Re: [TLS] About encrypting SNI - Traffic Analysis Attacks?
mrex@sap.com (Martin Rex) Wed, 14 May 2014 02:20 UTC
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To: Stephen Farrell <stephen.farrell@cs.tcd.ie>
Date: Wed, 14 May 2014 04:20:07 +0200
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From: mrex@sap.com
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Subject: Re: [TLS] About encrypting SNI - Traffic Analysis Attacks?
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Stephen Farrell wrote: > > One other thought, maybe more optimistic: could it be that > there might be ways to protect things like SNI used for > routing the 2nd and later times you visit a web site, even > if TLS had to put the DNS name in clear (or close-to) first > time around? The latter looks like a contradiction to SNI being used for routing to me. When SNI is used for routing, then it MUST be present on the initial ClientHello on every new connection, or routing (to other than the default credential) will be impossible. It doesn't really matter whether that routing is physical (to a different backend server) or just logical (to a different server credential on the same host. The session_id that is normally used for the abbreviated handshake is no suitable substitute here. These sessions may expire quickly and randomly (like depending on server load and cache contention), within a few minutes, and the session cache is not necessarily shared among TLS clients or among TLS servers involved in the communication. E.g. a while ago I observed an unfavorable behaviour of a browser on a platform after an OS minor version upgrade with respect to browser plugins. The OS upgrade seems to have seperated the browser's TLS session cache from the TLS session cache used by the plugins, and the plugins were not prepared to do their own promptin "server cert warning--do you want to continue anyway", but instead just silently failed (resulting in a blank/white area where the plugin should have rendered the contents). Hiding the server hostname by encrypting SNI looks extremely silly for anything that operates like a web browser. Those beasts spill HTTP-Referers all over the place, keep bookmarks, keep histories, keep cookies and do lots of other stuff to spread hostnames from URLs all over the place. The hostname horse has left the barn 25 years ago. Closing the barn door today is going to be futile. IF you have anything to hide, then you MUST ensure, that it is not vitally dependend on the hostname of the server remaining secret. I do not believe that it would be a good idea to create the provably false impression that TLS is a panacea and hiding of SNI would provide any security or any privacy benefit vaguely similar to characteristics that TOR tries to provide -- because it doesn't, and can't. -Martin
- [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Martin Thomson
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Watson Ladd
- Re: [TLS] About encrypting SNI Russ Housley
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Alyssa Rowan
- Re: [TLS] About encrypting SNI Nick Mathewson
- Re: [TLS] About encrypting SNI Daniel Kahn Gillmor
- Re: [TLS] About encrypting SNI Sniffen, Brian
- Re: [TLS] About encrypting SNI Yoav Nir
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Seth David Schoen
- Re: [TLS] About encrypting SNI Nico Williams
- Re: [TLS] About encrypting SNI Watson Ladd
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Yoav Nir
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Watson Ladd
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Alyssa Rowan
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Martin Rex
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Tom Ritter
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Watson Ladd
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Sniffen, Brian
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Alyssa Rowan
- Re: [TLS] About encrypting SNI Michael D'Errico
- Re: [TLS] About encrypting SNI James Cloos
- Re: [TLS] About encrypting SNI Jacob Appelbaum
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Erik Nygren
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Jacob Appelbaum
- [TLS] Forged RST (was: About encrypting SNI) Alyssa Rowan
- Re: [TLS] Forged RST (was: About encrypting SNI) Eric Rescorla
- Re: [TLS] About encrypting SNI Paul Lambert
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Erik Nygren
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] Forged RST (was: About encrypting SNI) Yoav Nir
- Re: [TLS] About encrypting SNI Sniffen, Brian
- Re: [TLS] Forged RST (was: About encrypting SNI) Erik Nygren
- Re: [TLS] About encrypting SNI James Cloos
- Re: [TLS] Forged RST Stephen Farrell
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] Forged RST (was: About encrypting SNI) Nico Williams
- Re: [TLS] About encrypting SNI Erik Nygren
- Re: [TLS] About encrypting SNI Sniffen, Brian
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Martin Thomson
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Eric Rescorla
- Re: [TLS] About encrypting SNI Sniffen, Brian
- Re: [TLS] About encrypting SNI Erik Nygren
- Re: [TLS] Forged RST (was: About encrypting SNI) Bill Frantz
- Re: [TLS] Forged RST (was: About encrypting SNI) Yoav Nir
- Re: [TLS] Forged RST (was: About encrypting SNI) Bill Frantz
- Re: [TLS] Forged RST (was: About encrypting SNI) Eric Rescorla
- Re: [TLS] Forged RST (was: About encrypting SNI) Watson Ladd
- Re: [TLS] Forged RST (was: About encrypting SNI) Eric Rescorla
- Re: [TLS] About encrypting SNI Marsh Ray
- Re: [TLS] About encrypting SNI Martin Rex
- Re: [TLS] About encrypting SNI David Holmes
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Marsh Ray
- Re: [TLS] About encrypting SNI Marsh Ray
- Re: [TLS] About encrypting SNI Nico Williams
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI Michael D'Errico
- Re: [TLS] About encrypting SNI Watson Ladd
- Re: [TLS] About encrypting SNI Erik Nygren
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Daniel Kahn Gillmor
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI - Traffic Analysis… Michael StJohns
- Re: [TLS] About encrypting SNI - Traffic Analysis… Nico Williams
- Re: [TLS] About encrypting SNI - Traffic Analysis… Stephen Farrell
- Re: [TLS] About encrypting SNI - Traffic Analysis… Martin Rex
- Re: [TLS] About encrypting SNI Nikos Mavrogiannopoulos
- Re: [TLS] About encrypting SNI Salz, Rich
- Re: [TLS] About encrypting SNI Stephen Farrell
- Re: [TLS] About encrypting SNI Andy Lutomirski
- Re: [TLS] About encrypting SNI - Traffic Analysis… Martin Thomson
- Re: [TLS] About encrypting SNI - Traffic Analysis… Tom Ritter
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Fabrice
- Re: [TLS] About encrypting SNI Jacob Appelbaum
- Re: [TLS] About encrypting SNI Paul Lambert
- Re: [TLS] About encrypting SNI Yoav Nir
- Re: [TLS] About encrypting SNI Daniel Kahn Gillmor
- Re: [TLS] About encrypting SNI Tim Bray
- Re: [TLS] About encrypting SNI Jacob Appelbaum
- Re: [TLS] About encrypting SNI Paul Hoffman
- Re: [TLS] About encrypting SNI Viktor Dukhovni
- Re: [TLS] About encrypting SNI Brian Sniffen
- Re: [TLS] About encrypting SNI Yoav Nir