Jim Fulton wrote:
> The problem is that it it starts with an environment in which things  
> are allowed by default, and takes things away. This means that if  
> anything is forgotten, then you end up with holes.

Isn't there a way we could change the AST manipulation such that we 
start with nothing and only allow opcodes as and when they're added to 
the RestrictedPython implementation?

> The Zope 3 security proxy approach is much better 

I agree, but it doesn't solve all the problems. My understanding of the 
original set of requirements which we're trying to solve here was 
basically that of Python Scripts: to allow python code to be written 
through the web. This means:

- restricting access to atributes of objects
   (security proxies give us this, right?)

- restricting access to features of the language such as imports such
   that unsafe things such as stripping security proxies can't be done.
   (security proxies *don't* give us this, right?)

...and some nice to haves:

- restricting memory used by executing the code
- restricting cpu used by executing the code

I know RestrictedPython doesn't support these last two very well, but 
there are hints that it would have liked to if it could.

> to do code manipulation. It still uses restricted Python do deal in a  
> narrow way with basic objects, like strings and numbers, that are  
> unproxied. It's use of restricted Python is so narrow that it is far  
> less problematic. It would be really great if Zope 2 would switch to  
> security proxies, although the transition is likely to be painful.

How would you see the problem of the second requirement above being met?

> I'm not sure that the PyPy guys are really authorities on the sorts of  
> problems we're trying to address, although there is some overlap. 

Who is then? ;-)

> If  
> I remember correctly, they are just focussed on protecting the system  
> from untrusted scripts.  Our problem is harder because we also want to  
> protect objects available to the scripts.

Indeed :-(


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