feat: socks5 proxy server (#3336)

- `SOCKS5_ENABLED=off`
- `SOCKS5_LISTENING_ADDRESS=":1080"`
- `SOCKS5_USER=`
- `SOCKS5_PASSWORD=`

internal/configuration/settings/settings.go

@@ -20,6 +20,7 @@ type Settings struct {
 	HTTPProxy     HTTPProxy
 	Log           Log
 	PublicIP      PublicIP
+	Socks5        Socks5
 	Shadowsocks   Shadowsocks
 	Storage       Storage
 	System        System
@@ -49,6 +50,7 @@ func (s *Settings) Validate(filterChoicesGetter FilterChoicesGetter, ipv6Support
 		"http proxy":      s.HTTPProxy.validate,
 		"log":             s.Log.validate,
 		"public ip check": s.PublicIP.validate,
+		"socks5":          s.Socks5.validate,
 		"shadowsocks":     s.Shadowsocks.validate,
 		"storage":         s.Storage.validate,
 		"system":          s.System.validate,
@@ -81,6 +83,7 @@ func (s *Settings) copy() (copied Settings) {
 		HTTPProxy:     s.HTTPProxy.copy(),
 		Log:           s.Log.copy(),
 		PublicIP:      s.PublicIP.copy(),
+		Socks5:        s.Socks5.copy(),
 		Shadowsocks:   s.Shadowsocks.copy(),
 		Storage:       s.Storage.copy(),
 		System:        s.System.copy(),
@@ -104,6 +107,7 @@ func (s *Settings) OverrideWith(other Settings,
 	patchedSettings.HTTPProxy.overrideWith(other.HTTPProxy)
 	patchedSettings.Log.overrideWith(other.Log)
 	patchedSettings.PublicIP.overrideWith(other.PublicIP)
+	patchedSettings.Socks5.overrideWith(other.Socks5)
 	patchedSettings.Shadowsocks.overrideWith(other.Shadowsocks)
 	patchedSettings.Storage.overrideWith(other.Storage)
 	patchedSettings.System.overrideWith(other.System)
@@ -131,6 +135,7 @@ func (s *Settings) SetDefaults() {
 	s.Log.setDefaults()
 	s.IPv6.setDefaults()
 	s.PublicIP.setDefaults()
+	s.Socks5.setDefaults()
 	s.Shadowsocks.setDefaults()
 	s.Storage.SetDefaults()
 	s.System.setDefaults()
@@ -154,6 +159,7 @@ func (s Settings) toLinesNode() (node *gotree.Node) {
 	node.AppendNode(s.Log.toLinesNode())
 	node.AppendNode(s.IPv6.toLinesNode())
 	node.AppendNode(s.Health.toLinesNode())
+	node.AppendNode(s.Socks5.toLinesNode())
 	node.AppendNode(s.Shadowsocks.toLinesNode())
 	node.AppendNode(s.HTTPProxy.toLinesNode())
 	node.AppendNode(s.ControlServer.toLinesNode())
@@ -212,6 +218,7 @@ func (s *Settings) Read(r *reader.Reader, warner Warner) (err error) {
 		"public ip": func(r *reader.Reader) error {
 			return s.PublicIP.read(r, warner)
 		},
+		"socks5":      s.Socks5.read,
 		"shadowsocks": s.Shadowsocks.read,
 		"storage":     s.Storage.Read,
 		"system":      s.System.read,

internal/configuration/settings/settings_test.go

@@ -81,6 +81,8 @@ func Test_Settings_String(t *testing.T) {
 |   |       ├── 1.1.1.1
 |   |       └── 8.8.8.8
 |   └── Restart VPN on healthcheck failure: yes
+├── SOCKS5 proxy server settings:
+|   └── Enabled: no
 ├── Shadowsocks server settings:
 |   └── Enabled: no
 ├── HTTP proxy settings:

internal/configuration/settings/socks5.go

@@ -0,0 +1,91 @@
+package settings
+
+import (
+	"errors"
+	"fmt"
+	"os"
+
+	"github.com/qdm12/gosettings"
+	"github.com/qdm12/gosettings/reader"
+	"github.com/qdm12/gosettings/validate"
+	"github.com/qdm12/gotree"
+)
+
+// Socks5 contains settings to configure the Socks5 proxy server.
+type Socks5 struct {
+	Enabled          *bool
+	ListeningAddress string
+	Username         *string
+	Password         *string
+}
+
+func (s Socks5) validate() (err error) {
+	err = validate.ListeningAddress(s.ListeningAddress, os.Getuid())
+	if err != nil {
+		return fmt.Errorf("server listening address is not valid: %w", err)
+	}
+
+	switch {
+	case *s.Username != "" && *s.Password == "":
+		return errors.New("password must be set if username is set")
+	case *s.Username == "" && *s.Password != "":
+		return errors.New("username must be set if password is set")
+	}
+
+	return nil
+}
+
+func (s *Socks5) copy() (copied Socks5) {
+	return Socks5{
+		Enabled:          gosettings.CopyPointer(s.Enabled),
+		ListeningAddress: s.ListeningAddress,
+		Username:         gosettings.CopyPointer(s.Username),
+		Password:         gosettings.CopyPointer(s.Password),
+	}
+}
+
+func (s *Socks5) overrideWith(other Socks5) {
+	s.Enabled = gosettings.OverrideWithPointer(s.Enabled, other.Enabled)
+	s.ListeningAddress = gosettings.OverrideWithComparable(s.ListeningAddress, other.ListeningAddress)
+	s.Username = gosettings.OverrideWithPointer(s.Username, other.Username)
+	s.Password = gosettings.OverrideWithPointer(s.Password, other.Password)
+}
+
+func (s *Socks5) setDefaults() {
+	s.Enabled = gosettings.DefaultPointer(s.Enabled, false)
+	s.ListeningAddress = gosettings.DefaultComparable(s.ListeningAddress, ":1080")
+	s.Username = gosettings.DefaultPointer(s.Username, "")
+	s.Password = gosettings.DefaultPointer(s.Password, "")
+}
+
+func (s Socks5) String() string {
+	return s.toLinesNode().String()
+}
+
+func (s Socks5) toLinesNode() (node *gotree.Node) {
+	node = gotree.New("SOCKS5 proxy server settings:")
+	node.Appendf("Enabled: %s", gosettings.BoolToYesNo(s.Enabled))
+	if !*s.Enabled {
+		return node
+	}
+
+	node.Appendf("Listening address: %s", s.ListeningAddress)
+	if *s.Username != "" || *s.Password != "" {
+		node.Appendf("Username: %s", *s.Username)
+		node.Appendf("Password: %s", gosettings.ObfuscateKey(*s.Password))
+	}
+	return node
+}
+
+func (s *Socks5) read(r *reader.Reader) (err error) {
+	s.Enabled, err = r.BoolPtr("SOCKS5_ENABLED")
+	if err != nil {
+		return err
+	}
+
+	s.ListeningAddress = r.String("SOCKS5_LISTENING_ADDRESS")
+	s.Username = r.Get("SOCKS5_USER", reader.ForceLowercase(false))
+	s.Password = r.Get("SOCKS5_PASSWORD", reader.ForceLowercase(false))
+
+	return nil
+}