tree 25fe4bb0a0ded2364eaa2c5e3a92b792fd95fd4d
parent 4a9d006f5f524890f2d2f77e3df00ccc02fc7364
author Hanno Becker <hanno.becker@arm.com> 1534520878 +0100
committer Hanno Becker <hanno.becker@arm.com> 1534520878 +0100

Don't send empty fragments of nonempty handshake messages

This for example lead to the following corner case bug:
The code attempted to piggy-back a Finished message at
the end of a datagram where precisely 12 bytes of payload
were still available. This lead to an empty Finished fragment
being sent, and when  mbedtls_ssl_flight_transmit() was called
again, it believed that it was just starting to send the
Finished message, thereby calling ssl_swap_epochs() which
had already happened in the call sending the empty fragment.
Therefore, the second call would send the 'rest' of the
Finished message with wrong epoch.