/* Support for dynamic loading of extension modules */

#include "Python.h"

#ifdef HAVE_DIRECT_H

#include <direct.h>

#endif

#include <ctype.h>

#include "importdl.h"

#include "patchlevel.h"

#include <windows.h>

#ifdef _DEBUG

#define PYD_DEBUG_SUFFIX "_d"

#else

#define PYD_DEBUG_SUFFIX ""

#endif

#ifdef PYD_PLATFORM_TAG

#define PYD_TAGGED_SUFFIX PYD_DEBUG_SUFFIX ".cp" Py_STRINGIFY(PY_MAJOR_VERSION) Py_STRINGIFY(PY_MINOR_VERSION) "-" PYD_PLATFORM_TAG ".pyd"

#else

#define PYD_TAGGED_SUFFIX PYD_DEBUG_SUFFIX ".cp" Py_STRINGIFY(PY_MAJOR_VERSION) Py_STRINGIFY(PY_MINOR_VERSION) ".pyd"

#endif

#define PYD_UNTAGGED_SUFFIX PYD_DEBUG_SUFFIX ".pyd"

const char *_PyImport_DynLoadFiletab[] = {

PYD_TAGGED_SUFFIX,

PYD_UNTAGGED_SUFFIX,

NULL

};

/* Function to return the name of the "python" DLL that the supplied module

directly imports. Looks through the list of imported modules and

returns the first entry that starts with "python" (case sensitive) and

is followed by nothing but numbers until the separator (period).

Returns a pointer to the import name, or NULL if no matching name was

located.

This function parses through the PE header for the module as loaded in

memory by the system loader. The PE header is accessed as documented by

Microsoft in the MSDN PE and COFF specification (2/99), and handles

both PE32 and PE32+. It only worries about the direct import table and

not the delay load import table since it's unlikely an extension is

going to be delay loading Python (after all, it's already loaded).

If any magic values are not found (e.g., the PE header or optional

header magic), then this function simply returns NULL. */

#define DWORD_AT(mem) (*(DWORD *)(mem))

#define WORD_AT(mem) (*(WORD *)(mem))

static char *GetPythonImport (HINSTANCE hModule)

{

unsigned char *dllbase, *import_data, *import_name;

DWORD pe_offset, opt_offset;

WORD opt_magic;

int num_dict_off, import_off;

/* Safety check input */

if (hModule == NULL) {

return NULL;

}

/* Module instance is also the base load address. First portion of

memory is the MS-DOS loader, which holds the offset to the PE

header (from the load base) at 0x3C */

dllbase = (unsigned char *)hModule;

pe_offset = DWORD_AT(dllbase + 0x3C);

/* The PE signature must be "PE\0\0" */

if (memcmp(dllbase+pe_offset,"PE\0\0",4)) {

return NULL;

}

/* Following the PE signature is the standard COFF header (20

bytes) and then the optional header. The optional header starts

with a magic value of 0x10B for PE32 or 0x20B for PE32+ (PE32+

uses 64-bits for some fields). It might also be 0x107 for a ROM

image, but we don't process that here.

The optional header ends with a data dictionary that directly

points to certain types of data, among them the import entries

(in the second table entry). Based on the header type, we

determine offsets for the data dictionary count and the entry

within the dictionary pointing to the imports. */

opt_offset = pe_offset + 4 + 20;

opt_magic = WORD_AT(dllbase+opt_offset);

if (opt_magic == 0x10B) {

/* PE32 */

num_dict_off = 92;

import_off = 104;

} else if (opt_magic == 0x20B) {

/* PE32+ */

num_dict_off = 108;

import_off = 120;

} else {

/* Unsupported */

return NULL;

}

/* Now if an import table exists, offset to it and walk the list of

imports. The import table is an array (ending when an entry has

empty values) of structures (20 bytes each), which contains (at

offset 12) a relative address (to the module base) at which a

string constant holding the import name is located. */

if (DWORD_AT(dllbase + opt_offset + num_dict_off) >= 2) {

/* We have at least 2 tables - the import table is the second

one. But still it may be that the table size is zero */

if (0 == DWORD_AT(dllbase + opt_offset + import_off + sizeof(DWORD)))

return NULL;

import_data = dllbase + DWORD_AT(dllbase +

opt_offset +

import_off);

while (DWORD_AT(import_data)) {

import_name = dllbase + DWORD_AT(import_data+12);

if (strlen(import_name) >= 6 &&

!strncmp(import_name,"python",6)) {

char *pch;

/* Don't claim that python3.dll is a Python DLL. */

#ifdef _DEBUG

if (strcmp(import_name, "python3_d.dll") == 0) {

#else

if (strcmp(import_name, "python3.dll") == 0) {

#endif

import_data += 20;

continue;

}

/* Ensure python prefix is followed only

by numbers to the end of the basename */

pch = import_name + 6;

#ifdef _DEBUG

while (*pch && pch[0] != '_' && pch[1] != 'd' && pch[2] != '.') {

#else

while (*pch && *pch != '.') {

#endif

if (*pch >= '0' && *pch <= '9') {

pch++;

} else {

pch = NULL;

break;

}

}

if (pch) {

/* Found it - return the name */

return import_name;

}

}

import_data += 20;

}

}

return NULL;

}

dl_funcptr _PyImport_FindSharedFuncptrWindows(const char *prefix,

const char *shortname,

PyObject *pathname, FILE *fp)

{

dl_funcptr p;

char funcname[258], *import_python;

_Py_CheckPython3();

#if USE_UNICODE_WCHAR_CACHE

const wchar_t *wpathname = _PyUnicode_AsUnicode(pathname);

#else /* USE_UNICODE_WCHAR_CACHE */

wchar_t *wpathname = PyUnicode_AsWideCharString(pathname, NULL);

#endif /* USE_UNICODE_WCHAR_CACHE */

if (wpathname == NULL)

return NULL;

PyOS_snprintf(funcname, sizeof(funcname), "%.20s_%.200s", prefix, shortname);

{

HINSTANCE hDLL = NULL;

unsigned int old_mode;

/* Don't display a message box when Python can't load a DLL */

old_mode = SetErrorMode(SEM_FAILCRITICALERRORS);

/* bpo-36085: We use LoadLibraryEx with restricted search paths

to avoid DLL preloading attacks and enable use of the

AddDllDirectory function. We add SEARCH_DLL_LOAD_DIR to

ensure DLLs adjacent to the PYD are preferred. */

Py_BEGIN_ALLOW_THREADS

hDLL = LoadLibraryExW(wpathname, NULL,

LOAD_LIBRARY_SEARCH_DEFAULT_DIRS |

LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR);

Py_END_ALLOW_THREADS

#if !USE_UNICODE_WCHAR_CACHE

PyMem_Free(wpathname);

#endif /* USE_UNICODE_WCHAR_CACHE */

/* restore old error mode settings */

SetErrorMode(old_mode);

if (hDLL==NULL){

PyObject *message;

unsigned int errorCode;

/* Get an error string from Win32 error code */

wchar_t theInfo[256]; /* Pointer to error text

from system */

int theLength; /* Length of error text */

errorCode = GetLastError();

theLength = FormatMessageW(

FORMAT_MESSAGE_FROM_SYSTEM |

FORMAT_MESSAGE_IGNORE_INSERTS, /* flags */

NULL, /* message source */

errorCode, /* the message (error) ID */

MAKELANGID(LANG_NEUTRAL,

SUBLANG_DEFAULT),

/* Default language */

theInfo, /* the buffer */

sizeof(theInfo) / sizeof(wchar_t), /* size in wchars */

NULL); /* no additional format args. */

/* Problem: could not get the error message.

This should not happen if called correctly. */

if (theLength == 0) {

message = PyUnicode_FromFormat(

"DLL load failed with error code %u while importing %s",

errorCode, shortname);

} else {

/* For some reason a \r\n

is appended to the text */

if (theLength >= 2 &&

theInfo[theLength-2] == '\r' &&

theInfo[theLength-1] == '\n') {

theLength -= 2;

theInfo[theLength] = '\0';

}

message = PyUnicode_FromFormat(

"DLL load failed while importing %s: ", shortname);

PyUnicode_AppendAndDel(&message,

PyUnicode_FromWideChar(

theInfo,

theLength));

}

if (message != NULL) {

PyObject *shortname_obj = PyUnicode_FromString(shortname);

PyErr_SetImportError(message, shortname_obj, pathname);

Py_XDECREF(shortname_obj);

Py_DECREF(message);

}

return NULL;

} else {

char buffer[256];

PyOS_snprintf(buffer, sizeof(buffer),

#ifdef _DEBUG

"python%d%d_d.dll",

#else

"python%d%d.dll",

#endif

PY_MAJOR_VERSION,PY_MINOR_VERSION);

import_python = GetPythonImport(hDLL);

if (import_python &&

_stricmp(buffer,import_python)) {

PyErr_Format(PyExc_ImportError,

"Module use of %.150s conflicts "

"with this version of Python.",

import_python);

Py_BEGIN_ALLOW_THREADS

FreeLibrary(hDLL);

Py_END_ALLOW_THREADS

return NULL;

}

}

Py_BEGIN_ALLOW_THREADS

p = GetProcAddress(hDLL, funcname);

Py_END_ALLOW_THREADS

}

return p;

}