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Network Performance Measurement for IPsec
draft-bi-ippm-ipsec-00

The information below is for an old version of the document.
Document Type This is an older version of an Internet-Draft whose latest revision is Replaced
Authors Emily Bi , Kostas Pentikousis , Yang Cui
Last updated 2012-10-14
Replaced by draft-ietf-ippm-ipsec, draft-ietf-ippm-ipsec, draft-ietf-ippm-ipsec, RFC 7717
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draft-bi-ippm-ipsec-00
IPPM                                                           Emily. Bi
Internet-Draft                                            K. Pentikousis
Intended status: Standards Track                               Yang. Cui
Expires: April 18, 2013                              Huawei Technologies
                                                        October 15, 2012

                 Network Performance Measurement for IPsec
                        draft-bi-ippm-ipsec-00.txt

Abstract

   IPsec is a mature technology with several interoperable
   implementations.  Indeed, the use of IPsec tunnels is increasingly
   gaining popularity in several deployment scenarios, not the least in
   what used to be solely areas of traditional telecommunication
   protocols.  Wider deployment calls for mechanisms and methods that
   enable tunnel end-users, as well as operators, to measure one-way and
   two-way network performance.  Unfortunately, however, standard IP
   performance measurement mechanisms cannot be readily used with IPsec.
   This document makes the case for employing IPsec to protect O/TWAMP
   and proposes a method which combines IKEv2 and O/TWAMP as defined in
   RFC 4656 and RFC 5357, respectively.  This specification aims, on the
   one hand, to ensure that O/TWAMP can be secured well, while on the
   other hand, it extends the applicability of O/TWAMP to networks that
   have already deployed IPsec.

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 April 18, 2013.

Copyright Notice

   Copyright (c) 2012 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

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Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  4
   2.  Terminology used in this document  . . . . . . . . . . . . . .  4
   3.  Motivation . . . . . . . . . . . . . . . . . . . . . . . . . .  4
       3.1 O/TWAMP-Control Security . . . . . . . . . . . . . . . . .  5
       3.2 O/TWAMP-Test Security  . . . . . . . . . . . . . . . . . .  6
       3.3 O/TWAMP Security Root  . . . . . . . . . . . . . . . . . .  7
       3.4 Why IPPM cannot be employed over IPsec?  . . . . . . . . .  7
   4.  O/TWAMP over IPsec . . . . . . . . . . . . . . . . . . . . . .  8
   5.  Others . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
   6. Security Considerations  . . . . . . . . . . . . . . . . . . .  12
   7. IANA Considerations  . . . . . . . . . . . . . . . . . . . . .  12
   8. Acknowledgments  . . . . . . . . . . . . . . . . . . . . . . .  12
   Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 12

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1.  Introduction

   The active measurement protocols OWAMP [RFC4656] and TWAMP [RFC5357]
   can be used to measure network performance parameters, such as
   latency, bandwidth, and packet loss by sending probe packets and
   monitoring their experience in the network.  In order to guarantee
   the accuracy of network measurement results, security aspects must be
   considered, otherwise, attacks may occur and authenticity may be
   violated.  For example, a man in the middle may modify packet
   timestamps if no protection is provided.

   Cryptographic security mechanisms, such as IPsec, have been
   considered during the early stage of working towards the definition
   of the two protocols mentioned above.  However, due to several
   reasons, it was preferred to avoid tying the development and
   deployment of O/TWAMP protocols to such security mechanisms.  In
   practice, for many networks, the issues listed in [RFC4656], Sec. 6.6
   with respect to IPSec are still valid.  However, we expect that in
   the near future IPsec will be deployed in many more hosts and
   networks than today.  Therefore, in this document we attempt to make
   the case that for networks where wide deployment of IPsec and other
   security mechanisms is mandatory for a variety of reasons, there are
   increasingly more use cases in which IPsec and O/TWAMP protocols are
   needed simultaneously.  In other words, we argue that it is now time
   to specify how O/TWAMP can be used in a network environment where
   IPsec is already deployed.  In such an environment, measuring IP
   performance over IPsec tunnels with O/TWAMP is an important tool for
   operators.

2.  Terminology used in this document

   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].

3.  Motivation

   Let us first consider why the reasons listed [RFC4656] Sec. 6.6 may
   not apply in many cases.  First, the argument made is that partial
   authentication in OWAMP authentication mode is not possible with
   IPsec.  IPsec indeed cannot authenticate only a part of a packet.
   However, in an environment where IPsec is already deployed and
   actively used, partial authentication of O/TWAMP contradicts the
   operational reasons dictating the use of IPsec.  At the same time,
   this limits the applicability and use of O/TWAMP in networks using
   IPsec.

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   The second argument made is the need to keep separate deployment
   paths between OWAMP and IPsec.  In several currently deployed types
   of networks, IPsec is widely used to protect the data and signaling
   planes.  For example, in mobile telecommunication networks, the
   deployment rate of IPsec exceeds 95% with respect to the LTE serving
   network.  In older technology cellular networks, such as UMTS and
   GSM, this percentage is lower, but still quite significant.
   Additionally, there is a great number of IPSec-based VPN applications
   which are widely used in business applications to provide end-to-end,
   or host-to-host security.  At the same time, lots of standardized
   protocols make use of IPsec/IKE, including MIPv4/v6, HIP, SCTP, BGP,
   NAT and SIP, just to name a few.

   Third, with respect to the support of IPsec in lightweight embedded
   devices, nowadays, a large number of limited-resource and low-cost
   devices, such as Ethernet switches, DSL modems, and other such
   devices come with support for IPsec "out of the box".  Therefore
   concerns about implementation, although likely valid a decade ago,
   are not well founded today.

   Fourth, everyday use of IPsec applications by field technicians, on
   the one hand, and by good understanding of the IPsec API by many
   programmers, on the other, should not be anymore a reason for
   concern.  On the contrary: By now, IPsec open source code is
   available for anyone who wants to use it.  Therefore, although IPsec
   does need a certain level of expertise to deal with it, in practice,
   most competent technical personnel and programmers have no problems
   using it on a daily basis.

   O/TWAMP actually consists of two inter-related protocols: O/TWAMP-
   Control and O/TWAMP-Test.  O/TWAMP-Control is used to initiate,
   start, and stop test sessions and to fetch their results, whereas
   O/TWAMP-Test is used to exchange test packets between two measurement
   nodes.  In the following subsections we consider security for each
   one separately and then make the case for using them over IPsec.

   3.1 O/TWAMP-Control Security

   O/TWAMP uses a simple cryptographic protocol which relies on AES-CBC
   for confidentiality and on HMAC-SHA1 truncated to 128 bits for
   message authentication.  Three modes of operation are supported:
   unauthenticated, authenticated, and encrypted.  The authenticated and
   encrypted modes require that endpoints possess a shared secret,
   typically a passphrase.  The secret key is derived from the
   passphrase using a password-based key derivation function PBKDF2
   (PKCS#5) [RFC2898].

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   In the unauthenticated mode, the security parameters are unused.  In
   authenticated and encrypted mode, the security parameters will be
   negotiated during the control connection establishment.  Before the
   client can send commands to a server, it has to establish a
   connection to the server.  Then, the client opens a TCP connection to
   the server on the well-known port number 861.  The server responds
   with a server greeting, which contains the Challenge, mode, Salt and
   Count.  If the client wants to establish the connection, it responds
   with a Set-Up-Response message, wherein the KeyID, Token and Client
   IV are included.  The Token is the concatenation of a 16-octet
   challenge, a 16-octet AES Session-key used for encryption, and a 32-
   octet HMAC-SHA1 Session-key used for authentication.  The token
   itself is encrypted using AES in Cipher Block Chaining (AES-CBC).

   Encryption is performed using a key derived from the shared secret
   associated with KeyID.  In authenticated and encrypted modes, all
   further communications are encrypted using the AES Session-key and
   authenticated with HMAC Session-key.  The client encrypts everything
   it sends through the just-established O/TWAMP-Control connection
   using stream encryption with Client-IV as the IV.  Correspondingly,
   the server encrypts its side of the connection using Server-IV as the
   IV.  The IVs themselves are transmitted in cleartext.  Encryption
   starts with the block immediately following the block containing the
   IV.

   The AES Session-key and HMAC Session-key are generated randomly by
   the client.  The HMAC Session-key is communicated along with the AES
   Session-key during O/TWAMP-Control connection setup.  The HMAC
   Session-key is derived independently of the AES Session-key.

   3.2 O/TWAMP-Test Security

   The O/TWAMP-Test protocol runs over UDP, using sender and receiver IP
   and port numbers negotiated during the Request-Session exchange.  As
   with O/TWAMP-Control, O/TWAMP-Test has three modes: unauthenticated,
   authenticated, and encrypted.  All O/TWAMP-Test sessions that are
   spawned by an O/TWAMP-Control session inherit its mode.

   The O/TWAMP-Test packet layout is the same in authenticated and
   encrypted modes.  The encryption and authentication operations are,
   however, different.  Similarly with the respective O/TWAMP-Control
   session, each O/TWAMP-Test session has two keys: an AES Session-key
   and an HMAC Session-key.  However, there is a difference in how the
   keys are obtained.  In the case of O/TWAMP-Control, the keys are
   generated by the client and communicated (as part of the Token)
   during connection setup as part of Set-Up-Response message.  In the
   case of O/TWAMP-Test, the keys are derived from the O/TWAMP-Control

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   keys and the session identifier (SID).  The O/TWAMP-Test AES Session-
   key is obtained from the O/TWAMP-Control AES Session-key.  The
   O/TWAMP-Control AES Session-key is encrypted using AES, with the 16-
   octet session identifier (SID) as the key.  The result is the
   O/TWAMP-Test AES Session-key used to encrypt and decrypt the packets
   of the particular O/TWAMP-Test session.  The O/TWAMP-Test HMAC
   Session-key is obtained from the O/TWAMP-Control HMAC Session-key.
   The O/TWAMP-Control HMAC Session-key is encrypted using AES, with the
   16-octet session identifier (SID) as the key.  The result is the
   O/TWAMP-Test HMAC Session-key used in authenticating the packets of
   the particular O/TWAMP-Test session.

   3.3 O/TWAMP Security Root

   As discussed above, the AES Session-key and HMAC Session-key used in
   the O/TWAMP-Test protocol are derived from the AES Session-key and
   HMAC Session-key which are used in O/TWAMP-Control protocol.  The AES
   Session-key and HMAC Session-key used in the O/TWAMP-Control protocol
   are generated randomly by the client, and encrypted with the shared
   secret associated with KeyID.  Therefore, the security root is the
   shared secret key.

   3.4 Why IPPM cannot be employed over IPsec?

   IPsec provides confidentiality and data integrity to IP datagrams.
   Three protocols are provided: Authentication Header (AH),
   Encapsulating Security Payload (ESP) and Internet Key Exchange (IKE
   v1/v2).  Only integrity protection can be provided with AH.  Both
   integrity and encryption can be provided with ESP.  The IKE Protocol
   is used for dynamical key negotiation and automatic key management.

   When the sender and receiver implement O/TWAMP over IPsec, the sender
   and the receiver will agree on a shared key during the establishment
   of IPsec, and all IP packets sent by the sender are protected with
   IPsec.  If the AH protocol is used, IP packets are transmitted in
   plaintext.  The authentication part covers the entire packet.  So all
   test information, such as UDP port number, and the test results will
   be visible to any attacker, which can intercept these test packets,
   and introduce errors or forge packets that may be injected during the
   transmission.  In order to avoid this attack, the receiver must
   validate the integrity of these packets with the negotiated secret
   key.  If ESP is used, IP packets are encrypted, and hence no other
   than the receiver can use the IPsec secret key and decrypt the IP
   packet, and then it can obtain the test data to assess the IP network
   performance based on the measurements.  So both the sender and
   receiver must support IPsec to generate the security secret key of

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   IPsec.

   In the current implementation of O/TWAMP, after the test packets are
   received by the receiver, it cannot execute active measurement over
   IPsec.  That is because the receiver knows only the shared secret key
   but not the IPsec key, while the test packets are protected with
   IPsec key ultimately.  Therefore, it needs to be considered how to
   measure IP network performance over an IPsec tunnel with O/TWAMP.
   Without this functionality, the use of OWAMP and TWAMP over IPsec is
   hindered.

   Of course, backward compatibility should be considered, as well.
   That is, the intrinsic security method based on shared key as
   specified in the O/TWAMP standards can also fit the other platforms.
   There should be no impact on the current security mechanisms defined
   in O/TWAMP for other use cases.  This document describes a possible
   solution to this problem which takes advantage of the secret key
   derived by IPsec, to provision the key needed in RFC 4656 and RFC
   5357.

4.  O/TWAMP over IPsec

   A security method based on a shared secret key has been defined in
   O/TWAMP [RFC 4656][RFC 5357].  In this section, in order to employ
   O/TWAMP over IPsec, a method of binding IPPM and IKEv2 is described,
   for those both the sender and receiver supporting the IPsec
   protocols.  The shared key used in the security of O/TWAMP is derived
   from IPsec [RFC5996].  If the AH protocol is used, the IP packets are
   transmitted in plaintext.  All of O/TWAMP is integrity-protected by
   IPsec.  Even if the peers choose unauthenticated mode, IPsec
   integrity protection is provided to O/TWAMP.  In authenticated and
   encrypted modes, the shared secret can be derived from IKE SA or
   IPsec SA.  If the shared secret key is derived from IKE SA, SKEYSEED
   must be generated firstly.  SKEYSEED and its derivatives are computed
   as the way in [RFC5996], where prf is a pseudorandom function:

   SKEYSEED = prf(Ni | Nr, g^ir)

   Ni and Nr are the nonces, negotiated during initial exchange. g^ir is
   the shared secret from the ephemeral Diffie-Hellman exchange and is
   represented as a string of octets.  SKEYSEED can be used as the share
   secret key directly then the share key is equal to SKEYSEED.
   Alternatively, the shared secret key can be generated as follows:
   Shared secret key=PRF{ SKEYSEED, Session ID}, wherein the session ID
   is the SID agreed during the O/TWAMP-Test protocol.

   If the shared secret key is derived from IPsec SA, the shared secret

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   key can be equal to KEYMAT, wherein KEYMAT = prf+(SK_d, Ni | Nr) and
   the term "prf+" describes a function that outputs a pseudorandom
   stream based on the inputs to a prf [RFC5996]; or the shared secret
   key can be generated as follows: Shared secret key=PRF{ KEYMAT,
   Session ID} , wherein the session ID is the SID agreed during the
   O/TWAMP-Test protocol.

   There are some cases for rekeying IKE SA and IPsec SA, after which
   the corresponding key of SA is updated.  Generally ESP and AH SAs
   always exist in pairs, with one SA in each direction.  If the SA is
   deleted, the key generated from IKE SA or IPsec SA should also be
   updated.

   As discussed above, a binding association between the key generated
   from IPsec and the shared secret key needs to be considered.  SA can
   be identified by SPI and protocol uniquely for a sender and a
   receiver.  So these parameters should be agreed during the O/TWAMP
   protocol.  When the sender and receiver execute O/TWAMP protocol to
   negotiate integrity key, the IPsec protocol and SPI should be
   checked.  Only if two parameters are matched with the information of
   IPsec, should the O/TWAMP connection be established.  As illustrated
   in Figure 1, the SPI and protocol type are included in the server
   greeting of the O/TWAMP-Control protocol.  After the client receives
   the greeting, it closes the connection if it receives a greeting with
   an erroneous SPI and protocol value.  Otherwise, the client responds
   with the following Set-Up-Response message and generate shared secret
   key.The message exchange flow is described as Figure 1:

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   +-------------------+                  +-------------------+
   |                   |                  |                   |
   |       Client      |                  |        Server     |
   |                   |                  |                   |
   +-------------------+                  +-------------------+
             |                                      |
             |            TCP  Connection           |
             |<------------------------------------>|
             |                                      |
             |             Greeting message         |
             |<-------------------------------------|
             |                                      |
             |             Set-Up-Response          |
             |------------------------------------->|
             |                                      |
             |                                      |
             |              Server-Start            |
             |<-------------------------------------|
             |                                      |

            Figure 1.  The procedure of O/TWAMP-Control

   The format of server greeting is illustrated in Figure 2.

   The unused 12 octets are used to carry the new parameter: protocol
   and SPIs.

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        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
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           protocol                            |
       |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           SPIi                                |
       |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                           SPIr                                |
       |+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-++-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                            Modes                              |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                     Challenge (16 octets)                     |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                        Salt (16 octets)                       |
       |                                                               |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                        Count (4 octets)                       |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
       |                                                               |
       |                        MBZ (12 octets)                        |
       |                                                               |
       +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+

                 Figure 2.  The format of server greeting

   In ESP, when the IP packets are encrypted, no other than the receiver
   achieves the IPsec key and decrypted the IP packet.  It gains the
   test data to process measurement IP performance.  IPsec protocol
   between the sender and receiver provides additional security.  Even
   if the peers choose unauthenticated mode, IPsec encryption and
   integrity protection is provided to O/TWAMP.  If the sender and
   receiver also want to use authenticated or encrypted mode, the shared
   secret can be also derived from IKE SA or IPsec SA.  The method of
   key generation and binding association is the same as AH protocol
   mode.

   Besides, there is encryption-only configuration in ESP, though not
   recommended for its insecurity.  Since it does not produce integrity
   key in this case, either encryption-only ESP should be prohibited for
   O/TWAMP, or a decryption failure should be distinguished due to
   possible integrity attack.

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5.  Others

   To be added

6.  Security Considerations

   As the shared secret key is derived from IPsec, the key derived
   algorithm strength and limitations are as per [RFC5996].  The
   strength of a key derived from a Diffie-Hellman exchange using any of
   the groups defined here depends on the inherent strength of the
   group, the size of the exponent used, and the entropy provided by the
   random number generator used.  The strength of all keys and
   implementation vulnerabilities, particularly DoS attacks are as
   defined in [RFC5996].

7.  IANA Considerations

   There may be IANA consideration for taking additional value for these
   options.  The values of the protocol field needed to be assigned from
   the numbering space.

8.  Acknowledgments

   who contributed actively to this document.

Authors' Addresses

   Emily Bi
   Huawei Technologies
   Huawei Building, Xinxi Road No.3
   Haidian District, Beijing  100085
   P. R. China

   Phone: +86-10-60611962
   Email: bixiaoyu@huawei.com

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   Kostas Pentikousis
   Huawei Technologies
   Carnotstr. 4
   10587 Berlin
   Germany

   Email: k.pentikousis@huawei.com

   Yang Cui
   Huawei Technologies
   Huawei Building, Xinxi Road No.3
   Haidian District, Beijing  100085
   P. R. China

   Phone: +86-10-60611962
   Email: cuiyang@huawei.com

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