Adding app identity blob signing example.

appengine/app_identity/signing/app.yaml

@@ -0,0 +1,11 @@
+runtime: python27
+threadsafe: yes
+api_version: 1
+
+handlers:
+- url: .*
+  script: main.app
+
+libraries:
+- name: pycrypto
+  version: latest

appengine/app_identity/signing/main.py

@@ -0,0 +1,82 @@
+# Copyright 2015 Google Inc.
+#
+# 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.
+
+"""
+Sample Google App Engine application that demonstrates usage of the app
+identity API.
+"""
+
+# [START all]
+
+import base64
+
+from Crypto.Hash import SHA256
+from Crypto.PublicKey import RSA
+from Crypto.Signature import PKCS1_v1_5
+from Crypto.Util.asn1 import DerSequence
+from google.appengine.api import app_identity
+import webapp2
+
+
+def verify_signature(data, signature, x509_certificate):
+    """Verifies a signature using the given x.509 public key certificate."""
+
+    # PyCrypto 2.6 doesn't support x.509 certificates directly, so we'll need
+    # to extract the public key from it manually.
+    # This code is based on https://github.com/google/oauth2client/blob/master
+    # /oauth2client/_pycrypto_crypt.py
+    pem_lines = x509_certificate.replace(b' ', b'').split()
+    cert_der = base64.urlsafe_b64decode(b''.join(pem_lines[1:-1]))
+    cert_seq = DerSequence()
+    cert_seq.decode(cert_der)
+    tbs_seq = DerSequence()
+    tbs_seq.decode(cert_seq[0])
+    public_key = RSA.importKey(tbs_seq[6])
+
+    signer = PKCS1_v1_5.new(public_key)
+    digest = SHA256.new(data)
+
+    return signer.verify(digest, signature)
+
+
+def verify_signed_by_app(data, signature):
+    """Checks the signature and data against all currently valid certificates
+    for the application."""
+    public_certificates = app_identity.get_public_certificates()
+
+    for cert in public_certificates:
+        if verify_signature(data, signature, cert.x509_certificate_pem):
+            return True
+
+    return False
+
+
+class MainPage(webapp2.RequestHandler):
+    def get(self):
+        message = 'Hello, world!'
+        signing_key_name, signature = app_identity.sign_blob(message)
+        verified = verify_signed_by_app(message, signature)
+
+        self.response.content_type = 'text/plain'
+        self.response.write('Message: {}\n'.format(message))
+        self.response.write(
+            'Signature: {}\n'.format(base64.b64encode(signature)))
+        self.response.write('Verified: {}\n'.format(verified))
+
+
+app = webapp2.WSGIApplication([
+    ('/', MainPage)
+], debug=True)
+
+# [END all]

appengine/app_identity/signing/main_test.py

@@ -0,0 +1,30 @@
+# Copyright 2015 Google Inc. All rights reserved.
+#
+# 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.
+
+from tests import AppEngineTestbedCase
+import webtest
+
+from . import main
+
+
+class TestAppIdentityHandler(AppEngineTestbedCase):
+    def setUp(self):
+        super(TestAppIdentityHandler, self).setUp()
+
+        self.app = webtest.TestApp(main.app)
+
+    def test_get(self):
+        response = self.app.get('/')
+        self.assertEqual(response.status_int, 200)
+        self.assertTrue('Verified: True' in response.text)

tests/utils.py

@@ -88,6 +88,7 @@ def setUp(self):
         self.testbed.init_memcache_stub()
 
         # Setup remaining stubs.
+        self.testbed.init_app_identity_stub()
         self.testbed.init_blobstore_stub()
         self.testbed.init_user_stub()
         self.testbed.init_taskqueue_stub(root_path='tests/resources')