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windows - VirtualProtectEx，ERROR_INVALID_PARAMETER（错误 87）

问题描述

我正在尝试编写一个可以通过进程内存的函数。我注意到 ReadProcessMemory 在权限设置为 PAGE_NOACCESS 或 PAGE_GUARD 的区域上会失败。我决定使用 VirtualProtectEx 临时更改这些页面的权限，以便能够阅读它们。这似乎在大多数情况下都有效，但总会有少数情况下 VirtualProtectEx 会因 ERROR_INVALID_PARAMETER 而失败。我对所有参数进行了三重检查，它们似乎是正确的，我什至添加了在失败时再次调用 VirtualQueryEx 的代码，以确保传递的参数仍然有效。是什么原因造成的，我该如何解决？我在下面添加了一些最小（尽可能少）的代码来重现问题。

int protect_test(DWORD pid) {

    HANDLE phandle;

    struct _MEMORY_BASIC_INFORMATION mbi;
    SIZE_T mbi_size = sizeof(struct _MEMORY_BASIC_INFORMATION);
    DWORD state;
    SIZE_T regionsize;

    int bytes_retrieved;
    void* lpAddress;
    void* lpBaseAddress;
    void* lpAddress2;
    int error;
    struct _SYSTEM_INFO lpSystemInfo;
    DWORD pagesize;

    DWORD protect;
    DWORD newprotect;
    DWORD lpflOldProtect;
    DWORD lpExitCode = 0;

    // get the page size
    GetSystemInfo(&lpSystemInfo);
    pagesize = lpSystemInfo.dwPageSize;

    // get handle to process
    if ((phandle = OpenProcess(PROCESS_ALL_ACCESS, 0, pid)) == NULL) {
        return(-1);
    }

    // main loop
    lpAddress = 0;
    while (!((bytes_retrieved = VirtualQueryEx(phandle, lpAddress, &mbi, mbi_size)) == 0 && (error = GetLastError()) == ERROR_INVALID_PARAMETER)) {

        // Check for error -2
        if (GetExitCodeProcess(phandle, &lpExitCode) && lpExitCode != 259) {
            // process was closed abruptly 
            return -2;
        }

        // handle VirtualQueryEx fail
        if (bytes_retrieved == 0) {
            lpBaseAddress = lpAddress;
            lpAddress2 = (unsigned long long) lpAddress + pagesize;
            lpAddress = lpAddress2;
            continue;
        }

        // set variables so we don't have to refernce mbi directly 
        lpBaseAddress = mbi.BaseAddress;
        regionsize = mbi.RegionSize;
        lpAddress2 = (unsigned long long)lpBaseAddress + regionsize;
        state = mbi.State;
        protect = mbi.Protect;


        if ( state == MEM_COMMIT && ((protect & PAGE_NOACCESS) || (protect & PAGE_GUARD)) ) {

            // some debug print
            //printf(" State: 0x%x Protection: 0x%x Regionsize: 0x%llx %p - %p\n", state, protect, regionsize, lpBaseAddress, (unsigned long long)lpAddress2 - 1);

            // The problematic VirtualProtectEx call
            newprotect = PAGE_EXECUTE_READWRITE;
            if (VirtualProtectEx(phandle, lpBaseAddress, regionsize, newprotect, &lpflOldProtect) == NULL) {
                printf("   Failed to change region's protection to 0x%x. Base address: 0x%p Errorcode: 0x%x\n", newprotect, lpBaseAddress, GetLastError());
                printf("   VirtualQuery returns %d. The base address returned was 0x%o. The regionsize returned is 0x%llx\n", VirtualQueryEx(phandle, lpBaseAddress, &mbi, mbi_size), mbi.BaseAddress, mbi.RegionSize);
                return(1);
            }

            // set things back
            if (VirtualProtectEx(phandle, lpBaseAddress, regionsize, lpflOldProtect, &lpflOldProtect) == 0) {
                printf("   Failed to change region's protection back to its previous state\n", pid);
            }

        }

        // update lpAddress
        lpAddress = lpAddress2;
    }

    return 0;
}

标签： windowsapipermissionsvirtual-memoryvirtualquery

解决方案

您无法更改该页面的权限。

使用

if ( state == MEM_COMMIT && ((protect & PAGE_NOACCESS) || (protect & PAGE_GUARD)) )

您只需要过滤掉坏内存，您无需更改具有其他状态和保护的页面的权限。其他页面类型中的“隐藏数据”将非常罕见，例如 0.000001% 的机会，甚至不值得考虑，除非您有理由在使用一些非常先进的保护机制的情况下怀疑它。

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