diff options
Diffstat (limited to 'Mailman')
| -rw-r--r-- | Mailman/Utils.py | 29 |
1 files changed, 25 insertions, 4 deletions
diff --git a/Mailman/Utils.py b/Mailman/Utils.py index 1aa49954..0344ef58 100644 --- a/Mailman/Utils.py +++ b/Mailman/Utils.py @@ -1170,7 +1170,28 @@ def IsDMARCProhibited(mlist, email): at_sign = email.find('@') if at_sign < 1: return False - dmarc_domain = '_dmarc.' + email[at_sign+1:] + dparts = email[at_sign+1:].split('.') + # The following is a way of testing the "Organizational Domain" for DMARC + # policy if the From: domain doesn't publish a policy. What we're doing + # is clearly wrong. I.e., if the From: domain is a.b.c.example.com, we + # should lookup _dmarc.a.b.c.example.com and if no DMARC policy there, + # we should look up only _dmarc.example.com. The problem is not all + # Organizational Domains are two "words" and determining any particular + # Organizational Domain requires applying a non-trivial algorithm to a + # large, somewhat dynamic data set. What we do is look up all the + # intermediate domains on the theory that if _dmarc.a.b.c.example.com has + # no valid DMARC policy then the intermediates won't either. We will also + # err with a domain like x.y.x.co.uk. Here we will go to far and also look + # up _dmarc.co.uk which is also wrong but hopefully won't return a policy. + # This is clearly a flawed approach, but hopefully good enough. + while len(dparts) > 1: + x = _DMARCProhibited(mlist, email, '_dmarc.' + '.'.join(dparts)) + if x != 'continue': + return x + dparts = dparts[1:] + return False + +def _DMARCProhibited(mlist, email, dmarc_domain): try: resolver = dns.resolver.Resolver() @@ -1178,12 +1199,12 @@ def IsDMARCProhibited(mlist, email): resolver.lifetime = float(mm_cfg.DMARC_RESOLVER_LIFETIME) txt_recs = resolver.query(dmarc_domain, dns.rdatatype.TXT) except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer): - return False + return 'continue' except DNSException, e: syslog('error', 'DNSException: Unable to query DMARC policy for %s (%s). %s', email, dmarc_domain, e.__class__) - return False + return 'continue' else: # people are already being dumb, don't trust them to provide honest DNS # where the answer section only contains what was asked for, nor to include @@ -1223,7 +1244,7 @@ def IsDMARCProhibited(mlist, email): dmarcs = filter(lambda n: n.startswith('v=DMARC1;'), results_by_name[name]) if len(dmarcs) == 0: - return False + return 'continue' if len(dmarcs) > 1: syslog('error', """RRset of TXT records for %s has %d v=DMARC1 entries; |