[Zope-Coders] Hidden Attribute Error

[Shane Hathaway]

Christian Theune wrote:
> Hi.
> 
> This costed me a lot of time to debug. I had an AttributeError which was
> within the security/authorization machinery.
> 
> It was hidden by the reraise (with Unauthorized) here:
> 
> lib/python/AccessControl/ZopeGuards.py line 61-64
> 
> I propose to only raise it as Unauthorized if in Production mode. Debug
> mode shouldn't hide those kinds of errors.
> 
> If you are fine with that, I can give a fix for that.

Ow, that would hurt. :-(

You're talking about the Zope HEAD, right?  This code is different on 
the 2_6 branch.

Here's the problem: ZopeSecurityPolicy doesn't always raise Unauthorized 
when it should.  Sometimes it simply returns "false".  This leads to 
Acquisition.c raising an AttributeError.  In guarded_getattr(), that 
situation is unacceptable: the system needs to see Unauthorized in order 
to prompt the user for credentials.  So guarded_getattr() converts the 
AttributeError to the Unauthorized that it should have been.

This has been a major source of bugs.  I think ZopeSecurityPolicy needs 
to be fixed so that we don't have to convert exceptions.  I think it 
should always raise Unauthorized when the user is denied access to 
something.  The change is quite simple, but it will probably expose bugs 
in Zope and/or products (we'll get more Unauthorized errors than we used 
to).  What do you think?

Shane