#29430: Use uTLS for meek TLS camouflage in Tor Browser --------------------------------------+-------------------------- Reporter: dcf | Owner: tbb-team Type: enhancement | Status: new Priority: Medium | Milestone: Component: Applications/Tor Browser | Version: Severity: Normal | Resolution: Keywords: meek utls | Actual Points: Parent ID: | Points: Reviewer: | Sponsor: --------------------------------------+--------------------------
Comment (by dcf): Replying to [comment:7 dcf]: > Heads up, upstream utls fixed a distinguishability bug recently. A second ClientHello (which the client sends after the server sends a HelloRetryRequest) was not being camouflaged correctly. I confirmed that the bug existed with HelloChrome_70 against ajax.aspnetcdn.com, but I haven't personally tested yet that the fix actually fixes it. When I do, I'll update the branch. > https://github.com/refraction-networking/utls/pull/21 Here's an updated branch with the aforementioned uTLS fix. It also requires a patch, attachment:tor-launcher-Make-uTLS- aware.helloretry.patch, that makes tor-launcher pass the `utls=` SOCKS arg (applies on top of comment:4:ticket:29627). * [https://gitweb.torproject.org/user/dcf/tor-browser-build.git/log/?h =meek-client-utls_2&id=b8a752802f177abf38f61c0b55c5325556986a3e new commits] * [https://gitweb.torproject.org/user/dcf/tor-browser-build.git/diff/?h =meek-client- utls_2&id=b8a752802f177abf38f61c0b55c5325556986a3e&id2=616fbe2c19a9fce7a9d0adbc466b259c18c45fb8 diff] since comment:1 Here is a packet capture: attachment:torbrowser-utls-helloretry.pcap.gz. And below are the fingerprints. The first one looks like Chrome, as expected. The second one (sent in response to HelloRetryRequest) seems to be very uncommon, but possibly I am misinterpreting the results. I've asked Sergey to look at it. * [https://tlsfingerprint.io/id/bc4c7e42f4961cd7 bc4c7e42f4961cd7] [https://web.archive.org/web/20190306042947/https://tlsfingerprint.io/id/bc4c7e42f4961cd7 (archive)] rank 11 * [https://tlsfingerprint.io/id/6f8a8a4b42dd552d 6f8a8a4b42dd552d] [https://web.archive.org/web/20190306043034/https://tlsfingerprint.io/id/6f8a8a4b42dd552d (archive)] rank 13911 * [https://tlsfingerprint.io/compare/bc4c7e42f4961cd7/6f8a8a4b42dd552d comparison] -- Ticket URL: <https://trac.torproject.org/projects/tor/ticket/29430#comment:12> Tor Bug Tracker & Wiki <https://trac.torproject.org/> The Tor Project: anonymity online
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