Add method to generate user IDs

1 files changed, 21 insertions, 0 deletions

diff --git a/packages/server/src/helpers/generateUserID.ts b/packages/server/src/helpers/generateUserID.ts
new file mode 100644
index 0000000..eaf9bb0
--- /dev/null
+++ b/packages/server/src/helpers/generateUserID.ts
@@ -0,0 +1,21 @@
+import { isoCrypto } from './iso/index.ts';
+
+/**
+ * Generate a suitably random value to be used as user ID
+ */
+export async function generateUserID(): Promise<Uint8Array> {
+  /**
+   * WebAuthn spec says user.id has a max length of 64 bytes. I prefer how 32 random bytes look
+   * after they're base64url-encoded so I'm choosing to go with that here.
+   */
+  const newUserID = new Uint8Array(32);
+
+  await isoCrypto.getRandomValues(newUserID);
+
+  return _generateUserIDInternals.stubThis(newUserID);
+}
+
+// Make it possible to stub the return value during testing
+export const _generateUserIDInternals = {
+  stubThis: (value: Uint8Array) => value,
+};