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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!")
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