IPBlacklistFilterStrategy not properly querying the DNS RBLs

[testnutzer123@…]

The spam filter IPBlacklistFilterStrategy queries doesn't finalize the dns names to query properly and therefore does only relative lookups.

It queries, for exmaple, for '3.2.1.10.bsb.empty.us' when it should be querying for '3.2.1.10.bsb.empty.us.'

Although this works most of the times it will not if the resolver has zones configured to query for relative lookup in case absolute lookups doesn't yield anything. And one of those zones suddenly starts resolving wildcard.

Suppose you got:

• 3.2.1.10.bsb.empty.us
• and a resolv.conf like

  domain example.org
  search example.org example.com
  

• And example.com will start to resolve wildcard.

Internally queries will be:

• 3.2.1.10.bsb.empty.us. NXDOMAIN
• 3.2.1.10.bsb.empty.us.example.org. NXDOMAIN
• 3.2.1.10.bsb.empty.us.example.com. A 127.0.0.1 ←- OOPS

Hence sandbox/spam-filter/tracspamfilter/filters/ip_blacklist.py@4111#L55​ must be modified to:

• either

  query(prefix + server.encode('utf-8') + '.')
  

• or better

  from dns.name import from_text
  query(from_text(prefix + server.encode('utf-8')))
  

This bug is particularly bad as it might bite you in the arse all of a sudden when some infrastructure changes that you might not have under control.

[Jonas Borgström]

Fixed in [7539], thanks.