本文为看雪论坛优秀文章
看雪论坛作者ID：橘喵Cat
一
前言
实现压缩壳，必须对PE格式十分熟悉，其次，解压缩代码需要编写shellcode，也是十分麻烦的环节。有了两者的结合，我们才能写好一个真正的压缩壳。
二
设计思路
首先上一张图，让大家直观地感受到一个壳程序是如何运行起来的。
左边是壳PE，壳程序有一个PE头，节表1是空节，用来存放解压缩后的原程序PE，节表2此时存储的是压缩后的原PE。节表3则是壳代码节，壳PE运行起来后，首先就是进入入口点，运行节表3的代码，解压缩节表2，然后将结果覆盖PE头＋节表1的位置，修复完导入表、重定位表，jmp到原程序的入口点处即可。
原理不变，我这里加了点“料”，新增了节4和节5，存储了相关的信息，让压缩壳的脱壳过程变难，往后看就知道了。
三
壳代码实现
1.为了生成一个新的壳PE，我们一步步来，首先是PE头，俗话说靠山吃山，靠水吃水，这个PE头我就直接拿原程序的PE头来代替了，只不过需要改一些数据：
NumberOfSections --节表数量，要改为5AddressOfEntryPoint --入口点，要改为节表3里的代码入口SizeOfImage --PE在内存中的大小，要改为新的PE的内存大小pSecHdr --节表头，要拓展为5个节表void CPacker::GetNewPeHdr(){//拷贝原PE的PE头m_dwNewPeHdrSize = m_pNtHdr->OptionalHeader.SizeOfHeaders;m_pNewPeHdr = new BYTE[m_dwNewPeHdrSize];CopyMemory(m_pNewPeHdr, m_pDosHdr, m_dwNewPeHdrSize);//修改auto pDosHdr = (PIMAGE_DOS_HEADER)m_pNewPeHdr;auto pNtHdr = (PIMAGE_NT_HEADERS)(m_pNewPeHdr + pDosHdr->e_lfanew);auto pSecHdr = (PIMAGE_SECTION_HEADER)((LPBYTE)&pNtHdr->OptionalHeader + pNtHdr->FileHeader.SizeOfOptionalHeader);pNtHdr->FileHeader.NumberOfSections = 5;pNtHdr->OptionalHeader.AddressOfEntryPoint = m_newSecHdr[2].VirtualAddress;pNtHdr->OptionalHeader.SizeOfImage = m_newSecHdr[4].VirtualAddress + m_newSecHdr[4].Misc.VirtualSize;//清空DataDirectory目录ZeroMemory(pNtHdr->OptionalHeader.DataDirectory, sizeof(pNtHdr->OptionalHeader.DataDirectory));//修改新的节表头CopyMemory(pSecHdr, m_newSecHdr, sizeof(m_newSecHdr));}
2.新PE头里一些需要修改的数据，比如SizeOfImage，我们目前还没有，需要等我们构造出节表1、2、3、4、5之后，才知道。接下来，先构造节表1的表头，节表1是个空节，它的大小只要够存放原程序的节表即可，多给一点也没关系，我这里直接给了SizeOfImage。（由于是空节，所以这里并不需要考虑节表1的数据内容）
//空节strcpy((char*)m_newSecHdr[0].Name, ".cr42");m_newSecHdr[0].Misc.VirtualSize = m_pNtHdr->OptionalHeader.SizeOfImage;m_newSecHdr[0].VirtualAddress = m_pSecHdr[0].VirtualAddress;m_newSecHdr[0].SizeOfRawData = 0;m_newSecHdr[0].PointerToRawData = 0;m_newSecHdr[0].Characteristics =IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_WRITE | IMAGE_SCN_MEM_READ;
3.接着是节表2，这个节要存放原PE的压缩数据，先设计表头（使用了PointerToRelocations和PointerToLinenumbers这两个没啥用的字段，存放压缩大小信息，留着给后面shellcode用）。
//压缩数据节strcpy((char*)m_newSecHdr[1].Name, ".data");m_newSecHdr[1].Misc.VirtualSize = GetAlign(m_dwComSecSize, m_pNtHdr->OptionalHeader.SectionAlignment);m_newSecHdr[1].VirtualAddress = m_newSecHdr[0].VirtualAddress + m_newSecHdr[0].Misc.VirtualSize;m_newSecHdr[1].SizeOfRawData = m_dwComSecSize;m_newSecHdr[1].PointerToRawData = m_pNtHdr->OptionalHeader.SizeOfHeaders;m_newSecHdr[1].Characteristics = IMAGE_SCN_MEM_READ;m_newSecHdr[1].PointerToRelocations = m_dwComSize; //压缩后大小m_newSecHdr[1].PointerToLinenumbers = m_dwSrcPeSize;//压缩前大小
然后将PE压缩，压缩前我把节表、导入表、重定位表保存并清空，到时候由shellcode进行还原。
bool CPacker::GetCompressData(){COMPRESSOR_HANDLE hCompressor = NULL;BOOL Success = CreateCompressor(COMPRESS_ALGORITHM_XPRESS_HUFF,NULL,&hCompressor);m_pComData = new BYTE[m_dwSrcPeSize + 0x28];LPBYTE m_pSrcPeTmp = new BYTE[m_dwSrcPeSize];CopyMemory(m_pSrcPeTmp, m_pSrcPe, m_dwSrcPeSize);PIMAGE_DOS_HEADER m_pDosHdrTmp = (PIMAGE_DOS_HEADER)m_pSrcPeTmp;PIMAGE_NT_HEADERS m_pNtHdrTmp = (PIMAGE_NT_HEADERS)(m_pSrcPeTmp + m_pDosHdrTmp->e_lfanew);PIMAGE_SECTION_HEADER m_pSecHdrTmp = (PIMAGE_SECTION_HEADER)((LPBYTE)&m_pNtHdrTmp->OptionalHeader + m_pNtHdrTmp->FileHeader.SizeOfOptionalHeader);//1.在压缩前，把节表保存并清空nSecNum = m_pNtHdrTmp->FileHeader.NumberOfSections;CopyMemory(m_pSaveSecHdr, m_pSecHdrTmp, nSecNum * 40);ZeroMemory(m_pSecHdrTmp, nSecNum * 40);//2.把导入表保存并清空m_pImportAddr = m_pNtHdrTmp->OptionalHeader.DataDirectory[1].VirtualAddress;nImpSize = m_pNtHdrTmp->OptionalHeader.DataDirectory[1].Size;ZeroMemory(&(m_pNtHdrTmp->OptionalHeader.DataDirectory[1]), 8);//3.把重定位表保存并清空m_pRelocAddr = m_pNtHdrTmp->OptionalHeader.DataDirectory[5].VirtualAddress;nRelocSize = m_pNtHdrTmp->OptionalHeader.DataDirectory[5].Size;ZeroMemory(&(m_pNtHdrTmp->OptionalHeader.DataDirectory[5]), 8);Success = Compress(hCompressor,m_pSrcPeTmp,m_dwSrcPeSize,m_pComData,m_dwSrcPeSize + 0x28,&m_dwComSize);return true;}
4.接着是节表3，该节表存放的是解压缩PE、还原导入表、重定位表，运行原程序的至关重要的shellcode，先设计表头。
//代码节strcpy((char*)m_newSecHdr[2].Name, ".text");m_newSecHdr[2].Misc.VirtualSize = GetAlign(m_dwCodeSecSize, m_pNtHdr->OptionalHeader.SectionAlignment);m_newSecHdr[2].VirtualAddress = m_newSecHdr[1].VirtualAddress + m_newSecHdr[1].Misc.VirtualSize;m_newSecHdr[2].SizeOfRawData = m_dwCodeSecSize;m_newSecHdr[2].PointerToRawData = m_newSecHdr[1].PointerToRawData + m_newSecHdr[1].SizeOfRawData;m_newSecHdr[2].Characteristics = IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_WRITE | IMAGE_SCN_MEM_READ;
至于节表3的数据内容，也就是shellcode，等我把节表、PE设计完，我再说。
5.接着是节表4，节表4是我额外增加的一个，用来存储步骤3中保存的原节表表头、原导入表、原重定位表，首先设计节表4表头。
//存放原节表、导入表、重定位表的节strcpy((char*)m_newSecHdr[3].Name, ".info");m_newSecHdr[3].Misc.VirtualSize = GetAlign(m_dwTableSecSize, m_pNtHdr->OptionalHeader.SectionAlignment);m_newSecHdr[3].VirtualAddress = m_newSecHdr[2].VirtualAddress + m_newSecHdr[2].Misc.VirtualSize;m_newSecHdr[3].SizeOfRawData = m_dwTableSecSize;m_newSecHdr[3].PointerToRawData = m_newSecHdr[2].PointerToRawData + m_newSecHdr[2].SizeOfRawData;m_newSecHdr[3].Characteristics = IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_WRITE | IMAGE_SCN_MEM_READ;
然后把刚才保存的原节表表头、原导入表、原重定位表信息，按顺序写入到缓冲区里。
bool CPacker::GetTable(){m_dwTableSize = nSecNum * 40 + 4 + 8 + 8;m_pTable = new BYTE[m_dwTableSize];RtlCopyMemory(m_pTable, &nSecNum, 4);RtlCopyMemory(m_pTable + 4, m_pSaveSecHdr, nSecNum * 40);RtlCopyMemory(m_pTable + 4 + nSecNum * 40, &m_pImportAddr, 4);RtlCopyMemory(m_pTable + 4 + nSecNum * 40 + 4, &nImpSize, 4);RtlCopyMemory(m_pTable + 4 + nSecNum * 40 + 4 + 4, &m_pRelocAddr, 4);RtlCopyMemory(m_pTable + 4 + nSecNum * 40 + 4 + 4 + 4, &nRelocSize, 4);return true;}
6.还剩最后一个节表5，是一个空节，壳代码还原原PE时，要还原导入表，于是这个节的作用就体现出来了，shellcode在这里玩了一波偷梁换柱，直接毙掉了x64dbg的脱壳后导入表自动修复功能，等会介绍shellcode的时候你们就知道了。设计节表5的表头：
//绕过x64搜索导入表的节(空节)strcpy((char*)m_newSecHdr[4].Name, ".imp");m_newSecHdr[4].Misc.VirtualSize = GetAlign(0x10000, m_pNtHdr->OptionalHeader.SectionAlignment);m_newSecHdr[4].VirtualAddress = m_newSecHdr[3].VirtualAddress + m_newSecHdr[3].Misc.VirtualSize;m_newSecHdr[4].SizeOfRawData = 0;m_newSecHdr[4].PointerToRawData = m_newSecHdr[3].PointerToRawData + m_newSecHdr[2].SizeOfRawData;m_newSecHdr[4].Characteristics = IMAGE_SCN_MEM_EXECUTE | IMAGE_SCN_MEM_WRITE | IMAGE_SCN_MEM_READ;
至此，新的壳PE结构我们就设计好了，然后将新PE头、节表234写入到新文件（节表1、5是空节，不用写入），就大功告成，加壳完毕！
bool CPacker::WriteNewPe(CString strNewPe){//创建文件HANDLE hFile = CreateFile(strNewPe,GENERIC_WRITE,0,NULL,CREATE_ALWAYS,FILE_ATTRIBUTE_NORMAL,NULL);//写入PE头DWORD dwBytesWrited = 0;WriteFile(hFile, m_pNewPeHdr, m_dwNewPeHdrSize, &dwBytesWrited, NULL);//写入数据节WriteFile(hFile, m_pComSec, m_dwComSecSize, &dwBytesWrited, NULL);//写入代码节WriteFile(hFile, m_pCodeSec, m_dwCodeSecSize, &dwBytesWrited, NULL);//写入存放表数据节WriteFile(hFile, m_pTableSec, m_dwTableSecSize, &dwBytesWrited, NULL);CloseHandle(hFile);return true;}
四
shellcode代码实现
由于壳PE可能是随机基址，所以执行shellcode时，一定要确保它的代码跟地址无关。我的shellcode是在VS上编译的，为了保证VS不会生成多余的代码，要修改以下几个设置：
1.使用Release版（Debug会加地址有关代码）2.不使用main函数，自己定义一个，放在链接器->高级->入口点（main不是程序真正入口点）3.关掉代码生成->安全检查4.关掉增强指令集5.关掉全程序优化
然后就是最麻烦的shellcode代码编写了。首先要清楚shellcode代码的功能：
1.解压缩节表2里面的压缩数据2.将解压缩数据覆盖到PE头处，连带着空节表1也被覆盖3.还原节表、导入表、重定位表
1.要解压缩，那么必定要调用库的API，如果直接调用的话，call的就是死地址，违背了地址无关原则。那么使用LoadLibrary然后GetProcAddress？显然也不行，LoadLibrary和GetProcAddress也是死地址，所以我们要自己实现LoadLibrary和GetProcAddress的功能。
首先通过_PEB来拿到kernel32的模块基址。
HMODULE GetKernel32(){HMODULE hKer;__asm {mov eax, dword ptr fs:[0x30]mov eax, dword ptr[eax + 0x0C]mov eax, dword ptr[eax + 0x0C]mov eax, dword ptr[eax]mov eax, dword ptr[eax]mov eax, dword ptr[eax + 0x18]mov hKer, eax}return hKer;}
然后通过kernel32的导出函数表，拿到GetProcAddress函数地址，代码如下：
FARPROC MyGetProcAddress(HMODULE hMod, LPCSTR lpProcName) {IMAGE_DOS_HEADER* pDosHdr;IMAGE_NT_HEADERS* pNTHdr;IMAGE_EXPORT_DIRECTORY* pExpDir;DWORD pAddrTbl;DWORD pNameTbl;DWORD pOrdTbl;//解析dos头pDosHdr = (IMAGE_DOS_HEADER*)hMod;//nt头pNTHdr = (IMAGE_NT_HEADERS*)(pDosHdr->e_lfanew + (DWORD)hMod);//获取导出表pExpDir = (IMAGE_EXPORT_DIRECTORY*)(pNTHdr->OptionalHeader.DataDirectory[0].VirtualAddress + (DWORD)hMod);//导出函数地址表pAddrTbl = (DWORD)(pExpDir->AddressOfFunctions + (DWORD)hMod);//导出函数名称表pNameTbl = (DWORD)(pExpDir->AddressOfNames + (DWORD)hMod);//导出序号表pOrdTbl = (DWORD)(pExpDir->AddressOfNameOrdinals + (DWORD)hMod);//判断是序号还是名称if ((int)lpProcName & 0xffff0000) {//名称int i = 0;while (i < pExpDir->NumberOfNames) {//获取名称地址int nNameOff = (int)(*(DWORD*)(pNameTbl + i * 4) + (DWORD)hMod);//字符串比较if (((char*)nNameOff)[0] == 'G'&& ((char*)nNameOff)[1] == 'e'&& ((char*)nNameOff)[2] == 't'&&((char*)nNameOff)[3] == 'P'&& ((char*)nNameOff)[4] == 'r'&& ((char*)nNameOff)[5] == 'o'&&((char*)nNameOff)[6] == 'c'&& ((char*)nNameOff)[7] == 'A'&& ((char*)nNameOff)[8] == 'd'&&((char*)nNameOff)[9] == 'd'&& ((char*)nNameOff)[10] == 'r'&& ((char*)nNameOff)[11] == 'e'&&((char*)nNameOff)[12] == 's'&& ((char*)nNameOff)[13] == 's') {//找到了, 从导出序号表取出函数地址下标int nOrdinal = *(WORD*)(pOrdTbl + i * 2);//从导出地址表，下标寻址，获取导出函数地址int nFuncAddr = *(DWORD*)(pAddrTbl + nOrdinal * 4);//不是转发nFuncAddr += (int)hMod;//返回地址if (nFuncAddr != NULL) {return (FARPROC)nFuncAddr;}}i++;}}else {//序号int nOrdinal = (DWORD)lpProcName - pExpDir->Base;//从导出地址表，下标寻址，获取导出函数地址int nFuncAddr = *(DWORD*)(pAddrTbl + nOrdinal * 4);//返回地址if (nFuncAddr != NULL) {return (FARPROC)(nFuncAddr + (DWORD)hMod);}}return 0;}
有了GetProcAddress函数地址和kernel32的基址，同理就能拿到LoadLibrary函数地址了。（注意定义字符串变量时，用单个字符一个一个排列，在汇编里面看就是db出来的，否则字符串会有一个常量区地址，影响shellcode的通用性）
char szLoadLibrary[] = { 'L', 'o','a', 'd', 'L', 'i', 'b', 'r', 'a', 'r', 'y', 'A', '\0' };pEnv->pfnLoadLibraryA = (PFN_LoadLibraryA)pEnv->pfnGetProcAddress(hKer, szLoadLibrary);
2.有了LoadLibrary和GetProcAddress，就可以使用任何库函数了，解压缩便是小菜一碟。
//有了LoadLibrary和GetProcAddress，就可以使用任意函数了//获取解压缩相关函数char szCab[] = { 'C','a','b','i','n','e','t', '\0' };HMODULE hCab = pEnv->pfnLoadLibraryA(szCab);char szCreateDecompressor[] = { 'C','r','e','a','t','e','D','e','c','o','m','p','r','e','s','s','o','r', '\0' };pEnv->pfnCreateDecompressor = (PFN_CreateDecompressor)pEnv->pfnGetProcAddress(hCab, szCreateDecompressor);char szDecompress[] = { 'D','e','c','o','m','p','r','e','s','s', '\0' };pEnv->pfnDecompress = (PFN_Decompress)pEnv->pfnGetProcAddress(hCab, szDecompress);char szVirtualAlloc[] = { 'V','i','r','t','u','a','l','A','l','l','o','c', '\0' };pEnv->pfnVirtualAlloc = (PFN_VirtualAlloc)pEnv->pfnGetProcAddress(hKer, szVirtualAlloc);char szVirtualProtect[] = { 'V','i','r','t','u','a','l','P','r','o','t','e','c','t','\0' };pEnv->pfnVirtualProtect = (PFN_VirtualProtect)pEnv->pfnGetProcAddress(hKer, szVirtualProtect);//解压缩LPBYTE pPEBuff = (LPBYTE)env.pfnVirtualAlloc(NULL, dwDeComSize, MEM_COMMIT, PAGE_READWRITE);DECOMPRESSOR_HANDLE hDecompressor;BOOL bSuccess = env.pfnCreateDecompressor(COMPRESS_ALGORITHM_XPRESS_HUFF,NULL,&hDecompressor);DWORD dwDecompressedBufferSize = 0;bSuccess = env.pfnDecompress(hDecompressor,pComData,dwComSize,pPEBuff,dwDeComSize,&dwDecompressedBufferSize);
3.解压缩完毕，得到了原PE，接下来就是将原PE覆盖到现在的PE头+节表1的地方，同时还原节表头、导入表和重定位表，相当于LoadPE的功能了。
#define VirtualProtect pEnv->pfnVirtualProtectDWORD MyLoadLibrary(LPBYTE pPEBuff, Environment* pEnv, LPBYTE pTableBuf, LPBYTE pMyImpBuf) {DWORD dwImageBase;HANDLE hFile;HANDLE hFileMap;LPVOID pPEBuf;IMAGE_DOS_HEADER* pDosHdr;IMAGE_NT_HEADERS* pNTHdr;IMAGE_SECTION_HEADER* pSecHdr;DWORD dwNumOfSecs;IMAGE_IMPORT_DESCRIPTOR* pImpHdr;DWORD dwSizeOfHeaders;IMAGE_IMPORT_DESCRIPTOR hdrZeroImp;HMODULE hDll;DWORD dwOep;DWORD dwOldProc;IMAGE_BASE_RELOCATION* pReloc;DWORD dwOfReloc;DWORD dwOff;//RtlZeroMemory(&hdrZeroImp, sizeof(IMAGE_IMPORT_DESCRIPTOR));pPEBuf = pPEBuff;//解析//dos 头pDosHdr = (IMAGE_DOS_HEADER*)pPEBuf;//nt头pNTHdr = (IMAGE_NT_HEADERS*)(pDosHdr->e_lfanew + (DWORD)pPEBuf);//还原节表DWORD nSecNum = *(DWORD*)pTableBuf;mymemcpy((void*)((DWORD)&pNTHdr->OptionalHeader + pNTHdr->FileHeader.SizeOfOptionalHeader),pTableBuf + 4, nSecNum * 40);//还原导入表mymemcpy(&(pNTHdr->OptionalHeader.DataDirectory[1].VirtualAddress),pTableBuf + 4 + nSecNum * 40, 4);mymemcpy(&(pNTHdr->OptionalHeader.DataDirectory[1].Size),pTableBuf + 4 + nSecNum * 40 + 4, 4);//还原重定位表mymemcpy(&(pNTHdr->OptionalHeader.DataDirectory[5].VirtualAddress),pTableBuf + 4 + nSecNum * 40 + 4 + 4, 4);mymemcpy(&(pNTHdr->OptionalHeader.DataDirectory[5].Size),pTableBuf + 4 + nSecNum * 40 + 4 + 4 + 4, 4);//选项头信息dwSizeOfHeaders = pNTHdr->OptionalHeader.SizeOfHeaders;//自己的模块基址dwImageBase = (DWORD)GetModuleBase();dwOff = dwImageBase - pNTHdr->OptionalHeader.ImageBase; //新旧ImageBase的偏移差dwOep = pNTHdr->OptionalHeader.AddressOfEntryPoint + dwImageBase;//节表dwNumOfSecs = pNTHdr->FileHeader.NumberOfSections;pSecHdr = (IMAGE_SECTION_HEADER*)((DWORD)&pNTHdr->OptionalHeader + pNTHdr->FileHeader.SizeOfOptionalHeader);//拷贝PE头VirtualProtect((LPVOID)dwImageBase, pNTHdr->OptionalHeader.SizeOfHeaders, PAGE_EXECUTE_READWRITE, &dwOldProc);mymemcpy((void*)dwImageBase, pPEBuf, dwSizeOfHeaders);VirtualProtect((LPVOID)dwImageBase, pNTHdr->OptionalHeader.SizeOfHeaders, dwOldProc, &dwOldProc);//按照节表，拷贝节区数据int i = 0;IMAGE_SECTION_HEADER* dwSecTmp = pSecHdr;while (i < dwNumOfSecs) {//目标DWORD dwDstMem = dwImageBase;dwDstMem += dwSecTmp->VirtualAddress;//源DWORD dwSrcFile = (DWORD)pPEBuf + dwSecTmp->PointerToRawData;//拷贝VirtualProtect((LPVOID)dwDstMem, dwSecTmp->SizeOfRawData, PAGE_EXECUTE_READWRITE, &dwOldProc);mymemcpy((void*)dwDstMem, (void*)dwSrcFile, dwSecTmp->SizeOfRawData);VirtualProtect((LPVOID)dwImageBase, pNTHdr->OptionalHeader.SizeOfHeaders, dwOldProc, &dwOldProc);i++;dwSecTmp = (IMAGE_SECTION_HEADER*)((char*)dwSecTmp + sizeof(IMAGE_SECTION_HEADER));}//获取导入表if (pNTHdr->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress != 0) {pImpHdr = (IMAGE_IMPORT_DESCRIPTOR*)(dwImageBase + pNTHdr->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress);//处理导入表IMAGE_IMPORT_DESCRIPTOR* pImpHdrTmp = pImpHdr;DWORD dwNum = 0;int nImpNum = 0;while (true) {//判断结束，全0项结束if (memcmp(pImpHdrTmp, &hdrZeroImp, sizeof(IMAGE_IMPORT_DESCRIPTOR)) == 0) {break;}//判断字段, 为空则结束if (pImpHdrTmp->Name == NULL || pImpHdrTmp->FirstThunk == NULL) {break;}//加载dllhDll = pEnv->pfnLoadLibraryA((LPCSTR)(dwImageBase + pImpHdrTmp->Name));//获取导入地址表, IATDWORD dwIAT = pImpHdrTmp->FirstThunk + dwImageBase;DWORD dwINT = dwIAT;//获取导入名称表, INTif (pImpHdrTmp->OriginalFirstThunk != NULL) {dwINT = pImpHdrTmp->OriginalFirstThunk + dwImageBase;}//遍历导入名称表while (*(DWORD*)(dwINT) != 0) {if ((*(DWORD*)pImpHdrTmp) >> 31) {//序号导入, 获取序号dwNum = *(DWORD*)pImpHdrTmp;dwNum = (dwNum << 16) >> 16;}else {//名称导入dwNum = *(DWORD*)pImpHdrTmp;dwNum += dwImageBase;dwNum += 2;}//获取函数地址后，先不要把地址直接写入IAT//而是先将.imp节地址写入IAT(每16个字节写一次)//在.imp节里写代码指令push 函数地址 retn//如果函数名是_acmdln，那么这里就不要混淆导入表if (((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[0] == '_' && ((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[1] == 'a' &&((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[2] == 'c' && ((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[3] == 'm' &&((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[4] == 'd' && ((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[5] == 'l' &&((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[6] == 'n') {*(DWORD*)dwIAT = (DWORD)pEnv->pfnGetProcAddress(hDll, (LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2));}else {DWORD dwMyAddr = (DWORD)pMyImpBuf + nImpNum * 0x10;DWORD dwFuncAddr = (DWORD)pEnv->pfnGetProcAddress(hDll, (LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2));*(DWORD*)dwIAT = dwMyAddr;*(BYTE*)dwMyAddr = 0x68; //push*(DWORD*)(dwMyAddr + 1) = dwFuncAddr; //真实函数地址*(BYTE*)(dwMyAddr + 5) = 0xC3; //retn}dwIAT += 4;dwINT += 4;nImpNum++;}pImpHdrTmp = (IMAGE_IMPORT_DESCRIPTOR*)((char*)pImpHdrTmp + sizeof(IMAGE_IMPORT_DESCRIPTOR));}}if (pNTHdr->OptionalHeader.DataDirectory[5].VirtualAddress != 0) {//定位重定位表pReloc = (IMAGE_BASE_RELOCATION*)(pNTHdr->OptionalHeader.DataDirectory[5].VirtualAddress + dwImageBase);dwOfReloc = pNTHdr->OptionalHeader.DataDirectory[5].Size;int nSize = 0;while (nSize < dwOfReloc) {//数组首地址int nOff = (DWORD)pReloc + 8;//数组元素个数int nCnt = (pReloc->SizeOfBlock - 8) >> 1;//遍历数组int j = 0;while (j < nCnt) {//取出一项int nDataOff = *(WORD*)(nOff + j * 2);//判断是否是有效重定位项if (nDataOff & 0x00003000) {//修正nDataOff = nDataOff & 0x0fff; //页偏移nDataOff = nDataOff + pReloc->VirtualAddress;nDataOff = nDataOff + dwImageBase;*(int*)nDataOff = *(int*)nDataOff + dwOff;}j++;}//处理下一个分页nSize += pReloc->SizeOfBlock;pReloc = (IMAGE_BASE_RELOCATION*)((char*)pReloc + pReloc->SizeOfBlock);}}return dwOep;}
这里重点要介绍的，就是还原导入表的过程，也是整篇文章的核心主题，加点“料”。我在遍历还原导入表时，并没有直接将API的地址填入到IAT里，而是将节表5的地址，从起始位置开始，每隔16个字节，将地址填入到IAT里，然后在对应的节表5地址上填入push 真实函数地址 + retn的汇编指令。这样一来，原PE程序运行调用API时，就会跳到节表5里面，再从节表5里面跳到真实API地址，直接干掉了x64dbg的脱壳导入表自动修复功能。
//获取函数地址后，先不要把地址直接写入IAT//而是先将.imp节地址写入IAT(每16个字节写一次)//在.imp节里写代码指令push 函数地址 retn//如果函数名是_acmdln，那么这里就不要混淆导入表if (((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[0] == '_' && ((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[1] == 'a' &&((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[2] == 'c' && ((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[3] == 'm' &&((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[4] == 'd' && ((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[5] == 'l' &&((LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2))[6] == 'n') {*(DWORD*)dwIAT = (DWORD)pEnv->pfnGetProcAddress(hDll, (LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2));}else {DWORD dwMyAddr = (DWORD)pMyImpBuf + nImpNum * 0x10;DWORD dwFuncAddr = (DWORD)pEnv->pfnGetProcAddress(hDll, (LPCSTR)((*(DWORD*)(dwINT)) + dwImageBase + 2));*(DWORD*)dwIAT = dwMyAddr;*(BYTE*)dwMyAddr = 0x68; //push*(DWORD*)(dwMyAddr + 1) = dwFuncAddr; //真实函数地址*(BYTE*)(dwMyAddr + 5) = 0xC3; //retn}
五
总结
最后来看看效果，对扫雷进行加壳，加壳后的程序可以正常运行。
先用x64找到真实入口点，进行一波dump操作。
dump后无法直接运行。
然后去x64里使用自动搜索修复导入表的功能，可以看到，IAT这里存放的压根就不是真实API的地址，所以x64也无法识别出来。
搞定！
看雪ID：橘喵Cat
https://bbs.pediy.com/user-home-940656.htm
# 往期推荐
球分享
球点赞
球在看
点击“阅读原文”，了解更多！
文章来源: http://mp.weixin.qq.com/s?__biz=MjM5NTc2MDYxMw==&mid=2458465700&idx=1&sn=88c0571f7a9bd353015fb15b395c8099&chksm=b18e052e86f98c382c9d5ae0de7b9a6650d19c61b78f9c33e06db03a4434bd51fe5238d46ca6#rd
如有侵权请联系:admin#unsafe.sh
如有侵权请联系:admin#unsafe.sh