fix(v4-policy): encode special characters

conformance-test/v4SignedUrl.ts

@@ -220,16 +220,15 @@ describe('v4 conformance test', () => {
 
         assert.strictEqual(policy.url, testCase.policyOutput.url);
         const outputFields = testCase.policyOutput.fields;
-        const decodedPolicy = Buffer.from(
-          policy.fields.policy,
-          'base64'
-        ).toString();
+        const decodedPolicy = JSON.parse(
+          Buffer.from(policy.fields.policy, 'base64').toString()
+        );
         assert.deepStrictEqual(
           decodedPolicy,
-          testCase.policyOutput.expectedDecodedPolicy
+          JSON.parse(testCase.policyOutput.expectedDecodedPolicy)
         );
 
-        assert.deepStrictEqual(outputFields, testCase.policyOutput.fields);
+        assert.deepStrictEqual(policy.fields, outputFields);
 
         fakeTimer.restore();
       });

src/file.ts

@@ -63,7 +63,7 @@ import {
 } from '@google-cloud/common/build/src/util';
 // eslint-disable-next-line @typescript-eslint/no-var-requires
 const duplexify: DuplexifyConstructor = require('duplexify');
-import {normalize, objectKeyToLowercase} from './util';
+import {normalize, objectKeyToLowercase, unicodeJSONStringify} from './util';
 import {GaxiosError, Headers, request as gaxiosRequest} from 'gaxios';
 
 export type GetExpirationDateResponse = [Date];
@@ -2611,7 +2611,7 @@ class File extends ServiceObject<File> {
         expiration,
       };
 
-      const policyString = JSON.stringify(policy);
+      const policyString = unicodeJSONStringify(policy);
       const policyBase64 = Buffer.from(policyString).toString('base64');
 
       try {

src/util.ts

@@ -90,3 +90,16 @@ export function objectKeyToLowercase<T>(object: {[key: string]: T}) {
   }
   return newObj;
 }
+
+/**
+ * JSON encode str, with unicode \u+ representation.
+ * @param {object} obj The object to encode.
+ * @return {string} Serialized string.
+ */
+export function unicodeJSONStringify(obj: object) {
+  return JSON.stringify(obj).replace(
+    /[\u0080-\uFFFF]/g,
+    (char: string) =>
+      '\\u' + ('0000' + char.charCodeAt(0).toString(16)).slice(-4)
+  );
+}

test/file.ts

@@ -2941,6 +2941,30 @@ describe('File', () => {
       );
     });
 
+    it('should encode special characters in policy', done => {
+      CONFIG = {
+        fields: {
+          'x-goog-meta-foo': 'bår',
+        },
+        ...CONFIG,
+      };
+
+      file.generateSignedPostPolicyV4(
+        CONFIG,
+        (err: Error, res: SignedPostPolicyV4Output) => {
+          assert.ifError(err);
+
+          assert.strictEqual(res.fields['x-goog-meta-foo'], 'bår');
+          const decodedPolicy = Buffer.from(
+            res.fields.policy,
+            'base64'
+          ).toString('utf-8');
+          assert(decodedPolicy.includes('"x-goog-meta-foo":"b\\u00e5r"'));
+          done();
+        }
+      );
+    });
+
     it('should not include fields with x-ignore- prefix in conditions', done => {
       CONFIG = {
         fields: {