Hi, > I know all this -- but its not relevant really, I think. I'm not trying > to create a safe yet relatively complete or functional Python. All those > efforts to sandbox Python fail because of the incredible dynamic nature > of the language has lots of enticing little holes in it. But I'm not > interested in a full or even vaguely full subset of Python, and I'm not > requiring that this security be done on the code-level. I had the same problem, and so I created a "pseudo-sandbox" for embedding Python in templates. This "pseudo-sandbox" creates a restricted Python environment, where only whitelisted functions/classes are allowed. Additionally, it prevents things like '0 .__class__'.
You can find some documentation at http://simple-is-better.org/template/pyratemp.html#evaluation, and the pseudo-sandbox itself in my template-engine, class "EvalPseudoSandbox" on the website above. (Please write me if you have any comments.) But note that this is not a real sandbox! As soon as you allow *any* unsafe function (e.g. open, import, eval, getattr etc.), you can easily break out. Also, don't directly pass complete modules to the pseudo-sandbox, since they may contain unsafe functions/classes/etc. And be warned: There *may* also be ways to break out of the pseudo-sandbox even without passing unsafe functions to it -- although I don't know any. If you know or find such a way: Please tell me! You could also take a look at Jinja (which is also a template-engine), and which claims to include a sandbox. But the Jinja-sandbox seems to be much more complicated than my pseudo-sandbox, and I haven't analyzed it and don't know how it works. > For example, when you go to save your bit of code, it will go in and if > it finds __ anywhere in the text it just replaces it with xx. And, since > getattr is not available, '_' + '_' won't get you anywhere. I don't think that searching the text is the right way; in my pseudo-sandbox, I compile the code and search co_names for such names instead. > I just need a certain limited context where someone can be handed > certain Python objects and manipulate them. I'd like people to be able > to use some fundamental Python power -- the rich, beautiful data types > for example (notably in this case, strings), list comprehensions and > stuff, to do what they need to do. Python's very easy, I'd like them to > be able to use that easy. I was in the exact same position ;). (Although I don't have fully untrusted/bad users, and so my pseudo-sandbox is sufficient for my cases, even though I haven't proved that it really is secure...) regards, Roland -- http://mail.python.org/mailman/listinfo/python-list
