hacktricks/network-services-pentesting/pentesting-dns.md

# 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

### **Banner Grabbing**

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

```bash
dig version.bind CHAOS TXT @DNS
```

Moreover, the tool [`fpdns`](https://github.com/kirei/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**.

```bash
dig any victim.com @<DNS_IP>
```

### **Zone Transfer**

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

```bash
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

```bash
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

```bash
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

```bash
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

```bash
auxiliary/gather/enum_dns #Perform enumeration actions
```

### Useful nmap scripts

```bash
#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

```bash
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
```

{% hint style="info" %}
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.
{% endhint %}

Another tool to do so: [https://github.com/amine7536/reverse-scan](https://github.com/amine7536/reverse-scan)

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

### DNS - Subdomains BF

```bash
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

```bash
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

```bash
 #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.

```bash
dnsdict6 -s -t <domain>
```

Bruteforce reverse DNS in using IPv6 addresses

```bash
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:

```bash
dig google.com A @<IP>
```

**Non available**:

![](<../.gitbook/assets/image (123).png>)

**Available**:

![](<../.gitbook/assets/image (146).png>)

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### Mail to nonexistent account

**Sending an email to a non-existaent address** using the victims domain could trigger the victim to send a nondelivery notification (NDN) message whose **headers** could contain interesting information such as the **name of internal servers and IP addresses**.

## Post-Exploitation

* When checking the configuration of a Bind server check the configuration of the param **`allow-transfer`** as it indicates who can perform zone transfers and **`allow-recursion`** and **`allow-query`** as the indicate who can send recursive requests and requests to it.
* The following are the names of DNS related files that could be interesting to search inside machines:

```
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/*
```

## References

* [https://www.myrasecurity.com/en/knowledge-hub/dns/](https://www.myrasecurity.com/en/knowledge-hub/dns/)
* Book: **Network Security Assessment 3rd edition**

## 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' 
```

<figure><img src="../.gitbook/assets/pentest-tools.svg" alt=""><figcaption></figcaption></figure>

**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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<summary>Support HackTricks</summary>

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