7 files changed, 50 insertions, 21 deletions
diff --git a/packages/browser/package-lock.json b/packages/browser/package-lock.json
index 14d089e..7edf0fd 100644
--- a/packages/browser/package-lock.json
+++ b/packages/browser/package-lock.json
@@ -1,6 +1,6 @@
 {
   "name": "@webauthntine/browser",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "lockfileVersion": 1,
   "requires": true,
   "dependencies": {
@@ -185,6 +185,10 @@
         "@xtuc/long": "4.2.2"
       }
     },
+    "@webauthntine/typescript-types": {
+      "version": "file:../typescript-types",
+      "dev": true
+    },
     "@xtuc/ieee754": {
       "version": "1.2.0",
       "resolved": "https://registry.npmjs.org/@xtuc/ieee754/-/ieee754-1.2.0.tgz",
diff --git a/packages/browser/package.json b/packages/browser/package.json
index 5bb63c0..9e5862a 100644
--- a/packages/browser/package.json
+++ b/packages/browser/package.json
@@ -1,6 +1,6 @@
 {
   "name": "@webauthntine/browser",
-  "version": "0.1.1",
+  "version": "0.1.2",
   "description": "WebAuthntine for Browsers",
   "main": "dist/webauthntine-browser.min.js",
   "types": "dist/index.d.ts",
@@ -15,7 +15,7 @@
     "test": "jest",
     "test:watch": "jest --watch",
     "test:coverage": "npm test -- --coverage",
-    "prepare": "npm run build"
+    "prepublish": "npm run build"
   },
   "keywords": [
     "webauthn",
@@ -26,7 +26,7 @@
   },
   "devDependencies": {
     "@types/base64-js": "^1.2.5",
-    "@webauthntine/typescript-types": "^0.1.1",
+    "@webauthntine/typescript-types": "file:../typescript-types",
     "ts-loader": "^7.0.4",
     "webpack": "^4.43.0",
     "webpack-auto-inject-version": "^1.2.2",
diff --git a/packages/browser/src/helpers/toBase64String.test.ts b/packages/browser/src/helpers/toBase64String.test.ts
new file mode 100644
index 0000000..bbcb11b
--- /dev/null
+++ b/packages/browser/src/helpers/toBase64String.test.ts
@@ -0,0 +1,15 @@
+import toBase64String from './toBase64String';
+
+import toUint8Array from './toUint8Array';
+
+test('should convert a Buffer to a string with a length that is a multiple of 4', () => {
+  const base64 = toBase64String(Buffer.from('123456', 'ascii'));
+
+  expect(base64.length % 4).toEqual(0);
+});
+
+test('should convert a Uint8Array to a string with a length that is a multiple of 4', () => {
+  const base64 = toBase64String(toUint8Array('123456'));
+
+  expect(base64.length % 4).toEqual(0);
+});
diff --git a/packages/browser/src/helpers/toBase64String.ts b/packages/browser/src/helpers/toBase64String.ts
index 8234002..9c949be 100644
--- a/packages/browser/src/helpers/toBase64String.ts
+++ b/packages/browser/src/helpers/toBase64String.ts
@@ -4,6 +4,5 @@ export default function toBase64String(buffer: ArrayBuffer): string {
   // TODO: Make sure converting buffer to Uint8Array() is correct
   return base64js.fromByteArray(new Uint8Array(buffer))
     .replace(/\+/g, "-")
-    .replace(/\//g, "_")
-    .replace(/=/g, "");
+    .replace(/\//g, "_");
 }
diff --git a/packages/browser/src/helpers/toUint8Array.ts b/packages/browser/src/helpers/toUint8Array.ts
index a807a88..ed4aa5d 100644
--- a/packages/browser/src/helpers/toUint8Array.ts
+++ b/packages/browser/src/helpers/toUint8Array.ts
@@ -1,6 +1,6 @@
 /**
- * A helper method to convert a string sent from the server to a Uint8Array the authenticator will
- * expect.
+ * A helper method to convert an arbitrary string sent from the server to a Uint8Array the
+ * authenticator will expect.
  */
 export default function toUint8Array(value: string): Uint8Array {
   return Uint8Array.from(value, c => c.charCodeAt(0));
diff --git a/packages/browser/src/methods/startAssertion.test.ts b/packages/browser/src/methods/startAssertion.test.ts
index b069f60..4e3bb07 100644
--- a/packages/browser/src/methods/startAssertion.test.ts
+++ b/packages/browser/src/methods/startAssertion.test.ts
@@ -4,6 +4,7 @@ import { AssertionCredential, PublicKeyCredentialRequestOptionsJSON } from '@web
 
 import toUint8Array from '../helpers/toUint8Array';
 import supportsWebauthn from '../helpers/supportsWebauthn';
+import toBase64String from '../helpers/toBase64String';
 
 import startAssertion from './startAssertion';
 
@@ -12,10 +13,10 @@ jest.mock('../helpers/supportsWebauthn');
 const mockNavigatorGet = (window.navigator.credentials.get as jest.Mock);
 const mockSupportsWebauthn = (supportsWebauthn as jest.Mock);
 
-const mockAttestationObject = 'mockAsse';
-const mockClientDataJSON = 'mockClie';
-const mockSignature = 'mockSign';
-const mockUserHandle = 'mockUser';
+const mockAuthenticatorData = toBase64String(toUint8Array('mockAuthenticatorData'));
+const mockClientDataJSON = toBase64String(toUint8Array('mockClientDataJSON'));
+const mockSignature = toBase64String(toUint8Array('mockSignature'));
+const mockUserHandle = toBase64String(toUint8Array('mockUserHandle'));
 
 const goodOpts1: PublicKeyCredentialRequestOptionsJSON = {
   publicKey: {
@@ -49,9 +50,9 @@ test('should convert options before passing to navigator.credentials.get(...)',
   const argsPublicKey = mockNavigatorGet.mock.calls[0][0].publicKey;
 
   expect(argsPublicKey.challenge).toEqual(toUint8Array(goodOpts1.publicKey.challenge));
-  expect(argsPublicKey.allowCredentials[0].id).toEqual(
-    toUint8Array(goodOpts1.publicKey.allowCredentials[0].id),
-  );
+  // Make sure the credential ID is a proper base64 with a length that's a multiple of 4
+  expect(argsPublicKey.allowCredentials[0].id.length % 4).toEqual(0);
+  expect(argsPublicKey.allowCredentials[0].id).toEqual(base64js.toByteArray('credId=='));
 
   done();
 });
@@ -59,14 +60,16 @@ test('should convert options before passing to navigator.credentials.get(...)',
 test('should return base64-encoded response values', async (done) => {
   mockSupportsWebauthn.mockReturnValue(true);
 
+  const credentialID = 'foobar';
+
   mockNavigatorGet.mockImplementation((): Promise<AssertionCredential> => {
     return new Promise((resolve) => {
       resolve({
         id: 'foobar',
         rawId: toUint8Array('foobar'),
         response: {
+          authenticatorData: base64js.toByteArray(mockAuthenticatorData),
           clientDataJSON: base64js.toByteArray(mockClientDataJSON),
-          authenticatorData: base64js.toByteArray(mockClientDataJSON),
           signature: base64js.toByteArray(mockSignature),
           userHandle: base64js.toByteArray(mockUserHandle),
         },
@@ -79,7 +82,8 @@ test('should return base64-encoded response values', async (done) => {
   const response = await startAssertion(goodOpts1);
 
   expect(response).toEqual({
-    base64AuthenticatorData: mockClientDataJSON,
+    base64CredentialID: credentialID,
+    base64AuthenticatorData: mockAuthenticatorData,
     base64ClientDataJSON: mockClientDataJSON,
     base64Signature: mockSignature,
     base64UserHandle: mockUserHandle,
diff --git a/packages/browser/src/methods/startAssertion.ts b/packages/browser/src/methods/startAssertion.ts
index 603c6fb..8e411ec 100644
--- a/packages/browser/src/methods/startAssertion.ts
+++ b/packages/browser/src/methods/startAssertion.ts
@@ -3,6 +3,7 @@ import {
   AuthenticatorAssertionResponseJSON,
   AssertionCredential,
 } from '@webauthntine/typescript-types';
+import base64js from 'base64-js';
 
 import toUint8Array from '../helpers/toUint8Array';
 import toBase64String from '../helpers/toBase64String';
@@ -24,10 +25,15 @@ export default async function startAssertion(
   const publicKey: PublicKeyCredentialRequestOptions = {
     ...requestOptionsJSON.publicKey,
     challenge: toUint8Array(requestOptionsJSON.publicKey.challenge),
-    allowCredentials: requestOptionsJSON.publicKey.allowCredentials.map((cred) => ({
-      ...cred,
-      id: toUint8Array(cred.id),
-    }))
+    allowCredentials: requestOptionsJSON.publicKey.allowCredentials.map((cred) => {
+      // Make sure the credential ID length is a multiple of 4
+      let id = cred.id.padEnd(cred.id.length + (cred.id.length % 4), '=');
+
+      return {
+        ...cred,
+        id: base64js.toByteArray(id),
+      };
+    })
   };
 
   // Wait for the user to complete assertion
@@ -46,6 +52,7 @@ export default async function startAssertion(
 
   // Convert values to base64 to make it easier to send back to the server
   return {
+    base64CredentialID: credential.id,
     base64AuthenticatorData: toBase64String(response.authenticatorData),
     base64ClientDataJSON: toBase64String(response.clientDataJSON),
     base64Signature: toBase64String(response.signature),