实现一个压缩壳，并给它加点“料”

admin

100990
文章

86
评论

2023年3月6日19:53:48评论9 views字数 16686阅读55分37秒阅读模式

实现一个压缩壳，并给它加点“料”

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。
实现一个压缩壳，并给它加点“料”
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', '' };    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', '' };    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', '' };    pEnv->pfnCreateDecompressor = (PFN_CreateDecompressor)pEnv->pfnGetProcAddress(hCab, szCreateDecompressor);     char szDecompress[] = { 'D','e','c','o','m','p','r','e','s','s', '' };    pEnv->pfnDecompress = (PFN_Decompress)pEnv->pfnGetProcAddress(hCab, szDecompress);     char szVirtualAlloc[] = { 'V','i','r','t','u','a','l','A','l','l','o','c', '' };    pEnv->pfnVirtualAlloc = (PFN_VirtualAlloc)pEnv->pfnGetProcAddress(hKer, szVirtualAlloc);     char szVirtualProtect[] = { 'V','i','r','t','u','a','l','P','r','o','t','e','c','t','' };    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dll            hDll = pEnv->pfnLoadLibraryA((LPCSTR)(dwImageBase + pImpHdrTmp->Name));             //获取导入地址表, IAT            DWORD dwIAT = pImpHdrTmp->FirstThunk + dwImageBase;            DWORD dwINT = dwIAT;            //获取导入名称表, INT            if (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。
实现一个压缩壳，并给它加点“料”
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。
实现一个压缩壳，并给它加点“料”
搞定！‍