From owner-freebsd-security Wed Aug 21 13:45:10 1996 Return-Path: owner-security Received: (from root@localhost) by freefall.freebsd.org (8.7.5/8.7.3) id NAA25174 for security-outgoing; Wed, 21 Aug 1996 13:45:10 -0700 (PDT) Received: from phoenix.iss.net (phoenix.iss.net [204.241.60.5]) by freefall.freebsd.org (8.7.5/8.7.3) with SMTP id NAA25165 for ; Wed, 21 Aug 1996 13:45:03 -0700 (PDT) Received: (from davem@localhost) by phoenix.iss.net (8.6.13/8.6.12) id QAA01683; Wed, 21 Aug 1996 16:39:01 -0400 Date: Wed, 21 Aug 1996 16:38:57 -0400 (EDT) From: "David J. Meltzer" To: bugtraq@netspace.org, linux-security@tarsier.cv.nrao.edu, freebsd-security@freebsd.org, deraadt@theos.com Subject: rwhod buffer overflow In-Reply-To: <199607240541.BAA18220@hcs.HARVARD.EDU> Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: owner-security@freebsd.org X-Loop: FreeBSD.org Precedence: bulk There is a remote buffer overflow in the path variable in rwhod.c in the line: (void) sprintf(path, "whod.%s", wd.wd_hostname); Although wd_hostname is defined to be only 32 characters, it is read as part of the wd structure from a remote host through a UDP packet and can be as large as the remainder of the structure starting at that point. Through examining the source this appears to be a problem in current OpenBSD, NetBSD, FreeBSD, and Linux distributions. Through penetration testing I have also found this problem present on AIX; I have not examined other platforms running rwhod and so do not know about their potential vulnerability. I have succesfully exploited this remotely to produce undesirable effects (segfaults and overwriting argv[0] on different OSes), I have not spent sufficient time on this to determine exactly how/if to compromise root directly with this overflow, but it is definitely something that should be corrected. I would suggest prior to the sprintf line you add something to the effect: if(strlen(wd.wd_hostname) >= sizeof(wd.wd_hostname)) { syslog(LOG_WARNING, "possible hostname overflow attack apparently from %x", from.sin_addr); continue; } Program: /usr/sbin/rwhod Affected Operating Systems: OpenBSD, NetBSD, FreeBSD, Linux, AIX, others. rwhod must be running on the system Requirements: Ability to send UDP packet to target host Security Compromise: Possible denial of service, Possible annoyance, Possibly root compromise? Author: Dave M. (davem@iss.net) Synopsis: rwhod reads a structure from a udp packet and does not check the hostname member of the structure for being the expected size. --------------------------------+--------------------- David J. Meltzer | Email: davem@iss.net Systems Engineer | Web: www.iss.net Internet Security Systems, Inc. | Fax: (404)252-2427 --------------------------------+--------------------- David J. Meltzer | Email: davem@iss.net Systems Engineer | Web: www.iss.net Internet Security Systems, Inc. | Fax: (404)252-2427