Re: [TLS] Signed messages should be prefixed with a NUL-terminated context string.

Adam Langley <agl@google.com> Mon, 01 December 2014 22:28 UTC

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From: Adam Langley <agl@google.com>
Date: Mon, 1 Dec 2014 14:28:28 -0800
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To: Eric Rescorla <ekr@rtfm.com>
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Subject: Re: [TLS] Signed messages should be prefixed with a NUL-terminated context string.
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On Wed, Nov 26, 2014 at 6:09 AM, Eric Rescorla <ekr@rtfm.com>; wrote:
> If someone wants to contribute a PR so that we can have something
> concrete to look at that would be even better.

I have submitted a PR for the padding and context-string changes:
https://github.com/tlswg/tls13-spec/pull/100

I did not change the CertificateVerify structure in the same commit
because I'm not quite sure that I follow the reasoning. The
CertificateVerify implicitly contains the client and server nonce
because it contains all the preceding handshake messages. What's the
motivation for duplicating them at the beginning? Is it simply to
avoid having the opaque signer understand the TLS structure? If so,
does the padding and context strings that I've just proposed break
that?


Cheers

AGL