Trouble decrypting messages (Example script included)

[bitnom]

I made a fork/branch to get the library working with Python 3.10. It works but as there is no documentation, I think I'm doing something wrong in my usage.

Installing my fork/branch:

pip install "git+https://github.com/bitnom/pure-python-otr.git@python3"

My example:

import potr
from potr.compatcrypto import DSAKey

# Custom Context class
class MyContext(potr.context.Context):
    def __init__(self, account, peername):
        super(MyContext, self).__init__(account, peername)

    def getPolicy(self, key):
        return self.user.getPolicy(key)

    def inject(self, msg, appdata=None):
        print(f"{self.user.name} -> {self.peer}: {msg}")
        if appdata:
            try:
                decrypted_msg, tlvs = appdata.receiveMessage(msg)
                if decrypted_msg:
                    print(f"{appdata.user.name} received decrypted message: {decrypted_msg}")
            except potr.context.NotEncryptedError:
                pass
            except potr.context.NotOTRMessage:
                pass

    def handleQuery(self, message, appdata=None):
        if 2 in message.versions and self.getPolicy('ALLOW_V2'):
            self.authStartV2(appdata=appdata)
        elif 1 in message.versions and self.getPolicy('ALLOW_V1'):
            self.authStartV1(appdata=appdata)
        else:
            print(f"{self.user.name} received a non-OTR message: {message.msg.decode('utf-8')}")

# Custom Account class with required methods
class MyAccount(potr.context.Account):
    contextclass = MyContext

    def __init__(self, *args, **kwargs):
        super(MyAccount, self).__init__(*args, **kwargs)
        self.policy = {
            'ALLOW_V2': True,
            'ALLOW_V1': False,
            'REQUIRE_ENCRYPTION': True,
            'SEND_TAG': True,
        }

    def loadPrivkey(self):
        return DSAKey.generate()

    def savePrivkey(self):
        pass

    def saveTrusts(self):
        pass

    def getPolicy(self, key):
        return self.policy.get(key, False)

# Initialize accounts for Alice and Bob
alice_account = MyAccount('alice@example.com', 'XMPP', maxMessageSize=1024)
bob_account = MyAccount('bob@example.com', 'XMPP', maxMessageSize=1024)

# Initialize contexts for Alice and Bob
alice_context = alice_account.getContext('bob@example.com')
bob_context = bob_account.getContext('alice@example.com')

# Alice sends an OTR query message to Bob
alice_query = alice_account.getDefaultQueryMessage(alice_context.getPolicy)
alice_context.inject(alice_query, appdata=bob_context)

# Wait for the AKE to complete
import time
time.sleep(5)

# Alice and Bob can now send encrypted messages to each other
encrypted_msg = alice_context.sendMessage(potr.context.FRAGMENT_SEND_ALL, b"Hello, Bob!", appdata=bob_context)
decrypted_msg, tlvs = bob_context.receiveMessage(encrypted_msg)
if decrypted_msg:
    print(f"Bob received decrypted message: {decrypted_msg}")

encrypted_msg = bob_context.sendMessage(potr.context.FRAGMENT_SEND_ALL, b"Hello, Alice!", appdata=alice_context)
decrypted_msg, tlvs = alice_context.receiveMessage(encrypted_msg)
if decrypted_msg:
    print(f"Alice received decrypted message: {decrypted_msg}")


# Alice and Bob can disconnect the OTR session
alice_context.disconnect()
bob_context.disconnect()

which prints:

alice@example.com -> bob@example.com: b'?OTRv2?\nI would like to start an Off-the-Record private conversation. However, you do not have a plugin to support that.\nSee https://otr.cypherpunks.ca/ for more information.'
bob@example.com -> alice@example.com: b'?OTR:AAICAAAAxKgjXJiCdN3p76/REwybuA3kWoZa5QOxuYsaZbLqO+pIfEDSkD1gUWGerdyj6ikELK0QArEcrhfQhvuw7OsfrCFujruX9AoNCglTIG5LLcU5skElWOk+DZQ1dunSMwn0E9BVGFCFfCtvXkjyESMwS2rU0LIR4topbdp9HLRNnJizNKWlpwO4Q1AxNqlF8OY9i265tqHj29EetAtcR2zx3P3dEdM3+aiJcZxoJ8h4YyKASmtD1QDHWR3D6JmPK3JQSN90DlkAAAAg1E8Re3oNsmtK6WRQtl3AMd6nPmi24q/F84ktgmIP90M=.'
bob@example.com -> alice@example.com: b'?OTR:AAICAAAAxIr+WZ5U1YFXf5KZ/IF+Exw5S0ENvJYEEq22rh2iQNldbB3QFWHmwr2PiymJ5kWeuj4XXDFwRM9Y08dzrGqq238aDeCMkGP1dIZ3O9s7Q/k3Pt9+pN9Csb3wbu9xUVFt3blSI5VoR4nVcAJrwlFcX4QpH6OWhmqqm6DDt/SoqXBeVGoddbhTGVQLEMcsjelXwmYeKjqxb3kR3ihgCli8b4/69rnK1/UiX8V5Wqp2FKd80uYH+XSH2vtFC9/4qWbdcjYBkC8AAAAgEagK0yJzkHwg7DQKF3nSL8IPGzD7YkZ5NwcIn+qk2oI=.'
alice@example.com -> bob@example.com: b'?OTR:AAICAAAAxGvDVCQvO9BDPzt916H400KtSjrFvic8qhkMyykSkCMHMNJL9yVUEsuqQqxSqu4CsqKmrwQekfGYMxmQF+u+ssuJJnJ4omXUGk1tjFvOgrG2677/rYSY4t7Cco96Ram9j3/DtKWrpc9V+jn7f0R8Gnf+LIrQtxnSOXAvTCD4BEGX25f72d5RGlGJZkb1ZsmV8j7Ov662P+G9PpEg+4VZhGXN1Y/YFmDAwuk4Sw4CK74Ge9Q9KEy+KWRKu3lowSEi96iBYrkAAAAgFnqzNfHwNx5UmHSXx7Fm0H6cNEUTKoZ9ioLLjKUIask=.'

Why is decrypted_msg always None? I must be missing something.