354 lines
14 KiB
Python
354 lines
14 KiB
Python
# -*- coding: utf-8 -*-
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""" Amazon Cognito implementation without external dependencies """
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# Based on https://github.com/retrospect-addon/plugin.video.retrospect/blob/master/channels/channel.be/vier/awsidp.py
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from __future__ import absolute_import, division, unicode_literals
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import base64
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import binascii
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import datetime
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import hashlib
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import hmac
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import json
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import logging
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import os
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import sys
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import requests
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import six
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_LOGGER = logging.getLogger('auth-awsidp')
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class AwsIdp:
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""" AWS Identity Provider """
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def __init__(self, pool_id, client_id):
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"""
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:param str pool_id: The AWS user pool to connect to (format: <region>_<poolid>).
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E.g.: eu-west-1_aLkOfYN3T
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:param str client_id: The client application ID (the ID of the application connecting)
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"""
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self.pool_id = pool_id
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if "_" not in self.pool_id:
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raise ValueError("Invalid pool_id format. Shoud be <region>_<poolid>.")
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self.client_id = client_id
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self.region = self.pool_id.split("_")[0]
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self.url = "https://cognito-idp.%s.amazonaws.com/" % (self.region,)
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self._session = requests.session()
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# Initialize the values
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# https://github.com/aws/amazon-cognito-identity-js/blob/master/src/AuthenticationHelper.js#L22
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self.n_hex = 'FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1' + \
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'29024E088A67CC74020BBEA63B139B22514A08798E3404DD' + \
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'EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245' + \
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'E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED' + \
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'EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D' + \
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'C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F' + \
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'83655D23DCA3AD961C62F356208552BB9ED529077096966D' + \
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'670C354E4ABC9804F1746C08CA18217C32905E462E36CE3B' + \
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'E39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9' + \
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'DE2BCBF6955817183995497CEA956AE515D2261898FA0510' + \
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'15728E5A8AAAC42DAD33170D04507A33A85521ABDF1CBA64' + \
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'ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7' + \
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'ABF5AE8CDB0933D71E8C94E04A25619DCEE3D2261AD2EE6B' + \
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'F12FFA06D98A0864D87602733EC86A64521F2B18177B200C' + \
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'BBE117577A615D6C770988C0BAD946E208E24FA074E5AB31' + \
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'43DB5BFCE0FD108E4B82D120A93AD2CAFFFFFFFFFFFFFFFF'
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# https://github.com/aws/amazon-cognito-identity-js/blob/master/src/AuthenticationHelper.js#L49
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self.g_hex = '2'
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self.info_bits = bytearray('Caldera Derived Key', 'utf-8')
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self.big_n = self.__hex_to_long(self.n_hex)
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self.g = self.__hex_to_long(self.g_hex)
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self.k = self.__hex_to_long(self.__hex_hash('00' + self.n_hex + '0' + self.g_hex))
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self.small_a_value = self.__generate_random_small_a()
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self.large_a_value = self.__calculate_a()
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_LOGGER.debug("Created %s", self)
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def authenticate(self, username, password):
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""" Authenticate with a username and password. """
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# Step 1: First initiate an authentication request
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auth_request = self.__get_authentication_request(username)
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auth_data = json.dumps(auth_request)
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auth_headers = {
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"X-Amz-Target": "AWSCognitoIdentityProviderService.InitiateAuth",
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"Accept-Encoding": "identity",
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"Content-Type": "application/x-amz-json-1.1"
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}
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auth_response = self._session.post(self.url, auth_data, headers=auth_headers)
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auth_response_json = json.loads(auth_response.content)
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challenge_parameters = auth_response_json.get("ChallengeParameters")
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_LOGGER.debug(challenge_parameters)
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challenge_name = auth_response_json.get("ChallengeName")
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if not challenge_name == "PASSWORD_VERIFIER":
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message = auth_response_json.get("message")
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_LOGGER.error("Cannot start authentication challenge: %s", message or None)
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return None
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# Step 2: Respond to the Challenge with a valid ChallengeResponse
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challenge_request = self.__get_challenge_response_request(challenge_parameters, password)
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challenge_data = json.dumps(challenge_request)
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challenge_headers = {
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"X-Amz-Target": "AWSCognitoIdentityProviderService.RespondToAuthChallenge",
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"Content-Type": "application/x-amz-json-1.1"
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}
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auth_response = self._session.post(self.url, challenge_data, headers=challenge_headers)
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auth_response_json = json.loads(auth_response.content)
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_LOGGER.debug("Got response: %s", auth_response_json)
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if "message" in auth_response_json:
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_LOGGER.error("Error logging in: %s", auth_response_json.get("message"))
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return None, None
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id_token = auth_response_json.get("AuthenticationResult", {}).get("IdToken")
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refresh_token = auth_response_json.get("AuthenticationResult", {}).get("RefreshToken")
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return id_token, refresh_token
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def renew_token(self, refresh_token):
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"""
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Sets a new access token on the User using the refresh token. The basic expire time of the
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refresh token is 30 days:
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http://docs.aws.amazon.com/cognito/latest/developerguide/amazon-cognito-user-pools-using-tokens-with-identity-providers.html
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:param str refresh_token: Token to use for refreshing the authorization token.
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"""
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refresh_request = {
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"AuthParameters": {
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"REFRESH_TOKEN": refresh_token
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},
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"ClientId": self.client_id,
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"AuthFlow": "REFRESH_TOKEN"
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}
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refresh_headers = {
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"X-Amz-Target": "AWSCognitoIdentityProviderService.InitiateAuth",
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"Content-Type": "application/x-amz-json-1.1"
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}
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refresh_request_data = json.dumps(refresh_request)
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refresh_response = self._session.post(self.url, refresh_request_data, headers=refresh_headers)
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refresh_json = json.loads(refresh_response.content)
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if "message" in refresh_json:
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_LOGGER.error("Error refreshing: %s", refresh_json.get("message"))
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return None
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id_token = refresh_json.get("AuthenticationResult", {}).get("IdToken")
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return id_token
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def __get_authentication_request(self, username):
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"""
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:param str username: The username to use
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:return: A full Authorization request.
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:rtype: dict
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"""
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auth_request = {
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"AuthParameters": {
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"USERNAME": username,
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"SRP_A": self.__long_to_hex(self.large_a_value)
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},
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"AuthFlow": "USER_SRP_AUTH",
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"ClientId": self.client_id
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}
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return auth_request
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def __get_challenge_response_request(self, challenge_parameters, password):
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""" Create a Challenge Response Request object.
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:param dict[str,str|imt] challenge_parameters: The parameters for the challenge.
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:param str password: The password.
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:return: A valid and full request data object to use as a response for a challenge.
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:rtype: dict
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"""
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user_id = challenge_parameters["USERNAME"]
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user_id_for_srp = challenge_parameters["USER_ID_FOR_SRP"]
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srp_b = challenge_parameters["SRP_B"]
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salt = challenge_parameters["SALT"]
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secret_block = challenge_parameters["SECRET_BLOCK"]
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timestamp = self.__get_current_timestamp()
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# Get a HKDF key for the password, SrpB and the Salt
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hkdf = self.__get_hkdf_key_for_password(
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user_id_for_srp,
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password,
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self.__hex_to_long(srp_b),
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salt
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)
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secret_block_bytes = base64.standard_b64decode(secret_block)
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# the message is a combo of the pool_id, provided SRP userId, the Secret and Timestamp
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msg = \
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bytearray(self.pool_id.split('_')[1], 'utf-8') + \
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bytearray(user_id_for_srp, 'utf-8') + \
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bytearray(secret_block_bytes) + \
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bytearray(timestamp, 'utf-8')
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hmac_obj = hmac.new(hkdf, msg, digestmod=hashlib.sha256)
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signature_string = base64.standard_b64encode(hmac_obj.digest()).decode('utf-8')
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challenge_request = {
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"ChallengeResponses": {
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"USERNAME": user_id,
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"TIMESTAMP": timestamp,
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"PASSWORD_CLAIM_SECRET_BLOCK": secret_block,
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"PASSWORD_CLAIM_SIGNATURE": signature_string
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},
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"ChallengeName": "PASSWORD_VERIFIER",
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"ClientId": self.client_id
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}
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return challenge_request
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def __get_hkdf_key_for_password(self, username, password, server_b_value, salt):
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""" Calculates the final hkdf based on computed S value, and computed U value and the key.
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:param str username: Username.
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:param str password: Password.
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:param int server_b_value: Server B value.
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:param int salt: Generated salt.
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:return Computed HKDF value.
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:rtype: object
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"""
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u_value = self.__calculate_u(self.large_a_value, server_b_value)
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if u_value == 0:
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raise ValueError('U cannot be zero.')
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username_password = '%s%s:%s' % (self.pool_id.split('_')[1], username, password)
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username_password_hash = self.__hash_sha256(username_password.encode('utf-8'))
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x_value = self.__hex_to_long(self.__hex_hash(self.__pad_hex(salt) + username_password_hash))
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g_mod_pow_xn = pow(self.g, x_value, self.big_n)
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int_value2 = server_b_value - self.k * g_mod_pow_xn
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s_value = pow(int_value2, self.small_a_value + u_value * x_value, self.big_n)
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hkdf = self.__compute_hkdf(
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bytearray.fromhex(self.__pad_hex(s_value)),
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bytearray.fromhex(self.__pad_hex(self.__long_to_hex(u_value)))
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)
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return hkdf
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def __compute_hkdf(self, ikm, salt):
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""" Standard hkdf algorithm
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:param {Buffer} ikm Input key material.
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:param {Buffer} salt Salt value.
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:return {Buffer} Strong key material.
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"""
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prk = hmac.new(salt, ikm, hashlib.sha256).digest()
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info_bits_update = self.info_bits + bytearray(chr(1), 'utf-8')
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hmac_hash = hmac.new(prk, info_bits_update, hashlib.sha256).digest()
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return hmac_hash[:16]
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def __calculate_u(self, big_a, big_b):
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""" Calculate the client's value U which is the hash of A and B
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:param int big_a: Large A value.
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:param int big_b: Server B value.
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:return Computed U value.
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:rtype: int
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"""
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u_hex_hash = self.__hex_hash(self.__pad_hex(big_a) + self.__pad_hex(big_b))
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return self.__hex_to_long(u_hex_hash)
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def __generate_random_small_a(self):
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""" Helper function to generate a random big integer
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:return a random value.
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:rtype: int
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"""
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random_long_int = self.__get_random(128)
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return random_long_int % self.big_n
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def __calculate_a(self):
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""" Calculate the client's public value A = g^a%N with the generated random number a
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:return Computed large A.
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:rtype: int
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"""
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big_a = pow(self.g, self.small_a_value, self.big_n)
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# safety check
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if (big_a % self.big_n) == 0:
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raise ValueError('Safety check for A failed')
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return big_a
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@staticmethod
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def __long_to_hex(long_num):
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return '%x' % long_num
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@staticmethod
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def __hex_to_long(hex_string):
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return int(hex_string, 16)
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@staticmethod
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def __hex_hash(hex_string):
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return AwsIdp.__hash_sha256(bytearray.fromhex(hex_string))
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@staticmethod
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def __hash_sha256(buf):
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"""AuthenticationHelper.hash"""
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a = hashlib.sha256(buf).hexdigest()
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return (64 - len(a)) * '0' + a
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@staticmethod
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def __pad_hex(long_int):
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""" Converts a Long integer (or hex string) to hex format padded with zeroes for hashing
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:param int|str long_int: Number or string to pad.
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:return Padded hex string.
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:rtype: str
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"""
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# noinspection PyTypeChecker
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if not isinstance(long_int, six.string_types):
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hash_str = AwsIdp.__long_to_hex(long_int)
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else:
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hash_str = long_int
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if len(hash_str) % 2 == 1:
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hash_str = '0%s' % hash_str
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elif hash_str[0] in '89ABCDEFabcdef':
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hash_str = '00%s' % hash_str
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return hash_str
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@staticmethod
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def __get_random(nbytes):
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random_hex = binascii.hexlify(os.urandom(nbytes))
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return AwsIdp.__hex_to_long(random_hex)
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@staticmethod
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def __get_current_timestamp():
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""" Creates a timestamp with the correct English format.
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:return: timestamp in format 'Sun Jan 27 19:00:04 UTC 2019'
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:rtype: str
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"""
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# We need US only data, so we cannot just do a strftime:
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# Sun Jan 27 19:00:04 UTC 2019
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months = [None, 'Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
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days = ['Mon', 'Tue', 'Wed', 'Thu', 'Fri', 'Sat', 'Sun']
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time_now = datetime.datetime.utcnow()
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if sys.platform.startswith('win'):
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format_string = "{} {} %#d %H:%M:%S UTC %Y".format(days[time_now.weekday()], months[time_now.month])
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else:
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format_string = "{} {} %-d %H:%M:%S UTC %Y".format(days[time_now.weekday()], months[time_now.month])
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time_string = datetime.datetime.utcnow().strftime(format_string)
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_LOGGER.debug("AWS Auth Timestamp: %s", time_string)
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return time_string
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def __str__(self):
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return "AWS IDP Client for:\nRegion: %s\nPoolId: %s\nAppId: %s" % (
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self.region, self.pool_id.split("_")[1], self.client_id
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)
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