Re: [TLS] Cached-info substitution

Brian Smith <brian@briansmith.org> Fri, 19 February 2010 15:38 UTC

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Date: Fri, 19 Feb 2010 09:39:55 -0600
From: Brian Smith <brian@briansmith.org>
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To: Stefan Santesson <stefan@aaa-sec.com>
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Cc: tls@ietf.org
Subject: Re: [TLS] Cached-info substitution
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Stefan Santesson wrote:
> I like in principle your suggested simplification to omit whole handshake
> messages to indicate substitution. However, this works only if the cached
> parameter is the only parameter of the handshake message. I.e. It works for
> the server Certificate message but not for the certificate_authorities
> parameter of the CertificateRequest message.
>    
That's why I suggested to treat a zero-length 
CertificateRequest.certificate_authorities (encoded "0x00 0x00") as "use 
the cached value" if and only if the server hello says that the server 
supports caching it. Maybe it is also possible to treat a zero-length 
Certificate.certificate_list ("0x00 0x00 0x00") as "use the cached 
value" if and only if the server hello says the server supports caching 
it. I suggested omitting the Certificate message completely only because 
I am not sure if any cipher suites allow zero-length certificate lists 
for another reason.

Regards,
Brian