HP-UX - Security Vulnerability with PMTU Strategy
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CIAC INFORMATION BULLETIN
K-018: HP-UX - Security Vulnerability with PMTU Strategy
January 25, 2000 17:00 GMT
PROBLEM: Hewlett-Packard's proprietary protocol for discovering the
maximum path MTU for a connection is flawed.
PLATFORM: HP-UX versions 10.30 and 11.0
DAMAGE: A vulnerable machine could be used as an amplifier in a
DoS (Denial-of-Service) attack.
SOLUTION: Follow the instructions in the HP-UX Advisory listed below.
VULNERABILITY The risk is low. However, because the number of DoS
ASSESSMENT: attempts and attacks has been on the rise, it is recommended
that the following instructions in the attached Advisory from
Hewlett-Packard be followed as soon as possible.
[ Begin Hewlett-Packard Security Advisory ]
Document ID: HPSBUX0001-110
Date Loaded: 20000123
Title: Security Vulnerability with PMTU strategy
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HEWLETT-PACKARD COMPANY SECURITY ADVISORY: #00110, 24 Jan 2000
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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.
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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.
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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:
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--------------------------------------
[ End Hewlett-Packard Security Advisory ]
CIAC wishes to acknowledge the contributions of Hewlett-Packard Corporation for the
information contained in this bulletin.
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UCRL-MI-119788
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