Internet Draft
Individual Submission                               R. Harrison, Editor
Document: draft-ietf-ldapbis-authmeth-00.txt
Internet Draft                                             Novell, Inc.
Document: draft-ietf-ldapbis-authmeth-01.txt              July 19, 2001
Intended Category: Draft Standard                     February 20, 2001
Obsoletes: RFC 2829 2829, RFC 2830

                         Authentication Methods
                                  and
                  Connection Level Security Mechanisms
                               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>.

   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 specifies particular combinations of describes LDAPv3 authentication methods and connection
   level security mechanisms that are required of all conforming LDAPv3
   server implementations and recommended makes recommendations for combinations of
   these mechanisms to be used in various deployment circumstances.

   Among the mechanisms described are

     - the LDAPv3 Bind operation used for authenticating LDAP clients
       to LDAP servers.

     - the Start TLS operation used to initiate Transport Layer
       Security on an established connection between an LDAP client and
       server.

                  Authentication Methods for LDAPv3 [1]
   implementations.     July 19, 2001

     - various forms of authentication including anonymous
       authentication, password-based authentication, and certificate
       based authentication.

1. Conventions Used in this Document

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

   Several terms and concepts relating to authentication and
   authorization are presented in Appendix B of this document. While
   the definition of these terms and concepts is outside the scope of
   this document, an understanding of them is prerequisite to
   understanding much of the material in this document. Readers who are
   unfamiliar with security-related concepts are encouraged to review
   Appendix B before reading the remainder of 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 RFC 2119
   [ReqsKeywords].

2. 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

   It is vital that these security functions be interoperable; interoperable among all
   LDAP clients and servers on the Internet; 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:

Harrison               Expires August 20, 2001               [Page 1]
                  Authentication Methods for LDAPv3 February 20, 2001

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

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

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

   (4) Unauthorized modification of directory data,

   (5) Unauthorized modification of configuration, configuration information,

   (6) Unauthorized or excessive use of resources (denial of service),
       and
                  Authentication Methods for LDAPv3     July 19, 2001

   (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] [SASL] mechanism set,
       possibly backed by the TLS [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 usage 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

3. Required Security Mechanisms

   It is an LDAP client using clear that allowing any implementation, faced with the directory to retrieve or store
   information.

Harrison               Expires August 20, 2001               [Page 2]
                  Authentication Methods for LDAPv3 February 20, 2001

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are above
   requirements, to be interpreted as described in RFC 2119 [3].

2. Example deployment scenarios

   The following scenarios are typical for LDAP directories on the
   Internet, pick and have different security requirements. (In choose among the
   following, "sensitive" means data possible alternatives is
   not a strategy that will cause real damage is likely to lead to interoperability. In the
   owner if revealed; there may
   absence of mandates, clients will be data written that is protected but not
   sensitive). This is do not intended to be a comprehensive list, other
   scenarios 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 possible, especially on physically protected networks.

   (1) A read-only directory, containing no sensitive data, accessible the most difficult for an attacker
   to "anyone", perform, and TCP connection hijacking or IP spoofing 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
       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 justified based on identity. TCP connection hijacking the
   perceived risk of active intermediary attacks.

   Given the presence of the Directory, there is not
       currently a problem. This scenario requires a secure
       authentication function.

   (3) A read-only directory containing no sensitive data; strong desire to see
   mechanisms where identities take the form of an LDAP distinguished
   name and authentication data can be stored in the
       client needs to ensure directory; this
                  Authentication Methods for LDAPv3     July 19, 2001

   means that the directory either this data is authenticated
       by useless for faking authentication
   (like the server and not modified while being returned from Unix "/etc/passwd" file format used to be), or its content
   is never passed across the
       server.

   (4) A read-write directory, containing no sensitive data; read
       access wire unprotected - that is, it's either
   updated outside the protocol or it is available only updated in sessions well
   protected against snooping. It is also desirable to "anyone", update access allow
   authentication methods to properly
       authorized persons. TCP connection hijacking is not currently 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
       problem. 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 scenario requires a secure provides client
       authentication
       function.

   (5) A with protection against passive eavesdropping
       attacks, but does not provide protection against active
       intermediary attacks.

   (3) For a directory containing sensitive data. This scenario requires needing session confidentiality protection AND secure authentication.

3. Authentication and Authorization: Definitions and Concepts

   This authentication,
       the Start TLS operation described in section defines basic terms, concepts, 5, and interrelationships
   regarding authentication, authorization, credentials, and identity.
   These concepts either the
       simple authentication choice or the SASL EXTERNAL mechanism, are
       to be used in describing how various security
   approaches are utilized in client together. Implementations SHOULD support
       authentication and authorization.

3.1. Access Control Policy

   An access control policy is with a set of rules defining the protection
   of resources, generally password as described 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 section 7.2, and mechanisms, such
       SHOULD support authentication with a certificate as those described here, enable the expression in
       section 8.1. Together, these can provide integrity and
       disclosure protection of access control policies transmitted data, and their enforcement. Access control

Harrison               Expires August 20, 2001               [Page 3]
                  Authentication Methods for LDAPv3 February 20, 2001

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

3.2. Access Control Factors

   A request, when it is being processed by a
       client and server, may be associated
   with a wide variety of security-related factors (section 4.2 of
   [1]). The including protection against active
       intermediary attacks.

   If TLS is negotiated, the client MUST discard all information about
   the server uses these factors to determine whether and how fetched prior to
   process the request. These are called access control factors (ACFs).
   They might include source IP address, encryption strength, TLS negotiation. In particular, the type
   of operation being requested, time
   value of day, etc. Some factors may be
   specific to the request itself, others may supportedSASLMechanisms MAY be associated with different after TLS has been
   negotiated (specifically, the
   connection via which EXTERNAL mechanism or the request is transmitted, others (e.g. time
   of day) may be "environmental".

   Access control policies proposed
   PLAIN mechanism are expressed in terms of access control
   factors. E.g., likely to only be listed after a request having ACFs i,j,k can perform operation Y
   on resource Z. The set of ACFs that TLS negotiation
   has been performed).

   If a server makes available for
   such expressions SASL security layer is implementation-specific.

3.3. Authentication, Credentials, Identity

   Authentication credentials are negotiated, the evidence supplied by one party to
   another, asserting client MUST discard all
   information about the identity of server fetched prior to SASL. In particular,
   if the supplying party (e.g. a user)
   who client is attempting configured to establish an association with support multiple SASL mechanisms, it
   SHOULD fetch supportedSASLMechanisms both before and after the other party
   (typically a server). Authentication SASL
   security layer is the process of generating,
   transmitting, and verifying these credentials negotiated and thus verify that the identity
   they assert. An authentication identity is value has not
   changed after the name presented in a
   credential.

   There are many forms of authentication credentials -- SASL security layer was negotiated. This detects
   active attacks which remove supported SASL mechanisms from the form used
   depends upon
   supportedSASLMechanisms list, and allows the particular authentication client to ensure that
   it is using the best mechanism negotiated supported by
   the parties. For example: X.509 certificates, Kerberos tickets,
   simple identity both client 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 server
   (additionally, this is one kind of access control factor. It a SHOULD to allow for environments where the
   supported SASL mechanisms list is provided to the name client through a
   different trusted source, e.g. as part of the user or other entity a digitally signed
   object).

                  Authentication Methods for LDAPv3     July 19, 2001

   Appendix A contains example deployment scenarios that requests list the
   mechanisms that
   operations might be performed. Access control policies are often expressed
   in terms used to achieve a reasonable level of authorization identities; e.g., entity X can perform
   operation Y on resource Z.
   security in various circumstances.

4. Bind Operation

   The authorization identity bound Bind operation allows authentication information to an association is often exactly be exchanged
   between the same client and server.

4.1 Bind Request

   The Bind Request is defined in section 4.2 of [LDAPv3] as the follows:

        BindRequest ::= [APPLICATION 0] SEQUENCE {
                version                 INTEGER (1 .. 127),
                name                    LDAPDN,
                authentication identity presented by          AuthenticationChoice }

        AuthenticationChoice ::= CHOICE {
                simple                  [0] OCTET STRING,
                                        -- 1 and 2 reserved
                sasl                    [ReqsKeywords] SaslCredentials
   }

        SaslCredentials ::= SEQUENCE {
                mechanism               LDAPString,
                credentials             OCTET STRING OPTIONAL }

   Parameters of the client, but
   it may Bind Request are:

     - version: A version number indicating the version of the protocol
       to be different. SASL allows clients used in this protocol session. This document describes
       version 3 of the LDAP protocol. Note that there is no version
       negotiation, and the client just sets this parameter to specify an authorization
   identity distinct from the authentication identity asserted by
       version it desires. If the
   client's credentials. This permits agents such client requests protocol version 2, a
       server that supports the version 2 protocol as proxy described in
       [RFC1777] will not return any v3-specific protocol fields. (Note
       that not all LDAP servers will support protocol version 2, since
       they may be unable to
   authenticate using their own credentials, yet request generate the access
   privileges attribute syntaxes associated
       with version 2.)

     - name: The name of the identity directory object that the client wishes to
       bind as. This field may take on a null value (a zero length
       string) for which they are proxying [2]. Also, the form purposes of anonymous binds, when authentication identity supplied by
       has been performed at a service like TLS

Harrison               Expires August 20, 2001               [Page 4]
                  Authentication Methods for LDAPv3 February 20, 2001

   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 lower layer, or when using SASL
       credentials supplied
   by with a client is implementation-specific.

4. Required security mechanisms

   It is clear mechanism that allowing any implementation, faced with includes the above
   requirements, to pick and choose among name in the possible alternatives
       credentials. Server behavior is undefined when the name is
   not a strategy that
       null value, simple authentication is likely to lead to interoperability. In the
   absence of mandates, clients will be written used, and a password is
       specified. Note 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 server SHOULD NOT perform any alias
       dereferencing in determining the most difficult for an attacker object to perform, and bind as.

                  Authentication Methods for an implementation LDAPv3     July 19, 2001

     - authentication: information used to protect against. Methods
   that protect only against hostile client and passive eavesdropping
   attacks are useful authenticate the name, if
       any, provided in situations where the cost Bind Request.

   Upon receipt of protection
   against active intermediary attacks is not justified based on a Bind Request, a protocol server will authenticate
   the
   perceived risk of active intermediary attacks.

   Given requesting client, if necessary. The server will then return a
   Bind Response to the presence client indicating the status of the Directory, there
   authentication.

   Authorization is a strong desire to see
   mechanisms where identities take the form use of an LDAP distinguished
   name and this authentication data can information when
   performing operations. Authorization MAY be stored in affected by factors
   outside of 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 LDAP Bind request, such as lower layer security
   services.

4.2. Bind Response

   The Bind Response is never passed across defined in section 4.2 of [LDAPv3] as follows.

        BindResponse ::= [APPLICATION 1] SEQUENCE {
             COMPONENTS OF LDAPResult,
             serverSaslCreds    [ABNF] OCTET STRING OPTIONAL }

   BindResponse consists simply of an indication from the wire unprotected - that is, it's either
   updated outside server of 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
   status of user identities the client's request for backwards compatibility with
   non-LDAP-based authentication services.

   Therefore, authentication.

   If 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 bind was successful, the DIGEST-MD5 resultCode will be success.
   Otherwise it will be one of:

     - operationsError: server encountered an internal error.

     - protocolError: unrecognized version number or incorrect PDU
       structure.

     - authMethodNotSupported: unrecognized SASL mechanism
       [4], as described in section 6.2. This provides client name.

     - strongAuthRequired: the server requires authentication be
       performed with protection against passive eavesdropping
       attacks, but does not provide protection against active
       intermediary attacks.

   (3) For a directory needing session protection SASL mechanism.

     - referral: this server cannot accept this bind and authentication, the Start TLS extended operation [5], and either client
       should try another.

     - saslBindInProgress: the simple
       authentication choice or server requires the SASL EXTERNAL mechanism, are client to be
       used together. Implementations SHOULD support authentication
       with send a password as described in section 6.2, and SHOULD support

Harrison               Expires August 20, 2001               [Page 5]
                  Authentication Methods for LDAPv3 February 20, 2001

       authentication new
       bind request, 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 same sasl mechanism, to continue the TLS negotiation. In particular,
       authentication process.

     - inappropriateAuthentication: the
   value server requires the client
       which had attempted to bind anonymously or without supplying
       credentials to provide some form of supportedSASLMechanisms MAY be different after TLS has been
   negotiated (specifically, credentials.

     - invalidCredentials: the EXTERNAL mechanism wrong password was supplied or the proposed
   PLAIN mechanism are likely to only be listed after a TLS negotiation
   has been performed).

   If a SASL security layer
       credentials could not be processed.

     - unavailable: the server is negotiated, shutting down.

                  Authentication Methods for LDAPv3     July 19, 2001

   If the client server does not support the client's requested protocol
   version it MUST discard all
   information about set the server fetched prior resultCode to SASL. In particular,
   if protocolError.

   If the client is configured to support multiple SASL mechanisms, receives a BindResponse response where the resultCode
   was protocolError it
   SHOULD fetch supportedSASLMechanisms both before and after MUST close the SASL
   security layer is negotiated and verify that connection as the value has not
   changed after server will be
   unwilling to accept further operations. (This is for compatibility
   with earlier versions of LDAP, in which the SASL security layer bind was negotiated. This detects
   active attacks which remove supported SASL mechanisms from always the
   supportedSASLMechanisms list,
   first operation and allows there was no negotiation.)

   The serverSaslCreds are used as part of a SASL-defined bind
   mechanism to allow the client to ensure that
   it is using authenticate the best mechanism supported by both client and server
   (additionally, this is a SHOULD to allow for environments where the
   supported SASL mechanisms list which it
   is provided communicating, or to perform "challenge-response" authentication.
   If 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 bound with the password choice, or entries generally require client authentication.
   Clients that do the SASL mechanism
   does not intend to perform any of these operations
   typically use anonymous authentication. Servers SHOULD NOT allow
   clients with anonymous authentication require the server to modify directory entries or
   access sensitive return 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 the client,
   then this field is not to retrieve be included in the supportedSASLMechanisms attribute result.

4.3. Sequencing 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 Bind Operation

4.3.1. Effect of Multiple Bind Requests

   Subsequent to anonymously authenticated clients.

5.1. Anonymous Authentication Procedure

Harrison               Expires August 20, 2001               [Page 6]
                  Authentication Methods for LDAPv3 February 20, 2001

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

   An LDAP request, A client MAY also send a bind anonymously using
   request to change its identity. Such a bind request has the procedure defined
   in section 4.2 effect
   of RFC 2251.

5.2. Anonymous abandoning all operations outstanding on the connection. (This
   simplifies server implementation.) Authentication from earlier binds
   are subsequently ignored, and TLS

   An LDAP client MAY use so if the Start TLS operation [5] to negotiate bind fails, the
   use of TLS security [6]. connection
   will be treated as anonymous (see section 4.3.3). If the client a SASL transfer
   encryption or integrity mechanism has not bound beforehand, been negotiated, and that
   mechanism does not support the changing of credentials from one
   identity to another, then until the client uses the EXTERNAL MUST instead establish a new
   connection.

   For some SASL mechanism to negotiate authentication mechanisms, it may be necessary for the recognition of
   client to invoke the client's certificate, BindRequest multiple times. If at any stage 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 wishes to successfully complete TLS negotiation if abort the bind process it MAY unbind and then drop
   the underlying connection. Clients MUST NOT invoke operations
   between two Bind requests made as part of a multi-stage bind.

4.3.2. Aborting SASL Bind Negotiation

   A client did
   not present may abort 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 SASL bind negotiation by sending a BindRequest
   with a different value in the "simple" authentication choice when mechanism field of SaslCredentials, or
   an AuthenticationChoice other than sasl.

   If the
   connection is protected against eavesdropping using TLS, as defined
   in section 6.3. LDAP implementations SHOULD NOT support
   authentication client sends a BindRequest with the "simple" authentication choice unless the
   data on sasl mechanism field as
   an empty string, the connection is protected using TLS or other privacy and
   data-integrity protection.

6.2. Digest Authentication

   LDAP implementations server MUST support authentication return a BindResponse with
   authMethodNotSupported as the resultCode. This will allow clients to
   abort a password
   using negotiation if it wishes to try again with the DIGEST-MD5 same SASL mechanism for password protection,
   mechanism.

4.3.3. Unbound Connection Treated as
   defined in section 6.1.

   An Anonymous

   Unlike LDAP client MAY determine whether v2, 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 client need not send a value of this attribute.

   In Bind Request in the first stage
   PDU of authentication, when the connection. The client is performing
   an "initial authentication" may request any operations and the
                  Authentication Methods for LDAPv3     July 19, 2001

   server MUST treat these as defined in section 2.1 of [4], anonymous. If the server requires that
   the client sends a bind request in which before browsing or modifying the version number is 3, directory, the
   authentication choice is sasl,
   server MAY reject a request other than binding, unbinding or an
   extended request with the sasl mechanism name is "DIGEST-
   MD5", and "operationsError" result.

   If the credentials are absent. The client did not bind before sending a request and receives an
   operationsError, it may then waits for send a
   response from Bind Request. If this also fails
   or the server client chooses not to this request.

Harrison               Expires August 20, 2001               [Page 7]
                  Authentication Methods for LDAPv3 February 20, 2001

   The server will respond with a bind response in which on the resultCode
   is saslBindInProgress, and existing connection, it
   will close the serverSaslCreds field is present. The
   contents of this field is a string defined connection, reopen it and begin again by "digest-challenge" first
   sending a PDU with a Bind Request. This will aid in
   section 2.1.1 interoperating
   with servers implementing other versions of [4]. The server SHOULD include a realm indication
   and MUST indicate support LDAP.

4.4. Using SASL for UTF-8. Other Security Services

   The client will send a bind request simple authentication option provides minimal authentication
   facilities, with a distinct message id, in
   which the version number is 3, contents of the authentication choice is sasl, field consisting
   only of a cleartext password. Note that the sasl mechanism name use of cleartext
   passwords is "DIGEST-MD5", and not recommended over open networks when the credentials contain underlying
   transport service cannot guarantee confidentiality; see the string
   "Security Considerations" section.

   The sasl choice allows for any mechanism defined by "digest-response" in section 2.1.2 of [4]. for use with SASL
   [RFC2222]. The
   serv-type is "ldap". mechanism field contains the name of the mechanism.
   The server will respond with a bind response in which credentials field contains the resultCode
   is either success, or arbitrary data used for
   authentication, inside an error indication. If the authentication OCTET STRING wrapper. Note that unlike
   some Internet application protocols where SASL is used, LDAP is
   successful and the server does not support subsequent
   authentication, then
   text-based, thus no base64 transformations are performed on the credentials field is absent.
   credentials.

   If any SASL-based integrity or confidentiality services are enabled,
   they take effect following the
   authentication is successful and transmission by the server supports subsequent
   authentication, then and
   reception by the credentials field contains client of the string
   defined final BindResponse with resultCode
   success.

   The client can request that the server use authentication
   information from a lower layer protocol by "response-auth" in section 2.1.3 using the SASL EXTERNAL
   mechanism.

4.4.1. Use of [4]. Support for
   subsequent authentication is OPTIONAL in clients ANONYMOUS and servers.

6.3. "simple" PLAIN SASL Mechanisms

   As LDAP includes native anonymous and plaintext authentication choice under TLS encryption

   Following
   methods, the negotiation of "ANONYMOUS" and "PLAIN" SASL mechanisms are not used
   with LDAP. If an appropriate TLS ciphersuite
   providing connection confidentiality [6], authorization identity of a client MAY authenticate
   to form different from a directory that supports the simple authentication choice
   DN is requested by
   performing the client, a simple bind operation.

   The client will use mechanism that protects the Start TLS operation [5]
   password in transit SHOULD be used.

4.4.2. Use of EXTERNAL SASL Mechanism

   The "EXTERNAL" SASL mechanism can be used to negotiate request the LDAP server
   make use of TLS security [6] on the connection to the LDAP server. The client
   need credentials exchanged by a lower layer. If a
   TLS session has not have bound to the directory beforehand.

   For this authentication procedure to be successful, been established between the client and server MUST negotiate a ciphersuite which contains a bulk encryption
   algorithm
   prior to making the SASL EXTERNAL Bind request and there is no other
   external source of appropriate strength. Recommendations on cipher suites
   are given in section 10.

   Following authentication credentials (e.g. IP-level
                  Authentication Methods for LDAPv3     July 19, 2001

   security [RFC2401]), or if, during the successful completion process of establishing the
   TLS negotiation, session, the client
   MUST send an LDAP bind server did not request with the version number of 3, client's authentication
   credentials, the
   name field containing SASL EXTERNAL bind MUST fail with a DN , result code of
   inappropriateAuthentication. Any client authentication and
   authorization state of the "simple" authentication choice,
   containing a password.

   6.3.1 "simple" Authentication Choice

   DSAs that map LDAP association is lost, so the DN sent LDAP
   association is in an anonymous state after the bind request to a directory entry
   with a userPassword attribute will, for each value failure.

4.4.3. SASL Mechanisms not Considered in this Document

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

4.5. SASL Authorization Identity

   The authorization identity is carried as part of the
   userPassword attribute SASL
   credentials field in the named user's entry, compare these for
   case-sensitive equality with LDAP Bind request and response.

   When the client's presented password. If
   there "EXTERNAL" SASL mechanism is a match, then being negotiated, if the server will respond with resultCode
   success, otherwise
   credentials field is present, it contains an authorization identity
   of the server will respond with resultCode
   invalidCredentials.

6.4. authzId form described below.

   Other authentication choices with TLS

Harrison               Expires August 20, 2001               [Page 8]
                  Authentication Methods for LDAPv3 February 20, 2001

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

4.5.1. Authorization Identity Syntax

   The authorization identity 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 string in which the public key has
   been signed by a Certification Authority may use this key pair to
   authenticate UTF-8 character set,
   corresponding to the directory server if the user's certificate is
   requested by the server. The user's certificate subject field SHOULD following ABNF grammar [ABNF]:

   ; Specific predefined authorization (authz) id schemes are
   ; defined below -- new schemes may be defined in the name of the user's directory entry, and the Certification
   Authority future.

   authzId = dnAuthzId / uAuthzId

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

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

4.5.1.1. DN-based Authorization Identity

   All servers that issued the userĘs certificate must be sufficiently
   trusted by support the directory server storage of authentication credentials,
   such as passwords or certificates, in order for the server to process directory MUST support the certificate.
   dnAuthzId choice. The means by which servers validate certificate
   paths format for distinguishedName is outside the scope defined in
   Section 3 of this document.

   A server MAY support mappings draft-zeilenga-ldapbis-rfc2253-01.txt.

4.5.1.2. Unspecified Authorization Identity
                  Authentication Methods for certificates in which the subject
   field name is different from the LDAPv3     July 19, 2001

   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 of the user's or that do not have a
   directory entry.
   A server which supports mappings of names MUST be capable The format of being
   configured to support certificates for which no mapping utf8string is required.

   The client will use the Start TLS operation [5] to negotiate the use defined as only a
   sequence of TLS security [6] on the connection UTF-8 encoded ISO 10646 characters, and further
   interpretation is subject to prior agreement between the LDAP server. The client
   need not have bound to and
   server.

   For example, the userid could identify a user of a specific
   directory beforehand.

   In the TLS negotiation, service, or be a login name or the server local-part of an RFC
   822 email address. In general a uAuthzId MUST request NOT be assumed to be
   globally unique.

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

4.6. SASL Service Name for LDAP

   For use with SASL [SASL], a certificate. The
   client will provide its certificate protocol must specify a service name to
   be used with various SASL mechanisms, such as GSSAPI. For LDAP, the server, and MUST perform
   a private key-based encryption, proving it
   service name is "ldap", which has the private key
   associated been registered with the certificate.

   In deployments that require protection of sensitive data in transit,
   the client and server MUST negotiate a ciphersuite which contains IANA as a
   bulk encryption algorithm
   GSSAPI service name.

4.7.  SASL Integrity and Privacy Protections

   Any negotiated SASL integrity and privacy protections SHALL start on
   the first octet of appropriate strength. Recommendations the first LDAP PDU following successful
   completion of cipher suites are given in section 10.

   The server MUST verify that the client's certificate SASL bind operation. If lower level security layer
   is valid. The
   server will normally check that negotiated, such as TLS, any SASL security services SHALL be
   layered on top of such security layers regardless of the certificate is issued by a known
   CA, and that none order of
   their negotiation.

5. Start TLS Operation

   The Start Transport Layer Security (StartTLS) operation provides the certificates
   ability to establish Transport Layer Security [TLS] on the client's certificate
   chain are invalid or revoked. There are several procedures an LDAP
   association.

5.1. Start TLS Request

   A client requests TLS establishment by which transmitting a Start TLS
   request PDU to the server can perform these checks.

   Following server. The Start TLS request is defined in terms
   of the successful completion [LDAPv3] ExtendedRequest as follows:

       ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
           requestName             [0] LDAPOID,
           requestValue            [LDAPv3] OCTET STRING OPTIONAL }

   The requestName portion of TLS negotiation, the client
   will send an LDAP bind Start TLS request with MUST be the SASL "EXTERNAL" mechanism.

8. Other mechanisms

Harrison               Expires August 20, 2001               [Page 9] OID
   "1.3.6.1.4.1.1466.20037".

   The requestValue field is absent.

                  Authentication Methods for LDAPv3 February 20,     July 19, 2001

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

   The client MUST NOT send any PDUs on this connection following this
   request until it receives a
   DN is requested by the client, Start TLS extended response.

5.2. Start TLS Response

   When 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 Start TLS request is made, the LDAP server
   make use of security credentials exchanged by a lower layer. If MUST return a Start TLS session has not been established between the client and server
   prior
   response PDU to making the SASL EXTERNAL Bind request and there is no other
   external source requestor.  The Start TLS response id defined in
   terms of authentication credentials (e.g. IP-level
   security [8]), or if, during the process [LDAPv3] ExtendedResponse as follows:

        ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
                COMPONENTS OF LDAPResult,
                responseName     [10] LDAPOID OPTIONAL,
                response         [11] OCTET STRING OPTIONAL }

   The responseName portion of establishing the Start TLS
   session, the server did not request the client's authentication
   credentials, the SASL EXTERNAL bind response MUST fail with a result code of
   inappropriateAuthentication. Any client authentication and
   authorization state of be the LDAP association OID
   "1.3.6.1.4.1.1466.20037". (Note that this OID is lost, so the LDAP
   association is same OID value
   used in an anonymous state after the failure.

9. Authorization Identity

   The authorization identity is carried as part requestName of the SASL
   credentials Start TLS request.)

   The response field in the LDAP Bind request and response.

   When the "EXTERNAL" SASL mechanism is being negotiated, if absent.

   The server MUST set the
   credentials resultCode field is present, it contains an authorization identity to either success or one of
   the authzId form described below.

   Other mechanisms define other values outlined in section 5.2.2.

5.2.1. "Success" Response

   If the location ExtendedResponse contains a resultCode of success, this
   indicates that the authorization identity
   in the credentials field.

9.1. Authorization Identity Syntax

   The authorization identity server is a string in willing and able to negotiate TLS.
   Refer to section 3, below, for details.

5.2.2. Response other than "success"

   If the UTF-8 character set,
   corresponding ExtendedResponse contains a resultCode other than success,
   this indicates that the server is unwilling or unable to negotiate
   TLS.

   If the following ABNF [7]:

   ; Specific predefined authorization (authz) id schemes are
   ; defined below -- new schemes may be defined in Start TLS extended request was not successful, the future.

   authzId = dnAuthzId / uAuthzId

   ; distinguished-name-based authz id.
   dnAuthzId = "dn:" dn
   dn = utf8string    ; resultCode
   will be one of:

   operationsError  (operations sequencing incorrect; e.g. TLS already
   established)

   protocolError    (TLS not supported or incorrect PDU structure)

   referral         (this server doesn't do TLS, try this one)

   unavailable      (e.g. some major problem with syntax defined TLS, or server is
   shutting down)

   The server MUST return operationsError if the client violates any of
   the Start TLS extended operation sequencing requirements described
   in RFC 2253

Harrison               Expires August 20, 2001              [Page 10] section 5.3, below.

                  Authentication Methods for LDAPv3 February 20,     July 19, 2001

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

9.1.1. DN-based Authorization Identity

   All servers that

   If the server does not support TLS (whether by design or by current
   configuration), it MUST set the storage resultCode to protocolError (see
   section 4.1.1 of authentication credentials,
   such as passwords [LDAPv3]), or certificates, to referral. The server MUST include
   an actual referral value in the directory MUST LDAP Result if it returns a
   resultCode of referral. The client's current session is unaffected
   if the server does not support TLS. The client MAY proceed with any
   LDAP operation, or it MAY close the
   dnAuthzId choice. connection.

   The format server MUST return unavailable if it supports TLS but cannot
   establish a TLS connection for distinguishedName some reason, e.g. the certificate
   server not responding, it cannot contact its TLS implementation, or
   if the server is defined in
   Section 3 process of draft-zeilenga-ldapbis-rfc2253-01.txt.

9.1.2. Unspecified Authorization Identity shutting down. 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 MAY retry
   the StartTLS operation, or that do not have a
   directory entry. The format of utf8string is defined as only a
   sequence it MAY proceed with any other LDAP
   operation, or it MAY close the connection.

5.3.  Sequencing of UTF-8 encoded ISO 10646 characters, and further
   interpretation is subject to prior agreement between the client Start TLS Operation

   This section describes the overall procedures clients and
   server.

   For example, servers
   MUST follow for TLS establishment. These procedures take into
   consideration various aspects of the userid could identify a user overall security of a specific
   directory service, or be a login name or the local-part LDAP
   association including discovery of an RFC
   822 email address. In general resultant security level and
   assertion of the client's authorization identity.

   Note that the precise effects, on a uAuthzId MUST NOT be assumed to be
   globally unique.

   Additional client's authorization identity schemes MAY be defined in future
   versions identity,
   of this document.

10. establishing TLS Ciphersuites on an LDAP association are described in detail
   in section 5.5.

5.3.1.  Requesting to Start TLS on an LDAP Association

   The following ciphersuites defined client MAY send the Start TLS extended request at any time after
   establishing an LDAP association, except that in [6] the following cases
   the client 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 send a day of CPU time Start TLS extended request:

        - if TLS is currently established on the connection, or
        - during a standard CPU in 2000). These
   ciphersuites are NOT RECOMMENDED for use in confidentiality
   protection of passwords multi-stage SASL negotiation, or data. Client and server implementers
   SHOULD carefully consider
        - if there are any LDAP operations outstanding on the value
   connection.

   The result of violating any 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

Harrison               Expires August 20, 2001              [Page 11]
                  Authentication Methods for LDAPv3 February 20, 2001

         TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
         TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
         TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA requirements is a resultCode of
   operationsError, as described above in section 2.3.

   The following ciphersuites are vulnerable to man-in-the-middle
   attacks, and SHOULD NOT be used to protect passwords client MAY have already performed a Bind operation when it sends
   a Start TLS request, or sensitive
   data, unless the network configuration is such that client might have not yet bound.

   If 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 did not establish a TLS connection before sending any
   other requests, and the server that supports requires the client to establish a
   TLS connection before performing a particular request, the server
   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 reject that request with SASL [2], a protocol must specify confidentialityRequired or
   strongAuthRequired result. The client MAY send a service name Start TLS extended
   request, or it MAY choose to be
   used close the connection.

5.3.2.  Starting TLS
                  Authentication Methods for LDAPv3     July 19, 2001

   The server will return an extended response with various SASL mechanisms, such as GSSAPI. For LDAP, the
   service name resultCode of
   success if it is "ldap", willing and able to negotiate TLS.  It will return
   other resultCodes, documented above, if it is unable.

   In the successful case, the client, which has been registered with ceased to transfer
   LDAP requests on the IANA as connection, MUST either begin a
   GSSAPI service name.

12.  SASL Integrity and Privacy Protections

   Any negotiated SASL integrity and privacy protections SHALL start on TLS negotiation
   or close the first octet of connection. The client will send PDUs in the first LDAP PDU following successful
   completion of TLS Record
   Protocol directly over the SASL bind operation. If lower level security layer
   is negotiated, such as TLS, any SASL security services SHALL be
   layered on top underlying transport connection to the
   server to initiate TLS negotiation [TLS].

5.3.3.  TLS Version Negotiation

   Negotiating the version of such security layers regardless TLS or SSL to be used is a part of the order
   TLS Handshake Protocol, as documented in [TLS]. Please refer to that
   document for details.

5.3.4.  Discovery of
   their negotiation.

13. Security Considerations Resultant Security issues are discussed throughout this memo; the
   (unsurprising) conclusion Level

   After a TLS connection is that mandatory security established on an LDAP association, both
   parties MUST individually decide whether or not to continue based on
   the privacy level achieved. Ascertaining the TLS connection's
   privacy level is important, implementation dependent, and accomplished by
   communicating with one's respective local TLS implementation.

   If the client or server decides that session encryption is required when snooping the level of authentication or
   privacy is a problem.

   Servers are encouraged to prevent modifications by anonymous users.
   Servers may also wish not high enough for it to minimize denial of service attacks by
   timing out idle connections, and returning continue, it SHOULD gracefully
   close the unwillingToPerform
   result code rather than performing computationally expensive
   operations requested by unauthorized clients.

   A TLS connection on which immediately after the client TLS negotiation has not performed
   completed (see sections 5.4.1 and 5.5.2 below). If the client
   decides to continue, it MAY attempt to Start TLS
   operation again, it MAY send
   an unbind request, or negotiated it MAY send any other LDAP request.

5.3.5.  Assertion of Client's Authorization Identity

   The client MAY, upon receipt of 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.

Harrison               Expires August 20, 2001              [Page 12]
                  Authentication Methods for LDAPv3 February 20, 2001

   Additional security considerations relating to the EXTERNAL
   mechanism to negotiate Start TLS can response indicating
   success, assert that a specific authorization identity be found utilized
   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, determining the document upon which client's authorization status. The client
   accomplishes this work is largely based. RFC 2829 was via an LDAP Bind request specifying a
   product SASL
   mechanism of "EXTERNAL" [SASL] (see section 5.5.1.2 below).

5.3.6.  Server Identity Check

   The client MUST check its understanding of the IETF LDAPEXT Working Group.

   This document server's hostname
   against the server's identity as presented in the server's
   Certificate message, in order to prevent man-in-the-middle attacks.

   Matching is based upon input of performed according to these rules:

     - The client MUST use the server hostname it used to open the IETF LDAP Revision working
   group.
       connection as the value to compare against the server name as
       expressed in the server's certificate.  The contributions client MUST NOT use
       the server's canonical DNS name or any other derived form 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
       name.

                  Authentication and Security Layer (SASL)",
       RFC 2222, October 1997.

   [3] Bradner, S., "Key words Methods for use LDAPv3     July 19, 2001

     - If a subjectAltName extension of type dNSName is present in RFCs to Indicate Requirement
       Levels", BCP 14, RFC 2119, March 1997.

   [4] Leach, P. and C. Newman, "Using Digest Authentication the
       certificate, it SHOULD be used as the source of the server's
       identity.

     - Matching is case-insensitive.

     - The "*" wildcard character is allowed.  If present, it applies
       only to the left-most name component.

   E.g. *.bar.com would match a.bar.com, b.bar.com, etc. but not
   bar.com.  If more than one identity of 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 given type is present in
   the certificate (e.g. more than one dNSName name), a match in any
   one of the set is considered acceptable.

   If the hostname does not match the dNSName-based identity in the
   certificate per the above check, user-oriented clients SHOULD either
   notify the user (clients MAY give the user the opportunity to
   continue with the connection in any case) or terminate the
   connection and indicate that the server's identity is suspect.
   Automated clients SHOULD close the connection, returning and/or
   logging an error indicating that the server's identity is suspect.

   Beyond the server identity checks described in this section, clients
   SHOULD be prepared to do further checking to ensure that the server
   is authorized to provide the service it is observed to provide. The
   client MAY need to make use of local policy information.

5.3.7.  Refresh of Server Capabilities Information

   The client MUST refresh any cached server capabilities information
   (e.g. from the server's root DSE; see section 3.4 of [LDAPv3]) upon
   TLS Protocol Version 1.0", RFC
       2246, January 1999.

   [7] Crocker, D., Ed. session establishment. This is necessary to protect against
   active-intermediary attacks that may have altered any server
   capabilities information retrieved prior to TLS establishment. The
   server MAY advertise different capabilities after TLS establishment.

5.4.  Closing a TLS Connection

   Two forms of TLS connection closure--graceful and P. Overell, "Augmented BNF abrupt--are
   supported.

5.4.1.  Graceful Closure

   Either the client or server MAY terminate the TLS connection on an
   LDAP association by sending a TLS closure alert. This will leave the
   LDAP association intact.

   Before closing a TLS connection, the client MUST [RGH18]either wait
   for Syntax
       Specifications: ABNF", RFC 2234, November 1997.

   [8] Kent, S. and R. Atkinson, "Security Architecture any outstanding LDAP operations to complete, or explicitly
   abandon them [LDAPv3].

   After the initiator of a close has sent a TLS closure alert, it MUST
   discard any TLS messages until it has received a TLS closure alert
                  Authentication Methods for LDAPv3     July 19, 2001

   from 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) other party.  It will cease to send TLS Record Protocol
   PDUs, and following the receipt of the alert, MAY send and receive
   LDAP PDUs.

   The Internet Society (2000). All Rights Reserved.

Harrison               Expires August 20, other party, if it receives a TLS closure alert, MUST
   immediately transmit a TLS closure alert.  It will subsequently
   cease to send TLS Record Protocol PDUs, and MAY send and receive
   LDAP PDUs.

5.4.2.  Abrupt Closure

   Either the client or server MAY abruptly close the entire LDAP
   association and any TLS connection established on it by dropping the
   underlying TCP connection. In this circumstance, a server MAY send
   the client a Notice of Disconnection [LDAPv3] before dropping the
   TCP connection.

5.5.  Effects of TLS on a Client's Authorization Identity

   This section describes the effects on a client's authorization
   identity brought about by establishing TLS on an LDAP association.
   The default effects are described first, and next the facilities for
   client assertion of authorization identity are discussed including
   error conditions. Lastly, the effects of closing the TLS connection
   are described.

   Authorization identities and related concepts are described in
   Appendix B.

5.5.1.  TLS Connection Establishment Effects

5.5.1.1.  Default Effects

   Upon establishment of the TLS connection onto the LDAP association,
   any previously established authentication and authorization
   identities MUST remain in force, including anonymous state. This
   holds even in the case where the server requests client
   authentication via TLS -- e.g. requests the client to supply its
   certificate during TLS negotiation (see [TLS]).

5.5.1.2.  Client Assertion of Authorization Identity

   A client MAY either implicitly request that its LDAP authorization
   identity be derived from its authenticated TLS credentials or it MAY
   explicitly provide an authorization identity and assert that it be
   used in combination with its authenticated TLS credentials. The
   former is known as an implicit assertion, and the latter as an
   explicit assertion.

5.5.1.2.1.  Implicit Assertion

   An implicit authorization identity assertion is accomplished after
   TLS establishment by invoking a Bind request of the SASL form using
                  Authentication Methods for LDAPv3     July 19, 2001              [Page 13]

   the "EXTERNAL" mechanism name [SASL, LDAPv3] that SHALL NOT include
   the optional credentials octet string (found within the
   SaslCredentials sequence in the Bind Request). The server will
   derive the client's authorization identity from the authentication
   identity supplied in the client's TLS credentials (typically a
   public key certificate) according to local policy. The underlying
   mechanics of how this is accomplished are implementation specific.

5.5.1.2.2.  Explicit Assertion

   An explicit authorization identity assertion is accomplished after
   TLS establishment by invoking a Bind request of the SASL form using
   the "EXTERNAL" mechanism name [SASL, LDAPv3] that SHALL include the
   credentials octet string. This string MUST be constructed as
   documented in section 9 of [AuthMeth].

5.5.1.2.3.  Error Conditions

   For either form of assertion, the server MUST verify that the
   client's authentication identity as supplied in its TLS credentials
   is permitted to be mapped to the asserted authorization identity.
   The server MUST reject the Bind operation with an invalidCredentials
   resultCode in the Bind response if the client is not so authorized.

   Additionally, with either form of assertion, 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 [IPSEC]), 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.

   After the above Bind operation failures, any client authentication
   and authorization state of the LDAP association is lost, so the LDAP
   association is in an anonymous state after the failure.  TLS
   connection state is unaffected, though a server MAY end the TLS
   connection, via a TLS close_notify message, based on the Bind
   failure (as it MAY at any time).

5.5.2.  TLS Connection Closure Effects

   Closure of the TLS connection MUST cause the LDAP association to
   move to an anonymous authentication and authorization state
   regardless of the state established over TLS and regardless of the
   authentication and authorization state prior to TLS connection
   establishment.

6. 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
                  Authentication Methods for LDAPv3     July 19, 2001

   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 6.1.

   LDAP implementations MAY support anonymous authentication with TLS,
   as defined in section 6.2.

   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.

6.1. Anonymous Authentication Procedure

   An LDAPv3 client that has not successfully completed a bind
   operation on a connection is anonymously authenticated. See section
   4.3.3.

   An LDAP client MAY also choose to explicitly bind anonymously. A
   client that wishes to do so MUST choose the simple authentication
   option in the Bind Request (see section XXX) and set the password to
   be of zero length. (This is often done by LDAPv2 clients.) Typically
   the name is also of zero length.

6.2. Anonymous Authentication and TLS

   An LDAP client MAY use the Start TLS operation (section 4) to
   negotiate the use of TLS security [TLS]. 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.

7. Password-based authentication

7.1. 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 Methods for LDAPv3     July 19, 2001

   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.

7.2. Digest Authentication

   LDAP implementations MUST support authentication with a password
   using the DIGEST-MD5 SASL mechanism for password protection.

   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 perfCorming
   an "initial authentication" as defined in section 2.1 of [RFC2831],
   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.

   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 [RFC2831]. 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
   [RFC2831]. 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.

7.3. "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.

                  Authentication Methods for LDAPv3     July 19, 2001

   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.

7.3.1 "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.

7.4. Other authentication choices with TLS

   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.

8. Certificate-based authentication

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

8.1. 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 userĘs 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.

                  Authentication Methods for LDAPv3     July 19, 2001

   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.

9. 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
         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
                  Authentication Methods for LDAPv3     July 19, 2001

   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.

10. 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.

10.1.  Start TLS Security Considerations

   The goals of using the TLS protocol with LDAP are to ensure
   connection confidentiality and integrity, and to optionally provide
   for authentication. TLS expressly provides these capabilities, as
   described in [TLS].

   All security gained via use of the Start TLS operation is gained by
   the use of TLS itself. The Start TLS operation, on its own, does not
   provide any additional security.

   The use of TLS does not provide or ensure for confidentiality and/or
   non-repudiation of the data housed by an LDAP-based directory
   server. Nor does it secure the data from inspection by the server
   administrators.  Once established, TLS only provides for and ensures
   confidentiality and integrity of the operations and data in transit
   over the LDAP association, and only if the implementations on the
   client and server support and negotiate it.

   The level of security provided though the use of TLS depends
   directly on both the quality of the TLS implementation used and the
   style of usage of that implementation. Additionally, an active-
                  Authentication Methods for LDAPv3     July 19, 2001

   intermediary attacker can remove the Start TLS extended operation
   from the supportedExtension attribute of the root DSE. Therefore,
   both parties SHOULD independently ascertain and consent to the
   security level achieved once TLS is established and before beginning
   use of the TLS connection. For example, the security level of the
   TLS connection might have been negotiated down to plaintext.

   Clients SHOULD either warn the user when the security level achieved
   does not provide confidentiality and/or integrity protection, or be
   configurable to refuse to proceed without an acceptable level of
   security.

   Client and server implementors SHOULD take measures to ensure proper
   protection of credentials and other confidential data where such
   measures are not otherwise provided by the TLS implementation.

   Server implementors SHOULD allow for server administrators to elect
   whether and when connection confidentiality and/or integrity is
   required, as well as elect whether and when client authentication
   via TLS is required.
   Additional security considerations relating to the EXTERNAL
   mechanism to negotiate TLS can be found in [SASL] and [6].

11. Acknowledgements

   This document combines information originally contained in RFC 2829,
   RFC 2830 and portions of RFC 2251. The author acknowledges the work
   of Harald Tveit Alvestrand, Jeff Hodges, Tim Howes, Steve Kille, RL
   "Bob" Morgan , and Mark Wahl, each of whom authored one or more of
   these documents. RFC 2829 and RFC 2830 were products of the IETF
   LDAPEXT Working Group. RFC 2251 was a product of the ASID Working
   Group.

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

12. Bibliography

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

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

   [LDAPv3] Wahl, M., Kille S. and T. Howes, "Lightweight Directory
       Access Protocol (v3)", RFC 2251, December 1997.

   [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
       Internet Protocol", RFC 2401, November 1998.

   [RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a
       SASL Mechanism", RFC 2831, May 2000.

                  Authentication Methods for LDAPv3     July 19, 2001

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

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

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

13. Author's Address

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

14. Full Copyright Statement

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

   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
   document itself may not be modified in any way, such as by removing
   the copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the purpose of
   developing Internet standards in which case the procedures for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.

   The limited permissions granted above are perpetual and will not be
   revoked by the Internet Society or its successors or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.

Appendix A. 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
                  Authentication Methods for LDAPv3     July 19, 2001

   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.

Appendix B. Authentication and Authorization: Definitions and Concepts

   This appendix 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.

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

B.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
   [LDAPv3]). 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,
                  Authentication Methods for LDAPv3     July 19, 2001

   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.

B.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.

B.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 [SASL]. Also,
   the form of authentication identity supplied by a service like TLS
   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.

Appendix C. RFC 2829 Change History

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

                  Authentication Methods for LDAPv3     July 19, 2001

C.0. General Editorial Changes
   Version -00

     - 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.

     - Miscellaneous grammatical changes to improve readability.

     - Made capitalization in section headings consistent.

   Version -01

     - Changed title to reflect inclusion of material from RFC 2830 and
       2251.

C.1. Changes to Section 1

   Version -01

     - Moved conventions used in document to a separate section.

C.2. Changes to Section 2

   Version -01

     - Moved section to an appendix.

C.3. Changes to Section 3

   Version -01

     - Moved section to an appendix.

C.4 Changes to Section 4

   Version -00

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

C.5. Changes to Section 5

   Version -00

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

C.5.1. Changes to Section 5.1

   Version -00
                  Authentication Methods for LDAPv3     July 19, 2001

     - 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).

   Version -01

     - Brought text describing procedure for performing an anonymous
       bind from section 4.2 of RFC 2251 bis.  This text will be
       removed from the draft standard version of that document.

C.6. Changes to Section 6.

   Version -00

     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 passwordą")
       to section on Digest Authentication (Now section 6.2).

C.6.1. Changes to Section 6.1.

   Version -00 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

C.6.2 Changes to Section 6.2

   Version -00

     - 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.

                  Authentication Methods for LDAPv3     July 19, 2001

     - 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."

C.6.3. Changes to section 6.3.

     Version -00

     - Renamed to section 6.4.

C.7. Changes to section 7.

   none

C.7.1. Changes to section 7.1.

   Version -00

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

C.8. Changes to section 8.

   Version -00

     - 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.

   Version -01

     - Moved entire section 8 of RFC 2829 into section 3.4 (Using SASL
       for Other Security Services) to bring material on SASL
       mechanisms together into one location.

C.9. Changes to section 9.

   Version -00

     - Paragraph 2: changed "EXTERNAL mechanism" to "EXTERNAL SASL
       mechanism."
                  Authentication Methods for LDAPv3 February 20,     July 19, 2001

   This document and translations

     - 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 may be copied and furnished is
       redundant.

     - Added section 9.1.1. heading.

     - Added section 9.1.2. heading.

   Version -01

     - Moved entire section 9 to
   others, and derivative works become section 3.5 so that comment on or otherwise explain it
   or assist in its implementation may would be prepared, copied, published
   and distributed, in whole or
       with other SASL material.

C.10. Changes to Section 10.

   Version -00

     - Updated reference to cracking from a week of CPU time in part, without restriction 1997 to
       be a day of any
   kind, provided that the above copyright notice and this paragraph CPU time in 2000.

     - Added text: "These ciphersuites are included on all such copies NOT RECOMMENDED for use...
       and derivative works. However, this
   document itself may not be modified in any way, such as by removing server implementers SHOULD" to sentence just prior the copyright notice
       second list of ciphersuites.

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

C.11. Changes to Section 11.

   Version -01

     - Moved to section 3.6 to be with other SASL material.

C.12. Changes to Section 12.

   Version -00

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

   Version -01

     - Moved to the Internet Society or section 3.7 to be with other
   Internet organizations, except as needed SASL material.

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

                  Authentication Methods for LDAPv3     July 19, 2001

   None

Appendix D. RFC 2830 Change History

   This appendix lists the purpose changes made to the text of
   developing Internet standards RFC 2830 in which case
   preparing this document.

D.0. General Editorial Changes

     - Material showing the procedures PDUs for
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it Start TLS response was broken
       out into languages other than
   English. a new section.

     - The limited permissions granted above are perpetual wording of the definition of the Start TLS request and will not be
   revoked by Start
       TLS response was changed to make them parallel. NO changes were
       made to the Internet Society or its successors ASN.1 definition or assigns.

   This document and the information contained herein is provided on an
   "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
   TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
   BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
   HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
   MERCHANTABILITY OR FITNESS FOR associated values of the
       parameters.

     - A PARTICULAR PURPOSE. separate section heading for graceful TLS closure was added
       for parallelism with section on abrupt TLS closure.

Appendix A - E. RFC 2251 Change History

   This appendix lists the changes made to the text of text of RFC 2251 in
   preparing this document.

E.0. General Editorial Changes

     - All material from section 4.2 of RFC 2251 was moved into this
       document.

     - A new section was created for the Bind Request

     - Section 4.2.1 of RFC 2251 (Sequencing Bind Request) was moved
       after the section on the Bind Response for parallelism with the
       presentation of the Start TLS operations. The section was also
       subdivided to explicitly call out the various effects being
       described within it.

     - All SASL profile information from RFC 2829 in
   preparing this document.

A.0. General Editorial Changes

   Changed title: LDAP to LDAPv3

   Changed other instances of was brought within
       the term LDAP to LDAPv3 where v3 discussion of the
   protocol is implied. Also made all references to LDAPv3 use the same
   wording.
   Made a small number of grammatical changes Bind operation (primarily sections 4.4 -
       4.7).

Appendix F. Issues to improve readability.

   Made capitalization in section headings consistent.

A.1. Changes be Resolved

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

F.1.

   Section 1

   None

A.2. Changes to Section 2

   None

A.3. Changes to Section 3

   None

A.4 Changes to Section 4

Harrison               Expires August 20, 2001              [Page 14] lists 6 security mechanisms that can be used by LDAP
   servers. I'm not sure what mechanism 5, "Resource limitation by
   means of administrative limits on service controls" means.

                  Authentication Methods for LDAPv3 February 20,     July 19, 2001

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

A.5. Changes to

F.2.

   Section 5

   Added 2 paragraph 1 defines the following sentence: "Servers SHOULD NOT allow clients with
   anonymous authentication term, "sensitive." Do we want to modify directory entries or access
   sensitive information
   bring this term and other security-related terms in directory entries."

A.5.1. Changes to Section 5.1

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

A.6. Changes to
   usage with the IETF security glossary (RFC 2828)?

F.3.

   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 2, deployment scenario 2: What is meant by the paragraph indicating:

        a. simple term "secure
   authentication function?"

F.4.

   Section 3, deployment scenario 3: What is not suitable for environments where
        confidentiality meant by the phrase,
   "directory data is not available.

        b. LDAP implementations SHOULD NOT support simple authenticated by the server?"

F.5.

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

F.6.

   Section 4 paragraph 7 begins: "For a directory needing session
   protection..."  Is this referring to data confidentiality and or data
   integrity
        mechanisms are in force.

   2. Moved first or both?

F.7.

   Section 4 paragraph of section 6 (beginning with "LDAP
   implementations MUST support authentication with a passwordą") to
   section on Digest Authentication (Now section 6.2).
A.6.1. Changes 8 indicates that "information about the server
   fetched fetched prior to Section 6.1.

   Renamed section the TLS negotiation" must be discarded. Do
   we want to 6.2

   Added sentence from original section 6 indicating explicitly state that this applies to information fetched
   prior to the DIGEST-
   MD5 SASL mechanism *completion* of the TLS negotiation or is required for all conforming LDAPv3
   implementations

A.6.2 Changes to this going
   too far?

F.8.

   Section 6.2

   Renamed section to 6.3

   Reworded first 4 paragraph 9 indicates that clients SHOULD check the
   supportedSASLMechanisms list both before and after a SASL security
   layer is negotiated to remove reference to user ensure that they are using the best available
   security mechanism supported mutually by the client and server. A
   note at the
   userPassword password attribute Made 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 first paragraph intent of this could be restated more
   general by simply saying that if a directory supports simple
   authentication that plainly using
   one of these two approaches (I've paraphrased for the simple bind operation MAY performed
   following negotiation sake of
   brevity):

   Approach 1: Clients SHOULD check the supportedSASLMechanisms list
   both before and after SASL negotiation or clients SHOULD use a TLS ciphersuite that supports
   confidentiality.

Harrison               Expires August 20, 2001              [Page 15]
                  Authentication Methods for LDAPv3 February 20,     July 19, 2001

   Replaced "the name of

   different trusted source to determine available supported SASL
   mechanisms.

   Approach 2: Clients MUST check the user's entry" with "a DN" since not all
   bind operations are performed on behalf of supportedSASLMechanisms list both
   before and after SASL negotiation UNLESS they use a "user."

   Added different
   trusted source to determine available supported SASL mechanisms.

F.9.

   Section 6.3.1 heading just prior to paragraph 5.

   Paragraph 5: replaced "The server" with states: "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 attribute will... compare
   [each value in the certificate" immediately after "Certification
   Authority."

A.8. Changes to section 8.

   Removed named user's entry]... with 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" presented
   password."  This implies that this this applies only to "EXTERNAL SASL
   mechanism."

   Added section 9.1. heading.

   Modified a comment user entries
   with userPassword attributes.  What about other types of entries
   that might allow passwords and might store in the ABNF from "unspecified userid" password
   information in other attributes?  Do we want to
   "unspecified authz id".

   Deleted sentence, "A utf8string is defined make this text more
   general?

F.10 userPassword and simple bind

   We need 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 sure that we don't require userPassword to Section 10.

Harrison               Expires August 20, 2001              [Page 16]
                  Authentication Methods be the only
   attribute used for LDAPv3 February 20, 2001

   Updated reference authenticating via simple bind. (See 2251 sec 4.2
   and authmeth 6.3.1. Work with Jim Sermersheim on resolution to cracking from a week this.
   On publication state something like: "This is the specific
   implementation of CPU time what we discussed in 1997 to be
   a day our general reorg
   conversation on the list." (Source: Kurt Zeilenga)

F.11 Meaning of CPU time LDAP Association

   The original RFC 2830 uses the term "LDAP association" in 2000.

   Added text: "These ciphersuites are NOT RECOMMENDED for use... describing
   a connection between an LDAP client and server implementers SHOULD" to sentence just prior the second list regardless of ciphersuites.

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

A.11. Changes to Section 11.

   None

A.12. Changes to Section 12.

   Inserted new section 12 TLS on that specifies when SASL protections begin connection. This term needs to be defined or
   possibly changed.

F.12. Is DIGEST-MD5 mandatory for all implementations?

   Reading 2829bis I think DIGEST-MD5 is mandatory ONLY IF your server
   supports password based authentication...but the following makes it
   sound mandatory to provide BOTH password authentication AND DIGEST-
   MD5:

   "6.2. Digest authentication

   LDAP implementations MUST support authentication with a password
   using the DIGEST-MD5 SASL negotiation, etc.. The original mechanism for password protection, as
   defined in section 12 6.1."

   The thing is
   renumbered to become section 13.

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

   None

Appendix B Issues to for acl it would be Resolved

   This appendix lists open questions and issues that need nice (though not critical) to be
   resolved before work on this document
   able to default the required authentication level for a subject to a
   single "fairly secure" mechanism--if there 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 no such mandatory
   authentication scheme then you cannot do that. (Source: Rob Byrne)
                  Authentication Methods for LDAPv3     July 19, 2001

F.13. Ordering of administrative limits authentication levels requested

   Again on service controls" means.

B.2.

   Section 2 paragraph 1 defines the term, "sensitive." Do we want subject of authentication level, is it possible to
   bring
   define an ordering on authentication levels which defines their
   relative "strengths" ? This would be useful in acl as you could say
   things like"a given aci grants access to a given subject at this term and other security-related terms
   authentication level AND ABOVE". David Chadwick raised this before
   in alignment with
   usage with the IETF context of denying access to a subject at a given
   authentication level, in which case he wanted to express "deny
   access to this subject at this authentication level AND TO ALL
   IDENTITIES AUTHENTICATED BELOW THAT LEVEL". (Source: Rob Byrne)

F.14. Document vulnerabilities of various mechanisms

   While I'm here...in 2829, I think it would be good to have some
   comments or explicit reference to a place where the security glossary (RFC 2828)?

B.3.

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

B.4.

   Section 3, deployment scenario 3: What is meant by the phrase,
   "directory data schemes are
   outlined. When I say "security properties" I mean stuff like "This
   scheme is authenticated by the server?"

B.5.

Harrison               Expires August 20, 2001              [Page 17]
                  Authentication Methods for LDAPv3 February 20, 2001

   Section 4 paragraph 3: What vulnerable to such and such attacks, is meatn by only safe if the phrase, "this means that
   either
   key size is > 50, this data hash is useless for faking authentication (like widely considered 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 best, etc...".
   I think an LDAP implementor is likely to data confidentiality or data
   integrity or both?

B.7.

   Section 4 paragraph 8 indicates be interested in that "information about the server
   fetched fetched prior
   information, without having to wade through the TLS negotiation" security RFCs.
   (Source: Rob Byrne)

F.15. Include a StartTLS state transition table

   The pictoral representation it is nominally based on is here (URL
   possibly folded):

   http://www.stanford.edu/~hodges/doc/LDAPAssociationStateDiagram-
   1999-12-14.html

   (Source: Jeff Hodges)

F.16. Empty sasl credentials question

   I spent some more time looking microscopically at ldap-auth-methods
   and ldap-ext-tls drafts. The drafts say that the credential must
   have the form dn:xxx or u:xxx or be discarded. Do
   we want absent, and although they don't
   say what to explicitly state do in the case of an empty octet string I would say that this applies to information fetched
   prior to
   we could send protocolError (claim it is a bad PDU).

   There is still the *completion* question of what to do if the TLS negotiation or credential is this going
   too far?

B.8.

   Section 4 paragraph 9 indicates that clients SHOULD 'dn:'
   (or 'u:') followed by the empty string. (Source: ariel@columbia.edu
   via Jeff Hodges)

F.17. Hostname check from MUST to SHOULD?

   I am uneasy about the
   supportedSASLMechanisms list both before and after a SASL security
   layer hostname check. My experience from PKI with
   HTTP probably is negotiated to ensure that they are a contributing factor; we have people using the best available
   security mechanism supported mutually by
   short hostname to get to a server which naturally has the client FQDN in
   the certificate, no end of problems. I have a certificate on my
   laptop which has the FQDN for the casse when the system is on our
                  Authentication Methods for LDAPv3     July 19, 2001

   Columbia network with a fixed IP; when I dial in however, I have
   some horrible dialup name, and server. A
   note at using the local https server becomes
   annoying. Issuing a certificate in the name 'localhost' is not a
   solution! Wildcard match does not solve this problem. For these
   reasons I am inclined to argue for 'SHOULD' instead of
   'MUST' in paragraph...

   Also, The hostname check against the end of name in the paragraph indicates that this certificate is a SHOULD
   since there are environments where
   very weak means of preventing man-in-the-middle attacks; the client might get a list proper
   solution is not here yet (SecureDNS or some equivalent). Faking out
   DNS is not so hard, and we see this sort of
   supported SASL mechanisms from thing in the press on a different trusted source.

   I wonder if
   pretty regular basis, where site A hijacks the intent DNS server for site B
   and gets all their requests. Some mention of this could should be restated more plainly using
   one of these two approaches (I've paraphrased for made in
   the sake draft. (Source: ariel@columbia.edu via Jeff Hodges)

F.18. Must SASL DN exist in the directory?

   If the 'dn:' form of
   brevity):

   Approach 1: Clients SHOULD check sasl creds is used, is it 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 intention of 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
   draft(ers) that map the this DN sent must exist in the bind request
   to a directory entry with a userPassword attribute will... compare
   [each value in and the named user's entry]... with client
   will have the presented
   password."  This implies privileges associated with that this this applies only entry, or can the
   server map the sasl DN to user entries
   with userPassword attributes.  What about perhaps some other types of entries DN in the directory,
   in an implementation-dependent fashion?

   We already know that might allow passwords and might store if *no* sasl credentials are presented, the DN
   or altname in the password
   information client certificate may be mapped to a DN in other attributes?  Do we want an
   implementation-dependent fashion, or indeed to make this text more
   general?

Harrison               Expires August 20, 2001              [Page 18] something not in the
   directory at all. (Right?)  (Source: ariel@columbia.edu via Jeff
   Hodges)