2 files changed, 37 insertions, 1 deletions
diff --git a/packages/browser/src/helpers/toUint8Array.ts b/packages/browser/src/helpers/toUint8Array.ts
index ed4aa5d..1855dd7 100644
--- a/packages/browser/src/helpers/toUint8Array.ts
+++ b/packages/browser/src/helpers/toUint8Array.ts
@@ -1,7 +1,9 @@
+const utf8Encoder = new TextEncoder();
+
 /**
  * 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));
+  return utf8Encoder.encode(value);
 }
diff --git a/packages/browser/src/methods/startAssertion.test.ts b/packages/browser/src/methods/startAssertion.test.ts
index 669e8eb..e919d18 100644
--- a/packages/browser/src/methods/startAssertion.test.ts
+++ b/packages/browser/src/methods/startAssertion.test.ts
@@ -17,6 +17,7 @@ const mockClientDataJSON = 'mockClientDataJSON';
 const mockSignature = 'mockSignature';
 const mockUserHandle = 'mockUserHandle';
 
+// With ASCII challenge
 const goodOpts1: PublicKeyCredentialRequestOptionsJSON = {
   challenge: 'fizz',
   allowCredentials: [
@@ -29,6 +30,13 @@ const goodOpts1: PublicKeyCredentialRequestOptionsJSON = {
   timeout: 1,
 };
 
+// With UTF-8 challenge
+const goodOpts2UTF8: PublicKeyCredentialRequestOptionsJSON = {
+  challenge: 'やれやれだぜ',
+  allowCredentials: [],
+  timeout: 1,
+};
+
 beforeEach(() => {
   mockNavigatorGet.mockReset();
   mockSupportsWebauthn.mockReset();
@@ -120,3 +128,29 @@ test('should throw error if assertion is cancelled for some reason', async done
 
   done();
 });
+
+test('should handle UTF-8 challenges', async done => {
+  mockSupportsWebauthn.mockReturnValue(true);
+
+  // Stub out a response so the method won't throw
+  mockNavigatorGet.mockImplementation(
+    (): Promise<any> => {
+      return new Promise(resolve => {
+        resolve({
+          response: {},
+          getClientExtensionResults: () => ({}),
+        });
+      });
+    },
+  );
+
+  await startAssertion(goodOpts2UTF8);
+
+  const argsPublicKey = mockNavigatorGet.mock.calls[0][0].publicKey;
+
+  expect(JSON.stringify(argsPublicKey.challenge)).toEqual(
+    '{"0":227,"1":130,"2":132,"3":227,"4":130,"5":140,"6":227,"7":130,"8":132,"9":227,"10":130,"11":140,"12":227,"13":129,"14":160,"15":227,"16":129,"17":156}',
+  );
+
+  done();
+});