dnsBotCheck.go

package main

import (
	"bytes"
	"fmt"
	"net"
	"strings"
)

func main() {
	fmt.Println(verifyBot("157.55.39.84", "msn.com."))        // true
	fmt.Println(verifyBot("91.99.75.10", "google.com."))      // false
	fmt.Println(verifyBot("66.249.66.1", "googlebot.com."))   // true
	fmt.Println(verifyBot("66.249.64.118", "googlebot.com.")) // true
	fmt.Println(verifyBot("66.249.64.116", "googlebot.com.")) // true
	fmt.Println(verifyBot("66.249.92.71", "google.com."))     // true
	fmt.Println(verifyBot("66.249.64.118", "googlebot.com.")) // true
	fmt.Println(verifyBot("66.249.64.116", "googlebot.com.")) // true
	fmt.Println(verifyBot("66.249.83.221", "google.com."))    // true
	fmt.Println(verifyBot("66.249.93.223", "google.com."))    // true
	fmt.Println(verifyBot("66.249.81.116", "google.com."))    // true
	fmt.Println(verifyBot("66.249.92.75", "google.com."))     // true
	fmt.Println(verifyBot("157.55.39.25", "msn.com."))        // true
	fmt.Println(verifyBot("13.66.139.1", "msn.com."))         // true
	fmt.Println(verifyBot("207.46.13.179", "msn.com."))       // true
	fmt.Println(verifyBot("66.249.89.180", "google.com."))       // true
}

// verifyBot used verify IP address with a reverse and forward DNS lookup
func verifyBot(ip string, identifier string) bool {
	// reverse dns lookup
	rev, err := net.LookupAddr(ip)
	if err != nil {
		panic(err)
	}

	if strings.HasSuffix(rev[0], identifier) {
		// forward dns lookup
		frw, err := net.LookupIP(rev[0])
		if err != nil {
			panic(err)
		}
		// check forward dns result with the original bot address
		parsedIP := net.ParseIP(ip)
		for _, res := range frw {
			if bytes.Compare(res, parsedIP) == 0 {
				return true
			}
		}
	}
	return false
}