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Detect conflicting Python DLL on module import under Windows - as per [ Patch #101676 ]
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‎Python/dynload_win.c‎

Lines changed: 152 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -3,6 +3,7 @@
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#include <windows.h>
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#include <direct.h>
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#include <ctype.h>
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#include "Python.h"
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#include "importdl.h"
@@ -19,11 +20,144 @@ const struct filedescr _PyImport_DynLoadFiletab[] = {
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};
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#ifdef MS_WIN32
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/* Case insensitive string compare, to avoid any dependencies on particular
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C RTL implementations */
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static int strcasecmp (char *string1, char *string2)
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{
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int first, second;
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do {
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first = tolower(*string1);
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second = tolower(*string2);
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string1++;
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string2++;
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} while (first && first == second);
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return (first - second);
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}
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/* Function to return the name of the "python" DLL that the supplied module
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directly imports. Looks through the list of imported modules and
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returns the first entry that starts with "python" (case sensitive) and
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is followed by nothing but numbers until the separator (period).
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Returns a pointer to the import name, or NULL if no matching name was
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located.
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This function parses through the PE header for the module as loaded in
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memory by the system loader. The PE header is accessed as documented by
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Microsoft in the MSDN PE and COFF specification (2/99), and handles
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both PE32 and PE32+. It only worries about the direct import table and
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not the delay load import table since it's unlikely an extension is
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going to be delay loading Python (after all, it's already loaded).
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If any magic values are not found (e.g., the PE header or optional
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header magic), then this function simply returns NULL. */
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#define DWORD_AT(mem) (*(DWORD *)(mem))
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#define WORD_AT(mem) (*(WORD *)(mem))
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static char *GetPythonImport (HINSTANCE hModule)
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{
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unsigned char *dllbase, *import_data, *import_name;
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DWORD pe_offset, opt_offset;
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WORD opt_magic;
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int num_dict_off, import_off;
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/* Safety check input */
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if (hModule == NULL) {
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return NULL;
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}
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/* Module instance is also the base load address. First portion of
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memory is the MS-DOS loader, which holds the offset to the PE
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header (from the load base) at 0x3C */
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dllbase = (unsigned char *)hModule;
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pe_offset = DWORD_AT(dllbase + 0x3C);
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/* The PE signature must be "PE\0\0" */
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if (memcmp(dllbase+pe_offset,"PE\0\0",4)) {
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return NULL;
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}
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/* Following the PE signature is the standard COFF header (20
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bytes) and then the optional header. The optional header starts
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with a magic value of 0x10B for PE32 or 0x20B for PE32+ (PE32+
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uses 64-bits for some fields). It might also be 0x107 for a ROM
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image, but we don't process that here.
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The optional header ends with a data dictionary that directly
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points to certain types of data, among them the import entries
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(in the second table entry). Based on the header type, we
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determine offsets for the data dictionary count and the entry
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within the dictionary pointing to the imports. */
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opt_offset = pe_offset + 4 + 20;
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opt_magic = WORD_AT(dllbase+opt_offset);
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if (opt_magic == 0x10B) {
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/* PE32 */
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num_dict_off = 92;
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import_off = 104;
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} else if (opt_magic == 0x20B) {
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/* PE32+ */
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num_dict_off = 108;
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import_off = 120;
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} else {
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/* Unsupported */
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return NULL;
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}
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/* Now if an import table exists, offset to it and walk the list of
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imports. The import table is an array (ending when an entry has
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empty values) of structures (20 bytes each), which contains (at
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offset 12) a relative address (to the module base) at which a
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string constant holding the import name is located. */
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if (DWORD_AT(dllbase + opt_offset + num_dict_off) >= 2) {
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import_data = dllbase + DWORD_AT(dllbase +
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opt_offset +
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import_off);
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while (DWORD_AT(import_data)) {
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import_name = dllbase + DWORD_AT(import_data+12);
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if (strlen(import_name) >= 6 &&
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!strncmp(import_name,"python",6)) {
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char *pch;
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/* Ensure python prefix is followed only
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by numbers to the end of the basename */
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pch = import_name + 6;
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while (*pch && *pch != '.') {
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if (*pch >= '0' && *pch <= '9') {
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pch++;
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} else {
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pch = NULL;
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break;
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}
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}
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if (pch) {
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/* Found it - return the name */
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return import_name;
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}
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}
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import_data += 20;
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}
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}
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return NULL;
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}
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#endif /* MS_WIN32 */
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dl_funcptr _PyImport_GetDynLoadFunc(const char *fqname, const char *shortname,
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const char *pathname, FILE *fp)
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{
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dl_funcptr p;
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char funcname[258];
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char funcname[258], *import_python;
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sprintf(funcname, "init%.200s", shortname);
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@@ -91,6 +225,23 @@ dl_funcptr _PyImport_GetDynLoadFunc(const char *fqname, const char *shortname,
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}
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PyErr_SetString(PyExc_ImportError, errBuf);
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return NULL;
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} else {
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char buffer[256];
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sprintf(buffer,"python%d%d.dll",
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PY_MAJOR_VERSION,PY_MINOR_VERSION);
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import_python = GetPythonImport(hDLL);
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if (import_python &&
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strcasecmp(buffer,import_python)) {
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sprintf(buffer,
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"Module use of %s conflicts "
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"with this version of Python.",
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import_python);
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PyErr_SetString(PyExc_ImportError,buffer);
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FreeLibrary(hDLL);
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return NULL;
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}
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}
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p = GetProcAddress(hDLL, funcname);
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}

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