Don't send signature algorithms when client_version is below TLS 1.2.
authorDavid Benjamin <davidben@google.com>
Sun, 6 Mar 2016 00:49:20 +0000 (19:49 -0500)
committerDr. Stephen Henson <steve@openssl.org>
Mon, 9 May 2016 16:46:23 +0000 (17:46 +0100)
commitf7aa318552c4ef62d902c480b59bd7c4513c0009
treedb4a080face26bd5e55733fab0f1cf034397a624
parent3105d695358d86c0f2a404b2b74a1870b941ce5e
Don't send signature algorithms when client_version is below TLS 1.2.

Per RFC 5246,

    Note: this extension is not meaningful for TLS versions prior to 1.2.
    Clients MUST NOT offer it if they are offering prior versions.
    However, even if clients do offer it, the rules specified in [TLSEXT]
    require servers to ignore extensions they do not understand.

Although second sentence would suggest that there would be no interop
problems in always offering the extension, WebRTC has reported issues
with Bouncy Castle on < TLS 1.2 ClientHellos that still include
signature_algorithms. See also
https://bugs.chromium.org/p/webrtc/issues/detail?id=4223

RT#4390

Reviewed-by: Matt Caswell <matt@openssl.org>
Reviewed-by: Stephen Henson <steve@openssl.org>
ssl/ssl_locl.h
ssl/t1_lib.c