wireguard-mfa_windows/main.go

package main

import (
	// External
	"golang.zx2c4.com/wireguard/wgctrl/wgtypes"

	// Standard
	"errors"
	"flag"
	"fmt"
	"io/fs"
	"net/url"
	"os"
	"os/exec"
	"regexp"
	"time"
)

const VERSION = "v1"
const SPOOLDIR = "C:\\Program Files\\Gibon\\wg-spool"
const DOMAIN = "https://vpn.gibonuddevalla.se"

var (
	publicKeyPath      string
	runInteractiveAuth bool
	connected          bool
	printVersion       bool
)

func init() {
	flag.BoolVar(&printVersion, "version", false, "print version and exit")
	flag.BoolVar(&runInteractiveAuth, "interactive", false, "run interactive authentication")
	flag.BoolVar(&connected, "connected", false, "postop, is connected")
	flag.Parse()

	if printVersion {
		fmt.Println(VERSION)
		os.Exit(0)
	}
}

func logError(where, e string) {
	fmt.Printf("ERROR: %s\n", e)
	fname := fmt.Sprintf("%s\\log.txt", SPOOLDIR)
	file, err := os.OpenFile(fname, os.O_CREATE|os.O_APPEND, 0644)
	if err != nil {
		fmt.Println(err)
		os.Exit(1)
	}
	defer file.Close()

	now := time.Now().String()
	file.Write([]byte(now))
	file.Write([]byte("\t"))
	file.Write([]byte(where))
	file.Write([]byte("\t"))
	file.Write([]byte(e))
	file.Write([]byte("\n"))
}

func main() {
	publicKeyPath = SPOOLDIR + "\\wireguard-mfa.url"
	iface := os.Getenv("WIREGUARD_TUNNEL_NAME")

	// Run from PreUp, step 1.
	// Starts an interactive process, dropping privileges,
	// in order to have permission to open a browser in step 2.
	// Doesn't have permission to get public key.
	if !runInteractiveAuth && !connected {
		ex, _ := os.Executable()
		if err := StartProcessAsCurrentUser("", ex+" -interactive", ""); err != nil {
			logError("start_interactive", err.Error())
		}
		os.Exit(0)
	}

	// Started from PreUp, step 2.
	// Doesn't have permission to get public key.
	if runInteractiveAuth {
		var err error
		start := time.Now()
		for {
			// Abort after 60 seconds to not have an eternal loop.
			if time.Since(start).Seconds() > 60 {
				os.Exit(1)
			}

			_, err = os.ReadFile(publicKeyPath)
			if err != nil {
				if errors.Is(err, fs.ErrNotExist) {
					time.Sleep(time.Millisecond * 200)
					continue
				}

				if !errors.Is(err, fs.ErrNotExist) {
					logError("read_publickey_file", err.Error())
					os.Exit(1)
				}
			}
			break
		}

		cmd := exec.Command("rundll32.exe", "url.dll,OpenURL", publicKeyPath)
		cmd.Output()
		os.Remove(publicKeyPath)
	}

	// Run from PostUp, step 3.
	// Has only permission to get public key, can't run browser.
	if connected {
		getPublicKey(iface)
	}
}

func getPublicKey(iface string) {
	rxpPrivateKey := regexp.MustCompile("PrivateKey\\s*=\\s*(.*)")
	cmd := exec.Command("wg", "showconf", iface)
	out, _ := cmd.Output()
	privateKey := rxpPrivateKey.FindStringSubmatch(string(out))
	if len(privateKey) == 2 {
		pubkey, err := wgtypes.ParseKey(privateKey[1])
		if err != nil {
			logError("parse_privatekey", fmt.Sprintf("%s [%s]", err.Error(), privateKey[1]))
			return
		}

		urlData := fmt.Sprintf(
			"[InternetShortcut]\r\nURL=%s/?key=%s\r\n",
			DOMAIN,
			url.QueryEscape(pubkey.PublicKey().String()),
		)
		os.WriteFile(publicKeyPath, []byte(urlData), 0644)
		logError("publickey", pubkey.PublicKey().String())
	} else {
		logError("get_publickey", string(out))
	}
}