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rfc:rfc7985

Internet Engineering Task Force (IETF) J. Yi Request for Comments: 7985 T. Clausen Updates: 7186 Ecole Polytechnique Category: Informational U. Herberg ISSN: 2070-1721 November 2016

     Security Threats to Simplified Multicast Forwarding (SMF)

Abstract

 This document analyzes security threats to Simplified Multicast
 Forwarding (SMF), including vulnerabilities of duplicate packet
 detection and relay set selection mechanisms.  This document is not
 intended to propose solutions to the threats described.
 In addition, this document updates RFC 7186 regarding threats to the
 relay set selection mechanisms using the Mobile Ad Hoc Network
 (MANET) Neighborhood Discovery Protocol (NHDP) (RFC 6130).

Status of This Memo

 This document is not an Internet Standards Track specification; it is
 published for informational purposes.
 This document is a product of the Internet Engineering Task Force
 (IETF).  It has been approved for publication by the Internet
 Engineering Steering Group (IESG).  Not all documents approved by the
 IESG are a candidate for any level of Internet Standard; see
 Section 2 of RFC 7841.
 Information about the current status of this document, any errata,
 and how to provide feedback on it may be obtained at
 http://www.rfc-editor.org/info/rfc7985.

Yi, et al. Informational [Page 1] RFC 7985 Security Threats for SMF November 2016

Copyright Notice

 Copyright (c) 2016 IETF Trust and the persons identified as the
 document authors.  All rights reserved.
 This document is subject to BCP 78 and the IETF Trust's Legal
 Provisions Relating to IETF Documents
 (http://trustee.ietf.org/license-info) in effect on the date of
 publication of this document.  Please review these documents
 carefully, as they describe your rights and restrictions with respect
 to this document.  Code Components extracted from this document must
 include Simplified BSD License text as described in Section 4.e of
 the Trust Legal Provisions and are provided without warranty as
 described in the Simplified BSD License.

Table of Contents

 1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   3
 2.  Terminology . . . . . . . . . . . . . . . . . . . . . . . . .   4
 3.  SMF Threat Overview . . . . . . . . . . . . . . . . . . . . .   4
 4.  Threats to Duplicate Packet Detection . . . . . . . . . . . .   5
   4.1.  Attack on the Hop Limit Field . . . . . . . . . . . . . .   6
   4.2.  Threats to Identification-Based Duplicate Packet
         Detection . . . . . . . . . . . . . . . . . . . . . . . .   7
     4.2.1.  Pre-Activation Attacks (Pre-Play) . . . . . . . . . .   7
     4.2.2.  De-activation Attacks (Sequence Number Wrangling) . .   8
   4.3.  Threats to Hash-Based Duplicate Packet Detection  . . . .   9
     4.3.1.  Attack on the Hash-Assistant Value  . . . . . . . . .   9
 5.  Threats to Relay Set Selection  . . . . . . . . . . . . . . .  10
   5.1.  Common Threats to Relay Set Selection . . . . . . . . . .  10
   5.2.  Threats to the E-CDS Algorithm  . . . . . . . . . . . . .  10
     5.2.1.  Link Spoofing . . . . . . . . . . . . . . . . . . . .  11
     5.2.2.  Identity Spoofing . . . . . . . . . . . . . . . . . .  11
   5.3.  Threats to S-MPR Algorithm  . . . . . . . . . . . . . . .  11
   5.4.  Threats to the MPR-CDS Algorithm  . . . . . . . . . . . .  12
 6.  Security Considerations . . . . . . . . . . . . . . . . . . .  12
 7.  References  . . . . . . . . . . . . . . . . . . . . . . . . .  13
   7.1.  Normative References  . . . . . . . . . . . . . . . . . .  13
   7.2.  Informative References  . . . . . . . . . . . . . . . . .  13
 Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . . .  15
 Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  15

Yi, et al. Informational [Page 2] RFC 7985 Security Threats for SMF November 2016

1. Introduction

 This document analyzes security threats to Simplified Multicast
 Forwarding (SMF) [RFC6621].  SMF aims at providing basic Internet
 Protocol (IP) multicast forwarding in a way that is suitable for
 wireless mesh and Mobile Ad Hoc Networks (MANET).  SMF consists of
 two major functional components: duplicate packet detection (DPD) and
 relay set selection (RSS).
 SMF is typically used in decentralized wireless environments and is
 potentially exposed to various attacks and misconfigurations.  In a
 wireless environment, some of these attacks and misconfigurations
 represent threats of particular significance as compared to what they
 would do in wired networks.  [RFC6621] briefly discusses several of
 these, but does not define any explicit security measures for
 protecting the integrity of the protocol.
 This document is based on the assumption that no additional security
 mechanism, such as IPsec, is used in the IP layer, as not all MANET
 deployments may be able to support deployment of such common IP
 protection mechanisms (e.g., because MANET routers may have limited
 resources for supporting the IPsec stack).  It also assumes that
 there is no lower-layer protection.  The document analyzes possible
 attacks on, and misconfigurations of, SMF and outlines the
 consequences of such attacks/misconfigurations to the state
 maintained by SMF in each router.
 In the Security Considerations section of [RFC6621], denial-of-
 service-attack scenarios are briefly discussed.  This document
 further analyzes and describes the potential vulnerabilities of, and
 attack vectors for, SMF.  While completeness in such analysis is
 always a goal, no claims of being complete are made.  The goal of
 this document is to be helpful when deploying SMF in a network and
 for understanding the risks incurred, as well as for providing a
 reference to and documented experience with SMF as input for possible
 future developments of SMF.
 This document is not intended to propose solutions to the threats
 described.  [RFC7182] provides a framework that can be used with SMF,
 and depending on how it is used, may offer some degree of protection
 against the threats related to identity spoofing described in this
 document.
 This document also updates [RFC7186], specifically with respect to
 threats to relay set selection (RSS) mechanisms that are using MANET
 NHDP [RFC6130].

Yi, et al. Informational [Page 3] RFC 7985 Security Threats for SMF November 2016

2. Terminology

 This document uses the terminology and notation defined in [RFC5444],
 [RFC6130], [RFC6621], and [RFC4949].
 Additionally, this document introduces the following terminology:
 SMF router:  A MANET router, running SMF as specified in [RFC6621].
 Attacker:  A device that is present in the network and intentionally
    seeks to compromise the information bases in SMF routers.  It may
    generate syntactically correct SMF control messages.
 Legitimate SMF router:  An SMF router that is correctly configured
    and not compromised by an attacker.

3. SMF Threat Overview

 An SMF router requires an external dynamic neighborhood discovery
 mechanism in order to maintain suitable topological information
 describing its immediate neighborhood, and thereby allowing it to
 select reduced relay sets for forwarding multicast data traffic.
 Such an external dynamic neighborhood discovery mechanism may be
 provided by lower-layer interface information, by a concurrently
 operating MANET routing protocol that already maintains such
 information (e.g., [RFC7181]) or by explicitly using the MANET
 Neighborhood Discovery Protocol (NHDP) [RFC6130].  If NHDP is used
 for both 1-hop and 2-hop neighborhood discovery by SMF, SMF
 implicitly inherits the vulnerabilities of NHDP discussed in
 [RFC7186].  As SMF relies on NHDP to assist in network-layer 2-hop
 neighborhood discovery (no matter if other lower-layer mechanisms are
 used for 1-hop neighborhood discovery), this document assumes that
 NHDP is used in SMF.  The threats that are NHDP specific are
 indicated explicitly.
 Based on neighborhood discovery mechanisms, [RFC6621] specifies two
 principal functional components: duplicate packet detection (DPD) and
 relay set selection (RSS).
 DPD is required by SMF in order to be able to detect duplicate
 packets and eliminate their redundant forwarding.  An attacker has
 two ways in which to harm the DPD mechanisms.  Specifically, it can:
 o  "deactivate" DPD, making it such that duplicate packets are not
    correctly detected.  As a consequence, they are (redundantly)
    transmitted, which increases the load on the network, drains the
    batteries of the routers involved, etc.

Yi, et al. Informational [Page 4] RFC 7985 Security Threats for SMF November 2016

 o  "pre-activate" DPD, making DPD detect a later arriving (valid)
    packet as being a duplicate and will, therefore, not be forwarded.
 Attacks on DPD can be achieved by replaying existing packets,
 wrangling sequence numbers, manipulating hash values, etc.; these are
 detailed in Section 4.
 RSS produces a reduced relay set for forwarding multicast data
 packets across a MANET.  For use in SMF, [RFC6621] specifies several
 relay set algorithms including E-CDS (Essential Connected Dominating
 Set) [RFC5614], S-MPR (Source-Based Multipoint Relay, as known from
 [RFC3626] and [RFC7181]), and MPR-CDS (Multipoint Relay Connected
 Dominating Set) [MPR-CDS].  An attacker can disrupt the RSS
 algorithm, and thereby the SMF operation, by degrading it to
 classical flooding or by "masking" certain parts of the network from
 the multicasting domain.  Attacks on RSS algorithms are detailed in
 Section 5.
 Other than the attacks on DPD and RSS, a common vulnerability of
 MANETs is "jamming", i.e., a device generates massive amounts of
 interfering radio transmissions, which will prevent legitimate
 traffic (e.g., control traffic as well as data traffic) on part of a
 network.  The attacks on DPD and RSS can be further enhanced by
 jamming.

4. Threats to Duplicate Packet Detection

 Duplicate packet detection (DPD) is required for packet dissemination
 in MANETs because: (1) packets may be retransmitted via the same
 physical interface as the one over which they were received, and (2)
 a router may receive multiple copies of the same packet (on the same
 or on different interfaces) from different neighbors.  DPD is thus
 used to check whether or not an incoming packet has been previously
 received.
 DPD is achieved by maintaining a record of recently processed
 multicast packets, and comparing later received multicast packets
 herewith.  A duplicate packet detected is silently dropped and is not
 inserted into the forwarding path of that router, nor is it delivered
 to an application.  DPD, as proposed by SMF, supports both IPv4 and
 IPv6 and suggests two duplicate packet detection mechanisms for each:
 1) IP packet header content identification-based DPD (I-DPD), in
 combination with flow state, to estimate temporal uniqueness of a
 packet, and 2) hash-based DPD (H-DPD), employing hashing of selected
 IP packet header fields and payload for the same effect.

Yi, et al. Informational [Page 5] RFC 7985 Security Threats for SMF November 2016

 In the Security Considerations section of [RFC6621], a selection of
 threats to DPD are briefly introduced.  This section expands on that
 discussion and describes how to effectively launch the attacks on DPD
 -- for example, by way of manipulating jitter and/or the Hash-
 Assistant Value.  In the remainder of this section, common threats to
 packet detection mechanisms are discussed first; then, the threats to
 I-DPD and H-DPD are introduced separately.  The threats described in
 this section are applicable to general SMF implementations,
 regardless of whether NHDP is used.

4.1. Attack on the Hop Limit Field

 One immediate Denial-of-Service (DoS) attack is based on manipulating
 the Time-to-Live (TTL, for IPv4) or Hop Limit (for IPv6) field.  As
 routers only forward packets with TTL > 1, an attacker can forward an
 otherwise valid packet while drastically reducing the TTL hereof.
 This will inhibit recipient routers from later forwarding the same
 multicast packet, even if received with a different TTL --
 essentially, an attacker can thus instruct its neighbors to block the
 forwarding of valid multicast packets.
 For example, in Figure 1, router A forwards a multicast packet with a
 TTL of 64 to the network.  A, B, and C are legitimate SMF routers,
 and X is an attacker.  In a wireless environment, jitter is commonly
 used to avoid systematic collisions in Media Access Control (MAC)
 protocols [RFC5148].  An attacker can thus increase the probability
 that its invalid packets arrive first by retransmitting them without
 applying jitter.  In this example, router X forwards the packet
 without applying jitter and reduces the TTL to 1.  Router C thus
 records the duplicate detection value (hash value for H-DPD or the
 header content of the packets for I-DPD) but does not forward the
 packet (due to TTL == 1).  When a second copy of the same packet,
 with a non-maliciously manipulated TTL value (63 in this case),
 arrives from router B, it will be discarded as a duplicate packet.
                               .---.
                               | X |
                             --'---' __
      packet with TTL=64    /          \  packet with TTL=1
                           /            \
                       .---.              .---.
                       | A |              | C |
                       '---'              '---'
      packet with TTL=64   \    .---.   /
                            \-- | B |__/  packet with TTL=63
                                '---'
                               Figure 1

Yi, et al. Informational [Page 6] RFC 7985 Security Threats for SMF November 2016

 As the TTL of a packet is intended to be manipulated by
 intermediaries forwarding it, classic methods such as integrity check
 values (e.g., digital signatures) are typically calculated by setting
 TTL fields to some predetermined value (e.g., 0) -- for example, the
 case for IPsec Authentication Headers -- rendering such an attack
 more difficult to both detect and counter.
 If the attacker has access to a "wormhole" through the network (a
 directional antenna, a tunnel to a collaborator, or a wired
 connection, allowing it to bridge parts of a network otherwise
 distant), it can make sure that the packets with such an artificially
 reduced TTL arrive before their unmodified counterparts.

4.2. Threats to Identification-Based Duplicate Packet Detection

 I-DPD uses a specific DPD identifier in the packet header to identify
 a packet.  By default, such packet identification is not provided by
 the IP packet header (for both IPv4 and IPv6).  Therefore, additional
 identification headers, such as the fragment header, a hop-by-hop
 header option, or IPsec sequencing, must be employed in order to
 support I-DPD.  The uniqueness of a packet can then be identified by
 the source IP address of the packet originator and the sequence
 number (from the fragment header, hop-by-hop header option, or
 IPsec).  By doing so, each intermediate router can keep a record of
 recently received packets and determine whether or not the incoming
 packet has been received.

4.2.1. Pre-Activation Attacks (Pre-Play)

 In a wireless environment, or across any other shared channel, an
 attacker can perceive the identification tuple (source IP address,
 sequence number) of a packet.  It is possible to generate a packet
 with the same (source IP address, sequence number) pair with invalid
 content.  If the sequence number progression is predictable, then it
 is trivial to generate and inject invalid packets with "future"
 identification information into the network.  If these invalid
 packets arrive before the legitimate packets that they are spoofing,
 the latter will be treated as a duplicate and will be discarded.
 This can prevent multicast packets from reaching parts of the
 network.
 Figure 2 gives an example of a pre-activation attack.  A, B, and C
 are legitimate SMF routers, and X is the attacker.  The line between
 the routers presents the packet forwarding.  Router A is the source
 and originates a multicast packet with sequence number n.  When
 router X receives the packet, it generates an invalid packet with the
 source address of A and sequence number n.  If the invalid packet
 arrives at router C before the forwarding of router B, the valid

Yi, et al. Informational [Page 7] RFC 7985 Security Threats for SMF November 2016

 packet will be dropped by C as a duplicate packet.  An attacker can
 manipulate jitter to make sure that the invalid packets arrive first.
 Router X can even generate packets with future sequence numbers (if
 they are predictable), so that the future legitimate packets with the
 same sequence numbers will be dropped as duplicate ones.
                               .---.
                               | X |
                             --'---' __
      packet with seq=n     /          \  invalid packet with seq=n
                           /            \
                       .---.              .---.
                       | A |              | C |
                       '---'              '---'
      packet with seq=n    \    .---.   /
                            \-- | B |__/  valid packet with seq=n
                                '---'
                               Figure 2
 As SMF does not currently have any timestamp mechanisms to protect
 data packets, there is no viable way to detect such pre-play attacks
 by way of timestamps.  Especially, if the attack is based on
 manipulation of jitter, the validation of the timestamp would not be
 helpful because the timing is still valid (but, much less valuable).

4.2.2. De-activation Attacks (Sequence Number Wrangling)

 An attacker can also seek to de-activate DPD by modifying the
 sequence number in packets that it forwards.  Thus, routers will not
 be able to detect an actual duplicate packet as a duplicate --
 rather, they will treat them as new packets, i.e., process and
 forward them.  This is similar to DoS attacks, as each packet that is
 considered unique will be multicasted: for a network with n routers,
 there will be n-1 retransmissions.  This can easily cause the
 "broadcast storm" problem discussed in [MOBICOM99].  The consequence
 of this attack is an increased channel load, the origin of which
 appears to be a router other than the attacker.
 Given the topology shown in Figure 2, on receiving a packet with
 seq=n, the attacker X can forward the packet with a modified sequence
 number n+i.  This has two consequences: firstly, router C will not be
 able to detect that the packet forwarded by X is a duplicate packet;
 secondly, the consequent packet with seq=n+i generated by router A
 will probably be treated as a duplicate packet and will be dropped by
 router C.

Yi, et al. Informational [Page 8] RFC 7985 Security Threats for SMF November 2016

4.3. Threats to Hash-Based Duplicate Packet Detection

 When explicit sequence numbers in packet headers is undesired, hash-
 based DPD can be used.  A hash of the non-mutable fields in the
 header of the data payload can be generated and recorded at the
 intermediate routers.  A packet can thus be uniquely identified by
 the source IP address of the packet and its hash-value.
 The hash algorithm used by SMF is being applied only to provide a
 reduced probability of collision and is not being used for
 cryptographic or authentication purposes.  Consequently, a digest
 collision is still possible.  In case the source router or gateway
 identifies that it has recently generated or injected a packet with
 the same hash-value, it inserts a "Hash-Assist Value (HAV)" IPv6
 header option into the packet, such that also calculating the hash
 over this HAV will render the resulting value unique.

4.3.1. Attack on the Hash-Assistant Value

 The HAV header is helpful when a digest collision happens.  However,
 it also introduces a potential vulnerability.  As the HAV option is
 only added when the source or the ingress SMF router detects that the
 incoming packet has digest collision with previously generated
 packets, it can actually be regarded as a "flag" of potential digest
 collision.  An attacker can discover the HAV header and be able to
 conclude that a hash collision is possible if the HAV header is
 removed.  By doing so, the modified packet received by other SMF
 routers will be treated as duplicate packets and will be dropped
 because they have the same hash value as previously received packets.
 In the example shown in Figure 3, routers A and B are legitimate SMF
 routers; X is an attacker.  Router A generates two packets, P1 and
 P2, with the same hash value h(P1)=h(P2)=x.  Based on the SMF
 specification, a HAV is added to the latter packet P2, so that
 h(P2+HAV)=x' avoids digest collision.  When the attacker X detects
 the HAV of P2, it is able to conclude that a collision is possible by
 removing the HAV header.  By doing so, packet P2 will be treated as a
 duplicate packet by router B and will be dropped.
            P2            P1                P2         P1
 .---.  h(P2+HAV)=x'    h(P1)=x    .---.  h(P2)=x     h(P1)=x    .---.
 | A |---------------------------> | X | ----------------------> | B |
 `---'                             `---'                         `---'
                               Figure 3

Yi, et al. Informational [Page 9] RFC 7985 Security Threats for SMF November 2016

5. Threats to Relay Set Selection

 A framework for an RSS mechanism, rather than a specific RSS
 algorithm, is provided by SMF.  Relay Set Selection is normally
 achieved by distributed algorithms that can dynamically generate a
 topological Connected Dominating Set based on 1-hop and 2-hop
 neighborhood information.  In this section, common threats to the RSS
 framework are first discussed.  Then specific threats to the three
 algorithms (Essential Connection Dominating Set (E-CDS), Source-Based
 Multipoint Relay (S-MPR), and Multipoint Relay Connected Dominating
 Set (MPR-CDS)) explicitly enumerated by [RFC6621] are analyzed.  As
 the relay set selection is based on 1-hop and 2-hop neighborhood
 information, which rely on NHDP, the threats described in this
 section are NHDP specific.

5.1. Common Threats to Relay Set Selection

 Non-algorithm-specific threats to RSS algorithms, including DoS
 attacks, eavesdropping, message timing attacks, and broadcast storm,
 are discussed in [RFC7186].

5.2. Threats to the E-CDS Algorithm

 The "Essential Connected Dominating Set" (E-CDS) algorithm [RFC5614]
 forms a single CDS mesh for an SMF operating region.  This algorithm
 requires 2-hop neighborhood information (the identity of the
 neighbors, the link to the neighbors, and the neighbors' priority
 information), as collected through NHDP or another process.
 An SMF router will select itself as a relay, if:
 o  The SMF router has a higher priority than all of its symmetric
    neighbors, or
 o  A path from the neighbor with the largest priority to any other
    neighbor via neighbors with greater priority than the current
    router does not exist.
 An attacker can disrupt the E-CDS algorithm by link spoofing or
 identity spoofing.

Yi, et al. Informational [Page 10] RFC 7985 Security Threats for SMF November 2016

5.2.1. Link Spoofing

 Link spoofing implies that an attacker advertises non-existing links
 to another router (which may or may not be present in the network).
 An attacker can declare itself to have high route priority and spoof
 the links to as many legitimate SMF routers as possible to declare
 high connectivity.  By doing so, it can prevent legitimate SMF
 routers from selecting themselves as relays.  As the "super" relay in
 the network, the attacker can manipulate the traffic it relays.

5.2.2. Identity Spoofing

 Identity spoofing implies that an attacker determines and makes use
 of the identity of other legitimate routers, without being authorized
 to do so.  The identity of other routers can be obtained by
 eavesdropping the control messages or the source/destination address
 from datagrams.  The attacker can then generate control or datagram
 traffic by pretending to be a legitimate router.
 Because E-CDS self-selection is based on the router priority value,
 an attacker can spoof the identity of other legitimate routers and
 declare a different router priority value.  If it declares that a
 spoofed router has a higher priority, it can prevent other routers
 from selecting themselves as relays.  On the other hand, if the
 attacker declares that a spoofed router has a lower priority, it can
 force other routers to select themselves as relays to degrade the
 multicast forwarding to classical flooding.

5.3. Threats to S-MPR Algorithm

 The S-MPR set selection algorithm enables individual routers, using
 2-hop topology information, to select relays from among their set of
 neighboring routers.  MPRs are selected by each router such that a
 message generated by it, and relayed only by its MPRs, will reach all
 of its 2-hop neighbors.
 An SMF router forwards a multicast packet if and only if:
 o  the packet has not been received before, and
 o  the neighbor from which the packet was received has selected the
    router as MPR.
 Because MPR calculation is based on the willingness declared by the
 SMF routers and the connectivity of the routers, it can be disrupted
 by both link spoofing and identity spoofing.  These threats and their
 impacts have been illustrated in Section 5.1 of [RFC7186].

Yi, et al. Informational [Page 11] RFC 7985 Security Threats for SMF November 2016

5.4. Threats to the MPR-CDS Algorithm

 MPR-CDS is a derivative from S-MPR.  The main difference between
 S-MPR and MPR-CDS is that while S-MPR forms a different broadcast
 tree for each source in the network, MPR-CDS forms a unique broadcast
 tree for all sources in the network.
 As MPR-CDS combines E-CDS and S-MPR and the simple combination of the
 two algorithms does not address the weaknesses; the vulnerabilities
 of E-CDS and S-MPR that are discussed in Sections 5.2 and 5.3 apply
 to MPR-CDS also.

6. Security Considerations

 This document does not specify a protocol or a procedure.  The whole
 document, however, reflects on security considerations for SMF
 regarding packet dissemination in MANETs.  Possible attacks to the
 two main functional components of SMF, duplicate packet detection,
 and relay set selection are analyzed and documented.
 Although neither [RFC6621] nor this document propose mechanisms to
 secure the SMF protocol, there are several possibilities to secure
 the protocol in the future and drive new work by suggesting which
 threats discussed in the previous sections could be addressed.
 For the I-DPD mechanism, employing randomized packet sequence numbers
 can avoid some pre-activation attacks based on sequence number
 prediction.  If predicable sequence numbers have to be used, applying
 timestamps can mitigate pre-activation attacks.
 For the H-DPD mechanism, applying cryptographically strong hashes can
 make the digest collisions effectively impossible, and it can avoid
 the use of a HAV.
 [RFC7182] specifies a framework for representing cryptographic
 Integrity Check Values (ICVs) and timestamps in MANETs.  Based on
 [RFC7182], [RFC7183] specifies integrity and replay protection for
 NHDP using shared keys as a mandatory-to-implement security
 mechanism.  If SMF is using NHDP as the neighborhood discovery
 protocol, implementing [RFC7183] remains advisable so as to enable
 integrity protection for NHDP control messages.  This can help
 mitigate threats related to identity spoofing through the exchange of
 HELLO messages and provide some general protection against identity
 spoofing by admitting only trusted routers to the network using ICVs
 in HELLO messages.

Yi, et al. Informational [Page 12] RFC 7985 Security Threats for SMF November 2016

 Using ICVs does not, of course, address the problem of attackers able
 to also generate valid ICVs.  Detection and exclusion of such
 attackers is, in general, a challenge that is not unrelated to how
 [RFC7182] is used.  If, for example, it is used with a shared key (as
 per [RFC7183]), excluding single attackers generally is not aided by
 the use of ICVs.  However, if routers have sufficient capabilities to
 support the use of asymmetric keys (as per [RFC7859]), part of
 addressing this challenge becomes one of providing key revocation in
 a way that does not in itself introduce additional vulnerabilities.
 As [RFC7183] does not protect the integrity of the multicast user
 datagram, and as no mechanism is specified by SMF for doing so,
 duplicate packet detection remains vulnerable to the threats
 introduced in Section 4.
 If pre-activation/de-activation attacks and attacks on the HAV of the
 multicast datagrams are to be mitigated, a datagram-level integrity
 protection mechanism is desired, by taking consideration of the
 identity field or HAV.  However, this would not be helpful for the
 attacks on the TTL (or Hop Limit for IPv6) field, because the mutable
 fields are generally not considered when ICV is calculated.

7. References

7.1. Normative References

 [RFC6130]  Clausen, T., Dearlove, C., and J. Dean, "Mobile Ad Hoc
            Network (MANET) Neighborhood Discovery Protocol (NHDP)",
            RFC 6130, DOI 10.17487/RFC6130, April 2011,
            <http://www.rfc-editor.org/info/rfc6130>.
 [RFC6621]  Macker, J., Ed., "Simplified Multicast Forwarding",
            RFC 6621, DOI 10.17487/RFC6621, May 2012,
            <http://www.rfc-editor.org/info/rfc6621>.
 [RFC7186]  Yi, J., Herberg, U., and T. Clausen, "Security Threats for
            the Neighborhood Discovery Protocol (NHDP)", RFC 7186,
            DOI 10.17487/RFC7186, April 2014,
            <http://www.rfc-editor.org/info/rfc7186>.

7.2. Informative References

 [MOBICOM99]
            Ni, S., Tseng, Y., Chen, Y., and J. Sheu, "The broadcast
            storm problem in a mobile ad hoc network", MobiCom
            '99 Proceedings of the 5th annual ACM/IEEE international
            conference on Mobile computing and networking,
            DOI 10.1145/313451.313525, 1999.

Yi, et al. Informational [Page 13] RFC 7985 Security Threats for SMF November 2016

 [MPR-CDS]  Adjih, C., Jacquet, P., and L. Viennot, "Computing
            Connected Dominating Sets with Multipoint Relays", Journal
            of Ad Hoc and Sensor Wireless Networks 2002, January 2002.
 [RFC3626]  Clausen, T., Ed. and P. Jacquet, Ed., "Optimized Link
            State Routing Protocol (OLSR)", RFC 3626,
            DOI 10.17487/RFC3626, October 2003,
            <http://www.rfc-editor.org/info/rfc3626>.
 [RFC4949]  Shirey, R., "Internet Security Glossary, Version 2",
            FYI 36, RFC 4949, DOI 10.17487/RFC4949, August 2007,
            <http://www.rfc-editor.org/info/rfc4949>.
 [RFC5148]  Clausen, T., Dearlove, C., and B. Adamson, "Jitter
            Considerations in Mobile Ad Hoc Networks (MANETs)",
            RFC 5148, DOI 10.17487/RFC5148, February 2008,
            <http://www.rfc-editor.org/info/rfc5148>.
 [RFC5444]  Clausen, T., Dearlove, C., Dean, J., and C. Adjih,
            "Generalized Mobile Ad Hoc Network (MANET) Packet/Message
            Format", RFC 5444, DOI 10.17487/RFC5444, February 2009,
            <http://www.rfc-editor.org/info/rfc5444>.
 [RFC5614]  Ogier, R. and P. Spagnolo, "Mobile Ad Hoc Network (MANET)
            Extension of OSPF Using Connected Dominating Set (CDS)
            Flooding", RFC 5614, DOI 10.17487/RFC5614, August 2009,
            <http://www.rfc-editor.org/info/rfc5614>.
 [RFC7181]  Clausen, T., Dearlove, C., Jacquet, P., and U. Herberg,
            "The Optimized Link State Routing Protocol Version 2",
            RFC 7181, DOI 10.17487/RFC7181, April 2014,
            <http://www.rfc-editor.org/info/rfc7181>.
 [RFC7182]  Herberg, U., Clausen, T., and C. Dearlove, "Integrity
            Check Value and Timestamp TLV Definitions for Mobile Ad
            Hoc Networks (MANETs)", RFC 7182, DOI 10.17487/RFC7182,
            April 2014, <http://www.rfc-editor.org/info/rfc7182>.
 [RFC7183]  Herberg, U., Dearlove, C., and T. Clausen, "Integrity
            Protection for the Neighborhood Discovery Protocol (NHDP)
            and Optimized Link State Routing Protocol Version 2
            (OLSRv2)", RFC 7183, DOI 10.17487/RFC7183, April 2014,
            <http://www.rfc-editor.org/info/rfc7183>.
 [RFC7859]  Dearlove, C., "Identity-Based Signatures for Mobile Ad Hoc
            Network (MANET) Routing Protocols", RFC 7859,
            DOI 10.17487/RFC7859, May 2016,
            <http://www.rfc-editor.org/info/rfc7859>.

Yi, et al. Informational [Page 14] RFC 7985 Security Threats for SMF November 2016

Acknowledgments

 The authors would like to thank Christopher Dearlove (BAE Systems
 ATC) who provided detailed review and valuable comments.

Authors' Addresses

 Jiazi Yi
 Ecole Polytechnique
 91128 Palaiseau Cedex
 France
 Phone: +33 1 77 57 80 85
 Email: jiazi@jiaziyi.com
 URI:   http://www.jiaziyi.com/
 Thomas Heide Clausen
 Ecole Polytechnique
 91128 Palaiseau Cedex
 France
 Phone: +33 6 6058 9349
 Email: T.Clausen@computer.org
 URI:   http://www.thomasclausen.org/
 Ulrich Herberg
 Email: ulrich@herberg.name
 URI:   http://www.herberg.name/

Yi, et al. Informational [Page 15]

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