Fix logfile open filemode (#5354)

Fixes #5346

logger/logfile.go

@@ -54,7 +54,7 @@ func (l *LogFile) openNew() error {
 	newfileName := fileName + "-" + strconv.FormatInt(createTime.UnixNano(), 10) + fileExt
 	newfilePath := filepath.Join(l.logPath, newfileName)
 	// Try creating a file. We truncate the file because we are the only authority to write the logs
-	filePointer, err := os.OpenFile(newfilePath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 640)
+	filePointer, err := os.OpenFile(newfilePath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0640)
 	if err != nil {
 		return err
 	}

logger/logfile_test.go

@@ -29,6 +29,21 @@ func TestLogFile_timeRotation(t *testing.T) {
 	}
 }
 
+func TestLogFile_openNew(t *testing.T) {
+	t.Parallel()
+	tempDir := testutil.TempDir(t, "LogWriterOpen")
+	defer os.Remove(tempDir)
+	logFile := LogFile{fileName: testFileName, logPath: tempDir, duration: testDuration}
+
+	if err := logFile.openNew(); err != nil {
+		t.Errorf("Expected open file %s, got an error (%s)", testFileName, err)
+	}
+
+	if _, err := ioutil.ReadFile(logFile.FileInfo.Name()); err != nil {
+		t.Errorf("Expected readable file %s, got an error (%s)", logFile.FileInfo.Name(), err)
+	}
+}
+
 func TestLogFile_byteRotation(t *testing.T) {
 	t.Parallel()
 	tempDir := testutil.TempDir(t, "LogWriterBytes")