[exim-config] / spam.m4

### -*-m4-*-
###
### Spam filtering for distorted.org.uk Exim configuration
###
### (c) 2012 Mark Wooding
###

###----- Licensing notice ---------------------------------------------------
###
### This program is free software; you can redistribute it and/or modify
### it under the terms of the GNU General Public License as published by
### the Free Software Foundation; either version 2 of the License, or
### (at your option) any later version.
###
### This program is distributed in the hope that it will be useful,
### but WITHOUT ANY WARRANTY; without even the implied warranty of
### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
### GNU General Public License for more details.
###
### You should have received a copy of the GNU General Public License
### along with this program; if not, write to the Free Software Foundation,
### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

DIVERT(null)
###--------------------------------------------------------------------------
### Spam filtering.

## The Exim documentation tells lies.
##
## : *${run{*<_command_>* *<_args_>*}{*<_string1_>*}{*<_string2_>*}}*
## :     The command and its arguments are first expanded separately, [...]
##
## They aren't.  The whole command-and-args are expanded together, and then
## split at unquoted spaces.  This unpleasant hack sorts out the mess.
m4_define(<:SHQUOTE:>, <:"${rxquote:$1}":>)

## Utilities for collecting spam limits.
m4_define(<:SPAMLIMIT_CHECK:>,
	<:${if match{$1}{\N^-?[0-9]+$\N} {spam_limit=$1} {}}:>)

m4_define(<:SPAMLIMIT_ROUTER:>,
<:$1:
	driver = redirect
	data = :unknown:
	verify_only = true
	condition = ${if !eq{$acl_c_mode}{submission}}
	condition = ${extract{spam_limit}{$address_data}{false}{true}}:>)

m4_define(<:SPAMLIMIT_SET:>,
	<:address_data = \
		${if def:address_data {$address_data}{}} \
		$1:>)

m4_define(<:SPAMLIMIT_LOOKUP:>,
	<:condition = ${if exists{$1}}
	SPAMLIMIT_SET(<:${lookup {$2$3$4@$5/$6} nwildlsearch {$1} \
			       {SPAMLIMIT_CHECK($value)}}:>):>)

m4_define(<:SPAMLIMIT_USERV:>,
	<:SPAMLIMIT_SET(<:${run {/usr/bin/timeout 5s \
					userv CONF_userv_opts \
					SHQUOTE($1) exim-spam-limit \
					SHQUOTE($6) SHQUOTE($2) SHQUOTE($3) \
					SHQUOTE($4) SHQUOTE(@$5)} \
				{SPAMLIMIT_CHECK($value)}}:>):>)

SECTION(global, policy)m4_dnl
spamd_address = CONF_spamd_address CONF_spamd_port

SECTION(acl, rcpt-hooks)m4_dnl
	## Do per-recipient spam-filter processing.
	require	 acl = rcpt_spam

SECTION(acl, misc)m4_dnl
skip_spam_check:

	## If the client is trusted, or this is a new submission, don't
	## bother with any of this.  We will have verified the sender
	## fairly aggressively before granting this level of trust.
	accept	 hosts = +trusted
	accept	 condition = ${if eq{$acl_c_mode}{submission}}

	## If all domains have disabled spam checking then don't check.
	accept	!condition = $acl_c_spam_check_domain

	## Otherwise we should check.
	deny

rcpt_spam:

	## If this is a virtual domain, and it says `spam-check=no', then we
	## shouldn't check spam.  But we can't check domains at DATA time, so
	## instead we must track whether all recipients have disabled
	## checking.
	warn	!domains = ${if exists{CONF_sysconf_dir/domains.conf} \
			 {partial0-lsearch; CONF_sysconf_dir/domains.conf} \
			 {}}
		 set acl_c_spam_check_domain = true
	warn	!condition = $acl_c_spam_check_domain
		 condition = DOMKV(spam-check, {${expand:$value}}{true})
		 set acl_c_spam_check_domain = true

	## See if we should do this check.
	accept	 acl = skip_spam_check

	## Always accept mail to `postmaster'.  Currently this is not
	## negotiable; maybe a tweak can be added to `domains.conf' if
	## necessary.
	accept	 local_parts = postmaster

	## Collect the user's spam threshold from the `address_data'
	## variable, where it was left by the `fetch_spam_limit' router
	## during recipient verification.  (This just saves duplicating this
	## enormous expression.)
	warn	 set acl_m_this_spam_limit = \
			${sg {${extract {spam_limit} \
					{${if def:address_data \
					      {$address_data}{}}} \
					{$value}{nil}}} \
			     {^(|.*\\D.*)\$}{CONF_spam_max}}

	## If there's a spam limit already established, and it's different
	## from this user's limit, then the sender will have to try this user
	## again later.
	defer	!hosts = +trusted
		 message = "You'd better try this one later"
		 condition = ${if def:acl_m_spam_limit {true}{false}}
		 condition = ${if ={$acl_m_spam_limit} \
				   {$acl_m_this_spam_limit} \
				  {false}{true}}

	## There's no limit set yet, or the user's limit is the same as the
	## existing one, or the client's local and we're not checking for
	## spam anyway.  Whichever way, it's safe to set it now.
	warn	 set acl_m_spam_limit = $acl_m_this_spam_limit

	## All done.
	accept

SECTION(acl, data-spam)m4_dnl
	## Do spam checking.
	require	 acl = data_spam

SECTION(acl, misc)m4_dnl
data_spam:

	## See if we should do this check.
	accept	 acl = skip_spam_check

	## Check header validity.
	require	 verify = header_syntax

	## Check the message for spam, comparing to the configured limit.
	deny	 spam = exim:true
		 message = Tinned meat product detected ($spam_score)
		 condition = ${if >{$spam_score_int}{$acl_m_spam_limit} \
				  {true}{false}}

	## Insert headers from the spam check now that we've decided to
	## accept the message.
	warn

		 ## Convert the limit (currently 10x fixed point) into a
		 ## decimal for presentation.
		 set acl_m_spam_limit_presentation = \
			${sg{$acl_m_spam_limit}{\N(\d)$\N}{.\$1}}

		 ## Convert the report into something less obnoxious.  Plain
		 ## old SpamAssassin has an `X-Spam-Status' header which
		 ## lists the matched rules and provides some other basic
		 ## information.  Try to extract something similar from the
		 ## report.
		 ##
		 ## This is rather fiddly.

		 ## Firstly, escape angle brackets, because we'll be using
		 ## them for our own purposes.
		 set acl_m_spam_tests = ${sg{$spam_report}{([!<>])}{!\$1}}

		 ## Trim off the blurb paragraph and the preview.  The rest
		 ## should be fairly well behaved.  Wrap double angle-
		 ## brackets around the remainder; these can't appear in the
		 ## body because we escaped them all earlier.
		 set acl_m_spam_tests = \
			${sg{$acl_m_spam_tests} \
			    {\N^(?s).*\n Content analysis details:(.*)$\N} \
			    {<<\$1>>}}

		 ## Extract the information about the matching rules and
		 ## their scores.  Leave `<<...>>' around everything else.
		 set acl_m_spam_tests = \
			${sg{$acl_m_spam_tests} \
			    {\N(?s)\n\s*(-?[\d.]+)\s+([-\w]+)\s\N} \
			    {>>\$2:\$1,<<}}

		 ## Strip everything still in `<<...>>' pairs, including any
		 ## escaped characters inside.
		 set acl_m_spam_tests = \
			${sg{$acl_m_spam_tests}{\N(?s)<<([^!>]+|!.)*>>\N}{}}

		 ## Trim off a trailing comma.
		 set acl_m_spam_tests = ${sg{$acl_m_spam_tests}{,\s*\$}{}}

		 ## Undo the escaping.
		 set acl_m_spam_tests = ${sg{$acl_m_spam_tests}{!(.)}{\$1}}

		 ## Insert the headers.
		 add_header = X-Distorted-SpamAssassin-Score: \
			$spam_score/$acl_m_spam_limit_presentation \
			($spam_bar)
		 add_header = X-Distorted-SpamAssassin-Status: \
			score=$spam_score, \
			limit=$acl_m_spam_limit_presentation, \n\t\
			tests=$acl_m_spam_tests

	## We're good.
	accept

DIVERT(null)
###----- That's all, folks --------------------------------------------------
Commit	Line	Data
185b5456 MW	1	### --m4--
	2	###
	3	### Spam filtering for distorted.org.uk Exim configuration
	4	###
	5	### (c) 2012 Mark Wooding
	6	###
	7
	8	###----- Licensing notice ---------------------------------------------------
	9	###
	10	### This program is free software; you can redistribute it and/or modify
	11	### it under the terms of the GNU General Public License as published by
	12	### the Free Software Foundation; either version 2 of the License, or
	13	### (at your option) any later version.
	14	###
	15	### This program is distributed in the hope that it will be useful,
	16	### but WITHOUT ANY WARRANTY; without even the implied warranty of
	17	### MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
	18	### GNU General Public License for more details.
	19	###
	20	### You should have received a copy of the GNU General Public License
	21	### along with this program; if not, write to the Free Software Foundation,
	22	### Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.
	23
	24	DIVERT(null)
	25	###--------------------------------------------------------------------------
	26	### Spam filtering.
	27
953ae20e MW	28	## The Exim documentation tells lies.
	29	##
	30	## : ${run{<_command_>* <_args_>}{<_string1_>}{<_string2_>}}*
	31	## : The command and its arguments are first expanded separately, [...]
	32	##
	33	## They aren't. The whole command-and-args are expanded together, and then
	34	## split at unquoted spaces. This unpleasant hack sorts out the mess.
	35	m4_define(<:SHQUOTE:>, <:"${rxquote:$1}":>)
	36
02af00e7 MW	37	## Utilities for collecting spam limits.
	38	m4_define(<:SPAMLIMIT_CHECK:>,
	39	<:${if match{$1}{\N^-?[0-9]+$\N} {spam_limit=$1} {}}:>)
	40
	41	m4_define(<:SPAMLIMIT_ROUTER:>,
	42	<:$1:
	43	driver = redirect
	44	data = :unknown:
	45	verify_only = true
	46	condition = ${if !eq{$acl_c_mode}{submission}}
	47	condition = ${extract{spam_limit}{$address_data}{false}{true}}:>)
	48
	49	m4_define(<:SPAMLIMIT_SET:>,
	50	<:address_data = \
	51	${if def:address_data {$address_data}{}} \
	52	$1:>)
	53
	54	m4_define(<:SPAMLIMIT_LOOKUP:>,
	55	<:condition = ${if exists{$1}}
	56	SPAMLIMIT_SET(<:${lookup {$2$3$4@$5/$6} nwildlsearch {$1} \
	57	{SPAMLIMIT_CHECK($value)}}:>):>)
	58
	59	m4_define(<:SPAMLIMIT_USERV:>,
	60	<:SPAMLIMIT_SET(<:${run {/usr/bin/timeout 5s \
	61	userv CONF_userv_opts \
	62	SHQUOTE($1) exim-spam-limit \
	63	SHQUOTE($6) SHQUOTE($2) SHQUOTE($3) \
	64	SHQUOTE($4) SHQUOTE(@$5)} \
	65	{SPAMLIMIT_CHECK($value)}}:>):>)
	66
185b5456 MW	67	SECTION(global, policy)m4_dnl
	68	spamd_address = CONF_spamd_address CONF_spamd_port
	69
185b5456 MW	70	SECTION(acl, rcpt-hooks)m4_dnl
	71	## Do per-recipient spam-filter processing.
	72	require acl = rcpt_spam
	73
	74	SECTION(acl, misc)m4_dnl
b8b0f13c	75	skip_spam_check:
185b5456	76
b8b0f13c MW	77	## If the client is trusted, or this is a new submission, don't
	78	## bother with any of this. We will have verified the sender
	79	## fairly aggressively before granting this level of trust.
185b5456	80	accept hosts = +trusted
b8b0f13c MW	81	accept condition = ${if eq{$acl_c_mode}{submission}}
b8b0f13c MW	82
87afdfcd MW	83	## If all domains have disabled spam checking then don't check.
87afdfcd MW	84	accept !condition = $acl_c_spam_check_domain
48507a38	85
b8b0f13c MW	86	## Otherwise we should check.
	87	deny
	88
	89	rcpt_spam:
	90
87afdfcd MW	91	## If this is a virtual domain, and it says `spam-check=no', then we
	92	## shouldn't check spam. But we can't check domains at DATA time, so
	93	## instead we must track whether all recipients have disabled
	94	## checking.
	95	warn !domains = ${if exists{CONF_sysconf_dir/domains.conf} \
	96	{partial0-lsearch; CONF_sysconf_dir/domains.conf} \
	97	{}}
	98	set acl_c_spam_check_domain = true
	99	warn !condition = $acl_c_spam_check_domain
	100	condition = DOMKV(spam-check, {${expand:$value}}{true})
	101	set acl_c_spam_check_domain = true
	102
b8b0f13c MW	103	## See if we should do this check.
b8b0f13c MW	104	accept acl = skip_spam_check
185b5456	105
aa935c91 MW	106	## Always accept mail to `postmaster'. Currently this is not
	107	## negotiable; maybe a tweak can be added to `domains.conf' if
	108	## necessary.
	109	accept local_parts = postmaster
	110
185b5456 MW	111	## Collect the user's spam threshold from the `address_data'
	112	## variable, where it was left by the `fetch_spam_limit' router
	113	## during recipient verification. (This just saves duplicating this
	114	## enormous expression.)
	115	warn set acl_m_this_spam_limit = \
	116	${sg {${extract {spam_limit} \
	117	{${if def:address_data \
	118	{$address_data}{}}} \
	119	{$value}{nil}}} \
	120	{^(\|.\\D.)\$}{CONF_spam_max}}
	121
	122	## If there's a spam limit already established, and it's different
	123	## from this user's limit, then the sender will have to try this user
	124	## again later.
	125	defer !hosts = +trusted
	126	message = "You'd better try this one later"
	127	condition = ${if def:acl_m_spam_limit {true}{false}}
	128	condition = ${if ={$acl_m_spam_limit} \
	129	{$acl_m_this_spam_limit} \
	130	{false}{true}}
	131
	132	## There's no limit set yet, or the user's limit is the same as the
	133	## existing one, or the client's local and we're not checking for
	134	## spam anyway. Whichever way, it's safe to set it now.
	135	warn set acl_m_spam_limit = $acl_m_this_spam_limit
	136
	137	## All done.
	138	accept
	139
	140	SECTION(acl, data-spam)m4_dnl
	141	## Do spam checking.
	142	require acl = data_spam
	143
	144	SECTION(acl, misc)m4_dnl
	145	data_spam:
	146
b8b0f13c MW	147	## See if we should do this check.
b8b0f13c MW	148	accept acl = skip_spam_check
185b5456	149
09ca3919 MW	150	## Check header validity.
	151	require verify = header_syntax
	152
185b5456 MW	153	## Check the message for spam, comparing to the configured limit.
	154	deny spam = exim:true
	155	message = Tinned meat product detected ($spam_score)
	156	condition = ${if >{$spam_score_int}{$acl_m_spam_limit} \
	157	{true}{false}}
	158
	159	## Insert headers from the spam check now that we've decided to
	160	## accept the message.
	161	warn
a882a548	162
185b5456 MW	163	## Convert the limit (currently 10x fixed point) into a
	164	## decimal for presentation.
	165	set acl_m_spam_limit_presentation = \
	166	${sg{$acl_m_spam_limit}{\N(\d)$\N}{.\$1}}
	167
	168	## Convert the report into something less obnoxious. Plain
	169	## old SpamAssassin has an `X-Spam-Status' header which
	170	## lists the matched rules and provides some other basic
	171	## information. Try to extract something similar from the
	172	## report.
	173	##
	174	## This is rather fiddly.
	175
	176	## Firstly, escape angle brackets, because we'll be using
	177	## them for our own purposes.
	178	set acl_m_spam_tests = ${sg{$spam_report}{([!<>])}{!\$1}}
	179
	180	## Trim off the blurb paragraph and the preview. The rest
	181	## should be fairly well behaved. Wrap double angle-
	182	## brackets around the remainder; these can't appear in the
	183	## body because we escaped them all earlier.
	184	set acl_m_spam_tests = \
	185	${sg{$acl_m_spam_tests} \
	186	{\N^(?s).\n Content analysis details:(.)$\N} \
	187	{<<\$1>>}}
	188
	189	## Extract the information about the matching rules and
	190	## their scores. Leave `<<...>>' around everything else.
	191	set acl_m_spam_tests = \
	192	${sg{$acl_m_spam_tests} \
4ff4d304	193	{\N(?s)\n\s*(-?[\d.]+)\s+([-\w]+)\s\N} \
185b5456 MW	194	{>>\$2:\$1,<<}}
	195
	196	## Strip everything still in `<<...>>' pairs, including any
	197	## escaped characters inside.
	198	set acl_m_spam_tests = \
	199	${sg{$acl_m_spam_tests}{\N(?s)<<([^!>]+\|!.)*>>\N}{}}
	200
	201	## Trim off a trailing comma.
	202	set acl_m_spam_tests = ${sg{$acl_m_spam_tests}{,\s*\$}{}}
	203
	204	## Undo the escaping.
	205	set acl_m_spam_tests = ${sg{$acl_m_spam_tests}{!(.)}{\$1}}
	206
	207	## Insert the headers.
33abb520	208	add_header = X-Distorted-SpamAssassin-Score: \
185b5456 MW	209	$spam_score/$acl_m_spam_limit_presentation \
185b5456 MW	210	($spam_bar)
33abb520	211	add_header = X-Distorted-SpamAssassin-Status: \
185b5456 MW	212	score=$spam_score, \
	213	limit=$acl_m_spam_limit_presentation, \n\t\
	214	tests=$acl_m_spam_tests
	215
185b5456 MW	216	## We're good.
	217	accept
	218
	219	DIVERT(null)
	220	###----- That's all, folks --------------------------------------------------