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samueltangz / swift-noise-protocol

Noise protocol implemented in Swift.
https://samueltangz.github.io/swift-noise-protocol/
MIT License
8 stars 4 forks source link

Update HandshakeState.swift #28

Open infiamit opened 3 years ago

infiamit commented 3 years ago

Fixed unnecessary hash if there is no payload to hash.

infiamit commented 3 years ago

If there is no payload, the library hashes the existing hash again which leads to Auth failure issue.

samueltangz commented 3 years ago

Hi, is there a reference showing that encryptAndHash only runs when the payload is non-empty?

I did not see a condition from section 5.3 of the Noise Protocol Framework specification saying that the call is skipped.

I also referred to a Python implementation: https://github.com/plizonczyk/noiseprotocol/blob/73375448c55af85df0230841af868b7f31942f0a/noise/state.py#L345 and https://github.com/plizonczyk/noiseprotocol/blob/73375448c55af85df0230841af868b7f31942f0a/noise/state.py#L164 but it doesn't skip the call as well.

infiamit commented 3 years ago

Hi, for the first token which is e, there is no need to do encryptAndHash as e is always plain text. This is the reason i was facing auth failure issue as it was hashing my payload which was non empty.

samueltangz commented 3 years ago

Section 5.2 of the Noise spec stated that:

EncryptAndHash(plaintext): Sets ciphertext = EncryptWithAd(h, plaintext), calls MixHash(ciphertext), and returns ciphertext. Note that if k is empty, the EncryptWithAd() call will set ciphertext equal to plaintext.

That said, even if there are no keys, MixHash is still called and the plaintext is mixed in.

I don't see a reason why we need to skip the hash - could you locate it from the spec?

infiamit commented 3 years ago

I am searching for the reference, however my point is that without this, i am facing auth fail errors, I will get back to you, if i found anything related to it.