The DNS interface
- Standard DNSEL, if I understand right, looks like this: There's some host
- at foo.example.com. You want to know if 1.2.3.4 is in the list, so you
- query for an A record for 4.3.2.1.foo.example.com. If the record exists,
- 1.2.3.4 is in the list. If you get an NXDOMAIN error, 1.2.3.4 is not in
- the list.
+ Standard DNSEL, if I understand right, looks like this: There's some
+ authoritative name server for foo.example.com. You want to know if
+ 1.2.3.4 is in the list, so you query for an A record for
+ 4.3.2.1.foo.example.com. If the record exists and has the value
+ 127.0.0.2[DNSBL-EMAIL], 1.2.3.4 is in the list. If you get an NXDOMAIN
+ error, 1.2.3.4 is not in the list. If you ask for a domain name outside
+ of the foo.example.com zone, you get a Server Failure error[RFC 1035].
- Assume that the DNSEL sits at some host, torhosts.example.com. Below
- are some queries that could be supported, though some of them are
- possibly a bad idea.
+ Assume that the DNSEL answers queries authoritatively for some zone,
+ torhosts.example.com. Below are some queries that could be supported,
+ though some of them are possibly a bad idea.
Query type 1: "General IP:Port"
Rule:
Iff {IP1} is a Tor server that permits connections to {port} on
- {IP2}, then there should be an A record.
+ {IP2}, then there should be an A record with the value 127.0.0.2.
Example:
- "1.0.0.10.80.4.3.2.1.ip-port.torhosts.example.com" should exist
- if and only if there is a Tor server at 10.0.0.1 that allows
- connections to port 80 on 1.2.3.4.
+ "1.0.0.10.80.4.3.2.1.ip-port.torhosts.example.com" should have the
+ value 127.0.0.2 if and only if there is a Tor server at 10.0.0.1
+ that allows connections to port 80 on 1.2.3.4.
Example use:
I'm running an IRC server at w.x.y.z:9999, and I want to tell
Other issues:
+ After a Tor server op turns off their server, it stops publishing server
+ descriptors. We should consider that server's IP address to still
+ represent a Tor node until 48 hours after its last descriptor was
+ published.
+
30-60 minutes is not an unreasonable TTL.
There could be some demand for address masks and port lists. Address
to launch periodic requests to itself through all exit servers whose
policies allow it -- and then see where the requests actually come from.
+References:
+
+ [DNSBL-EMAIL] Levine, J., "DNS Based Blacklists and Whitelists for
+ E-Mail", http://tools.ietf.org/html/draft-irtf-asrg-dnsbl-02, November
+ 2005.
+
+ [RFC 1035] Mockapetris, P., "Domain Names - Implementation and
+ Specification", RFC 1035, November 1987.