X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/594706ea2e56fe8c972eab772bd3e58c7a0c89ab..0160bfb8f6435449f80ccd8a8d20a0d749c0624d:/doc/doc-txt/experimental-spec.txt diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index c060a6c5a..e7a0d0668 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -762,87 +762,94 @@ b. Configure, somewhere before the DATA ACL, the control option to Transport post-delivery actions -------------------------------------------------------------- -An arbitrary per-transport string can be expanded on successful delivery, +An arbitrary per-transport string can be expanded upon various transport events and (for SMTP transports) a second string on deferrals caused by a host error. +Additionally a main-section configuration option can be expanded on some +per-message events. This feature may be used, for example, to write exim internal log information (not available otherwise) into a database. -In order to use the feature, you must set +In order to use the feature, you must compile with EXPERIMENTAL_TPDA=yes in your Local/Makefile -and define the expandable strings in the runtime config file, to -be executed at end of delivery. +and define one or both of +- the tpda_event_action option in the transport +- the delivery_event_action +to be expanded when the event fires. -Additionally, there are 6 more variables, available at end of -delivery: +A new variable, $tpda_event, is set to the event type when the +expansion is done. The current list of events is: -tpda_delivery_ip IP of host, which has accepted delivery -tpda_delivery_port Port of remote host which has accepted delivery -tpda_delivery_fqdn FQDN of host, which has accepted delivery -tpda_delivery_local_part local part of address being delivered -tpda_delivery_domain domain part of address being delivered -tpda_delivery_confirmation SMTP confirmation message + msg:complete main per message + msg:delivery transport per recipient + msg:host:defer transport per attempt + msg:fail:delivery main per recipient + msg:fail:internal main per recipient + tcp:connect transport per connection + tcp:close transport per connection + tls:cert transport per certificate in verification chain + smtp:connect transport per connection -In case of a deferral caused by a host-error: -tpda_defer_errno Error number -tpda_defer_errstr Error string possibly containing more details +The expansion is called for all event types, and should use the $tpda_event +value to decide when to act. The variable data is a colon-separated +list, describing an event tree. -The $router_name and $transport_name variables are also usable. +There is an auxilary variable, $tpda_data, for which the +content is event_dependent: + msg:delivery smtp confirmation mssage + msg:host:defer error string + tls:cert verification chain depth + smtp:connect smtp banner -To take action after successful deliveries, set the following option -on any transport of interest. +The msg:host:defer event populates one extra variable, $tpda_defer_errno. + +The following variables are likely to be useful depending on the event type: + + router_name, transport_name + local_part, domain + host, host_address, host_port + tls_out_peercert + lookup_dnssec_authenticated, tls_out_dane + sending_ip_address, sending_port + message_exim_id -tpda_delivery_action An example might look like: -tpda_delivery_action = \ -${lookup pgsql {SELECT * FROM record_Delivery( \ +tpda_event_action = ${if = {msg:delivery}{$tpda_event} \ +{${lookup pgsql {SELECT * FROM record_Delivery( \ '${quote_pgsql:$sender_address_domain}',\ '${quote_pgsql:${lc:$sender_address_local_part}}', \ - '${quote_pgsql:$tpda_delivery_domain}', \ - '${quote_pgsql:${lc:$tpda_delivery_local_part}}', \ - '${quote_pgsql:$tpda_delivery_ip}', \ - '${quote_pgsql:${lc:$tpda_delivery_fqdn}}', \ - '${quote_pgsql:$message_exim_id}')}} - -The string is expanded after the delivery completes and any + '${quote_pgsql:$domain}', \ + '${quote_pgsql:${lc:$local_part}}', \ + '${quote_pgsql:$host_address}', \ + '${quote_pgsql:${lc:$host}}', \ + '${quote_pgsql:$message_exim_id}')}} \ +} {}} + +The string is expanded for each of the supported events and any side-effects will happen. The result is then discarded. Note that for complex operations an ACL expansion can be used. -In order to log host deferrals, add the following option to an SMTP -transport: +The expansion of the tpda_event_action option should normally +return an empty string. Should it return anything else the +following will be forced: -tpda_host_defer_action + msg:delivery (ignored) + msg:host:defer (ignored) + msg:fail:delivery (ignored) + tcp:connect do not connect + tcp:close (ignored) + tls:cert refuse verification + smtp:connect close connection -This is a private option of the SMTP transport. It is intended to -log failures of remote hosts. It is executed only when exim has -attempted to deliver a message to a remote host and failed due to -an error which doesn't seem to be related to the individual -message, sender, or recipient address. -See section 47.2 of the exim documentation for more details on how -this is determined. -Example: -tpda_host_defer_action = \ -${lookup mysql {insert into delivlog set \ - msgid = '${quote_mysql:$message_exim_id}', \ - senderlp = '${quote_mysql:${lc:$sender_address_local_part}}', \ - senderdom = '${quote_mysql:$sender_address_domain}', \ - delivlp = '${quote_mysql:${lc:$tpda_delivery_local_part}}', \ - delivdom = '${quote_mysql:$tpda_delivery_domain}', \ - delivip = '${quote_mysql:$tpda_delivery_ip}', \ - delivport = '${quote_mysql:$tpda_delivery_port}', \ - delivfqdn = '${quote_mysql:$tpda_delivery_fqdn}', \ - deliverrno = '${quote_mysql:$tpda_defer_errno}', \ - deliverrstr = '${quote_mysql:$tpda_defer_errstr}' \ - }} Redis Lookup @@ -1171,6 +1178,10 @@ admins of the target server. The attack surface presented by (a) is thought to be smaller than that of the set of root CAs. +It also allows the server to declare (implicitly) that +connections to it should use TLS. An MITM could simply +fail to pass on a server's STARTTLS. + DANE scales better than having to maintain (and side-channel communicate) copies of server certificates for every possible target server. It also scales @@ -1195,12 +1206,12 @@ There are no changes to Exim specific to server-side operation of DANE. The TLSA record for the server may have "certificate -usage" of DANE_TA(2) or DANE_EE(3). The latter specifies +usage" of DANE-TA(2) or DANE-EE(3). The latter specifies the End Entity directly, i.e. the certificate involved is that of the server (and should be the sole one transmitted during the TLS handshake); this is appropriate for a single system, using a self-signed certificate. - DANE_TA usage is effectively declaring a specific CA + DANE-TA usage is effectively declaring a specific CA to be used; this might be a private CA or a public, well-known one. A private CA at simplest is just a self-signed certificate which is used to sign @@ -1212,7 +1223,7 @@ the entire certificate chain from CA to server-certificate. If a public CA is used then all clients must be primed with it (losing one advantage of DANE) - but the attack surface is reduced from all public CAs to that single CA. -DANE_TA is commonly used for several services and/or +DANE-TA is commonly used for several services and/or servers, each having a TLSA query-domain CNAME record, all of which point to a single TLSA record. @@ -1229,31 +1240,32 @@ is useful for quickly generating TLSA records; and commands like are workable for 4th-field hashes. -For use with the DANE_TA model, server certificates +For use with the DANE-TA model, server certificates must have a correct name (SubjectName or SubjectAltName). The use of OCSP-stapling should be considered, allowing for fast revocation of certificates (which would otherwise be limited by the DNS TTL on the TLSA records). However, -this is likely to only be usable with DANE_TA. NOTE: the -default is to request OCSP for all hosts; the certificate -chain in DANE_EE usage will be insufficient to validate -the OCSP proof and verification will fail. Either disable -OCSP completely or use the (new) variable $tls_out_tlsa_usage -like so: - - hosts_request_ocsp = ${if or { {= {4}{$tls_out_tlsa_usage}} \ - {= {0}{$tls_out_tlsa_usage}} } \ +this is likely to only be usable with DANE-TA. NOTE: the +default of requesting OCSP for all hosts is modified iff +DANE is in use, to: + + hosts_request_ocsp = ${if or { {= {0}{$tls_out_tlsa_usage}} \ + {= {4}{$tls_out_tlsa_usage}} } \ {*}{}} -The variable is a bitfield with numbered bits set for TLSA -record usage codes. The zero above means DANE was not in use, -the four means that only DANE_TA usage TLSA records were -found. If the definition of hosts_require_ocsp or -hosts_request_ocsp includes the string "tls_out_tlsa_usage", -they are re-expanded in time to control the OCSP request. -[ All a bit complicated. Should we make that definition -the default? Should we override the user's definition? ] +The (new) variable $tls_out_tlsa_usage is a bitfield with +numbered bits set for TLSA record usage codes. +The zero above means DANE was not in use, +the four means that only DANE-TA usage TLSA records were +found. If the definition of hosts_request_ocsp includes the +string "tls_out_tlsa_usage", they are re-expanded in time to +control the OCSP request. + +This modification of hosts_request_ocsp is only done if +it has the default value of "*". Admins who change it, and +those who use hosts_require_ocsp, should consider the interaction +with DANE in their OCSP settings. For client-side DANE there are two new smtp transport options, @@ -1263,9 +1275,15 @@ hosts_try_dane and hosts_require_dane. They do the obvious thing. DANE will only be usable if the target host has DNSSEC-secured MX, A and TLSA records. +A TLSA lookup will be done if either of the above options match +and the host-lookup succeded using dnssec. +If the TLSA lookup succeeds, a TLS connection will be required +for the host. + (TODO: specify when fallback happens vs. when the host is not used) If dane is in use the following transport options are ignored: + hosts_require_tls tls_verify_hosts tls_try_verify_hosts tls_verify_certificates