Internet DRAFT - draft-lai-mip4-proxy-sequence-problem
draft-lai-mip4-proxy-sequence-problem
MIP4 Working Group S. Lai
Internet-Draft H. Deng
Expires: December 22, 2006 Hitachi (China)
June 20, 2006
Problem of Replay Protection Using Sequence Number in Proxy Mobile IPv4
draft-lai-mip4-proxy-sequence-problem-00.txt
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Abstract
The document presents the problems of replay protection using
sequence number in proxy Mobile IPv4 solution. The sequence number
cannot prevent registration message from replay attack.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Problem of Using Sequence Number for Replay Protection . . . . 4
4. Security Considerations . . . . . . . . . . . . . . . . . . . . 5
5. References . . . . . . . . . . . . . . . . . . . . . . . . . . 5
5.1. Normative References . . . . . . . . . . . . . . . . . . . 5
5.2. Informative References . . . . . . . . . . . . . . . . . . 5
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 6
Intellectual Property and Copyright Statements . . . . . . . . . . 7
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1. Introduction
Proxy Mobile IPv4 is a helpful solution which to provide mobility for
mobile device with no MIP4 function [RFC3344]. The main idea of
proxy Mobile IP is that an Mobile IPv4 entity, defined as Mobility
Proxy Agent in this document, offers mobility service for a mobile
device by initiating the MIP4 registration procedure on behalf of
mobile device.
In Proxy MIP4 solution [Proxy-MIP4], a new registration doesn't have
sequence number and re-registration containes sequence number
assigned by Home Agent(HA). Hence HA can distinguish a new
registration from stale registrations generated by previous Mobility
Proxy Agent.
However, such sequence number cannot prevent registration message
from replay attack. An attacker can intercept previous new
registration and replay it to HA. Then HA will be deceived by the
replayed registration and bind a wrong care-of address for mobile
device.
2. Terminology
The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in BCP 14, [RFC2119].
The following new terminology and abbreviations are introduced in
this document and all other general mobility related terms as defined
in Mobile IPv4 specification [RFC3543].
Mobile Station (MS)
Any IPv4 node that has the ability to physically access or roam
across different networks. The Mobile Station does not
necessarily have the Mobile IPv4 protocol stack.
Mobility Proxy Agent (MPA)
The Mobile IPv4 entity that offers proxy mobility service for a
Mobile Station by performing registration function on the host's
behalf. It may be the Access Point, Base Station, Mobile
Terminal, Access Router, or Access Gateway.
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3. Problem of Using Sequence Number for Replay Protection
MS MPA-1 MPA-2 HA
|MS @ MPA-1 | | |
x-----------x | |
| |Reg Request| |
| |(no sequence number) |
1)| o---------------------->|
| | | |
2)| | | o MS @ MPA-1
| | | |
| | |Reg Reply |
| | |sequence=X |
3)| |<----------------------o
| | | |
|MS moved to MPA-2 | |
x-----------------------x |
| | |Reg Request|
| | |(no sequence number)
4)| | o---------->|
| | | |
5)| | | o MS @ MPA-2
| | | |
| | |Reg Reply |
| | |sequence=X+1
6)| | |<----------o
| | | |
Figure 1: Sequence Maintenance in Proxy Mobile IPv4
The using of sequence number in Proxy MIP4 [Proxy-MIP4] is
illustrated in figure 1. When MPA is attached to MPA1, MPA1 will
send Registration Request with no sequence number on MS's
behalf(step1). HA assigns a sequence number 'X' in the Registration
Reply. Subsequent registration requests from MPA1 contains the
sequence number. After MS moves and connects with MPA2, MPA2 will
send proxy Registration Request with no sequence number to HA(step4).
And HA returns back a sequence number 'X+1' in the Registration
Reply. Subsequent registration requests from MPA2 contains the
sequence number 'X+1'. By checking the sequence number in the
registration message, HA knows which registration is new and ignore
stale registrations.
If a malicious node intercepts previous Registration Request from
MPA1, the malicious node can replay the intercepted message to HA
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after MS connecting with MPA2. In this case, HA will be cheated that
it receives a new Registration Request from MPA1 and hence change the
care-of address of MS to IP address of MPA1 even though MS is
connected with MPA2.
Therefore only sequence number cannot prevent Registration Request
from Replay Attack. When a malicious node intercepts previous
registrations and replays it to home agent, home agent will have a
wrong binding for MS.
Even if timestamp is used as sequence number, the problem still
cannot be addressed. Unlike in base Mobile IPv4 in which
Registration Request is generated by MS, it is MPA that generates
Registration Request message. Unless that the machine time in two
MPAs are exactly synchronized, Home Agent doesn't know the sequence
of these registrations from different MPAs. And HA doesn't know
whether a registration message is a replayed message or a valid one.
4. Security Considerations
The security problem when using sequence number for anti-replay
purpose can be addressed by later solutions.
5. References
5.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC3344] Perkins, C., "IP Mobility Support for IPv4", RFC 3344,
August 2002.
[RFC3543] Glass, S. and M. Chandra, "Registration Revocation in
Mobile IPv4", RFC 3543, August 2003.
5.2. Informative References
[Proxy-MIP4]
Leung, K., Dommety, G., and P. Yegani, "Mobility
Management using Proxy Mobile IPv4", February 2006,
<draft-leung-mip4-proxy-mode-00(work in progress)>.
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Authors' Addresses
Shouwen Lai
Hitachi (China)
Beijing Fortune Bldg. 1701
5 Dong San Huan Bei-Lu
Chao Yang District
Beijing 100004
China
Email: swlai@hitachi.cn
Hui Deng
Hitachi (China)
Beijing Fortune Bldg. 1701
5 Dong San Huan Bei-Lu
Chao Yang District
Beijing 100004
China
Email: hdeng@hitachi.cn
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