Switch to pyOpenSSL library

[b-ranto]

python-rsa library exhibits several security flaws, this patch drops
the python-rsa dependency and implements the same functionality with
pyOpenSSL library.

[b-ranto]

Note: debian-based distros know this under the name python-openssl.

btw: I've again tested the patch with tests/unit/cloudfront/test_signed_urls.py unit test and it passed all the tests.

[danielgtaylor]

@BRANTO1 thanks for the pull request and trying to get this updated. It seems that PyOpenSSL actually depends on the cryptography module:

https://github.com/pyca/pyopenssl/blob/master/setup.py#L37

So if we switch from python-rsa I think we'd just go with cryptography directly, unless there is a good reason not to. We are still deciding which way to move forward with this issue.

[alex]

This has teh advantage that pyOpenSSL is packaged in older versions of debian, etc. and folks can still use that version.

[b-ranto]

Yep, this should also work in fedora 20, rhel 7 and some other systems where there is no cryptography module.

[kevgliss]

Any update on which way this is going to go? I will be working on a pull request adding signature verification to SNS messages.

I have no problem with either, but would lean towards cryptography if given a choice.