Move sasl.py to a directory module and move SCRAM logic to a different file,

move `github/module.py` to `github/__init__.py`

modules/sasl/__init__.py

@@ -1,5 +1,6 @@
 import base64, hashlib, hmac, uuid
 from src import ModuleManager, utils
+from . import scram
 
 def _validate(self, s):
     mechanism = s
@@ -68,62 +69,17 @@ class Module(ModuleManager.BaseModule):
             sasl_username, sasl_password = sasl["args"].split(":", 1)
             if event["message"] == "+":
                 # start SCRAM handshake
-                first_base = "n=%s,r=%s" % (
-                    _scram_escape(sasl_username), _scram_nonce())
-                first_withchannel = "n,,%s" % first_base
-                auth_text = first_withchannel.encode("utf8")
-                event["server"]._scram_first = first_base.encode("utf8")
+                event["server"]._scram = scram.SCRAM(
+                    algo, sasl_username, sasl_password)
+                auth_text = event["server"]._scram.client_first()
+                print(auth_text)
             else:
-                data = base64.b64decode(event["message"]).decode("utf8")
-                pieces = dict(piece.split("=", 1) for piece in data.split(","))
-                if "s" in pieces:
-                    # server-first-message
-                    nonce = pieces["r"].encode("utf8")
-                    salt = base64.b64decode(pieces["s"])
-                    iterations = pieces["i"]
-                    password = sasl_password.encode("utf8")
-
-                    salted_password = hashlib.pbkdf2_hmac(algo, password, salt,
-                        int(iterations), dklen=None)
-                    event["server"]._scram_salted_password = salted_password
-
-                    client_key = hmac.digest(salted_password, b"Client Key",
-                        algo)
-                    stored_key = hashlib.new(algo, client_key).digest()
-
-                    channel = base64.b64encode(b"n,,")
-                    auth_noproof = b"c=%s,r=%s" % (channel, nonce)
-                    auth_message = b"%s,%s,%s" % (event["server"]._scram_first,
-                        data.encode("utf8"), auth_noproof)
-                    event["server"]._scram_auth_message = auth_message
-
-                    client_signature = hmac.digest(stored_key, auth_message,
-                        algo)
-                    client_proof = base64.b64encode(
-                        _scram_xor(client_key, client_signature))
-
-                    auth_text = auth_noproof + (b",p=%s" % client_proof)
-                elif "v" in pieces:
-                    # server-final-message
-                    verifier = pieces["v"]
-
-                    salted_password = event["server"]._scram_salted_password
-                    auth_message = event["server"]._scram_auth_message
-                    server_key = hmac.digest(salted_password, b"Server Key",
-                        algo)
-                    server_signature = hmac.digest(server_key, auth_message,
-                        algo)
-
-                    del event["server"]._scram_first
-                    del event["server"]._scram_salted_password
-                    del event["server"]._scram_auth_message
-
-                    if server_signature != base64.b64decode(verifier):
-                        raise ValueError("SCRAM %s authentication failed "
-                            % algo)
-                        event["server"].disconnect()
-                    auth_text = "+"
-
+                current_scram = event["server"]._scram
+                if current_scram.state == scram.SCRAMState.ClientFirst:
+                    auth_text = current_scram.server_first(event["message"])
+                elif current_scram.state == scram.SCRAMState.ClientFinal:
+                    auth_text = current_scram.server_final(event["message"])
+                    del event["server"]._scram
         else:
             raise ValueError("unknown sasl mechanism '%s'" % mechanism)
 

modules/sasl/scram.py

@@ -0,0 +1,87 @@
+import base64, enum, hashlib, hmac, uuid
+
+def _scram_nonce():
+    return uuid.uuid4().hex.encode("utf8")
+def _scram_escape(s):
+    return s.replace(b"=", b"=3D").replace(b",", b"=2C")
+def _scram_unescape(s):
+    return s.replace(b"=3D", b"=").replace(b"=2C", b",")
+def _scram_xor(s1, s2):
+    return bytes(a ^ b for a, b in zip(s1, s2))
+
+class SCRAMState(enum.Enum):
+    Uninitialised = 0
+    ClientFirst = 1
+    ClientFinal = 2
+    Success = 3
+    VerifyFailed = 4
+
+class SCRAMError(Exception):
+    pass
+
+class SCRAM(object):
+    def __init__(self, algo, username, password):
+        self._algo = algo
+        self._username = username.encode("utf8")
+        self._password = password.encode("utf8")
+
+        self.state = SCRAMState.Uninitialised
+        self._client_first = None
+        self._salted_password = None
+        self._auth_message = None
+
+    def _get_data(self, message):
+        data = base64.b64decode(message)
+        return data, dict(piece.split(b"=", 1) for piece in data.split(b","))
+
+    def client_first(self):
+        self.state = SCRAMState.ClientFirst
+        # start SCRAM handshake
+        self._client_first = b"n=%s,r=%s" % (
+            _scram_escape(self._username), _scram_nonce())
+        return b"n,,%s" % self._client_first
+
+    def server_first(self, message):
+        self.state = SCRAMState.ClientFinal
+
+        data, pieces = self._get_data(message)
+        # server-first-message
+        nonce = pieces[b"r"]
+        salt = base64.b64decode(pieces[b"s"])
+        iterations = pieces[b"i"]
+        password = self._password
+
+        salted_password = hashlib.pbkdf2_hmac(self._algo, password, salt,
+            int(iterations), dklen=None)
+        self._salted_password = salted_password
+
+        client_key = hmac.digest(salted_password, b"Client Key", self._algo)
+        stored_key = hashlib.new(self._algo, client_key).digest()
+
+        channel = base64.b64encode(b"n,,")
+        auth_noproof = b"c=%s,r=%s" % (channel, nonce)
+        auth_message = b"%s,%s,%s" % (self._client_first, data, auth_noproof)
+        self._auth_message = auth_message
+
+        client_signature = hmac.digest(stored_key, auth_message, self._algo)
+        client_proof = base64.b64encode(
+            _scram_xor(client_key, client_signature))
+
+        return auth_noproof + (b",p=%s" % client_proof)
+
+    def server_final(self, message):
+        # server-final-message
+        data, pieces = self._get_data(message)
+        verifier = pieces[b"v"]
+
+        server_key = hmac.digest(self._salted_password, b"Server Key",
+            self._algo)
+        server_signature = hmac.digest(server_key, self._auth_message,
+            self._algo)
+
+        if server_signature != base64.b64decode(verifier):
+            self.state = SCRAMState.VerifyFailed
+            return None
+        else:
+            self.state = SCRAMState.Success
+            return "+"