 4 fields, the "Certificate Usage", the +"Selector", the "Matching type", and the "Certificate Association Data". +For a detailed description of the TLSA record see +&url(https://tools.ietf.org/html/rfc7671#page-5,RFC 7671). + +The TLSA record for the server may have "Certificate Usage" (1st) field of DANE-TA(2) or DANE-EE(3). These are the "Trust Anchor" and "End Entity" variants. The latter specifies the End Entity directly, i.e. the certificate involved is that of the server (and if only DANE-EE is used then it should be the sole one transmitted during the TLS handshake); @@ -28831,19 +28984,29 @@ If you're not already using a private CA, or it doesn't meet these requirements, then we encourage you to avoid all these issues and use a public CA such as &url(https://letsencrypt.org/,Let's Encrypt) instead. -The TLSA record should have a Selector field of SPKI(1) and a Matching Type field of SHA2-512(2). +The TLSA record should have a "Selector" (2nd) field of SPKI(1) and +a "Matching Type" (3rd) field of SHA2-512(2). -At the time of writing, &url(https://www.huque.com/bin/gen_tlsa) -is useful for quickly generating TLSA records; and commands like +For the "Certificate Authority Data" (4th) field, commands like .code - openssl x509 -in -pubkey -noout /dev/null \ | openssl sha512 \ | awk '{print $2}' .endd -are workable for 4th-field hashes. +are workable to create a hash of the certificate's public key. + +An example TLSA record for DANE-EE(3), SPKI(1), and SHA-512 (2) looks like + +.code + _25._tcp.mail.example.com. TLSA 3 1 2 8BA8A336E... +.endd + +At the time of writing, &url(https://www.huque.com/bin/gen_tlsa) +is useful for quickly generating TLSA records. + For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName). @@ -28877,7 +29040,9 @@ those who use &%hosts_require_ocsp%&, should consider the interaction with DANE For client-side DANE there are three new smtp transport options, &%hosts_try_dane%&, &%hosts_require_dane%& and &%dane_require_tls_ciphers%&. -The require variant will result in failure if the target host is not DNSSEC-secured. +The require variant will result in failure if the target host is not +DNSSEC-secured. To get DNSSEC-secured hostname resolution, use +the &%dnssec_request_domains%& router or transport option. DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records. @@ -28907,7 +29072,8 @@ If DANE is requested and useable (see above) the following transport options are If DANE is not usable, whether requested or not, and CA-anchored verification evaluation is wanted, the above variables should be set appropriately. -Currently the &%dnssec_request_domains%& must be active and &%dnssec_require_domains%& is ignored. +The router and transport option &%dnssec_request_domains%& must not be +set to "never" and &%dnssec_require_domains%& is ignored. If verification was successful using DANE then the "CV" item in the delivery log line will show as "CV=dane". @@ -30790,7 +30956,9 @@ the next &%local_parts%& test. .cindex "&ACL;" "virus scanning" .cindex "&ACL;" "scanning for viruses" This condition is available only when Exim is compiled with the -content-scanning extension. It causes the incoming message to be scanned for +content-scanning extension +and only after a DATA command. +It causes the incoming message to be scanned for viruses. For details, see chapter &<>&. .vitem &*mime_regex&~=&~*&<&'list&~of&~regular&~expressions'&> @@ -32578,6 +32746,15 @@ It supports a &"generic"& interface to scanners called via the shell, and specialized interfaces for &"daemon"& type virus scanners, which are resident in memory and thus are much faster. +.new +Since message data needs to have arrived, +the condition may be only called in ACL defined by +&%acl_smtp_data%&, +&%acl_smtp_data_prdr%&, +&%acl_smtp_mime%& or +&%acl_smtp_dkim%& +.wen + A timeout of 2 minutes is applied to a scanner call (by default); if it expires then a defer action is taken. @@ -39526,6 +39703,11 @@ was received from the client, this records the Distinguished Name from that certificate. .endlist +.new +Any of the above may have an extra hyphen prepended, to indicate the the +corresponding data is untrusted. +.wen + Following the options there is a list of those addresses to which the message is not to be delivered. This set of addresses is initialized from the command line when the &%-t%& option is used and &%extract_addresses_remove_arguments%& @@ -39634,11 +39816,11 @@ There is no dot-stuffing (and no dot-termination). . //////////////////////////////////////////////////////////////////////////// . //////////////////////////////////////////////////////////////////////////// -.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 @@ -39872,15 +40054,28 @@ RFC 6376 lists these tags as RECOMMENDED. Verification of DKIM signatures in SMTP incoming email is done for all messages for which an ACL control &%dkim_disable_verify%& has not been set. +.new +.cindex DKIM "selecting signature algorithms" +Individual classes of signature algorithm can be ignored by changing +the main options &%dkim_verify_hashes%& or &%dkim_verify_keytypes%&. +The &%dkim_verify_minimal%& option can be set to cease verification +processing for a message once the first passing signature is found. +.wen + .cindex authentication "expansion item" Performing verification sets up information used by the -&$authresults$& expansion item. +&%authresults%& expansion item. + +.new +For most purposes the default option settings suffice and the remainder +of this section can be ignored. +.wen -The results of that verification are then made available to the +The results of verification are made available to the &%acl_smtp_dkim%& ACL, which can examine and modify them. -By default, this ACL is called once for each -syntactically(!) correct signature in the incoming message. A missing ACL definition defaults to accept. +By default, the ACL is called once for each +syntactically(!) correct signature in the incoming message. If any ACL call does not accept, the message is not accepted. If a cutthrough delivery was in progress for the message, that is summarily dropped (having wasted the transmission effort). @@ -39891,11 +40086,11 @@ containing the signature status and its details are set up during the runtime of the ACL. Calling the ACL only for existing signatures is not sufficient to build -more advanced policies. For that reason, the global option -&%dkim_verify_signers%&, and a global expansion variable +more advanced policies. For that reason, the main option +&%dkim_verify_signers%&, and an expansion variable &%$dkim_signers%& exist. -The global option &%dkim_verify_signers%& can be set to a colon-separated +The main option &%dkim_verify_signers%& can be set to a colon-separated list of DKIM domains or identities for which the ACL &%acl_smtp_dkim%& is called. It is expanded when the message has been received. At this point, the expansion variable &%$dkim_signers%& already contains a colon-separated @@ -39933,7 +40128,7 @@ If multiple signatures match a domain (or identity), the ACL is called once for each matching signature. -Inside the &%acl_smtp_dkim%&, the following expansion variables are +Inside the DKIM ACL, the following expansion variables are available (from most to least important): @@ -40027,8 +40222,12 @@ DKIM signatures identified as having been signed with historic algorithms (currently, rsa-sha1) have permanently failed evaluation .endd -To enforce this you must have a DKIM ACL which checks this variable -and overwrites the &$dkim_verify_status$& variable as discussed above. +To enforce this you must either have a DKIM ACL which checks this variable +and overwrites the &$dkim_verify_status$& variable as discussed above, +.new +or have set the main option &%dkim_verify_hashes%& to exclude +processing of such signatures. +.wen .vitem &%$dkim_canon_body%& The body canonicalization method. One of 'relaxed' or 'simple'. @@ -40143,8 +40342,12 @@ for more information of what they mean. SPF is a mechanism whereby a domain may assert which IP addresses may transmit messages with its domain in the envelope from, documented by RFC 7208. -For more information on SPF see &url(http://www.openspf.org). -. --- 2018-09-07: still not https +For more information on SPF see &url(http://www.open-spf.org), a static copy of +the &url(http://openspf.org). +. --- 2019-10-28: still not https, open-spf.org is told to be a +. --- web-archive copy of the now dead openspf.org site +. --- See https://www.mail-archive.com/mailop@mailop.org/msg08019.html for a +. --- discussion. Messages sent by a system not authorised will fail checking of such assertions. This includes retransmissions done by traditional forwarders. @@ -40158,7 +40361,7 @@ publishing certain DNS records is all that is required. 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" @@ -40207,7 +40410,7 @@ deny spf = fail message = $sender_host_address is not allowed to send mail from \ ${if def:sender_address_domain \ {$sender_address_domain}{$sender_helo_name}}. \ - Please see http://www.openspf.org/Why?scope=\ + Please see http://www.open-spf.org/Why?scope=\ ${if def:sender_address_domain {mfrom}{helo}};\ identity=${if def:sender_address_domain \ {$sender_address}{$sender_helo_name}};\ @@ -40260,9 +40463,9 @@ In addition to SPF, you can also perform checks for so-called "Best-guess". Strictly speaking, "Best-guess" is not standard SPF, but it is supported by the same framework that enables SPF capability. -Refer to &url(http://www.openspf.org/FAQ/Best_guess_record) +Refer to &url(http://www.open-spf.org/FAQ/Best_guess_record) for a description of what it means. -. --- 2018-09-07: still not https: +. --- 2019-10-28: still not https: To access this feature, simply use the spf_guess condition in place of the spf one. For example: @@ -40295,7 +40498,11 @@ would relax host matching rules to a broader network range. .cindex SPF "lookup expansion" .cindex lookup spf A lookup expansion is also available. It takes an email -address as the key and an IP address as the database: +address as the key and an IP address +.new +(v4 or v6) +.wen +as the database: .code ${lookup {username@domain} spf {ip.ip.ip.ip}} @@ -40303,7 +40510,241 @@ address as the key and an IP address as the database: The lookup will return the same result strings as can appear in &$spf_result$& (pass,fail,softfail,neutral,none,err_perm,err_temp). -Currently, only IPv4 addresses are supported. + + + + + +.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 {$primary_hostname}} +.endd + +.wen @@ -40632,7 +41073,9 @@ Events have names which correspond to the point in process at which they fire. The name is placed in the variable &$event_name$& and the event action expansion must check this, as it will be called for every possible event type. +.new The current list of events is: +.wen .display &`dane:fail after transport `& per connection &`msg:complete after main `& per message @@ -40646,6 +41089,7 @@ The current list of events is: &`tcp:close after transport `& per connection &`tls:cert before both `& per certificate in verification chain &`smtp:connect after transport `& per connection +&`smtp:ehlo after transport `& per connection .endd New event types may be added in future. @@ -40672,6 +41116,7 @@ with the event type: &`msg:host:defer `& error string &`tls:cert `& verification chain depth &`smtp:connect `& smtp banner +&`smtp:ehlo `& smtp ehlo response .endd The :defer events populate one extra variable: &$event_defer_errno$&.