X-Git-Url: https://git.exim.org/users/jgh/exim.git/blobdiff_plain/0f06b4f296802e4e13188c740ea09419931a3020..a39bd74d3e94:/doc/doc-txt/experimental-spec.txt?ds=sidebyside diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index 2f44fce26..e6e066c04 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -623,10 +623,10 @@ 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. - control = dmarc_forensic_enable + control = dmarc_enable_forensic (AGAIN: You can choose not to send these forensic reports by simply -not putting the dmarc_forensic_enable control line at any point in +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.) @@ -755,15 +755,16 @@ b. Configure, somewhere before the DATA ACL, the control option to deny dmarc_status = reject !authenticated = * - message = Message from $domain_used_domain failed sender's DMARC policy, REJECT + message = Message from $dmarc_used_domain failed sender's DMARC policy, REJECT -Transport post-delivery actions +Event Actions -------------------------------------------------------------- -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. +(Renamed from TPDA, Transport post-delivery actions) + +An arbitrary per-transport string can be expanded upon various transport events. 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 @@ -771,33 +772,33 @@ This feature may be used, for example, to write exim internal log information In order to use the feature, you must compile with -EXPERIMENTAL_TPDA=yes +EXPERIMENTAL_EVENT=yes in your Local/Makefile and define one or both of -- the tpda_event_action option in the transport -- the delivery_event_action +- the event_action option in the transport +- the event_action main option to be expanded when the event fires. -A new variable, $tpda_event, is set to the event type when the +A new variable, $event_name, is set to the event type when the expansion is done. The current list of events is: - 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 + msg:complete after main per message + msg:delivery after transport per recipient + msg:host:defer after transport per attempt + msg:fail:delivery after main per recipient + msg:fail:internal after main per recipient + tcp:connect before transport per connection + tcp:close after transport per connection + tls:cert before both per certificate in verification chain + smtp:connect after transport per connection + +The expansion is called for all event types, and should use the $event_name value to decide when to act. The variable data is a colon-separated list, describing an event tree. -There is an auxilary variable, $tpda_data, for which the +There is an auxilary variable, $event_data, for which the content is event_dependent: msg:delivery smtp confirmation mssage @@ -805,7 +806,7 @@ content is event_dependent: tls:cert verification chain depth smtp:connect smtp banner -The msg:host:defer event populates one extra variable, $tpda_defer_errno. +The msg:host:defer event populates one extra variable, $event_defer_errno. The following variables are likely to be useful depending on the event type: @@ -815,12 +816,12 @@ The following variables are likely to be useful depending on the event type: tls_out_peercert lookup_dnssec_authenticated, tls_out_dane sending_ip_address, sending_port - message_exim_id + message_exim_id, verify_mode An example might look like: -tpda_event_action = ${if = {msg:delivery}{$tpda_event} \ +event_action = ${if eq {msg:delivery}{$event_name} \ {${lookup pgsql {SELECT * FROM record_Delivery( \ '${quote_pgsql:$sender_address_domain}',\ '${quote_pgsql:${lc:$sender_address_local_part}}', \ @@ -831,12 +832,12 @@ tpda_event_action = ${if = {msg:delivery}{$tpda_event} \ '${quote_pgsql:$message_exim_id}')}} \ } {}} -The string is expanded for each of the supported events and any -side-effects will happen. The result is then discarded. +The string is expanded when each of the supported events occur +and any side-effects of the expansion will happen. Note that for complex operations an ACL expansion can be used. -The expansion of the tpda_event_action option should normally +The expansion of the event_action option should normally return an empty string. Should it return anything else the following will be forced: @@ -848,8 +849,13 @@ following will be forced: tls:cert refuse verification smtp:connect close connection +No other use is made of the result string. +Known issues: +- the tls:cert event is only called for the cert chain elements + received over the wire, with GnuTLS. OpenSSL gives the entire + chain including thse loaded locally. Redis Lookup @@ -1078,82 +1084,39 @@ QUIT 221 mail.example.net closing connection -DSN Support --------------------------------------------------------------- - -DSN Support tries to add RFC 3461 support to Exim. It adds support for -*) the additional parameters for MAIL FROM and RCPT TO -*) RFC complient MIME DSN messages for all of - success, failure and delay notifications -*) dsn_advertise_hosts main option to select which hosts are able - to use the extension -*) dsn_lasthop router switch to end DSN processing - -In case of failure reports this means that the last three parts, the message body -intro, size info and final text, of the defined template are ignored since there is no -logical place to put them in the MIME message. - -All the other changes are made without changing any defaults - -Building exim: --------------- - -Define -EXPERIMENTAL_DSN=YES -in your Local/Makefile. - -Configuration: --------------- -All DSNs are sent in MIME format if you built exim with EXPERIMENTAL_DSN=YES -No option needed to activate it, and no way to turn it off. - -Failure and delay DSNs are triggered as usual except a sender used NOTIFY=... -to prevent them. -Support for Success DSNs is added and activated by NOTIFY=SUCCESS by clients. -Add -dsn_advertise_hosts = * -or a more restrictive host_list to announce DSN in EHLO answers - -Those hosts can then use NOTIFY,ENVID,RET,ORCPT options. - -If a message is relayed to a DSN aware host without changing the envelope -recipient the options are passed along and no success DSN is generated. - -A redirect router will always trigger a success DSN if requested and the DSN -options are not passed any further. +SOCKS +------------------------------------------------------------ +Support for proxying outbound SMTP via a Socks 5 proxy +(RFC 1928) is included if Exim is compiled with +EXPERIMENTAL_SOCKS defined. -A success DSN always contains the recipient address as submitted by the -client as required by RFC. Rewritten addresses are never exposed. +If an smtp transport has a nonempty socks_proxy option +defined, this is active. The option is expanded and +should be a list (colon-separated by default) of +proxy specifiers. Each proxy specifier is a list +(space-separated by default) where the initial element +is an IP address and any subsequent elements are options. -If you used DSN patch up to 1.3 before remove all "dsn_process" switches from -your routers since you don't need them anymore. There is no way to "gag" -success DSNs anymore. Announcing DSN means answering as requested. +Options are a string =. +These options are currently defined: +- "auth", with possible values "none" and "name". + Using "name" selects username/password authentication + per RFC 1929. Default is "none". +- "name" sets the authentication username. Default is empty. +- "pass" sets the authentication password. Default is empty. +- "port" sets the tcp port number for the proxy. Default is 1080. +- "tmo" sets a connection timeout in seconds for this proxy. Default is 5. -You can prevent Exim from passing DSN options along to other DSN aware hosts by defining -dsn_lasthop -in a router. Exim will then send the success DSN himself if requested as if -the next hop does not support DSN. -Adding it to a redirect router makes no difference. +Proxies from the list are tried in order until +one responds. The timeout for the overall connection +applies to the set of proxied attempts. +If events are used, the remote IP/port during a +tcp:connect event will be that of the proxy. -Certificate name checking --------------------------------------------------------------- -The X509 certificates used for TLS are supposed be verified -that they are owned by the expected host. The coding of TLS -support to date has not made these checks. -If built with EXPERIMENTAL_CERTNAMES defined, code is -included to do so, and a new smtp transport option -"tls_verify_cert_hostname" supported which takes a list of -names for which the checks must be made. The host must -also be in "tls_verify_hosts". - -Both Subject and Subject-Alternate-Name certificate fields -are supported, as are wildcard certificates (limited to -a single wildcard being the initial component of a 3-or-more -component FQDN). DANE @@ -1178,6 +1141,10 @@ 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 @@ -1202,12 +1169,12 @@ 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 @@ -1219,7 +1186,7 @@ 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. @@ -1236,13 +1203,13 @@ 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: @@ -1253,10 +1220,10 @@ 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 @@ -1271,15 +1238,26 @@ 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 a TLSA lookup is done and succeeds, a DANE-verified 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: +If DANE is requested and useable (see above) the following transport +options are ignored: + hosts_require_tls tls_verify_hosts tls_try_verify_hosts tls_verify_certificates tls_crl tls_verify_cert_hostnames +If DANE is not usable, whether requested or not, and CA-anchored +verification evaluation is wanted, the above variables should be set +appropriately. + Currently dnssec_request_domains must be active (need to think about that) and dnssec_require_domains is ignored. @@ -1288,7 +1266,7 @@ in the delivery log line will show as "CV=dane". There is a new variable $tls_out_dane which will have "yes" if verification succeeded using DANE and "no" otherwise (only useful -in combination with EXPERIMENTAL_TPDA), and a new variable +in combination with EXPERIMENTAL_EVENT), and a new variable $tls_out_tlsa_usage (detailed above).