bpo-38622: Add missing audit events for ctypes module (GH-17158)

(cherry picked from commit 00923c6)

Co-authored-by: Steve Dower <[email protected]>

Author: miss-islington

Doc/library/ctypes.rst

@@ -1526,6 +1526,12 @@ object is available:
    ``ctypes.dlsym`` with arguments ``library`` (the library object) and ``name``
    (the symbol's name as a string or integer).
 
+.. audit-event:: ctypes.dlsym/handle handle,name ctypes.LibraryLoader
+
+   In cases when only the library handle is available rather than the object,
+   accessing a function raises an auditing event ``ctypes.dlsym/handle`` with
+   arguments ``handle`` (the raw library handle) and ``name``.
+
 .. _ctypes-foreign-functions:
 
 Foreign functions
@@ -1611,6 +1617,19 @@ They are instances of a private class:
    passed arguments.
 
 
+.. audit-event:: ctypes.seh_exception code foreign-functions
+
+   On Windows, when a foreign function call raises a system exception (for
+   example, due to an access violation), it will be captured and replaced with
+   a suitable Python exception. Further, an auditing event
+   ``ctypes.seh_exception`` with argument ``code`` will be raised, allowing an
+   audit hook to replace the exception with its own.
+
+.. audit-event:: ctypes.call_function func_pointer,arguments ctype-foreign-functions
+
+   Some ways to invoke foreign function calls may raise an auditing event
+   ``ctypes.call_function`` with arguments ``function pointer`` and ``arguments``.
+
 .. _ctypes-function-prototypes:
 
 Function prototypes
@@ -1802,6 +1821,8 @@ Utility functions
    Returns the address of the memory buffer as integer.  *obj* must be an
    instance of a ctypes type.
 
+   .. audit-event:: ctypes.addressof obj ctypes.addressof
+
 
 .. function:: alignment(obj_or_type)
 
@@ -1844,6 +1865,7 @@ Utility functions
    termination character. An integer can be passed as second argument which allows
    specifying the size of the array if the length of the bytes should not be used.
 
+   .. audit-event:: ctypes.create_string_buffer init,size ctypes.create_string_buffer
 
 
 .. function:: create_unicode_buffer(init_or_size, size=None)
@@ -1860,6 +1882,7 @@ Utility functions
    allows specifying the size of the array if the length of the string should not
    be used.
 
+   .. audit-event:: ctypes.create_unicode_buffer init,size ctypes.create_unicode_buffer
 
 
 .. function:: DllCanUnloadNow()
@@ -1917,11 +1940,15 @@ Utility functions
    Returns the current value of the ctypes-private copy of the system
    :data:`errno` variable in the calling thread.
 
+   .. audit-event:: ctypes.get_errno "" ctypes.get_errno
+
 .. function:: get_last_error()
 
    Windows only: returns the current value of the ctypes-private copy of the system
    :data:`LastError` variable in the calling thread.
 
+   .. audit-event:: ctypes.get_last_error "" ctypes.get_last_error
+
 .. function:: memmove(dst, src, count)
 
    Same as the standard C memmove library function: copies *count* bytes from
@@ -1965,6 +1992,7 @@ Utility functions
    Set the current value of the ctypes-private copy of the system :data:`errno`
    variable in the calling thread to *value* and return the previous value.
 
+   .. audit-event:: ctypes.set_errno errno ctypes.set_errno
 
 
 .. function:: set_last_error(value)
@@ -1973,6 +2001,7 @@ Utility functions
    :data:`LastError` variable in the calling thread to *value* and return the
    previous value.
 
+   .. audit-event:: ctypes.set_last_error error ctypes.set_last_error
 
 
 .. function:: sizeof(obj_or_type)
@@ -1987,6 +2016,8 @@ Utility functions
    object. If size is specified, it is used as size, otherwise the string is assumed
    to be zero-terminated.
 
+   .. audit-event:: ctypes.string_at address,size ctypes.string_at
+
 
 .. function:: WinError(code=None, descr=None)
 
@@ -2007,6 +2038,8 @@ Utility functions
    characters of the string, otherwise the string is assumed to be
    zero-terminated.
 
+   .. audit-event:: ctypes.wstring_at address,size ctypes.wstring_at
+
 
 .. _ctypes-data-types:
 
@@ -2034,6 +2067,7 @@ Data types
       source buffer in bytes; the default is zero.  If the source buffer is not
       large enough a :exc:`ValueError` is raised.
 
+      .. audit-event:: ctypes.cdata/buffer pointer,size,offset ctypes._CData.from_buffer
 
    .. method:: _CData.from_buffer_copy(source[, offset])
 
@@ -2043,6 +2077,8 @@ Data types
       is zero.  If the source buffer is not large enough a :exc:`ValueError` is
       raised.
 
+      .. audit-event:: ctypes.cdata/buffer pointer,size,offset ctypes._CData.from_buffer_copy
+
    .. method:: from_address(address)
 
       This method returns a ctypes type instance using the memory specified by

Lib/ctypes/__init__.py

@@ -52,11 +52,13 @@ def create_string_buffer(init, size=None):
     if isinstance(init, bytes):
         if size is None:
             size = len(init)+1
+        _sys.audit("ctypes.create_string_buffer", init, size)
         buftype = c_char * size
         buf = buftype()
         buf.value = init
         return buf
     elif isinstance(init, int):
+        _sys.audit("ctypes.create_string_buffer", None, init)
         buftype = c_char * init
         buf = buftype()
         return buf
@@ -283,11 +285,13 @@ def create_unicode_buffer(init, size=None):
                 # 32-bit wchar_t (1 wchar_t per Unicode character). +1 for
                 # trailing NUL character.
                 size = len(init) + 1
+        _sys.audit("ctypes.create_unicode_buffer", init, size)
         buftype = c_wchar * size
         buf = buftype()
         buf.value = init
         return buf
     elif isinstance(init, int):
+        _sys.audit("ctypes.create_unicode_buffer", None, init)
         buftype = c_wchar * init
         buf = buftype()
         return buf

Misc/NEWS.d/next/Security/2019-11-14-16-13-23.bpo-38622.3DYkfb.rst

@@ -0,0 +1 @@
+Add additional audit events for the :mod:`ctypes` module.

Modules/_ctypes/_ctypes.c

@@ -641,6 +641,12 @@ CDataType_from_buffer(PyObject *type, PyObject *args)
         return NULL;
     }
 
+    if (PySys_Audit("ctypes.cdata/buffer", "nnn",
+                    (Py_ssize_t)buffer->buf, buffer->len, offset) < 0) {
+        Py_DECREF(mv);
+        return NULL;
+    }
+
     result = PyCData_AtAddress(type, (char *)buffer->buf + offset);
     if (result == NULL) {
         Py_DECREF(mv);
@@ -691,6 +697,12 @@ CDataType_from_buffer_copy(PyObject *type, PyObject *args)
         return NULL;
     }
 
+    if (PySys_Audit("ctypes.cdata/buffer", "nnn",
+                    (Py_ssize_t)buffer.buf, buffer.len, offset) < 0) {
+        PyBuffer_Release(&buffer);
+        return NULL;
+    }
+
     result = GenericPyCData_new((PyTypeObject *)type, NULL, NULL);
     if (result != NULL) {
         memcpy(((CDataObject *)result)->b_ptr,
@@ -714,6 +726,9 @@ CDataType_in_dll(PyObject *type, PyObject *args)
 
     if (!PyArg_ParseTuple(args, "Os:in_dll", &dll, &name))
         return NULL;
+    if (PySys_Audit("ctypes.dlsym", "O", args) < 0) {
+        return NULL;
+    }
 
     obj = PyObject_GetAttrString(dll, "_handle");
     if (!obj)
@@ -5534,6 +5549,9 @@ create_comerror(void)
 static PyObject *
 string_at(const char *ptr, int size)
 {
+    if (PySys_Audit("ctypes.string_at", "ni", (Py_ssize_t)ptr, size) < 0) {
+        return NULL;
+    }
     if (size == -1)
         return PyBytes_FromStringAndSize(ptr, strlen(ptr));
     return PyBytes_FromStringAndSize(ptr, size);
@@ -5625,6 +5643,9 @@ static PyObject *
 wstring_at(const wchar_t *ptr, int size)
 {
     Py_ssize_t ssize = size;
+    if (PySys_Audit("ctypes.wstring_at", "nn", (Py_ssize_t)ptr, ssize) < 0) {
+        return NULL;
+    }
     if (ssize == -1)
         ssize = wcslen(ptr);
     return PyUnicode_FromWideChar(ptr, ssize);

Modules/_ctypes/callproc.c

@@ -199,8 +199,9 @@ set_error_internal(PyObject *self, PyObject *args, int index)
     PyObject *errobj;
     int *space;
 
-    if (!PyArg_ParseTuple(args, "i", &new_errno))
+    if (!PyArg_ParseTuple(args, "i", &new_errno)) {
         return NULL;
+    }
     errobj = _ctypes_get_errobj(&space);
     if (errobj == NULL)
         return NULL;
@@ -213,12 +214,18 @@ set_error_internal(PyObject *self, PyObject *args, int index)
 static PyObject *
 get_errno(PyObject *self, PyObject *args)
 {
+    if (PySys_Audit("ctypes.get_errno", NULL) < 0) {
+        return NULL;
+    }
     return get_error_internal(self, args, 0);
 }
 
 static PyObject *
 set_errno(PyObject *self, PyObject *args)
 {
+    if (PySys_Audit("ctypes.set_errno", "O", args) < 0) {
+        return NULL;
+    }
     return set_error_internal(self, args, 0);
 }
 
@@ -227,12 +234,18 @@ set_errno(PyObject *self, PyObject *args)
 static PyObject *
 get_last_error(PyObject *self, PyObject *args)
 {
+    if (PySys_Audit("ctypes.get_last_error", NULL) < 0) {
+        return NULL;
+    }
     return get_error_internal(self, args, 1);
 }
 
 static PyObject *
 set_last_error(PyObject *self, PyObject *args)
 {
+    if (PySys_Audit("ctypes.set_last_error", "O", args) < 0) {
+        return NULL;
+    }
     return set_error_internal(self, args, 1);
 }
 
@@ -262,6 +275,11 @@ static WCHAR *FormatError(DWORD code)
 #ifndef DONT_USE_SEH
 static void SetException(DWORD code, EXCEPTION_RECORD *pr)
 {
+    if (PySys_Audit("ctypes.seh_exception", "I", code) < 0) {
+        /* An exception was set by the audit hook */
+        return;
+    }
+
     /* The 'code' is a normal win32 error code so it could be handled by
     PyErr_SetFromWindowsErr(). However, for some errors, we have additional
     information not included in the error code. We handle those here and
@@ -1427,6 +1445,9 @@ static PyObject *py_dl_sym(PyObject *self, PyObject *args)
     if (!PyArg_ParseTuple(args, "O&s:dlsym",
                           &_parse_voidp, &handle, &name))
         return NULL;
+    if (PySys_Audit("ctypes.dlsym/handle", "O", args) < 0) {
+        return NULL;
+    }
     ptr = ctypes_dlsym((void*)handle, name);
     if (!ptr) {
         PyErr_SetString(PyExc_OSError,
@@ -1454,6 +1475,10 @@ call_function(PyObject *self, PyObject *args)
                           &_parse_voidp, &func,
                           &PyTuple_Type, &arguments))
         return NULL;
+    if (PySys_Audit("ctypes.call_function", "nO",
+                    (Py_ssize_t)func, arguments) < 0) {
+        return NULL;
+    }
 
     result =  _ctypes_callproc((PPROC)func,
                         arguments,
@@ -1485,6 +1510,10 @@ call_cdeclfunction(PyObject *self, PyObject *args)
                           &_parse_voidp, &func,
                           &PyTuple_Type, &arguments))
         return NULL;
+    if (PySys_Audit("ctypes.call_function", "nO",
+                    (Py_ssize_t)func, arguments) < 0) {
+        return NULL;
+    }
 
     result =  _ctypes_callproc((PPROC)func,
                         arguments,
@@ -1597,11 +1626,15 @@ static const char addressof_doc[] =
 static PyObject *
 addressof(PyObject *self, PyObject *obj)
 {
-    if (CDataObject_Check(obj))
-        return PyLong_FromVoidPtr(((CDataObject *)obj)->b_ptr);
-    PyErr_SetString(PyExc_TypeError,
-                    "invalid type");
-    return NULL;
+    if (!CDataObject_Check(obj)) {
+        PyErr_SetString(PyExc_TypeError,
+                        "invalid type");
+        return NULL;
+    }
+    if (PySys_Audit("ctypes.addressof", "O", obj) < 0) {
+        return NULL;
+    }
+    return PyLong_FromVoidPtr(((CDataObject *)obj)->b_ptr);
 }
 
 static int
@@ -1615,8 +1648,12 @@ static PyObject *
 My_PyObj_FromPtr(PyObject *self, PyObject *args)
 {
     PyObject *ob;
-    if (!PyArg_ParseTuple(args, "O&:PyObj_FromPtr", converter, &ob))
+    if (!PyArg_ParseTuple(args, "O&:PyObj_FromPtr", converter, &ob)) {
         return NULL;
+    }
+    if (PySys_Audit("ctypes.PyObj_FromPtr", "O", ob) < 0) {
+        return NULL;
+    }
     Py_INCREF(ob);
     return ob;
 }