X-Git-Url: https://git.exim.org/users/heiko/exim.git/blobdiff_plain/ff9663026d1a318d385730c4a2c3e85508b4b00b..5ce86c4f552071ad7408c40324d5211ab2a2da82:/doc/doc-txt/experimental-spec.txt diff --git a/doc/doc-txt/experimental-spec.txt b/doc/doc-txt/experimental-spec.txt index 3beab4b9c..47cd93f3d 100644 --- a/doc/doc-txt/experimental-spec.txt +++ b/doc/doc-txt/experimental-spec.txt @@ -294,9 +294,9 @@ These four steps are explained in more details below. SRS (Sender Rewriting Scheme) Support (using libsrs_alt) -------------------------------------------------------------- -See also below, for an alternative native support implementation. +See also the main docs, for an alternative native support implementation. -Exim currently includes SRS support via Miles Wilton's +Exim can be built with SRS support using Miles Wilton's libsrs_alt library. The current version of the supported library is 0.5, there are reports of 1.0 working. @@ -309,10 +309,14 @@ https://opsec.eu/src/srs/ Unpack the tarball, then refer to MTAs/README.EXIM to proceed. You need to set -EXPERIMENTAL_SRS=yes +EXPERIMENTAL_SRS_ALT=yes in your Local/Makefile. +The built-in support, included by SUPPORT_SRS, +shuold *not* be enabled if you wish to use the libsrs_alt +version. + The following main-section options become available: srs_config string srs_hashlength int @@ -344,76 +348,6 @@ For configuration information see https://github.com/Exim/exim/wiki/SRS . -SRS (Sender Rewriting Scheme) Support (native) --------------------------------------------------------------- -This is less full-featured than the libsrs_alt version above. - -The Exim build needs to be done with this in Local/Makefile: -EXPERIMENTAL_SRS_NATIVE=yes - -The following are provided: -- an expansion item "srs_encode" - This takes three arguments: - - a site SRS secret - - the return_path - - the pre-forwarding domain - -- an expansion condition "inbound_srs" - This takes two arguments: the local_part to check, and a site SRS secret. - If the secret is zero-length, only the pattern of the local_part is checked. - The $srs_recipient variable is set as a side-effect. - -- an expansion variable $srs_recipient - This gets the original return_path encoded in the SRS'd local_part - -- predefined macros _HAVE_SRS and _HAVE_NATIVE_SRS - -Sample usage: - - #macro - SRS_SECRET = - - #routers - - outbound: - driver = dnslookup - # if outbound, and forwarding has been done, use an alternate transport - domains = ! +my_domains - transport = ${if eq {$local_part@$domain} \ - {$original_local_part@$original_domain} \ - {remote_smtp} {remote_forwarded_smtp}} - - inbound_srs: - driver = redirect - senders = : - domains = +my_domains - # detect inbound bounces which are SRS'd, and decode them - condition = ${if inbound_srs {$local_part} {SRS_SECRET}} - data = $srs_recipient - - inbound_srs_failure: - driver = redirect - senders = : - domains = +my_domains - # detect inbound bounces which look SRS'd but are invalid - condition = ${if inbound_srs {$local_part} {}} - allow_fail - data = :fail: Invalid SRS recipient address - - #... further routers here - - - # transport; should look like the non-forward outbound - # one, plus the max_rcpt and return_path options - remote_forwarded_smtp: - driver = smtp - # modify the envelope from, for mails that we forward - max_rcpt = 1 - return_path = ${srs_encode {SRS_SECRET} {$return_path} {$original_domain}} - - - - DCC Support -------------------------------------------------------------- Distributed Checksum Clearinghouse; http://www.rhyolite.com/dcc/ @@ -532,52 +466,6 @@ Rationale: Note that non-RFC-documented field names and data types are used. -LMDB Lookup support -------------------- -LMDB is an ultra-fast, ultra-compact, crash-proof key-value embedded data store. -It is modeled loosely on the BerkeleyDB API. You should read about the feature -set as well as operation modes at https://symas.com/products/lightning-memory-mapped-database/ - -LMDB single key lookup support is provided by linking to the LMDB C library. -The current implementation does not support writing to the LMDB database. - -Visit https://github.com/LMDB/lmdb to download the library or find it in your -operating systems package repository. - -If building from source, this description assumes that headers will be in -/usr/local/include, and that the libraries are in /usr/local/lib. - -1. In order to build exim with LMDB lookup support add or uncomment - -EXPERIMENTAL_LMDB=yes - -to your Local/Makefile. (Re-)build/install exim. exim -d should show -Experimental_LMDB in the line "Support for:". - -EXPERIMENTAL_LMDB=yes -LDFLAGS += -llmdb -# CFLAGS += -I/usr/local/include -# LDFLAGS += -L/usr/local/lib - -The first line sets the feature to include the correct code, and -the second line says to link the LMDB libraries into the -exim binary. The commented out lines should be uncommented if you -built LMDB from source and installed in the default location. -Adjust the paths if you installed them elsewhere, but you do not -need to uncomment them if an rpm (or you) installed them in the -package controlled locations (/usr/include and /usr/lib). - -2. Create your LMDB files, you can use the mdb_load utility which is -part of the LMDB distribution our your favourite language bindings. - -3. Add the single key lookups to your exim.conf file, example lookups -are below. - -${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. @@ -750,67 +638,8 @@ used via the transport in question. - -TLS Session Resumption ----------------------- -TLS Session Resumption for TLS 1.2 and TLS 1.3 connections can be used (defined -in RFC 5077 for 1.2). The support for this can be included by building with -EXPERIMENTAL_TLS_RESUME defined. This requires GnuTLS 3.6.3 or OpenSSL 1.1.1 -(or later). - -Session resumption (this is the "stateless" variant) involves the server sending -a "session ticket" to the client on one connection, which can be stored by the -client and used for a later session. The ticket contains sufficient state for -the server to reconstruct the TLS session, avoiding some expensive crypto -calculation and one full packet roundtrip time. - -Operational cost/benefit: - The extra data being transmitted costs a minor amount, and the client has - extra costs in storing and retrieving the data. - - In the Exim/Gnutls implementation the extra cost on an initial connection - which is TLS1.2 over a loopback path is about 6ms on 2017-laptop class hardware. - The saved cost on a subsequent connection is about 4ms; three or more - connections become a net win. On longer network paths, two or more - connections will have an average lower startup time thanks to the one - saved packet roundtrip. TLS1.3 will save the crypto cpu costs but not any - packet roundtrips. - - Since a new hints DB is used, the hints DB maintenance should be updated - to additionally handle "tls". - -Security aspects: - The session ticket is encrypted, but is obviously an additional security - vulnarability surface. An attacker able to decrypt it would have access - all connections using the resumed session. - The session ticket encryption key is not committed to storage by the server - and is rotated regularly (OpenSSL: 1hr, and one previous key is used for - overlap; GnuTLS 6hr but does not specify any overlap). - Tickets have limited lifetime (2hr, and new ones issued after 1hr under - OpenSSL. GnuTLS 2hr, appears to not do overlap). - - There is a question-mark over the security of the Diffie-Helman parameters - used for session negotiation. TBD. q-value; cf bug 1895 - -Observability: - New log_selector "tls_resumption", appends an asterisk to the tls_cipher "X=" - element. - - Variables $tls_{in,out}_resumption have bits 0-4 indicating respectively - support built, client requested ticket, client offered session, - server issued ticket, resume used. A suitable decode list is provided - in the builtin macro _RESUME_DECODE for ${listextract {}{}}. - -Issues: - In a resumed session: - $tls_{in,out}_cipher will have values different to the original (under GnuTLS) - $tls_{in,out}_ocsp will be "not requested" or "no response", and - hosts_require_ocsp will fail - - - Dovecot authenticator via inet socket ------------------------------------- +-------------------------------------------------------------- If Dovecot is configured similar to :- service auth { @@ -837,29 +666,19 @@ and a whitespace-separated port number must be given. -Twophase queue run fast ramp ----------------------------- -To include this feature, add to Local/Makefile: - EXPERIMENTAL_QUEUE_RAMP=yes - -If the (added for this feature) main-section option "queue_fast_ramp" (boolean) -is set, and a two-phase ("-qq") queue run finds, during the first phase, a -suitably large number of message routed for a given host - then (subject to -the usual queue-runner resource limits) delivery for that host is initiated -immediately, overlapping with the remainder of the first phase. - -This is incompatible with queue_run_in_order. - -The result should be a faster startup of deliveries when a large queue is -present and reasonable numbers of messages are routed to common hosts; this -could be a smarthost case, or delivery onto the Internet where a large proportion -of recipients hapen to be on a Gorilla-sized provider. -As usual, the presence of a configuration option is associated with a -predefined macro, making it possible to write portable configurations. -For this one, the macro is _OPT_MAIN_QUEUE_FAST_RAMP. +Logging protocol unusual states +--------------------------------------------------------------- +An extra log_selector, "protocol_detail" has been added in the default build. +The name may change in future, hence the Experimenal status. +Currrently the only effect is to enable logging, under TLS, +of a TCP RST received directly after a QUIT (in server mode). +Outlook is consistently doing this; not waiting for the SMTP response +to its QUIT, not properly closing the TLS session and not properly closing +the TCP connection. Previously this resulted is an error from SSL_write +being logged. -------------------------------------------------------------- End of file