X-Git-Url: https://vcs.fsf.org/?p=exim.git;a=blobdiff_plain;f=doc%2Fdoc-txt%2Fexperimental-spec.txt;h=0b1afb2478f0e142e123c454554dea2f78cd5d78;hp=0eeb939bfdafc8972301d195fe0d7903a635cdd3;hb=43042f3dab3201f2339f2be0a70e0d67ae7e5386;hpb=0d7911ea3aa8124490bd9272474aeba8b4a6313e diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index 0eeb939bf..0b1afb247 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -6,7 +6,7 @@ about experimental features, all of which are unstable and liable to incompatible change. -Brightmail AntiSpam (BMI) suppport +Brightmail AntiSpam (BMI) support -------------------------------------------------------------- Brightmail AntiSpam is a commercial package. Please see @@ -42,7 +42,7 @@ These four steps are explained in more details below. 1) Adding support for BMI at compile time To compile with BMI support, you need to link Exim against - the Brighmail client SDK, consisting of a library + the Brightmail client SDK, consisting of a library (libbmiclient_single.so) and a header file (bmi_api.h). You'll also need to explicitly set a flag in the Makefile to include BMI support in the Exim binary. Both can be achieved @@ -448,16 +448,29 @@ spf_guess = v=spf1 a/16 mx/16 ptr ?all would relax host matching rules to a broader network range. +A lookup expansion is also available. It takes an email +address as the key and an IP address as the database: + + ${lookup {username@domain} spf {ip.ip.ip.ip}} + +The lookup will return the same result strings as they can appear in +$spf_result (pass,fail,softfail,neutral,none,err_perm,err_temp). +Currently, only IPv4 addresses are supported. + + + SRS (Sender Rewriting Scheme) Support -------------------------------------------------------------- Exiscan currently includes SRS support via Miles Wilton's libsrs_alt library. The current version of the supported -library is 0.5. +library is 0.5, there are reports of 1.0 working. In order to use SRS, you must get a copy of libsrs_alt from -http://srs.mirtol.com/ +https://opsec.eu/src/srs/ + +(not the original source, which has disappeared.) Unpack the tarball, then refer to MTAs/README.EXIM to proceed. You need to set @@ -467,8 +480,10 @@ EXPERIMENTAL_SRS=yes in your Local/Makefile. + DCC Support -------------------------------------------------------------- +Distributed Checksum Clearinghouse; http://www.rhyolite.com/dcc/ *) Building exim @@ -538,7 +553,7 @@ Then set something like mout-xforward.gmx.net 82.165.159.12 mout.gmx.net 212.227.15.16 -Use a reasonable IP. eg. one the sending cluster acutally uses. +Use a reasonable IP. eg. one the sending cluster actually uses. DMARC Support -------------------------------------------------------------- @@ -759,366 +774,6 @@ b. Configure, somewhere before the DATA ACL, the control option to -Event Actions --------------------------------------------------------------- - -(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 -(not available otherwise) into a database. - -In order to use the feature, you must compile with - -EXPERIMENTAL_EVENT=yes - -in your Local/Makefile - -and define one or both of -- the event_action option in the transport -- the event_action main option -to be expanded when the event fires. - -A new variable, $event_name, is set to the event type when the -expansion is done. The current list of events is: - - 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, $event_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 - -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: - - 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, verify_mode - - -An example might look like: - -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}}', \ - '${quote_pgsql:$domain}', \ - '${quote_pgsql:${lc:$local_part}}', \ - '${quote_pgsql:$host_address}', \ - '${quote_pgsql:${lc:$host}}', \ - '${quote_pgsql:$message_exim_id}')}} \ -} {}} - -The string is expanded 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 event_action option should normally -return an empty string. Should it return anything else the -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 - 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 --------------------------------------------------------------- - -Redis is open source advanced key-value data store. This document -does not explain the fundamentals, you should read and understand how -it works by visiting the website at http://www.redis.io/. - -Redis lookup support is added via the hiredis library. Visit: - - https://github.com/redis/hiredis - -to obtain a copy, or find it in your operating systems package repository. -If building from source, this description assumes that headers will be in -/usr/local/include, and that the libraries are in /usr/local/lib. - -1. In order to build exim with Redis lookup support add - -EXPERIMENTAL_REDIS=yes - -to your Local/Makefile. (Re-)build/install exim. exim -d should show -Experimental_Redis in the line "Support for:". - -EXPERIMENTAL_REDIS=yes -LDFLAGS += -lhiredis -# CFLAGS += -I/usr/local/include -# LDFLAGS += -L/usr/local/lib - -The first line sets the feature to include the correct code, and -the second line says to link the hiredis libraries into the -exim binary. The commented out lines should be uncommented if you -built hiredis from source and installed in the default location. -Adjust the paths if you installed them elsewhere, but you do not -need to uncomment them if an rpm (or you) installed them in the -package controlled locations (/usr/include and /usr/lib). - - -2. Use the following global settings to configure Redis lookup support: - -Required: -redis_servers This option provides a list of Redis servers - and associated connection data, to be used in - conjunction with redis lookups. The option is - only available if Exim is configured with Redis - support. - -For example: - -redis_servers = 127.0.0.1/10/ - using database 10 with no password -redis_servers = 127.0.0.1//password - to make use of the default database of 0 with a password -redis_servers = 127.0.0.1// - for default database of 0 with no password - -3. Once you have the Redis servers defined you can then make use of the -experimental Redis lookup by specifying ${lookup redis{}} in a lookup query. - -4. Example usage: - -(Host List) -hostlist relay_from_ips = <\n ${lookup redis{SMEMBERS relay_from_ips}} - -Where relay_from_ips is a Redis set which contains entries such as "192.168.0.0/24" "10.0.0.0/8" and so on. -The result set is returned as -192.168.0.0/24 -10.0.0.0/8 -.. -. - -(Domain list) -domainlist virtual_domains = ${lookup redis {HGET $domain domain}} - -Where $domain is a hash which includes the key 'domain' and the value '$domain'. - -(Adding or updating an existing key) -set acl_c_spammer = ${if eq{${lookup redis{SPAMMER_SET}}}{OK}} - -Where SPAMMER_SET is a macro and it is defined as - -"SET SPAMMER " - -(Getting a value from Redis) - -set acl_c_spam_host = ${lookup redis{GET...}} - - -Proxy Protocol Support --------------------------------------------------------------- - -Exim now has Experimental "Proxy Protocol" support. It was built on -specifications from: -http://haproxy.1wt.eu/download/1.5/doc/proxy-protocol.txt -Above URL revised May 2014 to change version 2 spec: -http://git.1wt.eu/web?p=haproxy.git;a=commitdiff;h=afb768340c9d7e50d8e - -The purpose of this function is so that an application load balancer, -such as HAProxy, can sit in front of several Exim servers and Exim -will log the IP that is connecting to the proxy server instead of -the IP of the proxy server when it connects to Exim. It resets the -$sender_address_host and $sender_address_port to the IP:port of the -connection to the proxy. It also re-queries the DNS information for -this new IP address so that the original sender's hostname and IP -get logged in the Exim logfile. There is no logging if a host passes or -fails Proxy Protocol negotiation, but it can easily be determined and -recorded in an ACL (example is below). - -1. To compile Exim with Proxy Protocol support, put this in -Local/Makefile: - -EXPERIMENTAL_PROXY=yes - -2. Global configuration settings: - -proxy_required_hosts = HOSTLIST - -The proxy_required_hosts option will require any IP in that hostlist -to use Proxy Protocol. The specification of Proxy Protocol is very -strict, and if proxy negotiation fails, Exim will not allow any SMTP -command other than QUIT. (See end of this section for an example.) -The option is expanded when used, so it can be a hostlist as well as -string of IP addresses. Since it is expanded, specifying an alternate -separator is supported for ease of use with IPv6 addresses. - -To log the IP of the proxy in the incoming logline, add: - log_selector = +proxy - -A default incoming logline (wrapped for appearance) will look like this: - - 2013-11-04 09:25:06 1VdNti-0001OY-1V <= me@example.net - H=mail.example.net [1.2.3.4] P=esmtp S=433 - -With the log selector enabled, an email that was proxied through a -Proxy Protocol server at 192.168.1.2 will look like this: - - 2013-11-04 09:25:06 1VdNti-0001OY-1V <= me@example.net - H=mail.example.net [1.2.3.4] P=esmtp PRX=192.168.1.2 S=433 - -3. In the ACL's the following expansion variables are available. - -proxy_host_address The (internal) src IP of the proxy server - making the connection to the Exim server. -proxy_host_port The (internal) src port the proxy server is - using to connect to the Exim server. -proxy_target_address The dest (public) IP of the remote host to - the proxy server. -proxy_target_port The dest port the remote host is using to - connect to the proxy server. -proxy_session Boolean, yes/no, the connected host is required - to use Proxy Protocol. - -There is no expansion for a failed proxy session, however you can detect -it by checking if $proxy_session is true but $proxy_host is empty. As -an example, in my connect ACL, I have: - - warn condition = ${if and{ {bool{$proxy_session}} \ - {eq{$proxy_host_address}{}} } } - log_message = Failed required proxy protocol negotiation \ - from $sender_host_name [$sender_host_address] - - warn condition = ${if and{ {bool{$proxy_session}} \ - {!eq{$proxy_host_address}{}} } } - # But don't log health probes from the proxy itself - condition = ${if eq{$proxy_host_address}{$sender_host_address} \ - {false}{true}} - log_message = Successfully proxied from $sender_host_name \ - [$sender_host_address] through proxy protocol \ - host $proxy_host_address - - # Possibly more clear - warn logwrite = Remote Source Address: $sender_host_address:$sender_host_port - logwrite = Proxy Target Address: $proxy_target_address:$proxy_target_port - logwrite = Proxy Internal Address: $proxy_host_address:$proxy_host_port - logwrite = Internal Server Address: $received_ip_address:$received_port - - -4. Recommended ACL additions: - - Since the real connections are all coming from your proxy, and the - per host connection tracking is done before Proxy Protocol is - evaluated, smtp_accept_max_per_host must be set high enough to - handle all of the parallel volume you expect per inbound proxy. - - With the smtp_accept_max_per_host set so high, you lose the ability - to protect your server from massive numbers of inbound connections - from one IP. In order to prevent your server from being DOS'd, you - need to add a per connection ratelimit to your connect ACL. I - suggest something like this: - - # Set max number of connections per host - LIMIT = 5 - # Or do some kind of IP lookup in a flat file or database - # LIMIT = ${lookup{$sender_host_address}iplsearch{/etc/exim/proxy_limits}} - - defer message = Too many connections from this IP right now - ratelimit = LIMIT / 5s / per_conn / strict - - -5. Runtime issues to be aware of: - - The proxy has 3 seconds (hard-coded in the source code) to send the - required Proxy Protocol header after it connects. If it does not, - the response to any commands will be: - "503 Command refused, required Proxy negotiation failed" - - If the incoming connection is configured in Exim to be a Proxy - Protocol host, but the proxy is not sending the header, the banner - does not get sent until the timeout occurs. If the sending host - sent any input (before the banner), this causes a standard Exim - synchronization error (i.e. trying to pipeline before PIPELINING - was advertised). - - This is not advised, but is mentioned for completeness if you have - a specific internal configuration that you want this: If the Exim - server only has an internal IP address and no other machines in your - organization will connect to it to try to send email, you may - simply set the hostlist to "*", however, this will prevent local - mail programs from working because that would require mail from - localhost to use Proxy Protocol. Again, not advised! - -6. Example of a refused connection because the Proxy Protocol header was -not sent from a host configured to use Proxy Protocol. In the example, -the 3 second timeout occurred (when a Proxy Protocol banner should have -been sent), the banner was displayed to the user, but all commands are -rejected except for QUIT: - -# nc mail.example.net 25 -220-mail.example.net, ESMTP Exim 4.82+proxy, Mon, 04 Nov 2013 10:45:59 -220 -0800 RFC's enforced -EHLO localhost -503 Command refused, required Proxy negotiation failed -QUIT -221 mail.example.net closing connection - - - - -SOCKS ------------------------------------------------------------- -Support for proxying outbound SMTP via a Socks 5 proxy -(RFC 1928) is included if Exim is compiled with -EXPERIMENTAL_SOCKS defined. - -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. - -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. - -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. - - - - DANE ------------------------------------------------------------ DNS-based Authentication of Named Entities, as applied @@ -1232,18 +887,20 @@ with DANE in their OCSP settings. For client-side DANE there are two new smtp transport options, -hosts_try_dane and hosts_require_dane. They do the obvious thing. +hosts_try_dane and hosts_require_dane. [ should they be domain-based rather than host-based? ] +Hosts_require_dane will result in failure if the target host +is not DNSSEC-secured. + 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. +and the host-lookup succeeded 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) +will be required for the host. If it does not, the host will not +be used; there is no fallback to non-DANE or non-TLS. If DANE is requested and useable (see above) the following transport options are ignored: @@ -1271,12 +928,149 @@ $tls_out_tlsa_usage (detailed above). -SMTPUTF8 ------------------------------------------------------------- -Internationalised mail name handling. -RFCs 6530, 6533, 5890 +DSN extra information +--------------------- +If compiled with EXPERIMENTAL_DSN_INFO extra information will be added +to DSN fail messages ("bounces"), when available. The intent is to aid +tracing of specific failing messages, when presented with a "bounce" +complaint and needing to search logs. + + +The remote MTA IP address, with port number if nonstandard. +Example: + Remote-MTA: X-ip; [127.0.0.1]:587 +Rationale: + Several addresses may correspond to the (already available) + dns name for the remote MTA. + +The remote MTA connect-time greeting. +Example: + X-Remote-MTA-smtp-greeting: X-str; 220 the.local.host.name ESMTP Exim x.yz Tue, 2 Mar 1999 09:44:33 +0000 +Rationale: + This string sometimes presents the remote MTA's idea of its + own name, and sometimes identifies the MTA software. + +The remote MTA response to HELO or EHLO. +Example: + X-Remote-MTA-helo-response: X-str; 250-the.local.host.name Hello localhost [127.0.0.1] +Limitations: + Only the first line of a multiline response is recorded. +Rationale: + This string sometimes presents the remote MTA's view of + the peer IP connecting to it. + +The reporting MTA detailed diagnostic. +Example: + X-Exim-Diagnostic: X-str; SMTP error from remote mail server after RCPT TO:: 550 hard error +Rationale: + This string sometimes give extra information over the + existing (already available) Diagnostic-Code field. + + +Note that non-RFC-documented field names and data types are used. + + +LMDB Lookup support +------------------- +LMDB is an ultra-fast, ultra-compact, crash-proof key-value embedded data store. +It is modeled loosely on the BerkeleyDB API. You should read about the feature +set as well as operation modes at https://symas.com/products/lightning-memory-mapped-database/ + +LMDB single key lookup support is provided by linking to the LMDB C library. +The current implementation does not support writing to the LMDB database. + +Visit https://github.com/LMDB/lmdb to download the library or find it in your +operating systems package repository. + +If building from source, this description assumes that headers will be in +/usr/local/include, and that the libraries are in /usr/local/lib. -Compile with libidn. +1. In order to build exim with LMDB lookup support add or uncomment + +EXPERIMENTAL_LMDB=yes + +to your Local/Makefile. (Re-)build/install exim. exim -d should show +Experimental_LMDB in the line "Support for:". + +EXPERIMENTAL_LMDB=yes +LDFLAGS += -llmdb +# CFLAGS += -I/usr/local/include +# LDFLAGS += -L/usr/local/lib + +The first line sets the feature to include the correct code, and +the second line says to link the LMDB libraries into the +exim binary. The commented out lines should be uncommented if you +built LMDB from source and installed in the default location. +Adjust the paths if you installed them elsewhere, but you do not +need to uncomment them if an rpm (or you) installed them in the +package controlled locations (/usr/include and /usr/lib). + +2. Create your LMDB files, you can use the mdb_load utility which is +part of the LMDB distribution our your favourite language bindings. + +3. Add the single key lookups to your exim.conf file, example lookups +are below. + +${lookup{$sender_address_domain}lmdb{/var/lib/baruwa/data/db/relaydomains.mdb}{$value}} +${lookup{$sender_address_domain}lmdb{/var/lib/baruwa/data/db/relaydomains.mdb}{$value}fail} +${lookup{$sender_address_domain}lmdb{/var/lib/baruwa/data/db/relaydomains.mdb}} + + +Queuefile transport +------------------- +Queuefile is a pseudo transport which does not perform final delivery. +It simply copies the exim spool files out of the spool directory into +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. + +The motivation/inspiration for the transport is to allow external +processes to access email queued by exim and have access to all the +information which would not be available if the messages were delivered +to the process in the standard email formats. + +The mailscanner package is one of the processes that can take advantage +of this transport to filter email. + +The transport can be used in the same way as the other existing transports, +i.e by configuring a router to route mail to a transport configured with +the queuefile driver. + +The transport only takes one option: + +* directory - This is used to specify the directory messages should be +copied to + +The generic transport options (body_only, current_directory, disable_logging, +debug_print, delivery_date_add, envelope_to_add, event_action, group, +headers_add, headers_only, headers_remove, headers_rewrite, home_directory, +initgroups, max_parallel, message_size_limit, rcpt_include_affixes, +retry_use_local_part, return_path, return_path_add, shadow_condition, +shadow_transport, transport_filter, transport_filter_timeout, user) are +ignored. + +Sample configuration: + +(Router) + +scan: + driver = accept + transport = scan + +(Transport) + +scan: + driver = queuefile + directory = /var/spool/baruwa-scanner/input + + +In order to build exim with Queuefile transport support add or uncomment + +EXPERIMENTAL_QUEUEFILE=yes + +to your Local/Makefile. (Re-)build/install exim. exim -d should show +Experimental_QUEUEFILE in the line "Support for:". --------------------------------------------------------------