full-disclosure - Re: [FD] #WorldPenguinDay or this cant be right, can it?

Open Source and information security mailing list archives

Date: Fri, 1 May 2015 03:11:08 -0400
From: PIN <zero@...c.co>
To: Tavis Ormandy <taviso@...xchg8b.com>
Cc: fulldisclosure@...lists.org
Subject: Re: [FD] #WorldPenguinDay or this cant be right, can it?

> It sounds like you're asking "If I can learn an address, have I defeated
> ASLR", and the answer is usually yes.

Really? Because leaking a heap address in windows, openbsd, etc doesn't
yield a full collapse of all loaded modules randomization given the
preconditions; I'm asking that it's not just my box exhibiting this
behavior- which is a long story why it must just be mine.

>It depends on the circumstances of
> course, but leaking any address to an attacker would usually be
considered a
> bug and renders ASLR essentially useless.

Well, you are somewhat missing the gravity here. If this is generally
reproducible, you don't need the address to leak, you just need a series of
arithmetic operations to land you at a fixed offset within the target
module. no read back requisite.

I wouldn't argue that finding the exact required arguments for arithmetic
was not rare however, just that an ASLR "metaprogramming primitive"
potentially exists.

> For example, if you can find some JavaScript that tells you the address of
> an object on the heap or the base address of a module, that would be
> considered a security bug.

I'm fairly positive that no ASLR scheme is intended to entirely and totally
collapse given a single address that you don't necessarily even need to
know. Thus I find it hard to believe this is the case.

>You don't usually run untrusted python, > so
> python's id() isn't a bug - but you do run untrusted JavaScript.

Really? Because your employer does exactly that. The bigger question was
the behavior, not python. It seems a practical extension of the spy in the
sandbox stuff to potentially grab enough of an address to leverage this in
javascript, although code is not yet forthcoming there. However giving the
cache line and physical to virtual address scheme mappings, this seems
likely.

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