Add toPublicKeyCredentialDescriptor browser helper

1 files changed, 16 insertions, 0 deletions

diff --git a/packages/browser/src/helpers/toPublicKeyCredentialDescriptor.ts b/packages/browser/src/helpers/toPublicKeyCredentialDescriptor.ts
new file mode 100644
index 0000000..ad166a5
--- /dev/null
+++ b/packages/browser/src/helpers/toPublicKeyCredentialDescriptor.ts
@@ -0,0 +1,16 @@
+import base64js from 'base64-js';
+import type { PublicKeyCredentialDescriptorJSON } from '@webauthntine/typescript-types';
+
+export default function toPublicKeyCredentialDescriptor(
+  descriptor: PublicKeyCredentialDescriptorJSON,
+): PublicKeyCredentialDescriptor {
+  // Make sure the Base64'd credential ID length is a multiple of 4 or else toByteArray will throw
+  const { id } = descriptor;
+  const padLength = 4 - (id.length % 4);
+  const paddedId = id.padEnd(id.length + padLength, '=');
+
+  return {
+    ...descriptor,
+    id: base64js.toByteArray(paddedId),
+  };
+}