Advisory CA-2001-05

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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.

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

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

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

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Revision History
March 30, 2001: Initial release

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