GENWiki

Premier IT Outsourcing and Support Services within the UK

User Tools

Site Tools


rfc:rfc4593

Network Working Group A. Barbir Request for Comments: 4593 Nortel Category: Informational S. Murphy

                                                          Sparta, Inc.
                                                               Y. Yang
                                                         Cisco Systems
                                                          October 2006
                Generic Threats to Routing Protocols

Status of This Memo

 This memo provides information for the Internet community.  It does
 not specify an Internet standard of any kind.  Distribution of this
 memo is unlimited.

Copyright Notice

 Copyright (C) The Internet Society (2006).

Abstract

 Routing protocols are subject to attacks that can harm individual
 users or network operations as a whole.  This document provides a
 description and a summary of generic threats that affect routing
 protocols in general.  This work describes threats, including threat
 sources and capabilities, threat actions, and threat consequences, as
 well as a breakdown of routing functions that might be attacked
 separately.

Barbir, et al. Informational [Page 1] RFC 4593 Generic Threats to Routing Protocols October 2006

Table of Contents

 1. Introduction ....................................................2
 2. Routing Functions Overview ......................................3
 3. Generic Routing Protocol Threat Model ...........................4
    3.1. Threat Definitions .........................................4
         3.1.1. Threat Sources ......................................4
                3.1.1.1. Adversary Motivations ......................5
                3.1.1.2. Adversary Capabilities .....................5
         3.1.2. Threat Consequences .................................7
                3.1.2.1. Threat Consequence Scope ...................9
                3.1.2.2. Threat Consequence Zone ...................10
                3.1.2.3. Threat Consequence Periods ................10
 4. Generally Identifiable Routing Threat Actions ..................11
    4.1. Deliberate Exposure .......................................11
    4.2. Sniffing ..................................................11
    4.3. Traffic Analysis ..........................................12
    4.4. Spoofing ..................................................12
    4.5. Falsification .............................................13
         4.5.1. Falsifications by Originators ......................13
                4.5.1.1. Overclaiming ..............................13
                4.5.1.2. Misclaiming ...............................16
         4.5.2. Falsifications by Forwarders .......................16
                4.5.2.1. Misstatement ..............................16
         4.6. Interference .........................................17
         4.7. Overload .............................................18
 5. Security Considerations ........................................18
 6. References .....................................................18
    6.1. Normative References ......................................18
 Appendix A. Acknowledgments .......................................20
 Appendix B. Acronyms ..............................................20

1. Introduction

 Routing protocols are subject to threats and attacks that can harm
 individual users or the network operations as a whole.  The document
 provides a summary of generic threats that affect routing protocols.
 In particular, this work identifies generic threats to routing
 protocols that include threat sources, threat actions, and threat
 consequences.  A breakdown of routing functions that might be
 separately attacked is provided.
 This work should be considered a precursor to developing a common set
 of security requirements for routing protocols.  While it is well
 known that bad, incomplete, or poor implementations of routing
 protocols may, in themselves, lead to routing problems or failures or
 may increase the risk of a network's being attacked successfully,
 these issues are not considered here.  This document only considers

Barbir, et al. Informational [Page 2] RFC 4593 Generic Threats to Routing Protocols October 2006

 attacks against robust, well-considered implementations of routing
 protocols, such as those specified in Open Shortest Path First (OSPF)
 [4], Intermediate System to Intermediate System (IS-IS) [5][8], RIP
 [6] and BGP [7].  Attacks against implementation-specific weaknesses
 and vulnerabilities are out of scope for this document.
 The document is organized as follows: Section 2 provides a review of
 routing functions.  Section 3 defines threats.  In Section 4, a
 discussion on generally identifiable routing threat actions is
 provided.  Section 5 addresses security considerations.

2. Routing Functions Overview

 This section provides an overview of common functions that are shared
 among various routing protocols.  In general, routing protocols share
 the following functions:
 o  Transport Subsystem: The routing protocol transmits messages to
    its neighbors using some underlying protocol.  For example, OSPF
    uses IP, while other protocols may run over TCP.
 o  Neighbor State Maintenance: Neighboring relationship formation is
    the first step for topology determination.  For this reason,
    routing protocols may need to maintain state information.  Each
    routing protocol may use a different mechanism for determining its
    neighbors in the routing topology.  Some protocols have distinct
    exchanges through which they establish neighboring relationships,
    e.g., Hello exchanges in OSPF.
 o  Database Maintenance: Routing protocols exchange network topology
    and reachability information.  The routers collect this
    information in routing databases with varying detail.  The
    maintenance of these databases is a significant portion of the
    function of a routing protocol.
 In a routing protocol, there are message exchanges that are intended
 for the control of the state of the protocol.  For example, neighbor
 maintenance messages carry such information.  On the other hand,
 there are messages that are used to exchange information that is
 intended to be used in the forwarding function, for example, messages
 that are used to maintain the database.  These messages affect the
 data (information) part of the routing protocol.

Barbir, et al. Informational [Page 3] RFC 4593 Generic Threats to Routing Protocols October 2006

3. Generic Routing Protocol Threat Model

 The model developed in this section can be used to identify threats
 to any routing protocol.
 Routing protocols are subject to threats at various levels.  For
 example, threats can affect the transport subsystem, where the
 routing protocol can be subject to attacks on its underlying
 protocol.  An attacker may also attack messages that carry control
 information in a routing protocol to break a neighboring (e.g.,
 peering, adjacency) relationship.  This type of attack can impact the
 network routing behavior in the affected routers and likely the
 surrounding neighborhood as well.  For example, in BGP, if a router
 receives a CEASE message, it will break its neighboring relationship
 to its peer and potentially send new routing information to any
 remaining peers.
 An attacker may also attack messages that carry data information in
 order to break a database exchange between two routers or to affect
 the database maintenance functionality.  For example, the information
 in the database must be authentic and authorized.  An attacker who is
 able to introduce bogus data can have a strong effect on the behavior
 of routing in the neighborhood.  For example, if an OSPF router sends
 LSAs with the wrong Advertising Router, the receivers will compute a
 Shortest Path First (SPF) tree that is incorrect and might not
 forward the traffic.  If a BGP router advertises a Network Layer
 Reachability Information (NLRI) that it is not authorized to
 advertise, then receivers might forward that NLRI's traffic toward
 that router and the traffic would not be deliverable.  A Protocol
 Independent Multicast (PIM) router might transmit a JOIN message to
 receive multicast data it would otherwise not receive.

3.1. Threat Definitions

 In [1], a threat is defined as a potential for violation of security,
 which exists when there is a circumstance, capability, action, or
 event that could breach security and cause harm.  Threats can be
 categorized as threat sources, threat actions, threat consequences,
 threat consequence zones, and threat consequence periods.

3.1.1. Threat Sources

 In the context of deliberate attack, a threat source is defined as a
 motivated, capable adversary.  By modeling the motivations (attack
 goals) and capabilities of the adversaries who are threat sources,
 one can better understand what classes of attacks these threats may
 mount and thus what types of countermeasures will be required to deal
 with these attacks.

Barbir, et al. Informational [Page 4] RFC 4593 Generic Threats to Routing Protocols October 2006

3.1.1.1. Adversary Motivations

 We assume that the most common goal of an adversary deliberately
 attacking routing is to cause inter-domain routing to malfunction.  A
 routing malfunction affects data transmission such that traffic
 follows a path (sequence of autonomous systems in the case of BGP)
 other than one that would have been computed by the routing protocol
 if it were operating properly (i.e., if it were not under attack).
 As a result of an attack, a route may terminate at a router other
 than the one that legitimately represents the destination address of
 the traffic, or it may traverse routers other than those that it
 would otherwise have traversed.  In either case, a routing
 malfunction may allow an adversary to wiretap traffic passively, or
 to engage in man-in-the-middle (MITM) active attacks, including
 discarding traffic (denial of service).
 A routing malfunction might be effected for financial gain related to
 traffic volume (vs. the content of the routed traffic), e.g., to
 affect settlements among ISPs.
 Another possible goal for attacks against routing can be damage to
 the network infrastructure itself, on a targeted or wide-scale basis.
 Thus, for example, attacks that cause excessive transmission of
 UPDATE or other management messages, and attendant router processing,
 could be motivated by these goals.
 Irrespective of the goals noted above, an adversary may or may not be
 averse to detection and identification.  This characteristic of an
 adversary influences some of the ways in which attacks may be
 accomplished.

3.1.1.2. Adversary Capabilities

 Different adversaries possess varied capabilities.
 o  All adversaries are presumed to be capable of directing packets to
    routers from remote locations and can assert a false IP source
    address with each packet (IP address spoofing) in an effort to
    cause the targeted router to accept and process the packet as
    though it emanated from the indicated source.  Spoofing attacks
    may be employed to trick routers into acting on bogus messages to
    effect misrouting, or these messages may be used to overwhelm the
    management processor in a router, to effect DoS.  Protection from
    such adversaries must not rely on the claimed identity in routing
    packets that the protocol receives.

Barbir, et al. Informational [Page 5] RFC 4593 Generic Threats to Routing Protocols October 2006

 o  Some adversaries can monitor links over which routing traffic is
    carried and emit packets that mimic data contained in legitimate
    routing traffic carried over these links; thus, they can actively
    participate in message exchanges with the legitimate routers.
    This increases the opportunities for an adversary to generate
    bogus routing traffic that may be accepted by a router, to effect
    misrouting or DoS.  Retransmission of previously delivered
    management traffic (replay attacks) exemplify this capability.  As
    a result, protection from such adversaries ought not to rely on
    the secrecy of unencrypted data in packet headers or payloads.
 o  Some adversaries can effect MITM attacks against routing traffic,
    e.g., as a result of active wiretapping on a link between two
    routers.  This represents the ultimate wiretapping capability for
    an adversary.  Protection from such adversaries must not rely on
    the integrity of inter-router links to authenticate traffic,
    unless cryptographic measures are employed to detect unauthorized
    modification.
 o  Some adversaries can subvert routers, or the management
    workstations used to control these routers.  These Byzantine
    failures represent the most serious form of attack capability in
    that they result in emission of bogus traffic by legitimate
    routers.  As a result, protection from such adversaries must not
    rely on the correct operation of neighbor routers.  Protection
    measures should adopt the principle of least privilege, to
    minimize the impact of attacks of this sort.  To counter Byzantine
    attacks, routers ought not to trust management traffic (e.g.,
    based on its source) but rather each router should independently
    authenticate management traffic before acting upon it.
 We will assume that any cryptographic countermeasures employed to
 secure BGP will employ algorithms and modes that are resistant to
 attack, even by sophisticated adversaries; thus, we will ignore
 cryptanalytic attacks.
 Deliberate attacks are mimicked by failures that are random and
 unintentional.  In particular, a Byzantine failure in a router may
 occur because the router is faulty in hardware or software or is
 misconfigured.  As described in [3], "A node with a Byzantine failure
 may corrupt messages, forge messages, delay messages, or send
 conflicting messages to different nodes".  Byzantine routers, whether
 faulty, misconfigured, or subverted, have the context to provide

Barbir, et al. Informational [Page 6] RFC 4593 Generic Threats to Routing Protocols October 2006

 believable and very damaging bogus routing information.  Byzantine
 routers may also claim another legitimate peer's identity.  Given
 their status as peers, they may even elude the authentication
 protections, if those protections can only detect that a source is
 one of the legitimate peers (e.g., the router uses the same
 cryptographic key to authenticate all peers).
 We therefore characterize threat sources into two groups:
 Outsiders: These attackers may reside anywhere in the Internet, have
    the ability to send IP traffic to the router, may be able to
    observe the router's replies, and may even control the path for a
    legitimate peer's traffic.  These are not legitimate participants
    in the routing protocol.
 Byzantine: These attackers are faulty, misconfigured, or subverted
    routers; i.e., legitimate participants in the routing protocol.

3.1.2. Threat Consequences

 A threat consequence is a security violation that results from a
 threat action [1].  To a routing protocol, a security violation is a
 compromise of some aspect of the correct behavior of the routing
 system.  The compromise can damage the data traffic intended for a
 particular network or host or can damage the operation of the routing
 infrastructure of the network as a whole.
 There are four types of general threat consequences: disclosure,
 deception, disruption, and usurpation [1].
 o  Disclosure: Disclosure of routing information happens when an
    attacker successfully accesses the information without being
    authorized.  Outsiders who can observe or monitor a link may cause
    disclosure, if routing exchanges lack confidentiality.  Byzantine
    routers can cause disclosure, as long as they are successfully
    involved in the routing exchanges.  Although inappropriate
    disclosure of routing information can pose a security threat or be
    part of a later, larger, or higher layer attack, confidentiality
    is not generally a design goal of routing protocols.
 o  Deception: This consequence happens when a legitimate router
    receives a forged routing message and believes it to be authentic.
    Both outsiders and Byzantine routers can cause this consequence if
    the receiving router lacks the ability to check routing message
    integrity or origin authentication.

Barbir, et al. Informational [Page 7] RFC 4593 Generic Threats to Routing Protocols October 2006

 o  Disruption: This consequence occurs when a legitimate router's
    operation is being interrupted or prevented.  Outsiders can cause
    this by inserting, corrupting, replaying, delaying, or dropping
    routing messages, or by breaking routing sessions between
    legitimate routers.  Byzantine routers can cause this consequence
    by sending false routing messages, interfering with normal routing
    exchanges, or flooding unnecessary routing protocol messages.
    (DoS is a common threat action causing disruption.)
 o  Usurpation: This consequence happens when an attacker gains
    control over the services/functions a legitimate router is
    providing to others.  Outsiders can cause this by delaying or
    dropping routing exchanges, or fabricating or replaying routing
    information.  Byzantine routers can cause this consequence by
    sending false routing information or interfering with routing
    exchanges.
 Note: An attacker does not have to control a router directly to
 control its services.  For example, in Figure 1, Network 1 is dual-
 homed through Router A and Router B, and Router A is preferred.
 However, Router B is compromised and advertises a better metric.
 Consequently, devices on the Internet choose the path through Router
 B to reach Network 1.  In this way, Router B steals the data traffic,
 and Router A loses its control of the services to Router B.  This is
 depicted in Figure 1.
                 +-------------+   +-------+
                 |  Internet   |---| Rtr A |
                 +------+------+   +---+---+
                        |              |
                        |              |
                        |              |
                        |            *-+-*
                 +-------+           /     \
                 | Rtr B |----------*  N 1  *
                 +-------+           \     /
                                      *---*
                Figure 1.  Dual-homed network
 Several threat consequences might be caused by a single threat
 action.  In Figure 1, there exist at least two consequences: routers
 using Router B to reach Network 1 are deceived, and Router A is
 usurped.

Barbir, et al. Informational [Page 8] RFC 4593 Generic Threats to Routing Protocols October 2006

3.1.2.1. Threat Consequence Scope

 As mentioned above, an attack might damage the data traffic intended
 for a particular network or host or damage the operation of the
 routing infrastructure of the network as a whole.  Damage that might
 result from attacks against the network as a whole may include the
 following:
 o  Network congestion.  More data traffic is forwarded through some
    portion of the network than would otherwise need to carry the
    traffic.
 o  Blackhole.  Large amounts of traffic are unnecessarily re-directed
    to be forwarded through one router and that router drops
    many/most/all packets.
 o  Looping.  Data traffic is forwarded along a route that loops, so
    that the data is never delivered (resulting in network
    congestion).
 o  Partition.  Some portion of the network believes that it is
    partitioned from the rest of the network when it is not.
 o  Churn.  The forwarding in the network changes (unnecessarily) at a
    rapid pace, resulting in large variations in the data delivery
    patterns (and adversely affecting congestion control techniques).
 o  Instability.  The protocol becomes unstable so that convergence on
    a global forwarding state is not achieved.
 o  Overcontrol.  The routing protocol messages themselves become a
    significant portion of the traffic the network carries.
 o  Clog.  A router receives an excessive number of routing protocol
    messages, causing it to exhaust some resource (e.g., memory, CPU,
    battery).
 The damage that might result from attacks against a particular host
 or network address may include the following:
 o  Starvation.  Data traffic destined for the network or host is
    forwarded to a part of the network that cannot deliver it.
 o  Eavesdrop.  Data traffic is forwarded through some router or
    network that would otherwise not see the traffic, affording an
    opportunity to see the data or at least the data delivery pattern.

Barbir, et al. Informational [Page 9] RFC 4593 Generic Threats to Routing Protocols October 2006

 o  Cut.  Some portion of the network believes that it has no route to
    the host or network when it is in fact connected.
 o  Delay.  Data traffic destined for the network or host is forwarded
    along a route that is in some way inferior to the route it would
    otherwise take.
 o  Looping.  Data traffic for the network or host is forwarded along
    a route that loops, so that the data is never delivered.
 It is important to consider all consequences, because some security
 solutions can protect against one consequence but not against others.
 It might be possible to design a security solution that protects
 against eavesdropping on one destination's traffic without protecting
 against churn in the network.  Similarly, it is possible to design a
 security solution that prevents a starvation attack against one host,
 but not a clogging attack against a router.  The security
 requirements must be clear as to which consequences are being avoided
 and which consequences must be addressed by other means (e.g., by
 administrative means outside the protocol).

3.1.2.2. Threat Consequence Zone

 A threat consequence zone covers the area within which the network
 operations have been affected by threat actions.  Possible threat
 consequence zones can be classified as a single link or router,
 multiple routers (within a single routing domain), a single routing
 domain, multiple routing domains, or the global Internet.  The threat
 consequence zone varies based on the threat action and the position
 of the target of the attack.  Similar threat actions that happen at
 different locations may result in totally different threat
 consequence zones.  For example, when an outsider breaks the routing
 session between a distribution router and a stub router, only
 reachability to and from the network devices attached to the stub
 router will be impaired.  In other words, the threat consequence zone
 is a single router.  In another case, if the outsider is located
 between a customer edge router and its corresponding provider edge
 router, such an action might cause the whole customer site to lose
 its connection.  In this case, the threat consequence zone might be a
 single routing domain.

3.1.2.3. Threat Consequence Periods

 A threat consequence period is defined as the portion of time during
 which the network operations are impacted by the threat consequences.
 The threat consequence period is influenced by, but not totally
 dependent on, the duration of the threat action.  In some cases, the
 network operations will get back to normal as soon as the threat

Barbir, et al. Informational [Page 10] RFC 4593 Generic Threats to Routing Protocols October 2006

 action has been stopped.  In other cases, however, threat
 consequences may persist longer than does the threat action.  For
 example, in the original Advanced Research Projects Agency Network
 (ARPANET) link-state algorithm, some errors in a router introduced
 three instances of a Link-State Announcement (LSA).  All of them
 flooded throughout the network continuously, until the entire network
 was power cycled [2].

4. Generally Identifiable Routing Threat Actions

 This section addresses generally identifiable and recognized threat
 actions against routing protocols.  The threat actions are not
 necessarily specific to individual protocols but may be present in
 one or more of the common routing protocols in use today.

4.1. Deliberate Exposure

 Deliberate exposure occurs when an attacker takes control of a router
 and intentionally releases routing information to other entities
 (e.g., the attacker, a web page, mail posting, other routers) that
 otherwise should not receive the exposed information.
 The consequence of deliberate exposure is the disclosure of routing
 information.
 The threat consequence zone of deliberate exposure depends on the
 routing information that the attackers have exposed.  The more
 knowledge they have exposed, the bigger the threat consequence zone.
 The threat consequence period of deliberate exposure might be longer
 than the duration of the action itself.  The routing information
 exposed will not be outdated until there is a topology change of the
 exposed network.

4.2. Sniffing

 Sniffing is an action whereby attackers monitor and/or record the
 routing exchanges between authorized routers to sniff for routing
 information.  Attackers can also sniff data traffic information
 (however, this is out of scope of the current work).
 The consequence of sniffing is disclosure of routing information.
 The threat consequence zone of sniffing depends on the attacker's
 location, the routing protocol type, and the routing information that
 has been recorded.  For example, if the outsider is sniffing a link
 that is in an OSPF totally stubby area, the threat consequence zone
 should be limited to the whole area.  An attacker that is sniffing a

Barbir, et al. Informational [Page 11] RFC 4593 Generic Threats to Routing Protocols October 2006

 link in an External Border Gateway Protocol (EBGP) session can gain
 knowledge of multiple routing domains.
 The threat consequence period might be longer than the duration of
 the action.  If an attacker stops sniffing a link, their acquired
 knowledge will not be out-dated until there is a topology change of
 the affected network.

4.3. Traffic Analysis

 Traffic analysis is an action whereby attackers gain routing
 information by analyzing the characteristics of the data traffic on a
 subverted link.  Traffic analysis threats can affect any data that is
 sent over a communication link.  This threat is not peculiar to
 routing protocols and is included here for completeness.
 The consequence of data traffic analysis is the disclosure of routing
 information.  For example, the source and destination IP addresses of
 the data traffic and the type, magnitude, and volume of traffic can
 be disclosed.
 The threat consequence zone of the traffic analysis depends on the
 attacker's location and what data traffic has passed through.  An
 attacker at the network core should be able to gather more
 information than its counterpart at the edge and would therefore have
 to be able to analyze traffic patterns in a wider area.
 The threat consequence period might be longer than the duration of
 the traffic analysis.  After the attacker stops traffic analysis, its
 knowledge will not be outdated until there is a topology change of
 the disclosed network.

4.4. Spoofing

 Spoofing occurs when an illegitimate device assumes the identity of a
 legitimate one.  Spoofing in and of itself is often not the true
 attack.  Spoofing is special in that it can be used to carry out
 other threat actions causing other threat consequences.  An attacker
 can use spoofing as a means for launching other types of attacks.
 For example, if an attacker succeeds in spoofing the identity of a
 router, the attacker can send out unrealistic routing information
 that might cause the disruption of network services.
 There are a few cases where spoofing can be an attack in and of
 itself.  For example, messages from an attacker that spoof the
 identity of a legitimate router may cause a neighbor relationship to
 form and deny the formation of the relationship with the legitimate
 router.

Barbir, et al. Informational [Page 12] RFC 4593 Generic Threats to Routing Protocols October 2006

 The consequences of spoofing are as follows:
 o  The disclosure of routing information.  The spoofing router will
    be able to gain access to the routing information.
 o  The deception of peer relationship.  The authorized routers, which
    exchange routing messages with the spoofing router, do not realize
    that they are neighboring with a router that is faking another
    router's identity.
 The threat consequence zone is as follows:
 o  The consequence zone of the fake peer relationship will be limited
    to those routers trusting the attacker's claimed identity.
 o  The consequence zone of the disclosed routing information depends
    on the attacker's location, the routing protocol type, and the
    routing information that has been exchanged between the attacker
    and its deceived neighbors.
 Note: This section focuses on addressing spoofing as a threat on its
 own.  However, spoofing creates conditions for other threats actions.
 The other threat actions are considered falsifications and are
 treated in the next section.

4.5. Falsification

 Falsification is an action whereby an attacker sends false routing
 information.  To falsify the routing information, an attacker has to
 be either the originator or a forwarder of the routing information.
 It cannot be a receiver-only.  False routing information describes
 the network in an unrealistic fashion, whether or not intended by the
 authoritative network administrator.

4.5.1. Falsifications by Originators

 An originator of routing information can launch the falsifications
 that are described in the next sections.

4.5.1.1. Overclaiming

 Overclaiming occurs when a Byzantine router or outsider advertises
 its control of some network resources, while in reality it does not,
 or if the advertisement is not authorized.  This is given in Figures
 2 and 3.

Barbir, et al. Informational [Page 13] RFC 4593 Generic Threats to Routing Protocols October 2006

         +-------------+   +-------+   +-------+
         | Internet    |---| Rtr B |---| Rtr A |
         +------+------+   +-------+   +---+---+
                |                          .
                |                          |
                |                          .
                |                        *-+-*
            +-------+                   /     \
            | Rtr C |------------------*  N 1  *
            +-------+                   \     /
                                         *---*
                 Figure 2.  Overclaiming-1
         +-------------+   +-------+   +-------+
         |  Internet   |---| Rtr B |---| Rtr A |
         +------+------+   +-------+   +-------+
                |
                |
                |
                |                        *---*
            +-------+                   /     \
            | Rtr C |------------------*  N 1  *
            +-------+                   \     /
                                         *---*
                 Figure 3.  Overclaiming-2
 The above figures provide examples of overclaiming.  Router A, the
 attacker, is connected to the Internet through Router B.  Router C is
 authorized to advertise its link to Network 1.  In Figure 2, Router A
 controls a link to Network 1 but is not authorized to advertise it.
 In Figure 3, Router A does not control such a link.  But in either
 case, Router A advertises the link to the Internet, through Router B.
 Both Byzantine routers and outsiders can overclaim network resources.
 The consequences of overclaiming include the following:
 o  Usurpation of the overclaimed network resources.  In Figures 2 and
    3, usurpation of Network 1 can occur when Router B (or other
    routers on the Internet not shown in the figures) believes that
    Router A provides the best path to reach the Network 1.  As a
    result, routers forward data traffic destined to Network 1 to
    Router A.  The best result is that the data traffic uses an
    unauthorized path, as in Figure 2.  The worst case is that the

Barbir, et al. Informational [Page 14] RFC 4593 Generic Threats to Routing Protocols October 2006

    data never reaches the destination Network 1, as in Figure 3.  The
    ultimate consequence is that Router A gains control over Network
    1's services, by controlling the data traffic.
 o  Usurpation of the legitimate advertising routers.  In Figures 2
    and 3, Router C is the legitimate advertiser of Network 1.  By
    overclaiming, Router A also controls (partially or totally) the
    services/functions provided by the Router C.  (This is NOT a
    disruption, as Router C is operating in a way intended by the
    authoritative network administrator.)
 o  Deception of other routers.  In Figures 2 and 3, Router B, or
    other routers on the Internet, might be deceived into believing
    that the path through Router A is the best.
 o  Disruption of data planes on some routers.  This might happen to
    routers that are on the path that is used by other routers to
    reach the overclaimed network resources through the attacker.  In
    Figures 2 and 3, when other routers on the Internet are deceived,
    they will forward the data traffic to Router B, which might be
    overloaded.
 The threat consequence zone varies based on the consequence:
 o  Where usurpation is concerned, the consequence zone covers the
    network resources that are overclaimed by the attacker (Network 1
    in Figures 2 and 3), and the routers that are authorized to
    advertise the network resources but lose the competition against
    the attacker (Router C in Figures 2 and 3).
 o  Where deception is concerned, the consequence zone covers the
    routers that do believe the attacker's advertisement and use the
    attacker to reach the claimed networks (Router B and other
    deceived routers on the Internet in Figures 2 and 3).
 o  Where disruption is concerned, the consequence zone includes the
    routers that are on the path of misdirected data traffic (Router B
    in Figures 2 and 3 and other routers in the Internet on the path
    of the misdirected traffic).
 The threat consequence will not cease when the attacker stops
 overclaiming and will totally disappear only when the routing tables
 are converged.  As a result, the consequence period is longer than
 the duration of the overclaiming.

Barbir, et al. Informational [Page 15] RFC 4593 Generic Threats to Routing Protocols October 2006

4.5.1.2. Misclaiming

 A misclaiming threat is defined as an action whereby an attacker is
 advertising some network resources that it is authorized to control,
 but in a way that is not intended by the authoritative network
 administrator.  For example, it may be advertising inappropriate link
 costs in an OSPF LSA.  An attacker can eulogize or disparage when
 advertising these network resources.  Byzantine routers can misclaim
 network resources.
 The threat consequences of misclaiming are similar to the
 consequences of overclaiming.
 The consequence zone and period are also similar to those of
 overclaiming.

4.5.2. Falsifications by Forwarders

 In each routing protocol, routers that forward routing protocol
 messages are expected to leave some fields unmodified and to modify
 other fields in certain circumscribed ways.  The fields to be
 modified, the possible new contents of those fields and their
 computation from the original fields, the fields that must remain
 unmodified, etc. are all detailed in the protocol specification.
 They may vary depending on the function of the router or its network
 environment.  For example, in RIP, the forwarder must modify the
 routing information by increasing the hop count by 1.  On the other
 hand, a forwarder must not modify any field of the type 1 LSA in OSPF
 except the age field.  In general, forwarders in distance vector
 routing protocols are authorized to and must modify the routing
 information, while most forwarders in link state routing protocols
 are not authorized to and must not modify most routing information.
 As a forwarder authorized to modify routing messages, an attacker
 might also falsify by not forwarding routing information to other
 authorized routers as required.

4.5.2.1. Misstatement

 This is defined as an action whereby the attacker modifies route
 attributes in an incorrect manner.  For example, in RIP, the attacker
 might increase the path cost by two hops instead of one.  In BGP, the
 attacker might delete some AS numbers from the AS PATH.

Barbir, et al. Informational [Page 16] RFC 4593 Generic Threats to Routing Protocols October 2006

 Where forwarding routing information should not be modified, an
 attacker can launch the following falsifications:
 o  Deletion.  Attacker deletes valid data in the routing message.
 o  Insertion.  Attacker inserts false data in the routing message.
 o  Substitution.  Attacker replaces valid data in the routing message
    with false data.
 A forwarder can also falsify data by replaying out-dated data in the
 routing message as current data.
 All types of attackers, outsiders and Byzantine routers, can falsify
 the routing information when they forward the routing messages.
 The threat consequences of these falsifications by forwarders are
 similar to those caused by originators: usurpation of some network
 resources and related routers; deception of routers using false
 paths; and disruption of data planes of routers on the false paths.
 The threat consequence zone and period are also similar.

4.6. Interference

 Interference is a threat action whereby an attacker inhibits the
 exchanges by legitimate routers.  The attacker can do this by adding
 noise, by not forwarding packets, by replaying out-dated packets, by
 inserting or corrupting messages, by delaying responses, by denial of
 receipts, or by breaking synchronization.
 Byzantine routers can slow down their routing exchanges or induce
 flapping in the routing sessions of legitimate neighboring routers.
 The consequence of interference is the disruption of routing
 operations.
 The consequence zone of interference depends on the severity of the
 interference.  If the interference results in consequences at the
 neighbor maintenance level, then there may be changes in the
 database, resulting in network-wide consequences.
 The threat consequences might disappear as soon as the interference
 is stopped or might not totally disappear until the networks have
 converged.  Therefore, the consequence period is equal to or longer
 than the duration of the interference.

Barbir, et al. Informational [Page 17] RFC 4593 Generic Threats to Routing Protocols October 2006

4.7. Overload

 Overload is defined as a threat action whereby attackers place excess
 burden on legitimate routers.  For example, it is possible for an
 attacker to trigger a router to create an excessive amount of state
 that other routers within the network are not able to handle.  In a
 similar fashion, it is possible for an attacker to overload database
 routing exchanges and thus to influence the routing operations.

5. Security Considerations

 This entire document is security related.  Specifically, the document
 addresses security of routing protocols as associated with threats to
 those protocols.  In a larger context, this work builds upon the
 recognition of the IETF community that signaling and
 control/management planes of networked devices need strengthening.
 Routing protocols can be considered part of that signaling and
 control plane.  However, to date, routing protocols have largely
 remained unprotected and open to malicious attacks.  This document
 discusses inter- and intra-domain routing protocol threats that are
 currently known and lays the foundation for other documents that will
 discuss security requirements for routing protocols.  This document
 is protocol independent.

6. References

6.1. Normative References

 [1]  Shirey, R., "Internet Security Glossary", RFC 2828, May 2000.
 [2]  Rosen, E., "Vulnerabilities of network control protocols: An
      example", RFC 789, July 1981.
 [3]  Perlman, R., "Network Layer Protocols with Byzantine
      Robustness", PhD thesis, MIT LCS TR-429, October 1988.
 [4]  Moy, J., "OSPF Version 2", STD 54, RFC 2328, April 1998.
 [5]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and dual
      environments", RFC 1195, December 1990.
 [6]  Malkin, G., "RIP Version 2", STD 56, RFC 2453, November 1998.
 [7]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway Protocol 4
      (BGP-4)", RFC 4271, January 2006.

Barbir, et al. Informational [Page 18] RFC 4593 Generic Threats to Routing Protocols October 2006

 [8]  ISO 10589, "Intermediate System to Intermediate System intra-
      domain routeing information exchange protocol for use in
      conjunction with the protocol for providing the connectionless-
      mode network service (ISO 8473)", ISO/IEC 10589:2002.

Barbir, et al. Informational [Page 19] RFC 4593 Generic Threats to Routing Protocols October 2006

Appendix A. Acknowledgments

 This document would not have been possible save for the excellent
 efforts and teamwork characteristics of those listed here.
 o  Dennis Beard, Nortel
 o  Ayman Musharbash, Nortel
 o  Jean-Jacques Puig, int-evry, France
 o  Paul Knight, Nortel
 o  Elwyn Davies, Nortel
 o  Ameya Dilip Pandit, Graduate student, University of Missouri
 o  Senthilkumar Ayyasamy, Graduate student, University of Missouri
 o  Stephen Kent, BBN
 o  Tim Gage, Cisco Systems
 o  James Ng, Cisco Systems
 o  Alvaro Retana, Cisco Systems

Appendix B. Acronyms

 AS - Autonomous system.  Set of routers under a single technical
 administration.  Each AS normally uses a single interior gateway
 protocol (IGP) and metrics to propagate routing information within
 the set of routers.  Also called routing domain.
 AS-Path - In BGP, the route to a destination.  The path consists of
 the AS numbers of all routers a packet must go through to reach a
 destination.
 BGP - Border Gateway Protocol.  Exterior gateway protocol used to
 exchange routing information among routers in different autonomous
 systems.
 LSA - Link-State Announcement
 NLRI - Network Layer Reachability Information.  Information that is
 carried in BGP packets and is used by MBGP.
 OSPF - Open Shortest Path First.  A link-state IGP that makes routing
 decisions based on the shortest-path-first (SPF) algorithm (also
 referred to as the Dijkstra algorithm).

Barbir, et al. Informational [Page 20] RFC 4593 Generic Threats to Routing Protocols October 2006

Authors' Addresses

 Abbie Barbir
 Nortel
 3500 Carling Avenue
 Nepean, Ontario  K2H 8E9
 Canada
 EMail: abbieb@nortel.com
 Sandy Murphy
 Sparta, Inc.
 7110 Samuel Morse Drive
 Columbia, MD
 USA
 Phone: 443-430-8000
 EMail: sandy@sparta.com
 Yi Yang
 Cisco Systems
 7025 Kit Creek Road
 RTP, NC  27709
 USA
 EMail: yiya@cisco.com

Barbir, et al. Informational [Page 21] RFC 4593 Generic Threats to Routing Protocols October 2006

Full Copyright Statement

 Copyright (C) The Internet Society (2006).
 This document is subject to the rights, licenses and restrictions
 contained in BCP 78, and except as set forth therein, the authors
 retain all their rights.
 This document and the information contained herein are provided on an
 "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
 OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
 ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
 INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
 INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
 WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Intellectual Property

 The IETF takes no position regarding the validity or scope of any
 Intellectual Property Rights or other rights that might be claimed to
 pertain to the implementation or use of the technology described in
 this document or the extent to which any license under such rights
 might or might not be available; nor does it represent that it has
 made any independent effort to identify any such rights.  Information
 on the procedures with respect to rights in RFC documents can be
 found in BCP 78 and BCP 79.
 Copies of IPR disclosures made to the IETF Secretariat and any
 assurances of licenses to be made available, or the result of an
 attempt made to obtain a general license or permission for the use of
 such proprietary rights by implementers or users of this
 specification can be obtained from the IETF on-line IPR repository at
 http://www.ietf.org/ipr.
 The IETF invites any interested party to bring to its attention any
 copyrights, patents or patent applications, or other proprietary
 rights that may cover technology that may be required to implement
 this standard.  Please address the information to the IETF at
 ietf-ipr@ietf.org.

Acknowledgement

 Funding for the RFC Editor function is provided by the IETF
 Administrative Support Activity (IASA).

Barbir, et al. Informational [Page 22]

/data/webs/external/dokuwiki/data/pages/rfc/rfc4593.txt · Last modified: 2006/10/12 17:20 by 127.0.0.1

Donate Powered by PHP Valid HTML5 Valid CSS Driven by DokuWiki