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Re: [tor-bugs] #25594 [Obfuscation/Snowflake]: Broker: investigate non-domain-fronting secure client / proxy registrations
#25594: Broker: investigate non-domain-fronting secure client / proxy registrations
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Reporter: arlolra | Owner: (none)
Type: defect | Status: new
Priority: Medium | Milestone:
Component: Obfuscation/Snowflake | Version:
Severity: Normal | Resolution:
Keywords: | Actual Points:
Parent ID: | Points:
Reviewer: | Sponsor:
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Comment (by dcf):
Replying to [comment:4 arma]:
> Ok, from https://www.bamsoftware.com/papers/thesis/#fig:snowflake-
rendezvous it looks like it can be just one round-trip? So something like
encrypted dns is a great answer?
That's correct. It needs one round trip. DNS is a good match.
We should (but don't yet) encrypt client registration messages; see
#22945. The registration messages don't reveal a ''ton'' of sensitive
metadata beyond the client's IP address (which we can't hide anyway); but
there's no reason not to encrypt it. I believe the statement from the
description ''"the client is making TLS connections with the broker"'' is
incorrect; in the domain fronting case, the client has a TLS session with
the CDN, and the CDN has a TLS session with the broker, but the CDN is in
a MITM position and can read the plaintest of registration messages, in
the absence of any other protection. It's the same thing with encrypted
DNS: we may as well encrypt the messages before encoding them as DNS
requests. But that's a privacy thing, not a blocking resistance thing.
The situation with Moat is more complicated: Moat relies on end-to-end TLS
with bridgedb.torproject.org for integrity: it doesn't have separate
integrity for the message that contains your 3 bridges, for instance. So
Moat is using a comparatively heavyweight full meek tunnel, constructing a
general-purpose bidirectional tunnel atop multiple roundtrips. In Moat,
there is an outer TLS session between the client and the CDN, and a
separate outer TLS session between the CDN and BridgeDB's Moat endpoint;
but inside of both is a tunneled end-to-end TLS session between the client
and BridgeDB.
--
Ticket URL: <https://trac.torproject.org/projects/tor/ticket/25594#comment:5>
Tor Bug Tracker & Wiki <https://trac.torproject.org/>
The Tor Project: anonymity online
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