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    SubjectRe: [SECURITY] /proc/$pid/ leaks contents across setuid exec
    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.

    See:

    http://udrepper.livejournal.com/20407.html
    https://www.securecoding.cert.org/confluence/display/seccode/FIO42-C.+Ensure+files+are+properly+closed+when+they+are+no+longer+needed

    Changing the behavior in the core kernel will break userspace.



    - James
    --
    James Morris
    <jmorris@namei.org>


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