Allow to create config file next to binary (#701)

Force to use the proper temp dir

If we do not define the configDir then the Go
create a random temp dir for copy routine.
It is not optimal from security purpose.

util/file.go

@@ -11,8 +11,7 @@ import (
 // The output JSON is pretty-formatted
 func WriteJson(file string, obj interface{}) error {
 
-	configDir, configFileName := filepath.Split(file)
-	err := os.MkdirAll(configDir, 0750)
+	configDir, configFileName, err := prepareConfigFileDir(file)
 	if err != nil {
 		return err
 	}
@@ -100,3 +99,13 @@ func CopyFileContents(src, dst string) (err error) {
 	err = out.Sync()
 	return
 }
+
+func prepareConfigFileDir(file string) (string, string, error) {
+	configDir, configFileName := filepath.Split(file)
+	if configDir == "" {
+		return filepath.Dir(file), configFileName, nil
+	}
+
+	err := os.MkdirAll(configDir, 0750)
+	return configDir, configFileName, err
+}

util/file_test.go

@@ -3,11 +3,13 @@ package util_test
 import (
 	"crypto/md5"
 	"encoding/hex"
-	"github.com/netbirdio/netbird/util"
-	. "github.com/onsi/ginkgo"
-	. "github.com/onsi/gomega"
 	"io"
 	"os"
+
+	. "github.com/onsi/ginkgo"
+	. "github.com/onsi/gomega"
+
+	"github.com/netbirdio/netbird/util"
 )
 
 var _ = Describe("Client", func() {
@@ -102,4 +104,23 @@ var _ = Describe("Client", func() {
 			})
 		})
 	})
+
+	Describe("Handle config file without full path", func() {
+		Context("config file handling", func() {
+			It("should be successful", func() {
+				written := &TestConfig{
+					SomeField: 123,
+				}
+				cfgFile := "test_cfg.json"
+				defer os.Remove(cfgFile)
+
+				err := util.WriteJson(cfgFile, written)
+				Expect(err).NotTo(HaveOccurred())
+
+				read, err := util.ReadJson(cfgFile, &TestConfig{})
+				Expect(err).NotTo(HaveOccurred())
+				Expect(read).NotTo(BeNil())
+			})
+		})
+	})
 })