X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/4398228719841b08524520b8c07faeb3bee89705..48224640cb97b694c3ea2f159c3e60d64598ba65:/doc/doc-txt/experimental-spec.txt diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index b981f3b7a..49935fb40 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -430,14 +430,13 @@ package controlled locations (/usr/include and /usr/lib). 2. Use the following global settings to configure DMARC: -Optional: +Required: 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 http://publicsuffix.org/list/. - If unset, "/etc/exim/opendmarc.tlds" (hardcoded) - is used. + See also util/renew-opendmarc-tlds.sh script. Optional: dmarc_history_file Defines the location of a file to log results @@ -448,11 +447,19 @@ dmarc_history_file Defines the location of a file to log results directory of this file is writable by the user exim runs as. -dmarc_forensic_sender The email address to use when sending a +dmarc_forensic_sender 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. - Default: do-not-reply@$default_hostname + + If set, this is expanded and used for the + From: header line; the address is extracted + from it and used for the envelope from. + If not set, the From: header is expanded from + the dsn_from option, and <> is used for the + envelope from. + + Default: unset. 3. By default, the DMARC processing will run for any remote, @@ -525,6 +532,9 @@ Of course, you can also use any other lookup method that Exim supports, including LDAP, Postgres, MySQL, etc, as long as the result is a list of colon-separated strings. +Performing the check sets up information used by the +${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: @@ -548,9 +558,8 @@ expansion variables are available: are "none", "reject" and "quarantine". It is blank when there is any error, including no DMARC record. - o $dmarc_ar_header - This is the entire Authentication-Results header which you can - add using an add_header modifier. +A now-redundant variable $dmarc_ar_header has now been withdrawn. +Use the ${authresults } expansion instead. 5. How to enable DMARC advanced operation: @@ -590,7 +599,6 @@ b. Configure, somewhere before the DATA ACL, the control option to warn dmarc_status = accept : none : off !authenticated = * log_message = DMARC DEBUG: $dmarc_status $dmarc_used_domain - add_header = $dmarc_ar_header warn dmarc_status = !accept !authenticated = * @@ -609,6 +617,8 @@ b. Configure, somewhere before the DATA ACL, the control option to !authenticated = * message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT + warn add_header = :at_start:${authresults {$primary_hostname}} + DSN extra information @@ -707,6 +717,8 @@ an external directory retaining the exim spool format. The spool files can then be processed by external processes and then requeued into exim spool directories for final delivery. +However, note carefully the warnings in the main documentation on +qpool file formats. The motivation/inspiration for the transport is to allow external processes to access email queued by exim and have access to all the @@ -723,7 +735,7 @@ the queuefile driver. The transport only takes one option: * directory - This is used to specify the directory messages should be -copied to +copied to. Expanded. The generic transport options (body_only, current_directory, disable_logging, debug_print, delivery_date_add, envelope_to_add, event_action, group, @@ -791,7 +803,21 @@ standard header. Note that it would be wise to strip incoming messages of A-R headers that claim to be from our own . -There are two new variables: $arc_state and $arc_state_reason. +There are four new variables: + + $arc_state One of pass, fail, none + $arc_state_reason (if fail, why) + $arc_domains colon-sep list of ARC chain domains, in chain order. + problematic elements may have empty list elements + $arc_oldest_pass lowest passing instance number of chain + +Example: + logwrite = oldest-p-ams: <${reduce {$lh_ARC-Authentication-Results:} \ + {} \ + {${if = {$arc_oldest_pass} \ + {${extract {i}{${extract {1}{;}{$item}}}}} \ + {$item} {$value}}} \ + }> Receive log lines for an ARC pass will be tagged "ARC". @@ -803,7 +829,7 @@ An option on the smtp transport, which constructs and prepends to the message an ARC set of headers. The textually-first Authentication-Results: header is used as a basis (you must have added one on entry to the ADMD). Expanded as a whole; if unset, empty or forced-failure then no signing is done. -If it is set, all three elements must be non-empty. +If it is set, all of the first three elements must be non-empty. The fourth element is optional, and if present consists of a comma-separated list of options. The options implemented are @@ -822,12 +848,18 @@ Caveats: * There must be an Authentication-Results header, presumably added by an ACL while receiving the message, for the same ADMD, for arc_sign to succeed. This requires careful coordination between inbound and outbound logic. + + Only one A-R header is taken account of. This is a limitation versus + the ARC spec (which says that all A-R headers from within the ADMD must + be used). + * If passing a message to another system, such as a mailing-list manager (MLM), between receipt and sending, be wary of manipulations to headers made by the MLM. + For instance, Mailman with REMOVE_DKIM_HEADERS==3 might improve deliverability in a pre-ARC world, but that option also renames the Authentication-Results header, which breaks signing. + * Even if you use multiple DKIM keys for different domains, the ARC concept should try to stick to one ADMD, so pick a primary domain and use that for AR headers and outbound signing. @@ -838,6 +870,40 @@ used via the transport in question. + +REQUIRETLS support +------------------ +Ref: https://tools.ietf.org/html/draft-ietf-uta-smtp-require-tls-03 + +If compiled with EXPERIMENTAL_REQUIRETLS support is included for this +feature, where a REQUIRETLS option is added to the MAIL command. +The client may not retry in clear if the MAIL+REQUIRETLS fails (or was never +offered), and the server accepts an obligation that any onward transmission +by SMTP of the messages accepted will also use REQUIRETLS - or generate a +fail DSN. + +The Exim implementation includes +- a main-part option tls_advertise_requiretls; host list, default "*" +- an observability variable $requiretls returning yes/no +- an ACL "control = requiretls" modifier for setting the requirement +- Log lines and Received: headers capitalise the S in the protocol + element: "P=esmtpS" + +Differences from spec: +- we support upgrading the requirement for REQUIRETLS, including adding + it from cold, within an MTA. The spec only define the sourcing MUA + as being able to source the requirement, and makes no mention of upgrade. +- No support is coded for the RequireTLS header (which can be used + to annul DANE and/or STS policiy). [this can _almost_ be done in + transport option expansions, but not quite: it requires tha DANE-present + but STARTTLS-failing targets fallback to cleartext, which current DANE + coding specifically blocks] + +Note that REQUIRETLS is only advertised once a TLS connection is achieved +(in contrast to STARTTLS). If you want to check the advertising, do something +like "swaks -s 127.0.0.1 -tls -q HELO". + + -------------------------------------------------------------- End of file --------------------------------------------------------------