Re: [TLS] TLS 1.2 hash agility

[Mike <mike-list at pobox.com>]

> > The only thing I could come up with is that putting the list of
> > signature algorithms in the CertificateRequest is a change to the
> > format of that message, so it requires version-specific processing,
> > whereas if you use the server extension, the format of Certificate
> > Request is the same as previous TLS versions.
>
> CertificateRequest will require version-specific processing anyway,
> because its semantics will change. For example, in TLS 1.0/1.1
> ClientCertificateType "rsa_sign" meant a certificate containing
> an RSA key, and signed with RSA. In TLS 1.2, it will probably
> mean just a cert containing an RSA key; the signature algorithm
> part will be specified separately.

Ok, this is valid.  However, I have too much code that looks like:

   if (version == ssl3)
      do_this;
   else if (version <= tls11)
      do_that;
   else
      do_the_other;

Which is a maintenance nightmare.  In some places I used separate
functions for different TLS versions, all of which are very similar,
so that is not ideal either.  The less of this we need, the better.

> (Another difference is that in TLS 1.0/1.1, clients that didn't
> have certificates often just ignored CertificateRequest; 
> current draft of TLS 1.2 mandates sending an empty Certificate 
> message instead.)

Yes, but you can change your code to always send an empty Certificate
even for the earlier versions.

Mike

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