ALPN: complete handshake without accepting a client's protocols. (#876)
* ALPN: complete handshake without accepting a client's protocols.
The callback passed to `SSL_CTX_set_alpn_select_cb` can return
`SSL_TLSEXT_ERR_NOACK` to allow the handshake to continue without
accepting any of the client's offered protocols.
This commit introduces `NO_OVERLAPPING_PROTOCOLS`, which the Python
callback passed to `Context.set_alpn_select_callback` can return to
achieve the same thing.
It does not change the previous meaning of an empty string, which
still terminates the handshake.
* Update src/OpenSSL/SSL.py
Co-Authored-By: Alex Gaynor <alex.gaynor@gmail.com>
* Address @alex's review.
* Use recorded value in test, fix lint error.
* Cover TypeError branch in _ALPNHelper.callback
4 files changed