What role does a firewall or proxy play in an "authentication failed error code 403" scenario?

Firewalls and proxies can significantly contribute to a 403 error: **Firewalls (Network/Web Application):** Network firewalls can block specific IPs or ports, preventing connection. Web Application Firewalls (WAFs) are designed to protect applications and can generate a 403 if they detect suspicious activity (e.g., injection attempts, unusual headers) or if a request violates security policies, even if credentials are correct, blocking it before it reaches the application's authentication layer. **Proxies (Forward/Reverse):** Forward proxies (client-side) might modify headers or present a different IP, potentially triggering server-side IP restrictions. Reverse proxies (server-side, like Nginx) often have their own access control rules. If these are misconfigured or conflict with the backend application, they might return a 403 before the request even reaches the actual application server's authentication logic.