Messages in this thread | | | Date | Mon, 7 Feb 2011 17:14:45 -0800 | From | Kees Cook <> | Subject | Re: [SECURITY] /proc/$pid/ leaks contents across setuid exec |
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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
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