Rule:

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Sid:
1273

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Summary:
This event is generated when an attempt is made through a portmap GETPORT request to discover the port where the Remote Procedure Call (RPC) selection_svc is listening.

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Impact:
Information disclosure.  This request is used to discover which port selection_svc is using.  Attackers can also learn what versions of the selection_svc protocol are accepted by selection_svc.

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Detailed Information:
The portmapper service registers all RPC services on UNIX hosts. It can be queried to determine the port where RPC services such as selection_svc run.  The selection_svc RPC service is used by SunView, an old windowing system from Sun.  A vulnerability exists in selection_svc that allows a remote user to read files that are readable by SunView. 

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Affected Systems:
Sun SunOS 3.5
Sun SunOS 4.0
Sun SunOS 4.0.1
Sun SunOS 4.0.2
Sun SunOS 4.0.3
Sun SunOS 4.1
Sun SunOS 4.1.1

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Attack Scenarios:
An attacker can query the portmapper to discover the port where selection_svc runs.  This may be a precursor to accessing selection_svc.

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Ease of Attack:
Simple.  

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False Positives:
If a legitimate remote user is allowed to access selection_svc, this rule may trigger.

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False Negatives:
This rule detects probes of the portmapper service for selection_svc, not probes of the selection_svc service itself. Because RPC services often listen on fairly arbitrary ports, it may not be possible to detect misuses of the selection_svc service itself. An attacker may attempt to go directly to the selection_svc port without querying the portmapper service which, would not trigger the rule.

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Corrective Action:
Limit remote access to RPC services.

Filter RPC ports at the firewall to ensure access is denied to RPC-enabled machines. 

Disable unneeded RPC services.

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Contributors:
Original rule written by Max Vision <vision@whitehats.com>
Modified by Brian Caswell <bmc@sourcefire.com>
Sourcefire Vulnerability Research Team
Judy Novak <judy.novak@sourcefire.com>

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Additional References:

Bugtraq
http://www.securityfocus.com/bid/8

CERT
http://www.cert.org/advisories/CA-1990-05.html

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