[Search] [txt|pdf|bibtex] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: 00 01 02 03 04                                                
Working Group                                                U. Chunduri
Internet-Draft                                                     W. Lu
Intended status: Standards Track                                 A. Tian
Expires: September 13, 2012                                Ericsson Inc.
                                                                 N. Shen
                                                     Cisco Systems, Inc.
                                                          March 12, 2012


                   IS-IS Extended Sequence number TLV
            draft-chunduri-isis-extended-sequence-no-tlv-01

Abstract

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

Status of this Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on September 13, 2012.

Copyright Notice

   Copyright (c) 2012 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



Chunduri, et al.       Expires September 13, 2012               [Page 1]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


   described in the Simplified BSD License.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
     1.1.  Requirements Language  . . . . . . . . . . . . . . . . . .  4
     1.2.  Acronyms . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Replay attacks and Impact on IS-IS networks  . . . . . . . . .  4
     2.1.  Replay attacks . . . . . . . . . . . . . . . . . . . . . .  4
     2.2.  Impact of Replays  . . . . . . . . . . . . . . . . . . . .  5
   3.  Extended Sequence Number TLV . . . . . . . . . . . . . . . . .  5
     3.1.  Sequence Number Wrap . . . . . . . . . . . . . . . . . . .  7
   4.  Packet Encoding  . . . . . . . . . . . . . . . . . . . . . . .  7
     4.1.  IIHs . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.2.  LSPs . . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     4.3.  SNPs . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.3.1.  CSNPs  . . . . . . . . . . . . . . . . . . . . . . . .  8
       4.3.2.  PSNPs  . . . . . . . . . . . . . . . . . . . . . . . .  8
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  8
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . .  8
   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . .  8
   8.  Appendix A . . . . . . . . . . . . . . . . . . . . . . . . . .  9
     8.1.  Appendix A.1 . . . . . . . . . . . . . . . . . . . . . . .  9
     8.2.  Appendix A.2 . . . . . . . . . . . . . . . . . . . . . . .  9
   9.  Appendix B . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     9.1.  Operational/Implementation consideration . . . . . . . . . 10
   10. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10
     10.1. Normative References . . . . . . . . . . . . . . . . . . . 10
     10.2. Informative References . . . . . . . . . . . . . . . . . . 10
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11




















Chunduri, et al.       Expires September 13, 2012               [Page 2]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


1.  Introduction

   With the rapid development of new data center infrastructures, due to
   its flexibility and scalability attributes, ISIS has been adopted
   widely in various L2 and L3 routing deployment of the data centers
   for critical business operations.  At the meantime the SDN-enabled
   networks even though put more power to Internet applications and also
   make network management easier, it does raise the security
   requirement of network routing infrastructure to another level.

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

   A replayed IS-IS PDU can potentially cause many problems in the IS-IS
   networks ranging from bouncing adjacencies to black hole or even some
   form of Denial of Service (DoS) attacks as explained in Section 2.
   This problem is also discussed in security consideration 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 PDUs (IIHs)
   and Sequence number PDUs (SNPs) from the replay attacks.  However,
   Link State PDUs (LSPs) have sequence number in the LSP header as
   defined in [RFC1195], with which it can effectively mitigate the
   intra-session replay attacks.  But, LSPs are still susceptible to
   inter-session replay attacks.

   This document defines a new Extended Sequence Number (ESN) TLV to
   thwart these threats and can be deployed with authentication
   mechanism as specified in [RFC5304] and in [RFC5310] for a more
   secure network.

   Replay attacks can be effectively mitigated by deploying a group key
   management protocol (similar to as defined in [I-D.weis-gdoi-mac-
   tek], using GDOI [I-D.ietf-msec-gdoi-update]) with a frequent key
   change policy.  Currently, there is no such mechanism defined for
   routing protocols and one of the KARP WG goals is to define such
   mechanism eventually.  Even if such a mechanism is in use, usage of
   this TLV can be helpful to avoid replays before the keys are changed.

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






Chunduri, et al.       Expires September 13, 2012               [Page 3]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


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

   KMP     -  Key Management Protocol (auto key management)

   LSP     -  IS-IS Link State PDU

   MKM     -  Manual Key management Protocols

   PSNP    -  Partial Sequence Number PDU

   SNP     -  Sequence Number PDU


2.  Replay attacks and Impact on IS-IS networks

   This section explains the replay attacks and the applicability of the
   same for IS-IS networks.  Though this has been described in detail in
   KARP IS-IS gap analysis document, it is being restated below for
   completeness.

2.1.  Replay attacks

   Replaying a captured protocol packet to cause damage is a common
   threat for any protocol.  Securing the packet with cryptographic
   authentication information alone can not mitigate this threat
   completely.

   In intra-session replay attacks, a secured protocol packet of the
   current session is replayed, can cause damage if there is no other
   mechanism to confirm this is a replayed packet.

   In inter-session replay attacks, captured packet from one of the
   previous session can be replayed to cause the damage.  IS-IS packets
   are vulnerable to both these attacks as there is no sequence number
   verification for IIH packets, SNP packets and limited protection for
   LSPs.



Chunduri, et al.       Expires September 13, 2012               [Page 4]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


2.2.  Impact of Replays

   At the time of adjacency bring up an IS sends IIH packet with empty
   neighbor list (TLV 6) and with or with out the authentication
   information as per provisioned authentication mechanism.  If this
   packet is replayed later on the broadcast network all ISes in the
   broadcast network can bounce the adjacency to create a huge churn in
   the network.

   Today Link State PDUs (LSPs) have intra-session replay protection as
   LSP header contains 32-bit sequence number which is verified for
   every received packet against the local LSP database.  But, if the
   key is not changed, an adversary can cause an inter-session replay
   attack by replaying a old LSP with higher sequence number and fewer
   prefixes or fewer adjacencies.  This forces the receiver to accept
   and remove the routes from the routing table, which eventually causes
   traffic disruption to those prefixes.

   In broadcast networks a replayed Complete Sequence Number packet
   (CSNP) can force the receiver to request Partial Sequence Number
   packet (PSNP) in the network and similarly, a replayed PSNP can cause
   unnecessary LSP flood in the network.

   Please refer KARP IS-IS gap analysis document for further details.


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
   and an 8 or 12 byte Value field.

   x CODE - TBD.

   x LENGTH - total length of the value field, which is 12 bytes for
   IIH, SNP PDUs and 8 bytes for LSPs.

   x Value - 64-bit Extended Session Sequence Number (ESSN), which is
   present for all IS-IS PDUs followed 32 bit monotonically increasing
   per Packet Sequence Number (PSN).  PSN is not required for LSPs.











Chunduri, et al.       Expires September 13, 2012               [Page 5]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


        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 32 Bits)      |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    Extended Session Sequence Number (Low Order 32 Bits)       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |    (optional) Packet Sequence Number (32 Bits)                |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


               Figure 1: Extended Sequence Number (ESN) TLV

   The Extended Sequence Number (ESN) TLV Type is TBD.  Please refer to
   IANA Considerations, in Section 5 for more details.  Length indicates
   the length of the value field; which is 12 bytes for IIH and SNP PDUs
   and 8 bytes for LSPs.

   In order to provide protection against both inter-session and intra-
   session replay attacks, the IS-IS Extended Session Sequence Number
   (ESSN) is defined a 64-bits value; the value MUST contain ever
   increasing number in all IS-IS PDUs including LSPs whenever it is
   changed due any situation as specified in Section 3.1.

   The 32-bit Packet Sequence Number (PSN) MUST be set and increase
   monotonically for IIH or SNP PDUs sent by IS-IS router.  Upon
   reception, the Packet Sequence number MUST be greater than the last
   sequence number in the IIH or SNP PDUs accepted from the sending
   IS-IS router.  Otherwise, the IIH or SNP PDU is considered as
   replayed PDU and dropped.

   As LSPs contain 32-bit sequence number field already in the LSP
   header, Packet Sequence Number in the ESN TLV MUST be omitted by
   setting the length field to 8 bytes and implementations continue to
   refer the header sequence number for all encoding and validation
   purposes.

   The ESN TLV defined here is optional.  The ESN TLV MAY present in any
   IS-IS PDU.  If present and authentication is in use this TLV MUST be
   included as part of the authentication data to calculate the digest.
   A sender MUST only transmit a single ESN TLV in a IS-IS PDU.






Chunduri, et al.       Expires September 13, 2012               [Page 6]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


3.1.  Sequence Number Wrap

   If the 32-bit Packet Sequence Number in ESN TLV and for LSPs the 32-
   bit header sequence number wraps; or session is refreshed; or even
   for the cold restarts the 64-bit ESSN value MUST be set higher than
   the previous value.  IS-IS implementations MAY use guidelines
   provided in Section 8 for accomplishing this.


4.  Packet Encoding

   The ESN TLV defined in this document is optional and the encoding and
   decoding of this TLV in each IS-IS PDU is as detailed below.

4.1.  IIHs

   The IIH ESN TLV information is maintained per IS-IS interface and per
   level.  For a broadcast interface, it can have two sets of ESN TLV
   information, if the circuit belongs to both level-1 and level-2.  For
   point-to-point (P2P) interface, only one ESN TLV information is
   needed.  This TLV information can be maintained as part of the
   adjacency state.

   While transmitting, the 64-bit ESSN MUST always be started with a non
   zero number and MAY use the guidelines as specified in Section 8 to
   encode this 64-bit value.  The 32-bit PSN starts from 1 and increases
   monotonically for every subsequent packet.

   While receiving, the 64-bit ESSN MUST always be either same or higher
   than the stored value in the adjacency state.  Similarly, the 32-bit
   PSN MUST be higher than the stored value in the adjacency state.  If
   the PDU is accepted then the adjacency state should be updated with
   the last received IIH PDU's ESN TLV information.

   For an adjacency refresh or the 32-bit PSN wrap the associated higher
   order 64-bit ESSN MUST always be higher than the previous value and
   the lower order 32-bit packet sequence number starts all over again.

4.2.  LSPs

   For LSPs, while originating, the 64-bit ESSN MUST always be started
   with a non zero number and MAY use the guidelines as specified in
   Section 8 for encoding this value.

   While receiving, the 64-bit Extended Sequence Number MUST always be
   either same or higher than the stored value in the LSP database.
   This document does not specify any changes for the existing LSP
   header 32-bit sequence number validation mechanism.



Chunduri, et al.       Expires September 13, 2012               [Page 7]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


4.3.  SNPs

4.3.1.  CSNPs

   In broadcast networks, only Designated Intermediate System (DIS) CSNP
   ESN TLV information is maintained per adjacency (per level) similar
   to IIH ESN TLV information.  The procedure for encoding, verification
   and sequence number wrap scenarios are similar as explained in
   Section 4.1, except separate DIS ESN TLV information should be used.
   In case of DIS change all adjacencies in the broadcast network MUST
   reflect new DIS's CSNP ESN TLV information in the adjacency and
   should be used for encoding/verification.

   In P2P networks, CSNP ESN TLV information is maintained per adjacency
   similar to IIH ESN TLV information.  The procedure for encoding,
   verification and sequence number wrap scenarios are similar as
   explained in Section 4.1, except separate CSNP ESN TLV information
   should be used.

4.3.2.  PSNPs

   In both broadcast and P2P networks, PSNP ESN TLV information is
   maintained per adjacency (per level) similar to IIH ESN TLV
   information.  The procedure for encoding, verification and sequence
   number wrap scenarios are similar as explained in Section 4.1, except
   separate PSNP ESN TLV information should be used.


5.  IANA Considerations

   This document requests that IANA allocate from the IS-IS TLV
   Codepoints Registry a new TLV, referred to as the "Extended Sequence
   Number" TLV, with the following attributes: IIH = y, LSP = y, SNP =
   y, Purge = y.


6.  Security Considerations

   This document describes a mechanism to the replay attack threat as
   discussed in the Security Considerations section of [RFC5304] and in
   [RFC5310].  This document does not introduce any new security
   concerns to IS-IS or any other specifications referenced in this
   document.


7.  Acknowledgements

   The authors of this document do not make any claims on the



Chunduri, et al.       Expires September 13, 2012               [Page 8]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


   originality of the ideas described.  Authors are thankful for the
   review and the valuable feedback provided by Acee Lindem and Joel
   Halpern.


8.  Appendix A

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

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

8.1.  Appendix A.1

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

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

8.2.  Appendix A.2

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

   The drawback of this approach per Section 6 of [I-D.ietf-ospf-
   security-extension-manual-keying], if used is applicable here.  The
   only drawback is, it requires the IS-IS implementation to be able to
   save its boot count in non-volatile storage.  If the non-volatile
   storage is ever repaired or upgraded such that the contents are lost,
   keys MUST be changed to prevent replay attacks.



Chunduri, et al.       Expires September 13, 2012               [Page 9]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


9.  Appendix B

9.1.  Operational/Implementation consideration

   Since the ESN is maintained per interface, per level and per packet
   type, this scheme can be useful for monitoring the health of the ISIS
   adjacency.  A Packet Sequence Number skip on IIH can be recorded by
   the neighbors which can be used later to correlate with adjacency
   state changes over the interface.  For instance in a multi-access
   media, all the neighbors have the skips from the same IIH sender or
   only one neighbor has the Packet Sequence Number skips can indicate
   completely different issues on the network.


10.  References

10.1.  Normative References

   [RFC1195]  Callon, R., "Use of OSI IS-IS for routing in TCP/IP and
              dual environments", RFC 1195, December 1990.

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.

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

10.2.  Informative References

   [I-D.ietf-karp-threats-reqs]
              Lebovitz, G., Bhatia, M., and R. White, "The Threat
              Analysis and Requirements for Cryptographic Authentication
              of Routing Protocols' Transports",
              draft-ietf-karp-threats-reqs-03 (work in progress),
              June 2011.

   [I-D.ietf-msec-gdoi-update]
              Weis, B., Rowles, S., and T. Hardjono, "The Group Domain
              of Interpretation", draft-ietf-msec-gdoi-update-11 (work
              in progress), August 2011.

   [I-D.ietf-ospf-security-extension-manual-keying]
              Bhatia, M., Hartman, S., Zhang, D., and A. Lindem,
              "Security Extension for OSPFv2 when using Manual Key
              Management",
              draft-ietf-ospf-security-extension-manual-keying-00 (work
              in progress), May 2011.



Chunduri, et al.       Expires September 13, 2012              [Page 10]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


   [I-D.weis-gdoi-mac-tek]
              Weis, B. and S. Rowles, "GDOI Generic Message
              Authentication Code Policy", draft-weis-gdoi-mac-tek-02
              (work in progress), March 2011.

   [RFC5304]  Li, T. and R. Atkinson, "IS-IS Cryptographic
              Authentication", RFC 5304, October 2008.

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

   [RFC6518]  Lebovitz, G. and M. Bhatia, "Keying and Authentication for
              Routing Protocols (KARP) Design Guidelines", RFC 6518,
              February 2012.


Authors' Addresses

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

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


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

   Email: wenhu.lu@ericsson.com


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

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





Chunduri, et al.       Expires September 13, 2012              [Page 11]


Internet-Draft     IS-IS Extended Sequence number TLV         March 2012


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

   Email: naiming@cisco.com












































Chunduri, et al.       Expires September 13, 2012              [Page 12]