c++ - VirtualProtect 和 kernel32.dll - 尝试访问无效地址

Question

我正在分析进程加载的各种模块。不幸的是，我无法创建 kernel32.dll 内存快照，尽管该函数可以与其他模块(例如 ntddl.dll)一起正常工作。问题在于以下代码:

/* Copy code from memory  */
if (VirtualProtect((BYTE*)virtualAddress, sizeOfCode, PAGE_EXECUTE_READWRITE, &flags) == 0) {
    std::cout << "VirtualProtect failed!" << std::endl;
    std::cout << "Virtual address: " << virtualAddress << std::endl;
    std::cout << "Size of code: " << sizeOfCode << std::endl;
    std::cout << "Error code: " << GetLastError() << std::endl;
}

为 kernel32.dll 调用这段代码的结果是:

Virtual address: 747d0000
Size of code: 6a000
Error code: 0x1e7

错误描述是这样说的:

ERROR_INVALID_ADDRESS
487 (0x1E7)
Attempt to access invalid address. 

我检查了进程的内存映射和 kernel32.dll 地址是正确的。这是什么原因？

Answer 1

很难验证您的地址是否正确，它异常低。我刚刚写了另一个程序来测试这个。它枚举 kernel32.dll 中的区域并对它们调用 VirtualProtect():

#include <Windows.h>
#include <assert.h>
#include <iostream>


int main()
{
    HMODULE hmod = GetModuleHandle(L"kernel32.dll");
    MEMORY_BASIC_INFORMATION info;
    // Start at PE32 header
    SIZE_T len = VirtualQuery(hmod, &info, sizeof(info));
    assert(len > 0);
    BYTE* dllBase = (BYTE*)info.AllocationBase;
    BYTE* address = dllBase;
    for (;;) {
        len = VirtualQuery(address, &info, sizeof(info));
        assert(len > 0);
        if (info.AllocationBase != dllBase) break;
        std::cout << "Address: " << std::hex << info.BaseAddress;
        std::cout << " (" << std::hex << info.RegionSize << ") ";
        std::cout << " protect = " << std::hex << info.Protect;
        DWORD oldprotect;
        if (info.Protect == 0) std::cout << ", VirtualProtect skipped" << std::endl;
        else {
            BOOL ok = VirtualProtect(info.BaseAddress, info.RegionSize, PAGE_EXECUTE_READWRITE, &oldprotect);
            std::cout << ", VirtualProtect = " << (ok ? "okay" : "Failed!") << std::endl;
        }
        address = (BYTE*)info.BaseAddress + info.RegionSize;
    }
    return 0;
}

此程序在我的机器上的输出，运行 Windows 8.1 x64:

Address: 77470000 (1000)  protect = 2, VirtualProtect = okay
Address: 77471000 (f000)  protect = 0, VirtualProtect skipped
Address: 77480000 (62000)  protect = 20, VirtualProtect = okay
Address: 774E2000 (e000)  protect = 0, VirtualProtect skipped
Address: 774F0000 (7e000)  protect = 2, VirtualProtect = okay
Address: 7756E000 (2000)  protect = 0, VirtualProtect skipped
Address: 77570000 (1000)  protect = 4, VirtualProtect = okay
Address: 77571000 (f000)  protect = 0, VirtualProtect skipped
Address: 77580000 (1000)  protect = 2, VirtualProtect = okay
Address: 77581000 (f000)  protect = 0, VirtualProtect skipped
Address: 77590000 (1a000)  protect = 2, VirtualProtect = okay
Address: 775AA000 (6000)  protect = 0, VirtualProtect skipped

在 64 位模式下运行:

Address: 00007FFC4F870000 (1000)  protect = 2, VirtualProtect = okay
Address: 00007FFC4F871000 (112000)  protect = 20, VirtualProtect = okay
Address: 00007FFC4F983000 (1000)  protect = 4, VirtualProtect = okay
Address: 00007FFC4F984000 (1000)  protect = 8, VirtualProtect = okay
Address: 00007FFC4F985000 (24000)  protect = 2, VirtualProtect = okay

很明显，您的 Windows 版本不同，因此请务必在您的计算机上运行该程序以获得可比较的结果。

我得出的结论是，这种代码失败没有根本原因。如果它在您的机器上发生，那很可能是环境问题。有一个非常明显的候选者是您的反恶意软件，这当然在防止代码与 kernel32.dll 混淆方面有很大的利害关系。我在我的机器上运行最低限度的保护。