Crypto: drop support for Botan and OpenSSL variants

[petermax2]

The crypto plugin(s) consist(s) in variants with the following crypto libraries in use:

• libgcrypt,
• OpenSSL, and
• Botan.

The variants have been introduced for academic research, which was finished in 2018. There is no other benefit of supporting several crypto libraries.

On the downside the maintenance effort of supporting the libraries mentioned above is increasing (e.g. #3385 ).

I think libgcrypt is the crypto library that best fits our needs (and has the nicest code-base). Also I do not expect the crypto library to cause increased maintenance effort.

Therefore I propose to drop the support of:

• OpenSSL, and
• Botan

and remove their corresponding compilation variants from the crypto plugin.

[markus2330]

I agree with the proposal!

[petermax2]

The implementation of this issue closes #3385 . Close #3385 .

[petermax2]

I'll start with the implementation so we get a feeling if the clean-up improves the situation.

Please feel free to discuss the proposal above in the meantime.

[markus2330]

Btw. there was also a maintenance issue with OpenSSL openwrt/packages#8998

So keeping only libgcrypt seems to be the perfect choice from maintenance point of view.

@haraldg: is this also ok for you? It seems like the openwrt package currently only uses OpenSSL?

Is it possible to build curl also with gcrypt so that the whole Elektra depends only on libgcrypt (and not OpenSSL)?

[mpranj]

If there are no major functional differences I fully agree with maintaining only the best plugin variant. It's also great to drop some dependencies. I think you are in the best position to make the decision which plugin to keep @petermax2, but libgcrypt seems to be a good decision according to your work.

[petermax2]

Is it possible to build curl also with gcrypt so that the whole Elektra depends only on libgcrypt (and not OpenSSL)?

Libgcrypt does not provide any TLS/SSL functions. I'm afraid you won't be able to build curl with gcrypt.