fix return code when request /logs with long file name

pkg/routes/logs.go

@@ -18,7 +18,9 @@ package routes
 
 import (
 	"net/http"
+	"os"
 	"path"
+	"syscall"
 
 	"github.com/emicklei/go-restful"
 )
@@ -42,6 +44,12 @@ func (l Logs) Install(c *restful.Container) {
 func logFileHandler(req *restful.Request, resp *restful.Response) {
 	logdir := "/var/log"
 	actual := path.Join(logdir, req.PathParameter("logpath"))
+
+	// check filename length first, return 404 if it's oversize.
+	if logFileNameIsTooLong(actual) {
+		http.Error(resp, "file not found", http.StatusNotFound)
+		return
+	}
 	http.ServeFile(resp.ResponseWriter, req.Request, actual)
 }
 
@@ -49,3 +57,15 @@ func logFileListHandler(req *restful.Request, resp *restful.Response) {
 	logdir := "/var/log"
 	http.ServeFile(resp.ResponseWriter, req.Request, logdir)
 }
+
+// logFileNameIsTooLong checks filename length, returns true if it's longer than 255.
+// cause http.ServeFile returns default error code 500 except for NotExist and Forbidden, but we need to separate the real 500 from oversize filename here.
+func logFileNameIsTooLong(filePath string) bool {
+	_, err := os.Stat(filePath)
+	if err != nil {
+		if e, ok := err.(*os.PathError); ok && e.Err == syscall.ENAMETOOLONG {
+			return true
+		}
+	}
+	return false
+}

pkg/routes/logs_test.go

@@ -0,0 +1,48 @@
+/*
+Copyright 2021 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package routes
+
+import (
+	"fmt"
+	"os"
+	"testing"
+)
+
+func TestPreCheckLogFileNameLength(t *testing.T) {
+	oversizeFileName := fmt.Sprintf("%0256s", "a")
+	normalFileName := fmt.Sprintf("%0255s", "a")
+
+	// check file with oversize name.
+	if !logFileNameIsTooLong(oversizeFileName) {
+		t.Error("failed to check oversize filename")
+	}
+
+	// check file with normal name which doesn't exist.
+	if logFileNameIsTooLong(normalFileName) {
+		t.Error("failed to check normal filename")
+	}
+
+	// check file with normal name which does exist.
+	_, err := os.Create(normalFileName)
+	if err != nil {
+		t.Error("failed to create test file")
+	}
+	defer os.Remove(normalFileName)
+	if logFileNameIsTooLong(normalFileName) {
+		t.Error("failed to check normal filename")
+	}
+}