1 files changed, 82 insertions, 0 deletions
diff --git a/kafka/scram.py b/kafka/scram.py
new file mode 100644
index 0000000..684925c
--- /dev/null
+++ b/kafka/scram.py
@@ -0,0 +1,82 @@
+from __future__ import absolute_import
+
+import base64
+import hashlib
+import hmac
+import uuid
+
+from kafka.vendor import six
+
+
+if six.PY2:
+    def xor_bytes(left, right):
+        return bytearray(ord(lb) ^ ord(rb) for lb, rb in zip(left, right))
+else:
+    def xor_bytes(left, right):
+        return bytes(lb ^ rb for lb, rb in zip(left, right))
+
+
+class ScramClient:
+    MECHANISMS = {
+        'SCRAM-SHA-256': hashlib.sha256,
+        'SCRAM-SHA-512': hashlib.sha512
+    }
+
+    def __init__(self, user, password, mechanism):
+        self.nonce = str(uuid.uuid4()).replace('-', '')
+        self.auth_message = ''
+        self.salted_password = None
+        self.user = user
+        self.password = password.encode('utf-8')
+        self.hashfunc = self.MECHANISMS[mechanism]
+        self.hashname = ''.join(mechanism.lower().split('-')[1:3])
+        self.stored_key = None
+        self.client_key = None
+        self.client_signature = None
+        self.client_proof = None
+        self.server_key = None
+        self.server_signature = None
+
+    def first_message(self):
+        client_first_bare = 'n={},r={}'.format(self.user, self.nonce)
+        self.auth_message += client_first_bare
+        return 'n,,' + client_first_bare
+
+    def process_server_first_message(self, server_first_message):
+        self.auth_message += ',' + server_first_message
+        params = dict(pair.split('=', 1) for pair in server_first_message.split(','))
+        server_nonce = params['r']
+        if not server_nonce.startswith(self.nonce):
+            raise ValueError("Server nonce, did not start with client nonce!")
+        self.nonce = server_nonce
+        self.auth_message += ',c=biws,r=' + self.nonce
+
+        salt = base64.b64decode(params['s'].encode('utf-8'))
+        iterations = int(params['i'])
+        self.create_salted_password(salt, iterations)
+
+        self.client_key = self.hmac(self.salted_password, b'Client Key')
+        self.stored_key = self.hashfunc(self.client_key).digest()
+        self.client_signature = self.hmac(self.stored_key, self.auth_message.encode('utf-8'))
+        self.client_proof = xor_bytes(self.client_key, self.client_signature)
+        self.server_key = self.hmac(self.salted_password, b'Server Key')
+        self.server_signature = self.hmac(self.server_key, self.auth_message.encode('utf-8'))
+
+    def hmac(self, key, msg):
+        return hmac.new(key, msg, digestmod=self.hashfunc).digest()
+
+    def create_salted_password(self, salt, iterations):
+        self.salted_password = hashlib.pbkdf2_hmac(
+            self.hashname, self.password, salt, iterations
+        )
+
+    def final_message(self):
+        client_final_no_proof = 'c=biws,r=' + self.nonce
+        return 'c=biws,r={},p={}'.format(self.nonce, base64.b64encode(self.client_proof).decode('utf-8'))
+
+    def process_server_final_message(self, server_final_message):
+        params = dict(pair.split('=', 1) for pair in server_final_message.split(','))
+        if self.server_signature != base64.b64decode(params['v'].encode('utf-8')):
+            raise ValueError("Server sent wrong signature!")
+
+