Automatic Exploit Generation (AEG) and remote flag capture for exploitable CTF problems
This tool uses angr to concolically analyze binaries by hooking printf and looking for unconstrained paths. These program states are then weaponized for remote code execution through pwntools and a series of script tricks. Finally the payload is tested locally then submitted to a remote CTF server to recover the flag.
Zeratool now supports remote libc leaking with buffer overflows. When a puts or printf call is present, Zeratool will leak out remote GOT entries and submit them to an online libc searching database to find offsets without the need for a local copy of the library.
See remote libc leak in action!
Zeratool supports some basic ret2dlresolve chaining for 64bit binaries. See the example below on how to run it.
Zeratool now supports some smart rop chain generation. During a buffer overflow Zeratool will attempt to leak a libc address and compute the base address and build a execve(/bin/sh,NULL,NULL) chain or system(/bin/sh) chain.
Zeratool has been tested on Ubuntu 16.04 through 20.04. Please install radare2 first
pip install zeratool
Zeratool is a python script which accept a binary as an argument and optionally a linked libc library, and a CTF Server connection information
[chris:~/Zeratool] zerapwn.py -h
usage: zerapwn.py [-h] [-l LIBC] [-u URL] [-p PORT] [-v] [--force_shellcode] [--force_dlresolve] [--skip_check] [--no_win] [--format_only] [--overflow_only] file
positional arguments:
file File to analyze
optional arguments:
-h, --help show this help message and exit
-l LIBC, --libc LIBC libc to use
-u URL, --url URL Remote URL to pwn
-p PORT, --port PORT Remote port to pwn
-v, --verbose Verbose mode
--force_shellcode Set overflow pwn mode to point to shellcode
--force_dlresolve Set overflow pwn mode to use ret2dlresolve
--skip_check Skip first check and jump right to exploiting
--no_win Skip win function checking
--format_only Only run format strings check
--overflow_only Only run overflow check
Zeratool is designed around weaponizing buffer overflows and format string vulnerabilities and currently supports a couple types:
- Buffer Overflow
- Point program counter to win function
- Point program counter to shellcode
- Point program counter to rop chain
- Rop chains will attempt to leak a libc function
- Rop chains will then execve(/bin/sh) or system(/bin/sh)
- Can attempt a ret2dlresolve ropchain
- Can attempt to use puts/printf to leak remote libc
- Format String
- Point GOT entry to win function
- Point GOT entry to shellcode
Checkout the samples.sh file. The file contains several examples of Zeratool automatically solving exploitable CTF problems.
#!/bin/bash
# Buffer Overflows with win functions
zerapwn.py tests/bin/bof_win_32
zerapwn.py tests/bin/bof_win_64
# Buffer Overflows with ropping
zerapwn.py tests/bin/bof_nx_32
zerapwn.py tests/bin/bof_nx_64
# Buffer Overflow with ropping and libc leak
zerapwn.py tests/bin/bof_nx_64 -l tests/bin/libc.so.6_amd64
#Format string leak
zerapwn.py tests/bin/read_stack_32
zerapwn.py tests/bin/read_stack_64
#Format string point to win function
zerapwn.py challenges/medium_format
#Format string point to shellcode
#zerapwn.py challenges/hard_format #This one sometimes needs to be run twice
# Buffer overflow point to shellcode
# Turn off aslr
# echo 0 | sudo tee /proc/sys/kernel/randomize_va_space
zerapwn.py tests/bin/bof_32 --force_shellcode
zerapwn.py tests/bin/bof_64 --force_shellcode
# Remote libc leak
socat TCP4-LISTEN:7903,tcpwrap=script,reuseaddr,fork EXEC:./bof_nx_64
zerapwn.py tests/bin/bof_nx_64 -u localhost -p 7903 --skip_check --overflow_only
# Ret2dlresolve
zerapwn.py tests/bin/bof_dlresolve_64 --force_dlresolve --skip_check --overflow_only --no_win
Long Asciinema with Three Solves
Tox and Pytest are used to verify that Zeratool is working correctly.
tox .
Q. Why doesn't Zeratool work against my simple exploitable?
A. Zeratool is held together by scotch tape and dreams.