Go VPN Detector

main.go

package main

import (
	"bufio"
	"io"
	"log"
	"net"
	"net/http"
	"os"
	"strings"
)

type CIDRRecord struct {
	Network *net.IPNet
}

func loadCIDRDatabase(filePath string) ([]CIDRRecord, error) {
	file, err := os.Open(filePath)
	if err != nil {
		return nil, err
	}
	defer file.Close()

	var records []CIDRRecord
	scanner := bufio.NewScanner(file)
	for scanner.Scan() {
		line := strings.TrimSpace(scanner.Text())
		if line == "" || strings.HasPrefix(line, "#") {
			continue // Skip empty lines or comments
		}
		_, network, err := net.ParseCIDR(line)
		if err != nil {
			log.Printf("Failed to parse CIDR: %v", line)
			continue
		}
		records = append(records, CIDRRecord{Network: network})
	}

	if err := scanner.Err(); err != nil {
		return nil, err
	}
	return records, nil
}

func detectVPN(ip string, records []CIDRRecord) bool {
	parsedIP := net.ParseIP(ip)
	if parsedIP == nil {
		log.Printf("Invalid IP address: %s", ip)
		return false
	}

	for _, record := range records {
		if record.Network.Contains(parsedIP) {
			return true
		}
	}
	return false
}

func getPublicIP() (string, error) {
	resp, err := http.Get("https://api.ipify.org?format=text")
	if err != nil {
		return "", err
	}
	defer resp.Body.Close()

	ip, err := io.ReadAll(resp.Body)
	if err != nil {
		return "", err
	}

	return string(ip), nil
}

func main() {
	databasePath := "./ipv4.txt" // Download file from https://github.com/X4BNet/lists_vpn/blob/main/ipv4.txt
	records, err := loadCIDRDatabase(databasePath)
	if err != nil {
		log.Fatalf("Failed to load database: %v", err)
	}

	publicIP, err := getPublicIP()
	if err != nil {
		log.Fatalf("Failed to detect public IP: %v", err)
	}

	log.Printf("Public IP Detected: %s", publicIP)

	if detectVPN(publicIP, records) {
		log.Println("The IP address is detected as VPN/Proxy.")
	} else {
		log.Println("No VPN detected for this IP.")
	}
}

Download list of VPN IP database from https://github.com/X4BNet/lists_vpn/blob/main/ipv4.txt