Internet Draft                                      R. Harrison, Editor
Document: draft-ietf-ldapbis-authmeth-00.txt               Novell, Inc.
Intended Category: Draft Standard                     February 20, 2001
Obsoletes: RFC 2829


                   Authentication Methods for LDAPv3

Status of this Memo

   This document is an Internet-Draft and is in full conformance with
   all provisions of Section 10 of RFC2026.

   This document is intended to be, after appropriate review and
   revision, submitted to the RFC Editor as a Standard Track document.
   Distribution of this memo is unlimited.  Technical discussion of
   this document will take place on the IETF LDAP Extension Working
   Group mailing list <ietf-ldapbis@OpenLDAP.org>.  Please send
   editorial comments directly to the author
   <roger_harrison@novell.com>.

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Abstract

   This document specifies particular combinations of security
   mechanisms that are required and recommended in LDAPv3 [1]
   implementations.

1. Introduction

   LDAPv3 is a powerful access protocol for directories.
   It offers means of searching, fetching and manipulating directory
   content, and ways to access a rich set of security functions.

   In order to function for the best of the Internet, it is vital that
   these security functions be interoperable; therefore there has to be
   a minimum subset of security functions that is common to all
   implementations that claim LDAPv3 conformance.

   Basic threats to an LDAP directory service include:


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   (1) Unauthorized access to data via data-fetching operations,

   (2) Unauthorized access to reusable client authentication
       information by monitoring others' access,

   (3) Unauthorized access to data by monitoring others' access,

   (4) Unauthorized modification of data,

   (5) Unauthorized modification of configuration,

   (6) Unauthorized or excessive use of resources (denial of service),
       and

   (7) Spoofing of directory: Tricking a client into believing that
       information came from the directory when in fact it did not,
       either by modifying data in transit or misdirecting the client's
       connection.

   Threats (1), (4), (5) and (6) are due to hostile clients. Threats
   (2), (3) and (7) are due to hostile agents on the path between
   client and server, or posing as a server.

   The LDAP protocol suite can be protected with the following security
   mechanisms:

   (1) Client authentication by means of the SASL [2] mechanism set,
       possibly backed by the TLS credentials exchange mechanism,

   (2) Client authorization by means of access control based on the
       requestor's authenticated identity,

   (3) Data integrity protection by means of the TLS protocol or data-
       integrity SASL mechanisms,

   (4) Protection against snooping by means of the TLS protocol or
       data-encrypting SASL mechanisms,

   (5) Resource limitation by means of administrative limits on service
       controls, and

   (6) Server authentication by means of the TLS protocol or SASL
       mechanism.

   At the moment, imposition of access controls is done by means
   outside the scope of the LDAP protocol.

   In this document, the term "user" represents any application which
   is an LDAP client using the directory to retrieve or store
   information.





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   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 [3].

2. Example deployment scenarios

   The following scenarios are typical for LDAP directories on the
   Internet, and have different security requirements. (In the
   following, "sensitive" means data that will cause real damage to the
   owner if revealed; there may be data that is protected but not
   sensitive). This is not intended to be a comprehensive list, other
   scenarios are possible, especially on physically protected networks.

   (1) A read-only directory, containing no sensitive data, accessible
       to "anyone", and TCP connection hijacking or IP spoofing is not
       a problem. This directory requires no security functions except
       administrative service limits.

   (2) A read-only directory containing no sensitive data; read access
       is granted based on identity. TCP connection hijacking is not
       currently a problem. This scenario requires a secure
       authentication function.

   (3) A read-only directory containing no sensitive data; and the
       client needs to ensure that the directory data is authenticated
       by the server and not modified while being returned from the
       server.

   (4) A read-write directory, containing no sensitive data; read
       access is available to "anyone", update access to properly
       authorized persons. TCP connection hijacking is not currently a
       problem. This scenario requires a secure authentication
       function.

   (5) A directory containing sensitive data. This scenario requires
       session confidentiality protection AND secure authentication.

3. Authentication and Authorization: Definitions and Concepts

   This section defines basic terms, concepts, and interrelationships
   regarding authentication, authorization, credentials, and identity.
   These concepts are used in describing how various security
   approaches are utilized in client authentication and authorization.

3.1. Access Control Policy

   An access control policy is a set of rules defining the protection
   of resources, generally in terms of the capabilities of persons or
   other entities accessing those resources. A common expression of an
   access control policy is an access control list. Security objects
   and mechanisms, such as those described here, enable the expression
   of access control policies and their enforcement. Access control


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   policies are typically expressed in terms of access control
   attributes as described below.

3.2. Access Control Factors

   A request, when it is being processed by a server, may be associated
   with a wide variety of security-related factors (section 4.2 of
   [1]). The server uses these factors to determine whether and how to
   process the request. These are called access control factors (ACFs).
   They might include source IP address, encryption strength, the type
   of operation being requested, time of day, etc. Some factors may be
   specific to the request itself, others may be associated with the
   connection via which the request is transmitted, others (e.g. time
   of day) may be "environmental".

   Access control policies are expressed in terms of access control
   factors. E.g., a request having ACFs i,j,k can perform operation Y
   on resource Z. The set of ACFs that a server makes available for
   such expressions is implementation-specific.

3.3. Authentication, Credentials, Identity

   Authentication credentials are the evidence supplied by one party to
   another, asserting the identity of the supplying party (e.g. a user)
   who is attempting to establish an association with the other party
   (typically a server). Authentication is the process of generating,
   transmitting, and verifying these credentials and thus the identity
   they assert. An authentication identity is the name presented in a
   credential.

   There are many forms of authentication credentials -- the form used
   depends upon the particular authentication mechanism negotiated by
   the parties. For example: X.509 certificates, Kerberos tickets,
   simple identity and password pairs. Note that an authentication
   mechanism may constrain the form of authentication identities used
   with it.

3.4. Authorization Identity

   An authorization identity is one kind of access control factor. It
   is the name of the user or other entity that requests that
   operations be performed. Access control policies are often expressed
   in terms of authorization identities; e.g., entity X can perform
   operation Y on resource Z.

   The authorization identity bound to an association is often exactly
   the same as the authentication identity presented by the client, but
   it may be different. SASL allows clients to specify an authorization
   identity distinct from the authentication identity asserted by the
   client's credentials. This permits agents such as proxy servers to
   authenticate using their own credentials, yet request the access
   privileges of the identity for which they are proxying [2]. Also,
   the form of authentication identity supplied by a service like TLS

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   may not correspond to the authorization identities used to express a
   server's access control policy, requiring a server-specific mapping
   to be done. The method by which a server composes and validates an
   authorization identity from the authentication credentials supplied
   by a client is implementation-specific.

4. Required security mechanisms

   It is clear that allowing any implementation, faced with the above
   requirements, to pick and choose among the possible alternatives is
   not a strategy that is likely to lead to interoperability. In the
   absence of mandates, clients will be written that do not support any
   security function supported by the server, or worse, support only
   mechanisms like cleartext passwords that provide clearly inadequate
   security.

   Active intermediary attacks are the most difficult for an attacker
   to perform, and for an implementation to protect against. Methods
   that protect only against hostile client and passive eavesdropping
   attacks are useful in situations where the cost of protection
   against active intermediary attacks is not justified based on the
   perceived risk of active intermediary attacks.

   Given the presence of the Directory, there is a strong desire to see
   mechanisms where identities take the form of an LDAP distinguished
   name and authentication data can be stored in the directory; this
   means that either this data is useless for faking authentication
   (like the Unix "/etc/passwd" file format used to be), or its content
   is never passed across the wire unprotected - that is, it's either
   updated outside the protocol or it is only updated in sessions well
   protected against snooping. It is also desirable to allow
   authentication methods to carry authorization identities based on
   existing forms of user identities for backwards compatibility with
   non-LDAP-based authentication services.

   Therefore, the following implementation conformance requirements are
   in place:

   (1) For a read-only, public directory, anonymous authentication,
       described in section 5, can be used.

   (2) Implementations providing password-based authenticated access
       MUST support authentication using the DIGEST-MD5 SASL mechanism
       [4], as described in section 6.2. This provides client
       authentication with protection against passive eavesdropping
       attacks, but does not provide protection against active
       intermediary attacks.

   (3) For a directory needing session protection and authentication,
       the Start TLS extended operation [5], and either the simple
       authentication choice or the SASL EXTERNAL mechanism, are to be
       used together. Implementations SHOULD support authentication
       with a password as described in section 6.2, and SHOULD support

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       authentication with a certificate as described in section 7.1.
       Together, these can provide integrity and disclosure protection
       of transmitted data, and authentication of client and server,
       including protection against active intermediary attacks.

   If TLS is negotiated, the client MUST discard all information about
   the server fetched prior to the TLS negotiation. In particular, the
   value of supportedSASLMechanisms MAY be different after TLS has been
   negotiated (specifically, the EXTERNAL mechanism or the proposed
   PLAIN mechanism are likely to only be listed after a TLS negotiation
   has been performed).

   If a SASL security layer is negotiated, the client MUST discard all
   information about the server fetched prior to SASL. In particular,
   if the client is configured to support multiple SASL mechanisms, it
   SHOULD fetch supportedSASLMechanisms both before and after the SASL
   security layer is negotiated and verify that the value has not
   changed after the SASL security layer was negotiated. This detects
   active attacks which remove supported SASL mechanisms from the
   supportedSASLMechanisms list, and allows the client to ensure that
   it is using the best mechanism supported by both client and server
   (additionally, this is a SHOULD to allow for environments where the
   supported SASL mechanisms list is provided to the client through a
   different trusted source, e.g. as part of a digitally signed
   object).

5. Anonymous Authentication

   Directory operations that modify entries or access protected
   attributes or entries generally require client authentication.
   Clients that do not intend to perform any of these operations
   typically use anonymous authentication. Servers SHOULD NOT allow
   clients with anonymous authentication to modify directory entries or
   access sensitive information in directory entries.

   LDAP implementations MUST support anonymous authentication, as
   defined in section 5.1.

   LDAP implementations MAY support anonymous authentication with TLS,
   as defined in section 5.2.

   While there MAY be access control restrictions to prevent access to
   directory entries, an LDAP server SHOULD allow an anonymously-bound
   client to retrieve the supportedSASLMechanisms attribute of the root
   DSE.

   An LDAP server MAY use other information about the client provided
   by the lower layers or external means to grant or deny access even
   to anonymously authenticated clients.

5.1. Anonymous Authentication Procedure



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   An LDAPv3 client that has not successfully completed a bind
   operation on a connection is anonymously authenticated.

   An LDAP client MAY also bind anonymously using the procedure defined
   in section 4.2 of RFC 2251.

5.2. Anonymous Authentication and TLS

   An LDAP client MAY use the Start TLS operation [5] to negotiate the
   use of TLS security [6]. If the client has not bound beforehand,
   then until the client uses the EXTERNAL SASL mechanism to negotiate
   the recognition of the client's certificate, the client is
   anonymously authenticated.

   Recommendations on TLS ciphersuites are given in section 10.

   An LDAP server which requests that clients provide their certificate
   during TLS negotiation MAY use a local security policy to determine
   whether to successfully complete TLS negotiation if the client did
   not present a certificate which could be validated.

6. Password-based authentication

6.1. Simple authentication

   The LDAP "simple" authentication choice is not suitable for
   authentication in environments where there is no network or
   transport layer confidentiality. LDAP implementations SHOULD support
   authentication with the "simple" authentication choice when the
   connection is protected against eavesdropping using TLS, as defined
   in section 6.3. LDAP implementations SHOULD NOT support
   authentication with the "simple" authentication choice unless the
   data on the connection is protected using TLS or other privacy and
   data-integrity protection.

6.2. Digest Authentication

   LDAP implementations MUST support authentication with a password
   using the DIGEST-MD5 SASL mechanism for password protection, as
   defined in section 6.1.

   An LDAP client MAY determine whether the server supports this
   mechanism by performing a search request on the root DSE, requesting
   the supportedSASLMechanisms attribute, and checking whether the
   string "DIGEST-MD5" is present as a value of this attribute.

   In the first stage of authentication, when the client is performing
   an "initial authentication" as defined in section 2.1 of [4], the
   client sends a bind request in which the version number is 3, the
   authentication choice is sasl, the sasl mechanism name is "DIGEST-
   MD5", and the credentials are absent. The client then waits for a
   response from the server to this request.


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   The server will respond with a bind response in which the resultCode
   is saslBindInProgress, and the serverSaslCreds field is present. The
   contents of this field is a string defined by "digest-challenge" in
   section 2.1.1 of [4]. The server SHOULD include a realm indication
   and MUST indicate support for UTF-8.

   The client will send a bind request with a distinct message id, in
   which the version number is 3, the authentication choice is sasl,
   the sasl mechanism name is "DIGEST-MD5", and the credentials contain
   the string defined by "digest-response" in section 2.1.2 of [4]. The
   serv-type is "ldap".

   The server will respond with a bind response in which the resultCode
   is either success, or an error indication. If the authentication is
   successful and the server does not support subsequent
   authentication, then the credentials field is absent. If the
   authentication is successful and the server supports subsequent
   authentication, then the credentials field contains the string
   defined by "response-auth" in section 2.1.3 of [4]. Support for
   subsequent authentication is OPTIONAL in clients and servers.

6.3. "simple" authentication choice under TLS encryption

   Following the negotiation of an appropriate TLS ciphersuite
   providing connection confidentiality [6], a client MAY authenticate
   to a directory that supports the simple authentication choice by
   performing a simple bind operation.

   The client will use the Start TLS operation [5] to negotiate the use
   of TLS security [6] on the connection to the LDAP server. The client
   need not have bound to the directory beforehand.

   For this authentication procedure to be successful, the client and
   server MUST negotiate a ciphersuite which contains a bulk encryption
   algorithm of appropriate strength. Recommendations on cipher suites
   are given in section 10.

   Following the successful completion of TLS negotiation, the client
   MUST send an LDAP bind request with the version number of 3, the
   name field containing a DN , and the "simple" authentication choice,
   containing a password.

   6.3.1 "simple" Authentication Choice

   DSAs that map the DN sent in the bind request to a directory entry
   with a userPassword attribute will, for each value of the
   userPassword attribute in the named user's entry, compare these for
   case-sensitive equality with the client's presented password. If
   there is a match, then the server will respond with resultCode
   success, otherwise the server will respond with resultCode
   invalidCredentials.

6.4. Other authentication choices with TLS

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   It is also possible, following the negotiation of TLS, to perform a
   SASL authentication that does not involve the exchange of plaintext
   reusable passwords. In this case the client and server need not
   negotiate a ciphersuite which provides confidentiality if the only
   service required is data integrity.

7. Certificate-based authentication

   LDAP implementations SHOULD support authentication via a client
   certificate in TLS, as defined in section 7.1.

7.1. Certificate-based authentication with TLS

   A user who has a public/private key pair in which the public key has
   been signed by a Certification Authority may use this key pair to
   authenticate to the directory server if the user's certificate is
   requested by the server. The user's certificate subject field SHOULD
   be the name of the user's directory entry, and the Certification
   Authority that issued the userÆs certificate must be sufficiently
   trusted by the directory server in order for the server to process
   the certificate. The means by which servers validate certificate
   paths is outside the scope of this document.

   A server MAY support mappings for certificates in which the subject
   field name is different from the name of the user's directory entry.
   A server which supports mappings of names MUST be capable of being
   configured to support certificates for which no mapping is required.

   The client will use the Start TLS operation [5] to negotiate the use
   of TLS security [6] on the connection to the LDAP server. The client
   need not have bound to the directory beforehand.

   In the TLS negotiation, the server MUST request a certificate. The
   client will provide its certificate to the server, and MUST perform
   a private key-based encryption, proving it has the private key
   associated with the certificate.

   In deployments that require protection of sensitive data in transit,
   the client and server MUST negotiate a ciphersuite which contains a
   bulk encryption algorithm of appropriate strength. Recommendations
   of cipher suites are given in section 10.

   The server MUST verify that the client's certificate is valid. The
   server will normally check that the certificate is issued by a known
   CA, and that none of the certificates on the client's certificate
   chain are invalid or revoked. There are several procedures by which
   the server can perform these checks.

   Following the successful completion of TLS negotiation, the client
   will send an LDAP bind request with the SASL "EXTERNAL" mechanism.

8. Other mechanisms

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8.1. Use of ANONYMOUS and PLAIN SASL Mechanisms

   As LDAP includes native anonymous and plaintext authentication
   methods, the "ANONYMOUS" and "PLAIN" SASL mechanisms are not used
   with LDAP. If an authorization identity of a form different from a
   DN is requested by the client, a mechanism that protects the
   password in transit SHOULD be used.

8.2. SASL Mechanisms not Considered in this Document

   The following SASL-based mechanisms are not considered in this
   document: KERBEROS_V4, GSSAPI and SKEY.

8.3. Use of EXTERNAL SASL Mechanism

   The "EXTERNAL" SASL mechanism can be used to request the LDAP server
   make use of security credentials exchanged by a lower layer. If a
   TLS session has not been established between the client and server
   prior to making the SASL EXTERNAL Bind request and there is no other
   external source of authentication credentials (e.g. IP-level
   security [8]), or if, during the process of establishing the TLS
   session, the server did not request the client's authentication
   credentials, the SASL EXTERNAL bind MUST fail with a result code of
   inappropriateAuthentication. Any client authentication and
   authorization state of the LDAP association is lost, so the LDAP
   association is in an anonymous state after the failure.

9. Authorization Identity

   The authorization identity is carried as part of the SASL
   credentials field in the LDAP Bind request and response.

   When the "EXTERNAL" SASL mechanism is being negotiated, if the
   credentials field is present, it contains an authorization identity
   of the authzId form described below.

   Other mechanisms define the location of the authorization identity
   in the credentials field.

9.1. Authorization Identity Syntax

   The authorization identity is a string in the UTF-8 character set,
   corresponding to the following ABNF [7]:

   ; Specific predefined authorization (authz) id schemes are
   ; defined below -- new schemes may be defined in the future.

   authzId = dnAuthzId / uAuthzId

   ; distinguished-name-based authz id.
   dnAuthzId = "dn:" dn
   dn = utf8string    ; with syntax defined in RFC 2253

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   ; unspecified authorization id, UTF-8 encoded.
   uAuthzId = "u:" userid
   userid = utf8string    ; syntax unspecified

9.1.1. DN-based Authorization Identity

   All servers that support the storage of authentication credentials,
   such as passwords or certificates, in the directory MUST support the
   dnAuthzId choice. The format for distinguishedName is defined in
   Section 3 of draft-zeilenga-ldapbis-rfc2253-01.txt.

9.1.2. Unspecified Authorization Identity

   The uAuthzId choice allows for compatibility with client
   applications that wish to authenticate to a local directory but do
   not know their own distinguished name or that do not have a
   directory entry. The format of utf8string is defined as only a
   sequence of UTF-8 encoded ISO 10646 characters, and further
   interpretation is subject to prior agreement between the client and
   server.

   For example, the userid could identify a user of a specific
   directory service, or be a login name or the local-part of an RFC
   822 email address. In general a uAuthzId MUST NOT be assumed to be
   globally unique.

   Additional authorization identity schemes MAY be defined in future
   versions of this document.

10. TLS Ciphersuites

   The following ciphersuites defined in [6] MUST NOT be used for
   confidentiality protection of passwords or data:

         TLS_NULL_WITH_NULL_NULL
         TLS_RSA_WITH_NULL_MD5
         TLS_RSA_WITH_NULL_SHA

   The following ciphersuites defined in [6] can be cracked easily
   (less than a day of CPU time on a standard CPU in 2000). These
   ciphersuites are NOT RECOMMENDED for use in confidentiality
   protection of passwords or data. Client and server implementers
   SHOULD carefully consider the value of the password or data being
   protected before using these ciphersuites:

         TLS_RSA_EXPORT_WITH_RC4_40_MD5
         TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5
         TLS_RSA_EXPORT_WITH_DES40_CBC_SHA
         TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
         TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA
         TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA

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         TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
         TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
         TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA

   The following ciphersuites are vulnerable to man-in-the-middle
   attacks, and SHOULD NOT be used to protect passwords or sensitive
   data, unless the network configuration is such that the danger of a
   man-in-the-middle attack is tolerable:

         TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
         TLS_DH_anon_WITH_RC4_128_MD5
         TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA
         TLS_DH_anon_WITH_DES_CBC_SHA
         TLS_DH_anon_WITH_3DES_EDE_CBC_SHA

   A client or server that supports TLS MUST support
   TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA and MAY support other ciphersuites
   offering equivalent or better protection.

11. SASL service name for LDAP

   For use with SASL [2], a protocol must specify a service name to be
   used with various SASL mechanisms, such as GSSAPI. For LDAP, the
   service name is "ldap", which has been registered with the IANA as a
   GSSAPI service name.

12.  SASL Integrity and Privacy Protections

   Any negotiated SASL integrity and privacy protections SHALL start on
   the first octet of the first LDAP PDU following successful
   completion of the SASL bind operation. If lower level security layer
   is negotiated, such as TLS, any SASL security services SHALL be
   layered on top of such security layers regardless of the order of
   their negotiation.

13. Security Considerations

   Security issues are discussed throughout this memo; the
   (unsurprising) conclusion is that mandatory security is important,
   and that session encryption is required when snooping is a problem.

   Servers are encouraged to prevent modifications by anonymous users.
   Servers may also wish to minimize denial of service attacks by
   timing out idle connections, and returning the unwillingToPerform
   result code rather than performing computationally expensive
   operations requested by unauthorized clients.

   A connection on which the client has not performed the Start TLS
   operation or negotiated a suitable SASL mechanism for connection
   integrity and encryption services is subject to man-in-the-middle
   attacks to view and modify information in transit.



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   Additional security considerations relating to the EXTERNAL
   mechanism to negotiate TLS can be found in [2], [5] and [6].

14. Acknowledgements

   The author acknowledges the work of Mark Wahl, Harald Tveit
   Alvestrand, Jeff Hodges, and RL "Bob" Morgan who authored RFC 2829,
   the document upon which this work is largely based. RFC 2829 was a
   product of the IETF LDAPEXT Working Group.

   This document is based upon input of the IETF LDAP Revision working
   group. The contributions of its members is greatly appreciated.

15. Bibliography

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

   [2] Myers, J., "Simple Authentication and Security Layer (SASL)",
       RFC 2222, October 1997.

   [3] Bradner, S., "Key words for use in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

   [4] Leach, P. and C. Newman, "Using Digest Authentication as a SASL
       Mechanism", RFC 2831, May 2000.

   [5] Hodges, J., Morgan, R. and M. Wahl, "Lightweight Directory
       Access Protocol (v3): Extension for Transport Layer Security",
       RFC 2830, May 2000.

   [6] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC
       2246, January 1999.

   [7] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
       Specifications: ABNF", RFC 2234, November 1997.

   [8] Kent, S. and R. Atkinson, "Security Architecture for the
       Internet Protocol", RFC 2401, November 1998.

15. Author's Address

   Roger Harrison
   Novell, Inc.
   1800 S. Novell Place
   Provo, UT 84606
   +1 801 861 2642
   roger_harrison@novell.com

16. Full Copyright Statement

   Copyright (C) The Internet Society (2000). All Rights Reserved.



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   This document and translations of it may be copied and furnished to
   others, and derivative works that comment on or otherwise explain it
   or assist in its implementation may be prepared, copied, published
   and distributed, in whole or in part, without restriction of any
   kind, provided that the above copyright notice and this paragraph
   are included on all such copies and derivative works. However, this
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   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Appendix A - Change History

   This appendix lists the changes made to the text of RFC 2829 in
   preparing this document.

A.0. General Editorial Changes

   Changed title: LDAP to LDAPv3

   Changed other instances of the term LDAP to LDAPv3 where v3 of the
   protocol is implied. Also made all references to LDAPv3 use the same
   wording.
   Made a small number of grammatical changes to improve readability.

   Made capitalization in section headings consistent.

A.1. Changes to Section 1

   None

A.2. Changes to Section 2

   None

A.3. Changes to Section 3

   None

A.4 Changes to Section 4

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   Changed "Distinguished Name" to "LDAP distinguished name".

A.5. Changes to Section 5

   Added the following sentence: "Servers SHOULD NOT allow clients with
   anonymous authentication to modify directory entries or access
   sensitive information in directory entries."

A.5.1. Changes to Section 5.1

   Replaced the text describing the procedure for performing an
   anonymous bind (protocol) with a reference to section 4.2 of RFC
   2251 (the protocol spec).

A.6. Changes to Section 6.

   Reorganized text in section 6.1 as follows:

   1. Added a new section (6.1) titled "Simple Authentication" and
   moved one of two introductory paragraphs for section 6 into section
   6.1. Added sentences to the paragraph indicating:

        a. simple authentication is not suitable for environments where
        confidentiality is not available.

        b. LDAP implementations SHOULD NOT support simple
        authentication unless confidentiality and data integrity
        mechanisms are in force.

   2. Moved first paragraph of section 6 (beginning with "LDAP
   implementations MUST support authentication with a passwordà") to
   section on Digest Authentication (Now section 6.2).
A.6.1. Changes to Section 6.1.

   Renamed section to 6.2

   Added sentence from original section 6 indicating that the DIGEST-
   MD5 SASL mechanism is required for all conforming LDAPv3
   implementations

A.6.2 Changes to Section 6.2

   Renamed section to 6.3

   Reworded first paragraph to remove reference to user and the
   userPassword password attribute Made the first paragraph more
   general by simply saying that if a directory supports simple
   authentication that the simple bind operation MAY performed
   following negotiation of a TLS ciphersuite that supports
   confidentiality.



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   Replaced "the name of the user's entry" with "a DN" since not all
   bind operations are performed on behalf of a "user."

   Added Section 6.3.1 heading just prior to paragraph 5.

   Paragraph 5: replaced "The server" with "DSAs that map the DN sent
   in the bind request to a directory entry with a userPassword
   attribute."

A.6.3. Changes to section 6.3.

   Renamed to section 6.4.

A.7. Changes to section 7.

   none

A.7.1. Changes to section 7.1.

   Clarified the entity issuing a certificate by moving the phrase "to
   have issued the certificate" immediately after "Certification
   Authority."

A.8. Changes to section 8.

   Removed the first paragraph because simple authentication is covered
   explicitly in section 6.

   Added section 8.1. heading just prior to second paragraph.

   Added section 8.2. heading just prior to third paragraph.

   Added section 8.3. heading just prior to fourth paragraph.

A.9. Changes to section 9.

   Paragraph 2: changed "EXTERNAL mechanism" to "EXTERNAL SASL
   mechanism."

   Added section 9.1. heading.

   Modified a comment in the ABNF from "unspecified userid" to
   "unspecified authz id".

   Deleted sentence, "A utf8string is defined to be the UTF-8 encoding
   of one or more ISO 10646 characters," because it is redundant.

   Added section 9.1.1. heading.

   Added section 9.1.2. heading.

A.10. Changes to Section 10.


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   Updated reference to cracking from a week of CPU time in 1997 to be
   a day of CPU time in 2000.

   Added text: "These ciphersuites are NOT RECOMMENDED for use... and
   server implementers SHOULD" to sentence just prior the second list
   of ciphersuites.

   Added text: "and MAY support other ciphersuites offering equivalent
   or better protection," to the last paragraph of the section.

A.11. Changes to Section 11.

   None

A.12. Changes to Section 12.

   Inserted new section 12 that specifies when SASL protections begin
   following SASL negotiation, etc.. The original section 12 is
   renumbered to become section 13.

A.13 Changes to Section 13 (original section 12).

   None

Appendix B Issues to be Resolved

   This appendix lists open questions and issues that need to be
   resolved before work on this document is deemed complete.

B.1.

   Section 1 lists 6 security mechanisms that can be used by LADP
   servers. I'm not sure what mechanism 5, "Resource limitation by
   means of administrative limits on service controls" means.

B.2.

   Section 2 paragraph 1 defines the term, "sensitive." Do we want to
   bring this term and other security-related terms in alignment with
   usage with the IETF security glossary (RFC 2828)?

B.3.

   Section 2, deployment scenario 2: What is meant by the term "secure
   authentication function?"

B.4.

   Section 3, deployment scenario 3: What is meant by the phrase,
   "directory data is authenticated by the server?"

B.5.


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   Section 4 paragraph 3: What is meatn by the phrase, "this means that
   either this data is useless for faking authentication (like the Unix
   "/etc/passwd" file format used to be)?"

B.6.

   Section 4 paragraph 7 begins: "For a directory needing session
   protection..."  Is this referring to data confidentiality or data
   integrity or both?

B.7.

   Section 4 paragraph 8 indicates that "information about the server
   fetched fetched prior to the TLS negotiation" must be discarded. Do
   we want to explicitly state that this applies to information fetched
   prior to the *completion* of the TLS negotiation or is this going
   too far?

B.8.

   Section 4 paragraph 9 indicates that clients SHOULD check the
   supportedSASLMechanisms list both before and after a SASL security
   layer is negotiated to ensure that they are using the best available
   security mechanism supported mutually by the client and server. A
   note at the end of the paragraph indicates that this is a SHOULD
   since there are environments where the client might get a list of
   supported SASL mechanisms from a different trusted source.

   I wonder if the intent of this could be restated more plainly using
   one of these two approaches (I've paraphrased for the sake of
   brevity):

   Approach 1: Clients SHOULD check the supportedSASLMechanisms list
   both before and after SASL negotiation or clients SHOULD use a
   different trusted source to determine available supported SASL
   mechanisms.

   Approach 2: Clients MUST check the supportedSASLMechanisms list both
   before and after SASL negotiation UNLESS they use a different
   trusted source to determine available supported SASL mechanisms.

B.9.

   Section 6.3.1 states: "DSAs that map the DN sent in the bind request
   to a directory entry with a userPassword attribute will... compare
   [each value in the named user's entry]... with the presented
   password."  This implies that this this applies only to user entries
   with userPassword attributes.  What about other types of entries
   that might allow passwords and might store in the password
   information in other attributes?  Do we want to make this text more
   general?



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