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Date: Mon, 7 Feb 2011 17:14:45 -0800 From: Kees Cook <kees.cook@...onical.com> To: James Morris <jmorris@...ei.org> Cc: linux-kernel@...r.kernel.org Subject: Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec Hi James, On Tue, Feb 08, 2011 at 11:44:40AM +1100, James Morris wrote: > On Mon, 7 Feb 2011, Kees Cook wrote: > > > $ ./procleak.py auxv,syscall /usr/bin/passwd > > running > > AT_BASE: 0x7f2828bde000 > > AT_RANDOM: 0x7fff80bde7c9 > > Changing password for kees. > > (current) UNIX password: 0 0x0 0x7fff80bdda90 0x1ff 0x7fff80bdd580 0x7f2828dc57c0 0x7f28287cec1d 0x7fff80bdd088 0x7f28282fe6c0 > > > > There needs to be some way to break the connection to these files across > > the setuid exec, or perform some sort of revalidation of permissions. (Maybe > > check dumpable?) > > The way to do this is to set O_CLOEXEC. Sure, I know about O_CLOEXEC, but this is about protecting the just-been-execed setuid process from the attacking process that has no reason to set O_CLOEXEC. Something like this needs to be enforced on the kernel side. I.e. these file in /proc need to have O_CLOEXEC set in a way that cannot be unset. > Changing the behavior in the core kernel will break userspace. I don't think /proc/$pid/* needs to stay open across execs, does it? Or at least the non-0444 files should be handled separately. -Kees -- Kees Cook Ubuntu Security Team -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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