Home / exploits IPUtils Denial Of Service
Posted on 14 March 2012
====[ 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) -- Christophe Alladoum - <christophe.alladoum@hsc.fr> Hervé Schauer Consultants - <http://www.hsc.fr>
