Adds Extended Master Secret to TLS (RFC 7627)

[adamjanovsky]

extms snads for Extended Master Secret, see RFC 7627.

I just needed to do this for myself, so created PR by the way. If it does not comply to the rules or is screwed in any way, I'm probably not spending more time on this...

Did not created unit test, however tested it on few real handshakes. It works. My assumptions:

• The ClientHello offers using this extension via extension field. But whether it is actually going to be used is decided by the server, in a similar field inside the Server Hello record.
• Scapy is already gathering the handshake messages, so they can be used easily.

Based on this, I did the following adjustments:

• tls_session_update on TLSServerHello record looks for the extension and notes its usage into the session object
• tls_session_update on ClientKeyExchange gathers all handshake messages into one binary string and computes the hash on it. By that time, all should be available.
• Then, the master secret is computed with the updated compute_master_secret method.

[gpotter2]

Thanks a lot for your PR,

However, we cannot merge it if does not passes the tests. You are failing the PEP8 one (formatting of your code). It’s really fast to fix

scapy/layers/tls/handshake.py:32:80: E501 line too long (86 > 79 characters)
scapy/layers/tls/handshake.py:991:1: E303 too many blank lines (5)
scapy/layers/tls/handshake.py:995:1: E302 expected 2 blank lines, found 5
scapy/layers/tls/crypto/prf.py:210:80: E501 line too long (94 > 79 characters)

The PR needs this and a test. If you don’t find the time to provide a test, could you simply give us a small code example of its usage, so that I can add it myself ?

[adamjanovsky]

Yeah, I'll try to do that on next week. pá 31. 8. 2018 v 22:52 odesílatel Gabriel Potter <notifications@github.com> napsal:

…

Thanks a lot for your PR, However, we cannot merge it if does not passes the tests. You are failing the PEP8 one (formatting of your code). It’s really fast to fix scapy/layers/tls/handshake.py:32:80: E501 line too long (86 > 79 characters) scapy/layers/tls/handshake.py:991:1: E303 too many blank lines (5) scapy/layers/tls/handshake.py:995:1: E302 expected 2 blank lines, found 5 scapy/layers/tls/crypto/prf.py:210:80: E501 line too long (94 > 79 characters) The PR needs this and a test. If you don’t find the time to provide a test, could you simply give us a small code example of its usage, so that I can add it myself ? — You are receiving this because you authored the thread. Reply to this email directly, view it on GitHub <#1574 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AGejJ-Jodvx1oIqouZ2TqiBFyvRSizBNks5uWaIggaJpZM4WJkKD> .

[guedou]

@adamjanovsky any progress on the requested fixes?

[adamjanovsky]

Not at all. Completely dropped it from my priority list... st 10. 10. 2018 v 11:20 odesílatel Guillaume Valadon < notifications@github.com> napsal:

…

@adamjanovsky <https://github.com/adamjanovsky> any progress on the requested fixes? — You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub <#1574 (comment)>, or mute the thread <https://github.com/notifications/unsubscribe-auth/AGejJ8IEb5x8aMUqsyJQfJUTW5s3GHxiks5ujbvUgaJpZM4WJkKD> .

[guedou]

An improved version was submitted in #2403