[tor-dev] Tor and DNS

Jakob Schlyter jakob at kirei.se
Fri Feb 10 07:20:06 UTC 2012

On 7 feb 2012, at 22:08, Ondrej Mikle wrote:

> 1. full packet might leak identifying information about OS or resolver used,
> quoting Nick:
>> There are parts of a DNS packet that we wouldn't want
>> to have the Tor client make up.  For example, DNS transaction IDs
>> would need to avoid collisions. Similarly, I don't see why the client
>> should be setting most  of the possible flags.
> The query will work as if following was set: flags 0x110 (recursive,
> non-authenticated data ok), DO bit set. Is there any reason for setting some
> flags otherwise or make some optional?

If you bundle a full resolver (e.g. libunbound) with the TOR client, you will be much better off doing full DNS packet transport, or you have to rewrite the upstream forwarding code. I do about the potential fingerprinting issues (I'm one of the people behind Net::DNS::Fingerprint), but in this case I believe we can mitigate these issues (if considered important) by masking/rewriting some DNS request fields within the TOR client and/or exit node.


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