Feature: custom Openvpn configuration file, fixes #223 (#402)

internal/openvpn/custom.go

@@ -0,0 +1,205 @@
+package openvpn
+
+import (
+	"errors"
+	"fmt"
+	"io"
+	"net"
+	"strconv"
+	"strings"
+
+	"github.com/qdm12/gluetun/internal/configuration"
+	"github.com/qdm12/gluetun/internal/constants"
+	"github.com/qdm12/gluetun/internal/models"
+	"github.com/qdm12/golibs/os"
+)
+
+var errProcessCustomConfig = errors.New("cannot process custom config")
+
+func (l *looper) processCustomConfig(settings configuration.OpenVPN) (
+	lines []string, connection models.OpenVPNConnection, err error) {
+	lines, err = readCustomConfigLines(settings.Config, l.openFile)
+	if err != nil {
+		return nil, connection, fmt.Errorf("%w: %s", errProcessCustomConfig, err)
+	}
+
+	lines = modifyCustomConfig(lines, l.username, settings)
+
+	connection, err = extractConnectionFromLines(lines)
+	if err != nil {
+		return nil, connection, fmt.Errorf("%w: %s", errProcessCustomConfig, err)
+	}
+
+	lines = setConnectionToLines(lines, connection)
+	return lines, connection, nil
+}
+
+func readCustomConfigLines(filepath string, openFile os.OpenFileFunc) (
+	lines []string, err error) {
+	file, err := openFile(filepath, os.O_RDONLY, 0)
+	if err != nil {
+		return nil, err
+	}
+	defer file.Close()
+
+	b, err := io.ReadAll(file)
+	if err != nil {
+		return nil, err
+	}
+
+	if err := file.Close(); err != nil {
+		return nil, err
+	}
+
+	return strings.Split(string(b), "\n"), nil
+}
+
+func modifyCustomConfig(lines []string, username string,
+	settings configuration.OpenVPN) (modified []string) {
+	// Remove some lines
+	for _, line := range lines {
+		switch {
+		case strings.HasPrefix(line, "up "),
+			strings.HasPrefix(line, "down "),
+			strings.HasPrefix(line, "verb "),
+			strings.HasPrefix(line, "auth-user-pass "),
+			len(settings.Cipher) > 0 && strings.HasPrefix(line, "cipher "),
+			len(settings.Auth) > 0 && strings.HasPrefix(line, "auth "),
+			settings.MSSFix > 0 && strings.HasPrefix(line, "mssfix "),
+			!settings.Provider.ExtraConfigOptions.OpenVPNIPv6 && strings.HasPrefix(line, "tun-ipv6"):
+		default:
+			modified = append(modified, line)
+		}
+	}
+
+	// Add values
+	modified = append(modified, "mute-replay-warnings")
+	modified = append(modified, "auth-nocache")
+	modified = append(modified, "pull-filter ignore \"auth-token\"") // prevent auth failed loop
+	modified = append(modified, `pull-filter ignore "ping-restart"`)
+	modified = append(modified, "auth-retry nointeract")
+	modified = append(modified, "suppress-timestamps")
+	modified = append(modified, "auth-user-pass "+constants.OpenVPNAuthConf)
+	modified = append(modified, "verb "+strconv.Itoa(settings.Verbosity))
+	if len(settings.Cipher) > 0 {
+		modified = append(modified, "cipher "+settings.Cipher)
+	}
+	if len(settings.Auth) > 0 {
+		modified = append(modified, "auth "+settings.Auth)
+	}
+	if settings.MSSFix > 0 {
+		modified = append(modified, "mssfix "+strconv.Itoa(int(settings.MSSFix)))
+	}
+	if !settings.Provider.ExtraConfigOptions.OpenVPNIPv6 {
+		modified = append(modified, `pull-filter ignore "route-ipv6"`)
+		modified = append(modified, `pull-filter ignore "ifconfig-ipv6"`)
+	}
+	if !settings.Root {
+		modified = append(modified, "user "+username)
+	}
+
+	return modified
+}
+
+var errExtractConnection = errors.New("cannot extract connection")
+
+// extractConnectionFromLines always takes the first remote line only.
+func extractConnectionFromLines(lines []string) ( //nolint:gocognit
+	connection models.OpenVPNConnection, err error) {
+	for _, line := range lines {
+		switch {
+		case strings.HasPrefix(line, "proto "):
+			fields := strings.Fields(line)
+			if n := len(fields); n != 2 { //nolint:gomnd
+				return connection, fmt.Errorf(
+					"%w: proto line has %d fields instead of 2: %s",
+					errExtractConnection, n, line)
+			}
+			connection.Protocol = fields[1]
+
+		// only take the first remote line
+		case strings.HasPrefix(line, "remote ") && connection.IP == nil:
+			fields := strings.Fields(line)
+			n := len(fields)
+			//nolint:gomnd
+			if n < 2 {
+				return connection, fmt.Errorf(
+					"%w: remote line has not enough fields: %s",
+					errExtractConnection, line)
+			}
+
+			host := fields[1]
+			if ip := net.ParseIP(host); ip != nil {
+				connection.IP = ip
+			} else {
+				return connection, fmt.Errorf(
+					"%w: for now, the remote line must contain an IP adddress: %s",
+					errExtractConnection, line)
+				// TODO resolve hostname once there is an option to allow it through
+				// the firewall before the VPN is up.
+			}
+
+			if n > 2 { //nolint:gomnd
+				port, err := strconv.Atoi(fields[2])
+				if err != nil {
+					return connection, fmt.Errorf(
+						"%w: remote line has an invalid port: %s",
+						errExtractConnection, line)
+				}
+				connection.Port = uint16(port)
+			}
+
+			if n > 3 { //nolint:gomnd
+				connection.Protocol = strings.ToLower(fields[3])
+			}
+
+			if n > 4 { //nolint:gomnd
+				return connection, fmt.Errorf(
+					"%w: remote line has too many fields: %s",
+					errExtractConnection, line)
+			}
+		}
+
+		if connection.Protocol != "" && connection.IP != nil {
+			break
+		}
+	}
+
+	if connection.IP == nil {
+		return connection, fmt.Errorf("%w: remote line not found", errExtractConnection)
+	}
+
+	switch connection.Protocol {
+	case "":
+		return connection, fmt.Errorf("%w: network protocol not found", errExtractConnection)
+	case "tcp", "udp":
+	default:
+		return connection, fmt.Errorf("%w: network protocol not supported: %s", errExtractConnection, connection.Protocol)
+	}
+
+	if connection.Port == 0 {
+		if connection.Protocol == "tcp" {
+			const defaultPort uint16 = 443
+			connection.Port = defaultPort
+		} else {
+			const defaultPort uint16 = 1194
+			connection.Port = defaultPort
+		}
+	}
+
+	return connection, nil
+}
+
+func setConnectionToLines(lines []string, connection models.OpenVPNConnection) (modified []string) {
+	for i, line := range lines {
+		switch {
+		case strings.HasPrefix(line, "proto "):
+			lines[i] = "proto " + connection.Protocol
+
+		case strings.HasPrefix(line, "remote "):
+			lines[i] = "remote " + connection.IP.String() + " " + strconv.Itoa(int(connection.Port))
+		}
+	}
+
+	return lines
+}