Tor and DNS - how does it work?

Discussion in 'privacy problems' started by dumpydonk, Apr 6, 2010.

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  1. dumpydonk

    dumpydonk Registered Member

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    I want to clarify the situation with Tor and DNS requests.

    My current set-up is that Firefox is set to transport all HTTP and HTTPS traffic through port 8118 (Polipo) which then forwards all traffic to Tor on port 9050.

    AIUI, DNS requests are pushed through the HTTP proxy (Polipo) which then transfers them to the SOCKS proxy (Tor).

    Let us assume I am using my ISPs DNS (i.e. not OpenDNS or an equivalent) for "normal" web surfing.

    At what point is my ISPs contacted? It cannot be by the Tor client (on my computer) because this would be before a Tor node has been contacted and therefore any request would contain my IP.

    Or does Tor bypass my ISPs DNS - in which case who does the 3rd exit node contact to determine the IP of the website I want?

    Thanks.
     
  2. dumpydonk

    dumpydonk Registered Member

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  3. RoamMaster

    RoamMaster Registered Member

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    Your ISP's DNS server should never be contacted at all. You connect to Tor by an ip, not a domain name. From there one of the Tor nodes uses a DNS server. Which DNS server would depend on the node making the request. In most cases it would likely be the node's ISP's DNS.
    Regardless *your* ISP's DNS is never used.

    There's a really simple test for this. Configure your computer to use OpenDNS. Then type in craigslist.og. If you go to craigslist.org anyway, then you're using OpenDNS. If it doesn't, you know you're not using a local DNS.
     
  4. lotuseclat79

    lotuseclat79 Registered Member

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    Hi dumpydonk,

    There is a variable in Firefox's about:config that needs to be set properly in order to use the Tor exit node's DNS server. I don't remember it off the top of my head. I'll have to look it up again in my notes and post what I find, unless someone else knows and posts it before then. There might be a note about this topic at the torproject.org website: see Tor Documentation

    Further, if you have a hardware router, if it is possible to login to the router, there are DNS entry tables that (at least on my router) you can change to be OpenDNS's primary and secondary servers for both coax and wireless network connections. This approach would give you a way to avoid your ISP's DNS server logging normally when not using Tor.

    -- Tom
     
  5. lotuseclat79

    lotuseclat79 Registered Member

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    Hi dumpydonk,

    See post#5 in the thread Tor hates me. for the changes to about:config in Firefox to be able to use the DNS server of the Tor Exit node.

    -- Tom
     
  6. lotuseclat79

    lotuseclat79 Registered Member

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    Hi PooseyII,

    To my knowledge, the link you referenced only yields a fully integrated package of FF w/Tor for Windows - not the other OSes (Mac OSX and Linux). Perhaps the developers of Tor need to be poked to include a pref.js file of the about:config settings they recommend in their documentation (unless it is there and I missed it), so, the other OSes can be consistent across all of the OSes.

    -- Tom
     
  7. RoamMaster

    RoamMaster Registered Member

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    Provided you're using Polipo, there's no reason to do this.
    It also allows you to use browsers other than FF.
     
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