M1/#293: RequireAdmin middleware + UserFromContext

internal/auth/middleware.go

@@ -0,0 +1,54 @@
+package auth
+
+import (
+	"context"
+	"errors"
+	"net/http"
+
+	"github.com/jackc/pgx/v5"
+	"github.com/jackc/pgx/v5/pgxpool"
+
+	"git.fabledsword.com/bvandeusen/minstrel/internal/db/dbq"
+)
+
+type ctxKey int
+
+const userCtxKey ctxKey = 1
+
+// RequireAdmin gates a handler on X-API-Token matching an admin user. This is
+// the Minstrel-native token path (`/api/*`); Subsonic-compatible auth under
+// `/rest/*` lands with the Subsonic server.
+func RequireAdmin(pool *pgxpool.Pool) func(http.Handler) http.Handler {
+	return func(next http.Handler) http.Handler {
+		return http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
+			token := r.Header.Get("X-API-Token")
+			if token == "" {
+				http.Error(w, "missing X-API-Token", http.StatusUnauthorized)
+				return
+			}
+			q := dbq.New(pool)
+			user, err := q.GetUserByAPIToken(r.Context(), token)
+			if err != nil {
+				if errors.Is(err, pgx.ErrNoRows) {
+					http.Error(w, "invalid token", http.StatusUnauthorized)
+					return
+				}
+				http.Error(w, "auth lookup failed", http.StatusInternalServerError)
+				return
+			}
+			if !user.IsAdmin {
+				http.Error(w, "admin required", http.StatusForbidden)
+				return
+			}
+			ctx := context.WithValue(r.Context(), userCtxKey, user)
+			next.ServeHTTP(w, r.WithContext(ctx))
+		})
+	}
+}
+
+// UserFromContext returns the authenticated user when the request passed
+// through RequireAdmin (or a future RequireUser middleware).
+func UserFromContext(ctx context.Context) (dbq.User, bool) {
+	u, ok := ctx.Value(userCtxKey).(dbq.User)
+	return u, ok
+}