From a04f3a2976940022009c154fe0400fb8464b014c Mon Sep 17 00:00:00 2001 From: Mark Sapiro Date: Sat, 7 Oct 2017 15:28:06 -0700 Subject: Improved DMARC testing for domains with DNSSEC validation problems. --- Mailman/Utils.py | 16 ++++++++++++++-- 1 file changed, 14 insertions(+), 2 deletions(-) (limited to 'Mailman') diff --git a/Mailman/Utils.py b/Mailman/Utils.py index 75481563..9c366352 100644 --- a/Mailman/Utils.py +++ b/Mailman/Utils.py @@ -1267,11 +1267,23 @@ def _DMARCProhibited(mlist, email, dmarc_domain, org=False): txt_recs = resolver.query(dmarc_domain, dns.rdatatype.TXT) except (dns.resolver.NXDOMAIN, dns.resolver.NoAnswer): return 'continue' + except (dns.resolver.NoNameservers): + syslog('error', + 'DNSException: No Nameservers available for %s (%s)', + email, dmarc_domain) + # Typically this means a dnssec validation error. Clients that don't + # perform validation *may* successfully see a _dmarc RR whereas a + # validating mailman server wont see the _dmarc RR. We should mitigate + # this email to be safe. + return True except DNSException, e: syslog('error', 'DNSException: Unable to query DMARC policy for %s (%s). %s', - email, dmarc_domain, e.__doc__) - return 'continue' + email, dmarc_domain, e.__doc__) + # While we can't be sure what caused the error, there is potentially + # a DMARC policy record that we missed and that a receiver of the mail + # might see. Thus, we should err on the side of caution and mitigate. + return True else: # Be as robust as possible in parsing the result. results_by_name = {} -- cgit v1.2.3