PKIX Working Group Sharon Boeyen (Entrust) draft-ietf-pkix-ipki2opp-03.txt Tim Howes (Netscape) Expires in 6 months Patrick Richard (Xcert) September 1997 Internet Public Key Infrastructure Operational Protocols - LDAP <draft-ietf-pkix-ipki2opp-03.txt> 1. Status of this Memo This document is an Internet-Draft. Internet-Drafts are working docu- ments of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working docu- ments 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." To learn the current status of any Internet-Draft, please check the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow Directories on ftp.is.co.za (Africa), nic.nordu.net (Europe), munnari.oz.au (Pacific Rim), ds.internic.net (US East Coast), or ftp.isi.edu (US West Coast). 2. Abstract The protocol described in this document is designed to satisfy some of the operational requirements within the Internet Public Key Infrastruc- ture (IPKI). Specifically, this document addresses requirements to pro- vide access to Public Key Infrastructure (PKI) repositories for the pur- poses of retrieving PKI information and managing that same information. The mechanism described in this document is based on the Lightweight Directory Access Protocol (LDAP) version 2, defined in RFC 1777, and defines a profile of that protocol for use within the IPKI. Additional mechanisms addressing PKIX operational requirements are specified in separate documents. The key words "MUST", "REQUIRED", "SHOULD", "RECOMMENDED", and "MAY" in this document are to be interpreted as described in RFC 2119. Please send comments on this document to the ietf-pkix@tandem.com mail list. Boeyen, Howes & Richard [Page 1]
INTERNET DRAFT September 1997 3. Introduction This specification is part of a multi-part standard for development of a Public Key Infrastructure (PKI) for the Internet. This specification addresses requirements to provide retrieval of X.509 PKI information, including certificates and CRLs from a repository. This specification also addresses requirements to add, delete and modify PKI information in a repository. A profile based on the LDAP version 2 protocol is provided to satisfy these requirements. 4. Model The PKI components, as defined in PKIX Part 1, which are involved in PKIX operational protocol interactions include: - End Entities - Certification Authorities (CA) - Repository End entities and CAs using LDAPv2, retrieve PKI information from the repository using a subset of the LDAPv2 protocol. CAs populate the repository with PKI information using a subset of the LDAPv2 protocol. 5. Lightweight Directory Access Protocol (LDAP) The following sections examine the retrieval of PKI information from a repository and management of PKI information in a repository. A profile of the LDAPv2 protocol is defined for providing these services. Section 6 satisfies the requirement to retrieve PKI information (a cer- tificate, CRL, or other information of interest) from an entry in the repository, where the retrieving entity (either an end entity or a CA) has knowledge of the name of the entry. This is termed "repository read". Section 7 satisfies the same requirement as 6 for the situation where the name of the entry is not known, but some other related information which may optionally be used as a filter against candidate entries in the repository, is known. This is termed "repository search". Section 8 satisfies the requirement of CAs to add, delete and modify PKI information information (a certificate, CRL, or other information of interest)in the repository. This is termed "repository modify". The subset of LDAPv2 needed to support each of these functions is described below. Note that the repository search service is a superset Boeyen, Howes & Richard [Page 2]
INTERNET DRAFT September 1997 of the repository read service in terms of the LDAPv2 functionality needed. Note that all tags are implicit by default in the ASN.1 definitions that follow. 6. LDAP Repository Read To retrieve information from an entry corresponding to the subject or issuer name of a certificate, requires a subset of the following three LDAP operations: BindRequest (and BindResponse) SearchRequest (and SearchResponse) UnbindRequest The subset of each REQUIRED operation is given below. 6.1. Bind 6.1.1. Bind Request The full LDAP v2 Bind Request is defined in RFC 1777. An application providing a LDAP repository read service MUST implement the following subset of this operation: BindRequest ::= [APPLICATION 0] SEQUENCE { version INTEGER (2), name LDAPDN, -- MUST accept NULL LDAPDN simpleauth [0] OCTET STRING -- MUST accept NULL simple } An application providing a LDAP repository read service MAY implement other aspects of the BindRequest as well. Different services may have different security requirements. Some ser- vices may allow anonymous search, others may require authentication. Those services allowing anonymous search may choose only to allow search based on certain criteria and not others. A LDAP repository read service SHOULD implement some level of anonymous search access. A LDAP repository read service MAY implement authenti- cated search access. Boeyen, Howes & Richard [Page 3]
INTERNET DRAFT September 1997 6.1.2. Bind Response The full LDAPv2 BindResponse is described in RFC 1777. An application providing a LDAP repository read service MUST implement this entire protocol element, though only the following error codes may be returned from a Bind operation: success (0), operationsError (1), protocolError (2), authMethodNotSupported (7), noSuchObject (32), invalidDNSyntax (34), inappropriateAuthentication (48), invalidCredentials (49), busy (51), unavailable (52), unwillingToPerform (53), other (80) 6.2. Search 6.2.1. Search Request The full LDAPv2 SearchRequest is defined in RFC 1777. An application providing a LDAP repository read service MUST implement the following subset of the SearchRequest. SearchRequest ::= [APPLICATION 3] SEQUENCE { baseObject LDAPDN, scope ENUMERATED { baseObject (0), }, derefAliases ENUMERATED { neverDerefAliases (0), }, sizeLimit INTEGER (0), timeLimit INTEGER (0), attrsOnly BOOLEAN, -- FALSE only filter Filter, attributes SEQUENCE OF AttributeType } Filter ::= CHOICE { Boeyen, Howes & Richard [Page 4]
INTERNET DRAFT September 1997 present [7] AttributeType, -- "objectclass" only } This subset of the LDAPv2 SearchRequest allows the LDAPv2 "read" opera- tion: a base object search with a filter testing for the existence of the objectClass attribute. An application providing a LDAP repository read service MAY implement other aspects of the SearchRequest as well. 6.2.2. The full LDAPv2 SearchResponse is defined in RFC 1777. An application providing a LDAP repository read service over LDAPv2 MUST implement the full SearchResponse. 6.3. Unbind The full LDAPv2 UnbindRequest is defined in RFC 1777. An application providing a LDAP repository read service MUST implement the full UnbindRequest. 7. LDAP Repository Search To search ,using arbitrary criteria, for an entry in a repository con- taining a certificate, CRL, or other information of interest, requires a subset of the following three LDAP operations: BindRequest (and BindResponse) SearchRequest (and SearchResponse) UnbindRequest The subset of each operation REQUIRED is given below. 7.1. Bind The BindRequest and BindResponse subsets needed are the same as those described in Section 6.1. The full LDAP v2 Bind Request is defined in RFC 1777. 7.2. Search 7.2.1. Search Request The full LDAPv2 SearchRequest is defined in RFC 1777. Boeyen, Howes & Richard [Page 5]
INTERNET DRAFT September 1997 An application providing a LDAP repository search service MUST implement the following subset of the SearchRequest protocol unit. SearchRequest ::= [APPLICATION 3] SEQUENCE { baseObject LDAPDN, scope ENUMERATED { baseObject (0), singleLevel (1), wholeSubtree (2) }, derefAliases ENUMERATED { neverDerefAliases (0), }, sizeLimit INTEGER (0 .. maxInt), timeLimit INTEGER (0 .. maxInt), attrsOnly BOOLEAN, -- FALSE only filter Filter, attributes SEQUENCE OF AttributeType } All aspects of the SearchRequest MUST be supported, except for the fol- lowing: - Only the neverDerefAliases value of derefAliases needs to be supported - Only the FALSE value for attrsOnly needs to be supported This subset provides a more general search capability. It is a superset of the SearchRequest subset defined in Section 6.2.1. The elements added to this service are: - singleLevel and wholeSubtree scope needs to be supported - sizeLimit is included - timeLimit is included - Enhanced filter capability An application providing a LDAP repository search service MAY implement other aspects of the SearchRequest as well. 7.2.2. Search Response The full LDAPv2 SearchResponse is defined in RFC 1777. Boeyen, Howes & Richard [Page 6]
INTERNET DRAFT September 1997 An application providing a LDAP repository search service over LDAPv2 MUST implement the full SearchResponse. 7.3. Unbind An application providing a LDAP repository search service MUST implement the full UnbindRequest. 8. LDAP Repository Modify To add, delete and modify PKI information in a repository requires a subset of the following LDAP operations: BindRequest (and BindResponse) ModifyRequest (and ModifyResponse) AddRequest (and AddResponse) DelRequest (and DelResponse UnbindRequest The subset of each operation REQUIRED is given below. 8.1. Bind The full LDAP v2 Bind Request is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the following subset of this operation: BindRequest ::= [APPLICATION 0] SEQUENCE { version INTEGER (2), name LDAPDN, simpleauth [0] OCTET STRING } A LDAP repository modify service MUST implement authenticated access. The BindResponse subsets needed are the same as those described in Sec- tion 6.1.2. 8.2. Modify 8.2.1. Modify Request The full LDAPv2 ModifyRequest is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the following subset of the ModifyRequest protocol unit. Boeyen, Howes & Richard [Page 7]
INTERNET DRAFT September 1997 ModifyRequest ::= [APPLICATION 6] SEQUENCE { object LDAPDN, modification SEQUENCE OF SEQUENCE { operation ENUMERATED { add (0), delete (1) }, modification SEQUENCE { type AttributeType, values SET OF AttributeValue } } } All aspects of the ModifyRequest MUST be supported, except for the fol- lowing: - Only the add and delete values of operation need to be supported 8.2.2. Modify Response The full LDAPv2 ModifyResponse is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the full ModifyResponse. 8.3. Add 8.3.1. Add Request The full LDAPv2 AddRequest is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the full AddRequest. 8.3.2. Add Response The full LDAPv2 AddResponse is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the full AddResponse. 8.4. Delete Boeyen, Howes & Richard [Page 8]
INTERNET DRAFT September 1997 8.4.1. Delete Request The full LDAPv2 DelRequest is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the full DelRequest. 8.4.2. Delete Response The full LDAPv2 DelResponse is defined in RFC 1777. An application providing a LDAP repository modify service MUST implement the full DelResponse. 8.5. Unbind An application providing a LDAP repository modify service MUST implement the full UnbindRequest. 9. Non-standard attribute value encodings When conveyed in LDAP requests and results, attributes defined in X.500 are to be encoded using string representations defined in RFC 1778, The String Representation of Standard Attribute Syntaxes. These string encodings were based on the attribute definitions from X.500(1988). Thus, the string representations of the PKI information elements are for version 1 certificates and version 1 revocation lists. Since this specification uses version 3 certificates and version 2 revocation lists, as defined in X.509(1997), the RFC 1778 string encoding of these attributes is inappropriate. For this reason, these attributes MUST be encoded using a syntax similar to the syntax "Undefined" from section 2.1 of RFC 1778: values of these attributes are encoded as if they were values of type "OCTET STRING", with the string value of the encoding being the DER-encoding of the value itself. For example, when writing a userCertificate to the repo- sitory, the CA generates a DER-encoding of the certificate and uses that encoding as the value of the userCertificate attribute in the LDAP Modify request.This encoding style is consistent with the encoding scheme proposed for LDAPv3, which is now being defined within the IETF. 10. Transport An application providing a LDAP repository read service, LDAP repository search service, or LDAP repository modify service MUST support LDAPv2 transport over TCP, as defined in Section 3.1 of RFC 1777. An application providing a LDAP repository read service, LDAP repository Boeyen, Howes & Richard [Page 9]
INTERNET DRAFT September 1997 search service, or LDAP repository modify service MAY support LDAPv2 transport over other reliable transports as well. 11. Security Considerations Since the elements of information which are key to the PKI service (cer- tificates and CRLs) are both digitally signed pieces of information, no additional integrity service is REQUIRED. As neither information ele- ment need be kept secret and anonymous access to such information, for retrieval purposes is generally acceptable, no privacy service is REQUIRED. As CAs may have access to information elements in the reposi- tory which anonymous users will not, it is RECOMMENDED that even though anonymous access is provided to end entities, CAs should bind to the repository with a minimum of simple authentication. For the LDAP repository modify service, profiled in section 8, there are some specific security considerations with respect to access control. The CA MUST have access control permissions allowing it to: For CA entries: - add, modify and delete all PKI attributes for its own directory entry; - add, modify and delete all values of these attributes. For CRL distribution point entries (if used): - create, modify and delete entries of object class cRLDistributionPoint immediately subordinate to its own entry; - add, modify and delete all attributes, and all values of these attributes for these entries. For subscriber (end-entity) entries: - add, modify and delete the attribute userCertificate and all values of that attribute, issued by this CA to/from these entries. The CA is the ONLY entity with these permissions. An application providing LDAP repository read, LDAP repository search, or LDAP repository modify service as defined in this specification is not REQUIRED to implement any additional security features other than those described herein, however an implementation MAY do so. 12. References [1] Lightweight Directory Access Protocol. Y. Yeong, T. Howes, S. Kille, RFC 1777, March 1995. Boeyen, Howes & Richard [Page 10]
INTERNET DRAFT September 1997 [2] The String Representation of Standard Attribute Syntaxes. T. Howes, S. Kille, W. Yeong, C. Robbins, RFC 1778, March 1995. [3] Key Words for use in RFCs to Indicate Requirement Levels, S. Bradner, RFC 2119, March 1997. 13. Author's Address Sharon Boeyen Entrust Technologies Limited 750 Heron Road Ottawa, Ontario Canada K1V 1A7 boeyen@entrust.com Tim Howes Netscape Communications Corp. 501 E. Middlefield Rd. Mountain View, CA 94043 USA howes@netscape.com Patrick Richard Xcert Software Inc. Suite 1001, 701 W. Georgia Street P.O. Box 10145 Pacific Centre Vancouver, B.C. Canada V7Y 1C6 patr@xcert.com Boeyen, Howes & Richard [Page 11]
