Use RSA_generate_key_ex() instead of deprecated, RSA_generate_key()

This patch moves from using the deprecated RSA_generate_key() to the 'new'
RSA_generate_key_ex() to generate ephemeral RSA keys. This patch does
not change OpenVPN's behaviour.

One note on the implementation though; the code generates one ephemeral
RSA key that is used during the entire lifetime of an OpenVPN process.
If OpenSSL requests a new (ephemeral) key, it will keep on returning the
same (usually rather small) key. Not the best solution.

To actually run this code, I had to force usage by selecting the
TLS-RSA-EXPORT-WITH-DES40-CBC-SHA tls-cipher. That generated a 512-bit
ephemeral RSA key, and uses the outdated DES encryption protocol.

Using this mode could lead to a false sense of security. Then again, one
should be using (Ephemeral) Diffie-Hellman anyway, and OpenVPN requires
a tls-server to supply dh parameters. A user would need to deliberately
choose a weak tls-cipher like TLS-RSA-EXPORT-WITH-DES40-CBC-SHA, which
would be aligning a gun with his foot anyway. If one would decide this
implementation is not good enough anymore, I'd suggest to just strip out
support for this completely.

Code has been tested using the TLS-RSA-EXPORT-WITH-DES40-CBC-SHA tls-cipher
which uses this to create ephemeral RSA keys.

This should resolve trac#197.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Arne Schwabe <arne@rfc2549.org>
Message-Id: <52ADF633.8040003@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8110

Signed-off-by: Gert Doering <gert@greenie.muc.de>
Also update TLSv1_method() calls in support code to SSLv23_method() calls.

Commit 4b67f98 changed calls to TLSv1_{sever,client}_method() to
SSLv23_{client,server}_method() to enable TLS version negotiation. This
commit does the same for two calls of TLSv1_method() from support code.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1388607026-12297-2-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8148
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit dd3e319c1d66c7da51b8555d745a1139e0b322f2)
Update TLSv1 error messages to SSLv23 to reflect changes from commit 4b67f98

Commit 4b67f98 changed call to TLSv1_{client,server}_method() to
SSLv23_{client,server}_method(), this commit updates the corresponding
error messages to match the changes in the code.

Signed-off-by: Steffan Karger <steffan@karger.me>
Acked-by: Gert Doering <gert@greenie.muc.de>
Message-Id: <1388607026-12297-3-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8147
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit 441be9f4f91a16218d40b401384ead51b5aac0cc)
If --tls-cipher is supplied, make --show-tls parse the list.

This allows to check the available TLS ciphers for a specific configuration
by supplying both --tls-cipher and --show-tls options.

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: <1388607026-12297-4-git-send-email-steffan@karger.me>
URL: http://article.gmane.org/gmane.network.openvpn.devel/8150
Signed-off-by: Gert Doering <gert@greenie.muc.de>
(cherry picked from commit cb03dca83e37fd65666bf776f39da902fb10acbc)