[TLS] Heartbeat and padding

[Michael D'Errico <[e-mail]>]

Not related to Heartbleed(tm), do we need to revisit the Heartbeat spec.
due to the random padding?  There is a requirement to add at least 16
bytes of random padding to every message:

    struct {
       HeartbeatMessageType type;
       uint16 payload_length;
       opaque payload[HeartbeatMessage.payload_length];
       opaque padding[padding_length];
    } HeartbeatMessage;

    ...

    padding:  The padding is random content that MUST be ignored by the
       receiver.  The length of a HeartbeatMessage is TLSPlaintext.length
       for TLS and DTLSPlaintext.length for DTLS.  Furthermore, the
       length of the type field is 1 byte, and the length of the
       payload_length is 2.  Therefore, the padding_length is
       TLSPlaintext.length - payload_length - 3 for TLS and
       DTLSPlaintext.length - payload_length - 3 for DTLS.  The
       padding_length MUST be at least 16.

    The sender of a HeartbeatMessage MUST use a random padding of at
    least 16 bytes.  The padding of a received HeartbeatMessage message
    MUST be ignored.


Since the recipient MUST ignore the padding, they can't reverse engineer
the peer's PRNG, so maybe this isn't a problem?

Mike