< draft-ietf-netlmm-threats-03.txt   draft-ietf-netlmm-threats-04.txt >
Network Working Group C. Vogt Network Working Group C. Vogt
Internet-Draft Universitaet Karlsruhe (TH) Internet-Draft Universitaet Karlsruhe (TH)
Expires: February 22, 2007 J. Kempf Expires: March 16, 2007 J. Kempf
DoCoMo USA Labs DoCoMo USA Labs
August 21, 2006 September 12, 2006
Security Threats to Network-Based Localized Mobility Management Security Threats to Network-Based Localized Mobility Management
draft-ietf-netlmm-threats-03.txt draft-ietf-netlmm-threats-04.txt
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Abstract Abstract
This document discusses security threats to network-based localized This document discusses security threats to network-based localized
mobility management. Threats may occur on two interfaces: the mobility management. Threats may occur on two interfaces: the
interface between an LMA and a MAG, as well as the interface between interface between a localized mobility anchor and a mobile access
a MAG and a mobile node. Threats to the former interface impact the gateway, as well as the interface between a mobile access gateway and
localized mobility management protocol itself. a mobile node. Threats to the former interface impact the localized
mobility management protocol itself.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . 4 1.1 Terminology . . . . . . . . . . . . . . . . . . . . . . . 4
2. Threats to Interface between LMA and MAG . . . . . . . . . . . 4 2. Threats to Interface between LMA and MAG . . . . . . . . . . . 4
2.1 LMA Compromise or Impersonation . . . . . . . . . . . . . 4 2.1 LMA Compromise or Impersonation . . . . . . . . . . . . . 4
2.2 MAG Compromise or Impersonation . . . . . . . . . . . . . 5 2.2 MAG Compromise or Impersonation . . . . . . . . . . . . . 5
2.3 Man in the Middle Attack . . . . . . . . . . . . . . . . . 7 2.3 Man in the Middle Attack . . . . . . . . . . . . . . . . . 7
3. Threats to Interface between MAG and Mobile Node . . . . . . . 8 3. Threats to Interface between MAG and Mobile Node . . . . . . . 7
3.1 Mobile Node Compromise or Impersonation . . . . . . . . . 8 3.1 Mobile Node Compromise or Impersonation . . . . . . . . . 8
3.2 Man in the Middle Attack . . . . . . . . . . . . . . . . . 10 3.2 Man in the Middle Attack . . . . . . . . . . . . . . . . . 10
4. Threats from the Internet . . . . . . . . . . . . . . . . . . 10 4. Threats from the Internet . . . . . . . . . . . . . . . . . . 10
5. Security Considerations . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . . 11
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 12 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 11
7. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 12 7. Acknowledgment . . . . . . . . . . . . . . . . . . . . . . . . 11
8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 13 8. References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
8.1 Normative References . . . . . . . . . . . . . . . . . . . 13 8.1 Normative References . . . . . . . . . . . . . . . . . . . 12
8.2 Informative References . . . . . . . . . . . . . . . . . . 13 8.2 Informative References . . . . . . . . . . . . . . . . . . 12
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 14 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 13
A. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 14 A. Change Log . . . . . . . . . . . . . . . . . . . . . . . . . . 13
Intellectual Property and Copyright Statements . . . . . . . . 17 Intellectual Property and Copyright Statements . . . . . . . . 16
1. Introduction 1. Introduction
The network-based localized mobility management (NETLMM) architecture The network-based localized mobility management (NETLMM) architecture
[1] supports movement of IPv6 mobile nodes locally within a domain [1] supports movement of IPv6 mobile nodes locally within a domain
without requiring mobility support in the mobile nodes' network without requiring mobility support in the mobile nodes' network
stacks. A mobile node can keep its IP address constant as it moves stacks. A mobile node can keep its IP address constant as it moves
from link to link, avoiding the signaling overhead and latency from link to link, avoiding the signaling overhead and latency
associated with changing the IP address. While software specifically associated with changing the IP address. Software specifically for
for localized mobility management is not required on the mobile node, localized mobility management is not required on the mobile node,
IP-layer movement detection software may be necessary, and driver whereas IP-layer movement detection software may be necessary, and
software for link-layer mobility is prerequisite. driver software for link-layer mobility is prerequisite.
The IP addresses of mobile nodes have a prefix that routes to a The IP addresses of mobile nodes have a prefix that routes to a
localized mobility anchor (LMA). The LMA maintains an individual localized mobility anchor (LMA) [3]. The LMA maintains an individual
route for each registered mobile node. Any particular mobile node's route for each registered mobile node. Any particular mobile node's
route terminates at a mobile access gateway (MAG) which the mobile route terminates at a mobile access gateway (MAG) [3], to which the
node uses as a default router on its current access link. MAGs are mobile node attaches at its current access link. MAGs are
responsible for updating the mobile node's route on the LMA as the responsible for updating the mobile node's route on the LMA as the
mobile node moves. A MAG detects the arrival of a mobile node on its mobile node moves. A MAG detects the arrival of a mobile node on its
local access link based on handoff signaling that the mobile node local access link based on handoff signaling that the mobile node
pursues. The MAG may additionally monitor connectivity of the mobile pursues. The MAG may additionally monitor connectivity of the mobile
node in order to recognize when the mobile node has left the local node in order to recognize when the mobile node has left the local
access link. The localized mobility management architecture access link. The localized mobility management architecture
therefore has two interfaces: therefore has two interfaces:
1. The interface between a MAG and an LMA where route update 1. The interface between a MAG and an LMA where route update
signaling occurs. signaling occurs.
2. The interface between a mobile node and its current MAG where 2. The interface between a mobile node and its current MAG where
handoff signaling and other link maintenance signaling occurs. handoff signaling and other link maintenance signaling occurs.
The localized mobility management architecture specifies no The localized mobility management architecture demands no specific
standardized protocol for a MAG to detect the arrival or departure of protocol for a MAG to detect the arrival or departure of mobile nodes
mobile nodes on its local link and accordingly initiate route update to and from its local access link and accordingly initiate route
signaling with the LMA. An appropriate mechanism may be entirely update signaling with an LMA. An appropriate mechanism may be
implemented at the link layer, such as is common for cellular entirely implemented at the link layer, such as is common for
networks. In that case, the IP layer never detects any movement, cellular networks. In that case, the IP layer never detects any
even when a mobile node moves from one link to another handled by a movement, even when a mobile node moves from one link to another
different MAG. If the link layer does not provide the necessary handled by a different MAG. If the link layer does not provide the
functionality, the mobile node must perform active IP-layer movement necessary functionality, the mobile node must perform IP-layer
detection signaling so as to trigger route update signaling at the movement detection and auto-configuration signaling, thereby
MAG. In either case, the decisive handoff signaling is bound to a providing the trigger for the MAG to update its route at the LMA. A
mobile node identity, which is established when the mobile node mobile node identity, established by the localized mobility
initially connects to the domain. For some wireless access management domain when the mobile node initially connects and
technologies, the mobile node identity may have to be re-established authenticates, enables the MAG to ascribe the decisive link- or IP-
on every link-layer handoff. layer signaling to the correct mobile node. Some wireless access
technologies may require the mobile node identity to be re-
established on every link-layer handoff.
Vulnerabilities in either interface of the localized mobility Vulnerabilities in either interface of the localized mobility
management architecture may entail new security threats which go management architecture may entail new security threats which go
beyond those that already exist in IPv6. Potential attack objectives beyond those that already exist in IPv6. This document identifies
may be to roam at the cost of a legitimate mobile node, interpose in and discusses security threats on both interfaces of the localized
a mobile node's communications from a position off link, or cause mobility management architecture. It is limited to threats which are
denial of service to a mobile node or to the localized mobility peculiar to localized mobility management; threats to IPv6 in general
management domain as a whole. This document identifies and discusses are documented in [4].
security threats on both interfaces of the localized mobility
management architecture. It is limited to threats which are peculiar
to localized mobility management; threats to IPv6 in general are
documented in [3].
1.1 Terminology 1.1 Terminology
The terminology in this document follows the definitions in [2], with The terminology in this document follows the definitions in [2], with
those revisions and additions from [1]. In addition, the following those revisions and additions from [1]. In addition, the following
definition is used: definition is used:
Mobile node identity Mobile Node Identity
An identity established for the mobile node when initially An identity established for the mobile node when initially
connecting to the domain. It allows the localized mobility connecting to the domain. It allows the localized mobility
management domain to definitively and unambiguously identify the management domain to definitively and unambiguously identify the
mobile node upon handoff for route update signaling purposes. The mobile node upon handoff for route update signaling purposes. The
mobile node identity is conceptually independent of the mobile mobile node identity is conceptually independent of the mobile
node's IP or link-layer addresses, but it must be securely bound node's IP or link-layer addresses, but it must be securely bound
to the mobile node's handoff signaling. to the mobile node's handoff signaling.
2. Threats to Interface between LMA and MAG 2. Threats to Interface between LMA and MAG
The localized mobility management protocol executed on the interface The localized mobility management protocol executed on the interface
between an LMA and a MAG serves to establish, update, and tear down between an LMA and a MAG serves to establish, update, and tear down
routes for data plane traffic of mobile nodes. Threats to this routes for data plane traffic of mobile nodes. Threats to this
interface can be separated into compromise or impersonation of a interface can be separated into compromise or impersonation of a
legitimate LMA, compromise or impersonation of a legitimate MAG, and legitimate LMA, compromise or impersonation of a legitimate MAG, and
man-in-the-middle attacks. man-in-the-middle attacks.
2.1 LMA Compromise or Impersonation 2.1 LMA Compromise or Impersonation
A compromised LMA can ignore routing updates from a legitimate MAG, A compromised LMA can ignore route updates from a legitimate MAG in
or forge routing updates for a victim mobile node in order to order to deny service to a mobile node. It may also be able to trick
redirect or deny the mobile node's traffic. Since data plane traffic a legitimate MAG into creating a new, incorrect route, thereby
preparing the MAG to receive redirected traffic of a mobile node; it
may cause the traffic forwarded by a MAG to be redirected to a
different LMA; or it may simply have the MAG drop an existing route
in order to deny the mobile node service. Since data plane traffic
for mobile nodes routes through the LMA, a compromised LMA can also for mobile nodes routes through the LMA, a compromised LMA can also
intercept, inspect, modify, redirect, or drop such traffic on a MAG intercept, inspect, modify, or drop such traffic, or redirect it to a
supported by the LMA. The attack can be conducted transiently, to destination in collusion with the attacker. The attack can be
selectively disable traffic for any particular mobile node or MAG at conducted transiently, to selectively disable traffic for any
particular times. particular mobile node or MAG at particular times.
Moreover, a compromised LMA may manipulate its routing table such Moreover, a compromised LMA may manipulate its routing table such
that all packets are directed towards a single MAG. This may result that all packets are directed towards a single MAG. This may result
in a DoS attack against that MAG and its attached link. in a DoS attack against that MAG and its attached access link.
These threats also emanate from an attacker which tricks a MAG into These threats also emanate from an attacker which tricks a MAG into
believing that it is a legitimate LMA. This attacker can cause the believing that it is a legitimate LMA. This attacker can cause the
MAG to conduct route update signaling with the attacker instead of MAG to conduct route update signaling with the attacker instead of
with the legitimate LMA, enabling it to ignore route updates from the with the legitimate LMA, enabling it to ignore route updates from the
MAG, or forge route updates in order to redirect or deny a victim MAG, or induce incorrect route changes at the MAG as described above,
mobile node's traffic. The attacker does not necessarily have to be in order to redirect or deny a mobile node's traffic. The attacker
on the original control plane path between the legitimate LMA and the does not necessarily have to be on the original control plane path
MAG, provided that it can somehow make its presence known to the MAG. between the legitimate LMA and the MAG, provided that it can somehow
E.g., the IP address of a mobility anchor point in hierarchical make its presence known to the MAG. Failure to mutually authenticate
Mobile IPv6 mobility management [4] may be proliferated across a when establishing an association between an LMA and a MAG would allow
domain hop by hop in Router Advertisement messages. Failure to an attacker to establish itself as a rogue LMA.
properly authenticate a comparable mechanism for localized mobility
management would allow an attacker to establish itself as a rogue
LMA.
The attacker may further be able to intercept, inspect, modify, The attacker may further be able to intercept, inspect, modify, drop,
redirect, or drop data plane traffic to and from a mobile node. This or redirect data plane traffic to and from a mobile node. This is
is obvious if the attacker is on the original data plane path between obvious if the attacker is on the original data plane path between
the legitimate LMA and the mobile node's current MAG, which may the legitimate LMA and the mobile node's current MAG, which may
happen independent of whether or not the attacker is on the original happen independently of whether the attacker is on the original
control plane path. If the attacker is not on this path, it may be control plane path. If the attacker is not on this path, it may be
able to leverage the localized mobility management protocol to able to leverage the localized mobility management protocol to
redefine the prefix that the mobile node uses in IP address redefine the prefix that the mobile node uses in IP address
configuration. The attacker can then specify a prefix that routes to configuration. The attacker can then specify a prefix that routes to
itself. Whether or not outgoing data plane packets sourced by the itself. Whether or not outgoing data plane packets sourced by the
mobile node can be interfered with by an attacker off the original mobile node can be interfered with by an attacker off the original
data plane path depends on the specific data plane forwarding data plane path depends on the specific data plane forwarding
mechanism within the localized mobility management domain. E.g., if mechanism within the localized mobility management domain. E.g., if
IP-in-IP encapsulation or an equivalent per-mobile-node approach is IP-in-IP encapsulation or an equivalent approach is used for outbound
used for outbound data plane packets, the packets will route through data plane packets, the packets can be forced to be routed through
the attacker. On the other hand, standard IP routing may cause the the attacker. On the other hand, standard IP routing may cause the
packets to be relayed via the legitimate LMA and hence to circumvent packets to be relayed via a legitimate LMA and hence to circumvent
the attacker. the attacker.
2.2 MAG Compromise or Impersonation 2.2 MAG Compromise or Impersonation
A compromised MAG can redirect a victim mobile node's traffic onto A compromised MAG can redirect a mobile node's traffic onto its local
its local access link arbitrarily, without authorization from the access link arbitrarily, without authorization from the mobile node.
mobile node. This threat is similar to an attack on a typical This threat is similar to an attack on a typical routing protocol
routing protocol where a malicious stub router injects a bogus host where a malicious stub router injects a bogus host route for the
route for the mobile node. In general, forgery of a subnet prefix in mobile node. In general, forgery of a subnet prefix in link state or
link state or distance vector routing protocols requires support of distance vector routing protocols requires support of multiple
multiple routers in order to obtain a meaningful change in forwarding routers in order to obtain a meaningful change in forwarding
behavior. But a bogus host route is likely to take precedence over behavior. But a bogus host route is likely to take precedence over
the routing information advertised by legitimate routers, which is the routing information advertised by legitimate routers, which is
usually less specific, hence the attack should succeed even if the usually less specific, hence the attack should succeed even if the
attacker is not supported by other routers. A difference between attacker is not supported by other routers. A difference between
redirection in a routing protocol and redirection in localized redirection in a routing protocol and redirection in localized
mobility management is that the former impacts the routing tables of mobility management is that the former impacts the routing tables of
multiple routers, whereas the latter involves only the compromised multiple routers, whereas the latter involves only the compromised
MAG and an LMA. MAG and an LMA.
Moreover, a compromised MAG can ignore the presence of a mobile node Moreover, a compromised MAG can ignore the presence of a mobile node
on its local access link and refrain from registering the mobile node on its local access link and refrain from registering the mobile node
at an LMA. The mobile node then loses its traffic. The compromised at an LMA. The mobile node then loses its traffic. The compromised
MAG may further be able to cause interruption to a mobile node by MAG may further be able to cause interruption to a mobile node by
deregistering the mobile node at the LMA, pretending that the mobile deregistering the mobile node at the serving LMA, pretending that the
node has powered down. The mobile node then needs to reinitiate the mobile node has powered down. The mobile node then needs to re-
network access authentication procedure, which the compromised MAG initiate the network access authentication procedure, which the
may prevent repeatedly until the mobile node moves to a different compromised MAG may prevent repeatedly until the mobile node moves to
MAG. The mobile node should be able to handle this situation, but a different MAG. The mobile node should be able to handle this
the recovery process may be lengthy and hence impair ongoing situation, but the recovery process may be lengthy and hence impair
communication sessions to a significant extent. ongoing communication sessions to a significant extent.
Attacks that the MAG can mount on its access link interface are
common for any regular IPv6 access router [3].
Denial of service against an LMA is another threat of MAG subversion. Denial of service against an LMA is another threat of MAG subversion.
The compromised MAG can trick the LMA into believing that a high The compromised MAG can trick an LMA into believing that a high
number of mobile nodes have attached to the MAG. The LMA will then number of mobile nodes have attached to the MAG. The LMA will then
establish a routing table entry for each of the non-existing mobile establish a routing table entry for each of the non-existing mobile
nodes. The unexpected growth of the routing table may eventually nodes. The unexpected growth of the routing table may eventually
cause the LMA to reject legitimate route update requests. It may cause the LMA to reject legitimate route update requests. It may
also decrease the forwarding speed for data plane packets due to also decrease the forwarding speed for data plane packets due to
higher route lookup latencies, and it may for the same reason slow higher route lookup latencies, and it may for the same reason slow
down the responsiveness to control plane packets. Another adverse down the responsiveness to control plane packets. Another adverse
side effect of a high number of routing table entries is that the side effect of a high number of routing table entries is that the
LMA, and hence the localized mobility management domain as a whole, LMA, and hence the localized mobility management domain as a whole,
becomes more susceptible to flooding packets from external attackers becomes more susceptible to flooding packets from external attackers
(see Section 4). The high number of superfluous routes increases the (see Section 4). The high number of superfluous routes increases the
probability that a flooding packet, sent to a random IP address probability that a flooding packet, sent to a random IP address
within the localized mobility management domain, matches an existing within the localized mobility management domain, matches an existing
routing table entry at the LMA and gets tunneled to a MAG, which in routing table entry at the LMA and gets tunneled to a MAG, which in
turn performs address resolution [5] on the local access link. At turn performs address resolution on the local access link. At the
the same time, fewer flooding packets can be dropped directly at the same time, fewer flooding packets can be dropped directly at the LMA
LMA due to a nonexistent routing table entry. on the basis of a nonexistent routing table entry.
All of these threats apply not just to a MAG that is compromised, but All of these threats apply not just to a MAG that is compromised, but
also to an attacker that manages to counterfeit the identity of an also to an attacker that manages to counterfeit the identity of a
authorized MAG in interacting with both mobile nodes and an LMA. legitimate MAG in interacting with both mobile nodes and an LMA.
Such an attacker can behave towards mobile nodes like a legitimate Such an attacker can behave towards mobile nodes like an authorized
MAG and engage an LMA in route update signaling. In a related MAG and engage an LMA in route update signaling. In a related
attack, the perpetrator eavesdrops on signaling packets exchanged attack, the perpetrator eavesdrops on signaling packets exchanged
between an authorized MAG and an LMA and replays these packets at a between a legitimate MAG and an LMA and replays these packets at a
later time. These attacks may be conducted transiently, to later time. These attacks may be conducted transiently, to
selectively disable traffic for any particular mobile node at selectively disable traffic for any particular mobile node at
particular times. particular times.
2.3 Man in the Middle Attack 2.3 Man in the Middle Attack
An attacker that manages to interject itself between a legitimate LMA An attacker that manages to interject itself between a legitimate LMA
and a legitimate MAG can act as a man in the middle with respect to and a legitimate MAG can act as a man in the middle with respect to
both control plane signaling and data plane traffic. If the attacker both control plane signaling and data plane traffic. If the attacker
is on the original control plane path, it can forge, modify, or drop is on the original control plane path, it can forge, modify, or drop
route update packets so as to cause the establishment of incorrect route update packets so as to cause the establishment of incorrect
routes or the removal of routes that are in active use. Similarly, routes or the removal of routes that are in active use. Similarly,
an attacker on the original data plane path can intercept, inspect, an attacker on the original data plane path can intercept, inspect,
modify, redirect, and drop data plane packets sourced by or destined modify, drop, and redirect data plane packets sourced by or destined
to a victim mobile node. to a mobile node.
A compromised router located between an LMA and a MAG may cause A compromised switch or router located between an LMA and a MAG can
similar damage. Any router on the control plane path can forge, cause similar damage. Any switch or router on the control plane path
modify, or drop control plane packets, and thereby interfere with can forge, modify, or drop control plane packets, and thereby
route establishment. Any router on the data plane path can interfere with route establishment. Any switch or router on the data
intercept, inspect, modify, and drop data plane packets, or rewrite plane path can intercept, inspect, modify, and drop data plane
IP headers so as to divert the packets from their original path. packets, or rewrite IP headers so as to divert the packets from their
original path.
An attacker between an LMA and a MAG may further impersonate the MAG An attacker between an LMA and a MAG may further impersonate the MAG
towards the LMA and vice versa in route update signaling. The towards the LMA and vice versa in route update signaling. The
attacker can so interfere with route establishment even if it is not attacker can so interfere with route establishment even if it is not
on the original control plane path between the LMA and the MAG. An on the original control plane path between the LMA and the MAG. An
attacker off the original data plane path may undertake the same to attacker off the original data plane path may undertake the same to
cause inbound data plane packets destined to the mobile node to be cause inbound data plane packets destined to the mobile node to be
routed first from the LMA to the attacker, and from there to the routed first from the LMA to the attacker, and from there to the
mobile node's MAG and finally to the mobile node itself. As mobile node's MAG and finally to the mobile node itself. As
explained in Section 2.1, here, too, it depends on the specific data explained in Section 2.1, here, too, it depends on the specific data
plane forwarding mechanism within the localized mobility management plane forwarding mechanism within the localized mobility management
domain whether or not the attacker can influence the route of domain whether or not the attacker can influence the route of
outgoing data plane packets sourced by the mobile node. outgoing data plane packets sourced by the mobile node.
3. Threats to Interface between MAG and Mobile Node 3. Threats to Interface between MAG and Mobile Node
A MAG monitors the mobile nodes' link-layer handoff signaling or IP- A MAG monitors the arrival and departure of mobile nodes to and from
layer movement detection signaling in order to detect the arrival and its local access link based on link- or IP-layer mechanisms.
departure of mobile nodes and accordingly initiate route updates with Whatever signaling on the access link is thereby decisive must be
the LMA. Cellular access technologies utilize only the signaling at securely bound to the mobile node identity. A MAG uses this binding
the wireless link layer, and the IP stack never sees any change when to ascribe the signaling to the mobile node and accordingly initiate
the mobile node moves from one MAG to a MAG on a different link. For route update signaling with an LMA. The binding must be robust to
non-cellular access technologies, such as IEEE 802.11 or wired spoofing because it would otherwise facilitate impersonation of the
Ethernet, the link-layer signaling may not hide a handoff from the IP mobile node by a third party, denial of service, or man-in-the-middle
layer. Instead, IP-layer movement detection signaling may have to be attacks.
performed in response to a notification from the link layer that a
change in link-layer attachment has occurred. This signaling may
involve extensions [6] for IPv6 Neighbor Discovery [5], DHCPv6 [7],
or additional technology-specific functionality at the IP layer.
Although the mobile node identity is conceptually independent of the
mobile node's IP or link-layer addresses in either case, it must be
securely bound to whatever handoff signaling of the mobile node is
decisive for route updates on the MAG-LMA interface, be it via an
address or otherwise. A MAG uses this binding to deduce when the
mobile node has handed over onto the MAG's local access link, and
possibly when the mobile node leaves the local access link again,
thereby providing the trigger for route update signaling to an LMA.
The binding must be robust to spoofing because it would otherwise
facilitate impersonation of the mobile node by a third party, denial
of service, or man-in-the-middle attacks.
3.1 Mobile Node Compromise or Impersonation 3.1 Mobile Node Compromise or Impersonation
An attacker that is able to forge the mobile node identity of a An attacker that is able to forge the mobile node identity of a
neighboring victim mobile node may be able to trick its MAG into mobile node can to trick a MAG into redirecting data plane packets
redirecting the mobile node's packets to itself. Such an on-link for the mobile node to the attacker. The attacker can launch such an
attack is common for any regular IPv6 network [3]. However, if impersonation attack against a mobile node that resides on the same
handoff signaling cannot definitively and unambiguously be linked link as the attacker, or against a mobile node on a different link.
back to the legitimate mobile node identity, an attacker may further If the attack is on-link, the redirection of packets from the mobile
be capable of fabricating handoff signaling of a victim mobile node node to the attacker is internal to the MAG, and it involves no route
that currently attaches to a different link. The attacker can thus update signaling between the MAG and an LMA. On-link attacks are
trick its MAG into believing that the mobile node has handed over possible in a regular IPv6 network [4] that does not use Secure
onto the MAG's access link. The MAG will then initiate route update Neighbor Discovery [5].
signaling to an LMA, causing the LMA to redirect inbound data plane
packets for the mobile node to the attacker's MAG and finally to the
attacker itself. The attacker can so examine the packets that
legitimately belong to the mobile node, or discard the packets in
order to deny the mobile node service. The same can happen if a MAG
accepts from the attacker replayed handoff signaling packets which
the attacker has previously recorded from the legitimate mobile node.
The above attack is conceivable both if the attacker and the mobile Off-link impersonation requires the attacker to fabricate handoff
node are on links that connect to different MAGs, as well as if they signaling of the mobile node and thus trick the MAG into believing
are on separate links connecting to the same MAG. In the former that the mobile node has handed over onto the MAG's access link. The
case, two MAGs would think they see the mobile node and both would attack is conceivable both if the attacker and the mobile node are on
independently perform route update signaling with the LMA. In the separate links that connect to different MAGs, as well as if they are
latter case, route update signaling is likely to be performed only on separate, possibly virtual per-mobile-node links that connect to
once, and the redirection of packets from the mobile node to the the same MAG. In the former case, two MAGs would think they see the
attacker is internal to the MAG. The mobile node can always mobile node and both would independently perform route update
recapture its traffic back from the attacker through another run of signaling with the LMA. In the latter case, route update signaling
handoff signaling. But standard mobile nodes are generally not is likely to be performed only once, and the redirection of packets
prepared to counteract this kind of attack, and even where network from the mobile node to the attacker is internal to the MAG. The
stacks include suitable functionality, the attack may not be mobile node can always recapture its traffic back from the attacker
noticeable early enough at the link or IP layer to quickly institute through another run of handoff signaling. But standard mobile nodes
countermeasures. The attack is therefore disruptive at a minimum, are generally not prepared to counteract this kind of attack, and
and may potentially persist until the mobile node initiates signaling even where network stacks include suitable functionality, the attack
again upon a subsequent handoff. may not be noticeable early enough at the link or IP layer to quickly
institute countermeasures. The attack is therefore disruptive at a
minimum, and may potentially persist until the mobile node initiates
signaling again upon a subsequent handoff.
Off-link impersonation attacks can be prevented at the link layer. Impersonation attacks can be prevented at the link layer,
E.g., they are not possible with cellular access technologies, where particularly with cellular technologies where the handoff signaling
the handoff signaling is completely controlled by the wireless link between the mobile node and the network must be authenticated and is
layer. Here, an attacker must be on the same link as the victim completely controlled by the wireless link layer. Cellular access
mobile node in order to disrupt the negotiation between the mobile technologies provide a variety of cryptographic and non-cryptographic
node and the network. Cellular access technologies also provide attack barriers at the link layer which make mouting an impersonation
other cryptographic and non-cryptographic attack barriers at the link attack, both on-link and off-link, very difficult. However, for non-
layer, which make mounting an impersonation attack, both on-link and cellular technologies that do not require link layer authentication
off-link, very difficult. For non-cellular access technologies, and authorization during handoff, impersonation attacks may be
however, off-link impersonation attacks may be possible. possible.
An attacker which can forge handoff signaling messages may also cause An attacker that can forge handoff signaling may also cause denial of
denial of service against the localized mobility management domain. service against the localized mobility management domain. The
The attacker can trick a MAG into believing that a large number of attacker can trick a MAG into believing that a large number of mobile
mobile nodes have attached to the local access link and thus induce nodes have attached to the local access link and thus induce it to
it to initiate route update signaling with an LMA for each mobile initiate route update signaling with an LMA for each mobile node
node assumed on link. The result of such an attack is both assumed on link. The result of such an attack is both superfluous
superfluous signaling overhead on the control plane as well as a high signaling overhead on the control plane as well as a high number of
number of needless entries in the LMA's and MAG's routing tables. needless entries in the LMA's and MAG's routing tables. The
The unexpected growth of the routing tables may eventually cause the unexpected growth of the routing tables may eventually cause the LMA
LMA to reject legitimate route update requests, and it may cause the to reject legitimate route update requests, and it may cause the MAG
MAG to ignore handoffs of legitimate mobile nodes on its local access to ignore handoffs of legitimate mobile nodes onto its local access
link. It may also decrease the LMA's and MAG's forwarding speed for link. It may also decrease the LMA's and MAG's forwarding speed for
inbound and outbound data plane packets due to higher route lookup inbound and outbound data plane packets due to higher route lookup
latencies, and it may for the same reason slow down their latencies, and it may for the same reason slow down their
responsiveness to control plane packets. An adverse side effect of responsiveness to control plane packets. An adverse side effect of
this attack is that the LMA, and hence the localized mobility this attack is that the LMA, and hence the localized mobility
management domain as a whole, becomes more susceptible to flooding management domain as a whole, becomes more susceptible to flooding
packets from external attackers (see Section 4). The high number of packets from external attackers (see Section 4). The high number of
superfluous routes increases the probability that a flooding packet, superfluous routes increases the probability that a flooding packet,
sent to a random IP address within the localized mobility management sent to a random IP address within the localized mobility management
domain, matches an existing routing table entry at the LMA and gets domain, matches an existing routing table entry at the LMA and gets
tunneled to a MAG, which in turn performs address resolution [5] on tunneled to a MAG, which in turn performs address resolution on the
the local access link. At the same time, fewer flooding packets can local access link. At the same time, fewer flooding packets can be
be dropped directly at the LMA due to a nonexistent routing table dropped directly at the LMA on the basis of a nonexistent routing
entry. table entry.
A threat related to the ones identified above, but not limited to A threat related to the ones identified above, but not limited to
handoff signaling, is IP spoofing [8][9]. Attackers use IP spoofing handoff signaling, is IP spoofing [6]. Attackers use IP spoofing
mostly for reflection attacks or to hide their identities. The mostly for reflection attacks or to hide their identities. The
threat can be reasonably contained by a wide deployment of network threat can be reasonably contained by a wide deployment of network
ingress filtering [10] in access network routers. This technique ingress filtering [7] in routers, especially within access networks.
prevents IP spoofing to the extent that it ensures topological This technique prevents IP spoofing to the extent that it ensures
correctness of IP source address prefixes in to-be-forwarded packets. topological correctness of IP source address prefixes in to-be-
Where the technique is deployed in an access router, packets are forwarded packets. Where the technique is deployed in an access
forwarded only if the prefix of their IP source address is valid on router, packets are forwarded only if the prefix of their IP source
the router's local access link. An attacker can still use a false address is valid on the router's local access link. An attacker can
interface identifier in combination with an on-link prefix. But still use a false interface identifier in combination with an on-link
since reflection attacks typically aim at off-link targets, and the prefix. But since reflection attacks typically aim at off-link
enforcement of topologically correct IP address prefixes also limits targets, and the enforcement of topologically correct IP address
the effectiveness of identity concealment, network ingress filtering prefixes also limits the effectiveness of identity concealment,
has proven adequate so far. On the other hand, prefixes are not network ingress filtering has proven adequate so far. On the other
limited to a specific link in a localized mobility management domain, hand, prefixes are not limited to a specific link in a localized
so an attacker may be able to send packets with an off-link IP source mobility management domain, so merely ensuring topological
address despite the presence of network ingress filtering. This correctness through ingress filtering becomes insufficient. An
could make IP spoofing again more attractive. additional mechanism for IP address ownership verification is
necessary to prevent an attacker from sending packets with an off-
link IP source address.
3.2 Man in the Middle Attack 3.2 Man in the Middle Attack
An attacker which can interpose between a victim mobile node and a An attacker which can interpose between a mobile node and a MAG
MAG during handoff signaling, router discovery, and IP address during link- and/or IP-layer handoff signaling may be able to mount a
configuration can mount a man-in-the-middle attack on the mobile man-in-the-middle attack on the mobile node, spoofing the mobile node
node, spoofing the mobile node into believing that it has a into believing that it has a legitimate connection with the localized
legitimate connection with the localized mobility management domain. mobility management domain. The attacker can thus intercept,
The attacker can thus intercept, inspect, modify, or selectively drop inspect, modify, or drop data plane packets sourced by or destined to
packets sourced by or destined to the mobile node. the mobile node.
4. Threats from the Internet 4. Threats from the Internet
A localized mobility management domain uses host routes for data A localized mobility management domain uses individual host routes
plane traffic and hence deviates from the standard IPv6 longest- for data plane traffic of different mobile nodes, each between an LMA
prefix-match routing. Creation, maintenance, and deletion of tese and a MAG. Creation, maintenance, and deletion of these routes cause
host routes in addition cause control traffic within the localized control traffic within the localized mobility management domain.
mobility management domain. These characteristics are transparent to These characteristics are transparent to mobile nodes as well as
mobile nodes as well as external correspondent nodes, but the external correspondent nodes, but the functional differences within
functional differences within the domain may influence the impact the domain may influence the impact that a denial-of-service attack
that a denial-of-service attack from the outside world can have on from the outside world can have on the domain.
the domain.
A denial-of-service attack on an LMA may be launched by sending A denial-of-service attack on an LMA may be launched by sending
packets to arbitrary IP addresses which are potentially in use by packets to arbitrary IP addresses that are potentially in use by
mobile nodes within the localized mobility management domain. Like a mobile nodes within the localized mobility management domain. Like a
border router, the LMA is in a topological position through which a border router, the LMA is in a topological position through which a
substantial amount of data plane traffic goes, so it must process the substantial amount of data plane traffic goes, so it must process the
flooding packets and perform a routing table lookup for each of them. flooding packets and perform a routing table lookup for each of them.
The LMA can discard packets for which the IP destination address is The LMA can discard packets for which the IP destination address is
not registered in its routing table. But other packets must be not registered in its routing table. But other packets must be
encapsulated and forwarded. A target MAG as well as any mobile nodes encapsulated and forwarded. A target MAG as well as any mobile nodes
attached to the MAG's local access link are also likely to suffer attached to that MAG's local access link are also likely to suffer
damage because the unrequested packets must be decapsulated and damage because the unrequested packets must be decapsulated and
consume link bandwidth as well as processing capacities on the consume link bandwidth as well as processing capacities on the
receivers. This threat is in principle the same as for denial of receivers. This threat is in principle the same as for denial of
service on a regular IPv6 border router, but because either the service on a regular IPv6 border router, but because the routing
routing table lookup enables the LMA to drop a flooding packet early table lookups may enable the LMA to drop part of the flooding packets
on or, on the contrary, additional tunneling workload is required, early on or, on the contrary, additional tunneling workload is
the impact of an attack against localized mobility management may be required for packets that cannot be dropped, the impact of an attack
different. against localized mobility management may be different.
In a related attack, the villain manages to obtain a globally In a related attack, the attacker manages to obtain a globally
routable IP address of an LMA or a different network entity within routable IP address of an LMA or a different network entity within
the localized mobility management domain and perpetrates a denial-of- the localized mobility management domain and perpetrates a denial-of-
service attack against that IP address. Localized mobility service attack against that IP address. Localized mobility
management is in general somewhat resistant to such an attack because management is in general somewhat resistant to such an attack because
mobile nodes need never obtain a globally routable IP address of any mobile nodes need never obtain a globally routable IP address of any
entity within the localized mobility management domain. A entity within the localized mobility management domain. A
compromised mobile node hence cannot pass such an IP address off to a compromised mobile node hence cannot pass such an IP address off to a
remote attacker, limiting the feasibility of extracting information remote attacker, limiting the feasibility of extracting information
on the topology of the localized mobility management domain. It is on the topology of the localized mobility management domain. It is
still possible for an attacker to perform IP address scanning if MAGs still possible for an attacker to perform IP address scanning if MAGs
and LMAs have globally routable IP addresses, but the much larger and LMAs have globally routable IP addresses, but the much larger
IPv6 address space makes scanning considerably more time consuming. IPv6 address space makes scanning considerably more time consuming.
5. Security Considerations 5. Security Considerations
This document describes threats to network-based localized mobility This document describes threats to network-based localized mobility
management. These may either occur on the interface between an LMA management. These may either occur on the interface between an LMA
and a MAG, or on the interface between a MAG and a mobile node. and a MAG, or on the interface between a MAG and a mobile node.
Mitigation measures for the threats, as well as the security Mitigation measures for the threats, as well as the security
considerations associated with those measures, are described in the considerations associated with those measures, are described in the
respective protocol specifications [11][12] for the two interfaces. respective protocol specifications [3][8] for the two interfaces.
6. IANA Considerations 6. IANA Considerations
This document has no actions for IANA. This document has no actions for IANA.
7. Acknowledgment 7. Acknowledgment
The authors would like to thank the NETLMM working group, especially The authors would like to thank the NETLMM working group, especially
Jari Arkko, Gregory Daley, Vijay Devarapalli, Lakshminath Dondeti, Jari Arkko, Gregory Daley, Vijay Devarapalli, Lakshminath Dondeti,
Gerardo Giaretta, Wassim Haddad, Andy, Huang, Dirk von Hugo, Julien Gerardo Giaretta, Wassim Haddad, Andy, Huang, Dirk von Hugo, Julien
skipping to change at page 13, line 19 skipping to change at page 12, line 19
[1] Kempf, J., "Problem Statement for Network-based Localized [1] Kempf, J., "Problem Statement for Network-based Localized
Mobility Management", IETF Internet Draft Mobility Management", IETF Internet Draft
draft-ietf-netlmm-nohost-ps-04.txt (work in progress), draft-ietf-netlmm-nohost-ps-04.txt (work in progress),
June 2006. June 2006.
[2] Manner, J. and M. Kojo, "Mobility Related Terminology", [2] Manner, J. and M. Kojo, "Mobility Related Terminology",
IETF Request for Comments 3753, June 2004. IETF Request for Comments 3753, June 2004.
8.2 Informative References 8.2 Informative References
[3] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor [3] Giaretta, G., "NetLMM Protocol", IETF Internet Draft
Discovery (ND) Trust Models and Threats", IETF Request for draft-giaretta-netlmm-dt-protocol-00.txt (work in progress),
Comments 3756, May 2004. June 2006.
[4] Soliman, H., Castelluccia, C., El Malki, K., and L. Bellier,
"Hierarchical Mobile IPv6 Mobility Management (HMIPv6)",
IETF Request for Comments 4140, August 2005.
[5] Narten, T., "Neighbor Discovery for IP version 6 (IPv6)",
IETF Internet Draft draft-ietf-ipv6-2461bis-07.txt (work in
progress), May 2006.
[6] Kempf, J., Narayanan, S., Nordmark, E., Pentland, B., and JH.
Choi, "Detecting Network Attachment in IPv6 Networks (DNAv6)",
IETF Internet Draft draft-ietf-dna-protocol-01.txt (work in
progress), June 2006.
[7] Droms, R., Bound, J., Volz, B., Lemon, T., E., C., and M.
Carney, "Dynamic Host Configuration Protocol for IPv6
(DHCPv6)", IETF Request for Comments 3315, July 2003.
[8] CERT Coordination Center, "CERT Advisory CA-1996-21 TCP SYN
Flooding and IP Spoofing Attacks", September 1996.
[9] CERT Coordination Center, "CERT Advisory CA-1998-01 Smurf IP
Denial-of-Service Attacks", January 1998.
[10] Ferguson, P. and D. Senie, "Network Ingress Filtering: [4] Nikander, P., Kempf, J., and E. Nordmark, "IPv6 Neighbor
Defeating Denial of Service Attacks which employ IP Source Discovery (ND) Trust Models and Threats", IETF Request for
Address Spoofing", IETF Request for Comments 2827, May 2000. Comments 3756, May 2004.
[11] Giaretta, G., "NetLMM Protocol", IETF Internet Draft [5] Arkko, J., Kempf, J., Zill, B., and P. Nikander, "SEcure
draft-giaretta-netlmm-dt-protocol-00.txt (work in progress), Neighbor Discovery (SEND)", IETF Request for Comments 3971,
June 2006. March 2005.
[12] Laganier, J., Narayanan, S., and F. Templin, "Network-based [6] CERT Coordination Center, "CERT Advisory CA-1996-21 TCP SYN
Localized Mobility Management Interface between Mobile Node and Flooding and IP Spoofing Attacks", September 1996.
Access Router", IETF Internet Draft
draft-ietf-netlmm-mn-ar-if-01.txt (work in progress),
June 2006.
[13] Aura, T., "Cryptographically Generated Addresses (CGA)", [7] Ferguson, P. and D. Senie, "Network Ingress Filtering: Defeating
IETF Request for Comments 3972, March 2005. Denial of Service Attacks which employ IP Source Address
Spoofing", IETF Request for Comments 2827, May 2000.
[14] Aboba, B., Beadles, M., Arkko, J., and P. Eronen, "The Network [8] Laganier, J., Narayanan, S., and F. Templin, "Network-based
Access Identifier", IETF Request for Comments 4282, Localized Mobility Management Interface between Mobile Node and
December 2005. Access Router", IETF Internet Draft
draft-ietf-netlmm-mn-ar-if-01.txt (work in progress), June 2006.
Authors' Addresses Authors' Addresses
Christian Vogt Christian Vogt
Institute of Telematics Institute of Telematics
Universitaet Karlsruhe (TH) Universitaet Karlsruhe (TH)
P.O. Box 6980 P.O. Box 6980
76128 Karlsruhe 76128 Karlsruhe
Germany Germany
skipping to change at page 14, line 41 skipping to change at page 13, line 28
181 Metro Drive, Suite 300 181 Metro Drive, Suite 300
San Jose, CA 95110 San Jose, CA 95110
USA USA
Phone: +1 408 451 4711 Phone: +1 408 451 4711
Email: kempf@docomolabs-usa.com Email: kempf@docomolabs-usa.com
Appendix A. Change Log Appendix A. Change Log
The following is a list of technical changes that were made from The following is a list of technical changes that were made from
version 03 to version 04 of the document. Editorial revisions are
not explicitly mentioned.
o Section 2.1: Clarified in first paragraph what it means for a
compromised LMA to "forge routing updates for a victim mobile
node" and what the intention behind such an attack could be.
o Section 2.1: Removed description of how MAP discovery works in
Hierarchical Mobile IPv6.
o Section 3: Introductory text shortened, because (i) it repeated
material from Section 1, and (ii) also described potential link-
layer technologies for access links, which was not within the
scope of this document.
o Section 3.1: Clarified how impersonation of a mobile node may
look like when the attacker attaches to the same MAG as the mobile
node, but to a different link.
o Section 3.1: Revised text on why cellular technologies can
prevent impersonation attacks against mobile nodes at the link
layer.
The following is a list of technical changes that were made from
version 02 to version 03 of the document. Editorial revisions are version 02 to version 03 of the document. Editorial revisions are
not explicitly mentioned. not explicitly mentioned.
o Changed the terminology from "network access identity" to "mobile o Changed the terminology from "network access identity" to "mobile
node identity" as the previous term was frequently confused with node identity" as the previous term was frequently confused with
the different "network access identifier" (NAI). Removed the the different "network access identifier" (NAI). Removed the
special "Network Access Identity" subsection in Section 3. The special "Network Access Identity" subsection in Section 3. The
mobile node identity is now first mentioned in Section 1, which mobile node identity is now first mentioned in Section 1, which
fits well with the nutshell description of the NETLMM fits well with the nutshell description of the NETLMM
architecture. The security requirements of the mobile node architecture. The security requirements of the mobile node
skipping to change at page 15, line 19 skipping to change at page 14, line 31
This makes more sense than a special subsection because the text, This makes more sense than a special subsection because the text,
on one hand, provides the necessary basis to understand the on one hand, provides the necessary basis to understand the
following subsections, while on the other hand, it does not really following subsections, while on the other hand, it does not really
explain an attack itself. explain an attack itself.
o Section 1: Extended the description of conceptual actors in the o Section 1: Extended the description of conceptual actors in the
localized mobility management architecture and added a summary of localized mobility management architecture and added a summary of
potential attack objectives and attack targets. potential attack objectives and attack targets.
o Section 3.1: Granularity of ingress filtering may be coarser in a o Section 3.1: Granularity of ingress filtering may be coarser in a
localized mobility mangement domain. It may also allow off-link localized mobility management domain. It may also allow off-link
IP spoofing since prefixes are not limited to a specific link. IP spoofing since prefixes are not limited to a specific link.
o Section 2.2: The threat of replay attacks was not mentioned in o Section 2.2: The threat of replay attacks was not mentioned in
this section. It was added. this section. It was added.
o Section 3.1: The threat of replay attacks was not mentioned in o Section 3.1: The threat of replay attacks was not mentioned in
this section. It was added. this section. It was added.
o Section 2.2: Causing spurious route updates may lead to DoS o Section 2.2: Causing spurious route updates may lead to DoS
against the localized mobility management domain. This threat was against the localized mobility management domain. This threat was
 End of changes. 52 change blocks. 
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