TLS 1.3 PSK succeeds even if then pre-shared key is wrong

[Matt Caswell]

On 20/04/2020 12:59, brandon.murphy1996 via openssl-users wrote:
> From what I noticed, the handshake completes successfully, regardless
> of the value of "psk_key" (as long as PSK length is even). However,
> if the identity value is mismatched between psk_find_session_cb and
> use_session_cb, the handshake fails with the message:

It's not clear from your question what you expected to happen. The
length of the PSK key doesn't actually matter from a TLS perspective
(obviously in practice it is best if the length is consistent with the
ciphersuite key length).

Or did you mean that that the value doesn't matter - even if it is
mismatched with the client's value? That would be unexpected (and
probably indicates you are not actually using the PSK at all and doing a
full handshake).

Matt