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Re: [tor-talk] SOCKS proxy to sit between user and Tor?



Hi Jeremy,

Thank you for the thoughtful and thorough reply! I  think the users of
your software will appreciate you wanting to minimize  attack surface.
One thing I've noticed about mitmproxy is that it  appears to only
support SOCKS upstream proxies *without* authentication.  It's also a
http proxy, so although it's certainly useful, it may not  meet your
current requirements (in transparent proxy mode you'll exclude support
on Windows). I may be mistaken of course.

If I understand correctly you  intend to use the intermediate SOCKS
proxy to perform the translation of  .bit address to destination
format. If the address doesn't require  translation you'll pass it
through along with any authentication used  for domain-isolation. The
downside of using an intermediate proxy is  that you'll have an extra
dependency. The intermediate proxy needs to be  modified to perform
lookups against a local resolver as needed. If  proposal 229 [1] is
implemented you'll need to be aware of the changes.  This may turn
into maintenance difficulty in the long run.

If this  were a regular browser you could always just setup the local
DNS  resolver to forward if not resolving .bit addresses. Since this
is tor  you need to make that resolver aware of tor being used, and to
use the  SOCKS proxy instead (or tor-resolve). So maybe that's one
option. Have a  local DNS resolver which forwards to tor after
checking the address  (and turn off browser Remote DNS). That is to
say it might be easier to  maintain your own resolver implementation
which can be kept as simple as  you need. This would keep (some)
cross-browser compatibility, from TBB,  to Firefox. The downside being
the whole system will rely on the  resolver so you'll have to worry
about: conflicts with other local  resolvers (dnsmasq, some vpn), or
need to set the DNS server manually.  It looks like you do this
currently. If the local resolver wrapped all  the related processes
you could make a UI available to indicate status.

As a browser-plugin based alternative, maybe you can do without the
extra SOCKS proxy by a change to the plugin design. Say you use
Observer Notifications in the plugin. Now intercept the address and if
it ends in .bit make a request against a (local) server holding the
blockchain. This provides some flexibility in that you're not
restricted to using a SOCKS proxy. It should work with TBB. Unless I'm
mistaken (and I frequently am) websockets are enabled (check with
tbb-devs on this). An alternative approach would be to create your own
address bar for resolving addresses using the same approach previously
mentioned. There's a downside to this approach, in that if someone
were to use the regular bar, the resolve will be relayed using tor,
which might actually work if the exit DNS is setup to resolve
namecoin. 

Besides that, I'm only familiar with the SSH SOCKS proxy, and Tor's
SOCKS proxy. I can only look at the list of SOCKS servers on
Wikipedia, or HAProxy, as was previously mentioned, for other options.

In any case, thank you for trying to make FreeSpeechMe compatible with
tor.

--leeroy

[1]
https://gitweb.torproject.org/torspec.git/tree/proposals/229-further-socks5-extensions.txt

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