base.m4 (DKIM_SIGN_P): Check that the sending domain is actually listed.

[exim-config] / base.m4

### -*-m4-*-
###
### Basic settings 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.

###--------------------------------------------------------------------------
### Global settings.

SECTION(global, priv)m4_dnl
admin_groups = CONF_admin_groups
trusted_groups = CONF_trusted_groups
prod_requires_admin = false

SECTION(global, logging)m4_dnl
log_file_path = : syslog
log_selector = \
	+smtp_confirmation \
	+tls_peerdn
log_timezone = true
syslog_duplication = false
syslog_timestamp = false

SECTION(global, daemon)m4_dnl
local_interfaces = <; CONF_interfaces
extra_local_interfaces = <; 0.0.0.0 ; ::0

SECTION(global, resource)m4_dnl
deliver_queue_load_max = 8
message_size_limit = 500M
queue_only_load = 12
smtp_accept_max = 16
smtp_accept_queue = 32
smtp_accept_reserve = 4
smtp_load_reserve = 10
smtp_reserve_hosts = +trusted

SECTION(global, policy)m4_dnl
host_lookup = *

SECTION(global, users)m4_dnl
gecos_name = $1
gecos_pattern = ([^,:]*)

SECTION(global, incoming)m4_dnl
rfc1413_hosts = *
rfc1413_query_timeout = 10s
received_header_text = Received: \
	${if def:sender_rcvhost \
	     {from $sender_rcvhost\n\t} \
	     {${if def:sender_ident \
		   {from ${quote_local_part:$sender_ident} }}}}\
	by $primary_hostname \
	(Exim $version_number)\
	${if def:tls_cipher {\n\t} { }}\
	${if def:received_protocol \
	     {with $received_protocol \
	      ${if def:tls_cipher {(cipher=$tls_cipher)}}}}\n\t\
	${if def:sender_address \
	     {(envelope-from $sender_address\
	      ${if def:authenticated_id \
		   {; auth=${quote_local_part:$authenticated_id}} \
		   {${if and {{def:authenticated_sender} \
			      {match_address{$authenticated_sender} \
					    {*@CONF_master_domain}}} \
			 {; auth=${quote_local_part:\
				    ${local_part:\
				      $authenticated_sender}}}}}})\n\t}}\
	id $message_exim_id\
	${if def:received_for {\n\tfor $received_for}}

SECTION(global, smtp)m4_dnl
smtp_return_error_details = true
accept_8bitmime = true
chunking_advertise_hosts =

SECTION(global, env)m4_dnl
keep_environment =

SECTION(global, process)m4_dnl
extract_addresses_remove_arguments = false
headers_charset = utf-8
qualify_domain = CONF_master_domain
untrusted_set_sender = *
local_from_check = false
local_sender_retain = true

SECTION(global, bounce)m4_dnl
delay_warning = 1h : 24h : 2d

SECTION(global, tls)m4_dnl
tls_certificate = CONF_certlist
tls_privatekey = CONF_sysconf_dir/server.key
tls_advertise_hosts = ${if exists {CONF_sysconf_dir/server.key} {*}{}}
tls_dhparam = CONF_ca_dir/dh-param-2048.pem
tls_require_ciphers = ${if or {{={$received_port}{CONF_submission_port}} \
			       {match_ip {$sender_host_address}{+trusted}}} \
			   {CONF_good_ciphers} \
			   {CONF_acceptable_ciphers}}
tls_verify_certificates = CONF_ca_dir/ca.cert
tls_verify_hosts = ${if eq{$acl_c_mode}{submission} {} {+allnets}}

DIVERT(null)
###--------------------------------------------------------------------------
### Access control lists.

SECTION(global, acl-after)
SECTION(global, acl)m4_dnl
acl_smtp_helo = helo
SECTION(acl, misc)m4_dnl
helo:
	## Don't worry if this is local submission.  MUAs won't necessarily
	## have a clear idea of their hostnames.  (For some reason.)
	accept	 condition = ${if eq{$acl_c_mode}{submission}}

	## Check that the caller's claimed identity is actually plausible.
	## This seems like it's a fairly effective filter on spamminess, but
	## it's too blunt a tool.  Rather than reject, add a warning header.
	## Only we can't do this the easy way, so save it up for use in MAIL.
	## Also, we're liable to get a subsequent HELO (e.g., after STARTTLS)
	## and we should only care about the most recent one.
	warn	 set acl_c_helo_warning = false
		!condition = \
			${if and {{match_ip {$sender_host_address} \
					    {<; 127.0.0.0/8 ; ::1}} \
				  {match_domain {$sender_helo_name} \
						{localhost : +thishost}}}}
		!condition = \
			${if exists {CONF_sysconf_dir/helo.conf} \
			     {${lookup {$sender_helo_name} \
				       partial0-lsearch \
				       {CONF_sysconf_dir/helo.conf} \
				       {${if match_ip \
					     {$sender_host_address} \
					     {<; $value}}}}}}
		!verify = helo
		 set acl_c_helo_warning = true

	accept

SECTION(global, acl)m4_dnl
acl_not_smtp_start = not_smtp_start
SECTION(acl, misc)m4_dnl
not_smtp_start:
	## Record the user's name.
	warn	 set acl_c_user = $sender_ident
		 set acl_m_user = $sender_ident

	## Done.
	accept

SECTION(global, acl)m4_dnl
acl_smtp_mail = mail
SECTION(acl, mail)m4_dnl
mail:

	## If we stashed a warning header about HELO from earlier, we should
	## add it now.  Only don't bother if the client has authenticated
	## successfully for submission (because we can't expect mobile
	## clients to be properly set up knowing their names), or it's one of
	## our own satellites (because they're either properly set up anyway,
	## or satellites using us as a smarthost).
	warn	 condition = $acl_c_helo_warning
		!condition = ${if eq{$acl_c_mode}{submission}}
		!hosts = +allnets
		 WARNING_HEADER(BADHELO,
				<:Client's HELO doesn't match its IP address.\n\t\
				  helo-name=$sender_helo_name \
				  address=$sender_host_address:>)

	## Always allow the empty sender, so that we can receive bounces.
	accept	 senders = :

	## Ensure that the sender looks valid.
	require	 acl = mail_check_sender

	## If this is directly from a client then hack on it for a while.
	warn	 condition = ${if eq{$acl_c_mode}{submission}}
		 control = submission/sender_retain

	## Insist that a local client connect through TLS.
	deny	 message = Hosts within CONF_master_domain must use TLS
		!condition = ${if eq{$acl_c_mode}{submission}}
		 hosts = +allnets
		!encrypted = *

	## Check that a submitted message's sender address is allowable.
	require	 acl = mail_check_auth

SECTION(acl, mail-tail)m4_dnl
	## And we're done.
	accept

SECTION(acl, misc)m4_dnl
mail_check_sender:

	## See whether there's a special exception for this sender domain.
	accept	 senders = ${LOOKUP_DOMAIN($sender_address_domain,
			     {KV(senders)})}

	## Ensure that the sender is routable.  This is important to prevent
	## undeliverable bounces.
	require	 message = Invalid sender; \
			($sender_verify_failure; $acl_verify_message)
		 verify = sender

	## We're good, then.
	accept

SECTION(global, acl)m4_dnl
acl_smtp_connect = connect
SECTION(acl, connect)m4_dnl
connect:
SECTION(acl, connect-tail)m4_dnl
	## Configure variables according to the submission mode.
	warn	 acl = check_submission

	## Done.
	accept

check_submission:
	## See whether this message needs hacking on.
	accept	!hosts = +thishost
		!condition = ${if ={$received_port}{CONF_submission_port}}
		 set acl_c_mode = relay

	## Remember to apply submission controls.
	warn	 set acl_c_mode = submission
		 control = no_enforce_sync

	## Done.
	accept

SECTION(global, acl)m4_dnl
acl_smtp_rcpt = rcpt
SECTION(acl, rcpt)m4_dnl
rcpt:

	## Reject if the client isn't allowed to relay and the recipient
	## isn't in one of our known domains.
	require	 message = Relaying not permitted
		 acl = check_relay

	## Ensure that the recipient is routable.
	require	 message = Invalid recipient \
			($recipient_verify_failure; $acl_verify_message)
		 verify = recipient

SECTION(acl, misc)m4_dnl
check_relay:
	## Accept either if the client is allowed to relay through us, or if
	## we're the correct place to send this mail.

	## Known clients and authenticated users are OK.
	accept	 hosts = CONF_relay_clients
	accept	 authenticated = *

	## Known domains are OK.
	accept	 domains = +public

	## Finally, domains in our table are OK, unless they say they aren't.
	accept	 domains = \
		 ${if exists{CONF_sysconf_dir/domains.conf} \
		     {partial0-lsearch;	CONF_sysconf_dir/domains.conf}}
		 condition = DOMKV(service, {$value}{true})

	## Nope, that's not allowed.
	deny

SECTION(acl, rcpt-tail)m4_dnl
	## Everything checks out OK: let this one go through.
	accept

SECTION(global, acl)m4_dnl
acl_smtp_data = data
SECTION(acl, data)m4_dnl
data:
	## Don't accept messages with overly-long lines.
	deny	 message = line length exceeds SMTP permitted maximum: \
			$max_received_linelength > 998
		 condition = ${if >{$max_received_linelength}{998}}

SECTION(acl, data-tail)m4_dnl
	accept

SECTION(global, acl)m4_dnl
acl_smtp_expn = expn_vrfy
acl_smtp_vrfy = expn_vrfy
SECTION(acl, misc)m4_dnl
expn_vrfy:
	accept	 hosts = +trusted
	deny	 message = Suck it and see

DIVERT(null)
###--------------------------------------------------------------------------
### Verification of sender address.

SECTION(acl, misc)m4_dnl
mail_check_auth:

	## If this isn't a submission then it doesn't need checking.
	accept	 condition = ${if !eq{$acl_c_mode}{submission}}

	## If the caller hasn't formally authenticated, but this is a
	## loopback connection, then we can trust identd to tell us the right
	## answer.  So we should stash the right name somewhere consistent.
	warn	 set acl_c_user = $authenticated_id
		 hosts = +thishost
		!authenticated = *
		 condition = ${if def:sender_ident}
		 set acl_c_user = $sender_ident

	## User must be authenticated by now.
	deny	 message = Sender not authenticated
		 condition = ${if !def:acl_c_user}

	## Set the per-message authentication flag, since we now know that
	## there's a sensible value.
	warn	 set acl_m_user = $acl_c_user

	## All done.
	accept

DIVERT(null)
###--------------------------------------------------------------------------
### Common options for forwarding routers.

## We're pretty permissive here.
m4_define(<:FILTER_BASE:>,
	<:driver = redirect
	modemask = 002
	check_owner = false
	check_group = false
	allow_filter = true
	allow_defer = true
	allow_fail = true
	forbid_blackhole = false
	check_ancestor = true:>)

## Common options for forwarding routers at verification time.
m4_define(<:FILTER_VERIFY:>,
	<:verify_only = true
	user = CONF_filter_user
	forbid_filter_dlfunc = true
	forbid_filter_logwrite = true
	forbid_filter_perl = true
	forbid_filter_readsocket = true
	forbid_filter_run = true
	file_transport = dummy
	directory_transport = dummy
	pipe_transport = dummy
	reply_transport = dummy:>)

## Transports for redirection filters.
m4_define(<:FILTER_TRANSPORTS:>,
	<:file_transport = mailbox
	directory_transport = maildir
	pipe_transport = pipe
	reply_transport = reply:>)

m4_define(<:FILTER_ROUTER:>,
<:$1_vrf:
	$2
	FILTER_VERIFY<::>$3
$1:
	$2
	verify = no
	FILTER_TRANSPORTS<::>$4:>)

DIVERT(null)
###--------------------------------------------------------------------------
### Common routers.

SECTION(routers, alias)m4_dnl
## Look up the local part in the address map.
alias:
	driver = redirect
	allow_fail = true
	allow_defer = true
	user = CONF_filter_user
	FILTER_TRANSPORTS
	local_parts = nwildlsearch; CONF_alias_file
	data = ${expand:$local_part_data}
SECTION(routers, alias-opts)m4_dnl

DIVERT(null)
###--------------------------------------------------------------------------
### Some standard transports.

m4_define(<:USER_DELIVERY:>,
	<:delivery_date_add = true
	envelope_to_add = true
	return_path_add = true:>)

m4_define(<:APPLY_HEADER_CHANGES:>,
	<:headers_add = m4_ifelse(<:$1:>, <::>,
		<:$acl_m_hdradd:>,
		<:${if def:acl_m_hdradd{$acl_m_hdradd\n}}\
		$1:>)
	headers_remove = m4_ifelse(<:$2:>, <::>,
		<:$acl_m_hdrrm:>,
		<:${if def:acl_m_hdrrm{$acl_m_hdrrm:}}\
		$2:>):>)

m4_define(<:DKIM_SIGN_P:>,
	<:and {{exists{CONF_sysconf_dir/dkim-sign.conf}} \
	       {!def:h_DKIM-Signature:} \
	       {!def:h_List-ID:} \
	       {or {{def:authenticated_id} \
		    {def:authenticated_sender}}} \
	       {bool {DKIM_KEYS_INSTANCE(<:{true}:>, <:{false}:>)}}}:>)

m4_define(<:DKIM_KEYS_INSTANCE:>,
	<:${lookup {${domain:$h_From:}} partial0-lsearch \
			{CONF_sysconf_dir/dkim-sign.conf} \
		_LOOKUP_ARGS(<:$1:>, <:$2:>)}:>)
m4_define(<:DKIM_KEYS_STATE:>, <:${lookup {$1} lsearch \
		{DKIM_KEYS_INSTANCE(<:{CONF_dkim_keys_dir/$value/active/dkim-keys.state}:>)} \
	_LOOKUP_ARGS(<:$2:>, <:$3:>, <:fail:>)}:>)
m4_define(<:DKIM_KEYS_INFO:>, <:DKIM_KEYS_STATE(<:params:>,
	<:{${if and {{>={$tod_epoch}{KV(t0)}} \
		    {<{$tod_epoch}{${eval:KV(t0) + KV(n)*KV(step)}}}} \
		{DKIM_KEYS_STATE(<:info.${eval:($tod_epoch - KV(t0))/KV(step)}:>,
			<:$1:>, <:$2:>)} \
		m4_ifelse(<:$2:>, <::>, <:fail:>, <:$2:>)}}:>,
	m4_ifelse(<:$2:>, <::>, <:fail:>, <:$2:>)):>)

m4_define(<:DKIM_SIGN:>,
	<:dkim_domain = \
		${if DKIM_SIGN_P \
			{DKIM_KEYS_INSTANCE({${domain:$h_From:}})}}
	dkim_selector = DKIM_KEYS_INFO(<:{KV(k)}:>)
	dkim_private_key = \
		DKIM_KEYS_INSTANCE(<:m4_dnl
			{CONF_dkim_keys_dir/$value/active/$dkim_selector.priv}:>)
	dkim_canon = relaxed
	dkim_strict = true
	## The following ridiculous stunt does two important jobs.  Firstly,
	## and more obviously, it arranges to include one more copy of each
	## header name than the message actually contains, thereby causing
	## the signature to fail if another header with the same name is
	## added.  And secondly, and far more subtly, it also trims the
	## spaces from the header names so that they're in the format that
	## the signing machinery secretly wants.
	dkim_sign_headers = \
		${sg {${map {CONF_dkim_headers : \
			     X-CONF_header_token-DKIM-Key-Publication} \
			    {$item${sg {${expand:\$h_$item:}\n} \
				       {((?:[^\n]+|\n\\s+)*)\n} \
				       {:$item}}}}} \
		     {::}{:}}
	headers_add = \
		${if DKIM_SIGN_P \
			{DKIM_KEYS_INFO(<:m4_dnl
				{X-CONF_header_token-DKIM-Key-Publication: \
					DKIM signature not suitable \
					as evidence after delivery;\n\t\
					DKIM private key KV(k) will be \
					published\n\t\
					at KV(u)\n\t\
					on or before KV(tpub)}:>)}}:>)


m4_define(<:SMTP_DELIVERY:>,
	<:## Prevent sending messages with overly long lines.  The use of
	## `message_size_limit' here is somewhat misleading.
	message_size_limit = ${if >{$max_received_linelength}{998}{1}{0}}:>)

SECTION(transports)m4_dnl
## A standard transport for remote delivery.  By default, try to do TLS, and
## don't worry too much if it's not very secure: the alternative is sending
## in plaintext anyway.  But all of this can be overridden from the
## `domains.conf' file.  Annoyingly, the `tls_dh_min_bits' setting isn't
## expanded before use, so we can't set it the obvious way.  Instead, encode
## it into the transport name.  This is very unpleasant, of course.
smtp:
	driver = smtp
	SMTP_DELIVERY
	APPLY_HEADER_CHANGES
	DKIM_SIGN
	tls_require_ciphers = CONF_acceptable_ciphers
	tls_dh_min_bits = 508
	tls_tempfail_tryclear = true

m4_define(<:SMTP_TRANS_DHBITS:>,
	<:driver = smtp
	SMTP_DELIVERY
	APPLY_HEADER_CHANGES
	DKIM_SIGN
	hosts_try_auth = *
	hosts_require_tls = DOMKV(tls-peer-ca, {*}{})
	hosts_require_auth = \
		${if bool {DOMKV(require-auth, {$value}{false})} {*}{}}
	tls_certificate = DOMKV(tls-certificate, {${expand:$value}}fail)
	tls_privatekey = DOMKV(tls-private-key, {${expand:$value}}fail)
	tls_verify_certificates = DOMKV(tls-peer-ca, {${expand:$value}}fail)
	tls_require_ciphers = \
		DOMKV(tls-ciphers,
		      {${extract {${expand:$value}} \
				 { good = CONF_good_ciphers \
				   any = CONF_acceptable_ciphers } \
				 {$value} \
				 {${expand:$value}}}} \
		      {CONF_acceptable_ciphers})
	tls_dh_min_bits = $1
	tls_tempfail_tryclear = true:>)m4_dnl
smtp_dhbits_512:
	SMTP_TRANS_DHBITS(508)
smtp_dhbits_768:
	SMTP_TRANS_DHBITS(764)
smtp_dhbits_1024:
	SMTP_TRANS_DHBITS(1020)
smtp_dhbits_2048:
	SMTP_TRANS_DHBITS(2044)

## Transport to a local SMTP server; use TLS and perform client
## authentication.
smtp_local:
	driver = smtp
	SMTP_DELIVERY
	APPLY_HEADER_CHANGES
	hosts_require_tls = *
	tls_certificate = CONF_sysconf_dir/client.certlist
	tls_privatekey = CONF_sysconf_dir/client.key
	tls_verify_certificates = CONF_ca_dir/ca.cert
	tls_require_ciphers = CONF_good_ciphers
	tls_dh_min_bits = 2046
	tls_tempfail_tryclear = false
	authenticated_sender_force = true
	authenticated_sender = \
		${if def:acl_m_user {$acl_m_user@CONF_master_domain} \
		     {${if def:authenticated_sender {$authenticated_sender} \
			   fail}}}

## A standard transport for local delivery.
deliver:
	driver = appendfile
	APPLY_HEADER_CHANGES
	file = /var/mail/$local_part
	group = mail
	mode = 0600
	mode_fail_narrower = false
	USER_DELIVERY

## Transports for user filters.
mailbox:
	driver = appendfile
	APPLY_HEADER_CHANGES
	initgroups = true
	USER_DELIVERY

maildir:
	driver = appendfile
	APPLY_HEADER_CHANGES
	maildir_format = true
	initgroups = true
	USER_DELIVERY

pipe:
	driver = pipe
	APPLY_HEADER_CHANGES
	path = ${if and {{def:home} {exists{$home/bin}}} {$home/bin:} {}}\
		/usr/local/bin:/usr/local/sbin:\
		/usr/bin:/usr/sbin:/bin:/sbin
	initgroups = true
	umask = 002
	return_fail_output = true
	log_output = true

## A special dummy transport for use during address verification.
dummy:
	driver = appendfile
	file = /dev/null

DIVERT(null)
###--------------------------------------------------------------------------
### Retry configuration.

SECTION(retry, default)m4_dnl
## Be persistent when sending to the site relay.  It ought to work, but
## particularly satellites such as laptops often encounter annoying temporary
## failures due to network unavailability, and the usual gradual policy can
## leave mail building up for no good reason.
CONF_smarthost				* \
	F,4d,15m

## Default.
*					* \
	F,2h,15m; G,16h,2h,1.5; F,4d,6h

DIVERT(null)
###----- That's all, folks --------------------------------------------------