Re: RFC: Cygwin 64 bit?

[Ryan Johnson <ryan dot johnson at cs dot utoronto dot ca>]

On 18/08/2011 9:24 AM, Corinna Vinschen wrote:
> On Aug 18 15:10, Peter Rosin wrote:
> > Den 2011-08-18 11:20 skrev Corinna Vinschen:
> > > So, nobody except Earnie is interested in the way dlopen opens shared
> > > objects?  Nobody even replied to the idea of the pseudo algorithm below.
> > > Does really nobody care?
> > I have one little reservation, I don't like it when adding a seemingly
> > unrelated file can break old stuff. For example, let's say that I in the
> > future have an application that relies on the fact that it can dlopen
> > "libfoo.so" and get "cygfoo.dll". Everything works fine. If I then
> > install something that brings in a real "libfoo.so" things will break.
> > It's even a security problem because a carefully crafted rouge
> > libfoo.so can appear to work but do unwanted stuff behind my back.
> That's a good point.  I don't know how critical that is.  Maybe it would
> help to change the order, along these lines:
>
>    incoming: libfoo.so
>    1. check: cygfoo.dll
>    2. check: libfoo.dll
>    3. check: libfoo.so
>
> But, of course, regardless of the order, there's always a chance to
> slip something in.
In theory it does sound bad, but I'm not sure how much of a hole it 
leaves in practice: the fact that the adversary has to resort to 
different names rather than simply replacing the targeted library means 
they have pretty limited control. They can't just delete/rename their 
target, nor can they stick a decoy earlier in [LD_LIBRARY_]PATH, so they 
have to resort to exploiting this name overloading. The only way around 
it that I can think of right off would be if some directory in the 
search path has the 't' permission set (like /tmp does), so they can add 
new files even though they can't mess with other files there. That seems 
unlikely (or at least, easily fixed).

More likely it just adds a new facet to the existing dll purgatory which 
poor unfortunate developers already have to navigate. Which, ironically, 
is usually resolved by putting everything you care about in the same 
directory as the executable (so maybe that's another reason to leave 
dlls in/bin).

Ryan