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DICE                                                     D. Migault (Ed)
Internet-Draft                                                    Orange
Intended status: Standards Track                              C. Bormann
Expires: January 24, 2015                        Universitaet Bremen TZI
                                                           July 23, 2014


                   IPsec/ESP for Application Payload
          draft-mglt-dice-ipsec-for-application-payload-00.txt

Abstract

   This document is a strawman specification describing how IPsec/ESP
   could be used to secure application payloads, in particular to enable
   multicast applications where DTLS would be used for unicast.

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
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   This Internet-Draft will expire on January 24, 2015.

Copyright Notice

   Copyright (c) 2014 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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   described in the Simplified BSD License.




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Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements notation . . . . . . . . . . . . . . . . . .   3
   2.  State of the Art  . . . . . . . . . . . . . . . . . . . . . .   3
   3.  UDP-Encapsulation Header  . . . . . . . . . . . . . . . . . .   5
   4.  Removing Transport Header . . . . . . . . . . . . . . . . . .   6
   5.  Additional Compression  . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   7
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   7
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   7
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   7
     8.2.  Informational References  . . . . . . . . . . . . . . . .   8
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   8

1.  Introduction

   [I-D.keoh-dice-multicast-security] defines a way to protect multicast
   traffic against group outsiders using a modified DTLS record
   protocol.  Reservations have been voiced about modifying DTLS this
   way without strengthening security by adding data origin
   authentication.

   However, many applications do not require this additional security.
   One protocol that already supports group-level security for multicast
   is IPsec.

   This document discusses how IPsec can be used to secure data at the
   application layer.  The resulting packet structure is expected to
   resemble a DTLS flavor as represented in Figure 1.

          +--------+-------------------------------------------------+
          |        | +--------+------------------------------------+ |
          |        | |        | +-------------+------------------+ | |
          |        | |        | |             | +--------------+ | | |
          |   IP   | |   UDP  | |  Security   | | Application  | | | |
          | header | | header | |  Header     | |     Data     | | | |
          |        | |        | |             | +--------------+ | | |
          |        | |        | +-------------+------------------+ | |
          |        | +--------+------------------------------------+ |
          +--------+-------------------------------------------------+

                    Figure 1: Securing Application Data








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1.1.  Requirements notation

   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 [RFC2119].

2.  State of the Art

   IPsec/ESP [RFC4303] has been designed to secure IP payload according
   to two different modes: the transport mode and the tunnel mode.
   Figure 2 represents an non protected UDP packet that is protected
   with IPsec/ESP.  UDP is chosen as an example and could be any other
   transport mode like TCP or SCTP, or ANY for unknown transport.
   Figure 3 illustrates how IPsec/ESP secures the non protected packet
   using the transport mode and Figure 4 illustrates how IPsec/ESP
   secures the packet with the tunnel mode.

                       +--------------------------+
                       |        IP Header         |
                       +--------------------------+
                       |        UDP Header        |
                       +--------------------------+
                       |       Application        |
                       |       Data               |
                       +--------------------------+

                Figure 2: Example: non protected IP Packet

                       +--------------------------+
                       |        IP Header         |
                       +--------------------------+---
                       |        ESP Header        | ^
                    ---+--------------------------+ |
                    ^  |           IV             | |
                    |  +--------------------------+ |
                    |  |        UDP Header        | | Integrity
                    |  +--------------------------+ | Protection
        Encryption  |  |        Application       | |
                    |  |           Data           | |
                    |  +--------------------------+ |
                    v  |        ESP Trailer       | v
                   --- +--------------------------+---
                       |         ICV              |
                       +--------------------------+

             Figure 3: Example: IPsec/ESP with transport mode





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                       +--------------------------+
                       |     Tunnel IP Header     |
                       +--------------------------+---
                       |        ESP Header        | ^
                    ---+--------------------------+ |
                    ^  |           IV             | |
                    |  +--------------------------+ |
                    |  |        IP Header         | | Integrity
        Encryption  |  +--------------------------+ | Protection
                    |  |        UDP Header        | |
                    |  +--------------------------+ |
                    |  |  Encrypted  Application  | |
                    |  |          Data            | |
                    |  +--------------------------+ |
                    v  |        ESP Trailer       | v
                    ---+--------------------------+---
                       |         ICV              |
                       +--------------------------+

                 Figure 4: Ex: IPsec/ESP with tunnel mode

   This document does not consider the tunnel mode and only the
   transport mode.  DTLS is usually used to secure application data.
   Among other differences, IPsec/ESP with transport mode differs from
   DTLS on the following aspects: 1) The Security Header is placed
   before the transport header, as a result 2) the transport header is
   encrypted.  Then 3) IPsec/ESP is an extension of IP which makes the
   whole packet described in Figure 3 and Figure 4 an IP packet with an
   empty IP payload.  One consequence is that the packet has to respect
   the bit alignment required for IP headers, that is 32 bit alignment
   for IPv4 and 64 bit alignment for IPv6.  This is why the ESP Trailer
   presents some Padding.

   Figure 3 and Figure 4 mentions the IV which is necessary for
   encryption and decryption.  The IV is usually not part of the IPsec/
   ESP protocol, but is defined by the encryption protocol used by
   IPsec/ESP.  Each encryption protocol defines the size of its IV.  It
   is mentioned in the figures in order to clarify the way we compute
   the overhead.

   For NAT traversal, IPsec has defined a UDP encapsulation in
   [RFC3948].  UDP encapsulation of the IPsec/ESP packet with transport
   mode is illustrated in Figure 5.








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                       +--------------------------+
                       |        IP Header         |
                       +--------------------------+
                       |     UDP-Encapsulation    |
                       +--------------------------+---
                       |        ESP Header        | ^
                    ---+--------------------------+ |
                    ^  |           IV             | |
                    |  +--------------------------+ |
                    |  |        UDP Header        | | Integrity
                    |  +--------------------------+ | Protection
        Encryption  |  |       Application        | |
                    |  |       Data               | |
                    |  +--------------------------+ |
                    v  |        ESP Trailer       | v
                   --- +--------------------------+---
                       |         ICV              |
                       +--------------------------+

        Figure 5: Ex: UDP Encapsulation of IPsec/ESP Transport mode

   As illustrated in Figure 5, using IPsec/ESP with UDP encapsulation
   achieves our goal: A UDP packet carries a encrypted payload.  In
   Figure 5, the encrypted payload is the concatenation of the IV, the
   UDP header, the application data and the ESP Trailer.

   The overhead of such a packet is the ESP Header (8 bytes), the IV (8
   bytes for AES-CCM mode [RFC4309]), an extra UDP header (8 bytes), the
   ESP Trailer (2 bytes and padding bytes.  Padding bytes are between 0
   and 8 for 64 bit alignment in IPv6 and between 0 and 4 bytes for
   IPv4.  As a result, the average is 6 bytes for IPv6 and 4 bytes for
   IPv4).  This leads to a 30 bytes overhead for IPv6 and 28 byte
   overhead for IPv4.

   If this approach is to be pursued, it is probably worthwhile to
   reduce this overhead

   The remaining sections describe ways to do that.

3.  UDP-Encapsulation Header

   [RFC3948] specifies that ports of the UDP-Encapsulation Header MUST
   be the one used during the IKEv2 negotiation.  In addition IKEv2 is
   listening for UDP encapsulation on port 4500.  As a result, the port
   of the responder is always set to 4500 for any ESP packet.

   The use of a fix port in 4500 for IKEv2 is a standard port that
   specifies, IKEv2 packets are expected to be UDP encapsulated.  The



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   reason to keep these ports in the ESP UDP encapsulated communication,
   is that 1) IKEv2 has set a channel between the peers through a NAT --
   note that each peer may have a different set of (port source, port
   destination). 2) IKEv2 is used to set up the IPsec/ESP communication
   on each peer by setting the various IPsec database.  Since IKEv2 is
   aware of a through-NAT-reachable channel, IKEv2 can proceed to UDP
   encapsulation setting on each hosts.

   Port fixing is not required in applications other than the UDP
   encapsulation or if IKEv2 is not used to setup the IPsec/ESP
   communication.

4.  Removing Transport Header

   The Transport Header is used to identify the application with ports,
   once IPsec has decrypted an incoming packet.  For sending packets,
   the ports in the transport header can be used as Traffic Selectors to
   identify the right Securicy Policy.

   Removing the Transport Header implies that none of the ports or
   transport protocol can be used as selectors.  IPsec [RFC4301] does
   not prevent that, and only the IP addresses will be considered, and
   thus all applications that do not use ports as selectors between the
   two peers will be protected with the same SA.  Note that IPsec SPD is
   an ordered database.  This means that if an application between the
   two peers with ports specified as Traffic Selectors needs a specific
   Security Association, this is still possible.  The policy has simply
   to be placed before the policy using only IP addresses.

5.  Additional Compression

   With the current standard [RFC3948], [RFC4301], no additional
   compression can be completed, which leaves an overhead of 22 bytes
   for IPv4 and 20 bytes for IPv4.

   Protocols like 6LowPAN [I-D.raza-6lowpan-ipsec], ROHC [RFC3095],
   [RFC5225] can compress the ESP Header up to zero bytes.  The ESP
   Header contains a Security Policy Index (SPI) of 4 bytes and a
   Sequence Number (SN) of 4 bytes.  The SPI may be completely
   compressed if the UDP decapsulation decompressor is able to derive
   the SPI from UDP ports.  Both SPI and SN are necessary to perform
   authentication and integrity check.

   Compression of the ESP Trailer cannot be currently performed.
   However, ongoing work [I-D.mglt-ipsecme-diet-esp] makes possible the
   compression of all fields of the ESP Trailer.





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   Compression of IV is not currently permitted with IPsec, and this
   field MUST be included in each IP packet.  However, some ongoing work
   [I-D.mglt-ipsecme-diet-esp-iv-generation].

   Finally, compression of the transport header may also be performed
   using [I-D.mglt-ipsecme-diet-esp-payload-compression].  The advanatge
   of compressing it over removing it is that compression enables the
   use of ports as Traffic Selectors without carrying the transport
   header.  Note that this is done under conditions.

6.  IANA Considerations

   There are no IANA consideration for this document.

7.  Security Considerations

   The security considerations of IPsec and Diet-ESP (if used) apply.

8.  References

8.1.  Normative References

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

   [RFC3095]  Bormann, C., Burmeister, C., Degermark, M., Fukushima, H.,
              Hannu, H., Jonsson, L-E., 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.

   [RFC3948]  Huttunen, A., Swander, B., Volpe, V., DiBurro, L., and M.
              Stenberg, "UDP Encapsulation of IPsec ESP Packets", RFC
              3948, January 2005.

   [RFC4301]  Kent, S. and K. Seo, "Security Architecture for the
              Internet Protocol", RFC 4301, December 2005.

   [RFC4303]  Kent, S., "IP Encapsulating Security Payload (ESP)", RFC
              4303, December 2005.

   [RFC4309]  Housley, R., "Using Advanced Encryption Standard (AES) CCM
              Mode with IPsec Encapsulating Security Payload (ESP)", RFC
              4309, December 2005.






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   [RFC5225]  Pelletier, G. and K. Sandlund, "RObust Header Compression
              Version 2 (ROHCv2): Profiles for RTP, UDP, IP, ESP and
              UDP-Lite", RFC 5225, April 2008.

8.2.  Informational References

   [I-D.keoh-dice-multicast-security]
              Keoh, S., Kumar, S., Garcia-Morchon, O., Dijk, E., and A.
              Rahman, "DTLS-based Multicast Security in Constrained
              Environments", draft-keoh-dice-multicast-security-08 (work
              in progress), July 2014.

   [I-D.mglt-ipsecme-diet-esp]
              Migault, D. and T. Guggemos, "Diet-ESP: a flexible and
              compressed format for IPsec/ESP", draft-mglt-ipsecme-diet-
              esp-01 (work in progress), July 2014.

   [I-D.mglt-ipsecme-diet-esp-iv-generation]
              Migault, D. and T. Guggemos, "Diet-ESP: Generating
              compressed IV and SN", draft-mglt-ipsecme-diet-esp-iv-
              generation-00 (work in progress), July 2014.

   [I-D.mglt-ipsecme-diet-esp-payload-compression]
              Migault, D. and T. Guggemos, "Diet-IPsec: ESP Payload
              Compression of IPv6 / UDP / TCP / UDP-Lite", draft-mglt-
              ipsecme-diet-esp-payload-compression-00 (work in
              progress), July 2014.

   [I-D.raza-6lowpan-ipsec]
              Raza, S., Duquennoy, S., and G. Selander, "Compression of
              IPsec AH and ESP Headers for Constrained Environments",
              draft-raza-6lowpan-ipsec-01 (work in progress), September
              2013.

Authors' Addresses

   Daniel Migault
   Orange
   38 rue du General Leclerc
   92794 Issy-les-Moulineaux Cedex 9
   France

   Phone: +33 1 45 29 60 52
   Email: daniel.migault@orange.com







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   Carsten Bormann
   Universitaet Bremen TZI
   Postfach 330440
   D-28359 Bremen
   Germany

   Phone: +49-421-218-63921
   Email: cabo@tzi.org











































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