Add an example for IAP on GCE (#1099)

iap/example_gce_backend.py

@@ -0,0 +1,42 @@
+# Copyright 2017 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.
+
+import platform
+
+import flask
+
+import validate_jwt
+
+CLOUD_PROJECT_ID = 'YOUR_PROJECT_ID'
+BACKEND_SERVICE_ID = 'YOUR_BACKEND_SERVICE_ID'
+
+app = flask.Flask(__name__)
+
+
+@app.route('/')
+def root():
+    jwt = flask.request.headers.get('x-goog-iap-jwt-assertion')
+    if jwt is None:
+        return 'Unauthorized request.'
+    user_id, user_email, error_str = (
+        validate_jwt.validate_iap_jwt_from_compute_engine(
+            jwt, CLOUD_PROJECT_ID, BACKEND_SERVICE_ID))
+    if error_str:
+        return 'Error: {}'.format(error_str)
+    else:
+        return 'Hi, {}. I am {}.'.format(user_email, platform.node())
+
+
+if __name__ == '__main__':
+    app.run()

iap/requirements.txt

@@ -1,5 +1,7 @@
 PyJWT==1.5.3
 cryptography==2.0.3
+flask==0.12.2
 google-auth==1.1.0
+gunicorn==19.7.1
 requests==2.18.4
 requests_toolbelt==0.8.0