Internet Draft C. Francis PKIX Working Group WetStone Technologies, Inc. May 2002 D. Pinkas Expires: November Bull Attribute Certificate Policies Extension Status of this memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. 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. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Abstract This document describes a certificate extension to explicitly state the attribute certificate policies that apply to the attributes contained in the certificate containing that extension. It also defines two certificate extensions that may be used to indicate the location of the public or private repositories where the certificate is being stored. Conventions 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]. 1. Introduction A Public Key Certificate (PKC) binds a specific public key to the identity of the certificate subject. When issuing a PKC, a Certificate Authority (CA) can perform various levels of verification with regard to this identity. A CA makes its verification procedures, as well as other operational rules it abides by, "visible" through a certificate policy, which may be referenced by a certificate policies extension in the PKC. Francis, Pinkas Page 1 Internet-Draft Attribute Certificate Policies Extension June 2002 Attributes may be inserted either in Attribute Certificates (ACs) in the attributes field [RFC-3281] or in Public Key Certificates (PKCs) in the subjectDirectoryAttribute extension [RFC-3280]. When issuing a PKC that contains a subjectDirectoryAttribute extension, a Certificate Authority (CA) can perform various levels of initial and subsequent verifications with regard to these attributes. The procedure for handling the attributes may be part of the Certification Policy (CP) or alternatively may be specified separately in an Attribute Certificate Policy (ACP). When issuing an AC, an Attribute Authority (AA) can perform various levels of initial and subsequent verifications with regard to the attributes that are contained in that certificate. These verification procedures, as well as other operational rules the attribute certification authority abides by, can be made "visible" through an attribute certificate policies extension, which may be included in the PKC or the AC as an extension. The purpose of this document is to define such an extension, but not the attribute certificate policies themselves. 2. AC Policy Extension Semantics An Attribute Certificate Policy (ACP) is a named set of rules that indicates the applicability of the attributes contained in a certificate to a particular community and/or class of application with common security requirements; or which indicates generic rules for registering, verifying, delivering and revoking the attributes contained in a particular Attribute Certificate. It should thus be noticed that an AA does not necessarily support only one single policy. However, for each AC that is delivered it SHALL make sure that the policy applies to all the attributes that are contained in it. The Attribute Certificate Policy is independent from the intended use of the AC, usually authorization or non-repudiation. An Attribute Certificate Policy may be used by a certificate user to decide whether or not to trust the attributes contained in a certificate for a particular purpose. When a certificate contains an AC policies extension, the extension MAY, at the option of the certificate issuer, be either critical or non-critical. The extension MAY contain optional qualifiers. The AC Policies extension MAY be included in an attribute certificate or in a public-key certificate. Like all X.509 certificate extensions, the AC policies extension is defined using ASN.1 [X.208-88, X.209-88]. The AC policies extension is identified by id-pe-acPolicies. id-pe-acPolicies OBJECT IDENTIFIER ::= { id-pe <> } Francis, Pinkas Page 2 Internet-Draft Attribute Certificate Policies Extension June 2002 The AC policies extension includes a list of AC policies recognized by the issuing authority that apply to the attributes included in the certificate, together with optional qualifier information pertaining to these AC policies. AC Policies and AC policy qualifier types may be defined by any organization with a need. Object identifiers used to identify AC Policies and AC Policy qualifier types are assigned in accordance with [ITU-T Rec. X660 | ISO/IEC 9834-1]. The presence of this extension in an attribute certificate indicates the AC policies for which the attribute certificate is valid. The presence of this extension in a public-key certificate indicates the AC policies for which the attributes included in that certificate are valid. An application that recognizes this extension and its content SHALL process the extension regardless of the value of the criticality flag. If the extension is both flagged non-critical and is not recognized, then the application MAY ignore it. If the extension is flagged critical or is recognized, it indicates that the attributes contained in the certificate SHALL only be used for the purpose, and in accordance with the rules implied by one of the indicated AC policies. The rules of a particular policy MAY require the certificate-using system to process the qualifier value in a particular way. If the extension is marked critical or is recognized, certificate users MUST use the list of AC policies and associated qualifiers to determine whether it is appropriate to use the attributes contained in that certificate for a particular transaction. 2.1 AC Policy Extension Syntax The AC Policy syntax mirrors the certificate policies extension used for public key certificates defined in [X.509] and profiled in [RFC-3280]. The syntax for the AC Policy extension is: acPolicies EXTENSION ::= { SYNTAX acPoliciesSyntax IDENTIFIED BY id-pe-acPolicies} acPoliciesSyntax ::= SEQUENCE SIZE (1..MAX) OF PolicyInformation PolicyInformation ::= SEQUENCE { policyIdentifier acPolicyId, policyQualifiers SEQUENCE SIZE (1..MAX) OF PolicyQualifierInfo OPTIONAL} Francis, Pinkas Page 3 Internet-Draft Attribute Certificate Policies Extension June 2002 acPolicyId ::= OBJECT IDENTIFIER PolicyQualifierInfo ::= SEQUENCE { policyQualifierId PolicyQualifierId, qualifier ANY DEFINED BY policyQualifierId } To promote interoperability, this document RECOMMENDS that policy information terms consist of only an OID. 2.2 Attribute Certificate Policies The scope of this document is not the definition of the detailed content of Attribute Certificate policies themselves, therefore specific policies are not detailed in this document. 2.3. Policy Qualifiers 2.3.1. Generic Policy Qualifiers This specification defines two generic policy qualifier types for use by certificate policy writers and certificate issuers. The qualifier types are the CPS Pointer and User Notice qualifiers. The CPS Pointer qualifier contains a pointer to a Certification Practice Statement (CPS) published by the AA or the CA. The pointer is in the form of a URI. User notice is intended for display to a relying party when a certificate is used. The application software SHOULD display all user notices in all certificates of the certification path used, except that if a notice is duplicated only one copy need be displayed. To prevent such duplication, this qualifier SHOULD only be present in end-entity certificates. These policies Qualifiers are defined in RFC 3280. -- policyQualifierIds for Internet policy qualifiers id-qt OBJECT IDENTIFIER ::= { id-pkix 2 } id-qt-cps OBJECT IDENTIFIER ::= { id-qt 1 } id-qt-unotice OBJECT IDENTIFIER ::= { id-qt 2 } 2.3.2. Specific Policy Qualifiers Specific Policy qualifiers MAY be used to convey important differences between specific policies to relying parties. This specification defines three specific policy qualifier types for use by certificate policy writers and certificate issuers. Francis, Pinkas Page 4 Internet-Draft Attribute Certificate Policies Extension June 2002 2.3.2.1. Initial Verification Qualifier Attributes inserted in a certificate are verified at the time of the initial registration of the attribute for a given end-entity. Unless a specific revocation request is received and granted by the AA or the CA, attributes will continue to be certified for the period indicated by the certificateÆs validity period. For an AC, since the validity period of an AC can be much shorter than the period during which the asserted attribute(s) are granted to the holder, unless specific additional information is included, it cannot be known when attributes were initially verified. The initial verification qualifier is only applicable for ACs and indicates when the attributes contained in the AC have been initially verified. id-qt-iniVer OBJECT IDENTIFIER ::= { id-qt W } IniVer ::= GeneralizedTime Note: When an AC contains several attributes with different initial verification dates, this field contains the oldest verification date. 2.3.2.2. Regular Verification Qualifier AAs or CAs may choose to regularly verify some attributes so that relying parties may be more confident about their association with the end-entity. This information may be made available directly in a certificate through the Regular Verification qualifier. The Regular Verification Qualifier indicates that the attributes contained in the AC are regularly verified and includes the verification time period. id-qt-regVer OBJECT IDENTIFIER ::= { id-qt X } RegVer ::= CHOICE { days [0] INTEGER , months [1] INTEGER , years [2] INTEGER } 2.3.2.3. Repository Qualifiers When a relying party receives a certificate, it may be useful to avoid forwarding the certificate itself and pass only a reference to the certificate, together with a location where the certificate is stored. In some cases the AA or CA may be responsible for publication of the certificates it issues. When this is the case, a relying party can take advantage of the storage performed by or on behalf of the issuing authority. Francis, Pinkas Page 5 Internet-Draft Attribute Certificate Policies Extension June 2002 In order to allow a relying party to know that such a storage is available, two specific qualifiers may be used: the Public Repository and /or Private Repository qualifiers. The Public Repository Qualifier indicates that the AC is published in a public repository. id-qt-pubRep OBJECT IDENTIFIER ::= { id-qt Y } PubRep ::= NULL The Private Repository Qualifier indicates that the AC is published in a private repository reserved for some community of users. id-qt-prvRep OBJECT IDENTIFIER ::= { id-qt Z } PrvRep ::= NULL 3. Repository location extensions The locations of published certificates may be available in the CPS from the CA or AA. They may also be explicitly included in the certificate by including a repository location extension. The OIDs for these extensions are members of the id-ce arc, which is defined by the following: id-ce OBJECT IDENTIFIER ::= { joint-iso-ccitt(2) ds(5) 29 } 3.1. Public repository location extension The Public repository location Extension indicates the location of the repositories where the certificate is publicly available. This extension MAY be supported by CAs, AAs and/or applications, and it MUST be non-critical. id-ce-pubRepLoc OBJECT IDENTIFIER ::= { id-ce X } PubRepLoc ::= SEQUENCE OF GeneralName -- only uniformResourceIdentifier is allowed 3.2. Private repository location extension The Private repository location Extension indicates the location of the repositories where the certificate is only available for a community of users. This extension MAY be supported by CAs, AAs and/or applications, and it MUST be non-critical. id-ce-prvRepLoc OBJECT IDENTIFIER ::= { id-ce Y } Francis, Pinkas Page 6 Internet-Draft Attribute Certificate Policies Extension June 2002 PrvRepLoc ::= SEQUENCE OF GeneralName -- only uniformResourceIdentifier is allowed 4. Security Considerations The Attribute Certification Policy defined in this document applies for all the attributes that are included in one AC or one PKC. AAs or CAs shall make sure that the policy applies to all the attributes which are included in the certificates they issue. For AAs, attributes may be dynamically grouped in several ACs. It should be observed that since the management of some attributes may be different, different policies and/or different policy qualifiers may be used by the same AA. 5. References ITU-T Rec. X660 | ITU-T Recommendation Rec X.660 (1992) ISO/IEC 9834-1 | ISO/IEC 9834-1: 1993, Information technology - Open Systems Interconnection Procedures for the operation of OSI Registration Authorities: General procedures. RFC-3280 Certificate and Certificate Revocation List (CRL) Profile. R. Housley, W.Polk, W.Ford, and D. Solo. April 2002. RFC-3281 An Internet Attribute Certificate Profile for Authorization. S. Farrell S. and R. Housley. April 2002. X.208-88 CCITT. Recommendation X.208: Specification of Abstract Syntax Notation One (ASN.1). 1988. X.209-88 CCITT. Recommendation X.209: Specification of Basic Encoding Rules for Abstract Syntax Notation One (ASN.1). 1988. X.509 ITU-T Recommendation X.509 (2000): Information Technology û Open Systems Interconnections - The Directory: Public-key and Attribute Frameworks, March 2000 Author's Addresses Christopher S. Francis WetStone Technologies, Inc. 17755 US Highway 19 North, Suite 150 Clearwater, Florida 33764 Email: Chris.Francis@wetstonetech.com Francis, Pinkas Page 7 Internet-Draft Attribute Certificate Policies Extension June 2002 Denis Pinkas Bull 68, Route de Versailles 78434 Louveciennes CEDEX FRANCE Email: Denis.Pinkas@bull.net Full Copyright Statement Copyright (C) The Internet Society 2002. All Rights Reserved. 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