Fixes #295 (#296)

* Fixes #295

* Fixing lint

* Adding test to pad public and private key

Author: Matt Gaunt

package.json

@@ -50,6 +50,7 @@
     "selenium-assistant": "1.0.0",
     "selenium-webdriver": "3.0.0-beta-2",
     "semver": "^5.1.0",
+    "sinon": "^4.0.1",
     "which": "^1.2.11"
   },
   "engines": {

src/vapid-helper.js

@@ -39,9 +39,27 @@ function generateVAPIDKeys() {
   const curve = crypto.createECDH('prime256v1');
   curve.generateKeys();
 
+  let publicKeyBuffer = curve.getPublicKey();
+  let privateKeyBuffer = curve.getPrivateKey();
+
+  // Occassionally the keys will not be padded to the correct lengh resulting
+  // in errors, hence this padding.
+  // See https://github.com/web-push-libs/web-push/issues/295 for history.
+  if (privateKeyBuffer.length < 32) {
+    const padding = new Buffer(32 - privateKeyBuffer.length);
+    padding.fill(0);
+    privateKeyBuffer = Buffer.concat([privateKeyBuffer, padding]);
+  }
+
+  if (publicKeyBuffer.length < 65) {
+    const padding = new Buffer(65 - publicKeyBuffer.length);
+    padding.fill(0);
+    publicKeyBuffer = Buffer.concat([publicKeyBuffer, padding]);
+  }
+
   return {
-    publicKey: urlBase64.encode(curve.getPublicKey()),
-    privateKey: urlBase64.encode(curve.getPrivateKey())
+    publicKey: urlBase64.encode(publicKeyBuffer),
+    privateKey: urlBase64.encode(privateKeyBuffer)
   };
 }
 

test/test-vapid-helper.js

@@ -2,6 +2,8 @@
 
 const assert = require('assert');
 const urlBase64 = require('urlsafe-base64');
+const sinon = require('sinon');
+const crypto = require('crypto');
 const webPush = require('../src/index');
 const vapidHelper = require('../src/vapid-helper');
 
@@ -13,6 +15,16 @@ const VALID_PRIVATE_KEY = urlBase64.encode(new Buffer(32));
 const VALID_EXPIRATION = Math.floor(Date.now() / 1000) + (60 * 60 * 12);
 
 suite('Test Vapid Helpers', function() {
+  const sandbox = sinon.sandbox.create();
+
+  beforeEach(function() {
+    sandbox.restore();
+  });
+
+  after(function() {
+    sandbox.restore();
+  });
+
   test('is defined', function() {
     assert(webPush.generateVAPIDKeys);
     assert(webPush.getVapidHeaders);
@@ -30,6 +42,26 @@ suite('Test Vapid Helpers', function() {
     assert.equal(urlBase64.decode(keys.publicKey).length, 65);
   });
 
+  test('generate vapid keys with padding', function() {
+    sandbox.stub(crypto, 'createECDH').callsFake(() => {
+      return {
+        generateKeys: () => {},
+        getPublicKey: () => new Buffer(60),
+        getPrivateKey: () => new Buffer(27)
+      };
+    });
+
+    const keys = webPush.generateVAPIDKeys();
+    assert(keys.privateKey);
+    assert(keys.publicKey);
+
+    assert.equal(typeof keys.privateKey, 'string');
+    assert.equal(typeof keys.publicKey, 'string');
+
+    assert.equal(urlBase64.decode(keys.privateKey).length, 32);
+    assert.equal(urlBase64.decode(keys.publicKey).length, 65);
+  });
+
   test('generate new vapid keys between calls', function() {
     const keys = webPush.generateVAPIDKeys();
     assert(keys.privateKey);