2 files changed, 54 insertions, 1 deletions
diff --git a/packages/browser/src/methods/startAssertion.test.ts b/packages/browser/src/methods/startAssertion.test.ts
index 996f66a..c74b88f 100644
--- a/packages/browser/src/methods/startAssertion.test.ts
+++ b/packages/browser/src/methods/startAssertion.test.ts
@@ -72,6 +72,52 @@ test('should convert options before passing to navigator.credentials.get(...)',
   done();
 });
 
+test('should support optional allowCredential', async () => {
+  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({
+    challenge: bufferToBase64URLString(toUint8Array('fizz')),
+    timeout: 1,
+  });
+
+  expect(mockNavigatorGet.mock.calls[0][0].allowCredentials).toEqual(undefined);
+});
+
+test('should convert allow allowCredential to undefined when empty', async () => {
+  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({
+    challenge: bufferToBase64URLString(toUint8Array('fizz')),
+    timeout: 1,
+    allowCredentials: [],
+  });
+  expect(mockNavigatorGet.mock.calls[0][0].allowCredentials).toEqual(undefined);
+});
+
 test('should return base64url-encoded response values', async done => {
   mockSupportsWebauthn.mockReturnValue(true);
 
diff --git a/packages/browser/src/methods/startAssertion.ts b/packages/browser/src/methods/startAssertion.ts
index 09e416f..e02e577 100644
--- a/packages/browser/src/methods/startAssertion.ts
+++ b/packages/browser/src/methods/startAssertion.ts
@@ -21,11 +21,18 @@ export default async function startAssertion(
     throw new Error('WebAuthn is not supported in this browser');
   }
 
+  // We need to avoid passing empty array to avoid blocking retrieval
+  // of public key
+  let allowCredentials;
+  if (requestOptionsJSON.allowCredentials?.length !== 0) {
+    allowCredentials = requestOptionsJSON.allowCredentials?.map(toPublicKeyCredentialDescriptor);
+  }
+
   // We need to convert some values to Uint8Arrays before passing the credentials to the navigator
   const publicKey: PublicKeyCredentialRequestOptions = {
     ...requestOptionsJSON,
     challenge: base64URLStringToBuffer(requestOptionsJSON.challenge),
-    allowCredentials: requestOptionsJSON.allowCredentials.map(toPublicKeyCredentialDescriptor),
+    allowCredentials,
   };
 
   // Wait for the user to complete assertion