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@nirohfeld
Created March 10, 2024 17:39
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package main
import (
"flag"
"fmt"
"net"
"os"
"strings"
"sync"
"time"
"github.com/cheggaaa/pb/v3"
)
func performLookup(ip net.IP, results chan<- string, bar *pb.ProgressBar, retryCount int) {
var err error
var names []string
for i := 0; i < retryCount; i++ {
names, err = net.LookupAddr(ip.String())
if err == nil {
break
}
// Reduced sleep for retry to make it faster
time.Sleep(10 * time.Millisecond) // Shorter delay between retries
}
if err == nil && len(names) > 0 {
fmt.Println(ip, names[0])
results <- fmt.Sprintf("%s -> %s", ip, names[0])
}
bar.Increment()
}
func main() {
var inputFlag string
flag.StringVar(&inputFlag, "subnet", "", "Input to scan, CIDR notation (e.g., 10.5.0.0/24) or wildcard (e.g., 10.5.0.*)")
flag.Parse()
if inputFlag == "" {
fmt.Println("Usage: ./dnscan -subnet <CIDR or Wildcard>")
os.Exit(1)
}
ips, err := parseInput(inputFlag)
if err != nil {
fmt.Printf("Error processing subnet: %v\n", err)
os.Exit(1)
}
results := make(chan string)
bar := pb.StartNew(len(ips))
retryCount := 2
var wg sync.WaitGroup
rateLimit := time.Tick(1 * time.Millisecond)
for _, ip := range ips {
wg.Add(1)
<-rateLimit
go func(ip net.IP) {
defer wg.Done()
performLookup(ip, results, bar, retryCount)
}(ip)
}
go func() {
wg.Wait()
close(results)
bar.Finish()
}()
for r := range results {
fmt.Println(r)
}
}
func parseInput(input string) ([]net.IP, error) {
if strings.Contains(input, "*") {
// Convert wildcard to CIDR
cidrs, err := wildcardToCIDRs(input)
if err != nil {
return nil, err
}
var ips []net.IP
for _, cidr := range cidrs {
_, ipnet, _ := net.ParseCIDR(cidr)
ips = append(ips, generateIPsFromCIDR(ipnet)...)
}
return ips, nil
} else {
_, ipnet, err := net.ParseCIDR(input)
if err != nil {
return nil, fmt.Errorf("invalid input: %v", err)
}
return generateIPsFromCIDR(ipnet), nil
}
}
func wildcardToCIDRs(wildcard string) ([]string, error) {
parts := strings.Split(wildcard, ".")
if len(parts) != 4 {
return nil, fmt.Errorf("invalid wildcard format")
}
cidr := ""
for i, part := range parts {
if part == "*" {
parts[i] = "0"
}
cidr += parts[i]
if i < 3 {
cidr += "."
}
}
wildcardCount := strings.Count(wildcard, "*")
if wildcardCount < 1 || wildcardCount > 4 {
return nil, fmt.Errorf("invalid wildcard usage")
}
// Calculate CIDR block size based on wildcard count
cidrBlockSize := 32 - (wildcardCount * 8)
cidr += fmt.Sprintf("/%d", cidrBlockSize)
return []string{cidr}, nil
}
func generateIPsFromCIDR(ipnet *net.IPNet) []net.IP {
var ips []net.IP
for ip := ipnet.IP.Mask(ipnet.Mask); ipnet.Contains(ip); incrementIP(ip) {
ips = append(ips, net.ParseIP(ip.String()))
}
return ips
}
func incrementIP(ip net.IP) {
for j := len(ip) - 1; j >= 0; j-- {
ip[j]++
if ip[j] > 0 {
break
}
}
}
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