X-Git-Url: https://git.exim.org/exim.git/blobdiff_plain/036ed0dbc98e9534079f5606134d013218467d52..be36e5721725253b7529899884d7fe8ecd5120b9:/doc/doc-txt/experimental-spec.txt diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index 769f0229d..e7a0d0668 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -762,8 +762,10 @@ 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. @@ -773,18 +775,23 @@ EXPERIMENTAL_TPDA=yes in your Local/Makefile -and define the tpda_event_action option in the transport, to -be expanded when the event fires. +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. A new variable, $tpda_event, is set to the event type when the expansion is done. The current list of events is: - msg:delivery - msg:host:defer - tcp:connect - tcp:close - tls:cert - smtp:connect + 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 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 @@ -800,7 +807,7 @@ content is event_dependent: The msg:host:defer event populates one extra variable, $tpda_defer_errno. -The following variables are likely to be useful for most event types: +The following variables are likely to be useful depending on the event type: router_name, transport_name local_part, domain @@ -808,6 +815,7 @@ The following variables are likely to be useful for most event types: tls_out_peercert lookup_dnssec_authenticated, tls_out_dane sending_ip_address, sending_port + message_exim_id An example might look like: @@ -823,13 +831,10 @@ tpda_event_action = ${if = {msg:delivery}{$tpda_event} \ '${quote_pgsql:$message_exim_id}')}} \ } {}} -The string is expanded after the delivery completes and any +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. -During the expansion the tpda_event variable will contain the -string-list "msg:delivery". - The expansion of the tpda_event_action option should normally return an empty string. Should it return anything else the @@ -837,6 +842,7 @@ following will be forced: msg:delivery (ignored) msg:host:defer (ignored) + msg:fail:delivery (ignored) tcp:connect do not connect tcp:close (ignored) tls:cert refuse verification @@ -1172,6 +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 @@ -1196,12 +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 @@ -1213,7 +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. @@ -1230,13 +1240,13 @@ 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 +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: @@ -1247,10 +1257,10 @@ DANE is in use, to: 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_require_ocsp or -hosts_request_ocsp includes the string "tls_out_tlsa_usage", -they are re-expanded in time to control the OCSP request. +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 @@ -1265,9 +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