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Versions: (draft-ertekin-rohc-ipsec-extensions-hcoipsec) 00 01 02 03 04 05 06 07 08 RFC 5858

Network Working Group                                         E. Ertekin
Internet-Draft                                                  M. Casey
Expires: July 3, 2008                                        J. Pezeshki
                                                             C. Christou
                                                     Booz Allen Hamilton
                                                       December 31, 2007


    IPsec Extensions to Support Robust Header Compression over IPsec
                              (RoHCoIPsec)
              draft-ietf-rohc-ipsec-extensions-hcoipsec-01

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Copyright Notice

   Copyright (C) The IETF Trust (2007).

Abstract

   Integrating RoHC with IPsec (RoHCoIPsec) offers the combined benefits
   of IP security services and efficient bandwidth utilization.  Before
   this can be realized, however, several extensions to the Security
   Policy Database (SPD), the Security Association Database (SAD), and
   the IPsec process are required.  This document describes the IPsec



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   extensions required to support RoHCoIPsec.


Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Extensions to IPsec Databases  . . . . . . . . . . . . . . . .  3
     2.1.  Security Policy Database (SPD) . . . . . . . . . . . . . .  3
     2.2.  Security Association Database (SAD)  . . . . . . . . . . .  4
   3.  Extensions to IPsec Processing . . . . . . . . . . . . . . . .  5
     3.1.  Addition to the IANA Protocol Numbers Registry . . . . . .  5
     3.2.  Verifying the Integrity of Decompressed Packet Headers . .  5
       3.2.1.  ICV Computation and Integrity Verification . . . . . .  5
     3.3.  Nested IPComp and RoHCoIPsec Processing  . . . . . . . . .  6
   4.  Security Considerations  . . . . . . . . . . . . . . . . . . .  6
   5.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  7
   6.  Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  7
   7.  References . . . . . . . . . . . . . . . . . . . . . . . . . .  7
     7.1.  Normative References . . . . . . . . . . . . . . . . . . .  7
     7.2.  Informative References . . . . . . . . . . . . . . . . . .  8
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . .  8
   Intellectual Property and Copyright Statements . . . . . . . . . . 10





























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1.  Introduction

   Using IPsec ([IPSEC]) protection offers various security services for
   IP traffic.  However, for tunnel-mode security associations, these
   benefits come at the cost of additional packet headers, which
   increase packet overhead.  As described in [ROHCOIPSEC], Robust
   Header Compression (RoHC [ROHC]) can be used with IPsec to reduce the
   overhead associated with IPsec-protected packets.

   IPsec-protected traffic is carried between peers by Security
   Associations (SAs), whose parameters are negotiated on a case-by-case
   basis.  The Security Policy Database (SPD) specifies the services
   that are to be offered to IP datagrams, and the parameters associated
   with SAs that have been established are stored in the Security
   Association Database (SAD).  To fully integrate RoHC and IPsec,
   various extensions to the SPD and SAD that incorporate RoHC-relevant
   parameters are required.

   In addition, three extensions to the IPsec processing methodology are
   required.  First, a mechanism for identifying RoHC packets must be
   defined.  Second, a mechanism is required to ensure the integrity of
   the decompressed packet.  Finally, the order of the inbound and
   outbound processing must be enumerated when nesting IP Compression
   (IPComp [IPCOMP]), RoHC, and IPsec processing.


2.  Extensions to IPsec Databases

   The following subsections specify extensions to the SPD and the SAD
   to support RoHCoIPsec.

2.1.  Security Policy Database (SPD)

   In general, the SPD is responsible for specifying the security
   services that are offered to IP datagrams.  Entries in the SPD
   specify how to derive the corresponding values for SAD entries.  To
   support RoHC, the SPD must be extended to include per-channel RoHC
   parameters.  Together, the existing IPsec SPD parameters and the RoHC
   parameters will dictate packet disposition for traffic that is to be
   compressed, and subsequently protected by IPsec.

   The fields contained within each SPD entry are defined in [IPSEC],
   Section 4.4.1.2.  To support RoHC, several processing info fields
   must be added to the SPD; these fields contain information regarding
   the RoHC profiles and channel parameters supported by the local RoHC
   instance.  In addition, a field within the SPD entry is required to
   store a list of integrity algorithms, supported by the RoHCoIPsec
   instance.  This field will be used to negotiate an integrity



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   algorithm to ensure that packet headers are properly decompressed
   (see Section 3.2).

   The per-channel configuration parameters required for RoHC in the SPD
   are as follows (note that this information must only be included in
   the SPD if the processing info field is set to PROTECT, and if the
   IPsec mode is set to tunnel mode):

      MAX_CID: The highest context ID number to be used by the
      compressor.  MAX_CID must be at least 0 and at most 16383 (The
      value 0 implies having one context).  The suggested value for
      MAX_CID is 15.

      PROFILES: This indicates the RoHC profiles supported by the
      decompressor.  The list of possible values this field may assume
      is defined in the [ROHCPROF] registry.

      MRRU: The size of the largest reconstructed unit that the
      decompressor is expected to reassemble from segments.  In general,
      is not anticipated that a RoHC over IPsec instance will use RoHC
      segmentation features.  Consequently, the suggested value for MRRU
      is 0.

      MAX_HEADER: The largest header size (in octets) that can be
      compressed.  Note that the four RoHC profiles defined in RFC 3095
      do not provide for a MAX_HEADER parameter.  The parameter
      MAX_HEADER is therefore without consequence in these profiles.
      Other profiles (e.g., ones based on RFC 2507) can make use of the
      parameter by explicitly referencing it.

   Note: The RoHC LARGE_CIDS channel parameter is set implicitly, based
   on the value of MAX_CID.  Furthermore, the RoHC FEEDBACK_FOR channel
   parameter is set implicitly to the RoHC channel associated with the
   SA in the reverse direction.  Because both of these RoHC channel
   parameters are set implicitly, they are not stored in the SPD.

2.2.  Security Association Database (SAD)

   Each entry within the SAD defines the parameters associated with each
   established SA.  Unless if the "populate from packet" (PFP) flag is
   asserted for a particular field, SAD entries are determined by the
   corresponding SPD entries during the creation of the SA.

   The data items contained within the SAD are defined in [IPSEC],
   Section 4.4.2.1.  To support RoHC, this list of data items is
   augmented to include a "RoHC Data Item" field that defines the RoHC
   parameters.  These parameters (i.e., MAX_CID, PROFILES, MRRU, and
   MAX_HEADER) are enumerated above in Section 2.1.  In addition, the



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   FEEDBACK_FOR parameter is also included, which is associated with the
   SA in the reverse direction.  Furthermore, two additional datas items
   are required to store the Integrity Algorithm and respective key that
   is to be used to ensure that packets are properly decompressed (see
   Section 3.2).  These "RoHC Data Item" values may be initialized
   manually (i.e., administratively configured for manual SAs), or
   initialized via a key exchange protocol (e.g.  IKEv2 [IKEV2]) that
   has been extended to support the negotiation of RoHC parameters
   [IKEV2EXT].


3.  Extensions to IPsec Processing

3.1.  Addition to the IANA Protocol Numbers Registry

   In order to demultiplex header-compressed from uncompressed traffic
   on a RoHC-enabled SA, a "RoHC" value must be reserved in the IANA
   Protocol Numbers registry.  If an outbound packet has a compressed
   header, the Next Header field of the security protocol header (e.g.,
   AH [AH], ESP [ESP]) must be set to the "RoHC" protocol identifer.  If
   the packet header has not been compressed, the Next Header field
   remains unaltered.  Conversely, for an inbound packet, the value of
   the security protocol Next Header field is checked to determine if
   the packet maintains a RoHC header.

3.2.  Verifying the Integrity of Decompressed Packet Headers

   In order to ensure that the RoHC compressed packet is decompressed
   correctly, RoHCoIPsec will use an Integrity Algorithm (and respective
   key) to compute a second Integrity Check Value (ICV) for the
   uncompressed packet.  This ICV will be prepended to the header-
   compressed RoHC-compressed packet.  At the decompresser, the
   decompressed packet will be used with the Integrity Algorithm (and
   its respective key) to compute a value that will be compared to the
   ICV.  If these values are not identical, the decompressed packet must
   be dropped by the decompressor.

3.2.1.  ICV Computation and Integrity Verification

   In order to correctly verify the integrity of the decompressed
   packets, the processing steps for RoHCoIPsec must be implemented in a
   specific order, as given below.

   For outbound packets that are to be processed by RoHC:
   o  An ICV is computed for the uncompressed packet via RoHCoIPsec's
      Integrity Algorithm (and respective key)





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   o  The packet is compressed by the RoHC process
   o  The ICV is prepended to the beginning of the compressed packet (in
      front of the RoHC header)
   o  The security protocol is applied to the packet

   For inbound packets that are to be decompressed by RoHC:
   o  A packet received on a RoHC-enabled SA is IPsec-processed
   o  The packet is decompressed by the RoHC process
   o  The decompressed packet is used with the Integrity Algorithm (and
      its respective key) to compute a value that is compared to the ICV
      (if these two values differ, the packet is dropped)

3.3.  Nested IPComp and RoHCoIPsec Processing

   IPComp ([IPCOMP]) is another mechanism that can be implemented to
   reduce the size of an IP datagram.  If IPComp and RoHCoIPsec are
   implemented in a nested fashion, the order of the outbound and
   inbound processing steps must be carefully enumerated.

   For outbound packets that are to be processed by IPcomp and RoHC:
   o  The ICV is computed for the uncompressed packet, and the
      appropriate RoHC compression profile is applied to the packet
   o  IPComp is applied, and the packet is sent to the IPsec process
   o  The security protocol is applied to the packet

   Conversely, for inbound packets that are to be both RoHC- and IPcomp-
   decompressed:
   o  A packet received on a RoHC-enabled SA is IPsec-processed
   o  The datagram is decompressed based on the appropriate IPComp
      algorithm
   o  The packet is sent to the RoHC module for header decompression and
      integrity verification


4.  Security Considerations

   A malfunctioning RoHC compressor (i.e., the compressor located at the
   ingress of the IPsec tunnel) has the ability to send packets to the
   decompressor (i.e., the decompressor located at the egress of the
   IPsec tunnel) that do not match the original packets emitted from the
   end-hosts.  Such a scenario will result in a decreased efficiency
   between compressor and decompressor.  Furthermore, this may result in
   Denial of Service, as the decompression of a significant number of
   invalid packets may drain the resources of an IPsec device.

   In addition, some RoHCoIPsec implementations may allow an attacker to
   identify new traffic flows by monitoring the relative size of the
   encrypted packets (i.e. a group of "long" packets, followed by a long



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   series of "short" packets may indicate a new flow for some RoHCoIPsec
   implementations).  To mitigate this concern, RoHC padding mechanisms
   may be used to arbitrarily add padding to transmitted packets to
   randomize packet sizes.


5.  IANA Considerations

   IANA is requested to allocate one value within the "Protocol Numbers"
   registry [PROTOCOL] for "RoHC".  This value will be used to indicate
   that the next level protocol header is a RoHC header.


6.  Acknowledgments

   The authors would like to thank Mr. Sean O'Keeffe, Mr. James Kohler,
   Ms. Linda Noone of the Department of Defense, and Mr. A. Rich Espy of
   OPnet for their contributions and support for developing this
   document.  In addition, the authors would like to thank Mr. Rohan
   Jasani for his valuable assistance.  Finally, the authors would like
   to thank the following for their numerous reviews and comments to
   this document:

   o  Dr. Stephen Kent
   o  Dr. Carsten Bormann
   o  Mr. Lars-Erik Jonnson
   o  Mr. Pasi Eronen


7.  References

7.1.  Normative References

   [IPSEC]    Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [ROHCOIPSEC]
              Ertekin, E. and C. Christou, "Integration of Header
              Compression over IPsec Security Associations", work in
              progress , February 2007.

   [ROHC]     Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
              Hannu, H., Jonsson, L., Hakenberg, R., Koren, T., Le, K.,
              Liu, Z., Martensson, A., Miyazaki, A., Svanbro, K.,
              Wiebke, T., Yoshimura, T., and H. Zheng, "RObust Header
              Compression (ROHC): Framework and four profiles: RTP, UDP,
              ESP, and uncompressed", RFC 3095, July 2001.




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   [IPCOMP]   Shacham, A., Monsour, R., Pereira, and Thomas, "IP Payload
              Compression Protocol (IPComp)", RFC 3173, September 2001.

   [IKEV2]    Kaufman, C., "Internet Key Exchange (IKEv2) Protocol",
              RFC 4306, December 2005.

   [IKEV2EXT]
              Pezeshki, J., Ertekin, E., and C. Christou, "Extensions to
              IKEv2 to Support Robust Header Compression over IPsec
              (RoHCoIPsec)", work in progress , February 2007.

   [AH]       Kent, S., "IP Authentication Header", RFC 4302,
              December 2005.

   [ESP]      Kent, S., "IP Encapsulating Security Payload (ESP)",
              RFC 4303, December 2005.

7.2.  Informative References

   [ROHCPROF]
              "RObust Header Compression (ROHC) Profile Identifiers",
              www.iana.org/assignments/rohc-pro-ids , October 2005.

   [PROTOCOL]
              IANA, ""Assigned Internet Protocol Numbers", IANA registry
              at: http://www.iana.org/assignments/protocol-numbers".


Authors' Addresses

   Emre Ertekin
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171
   US

   Email: ertekin_emre@bah.com


   Michele Casey
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171
   US

   Email: casey_michele@bah.com





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   Jonah Pezeshki
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171
   US

   Email: pezeshki_jonah@bah.com


   Chris Christou
   Booz Allen Hamilton
   13200 Woodland Park Dr.
   Herndon, VA  20171
   US

   Email: christou_chris@bah.com



































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