### -*-m4-*-
###
### Client authentication 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.

###--------------------------------------------------------------------------
### Authenticators.

m4_define(<:CHECK_PASSWD:>,
<:${lookup {$1} lsearch {CONF_sysconf_dir/passwd} \
	   {${if crypteq {$2} {$value}}} \
	   {false}}:>)

m4_define(<:ALLOW_PLAINTEXT_AUTH_P:>,
<:or {{match_ip {$sender_host_address}{+thishost}} \
      {and {{def:tls_cipher} {eq{$acl_c_mode}{submission}}}}}:>)

m4_define(<:CLIENT_SECRETS_FILE:>, <:CONF_sysconf_dir/client-secrets:>)

m4_define(<:CLIENT_SECRET_GET:>,
<:${if exists {CLIENT_SECRETS_FILE} \
       {${lookup {$domain} partial0-lsearch {CLIENT_SECRETS_FILE} \
	    {${extract {$1}{$value}$2$3}} \
	    {${lookup {$host} partial0-lsearch {CLIENT_SECRETS_FILE} \
		      {${extract {$1}{$value}$2$3}} $3}}}} \
       $3}:>)

m4_define(<:CLIENT_SECRET_EXISTSP:>,
<:CLIENT_SECRET_GET($1, {true}, {false}):>)

m4_define(<:CLIENT_SECRET:>,
<:CLIENT_SECRET_GET($1, {${expand:$value}}, fail):>)

SECTION(auth)m4_dnl
plain:
	driver = plaintext
	public_name = PLAIN
	server_advertise_condition = ${if ALLOW_PLAINTEXT_AUTH_P}
	server_prompts = :
	server_condition = CHECK_PASSWD($auth2, $auth3)
	server_set_id = $auth2
	client_condition = CLIENT_SECRET_EXISTSP(plain)
	client_send = <; CLIENT_SECRET(plain)

login:
	driver = plaintext
	public_name = LOGIN
	server_advertise_condition = ${if ALLOW_PLAINTEXT_AUTH_P}
	server_prompts = <; Username: ; Password:
	server_condition = CHECK_PASSWD($auth1, $auth2)
	server_set_id = $auth1
	client_condition = CLIENT_SECRET_EXISTSP(login-passwd)
	client_send = <; \
		; CLIENT_SECRET(login-name) \
		; CLIENT_SECRET(login-passwd)

cram_md5:
	driver = cram_md5
	public_name = CRAM-MD5
	client_condition = CLIENT_SECRET_EXISTSP(cram-md5-secret)
	client_name = CLIENT_SECRET(cram-md5-name)
	client_secret = CLIENT_SECRET(cram-md5-secret)

DIVERT(null)
###--------------------------------------------------------------------------
### Dealing with `AUTH' parameters and relaying.

SECTION(global, acl)m4_dnl
acl_smtp_mailauth = mailauth
SECTION(acl, misc)m4_dnl
## Check the `AUTH=...' parameter to a `MAIL' command.
mailauth:
	## If the client has authenticated using TLS then we're OK.  The
	## sender was presumably checked upstream, and we can believe that
	## the name has been transmitted honestly.
	accept	  condition = ${if def:tls_peerdn}

	## If this is submission, and the client has authenticated, then we
	## check that the name matches the user.
	accept	  condition = ${if eq {$authenticated_sender} \
				      {$authenticated_id@CONF_master_domain}}

	## Otherwise we can't tell who really sent it.
	deny	  message = Authenticated user not authoritative for claimed sender.

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