Add GCF bearer auth sample

functions/security/index.js

@@ -0,0 +1,52 @@
+// Copyright 2020 Google LLC
+//
+// 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.
+
+'use strict';
+
+// [START functions_bearer_token]
+const {get} = require('axios');
+
+// TODO<developer>: set these values
+const REGION = 'us-central1';
+const PROJECT_ID = 'nodejs-docs-samples';
+const RECEIVING_FUNCTION = 'myFunction';
+
+// Constants for setting up metadata server request
+// See https://cloud.google.com/compute/docs/instances/verifying-instance-identity#request_signature
+const functionURL = `https://${REGION}-${PROJECT_ID}.cloudfunctions.net/${RECEIVING_FUNCTION}`;
+const metadataServerURL =
+  'http://metadata/computeMetadata/v1/instance/service-accounts/default/identity?audience=';
+const tokenUrl = metadataServerURL + functionURL;
+
+exports.bearerToken = async (req, res) => {
+  // Fetch the token
+  const tokenResponse = await get(tokenUrl, {
+    headers: {
+      'Metadata-Flavor': 'Google',
+    },
+  });
+  const token = tokenResponse.data;
+
+  // Provide the token in the request to the receiving function
+  try {
+    const functionResponse = await get(functionURL, {
+      headers: {Authorization: `bearer ${token}`},
+    });
+    res.status(200).send(functionResponse.data);
+  } catch (err) {
+    console.error(err);
+    res.status(500).send('An error occurred! See logs for more details.');
+  }
+};
+// [END functions_bearer_token]