53 - Pentesting DNS

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Basic Information

The Domain Name System (DNS) serves as the internet's directory, allowing users to access websites through easy-to-remember domain names like google.com or facebook.com, instead of the numeric Internet Protocol (IP) addresses. By translating domain names into IP addresses, the DNS ensures web browsers can quickly load internet resources, simplifying how we navigate the online world.

Default port: 53

PORT     STATE SERVICE  REASON
53/tcp   open  domain  Microsoft DNS 6.1.7601 (1DB15D39) (Windows Server 2008 R2 SP1)
5353/udp open  zeroconf udp-response
53/udp   open  domain  Microsoft DNS 6.1.7601 (1DB15D39) (Windows Server 2008 R2 SP1)

Different DNS Servers

  • DNS Root Servers: These are at the top of the DNS hierarchy, managing the top-level domains and stepping in only if lower-level servers do not respond. The Internet Corporation for Assigned Names and Numbers (ICANN) oversees their operation, with a global count of 13.

  • Authoritative Nameservers: These servers have the final say for queries in their designated zones, offering definitive answers. If they can't provide a response, the query is escalated to the root servers.

  • Non-authoritative Nameservers: Lacking ownership over DNS zones, these servers gather domain information through queries to other servers.

  • Caching DNS Server: This type of server memorizes previous query answers for a set time to speed up response times for future requests, with the cache duration dictated by the authoritative server.

  • Forwarding Server: Serving a straightforward role, forwarding servers simply relay queries to another server.

  • Resolver: Integrated within computers or routers, resolvers execute name resolution locally and are not considered authoritative.

Enumeration

There aren't banners in DNS but you can gran the macgic query for version.bind. CHAOS TXT which will work on most BIND nameservers. You can perform this query using dig:

dig version.bind CHAOS TXT @DNS

Moreover, the tool fpdns can also fingerprint the server.

It's also possible to grab the banner also with a nmap script:

--script dns-nsid

Any record

The record ANY will ask the DNS server to return all the available entries that it is willing to disclose.

dig any victim.com @<DNS_IP>

Zone Transfer

This procedure is abbreviated Asynchronous Full Transfer Zone (AXFR).

dig axfr @<DNS_IP> #Try zone transfer without domain
dig axfr @<DNS_IP> <DOMAIN> #Try zone transfer guessing the domain
fierce --domain <DOMAIN> --dns-servers <DNS_IP> #Will try toperform a zone transfer against every authoritative name server and if this doesn'twork, will launch a dictionary attack

More info

dig ANY @<DNS_IP> <DOMAIN>     #Any information
dig A @<DNS_IP> <DOMAIN>       #Regular DNS request
dig AAAA @<DNS_IP> <DOMAIN>    #IPv6 DNS request
dig TXT @<DNS_IP> <DOMAIN>     #Information
dig MX @<DNS_IP> <DOMAIN>      #Emails related
dig NS @<DNS_IP> <DOMAIN>      #DNS that resolves that name
dig -x 192.168.0.2 @<DNS_IP>   #Reverse lookup
dig -x 2a00:1450:400c:c06::93 @<DNS_IP> #reverse IPv6 lookup

#Use [-p PORT]  or  -6 (to use ivp6 address of dns)

Automation

for sub in $(cat <WORDLIST>);do dig $sub.<DOMAIN> @<DNS_IP> | grep -v ';\|SOA' | sed -r '/^\s*$/d' | grep $sub | tee -a subdomains.txt;done

dnsenum --dnsserver <DNS_IP> --enum -p 0 -s 0 -o subdomains.txt -f <WORDLIST> <DOMAIN>

Using nslookup

nslookup
> SERVER <IP_DNS> #Select dns server
> 127.0.0.1 #Reverse lookup of 127.0.0.1, maybe...
> <IP_MACHINE> #Reverse lookup of a machine, maybe...

Useful metasploit modules

auxiliary/gather/enum_dns #Perform enumeration actions

Useful nmap scripts

#Perform enumeration actions
nmap -n --script "(default and *dns*) or fcrdns or dns-srv-enum or dns-random-txid or dns-random-srcport" <IP>

DNS - Reverse BF

dnsrecon -r 127.0.0.0/24 -n <IP_DNS>  #DNS reverse of all of the addresses
dnsrecon -r 127.0.1.0/24 -n <IP_DNS>  #DNS reverse of all of the addresses
dnsrecon -r <IP_DNS>/24 -n <IP_DNS>   #DNS reverse of all of the addresses
dnsrecon -d active.htb -a -n <IP_DNS> #Zone transfer

If you are able to find subdomains resolving to internal IP-addresses, you should try to perform a reverse dns BF to the NSs of the domain asking for that IP range.

Another tool to do so: https://github.com/amine7536/reverse-scan

You can query reverse IP ranges to https://bgp.he.net/net/205.166.76.0/24#_dns (this tool is also helpful with BGP).

DNS - Subdomains BF

dnsenum --dnsserver <IP_DNS> --enum -p 0 -s 0 -o subdomains.txt -f subdomains-1000.txt <DOMAIN>
dnsrecon -D subdomains-1000.txt -d <DOMAIN> -n <IP_DNS>
dnscan -d <domain> -r -w subdomains-1000.txt #Bruteforce subdomains in recursive way, https://github.com/rbsec/dnscan

Active Directory servers

dig -t _gc._tcp.lab.domain.com
dig -t _ldap._tcp.lab.domain.com
dig -t _kerberos._tcp.lab.domain.com
dig -t _kpasswd._tcp.lab.domain.com

nslookup -type=srv _kerberos._tcp.<CLIENT_DOMAIN>
nslookup -type=srv _kerberos._tcp.domain.com

nmap --script dns-srv-enum --script-args "dns-srv-enum.domain='domain.com'"

DNSSec

 #Query paypal subdomains to ns3.isc-sns.info
 nmap -sSU -p53 --script dns-nsec-enum --script-args dns-nsec-enum.domains=paypal.com ns3.isc-sns.info

IPv6

Brute force using "AAAA" requests to gather IPv6 of the subdomains.

dnsdict6 -s -t <domain>

Bruteforce reverse DNS in using IPv6 addresses

dnsrevenum6 pri.authdns.ripe.net 2001:67c:2e8::/48 #Will use the dns pri.authdns.ripe.net

DNS Recursion DDoS

If DNS recursion is enabled, an attacker could spoof the origin on the UDP packet in order to make the DNS send the response to the victim server. An attacker could abuse ANY or DNSSEC record types as they use to have the bigger responses. The way to check if a DNS supports recursion is to query a domain name and check if the flag "ra" (recursion available) is in the response:

dig google.com A @<IP>

Non available:

Available:

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Mail to nonexistent account

Through the examination of a nondelivery notification (NDN) triggered by an email sent to an invalid address within a target domain, valuable internal network details are often disclosed.

The provided nondelivery report includes information such as:

  • The generating server was identified as server.example.com.

  • A failure notice for user@example.com with the error code #550 5.1.1 RESOLVER.ADR.RecipNotFound; not found was returned.

  • Internal IP addresses and hostnames were disclosed in the original message headers.

The original message headers were modified for anonymity and now present randomized data:

Generating server: server.example.com

user@example.com
#550 5.1.1 RESOLVER.ADR.RecipNotFound; not found ##

Original message headers:

Received: from MAILSERVER01.domain.example.com (192.168.1.1) by
mailserver02.domain.example.com (192.168.2.2) with Microsoft SMTP Server (TLS)
id 14.3.174.1; Mon, 25 May 2015 14:52:22 -0700
Received: from filter.example.com (203.0.113.1) by
MAILSERVER01.domain.example.com (192.168.1.1) with Microsoft SMTP Server (TLS)
id 14.3.174.1; Mon, 25 May 2015 14:51:22 -0700
X-ASG-Debug-ID: 1432576343-0614671716190e0d0001-zOQ9WJ
Received: from gateway.domainhost.com (gateway.domainhost.com [198.51.100.37]) by
filter.example.com with ESMTP id xVNPkwaqGgdyH5Ag for user@example.com; Mon,
25 May 2015 14:52:13 -0700 (PDT)
X-Envelope-From: sender@anotherdomain.org
X-Apparent-Source-IP: 198.51.100.37

Config files

host.conf
/etc/resolv.conf
/etc/bind/named.conf
/etc/bind/named.conf.local
/etc/bind/named.conf.options
/etc/bind/named.conf.log
/etc/bind/*

Dangerous settings when configuring a Bind server:

Option

Description

allow-query

Defines which hosts are allowed to send requests to the DNS server.

allow-recursion

Defines which hosts are allowed to send recursive requests to the DNS server.

allow-transfer

Defines which hosts are allowed to receive zone transfers from the DNS server.

zone-statistics

Collects statistical data of zones.

References

HackTricks Automatic Commands

Protocol_Name: DNS    #Protocol Abbreviation if there is one.
Port_Number:  53     #Comma separated if there is more than one.
Protocol_Description: Domain Name Service        #Protocol Abbreviation Spelled out

Entry_1:
  Name: Notes
  Description: Notes for DNS
  Note: |
    #These are the commands I run every time I see an open DNS port

    dnsrecon -r 127.0.0.0/24 -n {IP} -d {Domain_Name}
    dnsrecon -r 127.0.1.0/24 -n {IP} -d {Domain_Name}
    dnsrecon -r {Network}{CIDR} -n {IP} -d {Domain_Name}
    dig axfr @{IP}
    dig axfr {Domain_Name} @{IP}
    nslookup
        SERVER {IP}
        127.0.0.1
        {IP}
        Domain_Name
        exit

    https://book.hacktricks.xyz/pentesting/pentesting-dns

Entry_2:
  Name: Banner Grab
  Description: Grab DNS Banner
  Command: dig version.bind CHAOS TXT @DNS

Entry_3:
  Name: Nmap Vuln Scan
  Description: Scan for Vulnerabilities with Nmap
  Command: nmap -n --script "(default and *dns*) or fcrdns or dns-srv-enum or dns-random-txid or dns-random-srcport" {IP}

Entry_4:
  Name: Zone Transfer
  Description: Three attempts at forcing a zone transfer
  Command: dig axfr @{IP} && dix axfr @{IP} {Domain_Name} && fierce --dns-servers {IP} --domain {Domain_Name}


Entry_5:
  Name: Active Directory
  Description: Eunuerate a DC via DNS
  Command: dig -t _gc._{Domain_Name} && dig -t _ldap._{Domain_Name} && dig -t _kerberos._{Domain_Name} && dig -t _kpasswd._{Domain_Name} && nmap --script dns-srv-enum --script-args "dns-srv-enum.domain={Domain_Name}"
  
Entry_6:
  Name: consolesless mfs enumeration
  Description: DNS enumeration without the need to run msfconsole
  Note: sourced from https://github.com/carlospolop/legion
  Command: msfconsole -q -x 'use auxiliary/scanner/dns/dns_amp; set RHOSTS {IP}; set RPORT 53; run; exit' && msfconsole -q -x 'use auxiliary/gather/enum_dns; set RHOSTS {IP}; set RPORT 53; run; exit'

Get a hacker's perspective on your web apps, network, and cloud

Find and report critical, exploitable vulnerabilities with real business impact. Use our 20+ custom tools to map the attack surface, find security issues that let you escalate privileges, and use automated exploits to collect essential evidence, turning your hard work into persuasive reports.

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