Network Working Group                                            M. MyersRequest for Comments: 2797                                       VeriSignCategory: Standards Track                                          X. Liu                                                                    Cisco                                                                J. Schaad                                                                Microsoft                                                             J. Weinstein                                                               April 2000                Certificate Management Messages over CMSStatus of this Memo   This document specifies an Internet standards track protocol for the   Internet community, and requests discussion and suggestions for   improvements.  Please refer to the current edition of the "Internet   Official Protocol Standards" (STD 1) for the standardization state   and status of this protocol.  Distribution of this memo is unlimited.Copyright Notice   Copyright (C) The Internet Society (2000).  All Rights Reserved.Abstract   This document defines a Certificate Management protocol using CMS   (CMC).  This protocol addresses two immediate needs within the   Internet PKI community:   1. The need for an interface to public key certification products and      services based on [CMS] and [PKCS10], and   2. The need in [SMIMEV3] for a certificate enrollment protocol for      DSA-signed certificates with Diffie-Hellman public keys.   A small number of additional services are defined to supplement the   core certificate request service.   Throughout this specification the term CMS is used to refer to both   [CMS] and [PKCS7].  For both signedData and envelopedData, CMS is a   superset of the PKCS7. In general, the use of PKCS7 in this document   is aligned to the Cryptographic Message Syntax [CMS] that provides a   superset of the PKCS7 syntax. The term CMC refers to this   specification.   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 [RFC 2119].Myers, et al.               Standards Track                     [Page 1]RFC 2797        Certificate Management Messages over CMS      April 20001.  Protocol Requirements   -  The protocol is to be based as much as possible on the existing      CMS, PKCS#10 and CRMF specifications.   -  The protocol must support the current industry practice of a      PKCS#10 request followed by a PKCS#7 response as a subset of the      protocol.   -  The protocol needs to easily support the multi-key enrollment      protocols required by S/MIME and other groups.   -  The protocol must supply a way of doing all operations in a      single-round trip.  When this is not possible the number of round      trips is to be minimized.   -  The protocol will be designed such that all key generation can      occur on the client.   -  The mandatory algorithms must superset the required algorithms for      S/MIME.   -  The protocol will contain POP methods. Optional provisions for      multiple-round trip POP will be made if necessary.   -  The protocol will support deferred and pending responses to      certificate request for cases where external procedures are      required to issue a certificate.   -  The protocol needs to support arbitrary chains of local      registration authorities as intermediaries between certificate      requesters and issuers.2.  Protocol Overview   An enrollment transaction in this specification is generally composed   of a single round trip of messages.  In the simplest case an   enrollment request is sent from the client to the server and an   enrollment response is then returned from the server to the client.   In some more complicated cases, such as delayed certificate issuance   and polling for responses, more than one round trip is required.   This specification supports two different request messages and two   different response messages.   Public key certification requests can be based on either the PKCS10   or CRMF object.  The two different request messages are (a) the bare   PKCS10 (in the event that no other services are needed), and (b) the   PKCS10 or CRMF message wrapped in a CMS encapsulation as part of a   PKIData object.   Public key certification responses are based on the CMS signedData   object.  The response may be either (a) a degenerate CMS signedData   object (in the event no other services are needed), or (b) a   ResponseBody object wrapped in a CMS signedData object.Myers, et al.               Standards Track                     [Page 2]RFC 2797        Certificate Management Messages over CMS      April 2000   No special services are provided for doing either renewal (new   certificates with the same key) or re-keying (new certificates on new   keys) of clients.  Instead a renewal/re-key message looks the same as   any enrollment message, with the identity proof being supplied by   existing certificates from the CA.   A provision exists for Local Registration Authorities (LRAs) to   participate in the protocol by taking client enrollment messages,   wrapping them in a second layer of enrollment message with additional   requirements or statements from the LRA and then passing this new   expanded request on to the Certification Authority.   This specification makes no assumptions about the underlying   transport mechanism.  The use of CMS is not meant to imply an email-   based transport.   Optional services available through this specification are   transaction management, replay detection (through nonces), deferred   certificate issuance, certificate revocation requests and   certificate/CRL retrieval.2.1  Terminology   There are several different terms, abbreviations and acronyms used in   this document that we define here for convenience and consistency of   usage:   "End-Entity" (EE) refers to the entity that owns a key pair and for      whom a certificate is issued.   "LRA" or "RA" refers to a (Local) Registration Authority.  A      registration authority acts as an intermediary between an End-      Entity and a Certification Authority.  Multiple RAs can exist      between the End-Entity and the Certification Authority.   "CA" refers to a Certification Authority.  A Certification Authority      is the entity that performs the actual issuance of a certificate.   "Client" refers to an entity that creates a PKI request.  In this      document both RAs and End-Entities can be clients.   "Server" refers to the entities that process PKI requests and create      PKI responses.  CAs and RAs can be servers in this document.   "PKCS#10" refers the Public Key Cryptography Standard #10.  This is      one of a set of standards defined by RSA Laboratories in the      1980s.  PKCS#10 defines a Certificate Request Message syntax.   "CRMF" refers to the Certificate Request Message Format RFC [CRMF].      We are using certificate request message format defined in this      document as part of our management protocol.   "CMS" refers to the Cryptographic Message Syntax RFC [CMS].  This      document provides for basic cryptographic services including      encryption and signing with and without key management.Myers, et al.               Standards Track                     [Page 3]RFC 2797        Certificate Management Messages over CMS      April 2000   "POP" is an acronym for "Proof of Possession".  POP refers to a value      that can be used to prove that the private key corresponding to a      public key is in the possession and can be used by an end-entity.   "Transport wrapper" refers to the outermost CMS wrapping layer.2.2  Protocol Flow Charts   Figure 1 shows the Simple Enrollment Request and Response messages.   The contents of these messages are detailed in Sections 4.1 and 4.3   below.    Simple PKI Request                      Simple PKI Response    -------------------------               --------------------------    +----------+                            +------------------+    | PKCS #10 |                            | CMS "certs-only" |    +----------+--------------+             |     message      |    |                         |             +------------------+------+    | Certificate Request     |             |                         |    |                         |             | CMS Signed Data,        |    | Subject Name            |             |   no signerInfo         |    | Subject Public Key Info |             |                         |    |   (K_PUB)               |             | signedData contains one |    | Attributes              |             | or more certificates in |    |                         |             | the "certificates"      |    +-----------+-------------+             | portion of the          |                | signed with |             | signedData.             |                | matching    |             |                         |                | K_PRIV      |             | encapsulatedContentInfo |                +-------------+             | is empty.               |                                            |                         |                                            +--------------+----------+                                                           | unsigned |                                                           +----------+               Figure 1: Simple PKI Request and Response MessagesMyers, et al.               Standards Track                     [Page 4]RFC 2797        Certificate Management Messages over CMS      April 2000    Full PKI Request                        Full PKI Response    -----------------------                 ------------------------    +----------------+                      +----------------+    | CMS signedData |                      | CMS signedData |    |     object     |                      |     object     |    +----------------+--------+             +----------------+--------+    |                         |             |                         |    | PKIData object          |             | ResponseBody object     |    |                         |             |                         |    | Sequence of:            |             | Sequence of:            |    | <enrollment attribute>* |             | <enrollment attribute>* |    | <certification request>*|             | <CMS object>*           |    | <CMS objects>*          |             | <other message>*        |    | <other message>*        |             |                         |    |                         |             | where * == zero or more |    | where * == zero or more |             |                         |    |                         |             | All certificates issued |    | Certificate requests    |             | as part of the response |    | are CRMF or PKCS#10     |             | are included in the     |    | objects. Attributes are |             | "certificates" portion  |    | (OID, ANY defined by    |             | of the signedData.      |    | OID) pairs.             |             | Relevant CA certs and   |    |                         |             | CRLs can be included as |    +-------+-----------------+             | well.                   |            | signed (keypair |             |                         |            | used may be pre-|             +---------+---------------+            | existing or     |                       | signed by the |            | identified in   |                       | CA or an LRA  |            | the request)    |                       +---------------+            +-----------------+               Figure 2: Full PKI Request and Response Messages   Figure 2 shows the Full Enrollment Request and Response messages.   The contents of these messages are detailed in Sections 4.2 and 4.4   below.3.  Protocol Elements   This section covers each of the different elements that may be used   to construct enrollment request and enrollment response messages.   Section 4 will cover how to build the enrollment request and response   messages.Myers, et al.               Standards Track                     [Page 5]RFC 2797        Certificate Management Messages over CMS      April 20003.1  PKIData Object   The new content object PKIData has been defined for this protocol.   This new object is used as the body of the full PKI request message.   The new body is identified by:     id-cct-PKIData  OBJECT IDENTIFIER ::= { id-cct 2 }   The ASN.1 structure corresponding to this new content type is:   PKIData ::= SEQUENCE {         controlSequence    SEQUENCE SIZE(0..MAX) OF TaggedAttribute,         reqSequence        SEQUENCE SIZE(0..MAX) OF TaggedRequest,         cmsSequence        SEQUENCE SIZE(0..MAX) OF TaggedContentInfo,         otherMsgSequence   SEQUENCE SIZE(0..MAX) OF OtherMsg   }   -- controlSequence consists of a sequence of control attributes.  The   control attributes defined in this document are found in section 5.   As control sequences are defined by OIDs, other parties can define   additional control attributes. Unrecognized OIDs MUST result in no   part of the request being successfully processed.