Remove OpenSSL tmp_rsa_callback. Removes support for ephemeral RSA in TLS.

Remove OpenSSL tmp_rsa_callback. Removes support for ephemeral RSA in TLS.

This code would not really generate ephemeral keys every time it is called,
but a single key that would be reused during process lifetime and returned
each time the function was called; probably not what users would expect.

TLS allowes ephemeral keys to be used only when no other key exchange, such
as (ephemeral) Diffie-Hellman, is performed. The end result is that it was
only used by a number of (weak) export ciphers, which could give users a
false sense of security.

So, instead of fixing a weak cipher mode, we'll just remove support for it
completely. Plenty of better alternatives are available in TLS.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1388607026-12297-5-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8152
Signed-off-by: Gert Doering <gert@greenie.muc.de>