Decoupled Security: Securing the Auth Flow Without Touching the Implementation
Integrating additional security measures into existing authentication systems often introduces operational risks. With our new Caddy plugin, we shift this layer into the infrastructure. A load test with 40,000 requests demonstrates the stability of this architecture. For technical decision-makers, the authentication process is a mission-critical component. Any modification to the core codebase…
Integrating extra security into existing authentication systems can bring operational risks. Caddy's new plugin shifts this layer to infrastructure, a load test with 40,000 requests confirms the architecture's stability. For technical decision-makers, the authentication process is critical; any change to the core codebase raises system failure risks.
New verification methods, like checking for leaked passwords, often require backend changes and new dependencies. However, a non-negotiable requirement remains: third-party service latency or failure must not disrupt the standard login process for users.
Instead of requiring teams to modify their backend implementations (Node, PHP, Go, Java), Caddy adopts an infrastructure-based approach. The official caddy-hansestack plugin for the Caddy reverse proxy completely decouples the security QA layer from the application. In enrich_response mode, the plugin acts as middleware, intercepting requests, securely extracting passwords using k-anonymity, and immediately passing the original login request to the backend in parallel.
The backend remains unchanged and processes the login normally. Caddy waits for the asynchronous API result before responding and adds the HTTP header (X-Hansestack-Leaked: true) to the client's response. This requires no backend code changes and adds no latency to the primary login process.
To validate the system's reliability, a load test with 40,000 concurrent login attempts was conducted. The system was tested in a controlled environment, simulating 40 blocks of 1,000 background processes targeting the local Caddy server using a bash script. The goal was to overload the system to measure the behavior of the integrated circuit breaker. The load test showed that 36,700 requests were intercepted by the fail-open mechanism, with zero client errors occurring.
The system's resilience is demonstrated by its ability to handle over 36,700 requests, rate-limiting 1,924 requests due to concurrency, and activating the circuit breaker after five consecutive errors. After the circuit breaker opens, the remaining 36,715 requests are passed through locally without an API call, relieving the external interface and preventing the auth flow from being blocked.
The system recorded 0 client errors, maintaining delivery of requests to the backend, and maintained the login process with measured latencies of p50 (median) at 2.73 ms, p95 at 150 ms, and p99 at 345 ms, all below the 500ms timeout.
Written by urgent.news from Dev.to's reporting — not their text. Machine-written — may contain errors; check the original before relying on it.
