Arc has unauthenticated application log disclosure via `/api/v1/logs`

Arc exposes `GET /api/v1/logs` without authentication even when authentication is enabled by default. The route is registered before the global Fiber authentication middleware, and the handler returns recent buffered application logs without performing its own authorization check. Details Arc applies the global auth middleware after calling `server.RegisterRoutes()`: • `cmd/arc/main.go:1598-1599` registers base routes via `server.RegisterRoutes()`. • `cmd/arc/main.go:1601-1618` configures and installs `auth.NewMiddleware(...)` later. `server.RegisterRoutes()` registers `GET /api/v1/logs` as a base route: • `internal/api/server.go:164-183` registers base health, metrics, and logs routes, including `s.app.Get("/api/v1/logs", s.logsHandler)`. The logs handler returns buffered logs without checking authentication or authorization: • `internal/api/server.go:537-567` parses `limit`, `level`, and `since_minutes`, reads `logger.GetBuffer().GetRecent(...)`, and returns JSON. • `internal/logger/buffer.go:9-16` defines log entries returned to callers: timestamp, level, component, message, and caller. • `internal/logger/buffer.go:33-39` creates a global log buffer holding the last 10,000 entries. • `internal/api/server.go:540-558` permits up to `limit=1000` and `since_minutes=1440` in one unauthenticated request. Authentication is enabled by default and `/api/v1/logs` is not listed as a public route: • `internal/config/config.go:841-843` defaults auth to enabled. • `internal/auth/middleware.go:29-41` public defaults are `/health`, `/ready`, `/api/v1/auth/verify`, and `/metrics` prefix; `/api/v1/logs` is not public. However, Fiber route/middleware order makes the later middleware ineffective for an earlier exact route. Local verification against Fiber v2.52.13 showed a route registered before `app.Use(...)` returns `200` and the later middleware is not reached. Fiber’s router walks routes in declaration order and stops after the first matching route unless the handler calls `c.Next()`; `logsHandler` does not call `c.Next()`. Proof of concept Safe local reproduction only; do not scan external infrastructure. 1. Start Arc with default authentication enabled. 2. Request logs without an `Authorization` header or `x-api-key` header: ```bash curl -i 'http://127.0.0.1:8000/api/v1/logs?limit=1000&since_minutes=1440' ``` Expected vulnerable result: ```http HTTP/1.1 200 OK Content-Type: application/json {"timestamp":"...","count":...,"logs":[...]} ``` 3. Compare with a protected endpoint without credentials: ```bash curl -i 'http://127.0.0.1:8000/api/v1/auth/tokens' ``` Expected protected result: ```http HTTP/1.1 401 Unauthorized ``` This demonstrates that default auth is active while `/api/v1/logs` bypasses it due to registration order. Impact An unauthenticated network attacker can retrieve recent application logs. Depending on deployment and log level, logs can disclose operational metadata such as component names, internal paths, database/measurement names, node identifiers, caller locations, request outcomes, and error details. This can assist further attacks and may expose sensitive data if any deployment logs secrets or user-controlled confidential data. The audit did not confirm that the bootstrap admin token banner is captured by this endpoint; that banner is printed with `fmt.Fprintf(os.Stderr, ...)`, while this endpoint reads the zerolog-backed application buffer. Workarounds Until patched, operators can restrict access to `/api/v1/logs` at a reverse proxy, firewall, ingress policy, or service mesh. If the endpoint is not needed, block it entirely. Suggested fix • Move `/api/v1/logs` registration after global auth middleware and require an authenticated administrator; or • Add explicit route-level middleware: `auth.RequireAdmin(authManager)` for `/api/v1/logs`; and • Add a regression test that unauthenticated requests to `/api/v1/logs` return 401/403 while `/health` and `/ready` remain public. References / evidence • `cmd/arc/main.go:1598-1618` • `internal/api/server.go:164-183` • `internal/api/server.go:537-567` • `internal/auth/middleware.go:29-41` • `internal/config/config.go:841-843` • `internal/logger/buffer.go:9-16` • `internal/logger/buffer.go:33-39`