Ensuring Replay-Resistant Authentication with FusionAuth

wesley

I’m documenting our FusionAuth system login functionality and would like to know whether FusionAuth’s authentication is replay-resistant.

To clarify, a replay attack occurs when information transmitted between two parties is captured, stored, or altered, and then “replayed” later to disrupt communication or gain unauthorized access. Replay-resistant authentication ensures that captured data cannot be reused to impersonate a user or process.

Can you confirm if FusionAuth’s authentication mechanisms are replay-resistant? Please provide relevant documentation as well.

wesley

FusionAuth provides replay-resistant authentication mechanisms by adhering to industry standards for the technologies it implements. The level of replay resistance depends on the authentication workflow and specific standards followed.

Key Standards:

OAuth 2.0:
- FusionAuth adheres to RFC 6749, RFC 8628, and OpenID Connect Core, which include mechanisms to mitigate replay attacks (e.g., nonce and state parameters).
- Documentation: OAuth 2.0 Authorization Code Grant Example
Other Standards:
FusionAuth follows established standards for other authentication protocols, such as:
- WebAuthn: Provides strong, cryptographic-based authentication resistant to replay attacks.
- SAMLv2: Uses unique assertions and timestamps to prevent replay.
- OIDC (OpenID Connect): Includes nonce and other mechanisms to mitigate replay.

Replay Resistance Considerations:

Replay resistance is primarily ensured when these protocols are implemented as defined by their standards. FusionAuth provides the tools and configurations necessary to follow these standards.
However, deviations from these standards or implementation flaws outside of FusionAuth’s control (e.g., improper handling of state or nonce values) could introduce vulnerabilities.