Re: [iputils] Integer overflow in iputils ping/ping6 tools

[Gage Bystrom <themadichib0d () gmail com>]

Shoulda gotten a lawyer o.O professor sex scandals can rake in decent money
On Mar 13, 2012 4:32 PM, "Jeffrey Walton" <noloader () gmail com> wrote:

> On Tue, Mar 13, 2012 at 6:17 PM, Marcus Meissner <meissner () suse de> wrote:
> > Hi,
> >
> > How is this different from writing a fork bomb?
> :)
>
> Fork bombs can be remediated with RLIMIT_NPROC. The runaway ping
> program needs to be fixed and then recompiled.
>
> I suppose you could say the same about runaway fork'd programs,
> though. I had one accidentally get away from me in college. The
> professor who performed the post-mortem was very impressive. He had me
> fingered in under an hour.
>
> Jeff
>
> > On Tue, Mar 13, 2012 at 09:42:29AM +0100, Christophe Alladoum wrote:
> > > ====[ Description ]====
> > >
> > > An integer overflow was found in iputils/ping_common.c main_loop()
> function
> > > which could lead to excessive CPU usage when triggered (could lead to
> DoS). This
> > > means that both ping and ping6 are vulnerable.
> > >
> > >
> > > ====[ Proof-Of-Concept ]====
> > >
> > > Specify "big" interval (-i option) for ping/ping6 tool:
> > > {{{
> > > $ ping -i 3600 google.com
> > > PING google.com (173.194.66.102) 56(84) bytes of data.
> > > 64 bytes from we-in-f102.1e100.net (173.194.66.102): icmp_req=1 ttl=50
> time=11.4 ms
> > > [...]
> > > }}}
> > >
> > > And check your CPU usage (top, htop, etc.)
> > >
> > >
> > > ====[ Explanation ]====
> > >
> > > Here, ping will loop in main_loop() loop in this section of code :
> > > {{{
> > > /* from iputils-s20101006 source */
> > > /* ping_common.c */
> > >
> > >     546 void main_loop(int icmp_sock, __u8 *packet, int packlen)
> > >     547 {
> > > [...]
> > >     559         for (;;) {
> > > [...]
> > >     572                 do {
> > >     573                         next = pinger();
> > >     574                         next = schedule_exit(next);
> > >     575                 } while (next <= 0);
> > > [...]
> > >     588                 if ((options & (F_ADAPTIVE|F_FLOOD_POLL)) ||
> next<SCHINT(interval)) {
> > > [...]
> > >     593                         if (1000*next <= 1000000/(int)HZ) {
> > > }}}
> > >
> > > If interval parameter (-i) is set, then condition L593 will overflow
> (ie. value
> > > exceeding sizeof(signed integer)), making this statement "always true"
> for big
> > > values (e.g. -i 3600). As a consequence, ping process will start looping
> > > actively as long as condition is true (could be pretty long).
> > >
> > > As far as looked, this bug is unlikely to be exploitable besides
> provoking
> > > Denial-Of-Service.
> > >
> > >
> > > ====[ Affected versions ]====
> > >
> > > Tested on Fedora/Debian/Gentoo Linux system (2.6.x x86_32 and x86_64)
> on iputils
> > > version 20101006. ping6 seems also to be affected since it's relying on
> same
> > > ping_common.c functions.
> > >
> > > Since iputils is not maintained any longer
> > > (http://www.spinics.net/lists/netdev/msg191346.html), patch must be
> applied from
> > > source.
> > >
> > >
> > > ====[ Patch ]====
> > > Quick'n dirty patch (full patch in appendix) is to cast test result as
> long long:
> > > {{{
> > >     593                  if (((long long)1000*next) <= (long
> long)1000000/(int)HZ) {
> > > }}}
> > >
> > >
> > > ====[ Credits ]====
> > > * Christophe Alladoum (HSC)
> > > * Romain Coltel (HSC)
>
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