Wenn man bei Office365 oder Google Apps for Business einen eigenen Mailserver (Postfix) vorschalten möchte beim versenden/empfangen muss man die Mailserver von Microsoft/Google Whitelisten in den mynetworks bei Postfix.

Das Script löst alle SPF Record includes auf und generiert CIDR Maps die sich in Postfix einbinden lassen.

Beispiel:

max@dev1:~$ python get_subnets_of_spf_record_mynetwoks.py
Working on job office365
Working on job google

Es werden 2 Files erzeugt:

max@dev1:~$ cat /etc/postfix/networks/google 
64.18.0.0/20 OK
64.233.160.0/19 OK
66.102.0.0/20 OK
66.249.80.0/20 OK
72.14.192.0/18 OK
74.125.0.0/16 OK
108.177.8.0/21 OK
173.194.0.0/16 OK
207.126.144.0/20 OK
209.85.128.0/17 OK
216.58.192.0/19 OK
216.239.32.0/19 OK
[2001:4860:4000::]/36 OK
[2404:6800:4000::]/36 OK
[2607:f8b0:4000::]/36 OK
[2800:3f0:4000::]/36 OK
[2a00:1450:4000::]/36 OK
[2c0f:fb50:4000::]/36 OK
172.217.0.0/19 OK
108.177.96.0/19 OK
max@dev1:~/test$ cat /etc/postfix/networks/office365
207.46.101.128/26 OK
207.46.100.0/24 OK
207.46.163.0/24 OK
65.55.169.0/24 OK
157.56.110.0/23 OK
157.55.234.0/24 OK
213.199.154.0/24 OK
213.199.180.0/24 OK
157.56.112.0/24 OK
207.46.51.64/26 OK
157.55.158.0/23 OK
64.4.22.64/26 OK
40.92.0.0/14 OK
40.107.0.0/17 OK
40.107.128.0/17 OK
134.170.140.0/24 OK
[2a01:111:f400::]/48 OK
23.103.128.0/19 OK
23.103.198.0/23 OK
65.55.88.0/24 OK
104.47.0.0/17 OK
23.103.200.0/21 OK
23.103.208.0/21 OK
23.103.191.0/24 OK
216.32.180.0/23 OK
94.245.120.64/26 OK
[2001:489a:2202::]/48 OK

In Posftix werden sie in der main.cf eingebunden:

# ----------------------------------------------------------------------
# My Networks
# ----------------------------------------------------------------------
mynetworks =
        cidr:/etc/postfix/networks/local
        cidr:/etc/postfix/networks/other
        cidr:/etc/postfix/networks/google
        cidr:/etc/postfix/networks/office365

Da sich zwischendurch die Records auch mal ändern können empfiehlt es sich einen Cronjob dafür einzurichten. Ich habe eine Variante mit diff die nur patcht wenn das Resultat nicht null ist.

Das Script lässt sich auch noch für andere Dienste / etc. anpassen:

lookup_spf = {
# Google Apps for Business
"google": {
          "domain": "google.com",
          "file"  : "/etc/postfix/networks/google",
          },

# Office365
"office365": {
          "domain": "spf.protection.outlook.com",
          "file"  : "/etc/postfix/networks/office365",
          },

# Example
"example": {
          "domain": "example.com",
          "file"  : "/etc/postfix/networks/example",
          },

}

Sourcecode:

#!/usr/bin/env python

#
# get_subnets_of_spf_record_mynetwoks.py
# Resolve all known ip addresses from spf record and generate cidr map for postfix
#
# Version 1.0
# Written by Maximilian Thoma (http://www.lanbugs.de)
#
# The generated files can be used in postfix config with for example mynetworks = cidr:/etc/postfix/<generated_file>
#
# 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., 51 Franklin St, Fifth Floor, Boston, 
# MA 02110, USA
#

#
# Requirements:
# dnspython module  -> pip install dnspython
#

import dns.resolver
from dns.exception import DNSException
import re
import sys

# Look for DNS Record at:
#
# "jobname": {
#            "domain": "domainname",
#            "file": "output_file",
#            }
#

# 

lookup_spf = {
# Google Apps for Business
"google": {
          "domain": "google.com",
          "file"  : "/etc/postfix/networks/google",
          },

# Office365
"office365": {
          "domain": "spf.protection.outlook.com",
          "file"  : "/etc/postfix/networks/office365",
          },
}

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

def getspf(record, filehandler):
    # Init Resolver
    myResolver = dns.resolver.Resolver()

    try:
        # Try to lookup TXT record
        myAnswer = myResolver.query(record,"TXT")

    except DNSException:
        sys.stderr.write("Failed to query record, SPF broken.")
        return

    results = []

    for rdata in myAnswer:
        # Get string out of records
        for txt_string in rdata.strings:
            # Append to SPF Records buffer if "spf" in string
            if "spf" in txt_string:
                results.append(txt_string)

    # If results >=1
    if len(results) >= 1:
        # Work on records
        for spf in results:
            # Split parts
            parts = spf.split(" ")
            # Check parts
            for part in parts:

                s_include = re.match(r"^include:(?P<domain>.*)$", part)
                s_ip4 = re.match(r"^ip4:(?P<ip4>.*)$", part)
                s_ip6 = re.match(r"^ip6:(?P<ip6>.*)$", part)

                # If in part "include" found, next round
                if s_include:
                    getspf(s_include.group('domain'), filehandler)
                # elif ip4 found
                elif s_ip4:
                    filehandler.write(s_ip4.group('ip4') + " OK\n")
                # elif ip6 found
                elif s_ip6:
                    filehandler.write("[" + s_ip6.group('ip6').replace("/","]/") + " OK\n")
                # else no valid record
                else:
                    pass
    # no results 
    else:
        sys.stderr.write("No results")
        pass

def main():
    # Working on jobs
    for jobname, config in lookup_spf.iteritems():

        print "Working on job %s" % jobname

        # open file
        filehandler = open(config['file'], 'w')
        # start query spf records
        getspf(config['domain'], filehandler)
        # close file
        filehandler.close()


#getspf(lookup_spf)

if __name__ == "__main__":
    main()

 

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