[Zope-dev] Ambiguities in "Inheritance and Class Security Declaration"

[Chris McDonough]

Ross Boylan wrote:
> After reading this section of the development guide, I have a lot of
> questions (pp 75-76 of the guide).
> 
> 1. If a subclass redefines a base class method, does the subclass need
> to do a security declaration on it?  The document says "You only need
> to make security declarations for methods .... your class actually
> defines.  If your class inherits from other classes, the methods of
> the base classes are protected by the security declarations made in
> the base classes."  The first sentence seems to indicate a security
> declaration is necessary (since you define the method); the second
> sentence suggests its not.  It depends partly on the meaning of
> "define" and also "method" (that is, is redefinition considered
> definition?  does method refer to a name or to a specific classes
> implementation of that name?).

You should have security declarations for each method you define, even 
if they are defined in the base class.


> 
> 2. Does a subclass need to have
>    security = ClassSecurityInfo()
> in it if the base class does?  Judging from the example, yes.
> 

Yes.

> 3. Under what circumstances is the declaration in 2 necessary?  For
> example, only if new method names are introduced and protected?  Or
> any reference to security in the subclass?  It seems the latter, from
> the example.

Define security assertions for all the methods you define.

> 
> 4. Suppose we wanted to change the security of a base class method
> without otherwise redefining it.  What's necessary then?

Define a security declaration for a method without actually defining the 
method.  Your security declaration will override those of the base class.

> 
> 5. Under what conditions is InitializeClass necessary for the subclass
> when the base class has been through InitializeClass?  (The guide only
> addresses the case when the base class has not been so processed.  It
> also says the declarations "filter down", but the implication of this
> for new method is unclear.)

When you define new methods or when you want to override security 
declarations in the base class.  It never hurts to run a class through 
InitializeClass.

> 
> This section has a lot of explicit discussion of odd cases (no
> security in superclass, redefining permissions on existing methods
> without changing them) and not enough about the normal cases (my
> subclass extends some base class methods and defines some new ones).
> 
> Also, the second paragraph uses "superclass" where I hope it means
> subclass. 

These comments would be more helpful if they were made using the comment 
system that is in the book itself.  I will unfortunately forget about 
this maillist message in about 10 minutes, but if they were made inline, 
when I went to go edit the book, there they'd be. ;-)

> Although I would appreciate and responses from the list, I would also
> like to send these comments to the documents authors.  Unfortunately,
> I see no authorship or contact information in the document.  Can
> anyone suggest some?

I wrote most of it.  You can ask, I may be able to answer. ;-)

-- 
Chris McDonough                    Zope Corporation
http://www.zope.org             http://www.zope.com
"Killing hundreds of birds with thousands of stones"