Aether/backend/internal/auth/middleware.go

package auth

import (
	"context"
	"net/http"

	"aether/pkg/response"
)

type contextKey int

const keyUser contextKey = iota

// RequireAuth loads the session user and injects it into context.
// Returns 401 if not authenticated.
func RequireAuth(ss *SessionStore, store *Store) func(http.Handler) http.Handler {
	return func(next http.Handler) http.Handler {
		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
			id, ok := ss.GetUserID(r)
			if !ok {
				response.Error(w, http.StatusUnauthorized, "authentication required")
				return
			}
			user, err := store.GetByID(r.Context(), id)
			if err != nil {
				response.Error(w, http.StatusUnauthorized, "authentication required")
				return
			}
			ctx := context.WithValue(r.Context(), keyUser, user)
			next.ServeHTTP(w, r.WithContext(ctx))
		})
	}
}

// RequireAdmin additionally checks that the user is an admin.
func RequireAdmin(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		user := UserFromContext(r.Context())
		if user == nil || !user.IsAdmin {
			response.Error(w, http.StatusForbidden, "admin access required")
			return
		}
		next.ServeHTTP(w, r)
	})
}

// CSRF validates the double-submit CSRF token for state-changing requests.
func CSRF(next http.Handler) http.Handler {
	return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
		switch r.Method {
		case http.MethodGet, http.MethodHead, http.MethodOptions:
			next.ServeHTTP(w, r)
			return
		}
		if !ValidateCSRF(r) {
			response.Error(w, http.StatusForbidden, "invalid CSRF token")
			return
		}
		next.ServeHTTP(w, r)
	})
}

// UserFromContext retrieves the authenticated user from context (may be nil).
func UserFromContext(ctx context.Context) *User {
	u, _ := ctx.Value(keyUser).(*User)
	return u
}