WebAuthn Advanced Usage Example

Below is a more comprehensive Delphi example that demonstrates custom endpoints, challenge policies, database-backed credential storage, FIDO Metadata validation, and cross-origin iframe support. The code highlights advanced event handling to enforce security policies. 

1. Challenge Hardening – By expanding the challenge size and using a cryptographically secure RNG, replay attacks are further mitigated.
2. Custom User Handles – Assigning a unique binary user handle allows the authenticator to store a privacy-preserving identifier independent of usernames.
3. Metadata-Based Attestation Validation – The ValidateAttestationWithMDS routine cross-checks authenticator model, status reports, and revocation lists, ensuring only trusted devices are registered.
4. Sign Counter Enforcement – AuthnVerify rejects responses that do not strictly increment the authenticator's counter, detecting cloned credentials.
5. Database Integration – Credential data, sign counters, and session tokens are stored and updated via external persistence functions, demonstrating how to integrate the component with a real-world backend.
6. Cross-Origin Iframe Support – Enabled through AllowCrossOrigins and configured TopOrigins, allowing WebAuthn flows initiated from embedded frames (e.g., login widget on different domain).
7. Attestation Policy – Direct attestation coupled with MDS ensures only approved authenticators can register, useful for enterprise compliance scenarios.
8. Transport Selection – Though not shown, events can constrain acceptable transports (e.g., USB,NFC,BLE) to tailor which types of authenticators are permitted.