Added support for signed webhooks

See
http://help.mandrill.com/entries/23704122-Authenticating-webhook-request
s

djrill/tests/test_mandrill_webhook.py

@@ -1,3 +1,6 @@
+from base64 import b64encode
+import hashlib
+import hmac
 import json
 
 from django.test import TestCase
@@ -39,6 +42,37 @@ class DjrillWebhookSecretMixinTests(TestCase):
         self.assertEqual(response.status_code, 200)
 
 
+class DjrillWebhookSignatureMixinTests(TestCase):
+    """
+    Test mixin used in optional Mandrill webhook signature support
+    """
+
+    def setUp(self):
+        settings.DJRILL_WEBHOOK_SECRET = 'abc123'
+        settings.DJRILL_WEBHOOK_SIGNATURE_KEY = "signature"
+        settings.DJRILL_WEBHOOK_URL = "/webhook/?secret=abc123"
+
+    def test_incorrect_settings(self):
+        del settings.DJRILL_WEBHOOK_URL
+        with self.assertRaises(ImproperlyConfigured):
+            self.client.post('/webhook/?secret=abc123')
+        settings.DJRILL_WEBHOOK_URL = "/webhook/?secret=abc123"
+
+    def test_unauthorized(self):
+        settings.DJRILL_WEBHOOK_SIGNATURE_KEY = "anothersignature"
+        response = self.client.post(settings.DJRILL_WEBHOOK_URL)
+        self.assertEqual(response.status_code, 403)
+
+    def test_signature(self):
+        signature = hmac.new(key=settings.DJRILL_WEBHOOK_SIGNATURE_KEY, msg = settings.DJRILL_WEBHOOK_URL+"mandrill_events[]", digestmod=hashlib.sha1)
+        hash_string = b64encode(signature.digest())
+        response = self.client.post('/webhook/?secret=abc123', data={"mandrill_events":"[]"}, **{"X-Mandrill-Signature" : hash_string})
+        self.assertEqual(response.status_code, 200)
+
+    def tearDown(self):
+        del settings.DJRILL_WEBHOOK_SIGNATURE_KEY
+        del settings.DJRILL_WEBHOOK_URL
+
 class DjrillWebhookViewTests(TestCase):
     """
     Test optional Mandrill webhook view