Re: [TLS] Collisions (Re: Consensus Call: FNV vs SHA1)
Nicolas Williams <Nicolas.Williams@oracle.com> Tue, 11 May 2010 19:28 UTC
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Date: Tue, 11 May 2010 14:23:50 -0500
From: Nicolas Williams <Nicolas.Williams@oracle.com>
To: Simon Josefsson <simon@josefsson.org>
Message-ID: <20100511192350.GS9429@oracle.com>
References: <AC1CFD94F59A264488DC2BEC3E890DE50A43B479@xmb-sjc-225.amer.cisco.com> <20100510190954.GV9429@oracle.com> <87r5lj4eee.fsf@mocca.josefsson.org> <20100510215652.GA9429@oracle.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] Collisions (Re: Consensus Call: FNV vs SHA1)
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On Mon, May 10, 2010 at 04:56:52PM -0500, Nicolas Williams wrote: > On Mon, May 10, 2010 at 11:48:09PM +0200, Simon Josefsson wrote: > > It seems a server could easily create two pairs of server certificates > > that results in the same FNV-1a value but are different certificates. A > > client connecting to a server offering a cached value for the server > > certificate would not know which server certificate was intended, even > > after completing the handshake. If correct, that seems surprising. > > If the server figures it out, who cares. If not, bad. I didn't think this through yesterday. Let me try again. The only way the collision could happen and the handshake succeed is (at least for the cipher suites I've thought about) if a) the two certs have the same public key, b) the client had seen one or both server certs earlier. And the attack? I think it could be mostly harmless because the server thinks the client authenticated the server as one entity name while the client thinks it authenticated the server as another -- but both server names must have been reasonably close to equivalent (HUGE assumption; keep reading). Sure, the client could get redirected to another server, but only if the incorrect cert was properly signed, and only if the client cache learns about that object (more assumptions). The devil's in the details! Some of those devilish details: - Clients MUST NOT cache objects from failed handshakes. - Clients MAY cache objects from succesful handshakes, and only when the clients authenticate the server (including validation of the server's cert chain to a TA). - In particular there MUST NOT be any caching in cases where the server is authenticated by the use of pre-shared certificates. - There must be no chance of caching objects when a user clicks through one of those "give your money to the bad guys?" dialogs. Any others? Yes, I should review the document closely now. Nico --
- Re: [TLS] Wrapping up cached info Blumenthal, Uri - 0668 - MITLL
- [TLS] Consensus Call: FNV vs SHA1 Joseph Salowey (jsalowey)
- Re: [TLS] Consensus Call: FNV vs SHA1 Simon Josefsson
- Re: [TLS] Consensus Call: FNV vs SHA1 Blumenthal, Uri - 0668 - MITLL
- Re: [TLS] Consensus Call: FNV vs SHA1 Adam Langley
- Re: [TLS] Consensus Call: FNV vs SHA1 Marsh Ray
- Re: [TLS] Consensus Call: FNV vs SHA1 Robert Dugal
- Re: [TLS] Consensus Call: FNV vs SHA1 Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Martin Rex
- Re: [TLS] Consensus Call: FNV vs SHA1 Jeffrey A. Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Paul Hoffman
- [TLS] Collisions (Re: Consensus Call: FNV vs SHA1) Nicolas Williams
- [TLS] Nico's suggestions - Re: Consensus Call: FN… Stefan Santesson
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Blumenthal, Uri - 0668 - MITLL
- [TLS] Collisions (Re: Nico's suggestions - Re: Co… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Simon Josefsson
- [TLS] Collisions (Re: Consensus Call: FNV vs SHA1) Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Simon Josefsson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Hovav Shacham
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Simon Josefsson
- Re: [TLS] Consensus Call: FNV vs SHA1 Yoav Nir
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Martin Rex
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Consensus Call: FNV vs SHA1 Simon Josefsson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Michael D'Errico
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Martin Rex
- Re: [TLS] Consensus Call: FNV vs SHA1 Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Consensus Call: FNV vs SHA1 Blumenthal, Uri - 0668 - MITLL
- Re: [TLS] Consensus Call: FNV vs SHA1 Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Martin Rex
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Kemp, David P.
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Nicolas Williams
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Nic… Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Nicolas Williams
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Nic… Marsh Ray
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Con… Kemp, David P.
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Stefan Santesson
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Con… Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Stefan Santesson
- Re: [TLS] Collisions (Re: Consensus Call: FNV vs … Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Simon Josefsson
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Brian Smith
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Simon Josefsson
- Re: [TLS] Justification Adam Langley
- Re: [TLS] Justification Brian Smith
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Adam Langley
- Re: [TLS] Justification Marsh Ray
- Re: [TLS] Justification Brian Smith
- Re: [TLS] [POSSIBLE SPAM] Re: Collisions (Re: Con… Kemp, David P.
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Adam Langley
- [TLS] Use HTTP (Re: Justification) Nicolas Williams
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Yoav Nir
- Re: [TLS] Justification Michael D'Errico
- Re: [TLS] Justification Martin Rex
- Re: [TLS] Justification Marsh Ray
- Re: [TLS] Justification Stefan Santesson
- Re: [TLS] Justification Martin Rex
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Yoav Nir
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Stefan Santesson
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Collisions (Re: Nico's suggestions - Re… Marsh Ray
- Re: [TLS] Justification Dean Anderson
- [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Simon Josefsson
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Justification Stefan Santesson
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Justification Nicolas Williams
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Ben Laurie
- Re: [TLS] Wrapping up cached info Yoav Nir
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Ben Laurie
- Re: [TLS] Wrapping up cached info Martin Rex
- [TLS] Possible alternative to current cached info… Michael D'Errico
- Re: [TLS] Wrapping up cached info (and PRF WTF) Kemp, David P.
- Re: [TLS] Wrapping up cached info (and PRF WTF) Martin Rex
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info (and PRF WTF) Nicolas Williams
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Michael D'Errico
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Joseph Salowey (jsalowey)
- Re: [TLS] Wrapping up cached info Marsh Ray
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Michael D'Errico
- Re: [TLS] Wrapping up cached info Michael D'Errico
- Re: [TLS] Wrapping up cached info Kemp, David P.
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Ben Laurie
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Martin Rex
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Nicolas Williams
- Re: [TLS] Wrapping up cached info Stefan Santesson
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Brian Smith
- Re: [TLS] Wrapping up cached info Nicolas Williams