今天我遇到了解决Windows Portable Executable文件结构的问题时遇到了一个非常奇怪的问题。特别是在导出表中。
在尝试解析DLL中导出函数的函数地址时，我发现自己得到了Stack Overflow（所以这看起来像是最合适的QA板）。
我编写了自己的GetProcAddress版本，它手动执行解析，而不是调用现有的GetProcAddress方法。请不要只是告诉我使用现有的GetProcAddress方法，它不适合我目前的情况，我想从中学到一些东西。
对于我遇到的大多数情况，我的版本工作得非常好，并没有遇到任何问题。但是，该函数是针对名为API-MS-Win-Core-ProcessThreads-L1-1-0.dll的DLL（作为Kernel32.dll的递归解析的一部分）进行测试的，这是StackOverflow发生的时间。
我已将其缩小为从API-MS-Win-Core-ProcessThreads-L1-1-0.dll导出的以下函数：
CreateRemoteThreadEx
现在，此导出的功能实际上是转发导出。通常这不用担心;我编写了我的函数，以便它应该处理转发的导出。但是，此功能转发到
api-ms-win-core-processthreads-l1-1-0.CreateRemoteThreadEx
有人在这里看到问题吗？单步执行代码，我的GetProcAddress函数会在LoadLibrary上调用api-ms-win-core-processthreads-l1-1-0，然后尝试递归查找CreateRemoteThreadEx。但是，在下一次迭代中，CreateRemoteThreadEx函数再次转发到
api-ms-win-core-processthreads-l1-1-0.CreateRemoteThreadEx
开始StackOverflow。经过一番调查后，我发现调用的结果是
LoadLibraryA("api-ms-win-core-processthreads-l1-1-0");
返回与
相同的结果LoadLibraryA("kernel32.dll");
我很难过。
这是我目前的代码：
#include <Windows.h>
#define MKPTR(p1,p2) ((DWORD_PTR)(p1) + (DWORD_PTR)(p2))
INT LookupExport(IMAGE_DOS_HEADER* pDosHd, DWORD* pNames, DWORD nNames, LPCSTR lpProcName)
{
// Do a binary search on the name pointer table
INT start = 0,
index = -1,
middle = -1,
end = nNames - 1,
cmp = 0;
CHAR *pName;
while (start <= end && index == -1)
{
middle = (start + end) >> 1;
pName = (CHAR*)MKPTR(pDosHd, pNames[middle]);
if ((cmp = strcmp(pName, lpProcName)) == 0)
index = middle; // found
else if (cmp < 0)
start = middle + 1;
else
end = middle;
}
return index;
}
FARPROC InternalGetProcAddress(HMODULE hModule, LPCSTR lpProcName)
{
BOOL ordinalSearch = HIWORD(lpProcName) == 0;
WORD ordinal = 0;
IMAGE_DOS_HEADER *pDosHd = (IMAGE_DOS_HEADER*)hModule;
if (pDosHd->e_magic != IMAGE_DOS_SIGNATURE)
return NULL;
IMAGE_NT_HEADERS *pNtHd = (IMAGE_NT_HEADERS*)MKPTR(pDosHd, pDosHd->e_lfanew);
if (pNtHd->Signature != IMAGE_NT_SIGNATURE)
return NULL;
IMAGE_DATA_DIRECTORY directory = pNtHd->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
if (directory.Size == 0 || directory.VirtualAddress == 0)
return NULL;
IMAGE_EXPORT_DIRECTORY *pExports = (IMAGE_EXPORT_DIRECTORY*)MKPTR(pDosHd, directory.VirtualAddress);
if (!ordinalSearch)
{
INT index = LookupExport(pDosHd, (DWORD*)MKPTR(pDosHd, pExports->AddressOfNames), pExports->NumberOfNames, lpProcName);
if (index == -1)
return NULL;
ordinal = ((WORD*)MKPTR(pDosHd, pExports->AddressOfNameOrdinals))[index];
}
else
{
ordinal = LOWORD(lpProcName);
}
INT delta = pExports->Base - 1;
DWORD dwAddress = ((DWORD*)MKPTR(pDosHd, pExports->AddressOfFunctions))[ordinal - delta];
// Check whether forwarded:
if (dwAddress >= directory.VirtualAddress && dwAddress < (directory.VirtualAddress + directory.Size))
{
CHAR pForward[256];
strcpy(pForward, (CHAR*)MKPTR(pDosHd, dwAddress));
CHAR *pFunction = strchr(pForward, '.');
if (pFunction == NULL)
return NULL;
// break into seperate parts and recurse
*pFunction++ = 0;
return InternalGetProcAddress(LoadLibraryA(pForward), pFunction);
}
return (FARPROC)MKPTR(hModule, dwAddress);
}
非常感谢任何见解。
答案 0 :(得分：1)
好的，按照@ sergmat的建议，我看了一下API Set文档（找到感兴趣的人here）。我现在修改了我的GetProcAddress代码，以便对Api Set表进行简单的查找。
#include <Windows.h>
#define MKPTR(p1,p2) ((DWORD_PTR)(p1) + (DWORD_PTR)(p2))
typedef struct _stripped_peb32 {
BYTE unused1[0x038];
PVOID ApiSet;
BYTE unused2[0x1AC];
} PEB32;
typedef struct _stripped_peb64 {
BYTE unused1[0x068];
PVOID ApiSet;
BYTE unused2[0x23C];
} PEB64;
typedef struct _PROCESS_BASIC_INFORMATION {
PVOID Reserved1;
LPVOID PebBaseAddress;
PVOID Reserved2[2];
ULONG_PTR UniqueProcessId;
PVOID Reserved3;
} PROCESS_BASIC_INFORMATION;
typedef struct _api_set_host {
DWORD ImportModuleName;
WORD ImportModuleNameLength;
DWORD HostModuleName;
WORD HostModuleNameLength;
} API_SET_HOST;
typedef struct _api_set_host_descriptor {
DWORD NumberOfHosts;
API_SET_HOST Hosts[1];
} API_SET_HOST_DESCRIPTOR;
typedef struct _api_set_entry {
DWORD Name;
WORD NameLength;
DWORD HostDescriptor;
} API_SET_ENTRY;
typedef struct _api_set_header {
DWORD unknown1;
DWORD NumberOfEntries;
API_SET_ENTRY Entries[1];
} API_SET_HEADER;
typedef NTSTATUS (__stdcall *fnNtQueryInformationProcess)(HANDLE ProcessHandle, DWORD ProcessInformationClass, PVOID ProcessInformation, ULONG ProcessInformationLength, PULONG ReturnLength);
API_SET_HEADER *GetApiSetHeader()
{
fnNtQueryInformationProcess NtQueryInformationProcess = (fnNtQueryInformationProcess)GetProcAddress(LoadLibraryW(L"ntdll.dll"), "NtQueryInformationProcess");
if (!NtQueryInformationProcess)
return NULL;
PROCESS_BASIC_INFORMATION info;
if (NtQueryInformationProcess(GetCurrentProcess(), 0, &info, sizeof(info), NULL) != S_OK)
return NULL;
#if defined(_WIN32)
return (API_SET_HEADER*)(((PEB32*)info.PebBaseAddress)->ApiSet);
#elif defined(_WIN64)
return (API_SET_HEADER*)(((PEB64*)info.PebBaseAddress)->ApiSet);
#else
return NULL; // unsupported architecture
#endif
}
HMODULE ResolveImportMap(LPCSTR lpModuleName)
{
API_SET_HEADER *pHeader = GetApiSetHeader();
if (pHeader == NULL)
return NULL;
API_SET_ENTRY *pEntry = pHeader->Entries;
API_SET_HOST_DESCRIPTOR* pDescriptor;
wchar_t module[128];
// First, normalize the LPCSTR, the API Set table doesn't have the API- prefix
if (strnicmp("api-", lpModuleName, 4) == 0)
lpModuleName += 4;
// Next convert the LPCSTR to a unicode string for comparison and remove the extension (if found)
mbstowcs(module, lpModuleName, sizeof(module) / sizeof(wchar_t));
wchar_t *dot = wcsrchr(module, L'.');
if (dot) *dot = L'\0';
// Begin the lookup:
// todo: implement a case-insensitive binary search, not much to be gained for the effort IMO as there's
// only 35 entries in the current version of Windows 7, but the option is there for performance nuts.
for(unsigned long i = 0; i < pHeader->NumberOfEntries; ++i, ++pEntry)
{
// Check the top-level host map
if (wcsnicmp(module, (const wchar_t*)MKPTR(pHeader, pEntry->Name), pEntry->NameLength) == 0)
{
pDescriptor = (API_SET_HOST_DESCRIPTOR*)MKPTR(pHeader, pEntry->HostDescriptor);
// iterate backwards through the hosts to find the most important one (I think this is naive)
for(unsigned long j = pDescriptor->NumberOfHosts; j > 0; --j)
{
if (pDescriptor->Hosts[j - 1].HostModuleNameLength)
{
memcpy(module, (const void*)MKPTR(pHeader, pDescriptor->Hosts[j - 1].HostModuleName), pDescriptor->Hosts[j - 1].HostModuleNameLength);
module[pDescriptor->Hosts[j - 1].HostModuleNameLength / sizeof(wchar_t)] = L'\0';
return GetModuleHandleW(module); // All the modules should already be loaded, so use GetModuleHandle rather than LoadLibrary
}
}
}
}
return NULL;
}
INT LookupExport(IMAGE_DOS_HEADER* pDosHd, DWORD* pNames, DWORD nNames, LPCSTR lpProcName)
{
// Do a binary search on the name pointer table
INT start = 0,
index = -1,
middle = -1,
end = nNames - 1,
cmp = 0;
CHAR *pName;
while (start <= end && index == -1)
{
middle = (start + end) >> 1;
pName = (CHAR*)MKPTR(pDosHd, pNames[middle]);
if ((cmp = strcmp(pName, lpProcName)) == 0)
index = middle;
else if (cmp < 0)
start = middle + 1;
else
end = middle;
}
return index;
}
FARPROC InternalGetProcAddress(HMODULE hModule, LPCSTR lpProcName)
{
if (hModule == NULL)
return NULL;
BOOL ordinalSearch = HIWORD(lpProcName) == 0;
WORD ordinal = 0;
IMAGE_DOS_HEADER *pDosHd = (IMAGE_DOS_HEADER*)hModule;
if (pDosHd->e_magic != IMAGE_DOS_SIGNATURE)
return NULL;
IMAGE_NT_HEADERS *pNtHd = (IMAGE_NT_HEADERS*)MKPTR(pDosHd, pDosHd->e_lfanew);
if (pNtHd->Signature != IMAGE_NT_SIGNATURE)
return NULL;
IMAGE_DATA_DIRECTORY directory = pNtHd->OptionalHeader.DataDirectory[IMAGE_DIRECTORY_ENTRY_EXPORT];
if (directory.Size == 0 || directory.VirtualAddress == 0)
return NULL;
IMAGE_EXPORT_DIRECTORY *pExports = (IMAGE_EXPORT_DIRECTORY*)MKPTR(pDosHd, directory.VirtualAddress);
if (!ordinalSearch)
{
INT index = LookupExport(pDosHd, (DWORD*)MKPTR(pDosHd, pExports->AddressOfNames), pExports->NumberOfNames, lpProcName);
if (index == -1)
return NULL;
ordinal = ((WORD*)MKPTR(pDosHd, pExports->AddressOfNameOrdinals))[index];
}
else
{
ordinal = LOWORD(lpProcName);
}
INT ordbase = pExports->Base - 1;
DWORD dwAddress = ((DWORD*)MKPTR(pDosHd, pExports->AddressOfFunctions))[ordinal - ordbase];
// Check whether forwarded:
if (dwAddress >= directory.VirtualAddress && dwAddress < (directory.VirtualAddress + directory.Size))
{
CHAR pForward[256];
strcpy(pForward, (CHAR*)MKPTR(pDosHd, dwAddress));
CHAR *pFunction = strchr(pForward, '.');
if (pFunction == NULL)
return NULL;
// break into seperate parts and recurse
*pFunction++ = 0;
// check if ordinal-forwarded
if (*pFunction == '#')
pFunction = (PSTR)(unsigned short)(atoi(++pFunction));
HMODULE hDestination = LoadLibraryA(pForward);
// detect an infinite loop, the forward declaration requests the same module handle with
// the same function lookup, this could be an Api Set (Windows7+)
if (hDestination == hModule && (ordinalSearch ? LOWORD(pFunction) == LOWORD(lpProcName) : strcmp(pFunction, lpProcName) == 0))
hDestination = ResolveImportMap(pForward); // ResolveImportMap will return NULL if not an API Set and so avoid infinite recursion
return InternalGetProcAddress(hDestination, pFunction);
}
return (FARPROC)MKPTR(hModule, dwAddress);
}