diff --git a/routers/repo/attachment.go b/routers/repo/attachment.go
index 668169110..a60bed2a6 100755
--- a/routers/repo/attachment.go
+++ b/routers/repo/attachment.go
@@ -241,14 +241,20 @@ func GetAttachment(ctx *context.Context) {
 	}
 
 	if dataSet != nil {
-		isPermit, err := models.GetUserDataSetPermission(dataSet, ctx.User)
-		if err != nil {
-			ctx.Error(http.StatusInternalServerError, "GetUserDataSetPermission", err.Error())
-			return
-		}
-		if !isPermit {
-			ctx.Error(http.StatusNotFound)
+		if !ctx.IsSigned {
+			ctx.SetCookie("redirect_to", setting.AppSubURL+ctx.Req.URL.RequestURI(), 0, setting.AppSubURL)
+			ctx.Redirect(setting.AppSubURL + "/user/login")
 			return
+		} else {
+			isPermit, err := models.GetUserDataSetPermission(dataSet, ctx.User)
+			if err != nil {
+				ctx.Error(http.StatusInternalServerError, "GetUserDataSetPermission", err.Error())
+				return
+			}
+			if !isPermit {
+				ctx.Error(http.StatusNotFound)
+				return
+			}
 		}
 	}