bpo-28129: fix ctypes crashes (#386)

* init commit, with initial tests for from_param and fields __set__ and __get__, and some additions to from_buffer and from_buffer_copy

* added the rest of tests and patches. probably only a first draft.

* removed trailing spaces

* replace ctype with ctypes in error messages

* change back from ctypes instance to ctype instance

Author: orenmn

Lib/ctypes/test/test_frombuffer.py

@@ -121,12 +121,21 @@ def test_from_buffer_copy_with_offset(self):
             (c_int * 1).from_buffer_copy(a, 16 * sizeof(c_int))
 
     def test_abstract(self):
+        from ctypes import _Pointer, _SimpleCData, _CFuncPtr
+
         self.assertRaises(TypeError, Array.from_buffer, bytearray(10))
         self.assertRaises(TypeError, Structure.from_buffer, bytearray(10))
         self.assertRaises(TypeError, Union.from_buffer, bytearray(10))
+        self.assertRaises(TypeError, _CFuncPtr.from_buffer, bytearray(10))
+        self.assertRaises(TypeError, _Pointer.from_buffer, bytearray(10))
+        self.assertRaises(TypeError, _SimpleCData.from_buffer, bytearray(10))
+
         self.assertRaises(TypeError, Array.from_buffer_copy, b"123")
         self.assertRaises(TypeError, Structure.from_buffer_copy, b"123")
         self.assertRaises(TypeError, Union.from_buffer_copy, b"123")
+        self.assertRaises(TypeError, _CFuncPtr.from_buffer_copy, b"123")
+        self.assertRaises(TypeError, _Pointer.from_buffer_copy, b"123")
+        self.assertRaises(TypeError, _SimpleCData.from_buffer_copy, b"123")
 
 if __name__ == '__main__':
     unittest.main()

Lib/ctypes/test/test_funcptr.py

@@ -123,5 +123,10 @@ def c_string(init):
         self.assertEqual(strtok(None, b"\n"), b"c")
         self.assertEqual(strtok(None, b"\n"), None)
 
+    def test_abstract(self):
+        from ctypes import _CFuncPtr
+
+        self.assertRaises(TypeError, _CFuncPtr, 13, "name", 42, "iid")
+
 if __name__ == '__main__':
     unittest.main()

Lib/ctypes/test/test_parameters.py

@@ -169,6 +169,16 @@ def from_param(cls, obj):
         # ArgumentError: argument 1: ValueError: 99
         self.assertRaises(ArgumentError, func, 99)
 
+    def test_abstract(self):
+        from ctypes import (Array, Structure, Union, _Pointer,
+                            _SimpleCData, _CFuncPtr)
+
+        self.assertRaises(TypeError, Array.from_param, 42)
+        self.assertRaises(TypeError, Structure.from_param, 42)
+        self.assertRaises(TypeError, Union.from_param, 42)
+        self.assertRaises(TypeError, _CFuncPtr.from_param, 42)
+        self.assertRaises(TypeError, _Pointer.from_param, 42)
+        self.assertRaises(TypeError, _SimpleCData.from_param, 42)
 
 ################################################################
 

Lib/ctypes/test/test_pointers.py

@@ -213,6 +213,11 @@ def test_pointer_type_str_name(self):
         from ctypes import _pointer_type_cache
         del _pointer_type_cache[id(P)]
 
+    def test_abstract(self):
+        from ctypes import _Pointer
+
+        self.assertRaises(TypeError, _Pointer.set_type, 42)
+
 
 if __name__ == '__main__':
     unittest.main()

Lib/ctypes/test/test_struct_fields.py

@@ -46,5 +46,29 @@ class Y(X):
         Y._fields_ = []
         self.assertRaises(AttributeError, setattr, X, "_fields_", [])
 
+    # __set__ and __get__ should raise a TypeError in case their self
+    # argument is not a ctype instance.
+    def test___set__(self):
+        class MyCStruct(Structure):
+            _fields_ = (("field", c_int),)
+        self.assertRaises(TypeError,
+                          MyCStruct.field.__set__, 'wrong type self', 42)
+
+        class MyCUnion(Union):
+            _fields_ = (("field", c_int),)
+        self.assertRaises(TypeError,
+                          MyCUnion.field.__set__, 'wrong type self', 42)
+
+    def test___get__(self):
+        class MyCStruct(Structure):
+            _fields_ = (("field", c_int),)
+        self.assertRaises(TypeError,
+                          MyCStruct.field.__get__, 'wrong type self', 42)
+
+        class MyCUnion(Union):
+            _fields_ = (("field", c_int),)
+        self.assertRaises(TypeError,
+                          MyCUnion.field.__get__, 'wrong type self', 42)
+
 if __name__ == "__main__":
     unittest.main()

Modules/_ctypes/_ctypes.c

@@ -924,6 +924,7 @@ PyCPointerType_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
     if (proto) {
         StgDictObject *itemdict = PyType_stgdict(proto);
         const char *current_format;
+        /* PyCPointerType_SetProto has verified proto has a stgdict. */
         assert(itemdict);
         /* If itemdict->format is NULL, then this is a pointer to an
            incomplete type.  We create a generic format string
@@ -970,7 +971,11 @@ PyCPointerType_set_type(PyTypeObject *self, PyObject *type)
     StgDictObject *dict;
 
     dict = PyType_stgdict((PyObject *)self);
-    assert(dict);
+    if (!dict) {
+        PyErr_SetString(PyExc_TypeError,
+                        "abstract class");
+        return NULL;
+    }
 
     if (-1 == PyCPointerType_SetProto(dict, type))
         return NULL;
@@ -995,7 +1000,11 @@ PyCPointerType_from_param(PyObject *type, PyObject *value)
     }
 
     typedict = PyType_stgdict(type);
-    assert(typedict); /* Cannot be NULL for pointer types */
+    if (!typedict) {
+        PyErr_SetString(PyExc_TypeError,
+                        "abstract class");
+        return NULL;
+    }
 
     /* If we expect POINTER(<type>), but receive a <type> instance, accept
        it by calling byref(<type>).
@@ -2057,7 +2066,11 @@ PyCSimpleType_from_param(PyObject *type, PyObject *value)
     }
 
     dict = PyType_stgdict(type);
-    assert(dict);
+    if (!dict) {
+        PyErr_SetString(PyExc_TypeError,
+                        "abstract class");
+        return NULL;
+    }
 
     /* I think we can rely on this being a one-character string */
     fmt = PyUnicode_AsUTF8(dict->proto);
@@ -3146,7 +3159,11 @@ _validate_paramflags(PyTypeObject *type, PyObject *paramflags)
     PyObject *argtypes;
 
     dict = PyType_stgdict((PyObject *)type);
-    assert(dict); /* Cannot be NULL. 'type' is a PyCFuncPtr type. */
+    if (!dict) {
+        PyErr_SetString(PyExc_TypeError,
+                        "abstract class");
+        return 0;
+    }
     argtypes = dict->argtypes;
 
     if (paramflags == NULL || dict->argtypes == NULL)
@@ -4779,7 +4796,7 @@ Pointer_ass_item(PyObject *myself, Py_ssize_t index, PyObject *value)
     }
 
     stgdict = PyObject_stgdict((PyObject *)self);
-    assert(stgdict); /* Cannot be NULL fr pointer instances */
+    assert(stgdict); /* Cannot be NULL for pointer instances */
 
     proto = stgdict->proto;
     assert(proto);
@@ -4807,7 +4824,7 @@ Pointer_get_contents(CDataObject *self, void *closure)
     }
 
     stgdict = PyObject_stgdict((PyObject *)self);
-    assert(stgdict); /* Cannot be NULL fr pointer instances */
+    assert(stgdict); /* Cannot be NULL for pointer instances */
     return PyCData_FromBaseObj(stgdict->proto,
                              (PyObject *)self, 0,
                              *(void **)self->b_ptr);
@@ -4826,7 +4843,7 @@ Pointer_set_contents(CDataObject *self, PyObject *value, void *closure)
         return -1;
     }
     stgdict = PyObject_stgdict((PyObject *)self);
-    assert(stgdict); /* Cannot be NULL fr pointer instances */
+    assert(stgdict); /* Cannot be NULL for pointer instances */
     assert(stgdict->proto);
     if (!CDataObject_Check(value)) {
         int res = PyObject_IsInstance(value, stgdict->proto);

Modules/_ctypes/cfield.c

@@ -205,7 +205,11 @@ PyCField_set(CFieldObject *self, PyObject *inst, PyObject *value)
 {
     CDataObject *dst;
     char *ptr;
-    assert(CDataObject_Check(inst));
+    if (!CDataObject_Check(inst)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "not a ctype instance");
+        return -1;
+    }
     dst = (CDataObject *)inst;
     ptr = dst->b_ptr + self->offset;
     if (value == NULL) {
@@ -225,7 +229,11 @@ PyCField_get(CFieldObject *self, PyObject *inst, PyTypeObject *type)
         Py_INCREF(self);
         return (PyObject *)self;
     }
-    assert(CDataObject_Check(inst));
+    if (!CDataObject_Check(inst)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "not a ctype instance");
+        return NULL;
+    }
     src = (CDataObject *)inst;
     return PyCData_get(self->proto, self->getfunc, inst,
                      self->index, self->size, src->b_ptr + self->offset);