[gnutls-devel] GnuTLS | handshake: defer setting downgrade sentinel until version is selected (!918)

Development of GNU's TLS library gnutls-devel at lists.gnutls.org
Fri Feb 15 19:17:26 CET 2019


Hubert Kario commented on a discussion on lib/handshake.c:

>  
>  	_gnutls_handshake_log("HSK[%p]: Selected version %s\n", session, session->security_parameters.pversion->name);
>  
> +	/* set downgrade sentinel if the server supports TLS 1.3 and

one that does a TLS 1.2 resumption and then verifies that the sentinel was set? no

but it's very simple to do, it requires doing a regular resumption test and only providing one more option to `ExpectServerHello` the `server_max_protocol=` with `(3, 4)` as parameter: [test-downgrade-protection.py](https://github.com/tomato42/tlsfuzzer/blob/13479e5a44bc10e3577fc28b921c5b999a363ce9/scripts/test-downgrade-protection.py#L149-L178)

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