Code maintenance: OS package for file system

- OS custom internal package for file system interaction
- Remove fileManager external dependency
- Closer API to Go's native API on the OS
- Create directories at startup
- Better testability
- Move Unsetenv to os interface

.golangci.yml

@@ -10,6 +10,10 @@ issues:
       linters:
         - dupl
         - maligned
+    - path: internal/os/alias\.go
+      linters:
+        - gochecknoglobals
+      text: IsNotExist is a global variable
 
 linters:
   disable-all: true

cmd/gluetun/main.go

@@ -5,7 +5,7 @@ import (
 	"fmt"
 	"net"
 	"net/http"
-	"os"
+	nativeos "os"
 	"os/signal"
 	"strings"
 	"sync"
@@ -22,6 +22,7 @@ import (
 	gluetunLogging "github.com/qdm12/gluetun/internal/logging"
 	"github.com/qdm12/gluetun/internal/models"
 	"github.com/qdm12/gluetun/internal/openvpn"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/params"
 	"github.com/qdm12/gluetun/internal/publicip"
 	"github.com/qdm12/gluetun/internal/routing"
@@ -32,7 +33,6 @@ import (
 	"github.com/qdm12/gluetun/internal/updater"
 	versionpkg "github.com/qdm12/gluetun/internal/version"
 	"github.com/qdm12/golibs/command"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 	"github.com/qdm12/golibs/network"
 )
@@ -50,21 +50,24 @@ func main() {
 	buildInfo.Commit = commit
 	buildInfo.BuildDate = buildDate
 	ctx := context.Background()
-	os.Exit(_main(ctx, os.Args))
+	args := nativeos.Args
+	os := os.New()
+	nativeos.Exit(_main(ctx, args, os))
 }
 
-func _main(background context.Context, args []string) int { //nolint:gocognit,gocyclo
+//nolint:gocognit,gocyclo
+func _main(background context.Context, args []string, os os.OS) int {
 	if len(args) > 1 { // cli operation
 		var err error
 		switch args[1] {
 		case "healthcheck":
 			err = cli.HealthCheck(background)
 		case "clientkey":
-			err = cli.ClientKey(args[2:])
+			err = cli.ClientKey(args[2:], os.OpenFile)
 		case "openvpnconfig":
-			err = cli.OpenvpnConfig()
+			err = cli.OpenvpnConfig(os)
 		case "update":
-			err = cli.Update(args[2:])
+			err = cli.Update(args[2:], os)
 		default:
 			err = fmt.Errorf("command %q is unknown", args[1])
 		}
@@ -82,15 +85,14 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 	httpClient := &http.Client{Timeout: clientTimeout}
 	client := network.NewClient(clientTimeout)
 	// Create configurators
-	fileManager := files.NewFileManager()
-	alpineConf := alpine.NewConfigurator(fileManager)
-	ovpnConf := openvpn.NewConfigurator(logger, fileManager)
-	dnsConf := dns.NewConfigurator(logger, client, fileManager)
+	alpineConf := alpine.NewConfigurator(os.OpenFile)
+	ovpnConf := openvpn.NewConfigurator(logger, os)
+	dnsConf := dns.NewConfigurator(logger, client, os.OpenFile)
 	routingConf := routing.NewRouting(logger)
-	firewallConf := firewall.NewConfigurator(logger, routingConf, fileManager)
+	firewallConf := firewall.NewConfigurator(logger, routingConf, os.OpenFile)
 	streamMerger := command.NewStreamMerger()
 
-	paramsReader := params.NewReader(logger, fileManager)
+	paramsReader := params.NewReader(logger, os)
 	fmt.Println(gluetunLogging.Splash(buildInfo))
 
 	printVersions(ctx, logger, map[string]func(ctx context.Context) (string, error){
@@ -106,8 +108,17 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 	}
 	logger.Info(allSettings.String())
 
+	if err := os.MkdirAll("/tmp/gluetun", 0644); err != nil {
+		logger.Error(err)
+		return 1
+	}
+	if err := os.MkdirAll("/gluetun", 0644); err != nil {
+		logger.Error(err)
+		return 1
+	}
+
 	// TODO run this in a loop or in openvpn to reload from file without restarting
-	storage := storage.New(logger)
+	storage := storage.New(logger, os)
 	const updateServerFile = true
 	allServers, err := storage.SyncServers(constants.GetAllServers(), updateServerFile)
 	if err != nil {
@@ -124,8 +135,8 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 		logger.Error(err)
 		return 1
 	}
-	err = fileManager.SetOwnership("/etc/unbound", uid, gid)
-	if err != nil {
+
+	if err := os.Chown("/etc/unbound", uid, gid); err != nil {
 		logger.Error(err)
 		return 1
 	}
@@ -219,7 +230,7 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 	go collectStreamLines(ctx, streamMerger, logger, signalTunnelReady)
 
 	openvpnLooper := openvpn.NewLooper(allSettings.OpenVPN, nonRootUsername, uid, gid, allServers,
-		ovpnConf, firewallConf, routingConf, logger, httpClient, fileManager, streamMerger, cancel)
+		ovpnConf, firewallConf, routingConf, logger, httpClient, os.OpenFile, streamMerger, cancel)
 	wg.Add(1)
 	// wait for restartOpenvpn
 	go openvpnLooper.Run(ctx, wg)
@@ -236,7 +247,7 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 	go unboundLooper.Run(ctx, wg, signalDNSReady)
 
 	publicIPLooper := publicip.NewLooper(
-		client, logger, fileManager, allSettings.PublicIP, uid, gid)
+		client, logger, allSettings.PublicIP, uid, gid, os)
 	wg.Add(1)
 	go publicIPLooper.Run(ctx, wg)
 	wg.Add(1)
@@ -279,11 +290,11 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 	// until openvpn is launched
 	_, _ = openvpnLooper.SetStatus(constants.Running) // TODO option to disable with variable
 
-	signalsCh := make(chan os.Signal, 1)
+	signalsCh := make(chan nativeos.Signal, 1)
 	signal.Notify(signalsCh,
 		syscall.SIGINT,
 		syscall.SIGTERM,
-		os.Interrupt,
+		nativeos.Interrupt,
 	)
 	shutdownErrorsCount := 0
 	select {
@@ -295,7 +306,7 @@ func _main(background context.Context, args []string) int { //nolint:gocognit,go
 	}
 	if allSettings.OpenVPN.Provider.PortForwarding.Enabled {
 		logger.Info("Clearing forwarded port status file %s", allSettings.OpenVPN.Provider.PortForwarding.Filepath)
-		if err := fileManager.Remove(string(allSettings.OpenVPN.Provider.PortForwarding.Filepath)); err != nil {
+		if err := os.Remove(string(allSettings.OpenVPN.Provider.PortForwarding.Filepath)); err != nil {
 			logger.Error(err)
 			shutdownErrorsCount++
 		}

internal/alpine/alpine.go

@@ -3,7 +3,7 @@ package alpine
 import (
 	"os/user"
 
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 )
 
 type Configurator interface {
@@ -11,15 +11,15 @@ type Configurator interface {
 }
 
 type configurator struct {
-	fileManager files.FileManager
-	lookupUID   func(uid string) (*user.User, error)
-	lookupUser  func(username string) (*user.User, error)
+	openFile   os.OpenFileFunc
+	lookupUID  func(uid string) (*user.User, error)
+	lookupUser func(username string) (*user.User, error)
 }
 
-func NewConfigurator(fileManager files.FileManager) Configurator {
+func NewConfigurator(openFile os.OpenFileFunc) Configurator {
 	return &configurator{
-		fileManager: fileManager,
-		lookupUID:   user.LookupId,
-		lookupUser:  user.Lookup,
+		openFile:   openFile,
+		lookupUID:  user.LookupId,
+		lookupUser: user.Lookup,
 	}
 }

internal/alpine/users.go

@@ -2,6 +2,7 @@ package alpine
 
 import (
 	"fmt"
+	"os"
 	"os/user"
 )
 
@@ -26,14 +27,15 @@ func (c *configurator) CreateUser(username string, uid int) (createdUsername str
 		return "", fmt.Errorf("cannot create user: user with name %s already exists for ID %s instead of %d",
 			username, u.Uid, uid)
 	}
-	passwd, err := c.fileManager.ReadFile("/etc/passwd")
+	file, err := c.openFile("/etc/passwd", os.O_APPEND|os.O_WRONLY, 0644)
 	if err != nil {
 		return "", fmt.Errorf("cannot create user: %w", err)
 	}
-	passwd = append(passwd, []byte(fmt.Sprintf("%s:x:%d:::/dev/null:/sbin/nologin\n", username, uid))...)
-
-	if err := c.fileManager.WriteToFile("/etc/passwd", passwd); err != nil {
-		return "", fmt.Errorf("cannot create user: %w", err)
+	s := fmt.Sprintf("%s:x:%d:::/dev/null:/sbin/nologin\n", username, uid)
+	_, err = file.WriteString(s)
+	if err != nil {
+		_ = file.Close()
+		return "", err
 	}
-	return username, nil
+	return username, file.Close()
 }

internal/cli/cli.go

@@ -4,29 +4,40 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io/ioutil"
 	"net/http"
 	"strings"
 	"time"
 
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/healthcheck"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/params"
 	"github.com/qdm12/gluetun/internal/provider"
 	"github.com/qdm12/gluetun/internal/settings"
 	"github.com/qdm12/gluetun/internal/storage"
 	"github.com/qdm12/gluetun/internal/updater"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 )
 
-func ClientKey(args []string) error {
+func ClientKey(args []string, openFile os.OpenFileFunc) error {
 	flagSet := flag.NewFlagSet("clientkey", flag.ExitOnError)
 	filepath := flagSet.String("path", string(constants.ClientKey), "file path to the client.key file")
 	if err := flagSet.Parse(args); err != nil {
 		return err
 	}
-	fileManager := files.NewFileManager()
-	data, err := fileManager.ReadFile(*filepath)
+	file, err := openFile(*filepath, os.O_RDONLY, 0)
+	if err != nil {
+		return err
+	}
+	data, err := ioutil.ReadAll(file)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	if err := file.Close(); err != nil {
+		return err
+	}
 	if err != nil {
 		return err
 	}
@@ -49,17 +60,17 @@ func HealthCheck(ctx context.Context) error {
 	return healthchecker.Check(ctx, url)
 }
 
-func OpenvpnConfig() error {
+func OpenvpnConfig(os os.OS) error {
 	logger, err := logging.NewLogger(logging.ConsoleEncoding, logging.InfoLevel)
 	if err != nil {
 		return err
 	}
-	paramsReader := params.NewReader(logger, files.NewFileManager())
+	paramsReader := params.NewReader(logger, os)
 	allSettings, err := settings.GetAllSettings(paramsReader)
 	if err != nil {
 		return err
 	}
-	allServers, err := storage.New(logger).SyncServers(constants.GetAllServers(), false)
+	allServers, err := storage.New(logger, os).SyncServers(constants.GetAllServers(), false)
 	if err != nil {
 		return err
 	}
@@ -81,7 +92,7 @@ func OpenvpnConfig() error {
 	return nil
 }
 
-func Update(args []string) error {
+func Update(args []string, os os.OS) error {
 	options := settings.Updater{CLI: true}
 	var flushToFile bool
 	flagSet := flag.NewFlagSet("update", flag.ExitOnError)
@@ -110,7 +121,7 @@ func Update(args []string) error {
 	ctx := context.Background()
 	const clientTimeout = 10 * time.Second
 	httpClient := &http.Client{Timeout: clientTimeout}
-	storage := storage.New(logger)
+	storage := storage.New(logger, os)
 	const writeSync = false
 	currentServers, err := storage.SyncServers(constants.GetAllServers(), writeSync)
 	if err != nil {

internal/constants/permissions.go

@@ -1,8 +0,0 @@
-package constants
-
-import "os"
-
-const (
-	UserReadPermission      os.FileMode = 0400
-	AllReadWritePermissions os.FileMode = 0666
-)

internal/dns/conf.go

@@ -8,8 +8,8 @@ import (
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/settings"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 	"github.com/qdm12/golibs/network"
 )
@@ -21,11 +21,29 @@ func (c *configurator) MakeUnboundConf(ctx context.Context, settings settings.DN
 	for _, warning := range warnings {
 		c.logger.Warn(warning)
 	}
-	return c.fileManager.WriteLinesToFile(
-		string(constants.UnboundConf),
-		lines,
-		files.Ownership(uid, gid),
-		files.Permissions(constants.UserReadPermission))
+
+	const filepath = string(constants.UnboundConf)
+	file, err := c.openFile(filepath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0400)
+	if err != nil {
+		return err
+	}
+
+	_, err = file.WriteString(strings.Join(lines, "\n"))
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	if err := file.Chown(uid, gid); err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	if err := file.Close(); err != nil {
+		return err
+	}
+
+	return nil
 }
 
 // MakeUnboundConf generates an Unbound configuration from the user provided settings.

internal/dns/dns.go

@@ -5,9 +5,9 @@ import (
 	"io"
 	"net"
 
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/settings"
 	"github.com/qdm12/golibs/command"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 	"github.com/qdm12/golibs/network"
 )
@@ -24,19 +24,20 @@ type Configurator interface {
 }
 
 type configurator struct {
-	logger      logging.Logger
-	client      network.Client
-	fileManager files.FileManager
-	commander   command.Commander
-	lookupIP    func(host string) ([]net.IP, error)
+	logger    logging.Logger
+	client    network.Client
+	openFile  os.OpenFileFunc
+	commander command.Commander
+	lookupIP  func(host string) ([]net.IP, error)
 }
 
-func NewConfigurator(logger logging.Logger, client network.Client, fileManager files.FileManager) Configurator {
+func NewConfigurator(logger logging.Logger, client network.Client,
+	openFile os.OpenFileFunc) Configurator {
 	return &configurator{
-		logger:      logger.WithPrefix("dns configurator: "),
-		client:      client,
-		fileManager: fileManager,
-		commander:   command.NewCommander(),
-		lookupIP:    net.LookupIP,
+		logger:    logger.WithPrefix("dns configurator: "),
+		client:    client,
+		openFile:  openFile,
+		commander: command.NewCommander(),
+		lookupIP:  net.LookupIP,
 	}
 }

internal/dns/nameserver.go

@@ -2,10 +2,12 @@ package dns
 
 import (
 	"context"
+	"io/ioutil"
 	"net"
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/os"
 )
 
 // UseDNSInternally is to change the Go program DNS only.
@@ -23,10 +25,16 @@ func (c *configurator) UseDNSInternally(ip net.IP) {
 // UseDNSSystemWide changes the nameserver to use for DNS system wide.
 func (c *configurator) UseDNSSystemWide(ip net.IP, keepNameserver bool) error {
 	c.logger.Info("using DNS address %s system wide", ip.String())
-	data, err := c.fileManager.ReadFile(string(constants.ResolvConf))
+	const filepath = string(constants.ResolvConf)
+	file, err := c.openFile(filepath, os.O_RDWR, 0644)
 	if err != nil {
 		return err
 	}
+	data, err := ioutil.ReadAll(file)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
 	s := strings.TrimSuffix(string(data), "\n")
 	lines := strings.Split(s, "\n")
 	if len(lines) == 1 && lines[0] == "" {
@@ -44,6 +52,11 @@ func (c *configurator) UseDNSSystemWide(ip net.IP, keepNameserver bool) error {
 	if !found {
 		lines = append(lines, "nameserver "+ip.String())
 	}
-	data = []byte(strings.Join(lines, "\n"))
-	return c.fileManager.WriteToFile(string(constants.ResolvConf), data)
+	s = strings.Join(lines, "\n")
+	_, err = file.WriteString(s)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	return file.Close()
 }

internal/dns/nameserver_test.go

@@ -2,12 +2,14 @@ package dns
 
 import (
 	"fmt"
+	"io"
 	"net"
 	"testing"
 
 	"github.com/golang/mock/gomock"
 	"github.com/qdm12/gluetun/internal/constants"
-	"github.com/qdm12/golibs/files/mock_files"
+	"github.com/qdm12/gluetun/internal/os"
+	"github.com/qdm12/gluetun/internal/os/mock_os"
 	"github.com/qdm12/golibs/logging/mock_logging"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -17,30 +19,36 @@ func Test_UseDNSSystemWide(t *testing.T) {
 	t.Parallel()
 	tests := map[string]struct {
 		data        []byte
-		writtenData []byte
+		writtenData string
+		openErr     error
 		readErr     error
 		writeErr    error
+		closeErr    error
 		err         error
 	}{
 		"no data": {
-			writtenData: []byte("nameserver 127.0.0.1"),
+			writtenData: "nameserver 127.0.0.1",
+		},
+		"open error": {
+			openErr: fmt.Errorf("error"),
+			err:     fmt.Errorf("error"),
 		},
 		"read error": {
 			readErr: fmt.Errorf("error"),
 			err:     fmt.Errorf("error"),
 		},
 		"write error": {
-			writtenData: []byte("nameserver 127.0.0.1"),
+			writtenData: "nameserver 127.0.0.1",
 			writeErr:    fmt.Errorf("error"),
 			err:         fmt.Errorf("error"),
 		},
 		"lines without nameserver": {
 			data:        []byte("abc\ndef\n"),
-			writtenData: []byte("abc\ndef\nnameserver 127.0.0.1"),
+			writtenData: "abc\ndef\nnameserver 127.0.0.1",
 		},
 		"lines with nameserver": {
 			data:        []byte("abc\nnameserver abc def\ndef\n"),
-			writtenData: []byte("abc\nnameserver 127.0.0.1\ndef"),
+			writtenData: "abc\nnameserver 127.0.0.1\ndef",
 		},
 	}
 	for name, tc := range tests {
@@ -49,18 +57,43 @@ func Test_UseDNSSystemWide(t *testing.T) {
 			t.Parallel()
 			mockCtrl := gomock.NewController(t)
 			defer mockCtrl.Finish()
-			fileManager := mock_files.NewMockFileManager(mockCtrl)
-			fileManager.EXPECT().ReadFile(string(constants.ResolvConf)).
-				Return(tc.data, tc.readErr)
-			if tc.readErr == nil {
-				fileManager.EXPECT().WriteToFile(string(constants.ResolvConf), tc.writtenData).
-					Return(tc.writeErr)
+
+			file := mock_os.NewMockFile(mockCtrl)
+			if tc.openErr == nil {
+				firstReadCall := file.EXPECT().
+					Read(gomock.AssignableToTypeOf([]byte{})).
+					DoAndReturn(func(b []byte) (int, error) {
+						copy(b, tc.data)
+						return len(tc.data), nil
+					})
+				readErr := tc.readErr
+				if readErr == nil {
+					readErr = io.EOF
+				}
+				finalReadCall := file.EXPECT().
+					Read(gomock.AssignableToTypeOf([]byte{})).
+					Return(0, readErr).After(firstReadCall)
+				if tc.readErr == nil {
+					writeCall := file.EXPECT().WriteString(tc.writtenData).
+						Return(0, tc.writeErr).After(finalReadCall)
+					file.EXPECT().Close().Return(tc.closeErr).After(writeCall)
+				} else {
+					file.EXPECT().Close().Return(tc.closeErr).After(finalReadCall)
+				}
 			}
+
+			openFile := func(name string, flag int, perm os.FileMode) (os.File, error) {
+				assert.Equal(t, string(constants.ResolvConf), name)
+				assert.Equal(t, os.O_RDWR, flag)
+				assert.Equal(t, os.FileMode(0644), perm)
+				return file, tc.openErr
+			}
+
 			logger := mock_logging.NewMockLogger(mockCtrl)
 			logger.EXPECT().Info("using DNS address %s system wide", "127.0.0.1")
 			c := &configurator{
-				fileManager: fileManager,
-				logger:      logger,
+				openFile: openFile,
+				logger:   logger,
 			}
 			err := c.UseDNSSystemWide(net.IP{127, 0, 0, 1}, false)
 			if tc.err != nil {

internal/dns/roots.go

@@ -4,37 +4,46 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"os"
 
 	"github.com/qdm12/gluetun/internal/constants"
-	"github.com/qdm12/golibs/files"
 )
 
 func (c *configurator) DownloadRootHints(ctx context.Context, uid, gid int) error {
-	c.logger.Info("downloading root hints from %s", constants.NamedRootURL)
-	content, status, err := c.client.Get(ctx, string(constants.NamedRootURL))
-	if err != nil {
-		return err
-	} else if status != http.StatusOK {
-		return fmt.Errorf("HTTP status code is %d for %s", status, constants.NamedRootURL)
-	}
-	return c.fileManager.WriteToFile(
-		string(constants.RootHints),
-		content,
-		files.Ownership(uid, gid),
-		files.Permissions(constants.UserReadPermission))
+	return c.downloadAndSave(ctx, "root hints",
+		string(constants.NamedRootURL), string(constants.RootHints), uid, gid)
 }
 
 func (c *configurator) DownloadRootKey(ctx context.Context, uid, gid int) error {
-	c.logger.Info("downloading root key from %s", constants.RootKeyURL)
-	content, status, err := c.client.Get(ctx, string(constants.RootKeyURL))
+	return c.downloadAndSave(ctx, "root key",
+		string(constants.RootKeyURL), string(constants.RootKey), uid, gid)
+}
+
+func (c *configurator) downloadAndSave(ctx context.Context, logName, url, filepath string, uid, gid int) error {
+	c.logger.Info("downloading %s from %s", logName, url)
+	content, status, err := c.client.Get(ctx, url)
 	if err != nil {
 		return err
 	} else if status != http.StatusOK {
-		return fmt.Errorf("HTTP status code is %d for %s", status, constants.RootKeyURL)
+		return fmt.Errorf("HTTP status code is %d for %s", status, url)
 	}
-	return c.fileManager.WriteToFile(
-		string(constants.RootKey),
-		content,
-		files.Ownership(uid, gid),
-		files.Permissions(constants.UserReadPermission))
+
+	file, err := c.openFile(filepath, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, 0400)
+	if err != nil {
+		return err
+	}
+
+	_, err = file.Write(content)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	err = file.Chown(uid, gid)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	return file.Close()
 }

internal/dns/roots_test.go

@@ -2,27 +2,31 @@ package dns
 
 import (
 	"context"
+	"errors"
 	"fmt"
 	"net/http"
 	"testing"
 
 	"github.com/golang/mock/gomock"
 	"github.com/qdm12/gluetun/internal/constants"
-	"github.com/qdm12/golibs/files"
-	"github.com/qdm12/golibs/files/mock_files"
+	"github.com/qdm12/gluetun/internal/os"
+	"github.com/qdm12/gluetun/internal/os/mock_os"
 	"github.com/qdm12/golibs/logging/mock_logging"
 	"github.com/qdm12/golibs/network/mock_network"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
 )
 
-func Test_DownloadRootHints(t *testing.T) { //nolint:dupl
+func Test_downloadAndSave(t *testing.T) {
 	t.Parallel()
 	tests := map[string]struct {
 		content   []byte
 		status    int
 		clientErr error
+		openErr   error
 		writeErr  error
+		chownErr  error
+		closeErr  error
 		err       error
 	}{
 		"no data": {
@@ -36,11 +40,26 @@ func Test_DownloadRootHints(t *testing.T) { //nolint:dupl
 			clientErr: fmt.Errorf("error"),
 			err:       fmt.Errorf("error"),
 		},
+		"open error": {
+			status:  http.StatusOK,
+			openErr: fmt.Errorf("error"),
+			err:     fmt.Errorf("error"),
+		},
 		"write error": {
 			status:   http.StatusOK,
 			writeErr: fmt.Errorf("error"),
 			err:      fmt.Errorf("error"),
 		},
+		"chown error": {
+			status:   http.StatusOK,
+			chownErr: fmt.Errorf("error"),
+			err:      fmt.Errorf("error"),
+		},
+		"close error": {
+			status:   http.StatusOK,
+			closeErr: fmt.Errorf("error"),
+			err:      fmt.Errorf("error"),
+		},
 		"data": {
 			content: []byte("content"),
 			status:  http.StatusOK,
@@ -52,23 +71,49 @@ func Test_DownloadRootHints(t *testing.T) { //nolint:dupl
 			t.Parallel()
 			mockCtrl := gomock.NewController(t)
 			defer mockCtrl.Finish()
+
 			ctx := context.Background()
 			logger := mock_logging.NewMockLogger(mockCtrl)
-			logger.EXPECT().Info("downloading root hints from %s", constants.NamedRootURL)
+			logger.EXPECT().Info("downloading %s from %s", "root hints", string(constants.NamedRootURL))
 			client := mock_network.NewMockClient(mockCtrl)
 			client.EXPECT().Get(ctx, string(constants.NamedRootURL)).
 				Return(tc.content, tc.status, tc.clientErr)
-			fileManager := mock_files.NewMockFileManager(mockCtrl)
-			if tc.clientErr == nil && tc.status == http.StatusOK {
-				fileManager.EXPECT().WriteToFile(
-					string(constants.RootHints),
-					tc.content,
-					gomock.AssignableToTypeOf(files.Ownership(0, 0)),
-					gomock.AssignableToTypeOf(files.Ownership(0, 0))).
-					Return(tc.writeErr)
+
+			openFile := func(name string, flag int, perm os.FileMode) (os.File, error) {
+				return nil, nil
 			}
-			c := &configurator{logger: logger, client: client, fileManager: fileManager}
-			err := c.DownloadRootHints(ctx, 1000, 1000)
+
+			if tc.clientErr == nil && tc.status == http.StatusOK {
+				file := mock_os.NewMockFile(mockCtrl)
+				if tc.openErr == nil {
+					writeCall := file.EXPECT().Write(tc.content).
+						Return(0, tc.writeErr)
+					if tc.writeErr != nil {
+						file.EXPECT().Close().Return(tc.closeErr).After(writeCall)
+					} else {
+						chownCall := file.EXPECT().Chown(1000, 1000).Return(tc.chownErr).After(writeCall)
+						file.EXPECT().Close().Return(tc.closeErr).After(chownCall)
+					}
+				}
+
+				openFile = func(name string, flag int, perm os.FileMode) (os.File, error) {
+					assert.Equal(t, string(constants.RootHints), name)
+					assert.Equal(t, os.O_WRONLY|os.O_TRUNC|os.O_CREATE, flag)
+					assert.Equal(t, os.FileMode(0400), perm)
+					return file, tc.openErr
+				}
+			}
+
+			c := &configurator{
+				logger:   logger,
+				client:   client,
+				openFile: openFile,
+			}
+
+			err := c.downloadAndSave(ctx, "root hints",
+				string(constants.NamedRootURL), string(constants.RootHints),
+				1000, 1000)
+
 			if tc.err != nil {
 				require.Error(t, err)
 				assert.Equal(t, tc.err.Error(), err.Error())
@@ -79,65 +124,44 @@ func Test_DownloadRootHints(t *testing.T) { //nolint:dupl
 	}
 }
 
-func Test_DownloadRootKey(t *testing.T) { //nolint:dupl
+func Test_DownloadRootHints(t *testing.T) {
 	t.Parallel()
-	tests := map[string]struct {
-		content   []byte
-		status    int
-		clientErr error
-		writeErr  error
-		err       error
-	}{
-		"no data": {
-			status: http.StatusOK,
-		},
-		"bad status": {
-			status: http.StatusBadRequest,
-			err:    fmt.Errorf("HTTP status code is 400 for https://raw.githubusercontent.com/qdm12/files/master/root.key.updated"), //nolint:lll
-		},
-		"client error": {
-			clientErr: fmt.Errorf("error"),
-			err:       fmt.Errorf("error"),
-		},
-		"write error": {
-			status:   http.StatusOK,
-			writeErr: fmt.Errorf("error"),
-			err:      fmt.Errorf("error"),
-		},
-		"data": {
-			content: []byte("content"),
-			status:  http.StatusOK,
-		},
-	}
-	for name, tc := range tests {
-		tc := tc
-		t.Run(name, func(t *testing.T) {
-			t.Parallel()
-			mockCtrl := gomock.NewController(t)
-			defer mockCtrl.Finish()
-			ctx := context.Background()
-			logger := mock_logging.NewMockLogger(mockCtrl)
-			logger.EXPECT().Info("downloading root key from %s", constants.RootKeyURL)
-			client := mock_network.NewMockClient(mockCtrl)
-			client.EXPECT().Get(ctx, string(constants.RootKeyURL)).
-				Return(tc.content, tc.status, tc.clientErr)
-			fileManager := mock_files.NewMockFileManager(mockCtrl)
-			if tc.clientErr == nil && tc.status == http.StatusOK {
-				fileManager.EXPECT().WriteToFile(
-					string(constants.RootKey),
-					tc.content,
-					gomock.AssignableToTypeOf(files.Ownership(0, 0)),
-					gomock.AssignableToTypeOf(files.Ownership(0, 0)),
-				).Return(tc.writeErr)
-			}
-			c := &configurator{logger: logger, client: client, fileManager: fileManager}
-			err := c.DownloadRootKey(ctx, 1000, 1001)
-			if tc.err != nil {
-				require.Error(t, err)
-				assert.Equal(t, tc.err.Error(), err.Error())
-			} else {
-				assert.NoError(t, err)
-			}
-		})
+	mockCtrl := gomock.NewController(t)
+
+	ctx := context.Background()
+	logger := mock_logging.NewMockLogger(mockCtrl)
+	logger.EXPECT().Info("downloading %s from %s", "root hints", string(constants.NamedRootURL))
+	client := mock_network.NewMockClient(mockCtrl)
+	client.EXPECT().Get(ctx, string(constants.NamedRootURL)).
+		Return(nil, http.StatusOK, errors.New("test"))
+
+	c := &configurator{
+		logger: logger,
+		client: client,
 	}
+
+	err := c.DownloadRootHints(ctx, 1000, 1000)
+	require.Error(t, err)
+	assert.Equal(t, "test", err.Error())
+}
+
+func Test_DownloadRootKey(t *testing.T) {
+	t.Parallel()
+	mockCtrl := gomock.NewController(t)
+
+	ctx := context.Background()
+	logger := mock_logging.NewMockLogger(mockCtrl)
+	logger.EXPECT().Info("downloading %s from %s", "root key", string(constants.RootKeyURL))
+	client := mock_network.NewMockClient(mockCtrl)
+	client.EXPECT().Get(ctx, string(constants.RootKeyURL)).
+		Return(nil, http.StatusOK, errors.New("test"))
+
+	c := &configurator{
+		logger: logger,
+		client: client,
+	}
+
+	err := c.DownloadRootKey(ctx, 1000, 1000)
+	require.Error(t, err)
+	assert.Equal(t, "test", err.Error())
 }

internal/firewall/firewall.go

@@ -6,9 +6,9 @@ import (
 	"sync"
 
 	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/routing"
 	"github.com/qdm12/golibs/command"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -29,7 +29,7 @@ type configurator struct { //nolint:maligned
 	commander        command.Commander
 	logger           logging.Logger
 	routing          routing.Routing
-	fileManager      files.FileManager // for custom iptables rules
+	openFile         os.OpenFileFunc // for custom iptables rules
 	iptablesMutex    sync.Mutex
 	debug            bool
 	defaultInterface string
@@ -47,12 +47,12 @@ type configurator struct { //nolint:maligned
 }
 
 // NewConfigurator creates a new Configurator instance.
-func NewConfigurator(logger logging.Logger, routing routing.Routing, fileManager files.FileManager) Configurator {
+func NewConfigurator(logger logging.Logger, routing routing.Routing, openFile os.OpenFileFunc) Configurator {
 	return &configurator{
 		commander:         command.NewCommander(),
 		logger:            logger.WithPrefix("firewall: "),
 		routing:           routing,
-		fileManager:       fileManager,
+		openFile:          openFile,
 		allowedInputPorts: make(map[uint16]string),
 	}
 }

internal/firewall/iptables.go

@@ -3,7 +3,9 @@ package firewall
 import (
 	"context"
 	"fmt"
+	"io/ioutil"
 	"net"
+	"os"
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/models"
@@ -150,14 +152,18 @@ func (c *configurator) acceptInputToPort(ctx context.Context, intf string, port
 }
 
 func (c *configurator) runUserPostRules(ctx context.Context, filepath string, remove bool) error {
-	exists, err := c.fileManager.FileExists(filepath)
-	if err != nil {
-		return err
-	} else if !exists {
+	file, err := c.openFile(filepath, os.O_RDONLY, 0)
+	if os.IsNotExist(err) {
 		return nil
+	} else if err != nil {
+		return err
 	}
-	b, err := c.fileManager.ReadFile(filepath)
+	b, err := ioutil.ReadAll(file)
 	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	if err := file.Close(); err != nil {
 		return err
 	}
 	lines := strings.Split(string(b), "\n")

internal/openvpn/auth.go

@@ -1,31 +1,68 @@
 package openvpn
 
 import (
+	"io/ioutil"
+	"os"
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/constants"
-	"github.com/qdm12/golibs/files"
 )
 
 // WriteAuthFile writes the OpenVPN auth file to disk with the right permissions.
 func (c *configurator) WriteAuthFile(user, password string, uid, gid int) error {
-	exists, err := c.fileManager.FileExists(string(constants.OpenVPNAuthConf))
-	if err != nil {
+	const filepath = string(constants.OpenVPNAuthConf)
+	file, err := c.os.OpenFile(filepath, os.O_RDONLY, 0)
+
+	if err != nil && !os.IsNotExist(err) {
 		return err
-	} else if exists {
-		data, err := c.fileManager.ReadFile(string(constants.OpenVPNAuthConf))
+	}
+
+	if os.IsNotExist(err) {
+		file, err = c.os.OpenFile(filepath, os.O_WRONLY|os.O_CREATE, 0400)
 		if err != nil {
 			return err
 		}
-		lines := strings.Split(string(data), "\n")
-		if len(lines) > 1 && lines[0] == user && lines[1] == password {
-			return nil
+		_, err = file.WriteString(user + "\n" + password)
+		if err != nil {
+			_ = file.Close()
+			return err
 		}
-		c.logger.Info("username and password changed", constants.OpenVPNAuthConf)
+		err = file.Chown(uid, gid)
+		if err != nil {
+			_ = file.Close()
+			return err
+		}
+		return file.Close()
 	}
-	return c.fileManager.WriteLinesToFile(
-		string(constants.OpenVPNAuthConf),
-		[]string{user, password},
-		files.Ownership(uid, gid),
-		files.Permissions(constants.UserReadPermission))
+
+	data, err := ioutil.ReadAll(file)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	if err := file.Close(); err != nil {
+		return err
+	}
+
+	lines := strings.Split(string(data), "\n")
+	if len(lines) > 1 && lines[0] == user && lines[1] == password {
+		return nil
+	}
+
+	c.logger.Info("username and password changed in %s", constants.OpenVPNAuthConf)
+	file, err = c.os.OpenFile(filepath, os.O_TRUNC|os.O_WRONLY, 0400)
+	if err != nil {
+		return err
+	}
+	_, err = file.WriteString(user + "\n" + password)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	err = file.Chown(uid, gid)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	return file.Close()
 }

internal/openvpn/loop.go

@@ -4,17 +4,18 @@ import (
 	"context"
 	"net"
 	"net/http"
+	"strings"
 	"sync"
 	"time"
 
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/provider"
 	"github.com/qdm12/gluetun/internal/routing"
 	"github.com/qdm12/gluetun/internal/settings"
 	"github.com/qdm12/golibs/command"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -43,7 +44,7 @@ type looper struct {
 	// Other objects
 	logger, pfLogger logging.Logger
 	client           *http.Client
-	fileManager      files.FileManager
+	openFile         os.OpenFileFunc
 	streamMerger     command.StreamMerger
 	cancel           context.CancelFunc
 	// Internal channels and locks
@@ -57,7 +58,7 @@ type looper struct {
 func NewLooper(settings settings.OpenVPN,
 	username string, uid, gid int, allServers models.AllServers,
 	conf Configurator, fw firewall.Configurator, routing routing.Routing,
-	logger logging.Logger, client *http.Client, fileManager files.FileManager,
+	logger logging.Logger, client *http.Client, openFile os.OpenFileFunc,
 	streamMerger command.StreamMerger, cancel context.CancelFunc) Looper {
 	return &looper{
 		state: state{
@@ -74,7 +75,7 @@ func NewLooper(settings settings.OpenVPN,
 		logger:             logger.WithPrefix("openvpn: "),
 		pfLogger:           logger.WithPrefix("port forwarding: "),
 		client:             client,
-		fileManager:        fileManager,
+		openFile:           openFile,
 		streamMerger:       streamMerger,
 		cancel:             cancel,
 		start:              make(chan struct{}),
@@ -115,8 +116,8 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 			settings.Auth,
 			settings.Provider.ExtraConfigOptions,
 		)
-		if err := l.fileManager.WriteLinesToFile(string(constants.OpenVPNConf), lines,
-			files.Ownership(l.uid, l.gid), files.Permissions(constants.UserReadPermission)); err != nil {
+
+		if err := writeOpenvpnConf(lines, l.openFile); err != nil {
 			l.logger.Error(err)
 			l.cancel()
 			return
@@ -239,6 +240,22 @@ func (l *looper) portForward(ctx context.Context, wg *sync.WaitGroup,
 		return settings.Provider.PortForwarding.Filepath
 	}
 	providerConf.PortForward(ctx,
-		client, l.fileManager, l.pfLogger,
+		client, l.openFile, l.pfLogger,
 		gateway, l.fw, syncState)
 }
+
+func writeOpenvpnConf(lines []string, openFile os.OpenFileFunc) error {
+	const filepath = string(constants.OpenVPNConf)
+	file, err := openFile(filepath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
+	if err != nil {
+		return err
+	}
+	_, err = file.WriteString(strings.Join(lines, "\n"))
+	if err != nil {
+		return err
+	}
+	if err := file.Close(); err != nil {
+		return err
+	}
+	return nil
+}

internal/openvpn/openvpn.go

@@ -3,10 +3,9 @@ package openvpn
 import (
 	"context"
 	"io"
-	"os"
 
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/command"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 	"golang.org/x/sys/unix"
 )
@@ -20,21 +19,19 @@ type Configurator interface {
 }
 
 type configurator struct {
-	fileManager files.FileManager
-	logger      logging.Logger
-	commander   command.Commander
-	openFile    func(name string, flag int, perm os.FileMode) (*os.File, error)
-	mkDev       func(major uint32, minor uint32) uint64
-	mkNod       func(path string, mode uint32, dev int) error
+	logger    logging.Logger
+	commander command.Commander
+	os        os.OS
+	mkDev     func(major uint32, minor uint32) uint64
+	mkNod     func(path string, mode uint32, dev int) error
 }
 
-func NewConfigurator(logger logging.Logger, fileManager files.FileManager) Configurator {
+func NewConfigurator(logger logging.Logger, os os.OS) Configurator {
 	return &configurator{
-		fileManager: fileManager,
-		logger:      logger.WithPrefix("openvpn configurator: "),
-		commander:   command.NewCommander(),
-		openFile:    os.OpenFile,
-		mkDev:       unix.Mkdev,
-		mkNod:       unix.Mknod,
+		logger:    logger.WithPrefix("openvpn configurator: "),
+		commander: command.NewCommander(),
+		os:        os,
+		mkDev:     unix.Mkdev,
+		mkNod:     unix.Mknod,
 	}
 }

internal/openvpn/tun.go

@@ -11,7 +11,7 @@ import (
 // CheckTUN checks the tunnel device is present and accessible.
 func (c *configurator) CheckTUN() error {
 	c.logger.Info("checking for device %s", constants.TunnelDevice)
-	f, err := c.openFile(string(constants.TunnelDevice), os.O_RDWR, 0)
+	f, err := c.os.OpenFile(string(constants.TunnelDevice), os.O_RDWR, 0)
 	if err != nil {
 		return fmt.Errorf("TUN device is not available: %w", err)
 	}
@@ -23,9 +23,10 @@ func (c *configurator) CheckTUN() error {
 
 func (c *configurator) CreateTUN() error {
 	c.logger.Info("creating %s", constants.TunnelDevice)
-	if err := c.fileManager.CreateDir("/dev/net"); err != nil {
+	if err := c.os.MkdirAll("/dev/net", 0751); err != nil {
 		return err
 	}
+
 	const (
 		major = 10
 		minor = 200
@@ -34,8 +35,17 @@ func (c *configurator) CreateTUN() error {
 	if err := c.mkNod(string(constants.TunnelDevice), unix.S_IFCHR, int(dev)); err != nil {
 		return err
 	}
-	if err := c.fileManager.SetUserPermissions(string(constants.TunnelDevice), 0666); err != nil {
+
+	const filepath = string(constants.TunnelDevice)
+	file, err := c.os.OpenFile(filepath, os.O_WRONLY, 0666)
+	if err != nil {
 		return err
 	}
-	return nil
+	const readWriteAllPerms os.FileMode = 0666
+	if err := file.Chmod(readWriteAllPerms); err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	return file.Close()
 }

internal/os/alias.go

@@ -0,0 +1,9 @@
+package os
+
+import nativeos "os"
+
+// Aliases used for convenience so "os" does not have to be imported
+
+type FileMode nativeos.FileMode
+
+var IsNotExist = nativeos.IsNotExist

internal/os/constants.go

@@ -0,0 +1,16 @@
+package os
+
+import (
+	nativeos "os"
+)
+
+// Constants used for convenience so "os" does not have to be imported
+
+//nolint:golint
+const (
+	O_CREATE = nativeos.O_CREATE
+	O_TRUNC  = nativeos.O_TRUNC
+	O_WRONLY = nativeos.O_WRONLY
+	O_RDONLY = nativeos.O_RDONLY
+	O_RDWR   = nativeos.O_RDWR
+)

internal/os/file.go

@@ -0,0 +1,15 @@
+package os
+
+import (
+	"io"
+	nativeos "os"
+)
+
+//go:generate mockgen -destination=mock_$GOPACKAGE/$GOFILE . File
+
+type File interface {
+	io.ReadWriteCloser
+	WriteString(s string) (int, error)
+	Chown(uid, gid int) error
+	Chmod(mode nativeos.FileMode) error
+}

internal/os/funcs.go

@@ -0,0 +1,10 @@
+package os
+
+import (
+	nativeos "os"
+)
+
+type OpenFileFunc func(name string, flag int, perm FileMode) (File, error)
+type MkdirAllFunc func(name string, perm nativeos.FileMode) error
+type RemoveFunc func(name string) error
+type ChownFunc func(name string, uid int, gid int) error

internal/os/mock_os/file.go

@@ -0,0 +1,121 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/gluetun/internal/os (interfaces: File)
+
+// Package mock_os is a generated GoMock package.
+package mock_os
+
+import (
+	gomock "github.com/golang/mock/gomock"
+	os "os"
+	reflect "reflect"
+)
+
+// MockFile is a mock of File interface
+type MockFile struct {
+	ctrl     *gomock.Controller
+	recorder *MockFileMockRecorder
+}
+
+// MockFileMockRecorder is the mock recorder for MockFile
+type MockFileMockRecorder struct {
+	mock *MockFile
+}
+
+// NewMockFile creates a new mock instance
+func NewMockFile(ctrl *gomock.Controller) *MockFile {
+	mock := &MockFile{ctrl: ctrl}
+	mock.recorder = &MockFileMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use
+func (m *MockFile) EXPECT() *MockFileMockRecorder {
+	return m.recorder
+}
+
+// Chmod mocks base method
+func (m *MockFile) Chmod(arg0 os.FileMode) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Chmod", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Chmod indicates an expected call of Chmod
+func (mr *MockFileMockRecorder) Chmod(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Chmod", reflect.TypeOf((*MockFile)(nil).Chmod), arg0)
+}
+
+// Chown mocks base method
+func (m *MockFile) Chown(arg0, arg1 int) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Chown", arg0, arg1)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Chown indicates an expected call of Chown
+func (mr *MockFileMockRecorder) Chown(arg0, arg1 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Chown", reflect.TypeOf((*MockFile)(nil).Chown), arg0, arg1)
+}
+
+// Close mocks base method
+func (m *MockFile) Close() error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Close")
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Close indicates an expected call of Close
+func (mr *MockFileMockRecorder) Close() *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Close", reflect.TypeOf((*MockFile)(nil).Close))
+}
+
+// Read mocks base method
+func (m *MockFile) Read(arg0 []byte) (int, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Read", arg0)
+	ret0, _ := ret[0].(int)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Read indicates an expected call of Read
+func (mr *MockFileMockRecorder) Read(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Read", reflect.TypeOf((*MockFile)(nil).Read), arg0)
+}
+
+// Write mocks base method
+func (m *MockFile) Write(arg0 []byte) (int, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Write", arg0)
+	ret0, _ := ret[0].(int)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Write indicates an expected call of Write
+func (mr *MockFileMockRecorder) Write(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Write", reflect.TypeOf((*MockFile)(nil).Write), arg0)
+}
+
+// WriteString mocks base method
+func (m *MockFile) WriteString(arg0 string) (int, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "WriteString", arg0)
+	ret0, _ := ret[0].(int)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// WriteString indicates an expected call of WriteString
+func (mr *MockFileMockRecorder) WriteString(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "WriteString", reflect.TypeOf((*MockFile)(nil).WriteString), arg0)
+}

internal/os/mock_os/os.go

@@ -0,0 +1,121 @@
+// Code generated by MockGen. DO NOT EDIT.
+// Source: github.com/qdm12/gluetun/internal/os (interfaces: OS)
+
+// Package mock_os is a generated GoMock package.
+package mock_os
+
+import (
+	gomock "github.com/golang/mock/gomock"
+	os "github.com/qdm12/gluetun/internal/os"
+	os0 "os"
+	reflect "reflect"
+)
+
+// MockOS is a mock of OS interface
+type MockOS struct {
+	ctrl     *gomock.Controller
+	recorder *MockOSMockRecorder
+}
+
+// MockOSMockRecorder is the mock recorder for MockOS
+type MockOSMockRecorder struct {
+	mock *MockOS
+}
+
+// NewMockOS creates a new mock instance
+func NewMockOS(ctrl *gomock.Controller) *MockOS {
+	mock := &MockOS{ctrl: ctrl}
+	mock.recorder = &MockOSMockRecorder{mock}
+	return mock
+}
+
+// EXPECT returns an object that allows the caller to indicate expected use
+func (m *MockOS) EXPECT() *MockOSMockRecorder {
+	return m.recorder
+}
+
+// Chown mocks base method
+func (m *MockOS) Chown(arg0 string, arg1, arg2 int) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Chown", arg0, arg1, arg2)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Chown indicates an expected call of Chown
+func (mr *MockOSMockRecorder) Chown(arg0, arg1, arg2 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Chown", reflect.TypeOf((*MockOS)(nil).Chown), arg0, arg1, arg2)
+}
+
+// MkdirAll mocks base method
+func (m *MockOS) MkdirAll(arg0 string, arg1 os.FileMode) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "MkdirAll", arg0, arg1)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// MkdirAll indicates an expected call of MkdirAll
+func (mr *MockOSMockRecorder) MkdirAll(arg0, arg1 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "MkdirAll", reflect.TypeOf((*MockOS)(nil).MkdirAll), arg0, arg1)
+}
+
+// OpenFile mocks base method
+func (m *MockOS) OpenFile(arg0 string, arg1 int, arg2 os.FileMode) (os.File, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "OpenFile", arg0, arg1, arg2)
+	ret0, _ := ret[0].(os.File)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// OpenFile indicates an expected call of OpenFile
+func (mr *MockOSMockRecorder) OpenFile(arg0, arg1, arg2 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "OpenFile", reflect.TypeOf((*MockOS)(nil).OpenFile), arg0, arg1, arg2)
+}
+
+// Remove mocks base method
+func (m *MockOS) Remove(arg0 string) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Remove", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Remove indicates an expected call of Remove
+func (mr *MockOSMockRecorder) Remove(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Remove", reflect.TypeOf((*MockOS)(nil).Remove), arg0)
+}
+
+// Stat mocks base method
+func (m *MockOS) Stat(arg0 string) (os0.FileInfo, error) {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Stat", arg0)
+	ret0, _ := ret[0].(os0.FileInfo)
+	ret1, _ := ret[1].(error)
+	return ret0, ret1
+}
+
+// Stat indicates an expected call of Stat
+func (mr *MockOSMockRecorder) Stat(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Stat", reflect.TypeOf((*MockOS)(nil).Stat), arg0)
+}
+
+// Unsetenv mocks base method
+func (m *MockOS) Unsetenv(arg0 string) error {
+	m.ctrl.T.Helper()
+	ret := m.ctrl.Call(m, "Unsetenv", arg0)
+	ret0, _ := ret[0].(error)
+	return ret0
+}
+
+// Unsetenv indicates an expected call of Unsetenv
+func (mr *MockOSMockRecorder) Unsetenv(arg0 interface{}) *gomock.Call {
+	mr.mock.ctrl.T.Helper()
+	return mr.mock.ctrl.RecordCallWithMethodType(mr.mock, "Unsetenv", reflect.TypeOf((*MockOS)(nil).Unsetenv), arg0)
+}

internal/os/os.go

@@ -0,0 +1,39 @@
+package os
+
+import nativeos "os"
+
+//go:generate mockgen -destination=mock_$GOPACKAGE/$GOFILE . OS
+
+type OS interface {
+	OpenFile(name string, flag int, perm FileMode) (File, error)
+	MkdirAll(name string, perm FileMode) error
+	Remove(name string) error
+	Chown(name string, uid int, gid int) error
+	Unsetenv(key string) error
+	Stat(name string) (nativeos.FileInfo, error)
+}
+
+func New() OS {
+	return &os{}
+}
+
+type os struct{}
+
+func (o *os) OpenFile(name string, flag int, perm FileMode) (File, error) {
+	return nativeos.OpenFile(name, flag, nativeos.FileMode(perm))
+}
+func (o *os) MkdirAll(name string, perm FileMode) error {
+	return nativeos.MkdirAll(name, nativeos.FileMode(perm))
+}
+func (o *os) Remove(name string) error {
+	return nativeos.Remove(name)
+}
+func (o *os) Chown(name string, uid, gid int) error {
+	return nativeos.Chown(name, uid, gid)
+}
+func (o *os) Unsetenv(key string) error {
+	return nativeos.Unsetenv(key)
+}
+func (o *os) Stat(name string) (nativeos.FileInfo, error) {
+	return nativeos.Stat(name)
+}

internal/params/cyberghost.go

@@ -3,6 +3,8 @@ package params
 import (
 	"encoding/pem"
 	"fmt"
+	"io/ioutil"
+	"os"
 	"strings"
 
 	"github.com/qdm12/gluetun/internal/constants"
@@ -32,10 +34,19 @@ func (p *reader) GetCyberghostClientKey() (clientKey string, err error) {
 	} else if len(clientKey) > 0 {
 		return clientKey, nil
 	}
-	content, err := p.fileManager.ReadFile(string(constants.ClientKey))
+	const filepath = string(constants.ClientKey)
+	file, err := p.os.OpenFile(filepath, os.O_RDONLY, 0)
 	if err != nil {
 		return "", err
 	}
+	content, err := ioutil.ReadAll(file)
+	if err != nil {
+		_ = file.Close()
+		return "", err
+	}
+	if err := file.Close(); err != nil {
+		return "", err
+	}
 	return extractClientKey(content)
 }
 
@@ -55,10 +66,19 @@ func extractClientKey(b []byte) (key string, err error) {
 // GetCyberghostClientCertificate obtains the client certificate to use for openvpn from the
 // file at /gluetun/client.crt.
 func (p *reader) GetCyberghostClientCertificate() (clientCertificate string, err error) {
-	content, err := p.fileManager.ReadFile(string(constants.ClientCertificate))
+	const filepath = string(constants.ClientCertificate)
+	file, err := p.os.OpenFile(filepath, os.O_RDONLY, 0)
 	if err != nil {
 		return "", err
 	}
+	content, err := ioutil.ReadAll(file)
+	if err != nil {
+		_ = file.Close()
+		return "", err
+	}
+	if err := file.Close(); err != nil {
+		return "", err
+	}
 	return extractClientCertificate(content)
 }
 

internal/params/openvpn.go

@@ -11,7 +11,7 @@ import (
 // GetUser obtains the user to use to connect to the VPN servers.
 func (r *reader) GetUser() (s string, err error) {
 	defer func() {
-		unsetenvErr := r.unsetEnv("USER")
+		unsetenvErr := r.os.Unsetenv("USER")
 		if err == nil {
 			err = unsetenvErr
 		}
@@ -22,7 +22,7 @@ func (r *reader) GetUser() (s string, err error) {
 // GetPassword obtains the password to use to connect to the VPN servers.
 func (r *reader) GetPassword(required bool) (s string, err error) {
 	defer func() {
-		unsetenvErr := r.unsetEnv("PASSWORD")
+		unsetenvErr := r.os.Unsetenv("PASSWORD")
 		if err == nil {
 			err = unsetenvErr
 		}

internal/params/params.go

@@ -2,11 +2,10 @@ package params
 
 import (
 	"net"
-	"os"
 	"time"
 
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 	libparams "github.com/qdm12/golibs/params"
 	"github.com/qdm12/golibs/verification"
@@ -128,22 +127,20 @@ type Reader interface {
 }
 
 type reader struct {
-	envParams   libparams.EnvParams
-	logger      logging.Logger
-	verifier    verification.Verifier
-	unsetEnv    func(key string) error
-	fileManager files.FileManager
+	envParams libparams.EnvParams
+	logger    logging.Logger
+	verifier  verification.Verifier
+	os        os.OS
 }
 
 // Newreader returns a paramsReadeer object to read parameters from
 // environment variables.
-func NewReader(logger logging.Logger, fileManager files.FileManager) Reader {
+func NewReader(logger logging.Logger, os os.OS) Reader {
 	return &reader{
-		envParams:   libparams.NewEnvParams(),
-		logger:      logger,
-		verifier:    verification.NewVerifier(),
-		unsetEnv:    os.Unsetenv,
-		fileManager: fileManager,
+		envParams: libparams.NewEnvParams(),
+		logger:    logger,
+		verifier:  verification.NewVerifier(),
+		os:        os,
 	}
 }
 

internal/params/shadowsocks.go

@@ -36,7 +36,7 @@ func (r *reader) GetShadowSocksPort() (port uint16, err error) {
 // SHADOWSOCKS_PASSWORD.
 func (r *reader) GetShadowSocksPassword() (password string, err error) {
 	defer func() {
-		unsetErr := r.unsetEnv("SHADOWSOCKS_PASSWORD")
+		unsetErr := r.os.Unsetenv("SHADOWSOCKS_PASSWORD")
 		if err == nil {
 			err = unsetErr
 		}

internal/provider/cyberghost.go

@@ -11,7 +11,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -133,7 +133,7 @@ func (c *cyberghost) BuildConf(connection models.OpenVPNConnection, verbosity in
 }
 
 func (c *cyberghost) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for cyberghost")
 }

internal/provider/mullvad.go

@@ -10,7 +10,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -128,7 +128,7 @@ func (m *mullvad) BuildConf(connection models.OpenVPNConnection,
 }
 
 func (m *mullvad) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for mullvad")
 }

internal/provider/nordvpn.go

@@ -10,7 +10,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -142,7 +142,7 @@ func (n *nordvpn) BuildConf(connection models.OpenVPNConnection, verbosity int,
 }
 
 func (n *nordvpn) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for nordvpn")
 }

internal/provider/piav4.go

@@ -19,7 +19,7 @@ import (
 	"github.com/qdm12/gluetun/internal/firewall"
 	gluetunLog "github.com/qdm12/gluetun/internal/logging"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -183,7 +183,7 @@ func (p *pia) BuildConf(connection models.OpenVPNConnection, verbosity int, user
 
 //nolint:gocognit
 func (p *pia) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	if !p.activeServer.PortForward {
 		pfLogger.Error("The server %s does not support port forwarding", p.activeServer.Region)
@@ -203,7 +203,7 @@ func (p *pia) PortForward(ctx context.Context, client *http.Client,
 		return
 	}
 	defer pfLogger.Warn("loop exited")
-	data, err := readPIAPortForwardData(fileManager)
+	data, err := readPIAPortForwardData(openFile)
 	if err != nil {
 		pfLogger.Error(err)
 	}
@@ -222,7 +222,7 @@ func (p *pia) PortForward(ctx context.Context, client *http.Client,
 
 	if !dataFound || expired {
 		tryUntilSuccessful(ctx, pfLogger, func() error {
-			data, err = refreshPIAPortForwardData(ctx, client, gateway, fileManager)
+			data, err = refreshPIAPortForwardData(ctx, client, gateway, openFile)
 			return err
 		})
 		if ctx.Err() != nil {
@@ -240,12 +240,9 @@ func (p *pia) PortForward(ctx context.Context, client *http.Client,
 		return
 	}
 
-	filepath := syncState(data.Port)
+	filepath := string(syncState(data.Port))
 	pfLogger.Info("Writing port to %s", filepath)
-	if err := fileManager.WriteToFile(
-		string(filepath), []byte(fmt.Sprintf("%d", data.Port)),
-		files.Permissions(constants.AllReadWritePermissions),
-	); err != nil {
+	if err := writePortForwardedToFile(openFile, filepath, data.Port); err != nil {
 		pfLogger.Error(err)
 	}
 
@@ -281,7 +278,7 @@ func (p *pia) PortForward(ctx context.Context, client *http.Client,
 			pfLogger.Warn("Forward port has expired on %s, getting another one", data.Expiration.Format(time.RFC1123))
 			oldPort := data.Port
 			for {
-				data, err = refreshPIAPortForwardData(ctx, client, gateway, fileManager)
+				data, err = refreshPIAPortForwardData(ctx, client, gateway, openFile)
 				if err != nil {
 					pfLogger.Error(err)
 					continue
@@ -298,10 +295,7 @@ func (p *pia) PortForward(ctx context.Context, client *http.Client,
 			}
 			filepath := syncState(data.Port)
 			pfLogger.Info("Writing port to %s", filepath)
-			if err := fileManager.WriteToFile(
-				string(filepath), []byte(fmt.Sprintf("%d", data.Port)),
-				files.Permissions(constants.AllReadWritePermissions),
-			); err != nil {
+			if err := writePortForwardedToFile(openFile, string(filepath), data.Port); err != nil {
 				pfLogger.Error(err)
 			}
 			if err := bindPIAPort(ctx, client, gateway, data); err != nil {
@@ -365,8 +359,8 @@ func newPIAHTTPClient(serverName string) (client *http.Client, err error) {
 }
 
 func refreshPIAPortForwardData(ctx context.Context, client *http.Client,
-	gateway net.IP, fileManager files.FileManager) (data piaPortForwardData, err error) {
-	data.Token, err = fetchPIAToken(ctx, fileManager, client)
+	gateway net.IP, openFile os.OpenFileFunc) (data piaPortForwardData, err error) {
+	data.Token, err = fetchPIAToken(ctx, openFile, client)
 	if err != nil {
 		return data, fmt.Errorf("cannot obtain token: %w", err)
 	}
@@ -374,7 +368,7 @@ func refreshPIAPortForwardData(ctx context.Context, client *http.Client,
 	if err != nil {
 		return data, fmt.Errorf("cannot obtain port forwarding data: %w", err)
 	}
-	if err := writePIAPortForwardData(fileManager, data); err != nil {
+	if err := writePIAPortForwardData(openFile, data); err != nil {
 		return data, fmt.Errorf("cannot persist port forwarding information to file: %w", err)
 	}
 	return data, nil
@@ -393,34 +387,39 @@ type piaPortForwardData struct {
 	Expiration time.Time `json:"expires_at"`
 }
 
-func readPIAPortForwardData(fileManager files.FileManager) (data piaPortForwardData, err error) {
+func readPIAPortForwardData(openFile os.OpenFileFunc) (data piaPortForwardData, err error) {
 	const filepath = string(constants.PIAPortForward)
-	exists, err := fileManager.FileExists(filepath)
-	if err != nil {
-		return data, err
-	} else if !exists {
+	file, err := openFile(filepath, os.O_RDONLY, 0)
+	if os.IsNotExist(err) {
 		return data, nil
+	} else if err != nil {
+		return data, err
 	}
-	b, err := fileManager.ReadFile(filepath)
+
+	decoder := json.NewDecoder(file)
+	err = decoder.Decode(&data)
 	if err != nil {
+		_ = file.Close()
 		return data, err
 	}
-	if err := json.Unmarshal(b, &data); err != nil {
-		return data, err
-	}
-	return data, nil
+	return data, file.Close()
 }
 
-func writePIAPortForwardData(fileManager files.FileManager, data piaPortForwardData) (err error) {
-	b, err := json.Marshal(&data)
-	if err != nil {
-		return fmt.Errorf("cannot encode data: %w", err)
-	}
-	err = fileManager.WriteToFile(string(constants.PIAPortForward), b)
+func writePIAPortForwardData(openFile os.OpenFileFunc, data piaPortForwardData) (err error) {
+	const filepath = string(constants.PIAPortForward)
+	file, err := openFile(filepath,
+		os.O_CREATE|os.O_TRUNC|os.O_WRONLY,
+		0644)
 	if err != nil {
 		return err
 	}
-	return nil
+	encoder := json.NewEncoder(file)
+	err = encoder.Encode(data)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	return file.Close()
 }
 
 func unpackPIAPayload(payload string) (port uint16, token string, expiration time.Time, err error) {
@@ -449,8 +448,9 @@ func packPIAPayload(port uint16, token string, expiration time.Time) (payload st
 	return payload, nil
 }
 
-func fetchPIAToken(ctx context.Context, fileManager files.FileManager, client *http.Client) (token string, err error) {
-	username, password, err := getOpenvpnCredentials(fileManager)
+func fetchPIAToken(ctx context.Context, openFile os.OpenFileFunc,
+	client *http.Client) (token string, err error) {
+	username, password, err := getOpenvpnCredentials(openFile)
 	if err != nil {
 		return "", fmt.Errorf("cannot get Openvpn credentials: %w", err)
 	}
@@ -489,10 +489,19 @@ func fetchPIAToken(ctx context.Context, fileManager files.FileManager, client *h
 	return result.Token, nil
 }
 
-func getOpenvpnCredentials(fileManager files.FileManager) (username, password string, err error) {
-	authData, err := fileManager.ReadFile(string(constants.OpenVPNAuthConf))
+func getOpenvpnCredentials(openFile os.OpenFileFunc) (username, password string, err error) {
+	const filepath = string(constants.OpenVPNAuthConf)
+	file, err := openFile(filepath, os.O_RDONLY, 0)
 	if err != nil {
-		return "", "", fmt.Errorf("cannot read openvpn auth file: %w", err)
+		return "", "", fmt.Errorf("cannot read openvpn auth file: %s", err)
+	}
+	authData, err := ioutil.ReadAll(file)
+	if err != nil {
+		_ = file.Close()
+		return "", "", fmt.Errorf("cannot read openvpn auth file: %s", err)
+	}
+	if err := file.Close(); err != nil {
+		return "", "", err
 	}
 	lines := strings.Split(string(authData), "\n")
 	const minLines = 2
@@ -586,3 +595,17 @@ func bindPIAPort(ctx context.Context, client *http.Client, gateway net.IP, data
 	}
 	return nil
 }
+
+func writePortForwardedToFile(openFile os.OpenFileFunc,
+	filepath string, port uint16) (err error) {
+	file, err := openFile(filepath, os.O_CREATE|os.O_TRUNC|os.O_WRONLY, 0644)
+	if err != nil {
+		return err
+	}
+	_, err = file.Write([]byte(fmt.Sprintf("%d", port)))
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+	return file.Close()
+}

internal/provider/privado.go

@@ -10,7 +10,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -117,7 +117,7 @@ func (s *privado) BuildConf(connection models.OpenVPNConnection, verbosity int,
 }
 
 func (s *privado) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for privado")
 }

internal/provider/provider.go

@@ -8,7 +8,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -18,7 +18,7 @@ type Provider interface {
 	BuildConf(connection models.OpenVPNConnection, verbosity int, username string,
 		root bool, cipher, auth string, extras models.ExtraConfigOptions) (lines []string)
 	PortForward(ctx context.Context, client *http.Client,
-		fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+		openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 		syncState func(port uint16) (pfFilepath models.Filepath))
 }
 

internal/provider/purevpn.go

@@ -10,7 +10,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -150,7 +150,7 @@ func (p *purevpn) BuildConf(connection models.OpenVPNConnection, verbosity int,
 }
 
 func (p *purevpn) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for purevpn")
 }

internal/provider/surfshark.go

@@ -10,7 +10,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -138,7 +138,7 @@ func (s *surfshark) BuildConf(connection models.OpenVPNConnection, verbosity int
 }
 
 func (s *surfshark) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for surfshark")
 }

internal/provider/vyprvpn.go

@@ -10,7 +10,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -119,7 +119,7 @@ func (v *vyprvpn) BuildConf(connection models.OpenVPNConnection, verbosity int,
 }
 
 func (v *vyprvpn) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for vyprvpn")
 }

internal/provider/windscribe.go

@@ -11,7 +11,7 @@ import (
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/firewall"
 	"github.com/qdm12/gluetun/internal/models"
-	"github.com/qdm12/golibs/files"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -132,7 +132,7 @@ func (w *windscribe) BuildConf(connection models.OpenVPNConnection, verbosity in
 }
 
 func (w *windscribe) PortForward(ctx context.Context, client *http.Client,
-	fileManager files.FileManager, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
+	openFile os.OpenFileFunc, pfLogger logging.Logger, gateway net.IP, fw firewall.Configurator,
 	syncState func(port uint16) (pfFilepath models.Filepath)) {
 	panic("port forwarding is not supported for windscribe")
 }

internal/publicip/fs.go

@@ -0,0 +1,27 @@
+package publicip
+
+import "github.com/qdm12/gluetun/internal/os"
+
+func persistPublicIP(openFile os.OpenFileFunc,
+	filepath string, content string, uid, gid int) error {
+	file, err := openFile(
+		filepath,
+		os.O_TRUNC|os.O_WRONLY|os.O_CREATE,
+		0644)
+	if err != nil {
+		return err
+	}
+
+	_, err = file.WriteString(content)
+	if err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	if err := file.Chown(uid, gid); err != nil {
+		_ = file.Close()
+		return err
+	}
+
+	return file.Close()
+}

internal/publicip/loop.go

@@ -8,8 +8,8 @@ import (
 
 	"github.com/qdm12/gluetun/internal/constants"
 	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/gluetun/internal/settings"
-	"github.com/qdm12/golibs/files"
 	"github.com/qdm12/golibs/logging"
 	"github.com/qdm12/golibs/network"
 )
@@ -27,9 +27,9 @@ type Looper interface {
 type looper struct {
 	state state
 	// Objects
-	getter      IPGetter
-	logger      logging.Logger
-	fileManager files.FileManager
+	getter IPGetter
+	logger logging.Logger
+	os     os.OS
 	// Fixed settings
 	uid int
 	gid int
@@ -45,8 +45,9 @@ type looper struct {
 	timeSince func(time.Time) time.Duration
 }
 
-func NewLooper(client network.Client, logger logging.Logger, fileManager files.FileManager,
-	settings settings.PublicIP, uid, gid int) Looper {
+func NewLooper(client network.Client, logger logging.Logger,
+	settings settings.PublicIP, uid, gid int,
+	os os.OS) Looper {
 	return &looper{
 		state: state{
 			status:   constants.Stopped,
@@ -55,7 +56,7 @@ func NewLooper(client network.Client, logger logging.Logger, fileManager files.F
 		// Objects
 		getter:       NewIPGetter(client),
 		logger:       logger.WithPrefix("ip getter: "),
-		fileManager:  fileManager,
+		os:           os,
 		uid:          uid,
 		gid:          gid,
 		start:        make(chan struct{}),
@@ -125,7 +126,7 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 				close(errorCh)
 				filepath := l.GetSettings().IPFilepath
 				l.logger.Info("Removing ip file %s", filepath)
-				if err := l.fileManager.Remove(string(filepath)); err != nil {
+				if err := l.os.Remove(string(filepath)); err != nil {
 					l.logger.Error(err)
 				}
 				return
@@ -142,12 +143,8 @@ func (l *looper) Run(ctx context.Context, wg *sync.WaitGroup) {
 				getCancel()
 				l.state.setPublicIP(ip)
 				l.logger.Info("Public IP address is %s", ip)
-				const userReadWritePermissions = 0600
-				err := l.fileManager.WriteLinesToFile(
-					string(l.state.settings.IPFilepath),
-					[]string{ip.String()},
-					files.Ownership(l.uid, l.gid),
-					files.Permissions(userReadWritePermissions))
+				filepath := string(l.state.settings.IPFilepath)
+				err := persistPublicIP(l.os.OpenFile, filepath, ip.String(), l.uid, l.gid)
 				if err != nil {
 					l.logger.Error(err)
 				}

internal/storage/storage.go

@@ -1,10 +1,8 @@
 package storage
 
 import (
-	"io/ioutil"
-	"os"
-
 	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/os"
 	"github.com/qdm12/golibs/logging"
 )
 
@@ -14,17 +12,13 @@ type Storage interface {
 }
 
 type storage struct {
-	osStat    func(name string) (os.FileInfo, error)
-	readFile  func(filename string) (data []byte, err error)
-	writeFile func(filename string, data []byte, perm os.FileMode) error
-	logger    logging.Logger
+	os     os.OS
+	logger logging.Logger
 }
 
-func New(logger logging.Logger) Storage {
+func New(logger logging.Logger, os os.OS) Storage {
 	return &storage{
-		osStat:    os.Stat,
-		readFile:  ioutil.ReadFile,
-		writeFile: ioutil.WriteFile,
-		logger:    logger.WithPrefix("storage: "),
+		os:     os,
+		logger: logger.WithPrefix("storage: "),
 	}
 }

internal/storage/sync.go

@@ -3,10 +3,10 @@ package storage
 import (
 	"encoding/json"
 	"fmt"
-	"os"
 	"reflect"
 
 	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/gluetun/internal/os"
 )
 
 const (
@@ -29,14 +29,18 @@ func (s *storage) SyncServers(hardcodedServers models.AllServers, write bool) (
 	allServers models.AllServers, err error) {
 	// Eventually read file
 	var serversOnFile models.AllServers
-	_, err = s.osStat(jsonFilepath)
+	file, err := s.os.OpenFile(jsonFilepath, os.O_RDONLY, 0)
+	if err != nil && !os.IsNotExist(err) {
+		return allServers, err
+	}
 	if err == nil {
-		serversOnFile, err = s.readFromFile()
-		if err != nil {
+		var serversOnFile models.AllServers
+		decoder := json.NewDecoder(file)
+		if err := decoder.Decode(&serversOnFile); err != nil {
+			_ = file.Close()
 			return allServers, err
 		}
-	} else if !os.IsNotExist(err) {
-		return allServers, err
+		return allServers, file.Close()
 	}
 
 	// Merge data from file and hardcoded
@@ -51,24 +55,16 @@ func (s *storage) SyncServers(hardcodedServers models.AllServers, write bool) (
 	return allServers, s.FlushToFile(allServers)
 }
 
-func (s *storage) readFromFile() (servers models.AllServers, err error) {
-	bytes, err := s.readFile(jsonFilepath)
-	if err != nil {
-		return servers, err
-	}
-	if err := json.Unmarshal(bytes, &servers); err != nil {
-		return servers, err
-	}
-	return servers, nil
-}
-
 func (s *storage) FlushToFile(servers models.AllServers) error {
-	bytes, err := json.MarshalIndent(servers, "", "  ")
+	file, err := s.os.OpenFile(jsonFilepath, os.O_CREATE|os.O_WRONLY|os.O_TRUNC, 0644)
 	if err != nil {
-		return fmt.Errorf("cannot write to file: %w", err)
-	}
-	if err := s.writeFile(jsonFilepath, bytes, 0644); err != nil {
 		return err
 	}
-	return nil
+	encoder := json.NewEncoder(file)
+	encoder.SetIndent("", "  ")
+	if err := encoder.Encode(servers); err != nil {
+		_ = file.Close()
+		return fmt.Errorf("cannot write to file: %w", err)
+	}
+	return file.Close()
 }