Broken Access Control in Chi with Basic Auth

Broken Access Control (BAC) in the Chi web framework often intersects poorly with HTTP Basic Auth when authorization checks are applied only after authentication succeeds. Chi is a minimalistic router and middleware stack for Go, and it does not enforce any authorization model by default. If routes are registered without explicit middleware that validates permissions, any authenticated user may access endpoints intended for a subset of roles or scopes.

When Basic Auth is used, credentials are sent with every request as a base64-encoded username:password pair (not encrypted unless protected by TLS). If Chi handlers assume authentication implies proper authorization—for example, checking only for the presence of a user in context without validating role or tenant boundaries—an attacker who possesses a valid credential can perform BOLA/IDOR by iterating predictable resource identifiers. For example, an endpoint like GET /orgs/{orgID}/projects/{projectID} might verify that a user is logged in but fail to ensure that the authenticated user belongs to the requested orgID. This mismatch between authentication and authorization is a classic Broken Access Control misconfiguration.

Additionally, Basic Auth over unencrypted channels exposes credentials to network sniffing, effectively bypassing any access control logic because an attacker can replay captured headers. Even when TLS is used, missing middleware in Chi can lead to insecure default behaviors, such as not rejecting requests with empty or malformed Authorization headers. Without explicit middleware that enforces scope-based access control and validates each request against a policy store, Chi routes will default to permissive access, amplifying the impact of misconfigured route guards.

Consider a scenario where an OpenAPI spec defines a /api/v1/users/{userId} endpoint with security scheme basicAuth. If the Chi implementation only checks that a user is authenticated (via a middleware that sets ctx.Set("user", user)) but does not verify that the authenticated user’s ID matches userId or that the user has the required role, the endpoint is vulnerable to IDOR. Runtime scans from middleBrick can detect such authorization gaps by correlating spec-defined security requirements with actual handler behavior, flagging missing authorization checks as high-severity findings.

To remediate Broken Access Control when using Basic Auth in Chi, implement explicit authorization middleware that runs after authentication and validates permissions against the requested resource. Always enforce TLS and avoid logging credentials. Below are concrete code examples that demonstrate secure patterns.

Secure Basic Auth middleware with role-based checks

func BasicAuthWithRole(requiredRole string) func(chi.Handler) {
    return func(next chi.Handler) chi.Handler {
        return chi.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            user, pass, ok := r.BasicAuth()
            if !ok {
                http.Error(w, "Unauthorized", http.StatusUnauthorized)
                return
            }
            // Validate credentials against a secure store (e.g., database)
            u, err := userStore.FindByCredentials(user, pass)
            if err != nil || !u.Active {
                http.Error(w, "Unauthorized", http.StatusUnauthorized)
                return
            }
            // Enforce role-based access control
            if !u.HasRole(requiredRole) {
                http.Error(w, "Forbidden", http.StatusForbidden)
                return
            }
            ctx := context.WithValue(r.Context(), "user", u)
            next.ServeHTTP(w, r.WithContext(ctx))
        })
    }
}

Per-request resource ownership validation

func ProjectAccessMiddleware(projectIDParam string) func(chi.Handler) {
    return func(next chi.Handler) chi.Handler {
        return chi.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
            user := r.Context().Value("user").(*User)
            vars := chi.URLParamNames(r)
            projectID := chi.URLParam(r, projectIDParam)
            // Ensure the user has access to the specific project
            if !user.CanAccessProject(projectID) {
                http.Error(w, "Forbidden", http.StatusForbidden)
                return
            }
            next.ServeHTTP(w, r)
        })
    }
}

Chi route definition with layered guards

r := chi.NewRouter()
r.Use(middleware.RequestID)
r.Use(middleware.RealIP)
r.Use(middleware.Logger)
r.Use(BasicAuthWithRole("member"))
r.Get("/orgs/{orgID}/projects/{projectID}", ProjectAccessMiddleware("projectID"), func(w http.ResponseWriter, r *http.Request) {
    // Handler logic: user is authenticated, has role "member", and owns the project
    projectID := chi.URLParam(r, "projectID")
    orgID := chi.URLParam(r, "orgID")
    // Safe to proceed
})

These patterns ensure that authentication via Basic Auth is decoupled from authorization logic, reducing the risk of BOLA/IDOR. middleBrick can validate that such controls exist in your handler implementations and that the OpenAPI spec’s security requirements are reflected in Chi middleware chains, providing actionable remediation guidance when gaps are found.