bpo-29778: Ensure python3.dll is loaded from correct locations when Python is embedded (GH-21297)

Also enables using debug build of `python3_d.dll`
Reference: CVE-2020-15523
(cherry picked from commit dcbaa1b49cd9062fb9ba2b9d49555ac6cd8c60b5)

Co-authored-by: Steve Dower <steve.dower@python.org>

1 files changed, 44 insertions, 1 deletions

diff --git a/Modules/_testinternalcapi.c b/Modules/_testinternalcapi.c
index 8faa9fe..4445d2e 100644
--- a/Modules/_testinternalcapi.c
+++ b/Modules/_testinternalcapi.c
@@ -18,10 +18,53 @@
 #include "pycore_gc.h"           // PyGC_Head
 
 
+#ifdef MS_WINDOWS
+#include <windows.h>
+
+static int
+_add_windows_config(PyObject *configs)
+{
+    HMODULE hPython3;
+    wchar_t py3path[MAX_PATH];
+    PyObject *dict = PyDict_New();
+    PyObject *obj = NULL;
+    if (!dict) {
+        return -1;
+    }
+
+    hPython3 = GetModuleHandleW(PY3_DLLNAME);
+    if (hPython3 && GetModuleFileNameW(hPython3, py3path, MAX_PATH)) {
+        obj = PyUnicode_FromWideChar(py3path, -1);
+    } else {
+        obj = Py_None;
+        Py_INCREF(obj);
+    }
+    if (obj &&
+        !PyDict_SetItemString(dict, "python3_dll", obj) &&
+        !PyDict_SetItemString(configs, "windows", dict)) {
+        Py_DECREF(obj);
+        Py_DECREF(dict);
+        return 0;
+    }
+    Py_DECREF(obj);
+    Py_DECREF(dict);
+    return -1;
+}
+#endif
+
+
 static PyObject *
 get_configs(PyObject *self, PyObject *Py_UNUSED(args))
 {
-    return _Py_GetConfigsAsDict();
+    PyObject *dict = _Py_GetConfigsAsDict();
+#ifdef MS_WINDOWS
+    if (dict) {
+        if (_add_windows_config(dict) < 0) {
+            Py_CLEAR(dict);
+        }
+    }
+#endif
+    return dict;
 }