# Auth-proxy Security Model

## Authentication flow

1. Client request arrives at NGINX.
2. NGINX sends an internal auth_request subrequest to auth-proxy.
3. Auth-proxy checks:
   - Is the IP in the permanent whitelist? → Allow.
   - Is the IP in the temporary whitelist and not expired? → Allow.
   - Otherwise → 401 Unauthorized.
4. NGINX passes the request to the upstream service if auth-proxy returned 200.
5. NGINX returns 401 to the client if auth-proxy returned 401/403.

## IP handling

### Permanent whitelist

- Stored in SQLite `permanent_whitelist` table.
- Only single IPs and CIDR ranges (as strings) are supported.
- Added/removed via the `/api/whitelist/perm` API.

### Temporary whitelist

- Stored in SQLite `temp_whitelist` table.
- Entries expire after their TTL.
- The cleanup goroutine runs every 60 seconds (configurable) to remove expired entries.

## API key

The API key is the only secret for the /api/* endpoints. It's sent as a bearer token
in the Authorization header.

- **Required.** The service will not start without it.
- Keep it secret. Don't log it. Don't put it in the URL.
- Use a strong random string.
- Rotate it regularly.

## Audit log

All whitelist operations are logged to the `audit_log` table in SQLite.
Each entry records:

- `action` — what happened (`add_temp`, `delete_temp`, `add_perm`, `delete_perm`, `expire_temp`)
- `ip` — the affected IP or CIDR range
- `ttl_seconds` — for temp entries
- `reason` — the reason provided
- `api_client_ip` — the IP that made the API call (from NGINX `X-Real-IP`)

Retrieve logs via the `/api/logs` endpoint.

The audit log is automatically rotated to maintain a maximum of 200,000 entries.

## IP validation

The `/api/whitelist/temp` and `/api/whitelist/perm` endpoints validate inputs:

- `/api/whitelist/temp` requires a valid IP address.
- `/api/whitelist/perm` requires a valid IP address or CIDR range.
- Invalid inputs return `400 Bad Request`.

## Graceful shutdown

The service listens for SIGTERM and SIGINT. On signal:

1. Stop accepting new connections.
2. Close idle connections.
3. Wait for in-flight requests to complete (up to 30 seconds).
4. Exit.

This ensures Docker deployments can shut down cleanly.

## What we don't do

- We don't support JWT/OAuth. If you need these, add them later.
- We don't support session state. The auth decision is made per-request.
- We don't support rate limiting. Use NGINX's limit_req for that.
- We don't support IP-based rate limiting. Use NGINX's limit_conn for that.
- We support IPv6. The `/api/whitelist` endpoints accept both IPv4 and IPv6 addresses.
- We don't support TLS. The auth endpoint should always be served over TLS.
- We don't support logging to a file. Logs go to stdout (Docker).
- We don't support metrics. If you need metrics, add them later.
- We don't support health checks with Prometheus. The /status endpoint returns a JSON response with uptime, DB status, and whitelist counts.
- We don't support configuration via a config file. Use environment variables.
- We don't support multiple domains. The auth-proxy service doesn't care about domains.
- We don't support HTTP/2. The auth-proxy service uses HTTP/1.1 only.
- We don't support WebSocket. The auth-proxy service doesn't need WebSocket.
- We don't support gRPC. The auth-proxy service is a simple REST API.