CERT Advisory CA-2001-05

[babay at mediaone.net (Brian Bay)]

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CERT Advisory CA-2001-05 Exploitation of snmpXdmid

   Original release date: March 30, 2001
   Source: CERT/CC

   A complete revision history can be found at the end of this file.


Systems Affected

   Any machine running Solaris 2.6, 7, or 8 with snmpXdmid installed and
   enabled. snmpXdmid is installed and enabled by default on these
   systems.


Overview

   The CERT/CC has received numerous reports indicating that a
   vulnerability in snmpXdmid is being actively exploited. Exploitation
   of this vulnerability allows an intruder to gain privileged (root)
   access to the system.


I. Description

   The SNMP to DMI mapper daemon (snmpXdmid) translates Simple Network
   Management Protocol (SNMP) events to Desktop Management Interface
   (DMI) indications and vice-versa. Both protocols serve a similar
   purpose, and the translation daemon allows users to manage devices
   using either protocol. The snmpXdmi daemon registers itself with the
   snmpdx and dmid daemons, translating and forwarding requests from one
   daemon to the other.

   snmpXdmid contains a buffer overflow in the code for translating DMI
   indications to SNMP events. This buffer overflow is exploitable by
   local or remote intruders to gain root privileges.

   More information about this vulnerability can be found in

     CERT/CC Vulnerability Note VU#648304
     Sun Solaris DMI to SNMP mapper daemon snmpXdmid contains buffer
overflow
     http://www.kb.cert.org/vuls/id/648304

   Affected sites have reported discovering the following things on
   compromised systems:

     * Evidence of extensive scanning for RPC services (port
       111/{udp,tcp}) with explicit requests for the snmpXdmid service
       port prior to the exploit attempt
     * A core file from snmpXdmid on the / partition
     * An additional copy of inetd running (possibly using /tmp/bob as a
       configuration file)
     * A root-privileged telnet backdoor installed and listening on port
       2766 (although any port could be used)
     * An SSH backdoor installed and listening on port 47018 (although
       any port could be used)
     * An IRC proxy installed as /var/lp/lpacct/lpacct and listening on
       port 6668
     * A sniffer installed as /usr/lib/lpset
     * Logs altered to hide evidence of the compromise
     * System binaries replaced by a rootkit installed in /dev/pts/01/
       and /dev/pts/01/bin (the versions of 'ls' and 'find' installed
       by the rootkit do not show these directories)
       
       The contents of /dev/pts/01 may include
          + bin
          + crypt
          + idsol
          + patcher
          + su-backup
          + utime
          + bnclp
          + idrun
          + l3
          + pg
          + urklogin
       
       The contents of /dev/pts/01/bin may include
	  + du
	  + find
	  + ls
	  + netstat
	  + passwd
	  + ping
	  + psr
	  + sparcv7
	  + su

   Note: Since 'ps' and 'netstat' are both replaced by the rootkit, they
   will not show these processes or open ports. However, you may find
   that '/usr/ucb/ps' is still intact, and will show the additional
   processes.


II. Impact

   A local or remote user that is able to send packets to the snmpXdmi
   daemon on a system may gain root privileges.


III. Solution

     * Apply a patch from Sun when it is available
       Sun has been notified of this issue and is actively working on
       patches to address the problem. This advisory will be updated
when
       patches are available.
     
     * Disable snmpXdmi
       Until patches are available, sites that do not use both SNMP and
       DMI are stongly encouraged to disable snmpXdmid.
       
       One way to accomplish this is to issue the following commands (as
       root):

       1. Prevent the daemon from starting up upon reboot
	       mv /etc/rc3.d/SXXdmi /etc/rc3.d/KXXdmi
       2. Killing the currently running daemon
	       /etc/init.d/init.dmi stop`
       3. Verify that the daemon is no longer active
	       ps -ef | grep dmi
       4. As an additional measure, you may wish to make the daemon
          non-executable
	       chmod 000 /usr/lib/dmi/snmpXdmid

     * Restrict access to snmpXdmi and other RPC services
       For sites that require the functionality of snmpXdmi or other RPC
       services, local IP filtering rules that prevent hosts other than
       localhost from connecting to the daemon may mitigate the risks
       associated with running the daemon. Sun RPC services are
advertised on
       port 111/{tcp,udp}. The snmpXdmid RPC service id is 100249; use
       'rpcinfo -p' to list local site port bindings:
   
	# rpcinfo -p | grep 100249
	100249 1 udp 32785
	100249 1 tcp 32786
   
       Note that site-specific port binding will vary.


Appendix A. - Vendor Information

   Sun Microsystems

   We can confirm that this affects all versions of Solaris that ship
the
   SNMP to DMI mapper daemon, that is, Solaris 2.6, 7 and 8. To the best
   of my understanding from discussion with the engineering group
working
   on this, for sites which do use DMI (dmispd) and the mapper
   (snmpXdmid), there are no workarounds.
   
  
______________________________________________________________________

   The CERT/CC thanks Job de Haas (job at itsx.com) of ITSX BV Amsterdam,
   The Netherlands (http://www.itsx.com) for reporting this
vulnerability
   to the CERT/CC.
  
______________________________________________________________________

   This document was written by Brian B. King with significant
   contributions by Jeff Havrilla, and Cory F. Cohen.
  
______________________________________________________________________

   This document is available from:
   http://www.cert.org/advisories/CA-2001-05.html
  
______________________________________________________________________

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______________________________________________________________________

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   Revision History
   March 30, 2001: Initial release






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