1
2 /* Support for dynamic loading of extension modules */
3
4 #include "Python.h"
5 #include "pycore_fileutils.h" // _Py_add_relfile()
6 #include "pycore_pystate.h" // _PyInterpreterState_GET()
7
8 #ifdef HAVE_DIRECT_H
9 #include <direct.h>
10 #endif
11 #include <ctype.h>
12
13 #include "importdl.h"
14 #include "patchlevel.h"
15 #include <windows.h>
16
17 #ifdef _DEBUG
18 #define PYD_DEBUG_SUFFIX "_d"
19 #else
20 #define PYD_DEBUG_SUFFIX ""
21 #endif
22
23 #ifdef PYD_PLATFORM_TAG
24 #define PYD_TAGGED_SUFFIX PYD_DEBUG_SUFFIX ".cp" Py_STRINGIFY(PY_MAJOR_VERSION) Py_STRINGIFY(PY_MINOR_VERSION) "-" PYD_PLATFORM_TAG ".pyd"
25 #else
26 #define PYD_TAGGED_SUFFIX PYD_DEBUG_SUFFIX ".cp" Py_STRINGIFY(PY_MAJOR_VERSION) Py_STRINGIFY(PY_MINOR_VERSION) ".pyd"
27 #endif
28
29 #define PYD_UNTAGGED_SUFFIX PYD_DEBUG_SUFFIX ".pyd"
30
31 const char *_PyImport_DynLoadFiletab[] = {
32 PYD_TAGGED_SUFFIX,
33 PYD_UNTAGGED_SUFFIX,
34 NULL
35 };
36
37 /* Function to return the name of the "python" DLL that the supplied module
38 directly imports. Looks through the list of imported modules and
39 returns the first entry that starts with "python" (case sensitive) and
40 is followed by nothing but numbers until the separator (period).
41
42 Returns a pointer to the import name, or NULL if no matching name was
43 located.
44
45 This function parses through the PE header for the module as loaded in
46 memory by the system loader. The PE header is accessed as documented by
47 Microsoft in the MSDN PE and COFF specification (2/99), and handles
48 both PE32 and PE32+. It only worries about the direct import table and
49 not the delay load import table since it's unlikely an extension is
50 going to be delay loading Python (after all, it's already loaded).
51
52 If any magic values are not found (e.g., the PE header or optional
53 header magic), then this function simply returns NULL. */
54
55 #define DWORD_AT(mem) (*(DWORD *)(mem))
56 #define WORD_AT(mem) (*(WORD *)(mem))
57
GetPythonImport(HINSTANCE hModule)58 static char *GetPythonImport (HINSTANCE hModule)
59 {
60 unsigned char *dllbase, *import_data, *import_name;
61 DWORD pe_offset, opt_offset;
62 WORD opt_magic;
63 int num_dict_off, import_off;
64
65 /* Safety check input */
66 if (hModule == NULL) {
67 return NULL;
68 }
69
70 /* Module instance is also the base load address. First portion of
71 memory is the MS-DOS loader, which holds the offset to the PE
72 header (from the load base) at 0x3C */
73 dllbase = (unsigned char *)hModule;
74 pe_offset = DWORD_AT(dllbase + 0x3C);
75
76 /* The PE signature must be "PE\0\0" */
77 if (memcmp(dllbase+pe_offset,"PE\0\0",4)) {
78 return NULL;
79 }
80
81 /* Following the PE signature is the standard COFF header (20
82 bytes) and then the optional header. The optional header starts
83 with a magic value of 0x10B for PE32 or 0x20B for PE32+ (PE32+
84 uses 64-bits for some fields). It might also be 0x107 for a ROM
85 image, but we don't process that here.
86
87 The optional header ends with a data dictionary that directly
88 points to certain types of data, among them the import entries
89 (in the second table entry). Based on the header type, we
90 determine offsets for the data dictionary count and the entry
91 within the dictionary pointing to the imports. */
92
93 opt_offset = pe_offset + 4 + 20;
94 opt_magic = WORD_AT(dllbase+opt_offset);
95 if (opt_magic == 0x10B) {
96 /* PE32 */
97 num_dict_off = 92;
98 import_off = 104;
99 } else if (opt_magic == 0x20B) {
100 /* PE32+ */
101 num_dict_off = 108;
102 import_off = 120;
103 } else {
104 /* Unsupported */
105 return NULL;
106 }
107
108 /* Now if an import table exists, offset to it and walk the list of
109 imports. The import table is an array (ending when an entry has
110 empty values) of structures (20 bytes each), which contains (at
111 offset 12) a relative address (to the module base) at which a
112 string constant holding the import name is located. */
113
114 if (DWORD_AT(dllbase + opt_offset + num_dict_off) >= 2) {
115 /* We have at least 2 tables - the import table is the second
116 one. But still it may be that the table size is zero */
117 if (0 == DWORD_AT(dllbase + opt_offset + import_off + sizeof(DWORD)))
118 return NULL;
119 import_data = dllbase + DWORD_AT(dllbase +
120 opt_offset +
121 import_off);
122 while (DWORD_AT(import_data)) {
123 import_name = dllbase + DWORD_AT(import_data+12);
124 if (strlen(import_name) >= 6 &&
125 !strncmp(import_name,"python",6)) {
126 char *pch;
127
128 /* Don't claim that python3.dll is a Python DLL. */
129 #ifdef _DEBUG
130 if (strcmp(import_name, "python3_d.dll") == 0) {
131 #else
132 if (strcmp(import_name, "python3.dll") == 0) {
133 #endif
134 import_data += 20;
135 continue;
136 }
137
138 /* Ensure python prefix is followed only
139 by numbers to the end of the basename */
140 pch = import_name + 6;
141 #ifdef _DEBUG
142 while (*pch && pch[0] != '_' && pch[1] != 'd' && pch[2] != '.') {
143 #else
144 while (*pch && *pch != '.') {
145 #endif
146 if (*pch >= '0' && *pch <= '9') {
147 pch++;
148 } else {
149 pch = NULL;
150 break;
151 }
152 }
153
154 if (pch) {
155 /* Found it - return the name */
156 return import_name;
157 }
158 }
159 import_data += 20;
160 }
161 }
162
163 return NULL;
164 }
165
166 /* Load python3.dll before loading any extension module that might refer
167 to it. That way, we can be sure that always the python3.dll corresponding
168 to this python DLL is loaded, not a python3.dll that might be on the path
169 by chance.
170 Return whether the DLL was found.
171 */
172 extern HMODULE PyWin_DLLhModule;
173 static int
174 _Py_CheckPython3(void)
175 {
176 static int python3_checked = 0;
177 static HANDLE hPython3;
178 #define MAXPATHLEN 512
179 wchar_t py3path[MAXPATHLEN+1];
180 if (python3_checked) {
181 return hPython3 != NULL;
182 }
183 python3_checked = 1;
184
185 /* If there is a python3.dll next to the python3y.dll,
186 use that DLL */
187 if (PyWin_DLLhModule && GetModuleFileNameW(PyWin_DLLhModule, py3path, MAXPATHLEN)) {
188 wchar_t *p = wcsrchr(py3path, L'\\');
189 if (p) {
190 wcscpy(p + 1, PY3_DLLNAME);
191 hPython3 = LoadLibraryExW(py3path, NULL, LOAD_LIBRARY_SEARCH_DEFAULT_DIRS);
192 if (hPython3 != NULL) {
193 return 1;
194 }
195 }
196 }
197
198 /* If we can locate python3.dll in our application dir,
199 use that DLL */
200 hPython3 = LoadLibraryExW(PY3_DLLNAME, NULL, LOAD_LIBRARY_SEARCH_APPLICATION_DIR);
201 if (hPython3 != NULL) {
202 return 1;
203 }
204
205 /* For back-compat, also search {sys.prefix}\DLLs, though
206 that has not been a normal install layout for a while */
207 PyInterpreterState *interp = _PyInterpreterState_GET();
208 PyConfig *config = (PyConfig*)_PyInterpreterState_GetConfig(interp);
209 assert(config->prefix);
210 if (config->prefix) {
211 wcscpy_s(py3path, MAXPATHLEN, config->prefix);
212 if (py3path[0] && _Py_add_relfile(py3path, L"DLLs\\" PY3_DLLNAME, MAXPATHLEN) >= 0) {
213 hPython3 = LoadLibraryExW(py3path, NULL, LOAD_LIBRARY_SEARCH_DEFAULT_DIRS);
214 }
215 }
216 return hPython3 != NULL;
217 #undef MAXPATHLEN
218 }
219
220 dl_funcptr _PyImport_FindSharedFuncptrWindows(const char *prefix,
221 const char *shortname,
222 PyObject *pathname, FILE *fp)
223 {
224 dl_funcptr p;
225 char funcname[258], *import_python;
226
227 _Py_CheckPython3();
228
229 #if USE_UNICODE_WCHAR_CACHE
230 const wchar_t *wpathname = _PyUnicode_AsUnicode(pathname);
231 #else /* USE_UNICODE_WCHAR_CACHE */
232 wchar_t *wpathname = PyUnicode_AsWideCharString(pathname, NULL);
233 #endif /* USE_UNICODE_WCHAR_CACHE */
234 if (wpathname == NULL)
235 return NULL;
236
237 PyOS_snprintf(funcname, sizeof(funcname), "%.20s_%.200s", prefix, shortname);
238
239 {
240 HINSTANCE hDLL = NULL;
241 unsigned int old_mode;
242
243 /* Don't display a message box when Python can't load a DLL */
244 old_mode = SetErrorMode(SEM_FAILCRITICALERRORS);
245
246 /* bpo-36085: We use LoadLibraryEx with restricted search paths
247 to avoid DLL preloading attacks and enable use of the
248 AddDllDirectory function. We add SEARCH_DLL_LOAD_DIR to
249 ensure DLLs adjacent to the PYD are preferred. */
250 Py_BEGIN_ALLOW_THREADS
251 hDLL = LoadLibraryExW(wpathname, NULL,
252 LOAD_LIBRARY_SEARCH_DEFAULT_DIRS |
253 LOAD_LIBRARY_SEARCH_DLL_LOAD_DIR);
254 Py_END_ALLOW_THREADS
255 #if !USE_UNICODE_WCHAR_CACHE
256 PyMem_Free(wpathname);
257 #endif /* USE_UNICODE_WCHAR_CACHE */
258
259 /* restore old error mode settings */
260 SetErrorMode(old_mode);
261
262 if (hDLL==NULL){
263 PyObject *message;
264 unsigned int errorCode;
265
266 /* Get an error string from Win32 error code */
267 wchar_t theInfo[256]; /* Pointer to error text
268 from system */
269 int theLength; /* Length of error text */
270
271 errorCode = GetLastError();
272
273 theLength = FormatMessageW(
274 FORMAT_MESSAGE_FROM_SYSTEM |
275 FORMAT_MESSAGE_IGNORE_INSERTS, /* flags */
276 NULL, /* message source */
277 errorCode, /* the message (error) ID */
278 MAKELANGID(LANG_NEUTRAL,
279 SUBLANG_DEFAULT),
280 /* Default language */
281 theInfo, /* the buffer */
282 sizeof(theInfo) / sizeof(wchar_t), /* size in wchars */
283 NULL); /* no additional format args. */
284
285 /* Problem: could not get the error message.
286 This should not happen if called correctly. */
287 if (theLength == 0) {
288 message = PyUnicode_FromFormat(
289 "DLL load failed with error code %u while importing %s",
290 errorCode, shortname);
291 } else {
292 /* For some reason a \r\n
293 is appended to the text */
294 if (theLength >= 2 &&
295 theInfo[theLength-2] == '\r' &&
296 theInfo[theLength-1] == '\n') {
297 theLength -= 2;
298 theInfo[theLength] = '\0';
299 }
300 message = PyUnicode_FromFormat(
301 "DLL load failed while importing %s: ", shortname);
302
303 PyUnicode_AppendAndDel(&message,
304 PyUnicode_FromWideChar(
305 theInfo,
306 theLength));
307 }
308 if (message != NULL) {
309 PyObject *shortname_obj = PyUnicode_FromString(shortname);
310 PyErr_SetImportError(message, shortname_obj, pathname);
311 Py_XDECREF(shortname_obj);
312 Py_DECREF(message);
313 }
314 return NULL;
315 } else {
316 char buffer[256];
317
318 PyOS_snprintf(buffer, sizeof(buffer),
319 #ifdef _DEBUG
320 "python%d%d_d.dll",
321 #else
322 "python%d%d.dll",
323 #endif
324 PY_MAJOR_VERSION,PY_MINOR_VERSION);
325 import_python = GetPythonImport(hDLL);
326
327 if (import_python &&
328 _stricmp(buffer,import_python)) {
329 PyErr_Format(PyExc_ImportError,
330 "Module use of %.150s conflicts "
331 "with this version of Python.",
332 import_python);
333 Py_BEGIN_ALLOW_THREADS
334 FreeLibrary(hDLL);
335 Py_END_ALLOW_THREADS
336 return NULL;
337 }
338 }
339 Py_BEGIN_ALLOW_THREADS
340 p = GetProcAddress(hDLL, funcname);
341 Py_END_ALLOW_THREADS
342 }
343
344 return p;
345 }
346