[racket] Handin Server + PLAI problem [and 1 more messages] [and 2 more messages]

From: Robby Findler (robby at eecs.northwestern.edu)
Date: Sat Jan 14 22:31:59 EST 2012

On Sat, Jan 14, 2012 at 9:23 PM, Eli Barzilay <eli at barzilay.org> wrote:
> 20 minutes ago, Matthias Felleisen wrote:
>> On Jan 14, 2012, at 9:45 PM, Eli Barzilay wrote:
>> > Or maybe some private parameter (or continuation mark) that can be
>> > used to identify "I'm now in blessed code" which the sandbox
>> > security guard can check and if in that case avoid the
>> > restrictions?
>> That sounds an awful lot like stack inspection a la Java -- Matthias
> Yes, but it's different in that it's based on a parameter that several
> functions can do, rather than rely on the function's identity.  (But
> all of these things are similar in the same way, I think.)
> 20 minutes ago, Robby Findler wrote:
>> The parameter solution sounds right to me and the sandbox does sound
>> like the right level to put that.
> The sandbox shouldn't be the place for that -- it would be a reversed
> dependency, where the setup (core) code depends on a library.  But in
> this case it's not only a "shoudln't" -- it's a "cannot": see the
> comment at the top of "setup/private/main-collects.rkt" about why it
> shouldn't depend on anything.
> But it would also not be right to just add some parameter to the
> main-collects code, since that would be visible and usable by any code
> to bypass security checks.

I think that security-guards and continuation marks are a good way to
build a high-level capability permissions model in Racket. I would
have thought that the sandbox would be a good library to include that
in, but maybe we should be doing something smaller that the sandbox
just uses? (Is that what you're saying?)


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