Jim Fulton writes:

I have attached a new cPickle that adds a new control attribute
to unpicklers:

  Added new Unpickler attribute, find_global.  If set to None, then
  global and instance pickles are disabled.  Otherwise, it should be set to
  a callable object that takes two arguments, a module name and an
  object name, and returns an object.  If the attribute is unset, then
  the default mechanism is used.

  This feature provides an additional mechanism for controlling which
  classes can be used for unpickling.

Modules/cPickle.c

 /*
- * cPickle.c,v 1.63 1999/02/05 01:40:06 jim Exp
+ * cPickle.c,v 1.66 1999/04/13 17:23:48 jim Exp
  * 
  * Copyright (c) 1996-1998, Digital Creations, Fredericksburg, VA, USA.  
  * All rights reserved.
@@ -49,7 +49,7 @@
 static char cPickle_module_documentation[] = 
 "C implementation and optimization of the Python pickle module\n"
 "\n"
-"cPickle.c,v 1.63 1999/02/05 01:40:06 jim Exp\n"
+"cPickle.c,v 1.66 1999/04/13 17:23:48 jim Exp\n"
 ;
 
 #include "Python.h"
@@ -345,6 +345,7 @@ typedef struct {
      int buf_size;
      char *buf;
      PyObject *safe_constructors;
+     PyObject *find_class;
 } Unpicklerobject;
  
 staticforward PyTypeObject Unpicklertype;
@@ -2289,9 +2290,18 @@ static PyTypeObject Picklertype = {
 };
 
 static PyObject *
-find_class(PyObject *py_module_name, PyObject *py_global_name) {
+find_class(PyObject *py_module_name, PyObject *py_global_name, PyObject *fc) {
     PyObject *global = 0, *module;
 
+    if (fc) {
+      if (fc==Py_None) {
+	PyErr_SetString(UnpicklingError, 
+			"Global and instance pickles are not supported.");
+	return NULL;
+      }
+      return PyObject_CallFunction(fc, "OO", py_module_name, py_global_name);
+    }
+
     module = PySys_GetObject("modules");
     if (module == NULL)
       return NULL;
@@ -2842,7 +2852,7 @@ load_inst(Unpicklerobject *self) {
     if ((len = (*self->readline_func)(self, &s)) >= 0) {
         if (len < 2) return bad_readline();
         if (class_name = PyString_FromStringAndSize(s, len - 1)) {
-            class = find_class(module_name, class_name);
+            class = find_class(module_name, class_name, self->find_class);
             Py_DECREF(class_name);
         }
     }
@@ -2876,7 +2886,7 @@ load_global(Unpicklerobject *self) {
     if ((len = (*self->readline_func)(self, &s)) >= 0) {
         if (len < 2) return bad_readline();
         if (class_name = PyString_FromStringAndSize(s, len - 1)) {
-            class = find_class(module_name, class_name);
+            class = find_class(module_name, class_name, self->find_class);
             Py_DECREF(class_name);
         }
     }
@@ -3889,6 +3899,7 @@ newUnpicklerobject(PyObject *f) {
     self->read = NULL;
     self->readline = NULL;
     self->safe_constructors = NULL;
+    self->find_class = NULL;
 
     UNLESS (self->memo = PyDict_New()) {
        Py_XDECREF((PyObject *)self);
@@ -3996,6 +4007,16 @@ Unpickler_getattr(Unpicklerobject *self, char *name) {
         return self->pers_func;
     }
 
+    if (!strcmp(name, "find_global")) {
+        if (!self->find_class) {
+            PyErr_SetString(PyExc_AttributeError, name);
+            return NULL;
+        }
+
+        Py_INCREF(self->find_class);
+        return self->find_class;
+    }
+
     if (!strcmp(name, "memo")) {
         if (!self->memo) {
             PyErr_SetString(PyExc_AttributeError, name);
@@ -4018,19 +4039,26 @@ Unpickler_getattr(Unpicklerobject *self, char *name) {
 static int
 Unpickler_setattr(Unpicklerobject *self, char *name, PyObject *value) {
 
-    if (! value) {
-        PyErr_SetString(PyExc_TypeError,
-                        "attribute deletion is not supported");
-        return -1;
-    }
-
     if (!strcmp(name, "persistent_load")) {
         Py_XDECREF(self->pers_func);
         self->pers_func = value;
-        Py_INCREF(value);
+        Py_XINCREF(value);
+        return 0;
+    }
+
+    if (!strcmp(name, "find_global")) {
+        Py_XDECREF(self->find_class);
+        self->find_class = value;
+        Py_XINCREF(value);
         return 0;
     }
 
+    if (! value) {
+        PyErr_SetString(PyExc_TypeError,
+                        "attribute deletion is not supported");
+        return -1;
+    }
+
     if (strcmp(name, "memo") == 0) {
         if (! PyDict_Check(value)) {
           PyErr_SetString(PyExc_TypeError, "memo must be a dictionary");
@@ -4305,7 +4333,7 @@ init_stuff(PyObject *module, PyObject *module_dict) {
 DL_EXPORT(void)
 initcPickle() {
     PyObject *m, *d, *v;
-    char *rev="1.63";
+    char *rev="1.66";
     PyObject *format_version;
     PyObject *compatible_formats;