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Re: [tor-bugs] #5011 [Pluggable transport]: Discuss possible designs for an external program that discovers bridge addresses to tell Tor about them
#5011: Discuss possible designs for an external program that discovers bridge
addresses to tell Tor about them
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Reporter: karsten | Owner: mikeperry
Type: task | Status: new
Priority: normal | Milestone:
Component: Pluggable transport | Version:
Keywords: MikePerry201203 | Parent: #5010
Points: | Actualpoints:
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Comment(by nickm):
Replying to [comment:12 mikeperry]:
> > So it's important to make sure that this kind of attack won't work.
>
> Yeah, you're right. For best practice, BridgeFinder should create a way
for BridgeFinderHelper to authenticate. I was hoping not to have to solve
that.. What's the best option? Some sort of filesystem-based cookie
authentication? BridgeFinder's simple control port barfs a file path for
BridgeFinderHelper to read from? What about BridgeFinderHelpers that can't
read arbitrary file paths? (I think Chrome extensions fall into this
category).
So as a first step, make the data format reject partially-bogus messages,
or messages with junk at the start. That'll make some standard cross-
protocol attacks harder.
Second, once the BridgeFinder and whoever needs to use it share a secret,
they can authenticate pretty easily; possibly with a simple HMAC
challenge-response system. (That'd be ideal; see discussions on #5185).
So the only hard part is making sure they share a secret.
How were you planning for the Chrome extension or the Warcraft plugin or
whatever to learn the port of the bridgefinder ? Presumably they could
learn the shared secret via the same channel. Finding an appropriate
channel for esoterically sandboxed stuff is likely to require specific
work depending on the details of the sandbox; I don't know enough about
Chrome plugins to know what mechanism would work.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/5011#comment:13>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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