[Docs] [txt|pdf] [Tracker] [WG] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-zheng-mpls-ldp-hello-crypto-auth) 00 01 02 03 04 05 06 07 08 09 10 RFC 7349

Network Working Group                                           L. Zheng
Internet-Draft                                                   M. Chen
Intended status: Standards Track                     Huawei Technologies
Expires: July 26, 2013                                         M. Bhatia
                                                          Alcatel-Lucent
                                                        January 22, 2013


                 LDP Hello Cryptographic Authentication
              draft-ietf-mpls-ldp-hello-crypto-auth-01.txt

Abstract

   This document introduces a new optional Cryptographic Authentication
   TLV that LDP can use to secure its Hello messages.  It secures the
   Hello messages against spoofing attacks and some well known attacks
   against the IP header.  This document describes a mechanism to secure
   the LDP Hello messages using National Institute of Standards and
   Technology (NIST) Secure Hash Standard family of algorithms.
































Zheng, et al.             Expires July 26, 2013                 [Page 1]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


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].

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 July 26, 2013.

Copyright Notice

   Copyright (c) 2013 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.














Zheng, et al.             Expires July 26, 2013                 [Page 2]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4

   2.  Cryptographic Authentication TLV . . . . . . . . . . . . . . .  6
     2.1.  Optional Parameter for Hello Message . . . . . . . . . . .  6
     2.2.  Cryptographic Authentication TLV Encoding  . . . . . . . .  6

   3.  Cryptographic Aspects  . . . . . . . . . . . . . . . . . . . .  8
     3.1.  Cryptographic Key  . . . . . . . . . . . . . . . . . . . .  8
     3.2.  Hash . . . . . . . . . . . . . . . . . . . . . . . . . . .  8
     3.3.  Result . . . . . . . . . . . . . . . . . . . . . . . . . .  9

   4.  Processing Hello Message Using Cryptographic Authentication  . 10
     4.1.  Transmission Using Cryptographic Authentication  . . . . . 10
     4.2.  Receipt Using Cryptographic Authentication . . . . . . . . 10

   5.  Security Considerations  . . . . . . . . . . . . . . . . . . . 11

   6.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12

   7.  Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 13

   8.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 14
     8.1.  Normative References . . . . . . . . . . . . . . . . . . . 14
     8.2.  Informative References . . . . . . . . . . . . . . . . . . 14

   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 15























Zheng, et al.             Expires July 26, 2013                 [Page 3]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


1.  Introduction

   The Label Distribution Protocol (LDP) [RFC5036] sets up LDP sessions
   that runs between LDP peers.  The peers could either be directly
   connected at the link level or could be multiple hops away.  An LDP
   Label Switching Router (LSR) could either be configured with the
   identity of its peers or could discover them using LDP Hello
   messages.  These messages are sent encapsulated in UDP addressed to
   "all routers on this subnet" or to a specific IP address.  Periodic
   Hello messages are also used to maintain the relationship between LDP
   peers necessary to keep the LDP session active.

   Unlike other LDP messages, the Hello messages are sent using UDP and
   not TCP.  This implies that these messages cannot use the security
   mechanisms defined for TCP [RFC5926].  Besides a note that some
   configuration may help protect against bogus discovery messages,
   [RFC5036] does not really provide any security mechanism to protect
   the Hello messages.

   Spoofing a Hello packet for an existing adjacency can cause the valid
   adjacency to time out and in turn can result in termination of the
   associated session.  This can occur when the spoofed Hello specifies
   a smaller Hold Time, causing the receiver to expect Hellos within
   this smaller interval, while the true neighbor continues sending
   Hellos at the previously agreed lower frequency.  Spoofing a Hello
   packet can also cause the LDP session to be terminated directly,
   which can occur when the spoofed Hello specifies a different
   Transport Address, other than the previously agreed one between
   neighbors.  Spoofed Hello messages have been observed and reported as
   a real problem in production networks
   [I-D.ietf-karp-routing-tcp-analysis].

   [RFC5036] describes that the threat of spoofed Basic Hellos can be
   reduced by accepting Basic Hellos only on interfaces to which LSRs
   that can be trusted are directly connected, and ignoring Basic Hellos
   not addressed to the "all routers on this subnet" multicast group.
   Spoofing attacks via Extended Hellos are a potentially more serious
   threat.  An LSR can reduce the threat of spoofed Extended Hellos by
   filtering them and accepting only those originating at sources
   permitted by an access list.  However, filtering using access lists
   requires LSR resource, and does not prevent IP-address spoofing.

   This document introduces a new Cryptographic Authentication TLV which
   is used in LDP Hello message as an optional parameter.  It enhances
   the authentication mechanism for LDP by securing the Hello message
   against spoofing attack.  It also introduces a cryptographic sequence
   number carried in the Hello messages that can be used to protect
   against replay attacks.  The LSRs could be configured to only accept



Zheng, et al.             Expires July 26, 2013                 [Page 4]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


   Hello messages from specific peers when authentication is in use.

   Using this Cryptographic Authentication TLV, one or more secret keys
   (with corresponding key IDs) are configured in each system.  For each
   LDP Hello packet, the key is used to generate and verify a HMAC Hash
   that is stored in the LDP Hello packet.  For cryptographic hash
   function, this document proposes to use SHA-1, SHA-256, SHA-384, and
   SHA-512 defined in US NIST Secure Hash Standard (SHS) [FIPS-180-3].
   The HMAC authentication mode defined in NIST FIPS 198 is used
   [FIPS-198].  Of the above, implementations MUST include support for
   at least HMAC-SHA-256 and SHOULD include support for HMAC-SHA-1 and
   MAY include support for either of HMAC-SHA-384 or HMAC-SHA-512.







































Zheng, et al.             Expires July 26, 2013                 [Page 5]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


2.  Cryptographic Authentication TLV

2.1.  Optional Parameter for Hello Message

   [RFC5036] defines the encoding for the Hello message.  Each Hello
   message contains zero or more Optional Parameters, each encoded as a
   TLV.  Three Optional Parameters are defined by [RFC5036].  This
   document defines a new Optional Parameter: the Cryptographic
   Authentication parameter.

   Optional Parameter               Type
   -------------------------------  --------
   IPv4 Transport Address           0x0401 (RFC5036)
   Configuration Sequence Number    0x0402 (RFC5036)
   IPv6 Transport Address           0x0403 (RFC5036)
   Cryptographic Authentication     0x0404 (this document, TBD by IANA)


   The Cryptographic Authentication TLV Encoding is described in section
   2.2.

2.2.  Cryptographic Authentication TLV Encoding

       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
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |0|0|        Auth (TBD)         |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Authentication Key ID                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Cryptographic Sequence Number (High Order 32 Bits)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Cryptographic Sequence Number (Low Order 32 Bits)       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                Authentication Data (Variable)                 |
      ~                                                               ~
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   - Type: TBD, Cryptographic Authentication

   - Length: Specifying the length in octets of the value field.

   - Auth Key ID: 32 bit field that identifies the algorithm and the
   secret key used to create the message digest carried in LDP payload.




Zheng, et al.             Expires July 26, 2013                 [Page 6]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


   - Cryptographic Sequence Number: 64-bit strictly increasing sequence
   number that is used to guard against replay attacks.  The 64-bit
   sequence number MUST be incremented for every LDP Hello packet sent
   by the LDP router.  Upon reception, the sequence number MUST be
   greater than the sequence number in the last LDP Hello packet
   accepted from the sending LDP neighbor.  Otherwise, the LDP packet is
   considered a replayed packet and dropped.

   LDP routers implementing this specification SHOULD use available
   mechanisms to preserve the sequence number's strictly increasing
   property for the deployed life of the LDP router (including cold
   restarts).  One mechanism for accomplishing this could be to use the
   high-order 32 bits of the sequence number as a wrap/boot count that
   is incremented anytime the LDP router loses its sequence number
   state.  Techniques such as sequence number space partitioning
   described above or non-volatile storage preservation can be used but
   are really beyond the scope of this specification.

   - Authentication Data:

   This field carries the digest computed by the Cryptographic
   Authentication algorithm in use.  The length of the Authentication
   Data varies based on the cryptographic algorithm in use, which is
   shown as below:

   Auth type        Length
   ---------------  ----------
   HMAC-SHA1        20 bytes
   HMAC-SHA-256     32 bytes
   HMAC-SHA-384     48 bytes
   HMAC-SHA-512     64 bytes




















Zheng, et al.             Expires July 26, 2013                 [Page 7]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


3.  Cryptographic Aspects

   In the algorithm description below, the following nomenclature, which
   is consistent with [FIPS-198], is used:

   - H is the specific hashing algorithm specified by Auth Type (e.g.
   SHA-256).

   - K is the Authentication Key for the Hello packet.

   - Ko is the cryptographic key used with the hash algorithm.

   - B is the block size of H, in octets.

        For SHA-1 and SHA-256: B == 64
        For SHA-384 and SHA-512: B == 128

   - L is the length of the hash outputs, in octets.

   - XOR is the exclusive-or operation.

   - Ipad is the byte 0x36 repeated B times.

   - Opad is the byte 0x5c repeated B times.

   - Apad is source IP address that the would be used when sending out
   the LDP packet, repeated L/4 times, where L is the length of the
   hash, measured in octets.

3.1.  Cryptographic Key

   As described in [RFC2104], the authentication key K can be of any
   length up to B. Applications that use keys longer than B bytes will
   first hash the key using H and then use the resultant L byte string
   as the actual key to HMAC.

   In this application, Ko is always L octets long.  If the
   Authentication Key (K) is L octets long, then Ko is equal to K. If
   the Authentication Key (K) is more than L octets long, then Ko is set
   to H(K).  If the Authentication Key (K) is less than L octets long,
   then Ko is set to the Authentication Key (K) with trailing zeros such
   that Ko is L octets long.

3.2.  Hash

   First, the Authentication Data field in the Cryptographic
   Authentication TLV is filled with the value Apad.  Then, to compute
   HMAC over the Hello packet it performs:



Zheng, et al.             Expires July 26, 2013                 [Page 8]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


   H(Ko XOR Opad || H(Ko XOR Ipad || (Hello Packet)))

   Hello Packet refers to the LDP Hello packet excluding the IP header.

3.3.  Result

   The resultant Hash becomes the Authentication Data that is sent in
   the Authentication Data field of the Cryptographic Authentication
   TLV.  The length of the Authentication Data field is always identical
   to the message digest size of the specific hash function H that is
   being used.








































Zheng, et al.             Expires July 26, 2013                 [Page 9]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


4.  Processing Hello Message Using Cryptographic Authentication

4.1.  Transmission Using Cryptographic Authentication

   Prior to transmitting Hello message, the Length in the Cryptographic
   Authentication TLV header is set as per the authentication algorithm
   that is being used.  It is set to 24 for HMAC-SHA-1, 36 for HMAC-SHA-
   256, 52 for HMAC-SHA-384 and 68 for HMAC-SHA-512.

   The Auth Key ID field is set to the ID of the current authentication
   key.  The HMAC Hash is computed as explained in Section 3.  The
   resulting Hash is stored in the Authentication Data field prior to
   transmission.  The authentication key MUST NOT be carried in the
   packet.

4.2.  Receipt Using Cryptographic Authentication

   The receiving LSR applies acceptability criteria for received Hellos
   using cryptographic authentication.  If the Cryptographic
   Authentication TLV is unknown to the receiving LSR, the received
   packet MUST be discarded according to Section 3.5.1.2.2 of [RFC5036].

   If the Auth Key ID field does not match the ID of a configured
   authentication key, the received packet MUST be discarded.

   If the cryptographic sequence number in the LDP packet is less than
   or equal to the last sequence number received from the same neighbor,
   the LDP packet MUST be discarded.

   Before the receiving LSR performs any processing, it needs to save
   the values of the Authentication Data field.  The receiving LSR then
   replaces the contents of the Authentication Data field with Apad,
   computes the Hash, using the authentication key specified by the
   received Auth Key ID field, as explained in Section 3.  If the
   locally computed Hash is equal to the received value of the
   Authentication Data field, the received packet is accepted for other
   normal checks and processing as described in [RFC5036].  Otherwise,
   if the locally computed Hash is not equal to the received value of
   the Authentication Data field, the received packet MUST be discarded.












Zheng, et al.             Expires July 26, 2013                [Page 10]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


5.  Security Considerations

   Section 1 of this document describes the security issues arising from
   the use of unauthenticated LDP Hello messages.  In order to address
   those issues, it is RECOMMENDED that all deployments use the
   Cryptographic Authentication TLV to authenticate the Hello messages.

   The quality of the security provided by the Cryptographic
   Authentication TLV depends completely on the strength of the
   cryptographic algorithm in use, the strength of the key being used,
   and the correct implementation of the security mechanism in
   communicating LDP implementations.  Also, the level of security
   provided by the Cryptographic Authentication TLV varies based on the
   authentication type used.

   It should be noted that the authentication method described in this
   document is not being used to authenticate the specific originator of
   a packet but is rather being used to confirm that the packet has
   indeed been issued by a router that has access to the Authentication
   Key.

   Deployments SHOULD use sufficiently long and random values for the
   Authentication Key so that guessing and other cryptographic attacks
   on the key are not feasible in their environments.  Furthermore, it
   is RECOMMENDED that Authentication Keys incorporate at least 128
   pseudo-random bits to minimize the risk of such attacks.  In support
   of these recommendations, management systems SHOULD support
   hexadecimal input of Authentication Keys.

   The mechanism described herein is not perfect and does not need to be
   perfect.  Instead, this mechanism represents a significant increase
   in the effort required for an adversary to successfully attack the
   LDP Hello protocol while not causing undue implementation,
   deployment, or operational complexity.

















Zheng, et al.             Expires July 26, 2013                [Page 11]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


6.  IANA Considerations

   The IANA is requested to as assign a new TLV from the "Multiprotocol
   Label Switching Architecture (MPLS) Label Switched Paths (LSPs)
   Parameters - TLVs" registry, "TLVs and sub-TLVs" sub- registry.

   Value   Meaning                            Reference
   -----   --------------------------------   ---------
   TBD     Cryptographic Authentication TLV   this document (sect 3.2)










































Zheng, et al.             Expires July 26, 2013                [Page 12]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


7.  Acknowledgements

   The authors would like to thank Liu Xuehu for his work on background
   and motivation for LDP Hello authentication.  The authors also would
   like to thank Adrian Farrel, Eric Rosen, Sam Hartman, Eric Gray,
   Kamran Raza and Acee Lindem for their valuable comments.

   We would also like to thank the authors of RFC 5709 from where we
   have taken most of the cryptographic computation procedures from.










































Zheng, et al.             Expires July 26, 2013                [Page 13]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


8.  References

8.1.  Normative References

   [FIPS-180-3]
              "Secure Hash Standard (SHS), FIPS PUB 180-3",
              October 2008.

   [FIPS-198]
              "The Keyed-Hash Message Authentication Code (HMAC), FIPS
              PUB 198", March 2002.

   [RFC2104]  Krawczyk, H., Bellare, M., and R. Canetti, "HMAC: Keyed-
              Hashing for Message Authentication", RFC 2104,
              February 1997.

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

   [RFC5036]  Andersson, L., Minei, I., and B. Thomas, "LDP
              Specification", RFC 5036, October 2007.

8.2.  Informative References

   [I-D.ietf-karp-routing-tcp-analysis]
              Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP and MSDP Issues According to KARP Design
              Guide", draft-ietf-karp-routing-tcp-analysis-06 (work in
              progress), December 2012.

   [RFC5926]  Lebovitz, G. and E. Rescorla, "Cryptographic Algorithms
              for the TCP Authentication Option (TCP-AO)", RFC 5926,
              June 2010.


















Zheng, et al.             Expires July 26, 2013                [Page 14]

Internet-Draft   LDP Hello Cryptographic Authentication     January 2013


Authors' Addresses

   Lianshu Zheng
   Huawei Technologies
   China

   Email: vero.zheng@huawei.com


   Mach(Guoyi) Chen
   Huawei Technologies
   China

   Email: mach.chen@huawei.com


   Manav Bhatia
   Alcatel-Lucent
   India

   Email: manav.bhatia@alcatel-lucent.com






























Zheng, et al.             Expires July 26, 2013                [Page 15]


Html markup produced by rfcmarkup 1.109, available from https://tools.ietf.org/tools/rfcmarkup/