[psp] Add support for the PSP Security Protocol

[eyalitki]

Checklist:

• [V] If you are new to Scapy: I have checked CONTRIBUTING.md (esp. section submitting-pull-requests)
• [V] I squashed commits belonging together
• [V] I added unit tests or explained why they are not relevant
• [V] I executed the regression tests (using cd test && ./run_tests or tox)

Description:

PSP stands for PSP Security Protocol, and is a lightweight IPSec-Like implementation that was released by Google and is getting traction within data centers.

This commit adds support for versions 0 & 1 of the protocol which use AES-GCM in 128 and 265 bits. Support was tested against the testing tool of the RFC which is quite cumbersome. Example test vector is found in the usage instructions in the code itself.

The field names are taken from the LUA dissector for Wireshark as was provided by the RFC's GitHub repository.

[gpotter2]

Hi & thanks for the PR !

Could you:

• move this layer to contrib/ ? The general rule is to put layers that you'd find on any network in layers/, and more specialised ones in contrib
• add some unit tests? You'll find many examples in test/, it can be as easy as building and dissecting a few packets, and testing some fields.

Thanks !

[eyalitki]

Ack, made the changes as suggested. The unit tests include:

• Basic field checks
• The scenario from the usage example
• 3 main scenarios from the RFC testing tool itself - the .pcap files are auto-generated as "test vectors" by the RFC tool

This way, the unit tests ensure that Scapy complies with the RFC as part of its regression