确定PE文件中目录RVA的物理文件地址

Question

如何确定PE文件中特定数据目录的图像地址（文件中的字节偏移）？

例如，给定数据目录如下：

directory  1  RVA: 0x0  Size: 0
directory  2  RVA: 0xaf974  Size: 300
directory  3  RVA: 0xb8000  Size: 22328
directory  4  RVA: 0x0  Size: 0
directory  5  RVA: 0xc0800  Size: 6440
directory  6  RVA: 0xbe000  Size: 27776
directory  7  RVA: 0x91760  Size: 28
directory  8  RVA: 0x0  Size: 0
directory  9  RVA: 0x0  Size: 0
directory 10  RVA: 0x0  Size: 0
directory 11  RVA: 0xa46b8  Size: 64
directory 12  RVA: 0x0  Size: 0
directory 13  RVA: 0x91000  Size: 1736
directory 14  RVA: 0x0  Size: 0
directory 15  RVA: 0x0  Size: 0
directory 16  RVA: 0x0  Size: 0

导入目录（上面的#2）显示为 RVA 为 0xAF974。但是，导入目录不位于 EXE 文件的字节 0xAF974。文件写入磁盘时，如何计算文件中导入目录的字节偏移量？

Answer 1

这很有趣！您必须遍历部分以根据其虚拟地址找到正确的位置。这是我经过大量编写的一些代码

我可以试着解释一下，但是我自己花了很多时间来理解它，而且我已经有几个星期没有看它了，而且我已经忘记了很多技术性的东西。我也在写一个 C++ 类来处理很多这样的事情

在我的代码缓冲区中是一个指向 MapViewOfFile 的指针，但它可以是任何字符指针。

/* Example usage...I know not perfect but should help a bit. */
    unsigned char * lpFile = (unsigned char *)(void *)MapViewOfFile(fileMap, FILE_MAP_ALL_ACCESS, 0,0, 0);

    if(lpFile==NULL) {
        printf("Failed to MapViewOfFile\r\n");
        exit(0);
    }

    header_dos = (PIMAGE_DOS_HEADER)lpFile;
    header_nt = (PIMAGE_NT_HEADERS32)&lpFile [header_dos->e_lfanew];

    IMAGE_DATA_DIRECTORY import = header_nt->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_IMPORT];
    PIMAGE_IMPORT_DESCRIPTOR im = (PIMAGE_IMPORT_DESCRIPTOR)&lpFile[RVA2Offset(lpFile, import.VirtualAddress)];


        /* RVA is relative to the section it resides in. */
    int RVA2Offset(unsigned char * buffer, DWORD rva)
    {
        PIMAGE_NT_HEADERS header = (PIMAGE_NT_HEADERS) &buffer[ ((PIMAGE_DOS_HEADER)buffer)->e_lfanew ];
        PIMAGE_SECTION_HEADER section = (PIMAGE_SECTION_HEADER) &buffer[ ((PIMAGE_DOS_HEADER)buffer)->e_lfanew + sizeof(IMAGE_NT_HEADERS) ];

        for(int sectionIndex = 0; sectionIndex < header->FileHeader.NumberOfSections; sectionIndex++) {
            /*
                Check if the RVA is within the virtual addressing space of the section
                Make sure the RVA is less than  the VirtualAddress plus its raw data size
                IMAGE_HEADER_SECTION.VirtualAddress = The address of the first byte of the section when loaded into memory, relative to the image base. For object files, this is the address of the first byte before relocation is applied.
                Our ImageBase is 0, since we aren't loaded into actual memory
            */
            section = (PIMAGE_SECTION_HEADER) &buffer[ ((PIMAGE_DOS_HEADER)buffer)->e_lfanew + sizeof(IMAGE_NT_HEADERS) + (sectionIndex*sizeof(IMAGE_SECTION_HEADER))];

            if (rva >= section->VirtualAddress && (rva <= section->VirtualAddress + section->SizeOfRawData)) {
                /**
                    PointerToRawData gives us the section's location within the file.
                    RVA - VirtualAddress = Offset WITHIN the address space
                **/
                return section->PointerToRawData + (rva - section->VirtualAddress);
            }
        }

        return 0;
    }