Security Advisory

hs-kader-logo.gif (586 bytes) CERT-NL
Author/Source : Jan Meijer Index : S-00-05
Distribution : World Page : 1
Classification : External Version : 1
Subject : Security Vulnerability with PMTU strategy Date : 24-Jan-2000

By courtesy of HP we received information on a vulnerability in the PMTU strategy of HP-UX. An HP-UX 10.30/11.00 system can be used as an IP traffic amplifier.

CERT-NL recommends to follow the in the advisory mentioned procedure.


Digest Name: Daily Security Bulletins Digest
Created: Mon Jan 24 3:00:03 PST 2000

Table of Contents:

Document ID Title


HPSBUX0001-110 Security Vulnerability with PMTU strategy

The documents are listed below.


Document ID: HPSBUX0001-110
Date Loaded: 20000123
Title: Security Vulnerability with PMTU strategy

 

HEWLETT-PACKARD COMPANY SECURITY ADVISORY: #00110, 24 Jan 2000

The information in the following Security Advisory should be acted upon as soon as possible. Hewlett-Packard Company will not be liable for any consequences to any customer resulting from customer's failure to fully implement instructions in this Security Advisory as soon as possible.


PROBLEM: An HP-UX 10.30/11.00 system can be used as an IP traffic amplifier. Small amounts of inbound traffic can result in larger amounts of outbound traffic.
PLATFORM: HP-UX release 10.30 and 11.00 only.
DAMAGE: Depending upon the amount and nature of inbound traffic, an HP-UX 10.30/11.00 system can be used to flood a target system with IP packets which could result in a denial of service.
SOLUTION: Set the NDD parameter ip_pmtu_strategy to 1.
AVAILABILITY: This capability is already available.

I.

A. Background
HP provides a proprietary method for determining PMTU. When traffic needs to be routed to a destination for which the optimum MTU has not been determined, ICMP packets are used to discover the MTU for that path while data traffic is shipped in parallel.
This is the default strategy for determining PMTU.

B. Recommended solution
Reference ndd manpage (1M), /etc/rc.config.d/nddconf

To ensure that this parameter is set each time the system is booted, add the following lines to /etc/rc.config.d/nddconf

TRANSPORT_NAME[<index>]=ip
NDD_NAME[<index>]=ip_pmtu_strategy
NDD_VALUE[<index>]=1

The value of <index> is an integer from 0 to 99. The first parameter specified in the file should use an <index> of 0, the second an <index> of 1, and so on.

Once these changes have been made, execute the following command:

/usr/bin/ndd -c

This sets all of the options specified in the file /etc/rc.config.d/nddconf.

To verify that the parameter is set correctly, use the following command.

/usr/bin/ndd -get /dev/ip ip_pmtu_strategy

This should report a value of 1.

Another way to change the ip_pmtu_strategy parameter on a running system is to use the following NDD command:

/usr/bin/ndd -set /dev/ip ip_pmtu_strategy 1

This setting will only last until the system is rebooted at which point the value of the parameter will be determined by the default value of 2 or whatever value is set in /etc/rc.config.d/nddconf

C. To subscribe to automatically receive future NEW HP Security Bulletins from the HP IT Resource Center via electronic mail, do the following:

Use your browser to get to the HP IT Resource Center page at:

http://us-support.external.hp.com
(for US, Canada, Asia-Pacific, & Latin-America)
http://europe-support.external.hp.com   (for Europe)

Under the Maintenance and Support Menu (Electronic Support Center):
click on the "more..." link. Then -

To -subscribe- to future HP Security Bulletins, or
To -review- bulletins already released
click on "Support Information Digests" near the bottom of the page, under "Notifications".

Login with your user ID and password (or register for one).
(Remember to save the User ID assigned to you, and your password).

On the "Support Information Digest Main" page:
click on the "HP Security Bulletin Archive".

Once in the archive the third link is to our current Security Patch Matrix. Updated daily, this matrix categorizes security patches by platform/OS release, and by bulletin topic.

The security patch matrix is also available via anonymous ftp:

ftp://us-ffs.external.hp.com/~ftp/export/patches/hp-ux_patch_matrix

E. To report new security vulnerabilities, send email to security-alert@hp.com.

Please encrypt any exploit information using the security-alert PGP key, available from your local key server, or by sending a message with a -subject- (not body) of 'get key' (no quotes) to security-alert@hp.com.

Permission is granted for copying and circulating this Advisory to Hewlett-Packard (HP) customers (or the Internet community) for the purpose of alerting them to problems, if and only if, the Advisory is not edited or changed in any way, is attributed to HP, and provided such reproduction and/or distribution is performed for non-commercial purposes.

Any other use of this information is prohibited. HP is not liable for any misuse of this information by any third party.


-----End of Document ID: HPSBUX0001-110--------------------------------------


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