[TLS] TLS 1.2 and CertificateRequest message

[Nikos Mavrogiannopoulos <nmav at gnutls.org>]

Hello,
 I've been taking a look at TLS 1.2 and it seems that there is some new
negotiation added at the CertificateRequest message. At this message the
server is supposed to send a list of allowed algorithm for signature
calculation, and the client should respond with a signature that depends
on the previously exchanged handshake messages.

In previous versions of TLS a client could just start the hash
calculation for this signature during the exchange to avoid storing the
actual messages up to this point. However with this negotiation at this
point it is quite impossible to do that approach and as far as I
understand needs to follow the store approach.

My questions now are:
1. How is this implemented in compliant software today?

2. Why this negotiation was added? I see no added value of having such
negotiation at a so late point.

regards,
Nikos