lkml.org 
[lkml]   [2011]   [Mar]   [16]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
    /
    Date
    From
    SubjectRe: [PATCH] [RFC] Make it easier to harden /proc/
    On Wed, Mar 16, 2011 at 10:07:48PM +0100, Richard Weinberger wrote:
    > Am Mittwoch 16 März 2011, 22:04:52 schrieb Alexey Dobriyan:
    > > On Wed, Mar 16, 2011 at 09:52:49PM +0100, Richard Weinberger wrote:
    > > > Am Mittwoch 16 März 2011, 21:45:45 schrieb Arnd Bergmann:
    > > > > On Wednesday 16 March 2011 21:08:16 Richard Weinberger wrote:
    > > > > > Am Mittwoch 16 März 2011, 20:55:49 schrieb Kees Cook:
    > > > > > > On Wed, Mar 16, 2011 at 08:31:47PM +0100, Richard Weinberger wrote:
    > > > > > > > When containers like LXC are used a unprivileged and jailed
    > > > > > > > root user can still write to critical files in /proc/.
    > > > > > > > E.g: /proc/sys/kernel/{sysrq, panic, panic_on_oops, ... }
    > > > > > > >
    > > > > > > > This new restricted attribute makes it possible to protect such
    > > > > > > > files. When restricted is set to true root needs CAP_SYS_ADMIN
    > > > > > > > to into the file.
    > > > > > >
    > > > > > > I was thinking about this too. I'd prefer more fine-grained control
    > > > > > > in this area, since some sysctl entries aren't strictly controlled
    > > > > > > by CAP_SYS_ADMIN (e.g. mmap_min_addr is already checking
    > > > > > > CAP_SYS_RAWIO).
    > > > > > >
    > > > > > > How about this instead?
    > > > > >
    > > > > > Good Idea.
    > > > > > May we should also consider a per-directory restriction.
    > > > > > Every file in /proc/sys/{kernel/, vm/, fs/, dev/} needs a protection.
    > > > > > It would be much easier to set the protection on the parent directory
    > > > > > instead of protecting file by file...
    > > > >
    > > > > How does this interact with the per-namespace sysctls that Eric
    > > > > Biederman added a few years ago?
    > > >
    > > > Do you mean CONFIG_{UTS, UPC, USER, NET,}_NS?
    > >
    > > It only covers /proc/sys/net/
    >
    > Exactly.
    >
    > > > > I had expected that any dangerous sysctl would not be visible in
    > > > > an unpriviledge container anyway.
    > > >
    > > > No way.
    > >
    > > No way what exactly?
    >
    > Dangerous sysctls are not protected at all.
    > E.g. A jailed root can use /proc/sysrq-trigger.

    Yes, and it's suggested that you do not show it at all,
    instead of bloaing ctl_table.

    But this requires knowledge which /proc is root and which one is "root".
    :-(

    With current splitup into FOO_NS...
    --
    To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
    the body of a message to majordomo@vger.kernel.org
    More majordomo info at http://vger.kernel.org/majordomo-info.html
    Please read the FAQ at http://www.tux.org/lkml/

    \
     
     \ /
      Last update: 2011-03-16 22:19    [W:0.026 / U:1.108 seconds]
    ©2003-2016 Jasper Spaans. hosted at Digital OceanAdvertise on this site