packages/server/src/helpers/generateUserID.ts


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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,
};