One document matched: draft-rahman-rtg-router-alert-dangerous-00.txt
Routing Area Working Group R. Rahman
D. Ward
Internet Draft Cisco Systems
Intended status: BCP October 2008
Expires: April 2009
Use of IP Router Alert Considered Dangerous
draft-rahman-rtg-router-alert-dangerous-00.txt
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Abstract
This document provides guidelines to address security concerns which
arise with the use of IP Router Alert option [RFC2113] and [RFC2711].
RSVP,[RFC2205] and [RFC3209], and IGMP [RFC3376] are some of the
protocols which make use of the IP Router Alert option. IP datagrams
carrying the Router Alert option are usually examined in a router's
"slow path" and an excess of such datagrams can cause performance
degradation or packet drops in a router's "slow path".
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Table of Contents
1. Introduction...................................................2
2. Conventions used in this document..............................2
3. Security Risk Of IP Router Alert Option........................2
4. Guidelines For Use Of IP Router Alert Option...................3
5. Security Considerations........................................3
6. IANA Considerations............................................4
7. Conclusions....................................................4
8. Acknowledgments................................................4
9. References.....................................................5
9.1. Normative References......................................5
1. Introduction
The main purpose of this document is to describe the security risks
associated with the use of IP Router Alert and to discourage new
applications and protocols from using IP Router Alert.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC-2119 [1].
3. Security Risk Of IP Router Alert Option
IP datagrams carrying the Router Alert option are usually examined in
a router's "slow path" and an excess of such datagrams can cause
performance degradation or packet drops in a router's "slow path".
[RFC4081] and [RFC2711] mention the security risks associated with
the use of the IP Router Alert option: flooding a router with bogus
IP datagrams which contain the IP Router Alert option would cause a
performance degradation of the router's "slow path" and can also lead
to packet drops in the "slow path".
[RFC2711] mentions that limiting, by rate or some other means, the
use of Router Alert option is a way of protecting against a potential
attack. If rate limiting is used as a protection mechanism and the
granularity of the rate limiting is coarse, an attack using packet
types of one protocol could severely degrade the operation of other
protocols using IP Router Alert option.
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4. Guidelines For Use Of IP Router Alert Option
To protect the "slow path" against DOS attacks, a router MUST have a
means of limiting the number of Router Alert IP datagrams which go to
the "slow path".
If there are multiple protocols which make use of IP Router Alert
option on a router, the limiting MUST be able to distinguish between
the various protocols. E.g. if rate limiting is used, there MUST be
different rate limit pools for the protocols so that an attack on one
protocol will not affect the operation of another protocol.
IP Router Alert packets MUST NOT be sent to the "slow path" unless
there is at least one protocol enabled which uses the IP Router Alert
option.
A router SHOULD inspect Router Alert packets before sending them to
the "slow path" so that if the protocol to which a packet belongs is
not enabled on the router or on the incoming interface (physical or
virtual), then the packet is dropped.
Introducing new protocols/applications which make use of IP Router
Alert option MUST not provide a means of attacking or harming
deployed protocols such as RSVP and IGMP which already make use of
the IP Router Alert option.
Routing and signaling users of IP Router Alert, e.g. IGMP and RSVP,
are the highest priority users and MUST NOT be impacted by other
users of IP Router Alert.
Any application that relies on IP Router Alert should expect that the
incoming packets MAY be dropped by default and that a special filter
is needed to let the packets through.
All non-routing and non-signaling IP Router Alert packets, when
enabled, may be significantly rate limited.
Creating an application or protocol that uses IP Router Alert is
considered harmful and is strongly discouraged. A different mechanism
should be used to decrease the risk of impacting existing routing and
signaling protocols which use IP Router Alert
5. Security Considerations
This document provides guidelines for security risks which are
present with the use of IP Router Alert option. Its purpose is to
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have greater security against DDOS attacks and to discourage new
applications from using IP Router Alert since this would cause a
security risk against current users of IP Router Alert.
6. IANA Considerations
7. Conclusions
Use of IP Router Alert is a security risk and should be discouraged
for new applications and protocols.
8. Acknowledgments
This document was prepared using 2-Word-v2.0.template.dot.
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9. References
[RFC2113] "IP Router Alert Option", RFC 2113, D. Katz, February
1997.
[RFC2711] "IPv6 Router Alert Option", RFC 2711, C. Partridge, et al,
October 1999.
[RFC2205] "Resource ReSerVation Protocol (RSVP) - Version 1,
Functional Specification", RFC 2205, Braden, et al, September
1997.
[RFC3209] "Extensions to RSVP for LSP Tunnels", D. Awduche, et al,
RFC 3209, December 2001.
[RFC3376] "Internet Group Management Protocol, Version 3", RFC 3376,
B. Cain, et al, October 2002.
[RFC4081] "Security Threats For Next Steps in Signaling (NSIS)", RFC
4081, H. Tschofenig, et al, June 2005
9.1. Normative References
[1] Bradner, S., "Key words for use in RFCs to Indicate Requirement
Levels", BCP 14, RFC 2119, March 1997.
[2] Crocker, D. and Overell, P.(Editors), "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, Internet Mail Consortium and
Demon Internet Ltd., November 1997.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234] Crocker, D. and Overell, P.(Editors), "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, Internet Mail
Consortium and Demon Internet Ltd., November 1997.
Author's Addresses
Reshad Rahman
Cisco Systems Inc.
2000 Innovation Dr.,
Kanata, Ontario, K2K 3E8
Canada.
Phone: (613)-254-3519
Email: rrahman@cisco.com
David Ward
Cisco Systems Inc.
3750 Cisco Way,
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San Jose, California, 95134
United States
Phone: (651)-726-2368
Email: wardd@cisco.com
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