Embedded Python and Restricted Execution

[cgfandrich at my-deja.com]

I'm embedding Python in an application and I'd like to be able to run
Python code (including callable PyObjects) in a restricted environment -
 much like rexec - but I'd like to control the environment in C/C++.
I've tried the following and had some success:

1. Create a new module.
2. Add a "__builtins__" dictionary to the module.
3. Copy references from existing "__builtins__" to new "__builtins__"
(except for "__import__" and "open" - use my functions for those 2)
4. Use the new "__builtins__" dictionary whenever I want to run code in
restricted environment.

When importing modules, I've also had to make sure that the module
being imported gets the correct "__builtins__" dictionary.  The only
problem is ... if I have 2 modules "test1" and "test2" that use the
same Python source code, I can't run them in the different
environments.  It seems like they both run with
whichever "__builtins__" was used to import the first module.

Any ideas?  Should I be doing this differently?

-chris
//====================================================================
static PyMethodDef restricted_methods[] =
{
    {"__import__", restricted___import__, 1},
    {"open", restricted_open, 1},
    {NULL,NULL}
};

void InitRestricted()
{
    PyObject *SecureModule;
    SecureModule = PyImport_AddModule("__restricted__");
    PyObject *SecureDictionary = PyModule_GetDict(SecureModule);
    PyObject *SecureBuiltins=PyDict_New();
    PyDict_SetItemString
(SecureDictionary,"__builtins__",SecureBuiltins);

    PyObject *MainBuiltins = PyEval_GetBuiltins();

    if(MainBuiltins && SecureBuiltins)
    {
        PyObject *MainKeys = PyDict_Keys(MainBuiltins);
        int i;
        // __import__
        value = PyCFunction_New(&restricted_methods[0], NULL);
        if (value != NULL)
            PyDict_SetItemString(SecureBuiltins, "__import__", value);
        Py_DECREF(value);
        // open
        value = PyCFunction_New(&restricted_methods[1], NULL);
        if (value != NULL)
            PyDict_SetItemString(SecureBuiltins, "open", value);
        Py_DECREF(value);
        for(i=0;i<PyList_Size(MainKeys);i++)
        {
            PyObject *key = PyList_GetItem(MainKeys,i);
            char *keyname=PyString_AsString(key);
            PyObject *value = PyDict_GetItemString
(MainBuiltins,keyname);
            if((strcmpi(keyname,"__import__")!=0) && (strcmpi
(keyname,"open")!=0))
                PyDict_SetItemString(SecureBuiltins,keyname,value);
        }
    }
}

void RunScript(char *Script,const BOOL Secure,PyObject *RetObject)
{
    PyObject *module;
    PyObject *dict;
    if(Secure)
        module = PyImport_AddModule("__restricted__");
    else
        module = PyImport_AddModule("__main__");
    dict = PyModule_GetDict(module);
    RetObject = PyRun_String(Script,Py_eval_input,dict,dict);
}



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