Basic itsdangerous infrastructure.

Implement the basic infrastructure for using itsdangerous
in mediagoblin. Usage instructions will follow.

mediagoblin/app.py

@@ -36,6 +36,7 @@ from mediagoblin.init import (get_jinja_loader, get_staticdirector,
     setup_global_and_app_config, setup_locales, setup_workbench, setup_database,
     setup_storage, setup_beaker_cache)
 from mediagoblin.tools.pluginapi import PluginManager
+from mediagoblin.tools.crypto import setup_crypto
 
 
 _log = logging.getLogger(__name__)
@@ -66,6 +67,8 @@ class MediaGoblinApp(object):
         # Open and setup the config
         global_config, app_config = setup_global_and_app_config(config_path)
 
+        setup_crypto()
+
         ##########################################
         # Setup other connections / useful objects
         ##########################################

mediagoblin/config_spec.ini

@@ -14,6 +14,9 @@ sql_engine = string(default="sqlite:///%(here)s/mediagoblin.db")
 # Where temporary files used in processing and etc are kept
 workbench_path = string(default="%(here)s/user_dev/media/workbench")
 
+# Where to store cryptographic sensible data
+crypto_path = string(default="%(here)s/user_dev/crypto")
+
 # Where mediagoblin-builtin static assets are kept
 direct_remote_path = string(default="/mgoblin_static/")
 

mediagoblin/tools/crypto.py

@@ -0,0 +1,55 @@
+# GNU MediaGoblin -- federated, autonomous media hosting
+# Copyright (C) 2013 MediaGoblin contributors.  See AUTHORS.
+#
+# This program is free software: you can redistribute it and/or modify
+# it under the terms of the GNU Affero General Public License as published by
+# the Free Software Foundation, either version 3 of the License, or
+# (at your option) any later version.
+#
+# This program is distributed in the hope that it will be useful,
+# but WITHOUT ANY WARRANTY; without even the implied warranty of
+# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+# GNU Affero General Public License for more details.
+#
+# You should have received a copy of the GNU Affero General Public License
+# along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+import os.path
+import logging
+import random
+import itsdangerous
+from mediagoblin import mg_globals
+
+_log = logging.getLogger(__name__)
+
+
+# Use the system (hardware-based) random number generator if it exists.
+# -- this optimization is lifted from Django
+if hasattr(random, 'SystemRandom'):
+    getrandbits = random.SystemRandom().getrandbits
+else:
+    getrandbits = random.getrandbits
+
+
+__itsda_secret = None
+
+
+def setup_crypto():
+    global __itsda_secret
+    dir = mg_globals.app_config["crypto_path"]
+    if not os.path.isdir(dir):
+        _log.info("Creating %s", dir)
+        os.makedirs(dir)
+    name = os.path.join(dir, "itsdangeroussecret.bin")
+    if os.path.exists(name):
+        __itsda_secret = file(name, "r").read()
+    else:
+        __itsda_secret = str(getrandbits(192))
+        file(name, "w").write(__itsda_secret)
+        _log.info("Created %s", name)
+
+
+def get_timed_signer_url(namespace):
+    assert __itsda_secret is not None
+    return itsdangerous.URLSafeTimedSerializer(__itsda_secret,
+         salt=namespace)