The existence of this bug - but NOTHING about it's security implications - was posted by one "Peter Suschlik (peterat_private)" to the ntop-dev mailing list on 28Feb2002: http://listmanager.unipi.it/pipermail/ntop-dev/2002-February/000489.html I'm not ntop's author (Luca Deri), so I can't speak as to whether this is the same individual, or whether an attempt was made to contact the developers. The source was corrected in snapshots (available at http://snapshot.ntop.org) beginning with ntop-02-03-01.tgz and all subsequent versions. Although this bug may allow for arbitrarily code execution, the risk is limited if the user follows good practices. Still, an upgrade to snapshot versions on/after 01Mar2002 is recommended to all ntop users. ntop requires root privileges at startup in order to place the network interface into promiscuous mode. ntop provides the -u <username> parameter to allow ntop to run as an unprivileged user, as soon as possible after execution begins. This occurs BEFORE the web server is started. If the user continues to run as root, a WARNING message is displayed. A pending patch will further tighten down the security screen on requested URLs. This message is being copied to the two ntop mailing lists and I will also add this information to the ntop community FAQs, also available at snapshot. -----Burton -----Original Message----- From: hologram [mailto:holoat_private] Sent: Monday, March 04, 2002 6:46 AM To: bugtraqat_private Subject: [H20020304]: Remotely exploitable format string vulnerability in ntop h o l o g r a m | s e c u r i t y | a d v i s o r y _______________________________________________________________________ Advisory ID : H20020304 Software : ntop Synopsis : Remotely exploitable format string vulnerability in ntop. Vendor : Luca Deri <www.ntop.org> Verified : Version 2.0 Author : hologram <holoat_private> _______________________________________________________________________ | Overview |----------------------------------------------------------- ntop is a UNIX tool that shows the network usage, similar to what the popular top UNIX command does on the system level. A format string vulnerability has been discovered on the programmatic level and is currently known to affect the UNIX version, however, the Windows port of the program remains untested. The vulnerability allows for remote arbitrary code execution. | Vulnerability |------------------------------------------------------ The format string vulnerability lies within the traceEvent() function which is declared as: void traceEvent(int eventTraceLevel, char* file, int line, char * format, ...) in the file util.c. The third argument, as is apparent, is a format string to be later manipulated by the traceEvent() call. Further into the code, the following is made visible: ... va_list va_ap; va_start (va_ap, format); ... char buf[BUF_SIZE]; ... #ifdef WIN32 /* Windows lacks of vsnprintf */ vsprintf(buf, format, va_ap); #else vsnprintf(buf, BUF_SIZE-1, format, va_ap); #endif if(!useSyslog) { // syslog() logging is not enabled printf(buf); // vulnerability ... #ifndef WIN32 else { // syslog() logging is enabled #if 0 switch(traceLevel) { case 0: syslog(LOG_ERR, buf); // vulnerability break; case 1: syslog(LOG_WARNING, buf); // vulnerability break; case 2: syslog(LOG_NOTICE, buf); // vulnerability break; default: syslog(LOG_INFO, buf); // vulnerability break; } #else syslog(LOG_ERR, buf); ... Obviously, a call such as syslog(LOG_ERR, buf) should be replaced with syslog(LOG_ERR, "%s", buf) to remove the insecurity. The bug can be exploited whether or not syslog() logging is enabled because of the erroneous printf(buf) call, as well. One of the simplest points of entry I have determined is if the -w option was specified when ntop was ran, which allows web access to the ntop information. A HTTP request of the following: GET /%s%s%s HTTP/1.0 will cause program termination (the HTTP deamon for ntop is normally listening on port 3000). The vulnerability does allow remote execution of arbitrary commands, and if concerned, an appropriate fix should be quickly applied. -------------------------------| Copyright 2002. All rights reserved. |
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