Laravel Passport: TokenGuard Authenticates Unrelated User for Client Credentials Tokens

Impact

Authentication Bypass for client_credentials tokens. the league/oauth2-server library sets the JWT sub claim to the client identifier (since there's no user). The token guard then passes this value to retrieveById() without validating it's actually a user identifier, potentially resolving an unrelated real user. Any machine-to-machine token can inadvertently authenticate as an actual user.

Usage of EnsureClientIsResourceOwner middleware together with Passport::$clientUuids set to false, can result in resolving the user instead, as stated in the documentation.

> The underlying OAuth2 server sets the token's sub claim to the client's identifier for client credentials tokens. By default, Passport uses UUIDs for clients, so this cannot collide with a user's integer primary key. However, if you have set Passport::$clientUuids to false, a client credentials token may inadvertently resolve a user whose ID matches the client's ID. In such cases, using this middleware cannot guarantee that the incoming token is a client credentials token.

Patches

Patched in v13.7.1

Workarounds

_Is there a way for users to fix or remediate the vulnerability without upgrading?_ Disallow usage of client_credentials.

References

• https://github.com/laravel/passport/issues/1900
• https://github.com/laravel/passport/pull/1901
• https://github.com/laravel/passport/pull/1902
• https://github.com/thephpleague/oauth2-server/issues/1456#issuecomment-2734989996