add MagicKey datastore model

models.py

@@ -0,0 +1,41 @@
+"""Datastore model classes.
+
+Based on webfinger-unofficial/user.py.
+"""
+from django_salmon import magicsigs
+from google.appengine.ext import ndb
+from oauth_dropins.webutil.models import StringIdModel
+
+
+class MagicKey(StringIdModel):
+  """Stores a user's public/private key pair used for Magic Signatures.
+
+  The key name is USERNAME@DOMAIN.
+
+  The modulus and exponent properties are all encoded as base64url (ie URL-safe
+  base64) strings as described in RFC 4648 and section 5.1 of the Magic
+  Signatures spec.
+
+  Magic Signatures are used to sign Salmon slaps. Details:
+  http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-magicsig-01.html
+  http://salmon-protocol.googlecode.com/svn/trunk/draft-panzer-salmon-00.html
+  """
+  mod = ndb.StringProperty(required=True)
+  public_exponent = ndb.StringProperty(required=True)
+  private_exponent = ndb.StringProperty(required=True)
+
+  @staticmethod
+  @ndb.transactional
+  def get_or_create(uri):
+    """Loads and returns a MagicKey from the datastore. Creates it if necessary."""
+    key = MagicKey.get_by_id(uri)
+
+    if not key:
+      # this uses urandom(), and does some nontrivial math, so it can take a
+      # while depending on the amount of randomness available on the system.
+      pubexp, mod, privexp = magicsigs.generate()
+      key = MagicKey(id=uri, mod=mod, public_exponent=pubexp,
+                     private_exponent=privexp)
+      key.put()
+
+    return key

test/test_models.py

@@ -0,0 +1,30 @@
+# coding=utf-8
+"""Unit tests for models.py."""
+import unittest
+
+from google.appengine.datastore import datastore_stub_util
+from google.appengine.ext import testbed
+
+import models
+
+
+class ModelsTest(unittest.TestCase):
+
+    def setUp(self):
+        self.testbed = testbed.Testbed()
+        self.testbed.activate()
+        hrd_policy = datastore_stub_util.PseudoRandomHRConsistencyPolicy(probability=.5)
+        self.testbed.init_datastore_v3_stub(consistency_policy=hrd_policy)
+        self.testbed.init_memcache_stub()
+
+    def tearDown(self):
+        self.testbed.deactivate()
+
+    def test_magic_key_get_or_create(self):
+        key = models.MagicKey.get_or_create('x@y.z')
+        assert key.mod
+        assert key.public_exponent
+        assert key.private_exponent
+
+        same = models.MagicKey.get_or_create('x@y.z')
+        self.assertEquals(same, key)