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    SubjectRe: [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:
    > > $ ./ 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 Cook
    Ubuntu Security Team

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      Last update: 2011-02-08 02:17    [W:0.021 / U:21.916 seconds]
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