tree 0db9e36ee6c34f7889649903941b4502a0bb205a
parent 1841f84c7983cdb6cd188e0d536e63767c5d939c
author Hanno Becker <hanno.becker@arm.com> 1560778205 +0100
committer Hanno Becker <hanno.becker@arm.com> 1562240468 +0100

Don't store client-supported ECs in heap-allocated buffer

So far, the client-proposed list of elliptic curves was stored for the
duration of the entire handshake in a heap-allocated buffer referenced
from mbedtls_ssl_handshake_params::curves. It is used in the following
places:
1) When the server chooses a suitable ciphersuite, it checks that
   it has a certificate matching the ciphersuite; in particular, if
   the ciphersuite involves ECDHE, the server needs an EC certificate
   with a curve suitable for the client.
2) When performing the ECDHE key exchange, the server choose one
   curve among those proposed by the client which matches the server's
   own supported curve configuration.

This commit removes the hold back the entire client-side curve list
during the handshake, by performing (1) and (2) on during ClientHello
parsing, and in case of (2) only remembering the curve chosen for ECDHE
within mbedtls_ssl_handshake_params.