======================================================================
Network Associates, Inc.
SECURITY ADVISORY
February 7, 2000
SNMPD default writable community string
======================================================================
SYNOPSIS
The default configuration of SCO OpenServer 5.0.5 allows local users
read/write access to SNMPD via a default writable community string.
======================================================================
VULNERABLE HOSTS
This configuration has been verified on SCO OpenServer 5.0.5 and may
be present in earlier versions.
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DETAILS
SNMP(S.imple N.etwork M.anagement P.rotocol) is a protocol suite
used to manage information obtained from network entities such as
hosts, routers, switches, hubs, etc. A management station collects
the information from these various network entities via SNMP variable
querys. Information events called traps can also be sent from
entities to managment stations notifying the station of critical
changes such as changes to interface status, packet collisions, etc.
These domains of SNMP managment stations and entities are grouped
togather in what are called communities. The community name (called
the community string) is used as the authentication method used for
information retrieval/traps. There are 2 types of community strings
read(public), and write(private). A read community has privilages
to retrieve variables from SNMP entities and a write community has
privilages to read as well as write to entity variables.
The problem lies in that the default installation of SCO OpenServer
5.0.5 has snmpd enabled with a default write(private) community string.
SCO has released a security bulletin for this vulnerability, which can
be found at: http://www.sco.com/security.
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TECHNICAL DETAILS
SNMPD, run on startup by SCO OpenServer 5.0.5, is configured by
default with a writable(private) community string. This allows any
local user full administrator access to the SNMPD facility. The potential
abuses of this privelege include the ability to modify hostname,
network interface state, IP forwarding and routing, state of network
sockets (including the ability to terminate active TCP sessions and
listening sockets) and the ARP cache. An attacker also has full read
access to all SNMP facilities.
======================================================================
RESOLUTION
The community string definitions can be found in /etc/snmpd.comm
Remove/modify these strings and restart snmpd. Alternatively, if your
site does not use SNMP, kill snmpd and remove it from system startup
files.
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CREDITS
Discovery and documentation of this vulnerability was conducted by
Shawn Bracken <shawn_brackenat_private> at the security labs of Network
Associates.
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ABOUT THE NETWORK ASSOCIATES SECURITY LABS
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For more information about the Security Labs at Network
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at <seclabsat_private>.
======================================================================
NETWORK ASSOCIATES SECURITY LABS PGP KEY
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