A fast and multi-purpose DNS toolkit designed for running DNS queries

Features • Installation • Usage • Running `dnsx` • Wildcard • Notes • Join Discord

dnsx is a fast and multi-purpose DNS toolkit designed for running various probes through the retryabledns library. It supports multiple DNS queries, user supplied resolvers, DNS wildcard filtering like shuffledns etc.

Features

• Simple and Handy utility to query DNS records.
• A, AAAA, CNAME, PTR, NS, MX, TXT, SRV, SOA query support
• DNS Resolution / Brute-force support
• Custom resolver input support
• Multiple resolver format (TCP/UDP/DOH/DOT) support
• stdin and stdout support
• Automatic wildcard handling support

Installation Instructions

dnsx requires go1.19 to install successfully. Run the following command to install the latest version:

go install -v github.com/khulnasoft-lab/dnsx/cmd/dnsx@latest

Usage

dnsx -h

This will display help for the tool. Here are all the switches it supports.

INPUT:
   -l, -list string      list of sub(domains)/hosts to resolve (file or stdin)
   -d, -domain string    list of domain to bruteforce (file or comma separated or stdin)
   -w, -wordlist string  list of words to bruteforce (file or comma separated or stdin)

QUERY:
   -a      query A record (default)
   -aaaa   query AAAA record
   -cname  query CNAME record
   -ns     query NS record
   -txt    query TXT record
   -srv    query SRV record
   -ptr    query PTR record
   -mx     query MX record
   -soa    query SOA record
   -axfr   query AXFR
   -caa    query CAA record
   -any    query ANY record

FILTER:
   -re, -resp          display dns response
   -ro, -resp-only     display dns response only
   -rc, -rcode string  filter result by dns status code (eg. -rcode noerror,servfail,refused)

PROBE:
   -cdn  display cdn name
   -asn  display host asn information

RATE-LIMIT:
   -t, -threads int      number of concurrent threads to use (default 100)
   -rl, -rate-limit int  number of dns request/second to make (disabled as default) (default -1)

UPDATE:
   -up, -update                 update dnsx to latest version
   -duc, -disable-update-check  disable automatic dnsx update check

OUTPUT:
   -o, -output string  file to write output
   -j, -json           write output in JSONL(ines) format
   -omit-raw, -or      omit raw dns response from jsonl output

DEBUG:
   -hc, -health-check  run diagnostic check up
   -silent             display only results in the output
   -v, -verbose        display verbose output
   -raw, -debug        display raw dns response
   -stats              display stats of the running scan
   -version            display version of dnsx

OPTIMIZATION:
   -retry int                number of dns attempts to make (must be at least 1) (default 2)
   -hf, -hostsfile           use system host file
   -trace                    perform dns tracing
   -trace-max-recursion int  Max recursion for dns trace (default 32767)
   -resume                   resume existing scan
   -stream                   stream mode (wordlist, wildcard, stats and stop/resume will be disabled)

CONFIGURATIONS:
   -r, -resolver string          list of resolvers to use (file or comma separated)
   -wt, -wildcard-threshold int  wildcard filter threshold (default 5)
   -wd, -wildcard-domain string  domain name for wildcard filtering (other flags will be ignored)

Running dnsx

DNS Resolving

Filter active hostnames from the list of passive subdomains, obtained from various sources:

subfinder -silent -d hackerone.com | dnsx -silent

a.ns.hackerone.com
www.hackerone.com
api.hackerone.com
docs.hackerone.com
mta-sts.managed.hackerone.com
mta-sts.hackerone.com
resources.hackerone.com
b.ns.hackerone.com
mta-sts.forwarding.hackerone.com
events.hackerone.com
support.hackerone.com

Print A records for the given list of subdomains:

subfinder -silent -d hackerone.com | dnsx -silent -a -resp

www.hackerone.com [104.16.100.52]
www.hackerone.com [104.16.99.52]
hackerone.com [104.16.99.52]
hackerone.com [104.16.100.52]
api.hackerone.com [104.16.99.52]
api.hackerone.com [104.16.100.52]
mta-sts.forwarding.hackerone.com [185.199.108.153]
mta-sts.forwarding.hackerone.com [185.199.109.153]
mta-sts.forwarding.hackerone.com [185.199.110.153]
mta-sts.forwarding.hackerone.com [185.199.111.153]
a.ns.hackerone.com [162.159.0.31]
resources.hackerone.com [52.60.160.16]
resources.hackerone.com [3.98.63.202]
resources.hackerone.com [52.60.165.183]
resources.hackerone.com [read.uberflip.com]
mta-sts.hackerone.com [185.199.110.153]
mta-sts.hackerone.com [185.199.111.153]
mta-sts.hackerone.com [185.199.109.153]
mta-sts.hackerone.com [185.199.108.153]
gslink.hackerone.com [13.35.210.17]
gslink.hackerone.com [13.35.210.38]
gslink.hackerone.com [13.35.210.83]
gslink.hackerone.com [13.35.210.19]
b.ns.hackerone.com [162.159.1.31]
docs.hackerone.com [185.199.109.153]
docs.hackerone.com [185.199.110.153]
docs.hackerone.com [185.199.111.153]
docs.hackerone.com [185.199.108.153]
support.hackerone.com [104.16.51.111]
support.hackerone.com [104.16.53.111]
mta-sts.managed.hackerone.com [185.199.108.153]
mta-sts.managed.hackerone.com [185.199.109.153]
mta-sts.managed.hackerone.com [185.199.110.153]
mta-sts.managed.hackerone.com [185.199.111.153]

Extract A records for the given list of subdomains:

subfinder -silent -d hackerone.com | dnsx -silent -a -resp-only

104.16.99.52
104.16.100.52
162.159.1.31
104.16.99.52
104.16.100.52
185.199.110.153
185.199.111.153
185.199.108.153
185.199.109.153
104.16.99.52
104.16.100.52
104.16.51.111
104.16.53.111
185.199.108.153
185.199.111.153
185.199.110.153
185.199.111.153

Extract CNAME records for the given list of subdomains:

subfinder -silent -d hackerone.com | dnsx -silent -cname -resp

support.hackerone.com [hackerone.zendesk.com]
resources.hackerone.com [read.uberflip.com]
mta-sts.hackerone.com [hacker0x01.github.io]
mta-sts.forwarding.hackerone.com [hacker0x01.github.io]
events.hackerone.com [whitelabel.bigmarker.com]

Extract ASN records for the given list of subdomains:

subfinder -silent -d hackerone.com | dnsx -silent  -asn

b.ns.hackerone.com [AS13335, CLOUDFLARENET, US]
a.ns.hackerone.com [AS13335, CLOUDFLARENET, US]
hackerone.com [AS13335, CLOUDFLARENET, US]
www.hackerone.com [AS13335, CLOUDFLARENET, US]
api.hackerone.com [AS13335, CLOUDFLARENET, US]
support.hackerone.com [AS13335, CLOUDFLARENET, US]

Probe using dns status code on given list of (sub)domains:

subfinder -silent -d hackerone.com | dnsx -silent -rcode noerror,servfail,refused

ns.hackerone.com [NOERROR]
a.ns.hackerone.com [NOERROR]
b.ns.hackerone.com [NOERROR]
support.hackerone.com [NOERROR]
resources.hackerone.com [NOERROR]
mta-sts.hackerone.com [NOERROR]
www.hackerone.com [NOERROR]
mta-sts.forwarding.hackerone.com [NOERROR]
docs.hackerone.com [NOERROR]

Extract subdomains from given network range using PTR query:

echo 173.0.84.0/24 | dnsx -silent -resp-only -ptr

cors.api.paypal.com
trinityadminauth.paypal.com
cld-edge-origin-api.paypal.com
appmanagement.paypal.com
svcs.paypal.com
trinitypie-serv.paypal.com
ppn.paypal.com
pointofsale-new.paypal.com
pointofsale.paypal.com
slc-a-origin-pointofsale.paypal.com
fpdbs.paypal.com

Extract subdomains from given ASN using PTR query:

echo AS17012 | dnsx -silent -resp-only -ptr 

apiagw-a.paypal.com
notify.paypal.com
adnormserv-slc-a.paypal.com
a.sandbox.paypal.com
apps2.paypal-labs.com
pilot-payflowpro.paypal.com
www.paypallabs.com
paypal-portal.com
micropayments.paypal-labs.com
minicart.paypal-labs.com

DNS Bruteforce

Bruteforce subdomains for given domain or list of domains using d and w flag:

dnsx -silent -d facebook.com -w dns_worldlist.txt

blog.facebook.com
booking.facebook.com
api.facebook.com
analytics.facebook.com
beta.facebook.com
apollo.facebook.com
ads.facebook.com
box.facebook.com
alpha.facebook.com
apps.facebook.com
connect.facebook.com
c.facebook.com
careers.facebook.com
code.facebook.com

Bruteforce targeted subdomain using single or multiple keyword input, as d or w flag supports file or comma separated keyword inputs:

dnsx -silent -d domains.txt -w jira,grafana,jenkins

grafana.1688.com
grafana.8x8.vc
grafana.airmap.com
grafana.aerius.nl
jenkins.1688.com
jenkins.airbnb.app
jenkins.airmap.com
jenkins.ahn.nl
jenkins.achmea.nl
jira.amocrm.com
jira.amexgbt.com
jira.amitree.com
jira.arrival.com
jira.atlassian.net
jira.atlassian.com

Values are accepted from stdin for all the input types (-list, -domain, -wordlist). The -list flag defaults to stdin, but the same can be achieved for other input types by adding a - (dash) as parameter:

cat domains.txt | dnsx -silent -w jira,grafana,jenkins -d -

grafana.1688.com
grafana.8x8.vc
grafana.airmap.com
grafana.aerius.nl
jenkins.1688.com
jenkins.airbnb.app
jenkins.airmap.com
jenkins.ahn.nl
jenkins.achmea.nl
jira.amocrm.com
jira.amexgbt.com
jira.amitree.com
jira.arrival.com
jira.atlassian.net
jira.atlassian.com

DNS Bruteforce with Placeholder based wordlist

$ cat tld.txt

com
by
de
be
al
bi
cg
dj
bs

dnsx -d google.FUZZ -w tld.txt -resp

      _             __  __
   __| | _ __   ___ \ \/ /
  / _' || '_ \ / __| \  / 
 | (_| || | | |\__ \ /  \ 
  \__,_||_| |_||___//_/\_\ v1.1.2

      khulnasoft.com

google.de [142.250.194.99] 
google.com [142.250.76.206] 
google.be [172.217.27.163] 
google.bs [142.251.42.35] 
google.bi [216.58.196.67] 
google.al [216.58.196.68] 
google.by [142.250.195.4] 
google.cg [142.250.183.131] 
google.dj [142.250.192.3] 

Wildcard filtering

A special feature of dnsx is its ability to handle multi-level DNS based wildcards, and do it so with a very reduced number of DNS requests. Sometimes all the subdomains will resolve, which leads to lots of garbage in the output. The way dnsx handles this is by keeping track of how many subdomains point to an IP and if the count of the subdomains increase beyond a certain threshold, it will check for wildcards on all the levels of the hosts for that IP iteratively.

dnsx -l subdomain_list.txt -wd airbnb.com -o output.txt

Dnsx as a library

It's possible to use the library directly in your golang programs. The following code snippets is an example of use in golang programs. Please refer to here for detailed package configuration and usage.

package main

import (
	"fmt"

	"github.com/khulnasoft-lab/dnsx/libs/dnsx"
)

func main() {
	// Create DNS Resolver with default options
	dnsClient, err := dnsx.New(dnsx.DefaultOptions)
	if err != nil {
		fmt.Printf("err: %v\n", err)
		return
	}

	// DNS A question and returns corresponding IPs
	result, err := dnsClient.Lookup("hackerone.com")
	if err != nil {
		fmt.Printf("err: %v\n", err)
		return
	}
	for idx, msg := range result {
		fmt.Printf("%d: %s\n", idx+1, msg)
	}

	// Query
	rawResp, err := dnsClient.QueryOne("hackerone.com")
	if err != nil {
		fmt.Printf("err: %v\n", err)
		return
	}
	fmt.Printf("rawResp: %v\n", rawResp)

	jsonStr, err := rawResp.JSON()
	if err != nil {
		fmt.Printf("err: %v\n", err)
		return
	}
	fmt.Println(jsonStr)

	return
}

📋 Notes

• As default, dnsx checks for A record.
• As default dnsx uses Google, Cloudflare, Quad9 resolver.
• Custom resolver list can be loaded using the r flag.
• Domain name (wd) input is mandatory for wildcard elimination.
• DNS record flag can not be used when using wildcard filtering.
• DNS resolution (l) and DNS brute-forcing (w) can't be used together.
• VPN operators tend to filter high DNS/UDP traffic, therefore the tool might experience packets loss (eg. Mullvad VPN)

dnsx is made with 🖤 by the khulnasoft-lab team.