Comment 23 for bug 1197884

Created attachment 25714
Allow admin-choosen DH parameters for DHE enabled cipher-modes

In order to be EAL4+ validated for one of our customers, Apache needs to be able to support 2048+ bits group size for Diffie-Hellman parameters. Right now, temporary parameters are 512 and 1024 bits only.

We can still disallow DH at all, leaving only RSA for authentication and pre-master secret encryption, but that's a suboptimal solution, as we then loose forward secrecy.

Adding a 2048 bits DH temporary key into mod_ssl is not possible, since OpenSSL would only ask for a 512/1024 bits one, depending on the "exportability" of the choosen ciper-mode.

This patch adds a new configuration directive, "SSLDHParametersFile <file>", allowing the administrator to supply its own Diffie-Hellman parameters ("openssl dhparam 2048 > dhparam2048.pem" to generate 2048 bits ones, for example).
If this directive is specified and parameters are found in the supplied file, then these parameters will be used whenever DHE is used to negociate the pre-master secret. If this directive is not used, then it works like it does now, leaving OpenSSL ask mod_ssl for a set of parameters of the desired size (512 or 1024 bits).

We'd like this to be evaluated, discussed, and if possible, applied.

Regards.