Re: Process table attack (from RISKS Digest)

[jkb () BEST COM (Jan B. Koum)]

On Sat, Feb 20, 1999 at 01:42:53PM -0800, Mark Boolootian <booloo () cats ucsc edu> wrote:
> Date: Fri, 19 Feb 1999 16:08:06 -0500
> > From: "Simson L. Garfinkel" <simsong () vineyard net>
> Subject: Process-table attack
>
> Wide-ranging attack works against almost any UNIX systems on the Internet
>
> ABSTRACT:
>
> The Process Table Attack is a [relatively] new kind of denial-of-service
> attack that can be waged against numerous network services on a variety of
> different UNIX systems. The attack is launched against network services
> which fork() or otherwise allocate a new process for each incoming TCP/IP
> connection.  Although the standard UNIX operating system places limits on
> the number of processes that any one user may launch, there are no limits on
> the number of processes that the superuser can create other than the hard
> limits imposed by the operating system. Since incoming TCP/IP connections
> are usually handled by servers that run as root, it is possible to
> completely fill a target machine's process table with multiple
> instantiations of network servers. Properly executed, this attack prevents
> any other command from being executed on the target machine.

        I have not tested this, but I don't think this is true for at
        least FreeBSD. You see, it has what is called login limits and you
        can indeed put limits on root login user. From /etc/login.conf:

#root:\
#:cputime=infinity:\
#:datasize=infinity:\
#:stacksize=infinity:\
#:memorylocked=infinity:\
#:memoryuse=infinity:\
#:filesize=infinity:\
#:coredumpsize=infinity:\
#:openfiles=infinity:\
#:maxproc=infinity:\
#:memoryuse-cur=32M:\
#:maxproc-cur=64:\
#:openfiles-cur=1024:\
#:priority=0:\
#:requirehome@:\
#:umask=022:\
#:tc=auth-root-defaults:

        As far as I know (and I am sure 2829 peole will correct me if I am not),
        changing infinity to a numeric value should produce a desired result.
        AGAIN: I have not tested this yet for root user - but I know that the
        login limits do work for normal users.

-- Yan