feat: Added CredSSP support when private key is known

[alxbl]

This pull request adds a --auth switch that allows to selectively enable the authentication mechanisms that PyRDP will allow through. For now these only include tls and ssp with some strict limitations for CredSSP.

It also finally documents how to extract the private key of RDP servers so that we can close #154
Also resolves #134.

Details

• Does not support the actual negotiation of CredSSP, which would require a lot of code and knowledge of the NTLM hash or the target's credentials.
• Does not support the CredSSPY attack that was just released.
• In order for the connection to be MITMed, it requires the private key of the server

In practice, this means that the only purpose of this feature is to allow honeypots to expose CredSSP. Note that usage of CredSSP means credential stuffing is not possible since a secret key is derived from the NTLM hash of the credentials.

Future Work

This pull-request also paves the way towards supporting other authentication techniques such as Early User Authorization (EUA), but that is not yet implemented.

[obilodeau]

It also finally documents how to extract the private key of RDP servers so that we can close #154

That's awesome! 🥳

[Res260]

Awesome PR, can't wait to see it in action :)

[obilodeau]

Discussed briefly with @alxbl and this is good to go!