Working Group
Internet Engineering Task Force (IETF)                       U. Chunduri
Internet-Draft
Request for Comments: 7602                                         W. Lu
Intended status:
Category: Standards Track                                        A. Tian
Expires: October 24, 2015
ISSN: 2070-1721                                            Ericsson Inc.
                                                                 N. Shen
                                                     Cisco Systems, Inc.
                                                          April 22,
                                                               July 2015

                   IS-IS Extended Sequence number Number TLV
              draft-ietf-isis-extended-sequence-no-tlv-06

Abstract

   This document defines the Extended Sequence number Number TLV to protect
   Intermediate System to Intermediate System (IS-IS) PDUs from replay
   attacks.

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   http://www.rfc-editor.org/info/rfc7602.

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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
     1.2.  Acronyms  . . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  Replay attacks Attacks and Impact on IS-IS networks Networks . . . . . . . . .   4
     2.1.  IIHs  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.2.  LSPs  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
     2.3.  SNPs  . . . . . . . . . . . . . . . . . . . . . . . . . .   4
   3.  Extended Sequence Number TLV  . . . . . . . . . . . . . . . .   4
     3.1.  Sequence Number Wrap  . . . . . . . . . . . . . . . . . .   5
   4.  Mechanism and Packet Encoding . . . . . . . . . . . . . . . .   6   5
     4.1.  IIHs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
     4.2.  SNPs  . . . . . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Backward Compatibility and Deployment . . . . . . . . . . . .   6
     5.1.  IIH  IIHs and SNPs . . . . . . . . . . . . . . . . . . . . . .   7
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  Contributors  References  . . . . . . . . . . . . . . . . . . . . . . . . .   8
   9.  Acknowledgements
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   8
     8.2.  Informative References  . . . . . .   8
   10. References . . . . . . . . . . .   8
   Appendix A.  ESSN Encoding Mechanisms . . . . . . . . . . . . . .   8
     10.1.  Normative References  10
     A.1.  Using Timestamps  . . . . . . . . . . . . . . . . . .   8
     10.2.  Informative References . .  10
     A.2.  Using Non-volatile Storage  . . . . . . . . . . . . . . .   8  10
   Appendix A.  ESSN Encoding Mechanisms . B.  Operational/Implementation Considerations  . . . . .  11
   Acknowledgements  . . . . . . . .   9
     A.1.  Using Timestamp . . . . . . . . . . . . . . . .  11
   Contributors  . . . . .   9
     A.2.  Using Non-Volatile Storage . . . . . . . . . . . . . . .  10
   Appendix B.  Operational/Implementation consideration . . . . . .  10  11
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  10  12

1.  Introduction

   With the rapid development of new data center infrastructures, due to
   its flexibility and scalability attributes,

   Intermediate System to Intermediate System (IS-IS, [ISO10589]) (IS-IS) [ISO10589] has
   been adopted widely in various L2/L3 Layer 2 / Layer 3 routing and
   switching deployment deployments of the data centers and for critical business
   operations.  Its flexibility and scalability make it well suited for
   the rapid development of new data center infrastructures.  Also,
   while technologies such as Software Defined Networks Software-Defined Networking (SDN) may
   improve network management and enable new applications, their use also has
   an effect on the security requirements of the routing infrastructure.

   A replayed IS-IS PDU can potentially cause many problems in the IS-IS
   networks ranging from
   networks, including bouncing adjacencies to black hole or adjacencies, blackholing, and even some
   form of Denial of Service Denial-of-Service (DoS) attacks as explained in Section 2.
   This problem is also discussed in security consideration the Security Considerations
   section, in the context of cryptographic authentication work as
   described in [RFC5304] and in [RFC5310].

   Currently, there is no mechanism to protect IS-IS HELLO Hello (IIH) PDUs (IIHs)
   and Sequence number Number PDUs (SNPs) from the replay attacks.  However, Link
   State PDUs (LSPs) have a sequence number in the LSP header as defined
   in [ISO10589], with which it they can effectively mitigate
   the intra-session
   replay attacks.  But, LSPs are still susceptible to inter-session
   replay attacks.

   This document defines the Extended Sequence number Number (ESN) TLV to
   protect
   Intermediate System to Intermediate System (IS-IS) IS-IS PDUs from replay attacks.

   The new ESN TLV defined here thwart thwarts these threats and can be
   deployed with the authentication mechanism as mechanisms specified in [RFC5304]
   and in [RFC5310] for a more secure network.

   Replay attacks can be effectively mitigated by deploying a group key
   management protocol (being developed as defined in [I-D.yeung-
   g-ikev2] [GROUP-IKEv2] and [I-D.hartman-karp-mrkmp])
   [MRKMP]) with a frequent key change policy.  Currently, there is no
   such mechanism defined for IS-IS.  Even if such a mechanism is
   defined, usage of this TLV can be helpful to avoid replays before the
   keys are changed.

   Also, it is believed, believed that, even when such a key management system is
   deployed, there always will be some manual key based systems based on manual keying
   that co-
   exist coexist with KMP (Key Management Protocol) systems based systems.  The on key management protocols.  The ESN
   TLV defined in this document is more helpful for such deployments.

1.1.  Requirements Language

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in RFC 2119 [RFC2119].

1.2.  Acronyms

   CSNP    -  Complete Sequence Number PDU

   ESN     -  Extended Sequence Number

   IIH     -  IS-IS Hello PDU

   IS      -  Intermediate System

   KMP     -  Key Management Protocol (auto key management)

   LSP     -  IS-IS Link State PDU

   MKM     -  Manual Key management Protocols

   PDU     -  Protocol Data Unit
   PSNP    -  Partial Sequence Number PDU

   SNP     -  Sequence Number PDU

2.  Replay attacks Attacks and Impact on IS-IS networks Networks

   Replaying a captured protocol packet to cause damage is a common
   threat for any protocol.  Securing the packet with cryptographic
   authentication information alone cannot mitigate this threat
   completely.  This section explains the replay attacks and the their
   applicability of the same for to each IS-IS PDU.

2.1.  IIHs

   When an adjacency is brought up up, an IS sends an IIH packet with an
   empty neighbor list (TLV 6), which 6); it can be sent with or without
   authentication information.  Packets can be replayed later on the
   broadcast network which network, and this may cause all ISes ISs to bounce the
   adjacency, thus churning the network.  Note that mitigating replay is
   only possible when authentication information is present.

2.2.  LSPs

   Normal operation of the IS-IS update Process process as specified in
   [ISO10589] provides timely recovery from all LSP replay attacks.  Therefore
   Therefore, the use of the extensions defined in this document are is
   prohibited in LSPs.  Further discussion of the vulnerability of LSPs
   to replay attacks can be found in [I-D.ietf-
   karp-isis-analysis]. [ISIS-ANALYSIS].

2.3.  SNPs

   A replayed CSNP can result in the sending of unnecessary PSNPs on a
   given link.  A replayed CSNP or PSNP can result in unnecessary LSP
   flooding on the link.

3.  Extended Sequence Number TLV

   The Extended Sequence Number (ESN) TLV is composed of 1 octet for the
   Type, 1 octet that specifies the number of bytes in the Value field field,
   and a 12 byte 12-byte Value field.  This TLV is defined only for IIH and SNP
   PDUs.

   x CODE

   Code - 11.

   x LENGTH

   Length - total length of the value field, which is 12 bytes.

   x

   Value - 64-bit Extended Session Sequence Number (ESSN), which is
      followed by a 32 bit 32-bit, monotonically increasing per Packet Sequence
   Number (PSN). increasing, per-packet
      sequence number.

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+
   |    Type       |
   +-+-+-+-+-+-+-+-+
   |    Length     |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Extended Session Sequence Number (High Order (High-Order 32 Bits)      |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |    Extended Session Sequence Number (Low Order (Low-Order 32 Bits)       |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |             Packet Sequence Number (32 Bits)                  |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

           Figure 1: Extended Sequence Number (ESN) TLV

   The ESN TLV defined here is optional.  Though this is an optional
   TLV, this it can be mandatory on a link when 'verify' mode is enabled as
   specified in Section 5.1.  The ESN TLV MAY be present only in any IIH
   PDUs and SNP PDUs. SNPs.  A PDU with multiple ESN TLVs is invalid and MUST be
   discarded on receipt.

   The 64 bit 64-bit ESSN MUST be non-zero nonzero and MUST contain ever increasing a number that is
   increased whenever it is changed due any situation situation, as specified in
   Section 3.1.  Encoding the 64-bit unsigned integer ESSN value is a
   local matter matter, and implementations MAY use one of the alternatives
   provided in Appendix A.  Effectively, for each PDU which that contains the
   ESN TLV TLV, the 96 bit 96-bit unsigned integer value consisting of the 64 bit 64-bit
   ESSN and 32 bit 32-bit Packet Sequence Number (PSN) - -- where the ESSN is the
   higher order
   higher-order 64 bits - -- MUST be greater than the most recently
   received value in a PDU of the same type originated by the same IS.

3.1.  Sequence Number Wrap

   If the 32-bit Packet Sequence Number in the ESN TLV wraps or for the
   router performs a cold
   restart of the router, restart, the 64-bit ESSN value MUST be set
   higher than the previous value.  IS-IS implementations MAY use the
   guidelines provided in Appendix A for accomplishing this.

4.  Mechanism and Packet Encoding

   The encoding of the ESN TLV in each applicable IS-IS PDU is detailed
   below.  Please refer to Section 5 for appropriate operations on how
   to inter-op interoperate with legacy node(s) that do not support the
   extensions defined in this document.  If the received PDU with the
   ESN TLV is
   accepted accepted, then the stored value for the corresponding
   originator and PDU type MUST be updated with the latest value
   received.  Please note that level information is included in the PDU
   type.

4.1.  IIHs

   ESN TLV information is maintained for each type of IIH PDU being sent
   on a given circuit.  The procedures for encoding, verification verification, and
   sequence number wrap scenarios wrapping are explained in Section 3.

4.2.  SNPs

   A separate

   Separate CSNP/PSNP ESN TLV information is maintained per PDU type,
   per originator originator, and per link.  The procedures for encoding,
   verification
   verification, and sequence number wrap scenarios wrapping are explained in Section
   3.

5.  Backward Compatibility and Deployment

   The implementation and deployment of the ESN TLV can be done to
   support backward compatibility and gradual deployment in the network
   without requiring a flag day.  This feature can also be deployed for
   the links in a certain area of the network where the maximum security
   mechanism is needed, or it can be deployed for the entire network.

   The implementation SHOULD allow the configuration of ESN TLV feature features
   on each IS-IS link level.  The implementation SHOULD also allow
   operators to control the configuration of the 'send' and/or 'verify'
   feature of IS-IS PDUs for the links and for the node.  In this
   document, the 'send' operation mode is to include the ESN TLV in its own IS-IS PDUs;
   PDUs, and the 'verify' operation mode is to process the ESN TLV in the
   receiving IS-IS PDUs from neighbors.

   In the face of

   When an adversary doing an active attack, is actively attacking, it is possible to have
   inconsistent data view views in the network, if there is a considerable
   delay in enabling ESN TLV the 'verify' operation mode where nodes were configured to
   the 'send' mode, e.g., from the first
   node to the last node in the network or all nodes
   of a particular LAN
   segment, where 'send' mode is configured. segment.  This can happen happens primarily
   because, because replay
   PDUs can potentially be accepted by the nodes where the 'verify' operation mode
   is still not provisioned at the time of the attack.  To minimize such
   a window window, it is recommended that provisioning of 'verify' SHOULD be
   done in a timely fashion by the network operators.

5.1.  IIH  IIHs and SNPs

   On the link level, the ESN TLV involves the IIH PDUs and SNPs (both
   CSNP and PSNP).  The "send" 'send' and "verify" 'verify' modes described above can be
   set independently on each link and and, in the case of a broadcast network
   network, independently for on each level.

   To introduce ESN support without disrupting operations, ISs on a
   given interface are first configured to operate in 'send' mode.  Once
   all routers operating on an interface are operating in 'send' mode mode,
   'verify' mode can be enabled on each IS.  Once 'verify' mode is set
   for an interface interface, all the IIH and SNP PDUs and SNPs being sent on that
   interface MUST contain the ESN TLV.  Any such PDU received without an
   ESN TLV MUST be discarded when 'verify' mode is enabled.  Similarly,
   to safely disable ESN support on a link, 'verify' mode is disabled on
   all ISs on the link.  Once 'verify' mode is disabled on all routers
   operating on an interface are
   disabled from 'verify' mode interface, 'send' mode can be disabled on each IS.
   Please refer to Section 5 for considerations on enabling or disabling
   'verify' mode on all ISs on a link.

6.  IANA Considerations

   A new TLV code point is codepoint, as defined in this document, has been assigned
   by IANA from the IS-IS "IS-IS TLV
   Codepoints Registry as defined in this document, Codepoints" registry.  It is referred to
   as the
   "Extended Extended Sequence Number" TLV, with Number TLV and has the following attributes:

      Type  Description

      Value  Name                   IIH  LSP  SNP  Purge
      ----
      -----  ---------------------  ---  ---  ---  -----
      11     ESN TLV                 Y    N    Y    N

                 Figure 2: IS-IS Codepoints Registry Entry                 y    n    y    n

7.  Security Considerations

   This document describes a mechanism to mitigate the replay attack
   threat as discussed in the Security Considerations section sections of
   [RFC5304] and in [RFC5310].  If an adversary interferes either does by not forward the
   forwarding packets or
   delay the same by delaying messages as specified described in Section
   3.3 of [RFC6862], the mechanism specified in this document cannot
   mitigate those threats.
   Also  Also, some of the threats as specified described in
   Section 2.3 of [I-D.ietf-
   karp-isis-analysis] [ISIS-ANALYSIS] are not addressable with the ESN TLV
   as specified in this document.  This document does not introduce any
   new security concerns to IS-IS or any other specifications referenced in this
   document.
   referenced.

8.  Contributors

   Authors would like  References

8.1.  Normative References

   [ISO10589] International Organization for Standardization,
              "Intermediate system to thank Les Ginsberg intermediate system intra-domain-
              routing routine information exchange protocol for his significant
   contribution use in detailed reviews and suggestions.

9.  Acknowledgements

   As some sort of sequence number mechanism to thwart protocol replays
   is a old mechanism, authors of this document do not make any claims
   on the originality of the overall protection idea described.  Authors
   are thankful for the review and the valuable feedback provided by
   Acee Lindem and Joel Halpern.  Thanks to Alia Atlas, Chris Hopps,
   Nevil Brownlee and Adam W.  Montville for their reviews and
   suggestions during IESG directorate review.  Authors would also thank
   Christer Holmberg, Ben Campbell, Barry Leiba, Stephen Farrell and
   Alvaro Retana for their reviews on this document.

10.  References

10.1.  Normative References

   [ISO10589]
              International Organization for Standardization,
              "Intermediate system to intermediate system intra-domain-
              routing routine information exchange protocol for use in
              conjunction with the
              conjunction with the protocol for providing the
              connectionless-mode Network Service (ISO 8473)", ISO/
              IEC ISO/IEC
              10589:2002, Second Edition, Nov. 2002.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119,
              DOI 10.17487/RFC2119, March 1997. 1997,
              <http://www.rfc-editor.org/info/rfc2119>.

   [RFC5905]  Mills, D., Martin, J., Ed., Burbank, J., and W. Kasch,
              "Network Time Protocol Version 4: Protocol and Algorithms
              Specification", RFC 5905, DOI 10.17487/RFC5905, June 2010.

10.2. 2010,
              <http://www.rfc-editor.org/info/rfc5905>.

8.2.  Informative References

   [I-D.hartman-karp-mrkmp]

   [MRKMP]    Hartman, S., Zhang, D., and G. Lebovitz, "Multicast Router
              Key Management Protocol (MaRK)", draft-hartman-karp-
              mrkmp-05 (work Work in progress), Progress,
              draft-hartman-karp-mrkmp-05, September 2012.

   [I-D.ietf-karp-isis-analysis]

   [ISIS-ANALYSIS]
              Chunduri, U., Tian, A., and W. Lu, "KARP IS-IS security
              analysis", draft-ietf-karp-isis-analysis-04 (work Work in
              progress), March Progress, draft-ietf-karp-isis-
              analysis-07, July 2015.

   [I-D.weis-gdoi-mac-tek]
              Weis, B. and S.

   [GROUP-IKEv2] Rowles, "GDOI Generic Message
              Authentication Code Policy", draft-weis-gdoi-mac-tek-03
              (work S., Yeung, A., Ed., Tran, P., and Y. Nir,
              "Group Key Management using IKEv2", Work in progress), September 2011. Progress,
              draft-yeung-g-ikev2-08, October 2014.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, DOI 10.17487/RFC5304, October 2008.
              2008, <http://www.rfc-editor.org/info/rfc5304>.

   [RFC5310]  Bhatia, M., Manral, V., Li, T., Atkinson, R., White, R.,
              and M. Fanto, "IS-IS Generic Cryptographic
              Authentication", RFC 5310, DOI 10.17487/RFC5310, February 2009.

   [RFC6518]  Lebovitz, G. and M. Bhatia, "Keying and Authentication for
              Routing Protocols (KARP) Design Guidelines", RFC 6518,
              February 2012.
              2009, <http://www.rfc-editor.org/info/rfc5310>.

   [RFC6862]  Lebovitz, G., Bhatia, M., and B. Weis, "Keying and
              Authentication for Routing Protocols (KARP) Overview,
              Threats, and Requirements", RFC 6862,
              DOI 10.17487/RFC6862, March 2013. 2013,
              <http://www.rfc-editor.org/info/rfc6862>.

   [RFC7474]  Bhatia, M., Hartman, S., Zhang, D., and A. Lindem, Ed.,
              "Security Extension for OSPFv2 When Using Manual Key
              Management", RFC 7474, DOI 10.17487/RFC7474, April 2015. 2015,
              <http://www.rfc-editor.org/info/rfc7474>.

Appendix A.  ESSN Encoding Mechanisms

   IS-IS nodes implementing this specification SHOULD use available
   mechanisms to preserve the 64-bit Extended Session Sequence Number's
   strictly increasing property, whenever it is changed for the deployed
   life of the IS-IS node (including cold restarts).

   This Appendix appendix provides only guidelines for achieving maintaining the same strictly
   increasing property of the 64-bit ESSN in the ESN TLV, and
   implementations can resort to any similar method as far long as strictly
   increasing this
   property of the 64-bit ESSN in ESN TLV is maintained.

A.1.  Using Timestamp Timestamps

   One mechanism for accomplishing this is by encoding the 64-bit ESSN
   as the system time represented in by a 64-bit unsigned integer value.
   This MAY be similar to the system timestamp encoding for the NTP long
   format as defined in Appendix A.4 of [RFC5905].  New  The new current time
   MAY be used when the IS-IS node loses its sequence number state
   including in when the Packet Sequence Number wrap scenarios. wraps.

   Implementations MUST make sure while encoding the 64-bit ESN value
   with the current system time, time that it should does not default to any previous
   value or some default node time of the system; system, especially after cold
   restarts or any other similar events.  In general general, system time must
   be preserved across cold restarts in order for this mechanism to be
   feasible.  One example of such implementation is to use a battery
   backed real-time clock (RTC).

A.2.  Using Non-Volatile Non-volatile Storage

   One other mechanism for accomplishing this would be is similar to the one as
   specified in [RFC7474], to [RFC7474] -- use the 64-bit ESSN as a wrap/boot count
   stored in non-volatile storage.  This value is incremented anytime
   the IS-IS node loses its sequence number state state, including in when the
   Packet Sequence Number wrap scenarios.

   The wraps.

   There is a drawback of to this approach per approach, which is described as follows
   in Section 8 of [RFC7474], if used is
   applicable here. [RFC7474].  It requires the IS-IS implementation to
   be able to save its boot count in non-volatile storage.  If the non-volatile non-
   volatile storage is ever repaired or router hardware is upgraded such
   that the contents are lost, keys MUST be changed to prevent replay
   attacks.

Appendix B.  Operational/Implementation consideration Considerations

   Since the ESN is maintained per interface, PDU type, per level originator, and per PDU
   type,
   link, this scheme can be useful for monitoring the health of the IS-
   IS
   IS-IS adjacency.  A Packet Sequence Number skip on that occurs upon
   receiving an IIH can be recorded by the neighbors which and can be used
   later to correlate with adjacency state changes over the interface.  For instance
   instance, in a multi-access media, all completely different issues on the
   network may be indicated when all neighbors have the record skips from the
   same IIH sender or versus when only one neighbor has the Packet Sequence Number skips can indicate
   completely different issues on the network.  Effective records skips.  For
   operational issues, effective usage of the TLV defined in this
   document for operational issues MAY also need more system information before making concrete conclusions and
   conclusions; defining all that information is beyond the scope of
   this document.

Acknowledgements

   As some sort of sequence number mechanism to thwart protocol replays
   is a old concept, the authors of this document do not make any claims
   on the originality of the overall protection idea described.  The
   authors are thankful for the review and the valuable feedback
   provided by Acee Lindem and Joel Halpern.  Thanks to Alia Atlas,
   Chris Hopps, Nevil Brownlee, and Adam W. Montville for their reviews
   and suggestions during IESG directorate review.  The authors also
   thank Christer Holmberg, Ben Campbell, Barry Leiba, Stephen Farrell,
   and Alvaro Retana for their reviews of this document.

Contributors

   The authors would like to thank Les Ginsberg for his significant
   contribution in detailed reviews and suggestions.

Authors' Addresses

   Uma Chunduri
   Ericsson Inc.
   300 Holger Way,
   San Jose, California  95134
   USA
   United States

   Phone: 408 750-5678
   Email: uma.chunduri@ericsson.com

   Wenhu Lu
   Ericsson Inc.
   300 Holger Way,
   San Jose, California  95134
   USA
   United States

   Email: wenhu.lu@ericsson.com

   Albert Tian
   Ericsson Inc.
   300 Holger Way,
   San Jose, California  95134
   USA
   United States

   Phone: 408 750-5210
   Email: albert.tian@ericsson.com

   Naiming Shen
   Cisco Systems, Inc.
   225 West Tasman Drive,
   San Jose, California  95134
   USA
   United States

   Email: naiming@cisco.com