Closing information leaks in jails?

From: Attila Nagy (
Date: 08/18/05

  • Next message: Attila Nagy: "Re: Closing information leaks in jails?"
    Date: Thu, 18 Aug 2005 16:48:18 +0200


    I'm wondering about closing some information leaks in FreeBSD jails from
    the "outside world".

    Not that critical (depends on the application), but a simple user, with
    restricted devfs in the jail (devfsrules_jail for example from
    /etc/defaults/devfs.rules) can figure out the following:

    - network interfaces related data, via ifconfig, which contains
    everything, but the primary IP address of the interfaces. It seems that
    alias IPs can be viewed:
    bge0: flags=8843<UP,BROADCAST,RUNNING,SIMPLEX,MULTICAST> mtu 1500
            ether 00:12:79:3d:83:c2
            media: Ethernet autoselect (100baseTX <full-duplex>)
            status: active
    lo0: flags=8049<UP,LOOPBACK,RUNNING,MULTICAST> mtu 16384
            inet netmask 0xff000000

    - the arp table via arp, which does contain the above interface
    addresses. This can be used for example to detect other machines on the
    same subnet, which communicate with the host machine.
    - full dmesg output after boot and the kernel buffer when it overflows
    (can contain sensitive information)
    - information about geom providers (at least geom mirror list works)
    - the list of the loaded kernel modules via kldstat
    - some interesting information about the network related stuff via netstat
    - information about configured swap space via swapinfo
    - NFS related statistics via nfsstat
    - a lot of interesting stuff via sysctl

    and maybe more, I can't think of currently.

    Are there any ways to close (some of) these?


    Attila Nagy                                   e-mail:
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