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Versions: 00                                                            
Internet Engineering Task Force             R. Pereira, TimeStep Corp.
IP Security Working Group                   P. Bhattacharya, IBM Corp.
Internet Draft
Expires in six months
                                                     February 19, 1998

                       IPSec Policy Data Model

Status of this Memo

   This document is a submission to the IETF Internet Protocol
   Security (IPSECond) Working Group. Comments are solicited and
   should be addressed to the working group mailing list
   (ipsec@tis.com) or to the editor.

   This document is an Internet-Draft.  Internet Drafts are working
   documents of the Internet Engineering Task Force (IETF), its areas,
   and its working Groups. Note that other groups may also distribute
   working documents as Internet Drafts.

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   Distribution of this memo is unlimited.


   This document presents a data model for IPSec policy based on

R. Pereira, P. Bhattacharya                                   [Page 1]

Internet Draft         IPSec Policy Data Model           February, 98

Table of Contents

   1. Introduction...................................................2
     1.1. Specification of Requirements..............................2
   2. Data Model.....................................................2
     2.1. ISAKMP Model...............................................3
     2.2. IPSec Model................................................4
   3. Security Considerations........................................7
   4. References.....................................................7
   5. Editors' Addresses.............................................8

1.   Introduction

   The original intent of this document was to present a flexible,
   extensible and interoperable IPSec policy model that would be used
   by all IPSec compliant devices.  This version of this document
   represents a scaled down effort of that original goal.  This is due
   to many reasons, most notably the size of such an undertaking and
   the number of equally correct policy paradigms that IPSec can be
   molded into.

   The authors hope that this base IPSec data model will provide
   implementers sufficient information on the base IPSec negotiation
   mechanism that they can create an Enterprise policy architecture
   with the correct IPSec model.

   It is assumed that the reader is familiar with the terms and
   concepts described in the "Security Architecture for the Internet
   Protocol" [Atkinso95] and "IP Security Document Roadmap" [Thayer97]
   documents as well as all other referenced IPSec documents.

1.1. Specification of Requirements

   The keywords "MUST", "MUST NOT", "REQUIRED", "SHOULD", "SHOULD
   NOT", and "MAY" that appear in this document are to be interpreted
   as described in [Bradner97].

2.   Data Model

   To understand IPSec, the reader must realize that there really
   exists two different policy areas; one for the ISAKMP security
   association and one for the actual IPSec (ESP/AH) security
   association.  While the ISAKMP SA relies on the two negotiating
   peers, the IPSec SA will rely on the hosts actually being
   protected, which in many cases are the same as the negotiating
   peers (client to client).

R. Pereira, P. Bhattacharya                                   [Page 2]

Internet Draft         IPSec Policy Data Model           February, 98

   The current version of this document does not try to represent
   objects on the network (gateways, firewalls, routers, workstations,
   ...) and their relationship to these data models.  This work might
   be in future versions of this document, but it is foreseeable that
   most organizations will require different network security policy

   The following data models are represented in ASN.1 notation merely
   for clarity and is not intended to imply any preference for ASN.1
   based policy mechanisms however, a LDAP schema will be added to
   future versions of this document.

2.1. ISAKMP Model

   The ISAKMP SA protects the two negotiating peers while they are
   communicating with ISAKMP.

   The specification below allows for such examples as;
    '(DES MD5) or (DES SHA)'

   IsakmpDescriptor ::=
       exchange ENUMERATED {
         AggressiveMode } OPTIONAL,
       proposal SEQUENCE OF IsakmpProposal

   o The main ISAKMP object mainly includes proposals, but also
     includes which exchange to utilize.  AggressiveMode does not
     hide the identity of the negotiating peers, while MainMode does.
     Please refer to [Harkins98] for a more complete reference to
     both of these two exchange modes.

     The exchange mode MAY not be included in this object since it
     MAY instead depend on the peers.

   o The proposals are all taken as logical ORs when presented

R. Pereira, P. Bhattacharya                                   [Page 3]

Internet Draft         IPSec Policy Data Model           February, 98

   IsakmpProposal ::=
       cipher IsakmpCipherAlg,
       keylength INTEGER OPTIONAL,
       hash HashAlg,
       group INTEGER OPTIONAL,
       expiry Expiry

   o The keylength attribute is only valid when the cipher algorithm
     is CAST, RC5 or Blowfish.

   o The default for the group attribute is 1.

   HashAlg ::=

   o The hash algorithm values are specified in [Harkins98].

   IsakmpCipherAlg ::=

   o The cipher algorithm values are specified in [Harkins98].

   Expiry ::=
       seconds INTEGER OPTIONAL,
       kilobytes INTEGER OPTIONAL

2.2. IPSec Model

   The IPSec SA(s) protects the actual IP traffic between two systems.
   IPSec allows for security gateways (firewalls, routers or edge
   devices, ...) to proxy on behalf of systems behind them so that the

R. Pereira, P. Bhattacharya                                   [Page 4]

Internet Draft         IPSec Policy Data Model           February, 98

   negotiating system may not be the end-system.  Thus rules based on
   IpsecDescriptor SHOULD be referenced by the actual end-systems
   being protected. Additionally, rules MAY also be referenced by
   either edge devices proxing on their behalf.

   The specification below allows for such examples as;

     ((ESP DES) AND
       (AH (HMAC MD5) OR (HMAC SHA)))'

   IpsecDescriptor ::=
       pfs BOOLEAN,
       proposal SEQUENCE OF IpsecProposal

   o The Perfect Forward Secrecy (pfs) attribute is situated in the
     IPSec object and not in the ISAKMP object since this attribute
     is used in QuickMode (phase 2) for the initial IPSec SA and for
     subsequent rekeyed SAs.

   o The proposals are all taken as logical ORs when presented

   IpsecProposal ::=
       protectionSuite IpsecSuite

   o The protectionSuite attributes are all taken as logical ANDs
     when presented together thus allowing for multiple protocols to
     be negotiated together.

   IpsecSuite ::=
     CHOICE {
       espProtocol SEQUENCE OF EspProposal,
       ahProtocol SEQUENCE OF AhProposal,
       compProtocol SEQUENCE OF IpcompProposal

   o The IpsecSuite represents one of three possible protocol types.
     ESP allows for confidentiality and integrity/authentication, AH
     only allows for integrity/authentication and IPComp allows for

R. Pereira, P. Bhattacharya                                   [Page 5]

Internet Draft         IPSec Policy Data Model           February, 98

   EspProposal ::=
       cipher IpsecCipherAlg,
       keylength INTEGER OPTIONAL,
       keyrounds INTEGER OPTIONAL,
       integrity IntegrityAlg OPTIONAL,
       group INTEGER OPTIONAL,
       expiry Expiry OPTIONAL

   o The keylength attribute MUST only be present when the cipher
     algorithm is either CAST, RC5, or blowfish.

   o Key rounds is currently not defined for any cipher algorithm,
     but if a cipher algorithm is specified in the future that
     utilizes key rounds, then this attribute MAY be present.

   o The group attribute defaults to 1 and SHOULD only be present if
     the PFS attribute is TRUE.

   AhProposal ::=
       integrity IntegrityAlg,
       group INTEGER OPTIONAL,
       expiry Expiry OPTIONAL

   o The group attribute defaults to 1 and SHOULD only be present if
     the PFS attribute is TRUE.

   IpcompProposal ::=
       compression CompressionAlg,
       expiry Expiry OPTIONAL

   CompressionAlg ::=

   o The compression algorithm values are specified in [Piper98].

R. Pereira, P. Bhattacharya                                   [Page 6]

Internet Draft         IPSec Policy Data Model           February, 98

   IntegrityAlg ::=

   o The integrity algorithm values are specified in [Piper98].

   IpsecCipherAlg ::=

   o The cipher algorithm values are specified in [Piper98].

3.   Security Considerations

  This draft merely presents a data model of the IPSec documents.
  All security considerations within those actual specification MUST
  be considered previously to implementing a policy architecture.

4.   References

   [Atkinso95] R. Atkinson, "Security Architecture for the Internet
               Protocol", draft-ietf-ipsec-arch-sec-01

   [Bradner97] S. Bradner, "Key words for use in RFCs to indicate
               Requirement Levels", RFC2119

   [ISAKMP]    D. Maughan, M. Schertler, M. Schneider, J. Turner,
               "Internet Security Association and Key Management
               Protocol", draft-ietf-ipsec-isakmp-08

R. Pereira, P. Bhattacharya                                   [Page 7]

Internet Draft         IPSec Policy Data Model           February, 98

   [Harkins98] D. Harkins, "The Resolution of ISAKMP and Oakley",

   [Droms97]   R. Droms, "Dynamic Host Configuration Protocol",

   [Radius97]  C. Rigney, A. Rubens, W. Simpson, S. Willens, "Remote
               Authentication Dial In User Service (RADIUS)", RFC2138

   [Ldap97]    M. Wahl, T. Howes, S. Kille, "Lightweight Directory
               Access Protocol (v3)", RFC2251

   [Keromy98]  A. Keromytis, N. Provos, "The Use of HMAC-RIPEMD-160-96
               within ESP and AH", draft-ietf-ipsec-auth-hmac-ripemd-

   [Piper98]   D. Piper, "The Internet IP Security Domain of
               Interpretation for ISAKMP", draft-ietf-ipsec-ipsec-doi-

5.   Editors' Addresses

     Roy Pereira
     TimeStep Corporation
     +1 (613) 599-3610 x 4808

     Partha Bhattacharya
     IBM Corporation
     +1 (919) 863-7981

   The IPSec working group can be contacted via the IPSec working
   group's mailing list (ipsec@tis.com) or through its chairs:

     Robert Moskowitz
     International Computer Security Association

     Theodore Y. Ts'o
     Massachusetts Institute of Technology

R. Pereira, P. Bhattacharya                                   [Page 8]