LDP Hello Cryptographic Authentication
draft-zheng-mpls-ldp-hello-crypto-auth-03

Network Working Group                                           L. Zheng
Internet-Draft                                                   M. Chen
Intended status: Standards Track                     Huawei Technologies
Expires: September 10, 2012                                    M. Bhatia
                                                          Alcatel-Lucent
                                                           March 9, 2012

                 LDP Hello Cryptographic Authentication
             draft-zheng-mpls-ldp-hello-crypto-auth-03.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 how the National
   Institute of Standards and Technology (NIST) Secure Hash Standard
   family of algorithms should be used to secure LDP Hello messages.

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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
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   This Internet-Draft will expire on September 10, 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
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   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

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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.  References . . . . . . . . . . . . . . . . . . . . . . . . 14
     8.3.  Informative References . . . . . . . . . . . . . . . . . . 14

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

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1.  Introduction

   The Label Distribution Protocol (LDP) [RFC5036] utilizes LDP sessions
   that run between LDP peers.  The peers may be directly connected at
   the link level or may be remote.  A label switching router (LSR) that
   speaks LDP may be configured with the identity of its peers or may
   discover them using the LDP Hello message sent encapsulated in UDP
   that may be 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 all other LDP messages, the Hello messages are sent using UDP
   not TCP.  This means that they cannot benefit from the security
   mechanisms available with TCP.  [RFC5036] does not provide any
   security mechanisms for use with Hello messages except to note that
   some configuration may help protect against bogus discovery events.

   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 is observed and reported as real
   problem in production networks.  Spoofed Hello attack has been
   identified in [I-D.ietf-karp-routing-tcp-analysis] and need to be
   addressed.

   As described in [RFC5036], the threat of spoofed Basic Hellos can be
   reduced by accepting Basic Hellos only on interfaces to which LSRs
   that can be trusted, and ignoring Basic Hellos not addressed to the
   "all routers on this subnet" multicast group.  Spoofing attacks via
   Extended Hellos are 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, performing the filtering using access lists requires
   LSR resource, and the LSR is still vulnerable to the IP source
   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, and an LSR can be configured to only accept
   Hello messages from specific peers when authentication is in use.

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   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.

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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 (0x0404)       |             Length            |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                  Authentication Key ID                        |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Cryptographic Sequence Number (High Order 32 Bits)      |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |       Cryptographic Sequence Number (Low Order 32 Bits)       |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
      |                                                               |
      |                Authentication Data (Variable)                 |
      ~                                                               ~
      |                                                               |
      |                                                               |
      +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

   - Type: 0x0404 (TBD by IANA), 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.

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   - 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 packet sent by the
   LDP router.  Upon reception, the sequence number MUST be greater than
   the sequence number in the last LDP packet accepted from the sending
   LDP neighbor.  In case it isnt, the LDP packet is considered a
   replayed packet and is 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).  Techniques such as sequence number space partitioning and
   non-volatile storage preservation can be used but are 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 used, 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

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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:

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   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.

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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,
   the received packet MUST be discarded.

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5.  Security Considerations

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

   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.

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6.  IANA Considerations

   IANA maintains a registry of LDP message parameters with a sub-
   registry to track LDP TLV Types.  This document requests IANA to
   assign a new TLV type as follows for Cryptographic Authenticatio.
   This document suggests 0x0404 to foster pre-standard implementations.

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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, Thomas Nadeau, So Ning, Eric Rosen and
   Sam Hartman 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.

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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.  References

8.3.  Informative References

   [I-D.ietf-karp-routing-tcp-analysis]
              Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Security According to KARP Design
              Guide", draft-ietf-karp-routing-tcp-analysis-00 (work in
              progress), June 2011.

   [RFC2385]  Heffernan, A., "Protection of BGP Sessions via the TCP MD5
              Signature Option", RFC 2385, August 1998.

   [RFC4634]  Eastlake, D. and T. Hansen, "US Secure Hash Algorithms
              (SHA and HMAC-SHA)", RFC 4634, July 2006.

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

   [RFC5709]  Bhatia, M., Manral, V., Fanto, M., White, R., Barnes, M.,
              Li, T., and R. Atkinson, "OSPFv2 HMAC-SHA Cryptographic
              Authentication", RFC 5709, October 2009.

   [RFC5880]  Katz, D. and D. Ward, "Bidirectional Forwarding Detection
              (BFD)", RFC 5880, June 2010.

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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

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