[Search] [txt|pdf|bibtex] [Tracker] [WG] [Email] [Nits]

Versions: 00 01 02 03 04 rfc2649                                        
LDAP Extensions Working Group                      Bruce Greenblatt
Internet Draft                                          Pat Richard
Expires in six months

                Signed Directory Operations Using S/MIME

Status of this Memo

     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.

     Internet-Drafts are draft documents valid for a maximum of six
months.  Internet-Drafts may be updated, replaced, or made obsolete by
other documents at any time.  It is not appropriate to use  Internet-
Drafts as reference material or to cite them other than as a "working
draft" or "work in progress".

     To view the entire list of current Internet-Drafts, please check
the "1id-abstracts.txt" listing contained in the Internet-Drafts Shadow
Directories on ftp.is.co.za (Africa), ftp.nordu.net (Northern Europe),
ftp.nis.garr.it (Southern Europe), munnari.oz.au (Pacific Rim),
ftp.ietf.org (US East Coast), or ftp.isi.edu (US West Coast).

     Distribution of this document is unlimited.


     This document defines an LDAP v3 based mechanism for signing direc-
tory operations in order to create a secure journal of changes that have
been made to each directory entry.  Both client and server based signa-
tures are supported.  An object class for subsequent retrieval are
'journal entries' is also defined.  This document specifies LDAP v3 con-
trols that enable this functionality.  It also defines an LDAP v3 schema
that allows for subsequent browsing of the journal information.

Greenblatt and Richard                                          [Page 1]

Internet Draft                                                  May 1998

1.  Mechanism

     Signed directory operations is a straightforward application of
S/MIME technology that also leverages the extensible framework that is
provided by LDAP version 3.  LDAP version 3 is defined in [4], and
S/MIME is defined in [2].  The security used in S/MIME is based in the
definitions in [1].  The basic idea is that the submitter of an LDAP
operation that changes the directory information includes an LDAP ver-
sion 3 control that includes either a signature of the operation, or a
request that the LDAP server sign the operation on the behalf of the
LDAP client.  The result of the operation (in addition to the change of
the directory information), is additional information that is attached
to directory objects, that includes the audit trail of signed opera-
tions.  The LDAP control is (OID = 1.2.840.113549.6.0.0):

     SignedOperation ::= CHOICE {
     SignbyServer [0] BOOLEAN
     SignatureIncluded [1] OCTET STRING }

     If the SignatureIncluded CHOICE is used, then the OCTET string is
just an S/MIME message of the multipart/signed variety, that is composed
of a single piece, that is the signature of the directory operation.
Multipart/signed MIME objects are defined in [3].  If the SignbyServer
CHOICE us used, then the LDAP server creates the signature on behalf of
the client, using its own identity and not the identity of the client,
in order to produce the audit trail entry.  In either case the success-
ful result of processing the control is the creation of  additional
information in the directory entry that is being modified or created.

     No control is defined for the server to return in the LDAPResult as
defined in [4].  The LDAP server MAY attempt to parse and verify the
signature included in the SignedOperation control, but is not required
to.  If the LDAP server is unable to verify the signature and wishes to
return an error then the error code unwillingToPerform(53) should be
returned, and the entire LDAP operation fails.  In this situation, an
appropriate message (e.g. "Unable to verify signature") MUST be included
in the errorMessage of the LDAPResult.  The Control MAY be marked CRITI-
CAL, and if it is CRITICAL then if the LDAP Server performs the LDAP
operation, then must include the signature in the signedAuditTrail

     The schema definition for the signedAuditTrail information is:

Greenblatt and Richard                                          [Page 2]

Internet Draft                                                  May 1998

     ( 1.2.840.113549.6.1.0
     NAME 'signedAuditTrail'
     SUP top
     MUST (

     The format of the Changes attribute is:

     ( 1.2.840.113549.6.2.0
     NAME 'Changes'
     DESC 'a set of changes applied to an entry'
     SYNTAX 'Binary' )

     The actual format of the Changes attribute is:

     Change ::= SEQUENCE {
     SequenceNumber [0] INTEGER (0 .. maxInt),
     SignedOperation [1] OCTET STRING }

     The SignedOperation attribute is a multipart/signed S/MIME  mes-
sage.  Part 1 of the message is the directory operation, and part 2 is
the signature.  Sequence number 0 (if present) always indicates the
starting point directory object as represented by the definitions in "A
MIME Content-Type for Directory Information", as defined in [5].  Subse-
quent sequence numbers indicate the sequence of changes that have been
made to this directory object.  Note that the sequence of the changes
can be verified due to the fact that the signed directory object will
have a timestamp as part of the signature object, and that the sequence
numbering as part of the change attribute should be considered to be an
unverified aid to the LDAP client.

2.  Signed Results Mechanism

     A control is also defined that allows the LDAP v3 client to request
that the server sign the results that it returns.  It is intended that
this control is primarily used in concert with the LDAPSearch operation.
This control MAY be marked as CRITICAL.  If it is marked as CRITICAL and
the LDAP Server supports this operation, then all search results MUST be
returned with a signature as attached in the SignedResult control if it
is willing to sign results for this user.  If the server supports this
control but does not wish to sign the results for this user then the

Greenblatt and Richard                                          [Page 3]

Internet Draft                                                  May 1998

error code unwillingToPerform(53) should be returned, and the LDAP
search will have failed.  In this situation, an appropriate message
(e.g. "Unwilling to sign results for you!") MUST be included in the
errorMessage of the LDAPResult.  If the LDAPSigType has the value FALSE
then the client is requesting that the server not sign this operation.
This may be done in situations where servers are configured to always
sign their operations.

     The LDAP control to include in the LDAP request is (OID =

     DemandSignedResult ::= { signatureSpan     LDAPSigType }


     In response to a DemandSignedResult control, the LDAP v3 server
will return a SignedResult control in addition to the normal result as
defined by the operation (assuming that the server understands the con-
trol, and is willing to perform it).  The SignedResult control MUST not
be marked CRITICAL.  LDAP v3 servers MAY be configured to sign all of
their operations.  In this situation the server always returns a Signe-
dResult control, unless instructed otherwise by the DemandSignedResult
Control.  The signature field below includes the signature of the enitre
LDAPResult formatted as an S/MIME pkcs-7/signature object, as defined in
[2].  The LDAP control in the LDAP response is (OID =

     SignedResult ::= CHOICE {
     signature     OCTET STRING }

3.  Notes

     The base OIDs are:

     rsadsiLdap ::= {1 2 840 113549 6}
     rsadsiLdapControls ::=  {1 2 840 113549 6 0}
     rsadsiLdapObjectClasses ::= {1 2 840 113549 6 1}
     rsadsiLdapAttributes ::= {1 2 840 113549 6 2}

     If any of the controls in this specification are supported by an
LDAP v3 server then that server MUST make available its certificate in
the userCertificate attribute of its rootDSE object.  The UserCertifi-
cate attribute is defined in [6].

Greenblatt and Richard                                          [Page 4]

Internet Draft                                                  May 1998

4.  References

     [1] RFC 2315 PKCS 7: Cryptographic Message Syntax Version 1-5. B.
Kaliski. March 1998.

     [2] RFC 2311 S/MIME Version 2 Message Specification. S. Dusse, P.
Hoffman, B. Ramsdell, L. Lundblade, L. Repka. March 1998.

     [3] RFC 1847 Security Multiparts for MIME: Multipart/Signed and
Multipart/Encrypted.  J. Galvin, S. Murphy, S. Crocker & N. Freed. Octo-
ber 1995.

     [4] RFC 2251 Lightweight Directory Access Protocol (v3). M. Wahl,
T. Howes, S. Kille. December 1997.

     [5] Internet Draft, work in progress, "A MIME Content-Type for
Directory Information", Tim Howes, Mark Smith, Frank Dawson Jr.,

     [6] RFC 2256 A Summary of the X.500(96) User Schema for use with
LDAPv3. M. Wahl. December 1997.

5.  Author's Addresses

     Bruce Greenblatt
     RSA Data Security
     100 Marine Parkway, Suite 500
     Redwood City, CA 94065
     Email: bgreenblatt@rsa.com
     Phone: +1-650-595-1282 x569

     Pat Richard
     Xcert Software, Inc.
     Suite 1001 - 701 W. Georgia
     Vancouver, BC
     CANADA V6G 1C9
     Email: patr@xcert.com

Greenblatt and Richard                                          [Page 5]

Internet Draft                                                  May 1998

                           Table of Contents

1. Audit Trail Mechanism . . . . . . . . . . . . . . . . . . . . . .   2
2. Signed Results Mechanism  . . . . . . . . . . . . . . . . . . . .   3
3. Notes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .   4
4. References  . . . . . . . . . . . . . . . . . . . . . . . . . . .   5
5. Author's Address  . . . . . . . . . . . . . . . . . . . . . . . .   5

Greenblatt and Richard                                          [Page 6]