Adding TLS 1.2 Support to Your TLS Library - Implementing SSL/TLS Using Cryptography and PKI - page 484

int bufsz,
TLSParameters *parameters )
{
…
update_digest( &parameters->sha256_handshake_digest,
handshake_msg_start, handshake.length + 4 );
}
}
else if ( message.type == content_alert )
3. Finally, tls_resume and tls_connect must both be changed to initialize
this digest rather than the two parallel digests that they initialized in
Chapters 6 and 8. Listing 9-7 demonstrates.
Listing 9-7: “tls.c” TLS 1.2 handshake digest initialization
int tls_resume( int connection,
int session_id_length,
const unsigned char *session_id,
const unsigned char *master_secret,
TLSParameters *parameters )
{
init_parameters( parameters, 0 );
parameters->connection_end = connection_end_client;
parameters->session_id_length = session_id_length;
memcpy( &parameters->session_id, session_id, session_id_length );
new_sha256_digest( &parameters->sha256_handshake_digest );
...
int tls_connect( int connection,
TLSParameters *parameters,
int renegotiate )
{
init_parameters( parameters, renegotiate );
parameters->connection_end = connection_end_client;
new_sha256_digest( &parameters->sha256_handshake_digest );
…
int tls_accept( int connection,
TLSParameters *parameters )
{
init_parameters( parameters, 0 );
parameters->connection_end = connection_end_server;
new_sha256_digest( &parameters->sha256_handshake_digest );
...
Of course, if you want to implement this code to support TLS 1.0 through TLS
1.2 concurrently, you'd have some conditional logic to initialize the handshake
digests depending on the version of TLS.