Add google-endpoints to third_party/.

third_party/google-endpoints/oauth2client/xsrfutil.py

+#
+# Copyright 2014 the Melange authors.
+#
+# 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.
+
+"""Helper methods for creating & verifying XSRF tokens."""
+
+import base64
+import binascii
+import hmac
+import time
+
+from oauth2client._helpers import _to_bytes
+from oauth2client import util
+
+__authors__ = [
+    '"Doug Coker" <dcoker@google.com>',
+    '"Joe Gregorio" <jcgregorio@google.com>',
+]
+
+# Delimiter character
+DELIMITER = b':'
+
+# 1 hour in seconds
+DEFAULT_TIMEOUT_SECS = 60 * 60
+
+
+@util.positional(2)
+def generate_token(key, user_id, action_id='', when=None):
+    """Generates a URL-safe token for the given user, action, time tuple.
+
+    Args:
+        key: secret key to use.
+        user_id: the user ID of the authenticated user.
+        action_id: a string identifier of the action they requested
+                   authorization for.
+        when: the time in seconds since the epoch at which the user was
+              authorized for this action. If not set the current time is used.
+
+    Returns:
+        A string XSRF protection token.
+    """
+    digester = hmac.new(_to_bytes(key, encoding='utf-8'))
+    digester.update(_to_bytes(str(user_id), encoding='utf-8'))
+    digester.update(DELIMITER)
+    digester.update(_to_bytes(action_id, encoding='utf-8'))
+    digester.update(DELIMITER)
+    when = _to_bytes(str(when or int(time.time())), encoding='utf-8')
+    digester.update(when)
+    digest = digester.digest()
+
+    token = base64.urlsafe_b64encode(digest + DELIMITER + when)
+    return token
+
+
+@util.positional(3)
+def validate_token(key, token, user_id, action_id="", current_time=None):
+    """Validates that the given token authorizes the user for the action.
+
+    Tokens are invalid if the time of issue is too old or if the token
+    does not match what generateToken outputs (i.e. the token was forged).
+
+    Args:
+        key: secret key to use.
+        token: a string of the token generated by generateToken.
+        user_id: the user ID of the authenticated user.
+        action_id: a string identifier of the action they requested
+                   authorization for.
+
+    Returns:
+        A boolean - True if the user is authorized for the action, False
+        otherwise.
+    """
+    if not token:
+        return False
+    try:
+        decoded = base64.urlsafe_b64decode(token)
+        token_time = int(decoded.split(DELIMITER)[-1])
+    except (TypeError, ValueError, binascii.Error):
+        return False
+    if current_time is None:
+        current_time = time.time()
+    # If the token is too old it's not valid.
+    if current_time - token_time > DEFAULT_TIMEOUT_SECS:
+        return False
+
+    # The given token should match the generated one with the same time.
+    expected_token = generate_token(key, user_id, action_id=action_id,
+                                    when=token_time)
+    if len(token) != len(expected_token):
+        return False
+
+    # Perform constant time comparison to avoid timing attacks
+    different = 0
+    for x, y in zip(bytearray(token), bytearray(expected_token)):
+        different |= x ^ y
+    return not different