From: Patrick May <patrick@...>
Date: 2004-06-28T08:53:39+09:00
Subject: Re: Is it considered Harmful?


On Sunday, June 27, 2004, at 07:08  PM, Sean O'Dell wrote:

> Well, in C extensions you have typing, period; you can't get around 
> that.  In
> C you quite often have no choice but to check your type.  In fact, the 
> vast
> majority of security hacks arise out of C programmers not checking 
> variables
> for type and/or size.  It's results in buffer overflow-style hacks 
> that not
> only result in software de-stabilization, attackers can sometimes gain
> permissions through them.

Classes defined in safe old 'script.rb' files will have to deal with 
the same lifecycle issues as classes defined in C.  You might not see 
core dumps, but same issue remains.  Any class which depends on its 
initialize method will have guard against #become.

For example -- the very useful class Tempfile is defined in 
tempfile.rb.  It depends on these variables:

   @tmpname: the name of the tempfile
   @tmpfile: the File object of the tempfile
   @@cleanlist: the list of files to be cleaned on exit, @tmpname gets 
appended to it.

If these variables are out of sync, then Tempfile is broken.  Note the 
class variable @@cleanlist.  A Tempfile might #become something else 
that changes @tmpname and @tmpfile, but that new class can't change 
@@cleanlist.

This is what I mean when I refer to lifecycle issues.  It has nothing 
to do with C; every class in Ruby will have to guard against this sort 
of problem.

And I don't think that sounds like fun.

Cheers,

Patrick