Re: [TLS] CCS and key reset and renegotiation

Peter Gutmann <pgut001@cs.auckland.ac.nz> Fri, 06 June 2014 01:42 UTC

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From: Peter Gutmann <pgut001@cs.auckland.ac.nz>
To: "<tls@ietf.org>" <tls@ietf.org>
Thread-Topic: [TLS] CCS and key reset and renegotiation
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Date: Fri, 6 Jun 2014 01:41:53 +0000
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Subject: Re: [TLS] CCS and key reset and renegotiation
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Watson Ladd <watsonbladd@gmail.com> writes:

>The spec needs a state machine.

No, it's this that created the problem in the first place.  SSL/TLS (and SSH,
and others) are best described using a ladder diagram (and in fact that's how
pretty much every diagram of the protocols that I've ever seen does them).
The fact that the spec dresses it up like a state machine means that anyone
who actually tries to implement it that way ends up vulnerable to mistakes
like the current OpenSSL one.  So the spec needs to take a protocol that
exists as a ladder diagram and describe it as such, not pretend that it's
meant to be a state machine.

Peter.