fix: handle excludeCredentials with credentials with an empty store

Author: cquintana92

passkey-authenticator/src/authenticator/make_credential.rs

@@ -32,16 +32,24 @@ where
             .filter(|list| !list.is_empty())
             .is_some()
         {
-            if let Some(excluded_credential) = self
+            // Handle the case where find_credentials returns NoCredentials error.
+            // An empty credential store should not prevent credential creation when checking
+            // the exclude list. NoCredentials simply means there are no credentials to exclude.
+            let excluded_credentials = match self
                 .store()
                 .find_credentials(
                     input.exclude_list.as_deref(),
                     &input.rp.id,
                     Some(&input.user.id),
                 )
-                .await?
-                .first()
+                .await
             {
+                Ok(creds) => creds,
+                Err(status) if status == StatusCode::from(Ctap2Error::NoCredentials) => vec![],
+                Err(e) => return Err(e),
+            };
+
+            if let Some(excluded_credential) = excluded_credentials.first() {
                 self.check_user(
                     UiHint::InformExcludedCredentialFound(excluded_credential),
                     &input.options,

passkey-authenticator/src/authenticator/make_credential/tests.rs

@@ -438,3 +438,63 @@ async fn make_credential_returns_err_when_rk_is_requested_but_not_supported() {
     // Assert
     assert_eq!(err, Ctap2Error::UnsupportedOption.into());
 }
+#[tokio::test]
+async fn empty_store_with_exclude_credentials_succeeds() {
+    // This test verifies the fix for the issue where an empty credential store
+    // would return NoCredentials error when checking excludeCredentials,
+    // causing credential creation to fail incorrectly.
+
+    let cred_id: Bytes = random_vec(16).into();
+    let request = Request {
+        exclude_list: Some(vec![webauthn::PublicKeyCredentialDescriptor {
+            ty: webauthn::PublicKeyCredentialType::PublicKey,
+            id: cred_id.clone(),
+            transports: Some(vec![webauthn::AuthenticatorTransport::Usb]),
+        }]),
+        ..good_request()
+    };
+
+    // Use an empty store - previously this would cause NoCredentials error
+    let shared_store = Arc::new(Mutex::new(MemoryStore::new()));
+    let user_mock = MockUserValidationMethod::verified_user_with_hint(
+        1,
+        MockUiHint::RequestNewCredential(request.user.clone().into(), request.rp.clone()),
+    );
+
+    let mut authenticator =
+        Authenticator::new(Aaguid::new_empty(), shared_store.clone(), user_mock);
+
+    // This should succeed - an empty store means no credentials to exclude
+    authenticator
+        .make_credential(request)
+        .await
+        .expect("make_credential should succeed with empty store and exclude_credentials");
+
+    // Verify the credential was created
+    assert_eq!(shared_store.lock().await.len(), 1);
+}
+
+#[tokio::test]
+async fn empty_exclude_credentials_with_empty_store_succeeds() {
+    // Edge case: empty exclude list with empty store should also succeed
+    let request = Request {
+        exclude_list: Some(vec![]),
+        ..good_request()
+    };
+
+    let shared_store = Arc::new(Mutex::new(MemoryStore::new()));
+    let user_mock = MockUserValidationMethod::verified_user_with_hint(
+        1,
+        MockUiHint::RequestNewCredential(request.user.clone().into(), request.rp.clone()),
+    );
+
+    let mut authenticator =
+        Authenticator::new(Aaguid::new_empty(), shared_store.clone(), user_mock);
+
+    authenticator
+        .make_credential(request)
+        .await
+        .expect("make_credential should succeed with empty exclude list");
+
+    assert_eq!(shared_store.lock().await.len(), 1);
+}