samples: add v4 signed policy sample (#1116)

* add v4 signed policy sample

* fix comments

* nit: v4 signed policy

* use updated method name

* add test

* fixy

* fixy

* fix assert

* copy: file to create

* use string concat instead of console.log each line

* const => let

* fix

Co-authored-by: Jonathan Lui <jonathanlui@google.com>

samples/generateV4SignedPolicy.js

@@ -0,0 +1,69 @@
+// 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.
+
+/**
+ * This application demonstrates how to perform basic operations on files with
+ * the Google Cloud Storage API.
+ *
+ * For more information, see the README.md under /storage and the documentation
+ * at https://cloud.google.com/storage/docs.
+ */
+
+function main(bucketName = 'my-bucket', filename = 'test.txt') {
+  // [START storage_generate_post_policy_url_v4]
+  /**
+   * TODO(developer): Uncomment the following lines before running the sample.
+   */
+  // const bucketName = 'Name of a bucket, e.g. my-bucket';
+  // const filename = 'File to access, e.g. file.txt';
+
+  // Imports the Google Cloud client library
+  const {Storage} = require('@google-cloud/storage');
+
+  // Creates a client
+  const storage = new Storage();
+
+  async function generateV4SignedPolicy() {
+    const bucket = storage.bucket(bucketName);
+    const file = bucket.file(filename);
+
+    // These options will allow temporary uploading of a file
+    // through an HTML form.
+    const expires = Date.now() + 10 * 60 * 1000; //  10 minutes
+    const options = {
+      expires,
+      fields: {'x-goog-meta-test': 'data'},
+    };
+
+    // Get a v4 signed policy for uploading file
+    const [response] = await file.generateSignedPostPolicyV4(options);
+
+    // Create an HTML form with the provided policy
+    let output = `<form action='${response.url}' method='POST' enctype="multipart/form-data">\n`;
+    // Include all fields returned in the HTML form as they're required
+    for (const name of Object.keys(response.fields)) {
+      const value = response.fields[name];
+      output += `  <input name='${name}' value='${value}' type='hidden'/>\n`;
+    }
+    output += "  <input type='file' name='file'/>\n";
+    output += "  <input type='submit' value='Upload File' name='submit'/>\n";
+    output += '</form>';
+
+    console.log(output);
+  }
+
+  generateV4SignedPolicy().catch(console.error);
+  // [END storage_generate_post_policy_url_v4]
+}
+main(...process.argv.slice(2));

samples/system-test/files.test.js

@@ -240,6 +240,28 @@ it('should generate a v4 signed URL and upload a file', async () => {
   });
 });
 
+it('should generate a v4 signed policy', async () => {
+  const output = execSync(
+    `node generateV4SignedPolicy.js ${bucketName} ${signedFileName}`
+  );
+
+  assert.include(
+    output,
+    `<form action='https://storage.googleapis.com/${bucketName}/`
+  );
+  assert.include(output, `<input name='key' value='${signedFileName}'`);
+  assert.include(output, "<input name='x-goog-signature'");
+  assert.include(output, "<input name='x-goog-date'");
+  assert.include(output, "<input name='x-goog-credential'");
+  assert.include(
+    output,
+    "<input name='x-goog-algorithm' value='GOOG4-RSA-SHA256'"
+  );
+  assert.include(output, "<input name='policy'");
+  assert.include(output, "<input name='x-goog-meta-test' value='data'");
+  assert.include(output, "<input type='file' name='file'/>");
+});
+
 it('should get metadata for a file', () => {
   const output = execSync(
     `node getMetadata.js ${bucketName} ${copiedFileName}`