[security] bpo-13617: Reject embedded null characters in wchar* strings. (#2302)

Based on patch by Victor Stinner.

Add private C API function _PyUnicode_AsUnicode() which is similar to
PyUnicode_AsUnicode(), but checks for null characters.

1 files changed, 14 insertions, 0 deletions

diff --git a/Objects/unicodeobject.c b/Objects/unicodeobject.c
index 646de0e..e396d68 100644
--- a/Objects/unicodeobject.c
+++ b/Objects/unicodeobject.c
@@ -4133,6 +4133,20 @@ PyUnicode_AsUnicode(PyObject *unicode)
     return PyUnicode_AsUnicodeAndSize(unicode, NULL);
 }
 
+const Py_UNICODE *
+_PyUnicode_AsUnicode(PyObject *unicode)
+{
+    Py_ssize_t size;
+    const Py_UNICODE *wstr;
+
+    wstr = PyUnicode_AsUnicodeAndSize(unicode, &size);
+    if (wstr && wcslen(wstr) != (size_t)size) {
+        PyErr_SetString(PyExc_ValueError, "embedded null character");
+        return NULL;
+    }
+    return wstr;
+}
+
 
 Py_ssize_t
 PyUnicode_GetSize(PyObject *unicode)