# Sample Configuration for Experimental Return Path Rewriting in Exim 3
# Copyright 2004, Daniel Roethlisberger <daniel@roe.ch>
#
# 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
# copy of the GNU General Public License is distributed with exim itself

##############################################################################
### Version 1 of my return path rewriting scheme
### Obsoleted by http://www.roe.ch/spam/rpr-exim3-roe-02.txt
### See http://www.roe.ch/spam/return-path-rewriting.xml
# Q()          : Quoting s/([=%#_])/_\1/g
# H()          : Hash (MD5)
# local_user   : local part of original recipient address,
#                or full recipient (s/@/%/) address if nonlocal
# local_domain : domain of original recipient (which is a local domain)
# old_from     : original return path / envelope sender (s/@/#/)
# secret       : local RPR secret
# timestamp    = strftime(%Y%m%d%H%M)
# authdata     = $secret + $timestamp + '=' + Q($old_from) + '=' + $local_user
# new_from     = 'bouce-' + H($authdata) + '-' + $authdata +
#                '@' + $local_domain

##############################################################################
### in startup.pl

use POSIX qw(mktime);

### [...]

sub rpr_verify_date
{
    my ($y, $m, $d, $ru, $rd) = @_;

    # 1296000 = 15 * 24 * 60 * 60 = 15d
    if(time() &lt;= 1296000 + mktime(0, 0, 0, $d, $m-1, $y-1900))
    {
        return $ru.'@'.$rd;
    }
    else
    {
        return 'postmaster@'.Exim::expand_string('$domain');
    }
}
##############################################################################

##############################################################################
### in exim.conf

### somewhere near the top - ADJUST THIS !!!
# the secret
RPR_SECRET = yoursecret
RPR_URL = http://www.roe.ch/spam/return-path-rewriting.xml
# domain lists or file lookups or the like -- gets used in "senders =" below
# to decide whether the router is run on a foreign address or not.
# You may want to edit the senders line below instead of adding these macros.
LOCAL_DOMAINS = your : local : domains
VIRTUAL_DOMAINS = your : virtual : domains

### [...]

### in the directors section, preferrably at the top
# Return Path Rewriting
# rewrite incoming RPR bounces to their real destinations

rpr_return:
  driver = smartuser
  prefix = bounce-
  condition = ${if and {{eq {$sender_address}{}}\
                        {match {$local_part}{^([0-9a-f]\{32\})-(\\d\{8\}(?:\\d\{4\})?=(?:.*[^_])?(?:_[_#])*#[^=#]+=.+)\$}}\
                        {eq {${md5:RPR_SECRET-$2@$domain}}{$1}}\
                       } {1}{0}}
  new_address = ${if match {$local_part}{^[0-9a-f]\{32\}-(\\d\{4\})(\\d\{2\})(\\d\{2\})(?:\\d\{4\})?=((?:.*[^_])?(?:_[_#])*)#([^=#]+)=(.+)\$}{\
                  ${sg {${perl{rpr_verify_date}{$1}{$2}{$3}{$4}{$5}}} {_([_=#%])}{\$1}}\
                }{"postmaster@$domain"}}
  headers_add = "X-RPR-Return: DSN routed to destination via $primary_hostname\n\
                 \tSee RPR_URL"

rpr_error_checksum:
  driver = smartuser
  prefix = bounce-
  condition = ${if and {{eq {$sender_address}{}}\
                        {match {$local_part}{^([0-9a-f]\{32\})-(\\d\{8\}(?:\\d\{4\})?=(?:.*[^_])?(?:_[_#])*#[^=#]+=.+)\$}}\
                       } {1}{0}}
  new_address = "postmaster@$domain"
  headers_add = "X-RPR-Alert: Checksum mismatch!"

rpr_error_nodsn:
  driver = smartuser
  prefix = bounce-
  condition = ${if match {$local_part}{^([0-9a-f]\{32\})-(\\d\{8\}(?:\\d\{4\})?=(?:.*[^_])?(?:_[_#])*#[^=#]+=.+)\$} {1}{0}}
  new_address = "postmaster@$domain"
  headers_add = "X-RPR-Alert: Not a DSN (non-empty return-path)!"

### [...]

### in the routers section, preferrably at the top
# Return Path Rewriting
# rewrite outgoing mail with foreign return-path to local RPR scheme

rpr_lookup_mx:
  senders = !LOCAL_DOMAINS:!VIRTUAL_DOMAINS
  driver = lookuphost
  transport = remote_smtp
  ignore_target_hosts = 127.0.0.0/8
  condition = ${if and {{!eq {$sender_address}{}}\
                        {!match {$h_X-RPR-Return:}{$primary_hostname}}\
                       }{1}{0}}
  headers_add = "X-RPR-Rewrite: SMTP envelope sender rewritten by $primary_hostname\n\
                 \tSee RPR_URL"
  errors_to = "${quote:bounce-\
                 ${md5:\
                   RPR_SECRET-\
                   ${sg {$tod_log}{^(\\\\d+)-(\\\\d+)-(\\\\d+) (\\\\d+):(\\\\d+):(\\\\d+)}{\\$1\\$2\\$3\\$4\\$5}}=\
                   ${sg {${sg {$sender_address}{([=#%_])}{_\\$1}}}{@}{#}}=\
                   ${sg {$original_local_part}{([=#%_])}{_\\$1}}\
                   ${if eq {$domain}{$original_domain}\
                     {%$original_domain@$primary_hostname}\
                     {@$original_domain}\
                    }\
                 }-\
                 ${sg {$tod_log}{^(\\\\d+)-(\\\\d+)-(\\\\d+) (\\\\d+):(\\\\d+):(\\\\d+)}{\\$1\\$2\\$3\\$4\\$5}}=\
                 ${sg {${sg {$sender_address}{([=#%_])}{_\\$1}}}{@}{#}}=\
                 ${sg {$original_local_part}{([=#%_])}{_\\$1}}\
                 ${if eq {$domain}{$original_domain} {%$original_domain}{}}\
               }@${if eq {$domain}{$original_domain} {$primary_hostname}{$original_domain}}"

##############################################################################