Merge pull request #63 from stax-labs/feat_less_dependencies

feat(sdk): remove warrant dependency to remove native dependencies

requirements.txt

@@ -1,11 +1,14 @@
 black
 isort
 jsonschema
-pyjwt
 nose2
 prance
 pycodestyle
 pylint
 pytest
 pytest-cov
 responses
+pyjwt==1.7.1
+boto3
+aws_requests_auth
+openapi-spec-validator

setup.py

@@ -7,8 +7,6 @@
     "prance",
     "requests",
     "aws_requests_auth",
-    "warrant",
-    "pyjwt",
     "openapi-spec-validator",
 ]
 

staxapp/auth.py

@@ -6,8 +6,8 @@
 from botocore import UNSIGNED
 from botocore.client import Config as BotoConfig
 from botocore.exceptions import ClientError
-from warrant import AWSSRP
 
+from staxapp.aws_srp import AWSSRP
 from staxapp.config import Config as StaxConfig
 from staxapp.exceptions import InvalidCredentialsException
 

staxapp/aws_srp.py

@@ -0,0 +1,293 @@
+"""
+   Copyright 2021 Brian Jinwright <opensource@capless.io>
+
+   Licensed under the Apache License, Version 2.0 (the "License");
+   you may not use this file except in compliance with the License.
+   You may obtain a copy of the License at
+
+       http://www.apache.org/licenses/LICENSE-2.0
+
+   Unless required by applicable law or agreed to in writing, software
+   distributed under the License is distributed on an "AS IS" BASIS,
+   WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+   See the License for the specific language governing permissions and
+   limitations under the License.
+
+   Imported from https://github.com/capless/warrant to reduce external dependencies required by this library and just
+   use the SRP functions.
+"""
+
+import base64
+import binascii
+import datetime
+import hashlib
+import hmac
+import os
+import re
+
+import boto3
+import six
+
+
+class WarrantException(Exception):
+    """Base class for all Warrant exceptions"""
+
+
+class ForceChangePasswordException(WarrantException):
+    """Raised when the user is forced to change their password"""
+
+
+# https://github.com/aws/amazon-cognito-identity-js/blob/master/src/AuthenticationHelper.js#L22
+n_hex = (
+    "FFFFFFFFFFFFFFFFC90FDAA22168C234C4C6628B80DC1CD1"
+    + "29024E088A67CC74020BBEA63B139B22514A08798E3404DD"
+    + "EF9519B3CD3A431B302B0A6DF25F14374FE1356D6D51C245"
+    + "E485B576625E7EC6F44C42E9A637ED6B0BFF5CB6F406B7ED"
+    + "EE386BFB5A899FA5AE9F24117C4B1FE649286651ECE45B3D"
+    + "C2007CB8A163BF0598DA48361C55D39A69163FA8FD24CF5F"
+    + "83655D23DCA3AD961C62F356208552BB9ED529077096966D"
+    + "670C354E4ABC9804F1746C08CA18217C32905E462E36CE3B"
+    + "E39E772C180E86039B2783A2EC07A28FB5C55DF06F4C52C9"
+    + "DE2BCBF6955817183995497CEA956AE515D2261898FA0510"
+    + "15728E5A8AAAC42DAD33170D04507A33A85521ABDF1CBA64"
+    + "ECFB850458DBEF0A8AEA71575D060C7DB3970F85A6E1E4C7"
+    + "ABF5AE8CDB0933D71E8C94E04A25619DCEE3D2261AD2EE6B"
+    + "F12FFA06D98A0864D87602733EC86A64521F2B18177B200C"
+    + "BBE117577A615D6C770988C0BAD946E208E24FA074E5AB31"
+    + "43DB5BFCE0FD108E4B82D120A93AD2CAFFFFFFFFFFFFFFFF"
+)
+# https://github.com/aws/amazon-cognito-identity-js/blob/master/src/AuthenticationHelper.js#L49
+g_hex = "2"
+info_bits = bytearray("Caldera Derived Key", "utf-8")
+
+
+def hash_sha256(buf):
+    """AuthenticationHelper.hash"""
+    a = hashlib.sha256(buf).hexdigest()
+    return (64 - len(a)) * "0" + a
+
+
+def hex_hash(hex_string):
+    return hash_sha256(bytearray.fromhex(hex_string))
+
+
+def hex_to_long(hex_string):
+    return int(hex_string, 16)
+
+
+def long_to_hex(long_num):
+    return "%x" % long_num
+
+
+def get_random(nbytes):
+    random_hex = binascii.hexlify(os.urandom(nbytes))
+    return hex_to_long(random_hex)
+
+
+def pad_hex(long_int):
+    """
+    Converts a Long integer (or hex string) to hex format padded with zeroes for hashing
+    :param {Long integer|String} long_int Number or string to pad.
+    :return {String} Padded hex string.
+    """
+    if not isinstance(long_int, six.string_types):
+        hash_str = long_to_hex(long_int)
+    else:
+        hash_str = long_int
+    if len(hash_str) % 2 == 1:
+        hash_str = "0%s" % hash_str
+    elif hash_str[0] in "89ABCDEFabcdef":
+        hash_str = "00%s" % hash_str
+    return hash_str
+
+
+def compute_hkdf(ikm, salt):
+    """
+    Standard hkdf algorithm
+    :param {Buffer} ikm Input key material.
+    :param {Buffer} salt Salt value.
+    :return {Buffer} Strong key material.
+    @private
+    """
+    prk = hmac.new(salt, ikm, hashlib.sha256).digest()
+    info_bits_update = info_bits + bytearray(chr(1), "utf-8")
+    hmac_hash = hmac.new(prk, info_bits_update, hashlib.sha256).digest()
+    return hmac_hash[:16]
+
+
+def calculate_u(big_a, big_b):
+    """
+    Calculate the client's value U which is the hash of A and B
+    :param {Long integer} big_a Large A value.
+    :param {Long integer} big_b Server B value.
+    :return {Long integer} Computed U value.
+    """
+    u_hex_hash = hex_hash(pad_hex(big_a) + pad_hex(big_b))
+    return hex_to_long(u_hex_hash)
+
+
+class AWSSRP(object):
+
+    NEW_PASSWORD_REQUIRED_CHALLENGE = "NEW_PASSWORD_REQUIRED"
+    PASSWORD_VERIFIER_CHALLENGE = "PASSWORD_VERIFIER"
+
+    def __init__(
+        self,
+        username,
+        password,
+        pool_id,
+        client_id,
+        pool_region=None,
+        client=None,
+        client_secret=None,
+    ):
+        if pool_region is not None and client is not None:
+            raise ValueError(
+                "pool_region and client should not both be specified "
+                "(region should be passed to the boto3 client instead)"
+            )
+
+        self.username = username
+        self.password = password
+        self.pool_id = pool_id
+        self.client_id = client_id
+        self.client_secret = client_secret
+        self.client = (
+            client if client else boto3.client("cognito-idp", region_name=pool_region)
+        )
+        self.big_n = hex_to_long(n_hex)
+        self.g = hex_to_long(g_hex)
+        self.k = hex_to_long(hex_hash("00" + n_hex + "0" + g_hex))
+        self.small_a_value = self.generate_random_small_a()
+        self.large_a_value = self.calculate_a()
+
+    def generate_random_small_a(self):
+        """
+        helper function to generate a random big integer
+        :return {Long integer} a random value.
+        """
+        random_long_int = get_random(128)
+        return random_long_int % self.big_n
+
+    def calculate_a(self):
+        """
+        Calculate the client's public value A = g^a%N
+        with the generated random number a
+        :param {Long integer} a Randomly generated small A.
+        :return {Long integer} Computed large A.
+        """
+        big_a = pow(self.g, self.small_a_value, self.big_n)
+        # safety check
+        if (big_a % self.big_n) == 0:
+            raise ValueError("Safety check for A failed")
+        return big_a
+
+    def get_password_authentication_key(self, username, password, server_b_value, salt):
+        """
+        Calculates the final hkdf based on computed S value, and computed U value and the key
+        :param {String} username Username.
+        :param {String} password Password.
+        :param {Long integer} server_b_value Server B value.
+        :param {Long integer} salt Generated salt.
+        :return {Buffer} Computed HKDF value.
+        """
+        u_value = calculate_u(self.large_a_value, server_b_value)
+        username_password = "%s%s:%s" % (self.pool_id.split("_")[1], username, password)
+        username_password_hash = hash_sha256(username_password.encode("utf-8"))
+
+        x_value = hex_to_long(hex_hash(pad_hex(salt) + username_password_hash))
+        g_mod_pow_xn = pow(self.g, x_value, self.big_n)
+        int_value2 = server_b_value - self.k * g_mod_pow_xn
+        s_value = pow(int_value2, self.small_a_value + u_value * x_value, self.big_n)
+        hkdf = compute_hkdf(
+            bytearray.fromhex(pad_hex(s_value)),
+            bytearray.fromhex(pad_hex(long_to_hex(u_value))),
+        )
+        return hkdf
+
+    def get_auth_params(self):
+        auth_params = {
+            "USERNAME": self.username,
+            "SRP_A": long_to_hex(self.large_a_value),
+        }
+        if self.client_secret is not None:
+            auth_params.update(
+                {
+                    "SECRET_HASH": self.get_secret_hash(
+                        self.username, self.client_id, self.client_secret
+                    )
+                }
+            )
+        return auth_params
+
+    @staticmethod
+    def get_secret_hash(username, client_id, client_secret):
+        message = bytearray(username + client_id, "utf-8")
+        hmac_obj = hmac.new(bytearray(client_secret, "utf-8"), message, hashlib.sha256)
+        return base64.standard_b64encode(hmac_obj.digest()).decode("utf-8")
+
+    def process_challenge(self, challenge_parameters):
+        user_id_for_srp = challenge_parameters["USER_ID_FOR_SRP"]
+        salt_hex = challenge_parameters["SALT"]
+        srp_b_hex = challenge_parameters["SRP_B"]
+        secret_block_b64 = challenge_parameters["SECRET_BLOCK"]
+        # re strips leading zero from a day number (required by AWS Cognito)
+        timestamp = re.sub(
+            r" 0(\d) ",
+            r" \1 ",
+            datetime.datetime.utcnow().strftime("%a %b %d %H:%M:%S UTC %Y"),
+        )
+        hkdf = self.get_password_authentication_key(
+            user_id_for_srp, self.password, hex_to_long(srp_b_hex), salt_hex
+        )
+        secret_block_bytes = base64.standard_b64decode(secret_block_b64)
+        msg = (
+            bytearray(self.pool_id.split("_")[1], "utf-8")
+            + bytearray(user_id_for_srp, "utf-8")
+            + bytearray(secret_block_bytes)
+            + bytearray(timestamp, "utf-8")
+        )
+        hmac_obj = hmac.new(hkdf, msg, digestmod=hashlib.sha256)
+        signature_string = base64.standard_b64encode(hmac_obj.digest())
+        response = {
+            "TIMESTAMP": timestamp,
+            "USERNAME": user_id_for_srp,
+            "PASSWORD_CLAIM_SECRET_BLOCK": secret_block_b64,
+            "PASSWORD_CLAIM_SIGNATURE": signature_string.decode("utf-8"),
+        }
+        if self.client_secret is not None:
+            response.update(
+                {
+                    "SECRET_HASH": self.get_secret_hash(
+                        self.username, self.client_id, self.client_secret
+                    )
+                }
+            )
+        return response
+
+    def authenticate_user(self, client=None):
+        boto_client = self.client or client
+        auth_params = self.get_auth_params()
+        response = boto_client.initiate_auth(
+            AuthFlow="USER_SRP_AUTH",
+            AuthParameters=auth_params,
+            ClientId=self.client_id,
+        )
+        if response["ChallengeName"] == self.PASSWORD_VERIFIER_CHALLENGE:
+            challenge_response = self.process_challenge(response["ChallengeParameters"])
+            tokens = boto_client.respond_to_auth_challenge(
+                ClientId=self.client_id,
+                ChallengeName=self.PASSWORD_VERIFIER_CHALLENGE,
+                ChallengeResponses=challenge_response,
+            )
+
+            if tokens.get("ChallengeName") == self.NEW_PASSWORD_REQUIRED_CHALLENGE:
+                raise ForceChangePasswordException(
+                    "Change password before authenticating"
+                )
+
+            return tokens
+        else:
+            raise NotImplementedError(
+                "The %s challenge is not supported" % response["ChallengeName"]
+            )