SCO OpenServer SNMPD vulnerability

[seclabs () NAI COM (NAI Labs)]

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                     Network Associates, Inc.
                        SECURITY ADVISORY
                        February 7, 2000

           SNMPD default writable community string

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SYNOPSIS

The default configuration of SCO OpenServer 5.0.5 allows local users
read/write access to SNMPD via a default writable community string.

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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.

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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_bracken () nai com> at the security labs of Network
Associates.

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