Allow use of different crypto libraries for GPL compliance

[majn]

I've been thinking about ways of how to resolve some GPL licensing issue in telegram-purple (see majn/telegram-purple#1), which is caused by the hard dependency on OpenSSL in libtgl. I'm probably not the only one that might run into this issue, since the OpenSSL license is incompatible with the GPL and not every project has the ability to add a GPL exception for OpenSSL.

I think one good way to solve this would be to provide a way to pass a struct of crypto functions to use instead of using OpenSSL statically, and providing a way to compile libtgl without OpenSSL. This would allow others to compile it with something like libgcrypt if GPL-compliance is a hard dependency.

Im working on a pull request to patch that functionality, is there is any chance that you would merge such a thing?

[vysheng]

Probably. But you will need not only use different crypto functions, but also another bignum library, and random generator.

Though I don't see any licensing problems. At least when you distribute in source code form.

[dequis]

Isn't this fixed? I see --disable-openssl is merged.

[BenWiederhake]

@dequis: It should stay open until the branch is stable and gets merged to master.