Add XSRF protection to oauth2decorator callback.
Also update all samples to use XSRF callback protection.
Reviewed in https://codereview.appspot.com/6473053/.
diff --git a/oauth2client/xsrfutil.py b/oauth2client/xsrfutil.py
new file mode 100644
index 0000000..7d5fdbe
--- /dev/null
+++ b/oauth2client/xsrfutil.py
@@ -0,0 +1,106 @@
+#!/usr/bin/python2.5
+#
+# Copyright 2010 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."""
+
+__authors__ = [
+ '"Doug Coker" <dcoker@google.com>',
+ '"Joe Gregorio" <jcgregorio@google.com>',
+]
+
+
+import base64
+import hmac
+import os # for urandom
+import time
+
+from oauth2client import util
+
+
+# Delimiter character
+DELIMITER = ':'
+
+# 1 hour in seconds
+DEFAULT_TIMEOUT_SECS = 1*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.
+ """
+ when = when or int(time.time())
+ digester = hmac.new(key)
+ digester.update(str(user_id))
+ digester.update(DELIMITER)
+ digester.update(action_id)
+ digester.update(DELIMITER)
+ digester.update(str(when))
+ digest = digester.digest()
+
+ token = base64.urlsafe_b64encode('%s%s%d' % (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(str(token))
+ token_time = long(decoded.split(DELIMITER)[-1])
+ except (TypeError, ValueError):
+ 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 token != expected_token:
+ return False
+
+ return True