nmcli-vpn-activator/main.go

package main

import (
	"fmt"
	"os/exec"
	"regexp"

	"git.ohea.xyz/golang/config"
)

type Config struct {
	IgnoreDevices     bool
	Devices           []string
	IgnoreConnections bool
	Connections       []string
	VPNConnection     string
}

func isMatch(ignoreStrings bool, strings []string, match string) bool {
	if ignoreStrings {
		for _, s := range strings {
			if match == s {
				return false
			}
		}
		return true
	} else {
		for _, s := range strings {
			if match == s {
				return true
			}
		}
		return false
	}
}

func PrintArray(message string, items []string) {
	fmt.Printf("%s: ", message)
	for i, s := range items {
		fmt.Print(s)
		if i < len(items)-1 {
			fmt.Print(", ")
		}
	}
	fmt.Printf("\n")
}

func enableVPN(vpnCon string) error {
	cmd := exec.Command("nmcli", "con", "up", vpnCon)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("could not launch VPN: %w\n", err)
	}
	return nil
}

func disableVPN(vpnCon string) error {
	cmd := exec.Command("nmcli", "con", "down", vpnCon)
	if err := cmd.Run(); err != nil {
		return fmt.Errorf("could not stop VPN: %w\n", err)
	}
	return nil
}

func main() {
	configData := config.Config[Config]{
		Name:     "nmcli-vpn-activator",
		Filename: "config",
		Config: Config{
			IgnoreDevices:     false,
			Devices:           []string{},
			IgnoreConnections: true,
			Connections:       []string{},
			VPNConnection:     "",
		},
	}
	new, err := configData.Get()
	if err != nil {
		fmt.Printf("Could not get config: %w\n", err)
		return
	}

	if new {
		fmt.Println("New config created, please update and restart.")
		return
	}

	if configData.Config.IgnoreDevices {
		PrintArray("Ignoring the following devices", configData.Config.Devices)
	} else {
		PrintArray("Enabling the VPN on the following devices", configData.Config.Devices)
	}

	if configData.Config.IgnoreConnections {
		PrintArray("Ignoring the following connections", configData.Config.Connections)
	} else {
		PrintArray("Enabling the VPN on the following connections", configData.Config.Connections)
	}

	nmcli_monitor := exec.Command("nmcli", "monitor")

	stdout, err := nmcli_monitor.StdoutPipe()
	if err != nil {
		fmt.Printf("could not get stdout: %w\n", err)
		return
	}

	err = nmcli_monitor.Start()
	if err != nil {
		fmt.Printf("Could not start process: %w\n", err)
		return
	}

	buf := make([]byte, 1024)
	connectingEnable := false
	connectingDisable := false

	for {
		n, err := stdout.Read(buf)
		if err != nil {
			fmt.Printf("could not read stdout: %w\n, err")
			return
		}
		logLine := string(buf[:n])

		usingConnection := regexp.MustCompile(`(?P<device>\S+?): using connection \'(?P<network>.+?)\'`)
		results := usingConnection.FindStringSubmatch(logLine)
		if len(results) > 0 {
			if !isMatch(configData.Config.IgnoreDevices, configData.Config.Devices, results[1]) {
				continue
			}
			if !isMatch(configData.Config.IgnoreConnections, configData.Config.Connections, results[2]) {
				fmt.Printf("Monitored device %s has started connecting to VPN disabled network %s.\n", results[1], results[2])
				connectingDisable = true
				connectingEnable = false
			} else {
				fmt.Printf("Monitored device %s has started connecting to VPN enabled network %s.\n", results[1], results[2])
				connectingEnable = true
				connectingDisable = false
			}
			continue
		}

		deviceConnected := regexp.MustCompile(`(?P<device>\S+?): connected`)
		results = deviceConnected.FindStringSubmatch(logLine)
		if len(results) > 0 {
			if connectingEnable {
				fmt.Printf("Monitored device %s has connected to VPN enabled network, enabling VPN.\n", results[1])
				err = enableVPN(configData.Config.VPNConnection)
				if err != nil {
					fmt.Printf("Could not enable VPN: %w\n", err)
				}
				connectingEnable = false
			}
			if connectingDisable {
				fmt.Printf("Monitored device %s has connected to VPN disabled network, disabling VPN.\n", results[1])
				err = disableVPN(configData.Config.VPNConnection)
				if err != nil {
					fmt.Printf("Could not disable VPN: %w\n", err)
				}
				connectingDisable = false
			}
		}

	}
}