Re: [TLS] Verifying X.509 Certificate Chains out of order
pgut001@cs.auckland.ac.nz (Peter Gutmann) Tue, 21 October 2008 14:56 UTC
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From: pgut001@cs.auckland.ac.nz
To: nelson@bolyard.me, tls@ietf.org
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Date: Wed, 22 Oct 2008 03:56:59 +1300
Subject: Re: [TLS] Verifying X.509 Certificate Chains out of order
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Nelson B Bolyard <nelson@bolyard.me> writes: >One major difference between tracking with cookies (or TLS session IDs) and >using certs is that cookies and TLS session IDs contain only information >previously put there by the server itself. When the server fetches them, it >doesn't learn anything about the user that it didn't already know. It has >merely learned that a user who has previously been to this web site has now >returned. But certs reveal information that could well have previously been >unknown to the server. Fetching certs is a way to do information discovery. I'm sure this can be argued endlessly, but given a mechanism that has 100% coverage/penetration (cookies/Flash cookies/cache cookies/Javascript/whatever) and one that has a coverage level two orders of magnitude below the margin of error, I know which one I'd be using to track users, regardless of some theoretical advantage that one might have. >Finally, I will add that the decision to change the default behavior for >client auth was made by the browser UI folks, not by the crypto folks. UI folks did this? Wow. I guess they had no idea of the consequences of their actions :-). >The subsequent discovery of lots of sites that are doing this seems to prove >that the threat was not merely imaginary. That doesn't say anything about the threat, merely that there are lots of misconfigured servers. The fact that the server admins had no idea their servers were doing this and even less idea how to turn it off, and that the servers threw the certs away when they were given them, would argue strongly against any attempt at deliberate user tracking. Peter. _______________________________________________ TLS mailing list TLS@ietf.org https://www.ietf.org/mailman/listinfo/tls
- [TLS] Verifying X.509 Certificate Chains out of o… Simon Josefsson
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Rob Dugal
- Re: [TLS] Verifying X.509 Certificate Chains out … Dr Stephen Henson
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Eric Rescorla
- Re: [TLS] Verifying X.509 Certificate Chains out … Steven M. Bellovin
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Mike
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Stefan Santesson
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Axel.Heider
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Alexander Klink
- Re: [TLS] Verifying X.509 Certificate Chains out … Eric Rescorla
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Sylvester
- Re: [TLS] Verifying X.509 Certificate Chains out … Eric Rescorla
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Sylvester
- Re: [TLS] Verifying X.509 Certificate Chains out … Stefan Santesson
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Stefan Santesson
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Steven M. Bellovin
- [TLS] Antwort: Re: Verifying X.509 Certificate Ch… Axel.Heider
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Nelson B Bolyard
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Ben Laurie
- Re: [TLS] Verifying X.509 Certificate Chains out … Ben Laurie
- Re: [TLS] Verifying X.509 Certificate Chains out … Jeffrey A. Williams
- Re: [TLS] Verifying X.509 Certificate Chains out … Martin Rex
- Re: [TLS] Verifying X.509 Certificate Chains out … Nelson B Bolyard
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Nelson B Bolyard
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Simon Josefsson
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Yoav Nir
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Nelson B Bolyard
- Re: [TLS] Verifying X.509 Certificate Chains out … Peter Gutmann
- Re: [TLS] Verifying X.509 Certificate Chains out … Alexander Klink