C ++：获取本机dll依赖项而不在进程中加载​​它

Question

我需要以编程方式获取 DLL 的依赖项列表。以下是我尝试解决此任务的方法：

BSTR GetDllDependencies(const wchar_t* dllPath)
{
    std::wstring dependencies;

    struct LibDeleter
    {
        typedef HMODULE pointer;
        void operator()(HMODULE hMod) { FreeLibrary(hMod); }
    };

    auto hModRaw = LoadLibraryExW(dllPath, NULL, DONT_RESOLVE_DLL_REFERENCES); //(*)nullptr nere
    auto hMod = std::unique_ptr<HMODULE, LibDeleter>();

    auto imageBase = (DWORD_PTR)hMod.get();

    auto header = ImageNtHeader(hMod.get());
    auto importRVA = header->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress;
    auto importTable = (PIMAGE_IMPORT_DESCRIPTOR)(DWORD_PTR)(importRVA + imageBase);

    while (importRVA && importTable->OriginalFirstThunk)
    {
        auto importedModuleName = (char*)(DWORD_PTR)(importTable->Name + imageBase);
        dependencies
            .append(importedModuleName, importedModuleName + std::strlen(importedModuleName))
            .append(L",");

        importTable++;
    }

    auto result = SysAllocString(dependencies.c_str());

    return result;
}

它有效。但是，如您所见，它将 DLL 加载到进程中。我在这个地方遇到了一个问题：如果进程已经加载了同名的 DLL，LoadLibraryEx 返回nullptr。

我不确定是否允许将两个同名（但位置不同）的 DLL 加载到同一个进程中？我相信是的。那为什么LoadLibraryEx 返回nullptr？是否有可能在不加载 DLL 的情况下以某种方式获取 DLL 依赖项？

Answer 1

您会发现 Matt Pietrek 的这篇文章很有趣。特别是，请查看 “PE 文件导入” 段落中的 IMAGE_IMPORT_DESCRIPTOR 数组。

Peering Inside the PE: A Tour of the Win32 Portable Executable File Format

Answer 2

此解决方案在 DLL 文件中使用手动导航。该解决方案的基础是 RVAtoRAW 函数，它将 RVA 地址转换为 RAW 地址（文件内的地址）。

//Defining in which section particular RVA address actually located (section number)
DWORD RVAtoRAW(DWORD rva, PIMAGE_SECTION_HEADER sectionHeaderRAW, WORD sectionsCount)
{
    int sectionNo;
    for (sectionNo = 0; sectionNo < sectionsCount; ++sectionNo)
    {
        auto sectionBeginRVA = sectionHeaderRAW[sectionNo].VirtualAddress;
        auto sectionEndRVA = sectionBeginRVA + sectionHeaderRAW[sectionNo].Misc.VirtualSize;
        if (sectionBeginRVA <= rva && rva <= sectionEndRVA)
            break;
    }
    //Evaluating RAW address from section & RVA
    auto sectionRAW = sectionHeaderRAW[sectionNo].PointerToRawData;
    auto sectionRVA = sectionHeaderRAW[sectionNo].VirtualAddress;
    auto raw = sectionRAW + rva - sectionRVA;

    return raw;
}

BSTR GetDllDependencies(const wchar_t* dllPath)
{
    auto buffer = ReadFile(dllPath);
    if (buffer.empty())
        return SysAllocString(L"");

    //RAW - offset from beginnig of the file (absolute "address" within file)
    auto baseRAW = buffer.data();
    auto dosHeaderRAW = (PIMAGE_DOS_HEADER)baseRAW;
    auto peHeaderRAW = (PIMAGE_NT_HEADERS)(baseRAW + dosHeaderRAW->e_lfanew);
    auto sectionHeaderRAW = (PIMAGE_SECTION_HEADER)(baseRAW + dosHeaderRAW->e_lfanew + sizeof(IMAGE_NT_HEADERS));

    auto sectionsCount = peHeaderRAW->FileHeader.NumberOfSections;

    //RVA - Relative Virtual Address - relative (to ImageBase) address within virtual address space of the process which loads this DLL
    auto importTableRVA = peHeaderRAW->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT].VirtualAddress;
    auto importTableRAW = RVAtoRAW(importTableRVA, sectionHeaderRAW, sectionsCount);
    auto importTable = (PIMAGE_IMPORT_DESCRIPTOR)(baseRAW + importTableRAW);

    std::wstring dependencies;
    while (importTableRVA && importTable->OriginalFirstThunk)
    {
        auto nameRAW = RVAtoRAW(importTable->Name, sectionHeaderRAW, sectionsCount);

        auto importedModuleName = (char*)(DWORD_PTR)(nameRAW + baseRAW);
        dependencies
            .append(importedModuleName, importedModuleName + std::strlen(importedModuleName))
            .append(L",");

        importTable++;
    }

    auto result = SysAllocString(dependencies.c_str());

    return result;
}