INTERNET-DRAFT                                      Editor: R. Harrison
draft-ietf-ldapbis-authmeth-08.txt
draft-ietf-ldapbis-authmeth-09.txt                         Novell, Inc.
Obsoletes: 2251, 2829, 2830                             26 October                             5 December 2003
Intended Category: Draft Standard

                      LDAP: Authentication Methods
                                  and
                  Connection Level Security Mechanisms

Status of this Memo

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

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

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Copyright Notice

   Copyright (C) The Internet Society (2003).  All Rights Reserved.

Abstract

   This document describes authentication methods and connection level
   security mechanisms of the Lightweight Directory Access Protocol
   (LDAP).

   This document details the simple Bind authentication method
   including anonymous, unauthenticated, and plain-text password
   methods and the SASL (Simple Authentication and Security Layer) Bind
   authentication method including the use of DIGEST-MD5 and EXTERNAL
   mechanisms.

   This document also details establishment of TLS (Transport Layer
   Security) using the Start TLS operation.

   This document describes various authentication and authorization
   states through which a connection to an LDAP server may pass and the
   actions that trigger these state changes.

   This document also prescribes DIGEST-MD5 as LDAP's mandatory-to-
   implement strong authentication mechanism.

1. Introduction

   The Lightweight Directory Access Protocol (LDAP) [Protocol] is a
   powerful access protocol for directories. It offers means of
   searching, retrieving and manipulating directory content, and ways
   to access a rich set of security functions.

   It is vital that these security functions be 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 LDAP conformance.

   Basic threats to an LDAP directory service include:

   (1) Unauthorized access to directory data via data-retrieval
       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 information,

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

   (7) Spoofing of directory: Tricking a client into believing that
       information came from the directory when in fact it did not,
       either by modifying data in transit or misdirecting the client's
       connection. Also, tricking a client into sending privileged
       information to a hostile entity that appears to be the directory
       but is not.

   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 hostile agents posing as a server.

   LDAP can be protected with the following security mechanisms:

   (1) Client authentication by means of the Secure Authentication and
       Security Layer (SASL) [SASL] mechanism set, possibly backed by
       the Transport Layer Security (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 TLS or SASL mechanisms
       with security layers that provide data integrity services,

   (4) Data confidentiality protection against snooping by means of the
       TLS protocol or SASL mechanisms that provide data
       confidentiality services,

   (5) Server resource usage limitation by means of administrative
       service limits configured on the server, 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 LDAP.

   It seems clear that allowing any implementation, faced with the
   above requirements, to simply pick and choose among the possible
   alternatives is not a strategy that is likely to lead to
   interoperability. In the absence of mandates, clients will be
   written that do not support any security function supported by the
   server, or worse, they will support only mechanisms like the LDAP
   simple bind using clear text passwords that provide inadequate
   security for most circumstances.

   Given the presence of the Directory, there is a strong desire to see
   mechanisms where identities take the form of an LDAP distinguished
   name [LDAPDN] and authentication data can be stored in the
   directory. This means that this data must be updated outside the
   protocol or only updated in sessions well protected against
   snooping. It is also desirable to allow authentication methods to
   carry authorization identities based on existing--non-LDAP DN--forms
   of not represented as LDAP DNs that are familiar to
   the user identities for backwards compatibility with non-LDAP-based
   authentication services. or that are used in other systems.

     The set of security mechanisms provided in LDAP and described in
     this document is intended to meet the security needs for a wide
     range of deployment scenarios and still provide a high degree of
     interoperability among various LDAP implementations and
     deployments. Appendix A contains example deployment scenarios that
     list the mechanisms that might be used to achieve a reasonable
     level of security in various circumstances.

1.1. Relationship to Other Documents

   This document is an integral part of the LDAP Technical
   Specification [Roadmap].

   This document replaces obsoletes RFC 2829 2829.

   Sections 2 and
   portions 4 of RFC 2830 and are obsoleted by [Protocol].  The
   remainder of RFC 2251. 2830 is obsoleted by this document.

2. Conventions Used in this Document

2.1. Glossary of Terms

   The following terms are used in this document. To aid the reader,
   these terms are defined here.

     - "user" represents any human or application entity which is
       accessing the directory using a directory client.  A directory
       client (or client) is also known as a directory user agent
       (DUA).

     - "connection" and "LDAP connection" both refer to the underlying
       transport protocol connection between two protocol peers.

     - "TLS connection" refers to a TLS-protected LDAP connection.

     - "association" and "LDAP association" both refer to the
       association of the LDAP connection and its current
       authentication and authorization state.

2.2. Security Terms and Concepts

   In general, security terms in this document are used consistently
   with the definitions provided in [RFC2828]. In addition, several
   terms and concepts relating to security, authentication, and
   authorization are presented in Appendix B of this document. While
   the formal 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.

2.3. Keywords

   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 [RFC2119].

3. Bind Operation

   The Bind operation defined in section 4.2 of [Protocol] allows
   authentication information to be exchanged between the client and
   server to establish a new LDAP association. The new LDAP association
   is established upon successful completion of the authentication
   exchange.

3.1. Implied Anonymous Bind on LDAP Association

   Prior to the successful completion of a Bind operation and during
   any subsequent authentication exchange, the session has an anonymous
   LDAP association. Among other things this implies that the client
   need not send a Bind Request in the first PDU of the connection. The
   client may send any operation request prior to binding, and the
   server MUST treat it as if it had been performed after an anonymous
   bind operation. This authentication state on an LDAP association is
   sometimes referred to as an implied anonymous bind.

3.2. Simple Authentication

   The simple authentication choice provides minimal facilities for
   establishing an anonymous association or for establishing an LDAP
   association based upon credentials consisting of a name (in the form
   of an [LDAPDN] and a password.

   The simple authentication choice provides two different methods
   for establishing an anonymous association: anonymous bind and
   unauthenticated bind (see section 6.1). 5.1).

   The simple authentication choice provides one method for
   establishing a non-anonymous association: simple password bind.

3.3. SASL Authentication Profile

   LDAP allows authentication via any SASL mechanism [SASL]. As LDAP
   includes native anonymous and plaintext authentication methods, the
   "ANONYMOUS"
   ANONYMOUS [ANONYMOUS] and "PLAIN" PLAIN [PLAIN] SASL mechanisms are
   typically not used with LDAP.

   Each protocol that utilizes SASL services is required to supply
   certain information profiling the way they are exposed through the
   protocol ([SASL] section 5). This section explains how each of these
   profiling requirements are met by LDAP.

3.3.1. SASL Service Name for LDAP

   The SASL service name for LDAP is "ldap", which has been registered
   with the IANA as a GSSAPI service name.

3.3.2. SASL authentication initiation and protocol exchange

   SASL authentication is initiated via an LDAP bind request
   ([Protocol] section 4.2) with the following parameters:

      - The version is 3.
      - The AuthenticationChoice is sasl.
      - The mechanism element of the SaslCredentials sequence contains
        the value of the desired SASL mechanism.
      - The optional credentials field of the SaslCredentials sequence
        may be used to provide an initial client response for
        mechanisms that are defined to have the client send data first
        (see [SASL] sections 5 and 6.1). 5.1).

   In general, a SASL authentication protocol exchange consists of a
   series of server challenges and client responses, the contents of
   which are specific to and defined by the SASL mechanism. Thus for
   some SASL authentication mechanisms, it may be necessary for the
   client to respond to one or more server challenges by invoking the
   BindRequest multiple times. A challenge is indicated by the server
   sending a BindResponse with the resultCode set to
   saslBindInProgress. This indicates that the server requires the
   client to send a new bind request, with the same sasl mechanism to
   continue the authentication process.

   To the encapsulating protocol, these challenges and responses are
   opaque binary tokens of arbitrary length. LDAP servers use the
   serverSaslCreds field, an OCTET STRING, in a bind response message
   to transmit each challenge. LDAP clients use the credentials field,
   an OCTET STRING, in the SaslCredentials sequence of a bind request
   message to transmit each response. Note that unlike some Internet
   application
   protocols where SASL is used, LDAP is not text-based, thus no Base64
   transformations are performed on these challenge and response
   values.

   Clients sending a bind request with the sasl choice selected SHOULD
   NOT send a value in the name field. Servers receiving a bind request
   with the sasl choice selected SHALL ignore any value in the name
   field.

   A client may abort a SASL bind negotiation by sending a BindRequest
   with a different value in the mechanism field of SaslCredentials, or
   an AuthenticationChoice other than sasl.

   If the client sends a BindRequest with the sasl mechanism field as
   an empty string, the server MUST return a BindResponse with
   authMethodNotSupported as the resultCode. This will allow clients to
   abort a negotiation if it wishes to try again with the same SASL
   mechanism.

   The server indicates completion of the SASL challenge-response
   exchange by responding with a bind response in which the resultCode
   is either success, or an error indication.

   The serverSaslCreds field in the bind response can be used to
   include an optional challenge with a success notification for
   mechanisms which are defined to have the server send additional data
   along with the indication of successful completion.

3.3.3. Octet where negotiated security mechanisms take effect

   When negotiated, SASL security layers take effect following the
   transmission by the server and reception by the client of the final
   BindResponse in the exchange.

   Once a SASL security layer providing integrity or confidentiality
   services takes effect, the layer remains in effect until a new layer
   is installed (i.e. at the first octet following the final
   BindResponse of the bind operation that caused the new layer to take
   effect).

3.3.4. Determination of supported SASL mechanisms

   An LDAP client may determine the SASL mechanisms a server supports
   by performing a search request on the root DSE, requesting the
   supportedSASLMechanisms attribute. The values of this attribute, if
   any, list the mechanisms the server supports.

3.3.5. Rules for using SASL security layers

   If a SASL security layer is negotiated, the client SHOULD discard
   information about the server fetched it obtained prior to the initiation of
   the SASL negotiation and not obtained through secure mechanisms.

   If the client is configured to support multiple SASL mechanisms, it
   SHOULD fetch the supportedSASLmechanisms list both before and after
   the SASL security layer is negotiated. This allows the client to
   detect active attacks that remove supported SASL mechanisms from the
   supportedSASLMechanisms list and allows the client to ensure that it
   is using the best mechanism supported by both client and server. (In
   particular, this allows for environments where the
   supportedSASLMechanisms list is provided to the client through a
   different trusted source, e.g. as part of a digitally signed
   object.)

   If a lower level security layer (such as TLS) is negotiated, any
   SASL security services SHALL be layered on top of such security
   layers regardless of the order of their negotiation. In all other
   respects, SASL security services and other security layers act
   independently, e.g. if both TLS and SASL security service are in
   effect removing the SASL security service does not affect the
   continuing service of TLS and vice versa.

   Because SASL mechanisms provide critical security functions, clients
   and servers should allow the user to specify what mechanisms are
   acceptable and allow only those mechanisms to be used.

3.3.6. Use of EXTERNAL SASL Mechanism

   A client can use the "EXTERNAL" EXTERNAL SASL [SASL] mechanism to request the
   LDAP server to make use of security credentials exchanged by a lower
   layer.
   security layer (such as by TLS authentication or IP-level security
   [RFC2401]).

   If the client's authentication credentials have not been established
   at a lower level (such as by TLS authentication or IP-level security
   [RFC2401]), layer, the SASL EXTERNAL bind MUST fail with a
   resultCode of inappropriateAuthentication.  Any client
   authentication and authorization state of the LDAP association is
   lost, so the LDAP association is in an anonymous state after the
   failure (see [Protocol] section 4.2.1).

3.4. SASL Authorization Identity

   When In such a situation, the "EXTERNAL" SASL mechanism
   state of any established security layer is being negotiated, if the
   SaslCredentials credentials unaffected.

   A client may either implicitly request that its LDAP authorization
   identity be derived from a lower layer 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.

3.3.6.1. Implicit Assertion

   An implicit authorization identity assertion is performed by
   invoking a Bind request of the SASL form using the EXTERNAL
   mechanism name 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 by the security layer
   (e.g., a public key certificate used during TLS establishment)
   according to local policy. The underlying mechanics of how this is
   accomplished are implementation specific.

3.3.6.2. Explicit Assertion

   An explicit authorization identity assertion is performed by
   invoking a Bind request of the SASL form using the EXTERNAL
   mechanism name that SHALL include the credentials octet string. This
   string MUST be constructed as documented in section 3.4.1.

   The server MUST 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.

3.3.6.3. SASL Authorization Identity

   When the EXTERNAL SASL mechanism is being negotiated, if the
   SaslCredentials credentials field is present, it contains an
   authorization identity. Other mechanisms define the location of the
   authorization identity in the credentials field. In either case, the
   authorization identity is represented in the authzId form described
   below.

3.4.1.

3.3.6.4 Authorization Identity Syntax

   The authorization identity is a string of [UTF-8] encoded [Unicode]
   characters corresponding to the following ABNF grammar [RFC2234]:

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

   authzId = dnAuthzId / uAuthzId

   DNCOLON  = %x64 %x6e %x3a ; "dn:"
   UCOLON = %x75 %x3a ; "u:"

   ; distinguished-name-based authz id.
   dnAuthzId = DNCOLON dn
   dn = utf8string    ; with syntax defined in [LDAPDN] section 3. distinguishedName

   ; unspecified authorization id, UTF-8 encoded.
   uAuthzId = UCOLON userid
   userid = utf8string *UTF8    ; syntax unspecified

   where the <distinguishedName> production is defined in section 3 of
   [LDAPDN] and <UTF8> production is defined in section 1.3 of
   [Models].

   In order to support additional specific authorization identity
   forms, future updates to this specification may add new choices
   supporting other forms may be added to the authzId production.

   The dnAuthzId choice allows client applications clients to assert authorization
   identities in the form of a distinguished name to be matched in
   accordance with the distinguishedName matching rule [Syntaxes]. The
   decision to allow or disallow an authentication identity to have
   access to the requested authorization identity is a matter of local
   policy ([SASL] section 4.2). For this reason there is no requirement
   that the asserted dn be that of an entry in directory.

   The uAuthzId choice allows for compatibility with client
   applications clients that wish
   to assert an authorization identity to a local directory but do not
   have that identity in distinguished name form. The value contained
   within a uAuthzId MUST be prepared using
   SASLprep [SASLPrep] before being
   compared octet-wise. The format of utf8string is defined as only a
   sequence of of [UTF-8] encoded [Unicode] characters, and further
   interpretation is subject to prior agreement between the client and
   server.

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

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

4. Start TLS Operation

   The Start Transport Layer Security (StartTLS) (Start TLS) operation defined in
   section 4.13 of [Protocol] provides the ability to establish [TLS]
   on an LDAP association.

4.1. Sequencing of the Start TLS Operation

   This section describes the overall procedures clients and servers
   must follow for TLS establishment. These procedures take into
   consideration various aspects of the overall security of the LDAP
   association including discovery of resultant security level and
   assertion of the client's authorization identity.

   Note that the precise effects, on a client's authorization identity,
   of establishing TLS on an LDAP association are described in detail
   in section 4.2.

4.1.1. Requesting to Start TLS on an LDAP Connection Request

   The client MAY send the Start TLS extended request at any time after
   establishing an LDAP connection, except:

      - when TLS is currently established on the connection,
      - when a multi-stage SASL negotiation is in progress on the
        connection, or
      - when there are one or more outstanding LDAP operations on the
        connection.

   The result of violating any of these requirements is a resultCode of
   operationsError, as described in [Protocol] section 4.13.2.2. Client
   implementers should note that it is possible to receive a resultCode
   of success for a Start TLS operation that is sent on a connection
   with outstanding LDAP operations and the server has sufficient time
   to process them prior to its receiving the Start TLS request.
   Implementors of clients should ensure that they do not inadvertently
   depend upon this race condition for proper functioning of their
   applications. condition.

   In particular, there is no requirement that the client have or have
   not already performed a Bind operation before sending a Start TLS
   operation request. The client may have already performed a Bind
   operation when it sends a Start TLS request, or the client might
   have not yet bound.

   If the client did not establish a TLS connection before sending any
   other requests, and the server requires the client to establish a
   TLS connection before performing a particular request, the server
   MUST reject that request by sending a resultCode of
   confidentialityRequired or strongAuthRequired.

4.1.2. Starting Start TLS Response

   The server will return an extended response with the resultCode of
   success if it is willing and able to negotiate TLS.  It will return
   other resultCodes resultCode values (documented in [Protocol] section 4.13.2.2)
   if it is unwilling or unable to do so.

   In the successful case, the client (which has ceased to transfer
   LDAP requests on the connection) MUST either begin a TLS negotiation
   or close the connection. The client will send PDUs in the TLS Record
   Protocol directly over the underlying transport connection to the
   server to initiate [TLS] negotiation.

4.1.3. TLS Version Negotiation

   Negotiating the version of TLS or SSL to be used is a part of the
   [TLS] Handshake Protocol. Please refer to that document for details.

4.1.4. Discovery of Resultant Security Level

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

   If the client or server decides that the level of authentication or
   security is not high enough for it to continue, it SHOULD gracefully
   close the TLS connection immediately after the TLS negotiation has
   completed (see [Protocol] section 4.13.3.1 and section 4.2.3 below).
   If the client decides to continue, it may gracefully close the TLS
   connection and attempt to Start TLS again, it may send an unbind
   request, or it may send any other LDAP request.

4.1.5. Server Identity Check
   The client MUST check its understanding of the 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 performed according to these rules:

     - The client MUST use the server provided by the user (or other
       trusted entity) as the value to compare against the server name
       as expressed in the server's certificate. A hostname derived
       from the user input is to be considered provided by the user
       only if derived in a secure fashion (e.g., DNSSEC).

     - If a subjectAltName extension of type dNSName is present in 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.

       For example, *.bar.com would match a.bar.com and b.bar.com, but
       it would not match a.x.bar.com nor would it match bar.com.  If
       more than one identity of a 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 in making
   this determination.

4.1.6. Refresh of Server Capabilities Information

   Upon TLS session establishment, the client SHOULD discard or refresh
   all information about the server fetched it obtained prior to the initiation
   of the TLS negotiation and not obtained through secure mechanisms.
   This protects 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. In particular, the value of supportedSASLMechanisms
   may be different after TLS has been negotiated (specifically, the
   EXTERNAL and PLAIN [PLAIN] mechanisms are likely to be listed only
   after a TLS negotiation has been performed).

4.2. 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. Finally, the effects of closing the TLS connection
   are described.

   Authorization identities and related concepts are described in
   Appendix B.

4.2.1. Default Effects

   Upon establishment of the TLS session onto Connection Establishment Effects

   The decision to keep or invalidate 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 place after TLS is negotiated is a
   matter of local server requests client policy. If a server chooses to invalidate
   established authentication via and authorization identities after TLS --
   e.g. is
   negotiated, it MUST reply to subsequent valid operation requests
   until the next TLS closure or successful bind request with a
   resultCode of strongAuthRequired to indicate that the client needs
   to supply bind to reestablish its certificate during TLS
   negotiation. authentication. If the client attempts to
   bind using a method the server is unwilling to support, it responds
   to the with a resultCode of authMethodNotSupported (per [Protocol])
   to indicate that a different authentication method should be used.

4.2.2. Client Assertion of Authorization Identity

   The client MAY, upon receipt of

   After successfully establishing a Start TLS response indicating
   success, assert that session, a specific authorization identity client may request
   that its credentials exchanged during the TLS establishment be
   utilized
   in determining to determine the client's authorization status. The client
   accomplishes this via an LDAP Bind request specifying a SASL
   mechanism of "EXTERNAL" EXTERNAL [SASL]. 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 See section 3.3.6 for additional
   details.

4.2.3. TLS credentials. Connection Closure Effects

   The former is known as an
   implicit assertion, and decision to keep or invalidate the latter as an explicit assertion.

4.2.2.1. Implicit Assertion

   An implicit established authentication
   and authorization identity assertion is accomplished identities in place after TLS establishment by invoking closure is a Bind request matter
   of the SASL form using
   the "EXTERNAL" mechanism name [SASL] [Protocol] that SHALL NOT
   include the optional credentials octet string (found within the
   SaslCredentials sequence in the Bind Request). The local server will
   derive the client's authorization identity from the authentication
   identity supplied in the client's TLS credentials (typically policy. If a
   public key certificate) according server chooses to local policy. The underlying
   mechanics of how this is accomplished are implementation specific.

4.2.2.2. Explicit Assertion

   An explicit invalidate
   established authentication and authorization identity assertion is accomplished identities after TLS establishment by invoking a Bind is
   negotiated, it MUST reply to subsequent valid operation requests
   until the next TLS closure or successful bind request with a
   resultCode of strongAuthRequired to indicate that the SASL form using client needs
   to bind to reestablish its authentication. If the "EXTERNAL" mechanism name [SASL] [Protocol] that SHALL include client attempts to
   bind using a method the credentials octet string. This string MUST be constructed as
   documented in section 3.4.1.

   The server MUST verify that the client's authentication identity as
   supplied in its TLS credentials is permitted unwilling to be mapped support, it responds
   to the
   asserted authorization identity. The server MUST reject the Bind
   operation with an invalidCredentials a resultCode in the Bind response
   if the client is not so authorized.

4.2.2.3. Error Conditions

   Additionally, with either form of assertion, if authMethodNotSupported (per [Protocol])
   to indicate that a TLS session has
   not been established between the different authentication method should be used.

5. Anonymous Authentication
   Directory operations that modify entries or access protected
   attributes or entries generally require client and server prior authentication.
   Clients that do not intend to making
   the SASL EXTERNAL Bind request and there is no other external source perform any of these operations
   typically use anonymous authentication.

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

   LDAP implementations MAY support anonymous authentication credentials (e.g. IP-level security [RFC2401]), or
   if during with TLS,
   as defined in section 5.2.

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

   An LDAP server
   did not request may use other information about the client's authentication credentials, client provided
   by the SASL
   EXTERNAL bind MUST fail with lower layers or external means to grant or deny access even
   to anonymously authenticated clients.

5.1. Anonymous Authentication Procedure

   Prior to successfully completing a resultCode of
   inappropriateAuthentication.

   After the above Bind operation failures, any client authentication
   and authorization state of operation, the LDAP
   association is lost (see
   [Protocol] anonymous. See section 4.2.1), so the 3.1.

   An LDAP association is in client may also explicitly establish an anonymous state after the failure.  The TLS session state is
   unaffected, though
   association by sending a server MAY end Bind Request with the TLS session, via simple authentication
   option and a TLS
   close_notify message, based on the Bind failure (as it MAY at any
   time).

4.2.3. TLS Connection Closure Effects

   Closure password of zero length. A bind request where both the TLS session MUST cause the LDAP association to move
   name and password are of zero length is said to be an anonymous authentication and authorization state regardless of
   bind. A bind request where the state established over TLS and regardless name, a DN, is of the authentication non-zero length,
   and authorization state prior to TLS session establishment.

5. LDAP Association State Transition Tables

   To comprehensively diagram the various authentication and TLS states
   through which password is of zero length is said to be an LDAP association may pass, this unauthenticated
   bind. Both variations produce an anonymous association.

   Unauthenticated binds can have significant security issues (see
   section provides 10). Servers SHOULD by default reject unauthenticated bind
   requests with a
   state transition table resultCode of invalidCredentials, and clients may
   need to represent a state diagram for the various
   states through which actively detect situations where they would make an
   unauthenticated bind request.

5.2. Anonymous Authentication and TLS

   An LDAP association client may pass during use the course Start TLS operation (section 5) to
   negotiate the use of its existence and [TLS] security. If the actions that cause these changes in state.

5.1. LDAP Association States

   The following table lists client has not bound
   beforehand, then until the valid LDAP association states and
   provides a description client uses the EXTERNAL SASL mechanism
   to negotiate the recognition of each state. The ID for each state is used
   in the state transition table client's certificate, the client
   is anonymously authenticated.

   Recommendations on TLS ciphersuites are given in section 5.4.

   ID State Description
   -- --------------------------------------------------------------
   S1 Anonymous
       no Authentication  ID is associated with the 9.

   An LDAP connection
       no Authorization ID is in force
       No server which requests that clients provide their certificate
   during TLS negotiation MAY use a local security layer is in effect.
       No policy to determine
   whether to successfully complete TLS credentials have been provided
       TLS: no Creds, OFF]
   S2 no Auth ID
       no AuthZ ID
       [TLS: no Creds, ON]
   S3 no Auth ID
       no AuthZ ID
       [TLS: Creds Auth ID "I", ON]
   S4 Auth ID = Xn
       AuthZ ID= Y
       [TLS: no Creds, OFF]
   S5 Auth ID = Xn
       AuthZ ID= Yn
       [TLS: no Creds, ON]
   S6 Auth ID = Xn
       AuthZ ID= Yn
       [TLS: Creds Auth ID "I", ON]
   S7 Auth ID = I
       AuthZ ID= J
       [TLS: Creds Auth ID "I", ON]
   S8 Auth ID = I
       AuthZ ID= K
       [TLS: Creds Auth ID "I", ON]

5.2. Actions that Affect LDAP Association State

   The following table lists the actions that can affect negotiation if the state of
   an client did
   not present a certificate which could be validated.

6. Password-based Authentication

   This section discusses various options for performing password-based
   authentication to LDAP association. The ID compliant servers and the environments
   suitable for each action is used their use.

   The transmission of passwords in the state
   transition table in section 5.4.

   ID Action
   -- ------------------------------------------------
   A1 Client binds anonymously
   A2 Inappropriate authentication: client attempts an anonymous
       bind clear--typically for
   authentication or modification--poses a significant security risk.
   This risk can be avoided by using SASL bind without supplying credentials to [SASL] mechanisms that
   do not transmit passwords in the clear and by negotiating transport
   or session layer confidentiality services before transmitting
   password values.

   To mitigate the security risks associated with the use of passwords,
   a server implementation MUST implement a configuration that
       requires at the client to provide some form
   time of credentials.
   A3 Client Start TLS request
       Server: client auth NOT required
   A4 Client: Start TLS request
       Server: client creds requested
       Client: [TLS creds: Auth ID "I"]
   A5 Client authentication or Server: send TLS closure alert ([Protocol] section
       X)
   A6 Client: Bind w/simple password or SASL modification, requires:

     1) A Start TLS encryption layer has been successfully negotiated.

      OR

     2) Some other confidentiality mechanism (e.g. DIGEST-
       MD5 password, Kerberos, etc., except EXTERNAL [Auth ID "X"
       maps to AuthZ ID "Y"]
   A7 Client Binds SASL EXTERNAL with credentials: AuthZ ID "J"
       [Explicit Assertion (section 4.2.1.2.2)]
   A8 Client Bind SASL EXTERNAL without credentials [Implicit
       Assertion (section 4.2.1.2.1)]
   A9 Client abandons a bind operation or bind operation fails

5.3. Decisions Used in Making LDAP Association State Changes

   Certain changes in the state of an LDAP association are only allowed
   if that protects the password
        value from snooping has been provided.

      OR

     3) The server can affirmatively answer returns a question. These questions
   are applied as part resultCode of the criteria confidentialityRequired for allowing or disallowing
        the operation (i.e. simple bind with password value, SASL bind
        transmitting a
   state change password value in the state transition table in section 5.4.

   ID Decision Question
   -- --------------------------------------------------------------
   D1 Can TLS Credentials Auth ID "I" be mapped to AuthZ ID "J"?
   D2 Can clear, add or modify
        including a valid AuthZ ID "K" be derived from TLS Credentials Auth
       ID "I"?

5.4. LDAP Association State Transition Table userPassword value, etc.), even if the password
        value is correct.

6.1. Simple Authentication

   The LDAP Association table below lists the valid states "simple" authentication choice is not suitable for an LDAP
   association and the actions that could affect them. For any given
   row
   authentication in environments where there is no network or
   transport layer confidentiality. LDAP implementations SHOULD support
   authentication with the table, the Current State column gives "simple" authentication choice when the state of an
   connection is protected against eavesdropping using TLS, as defined
   in section 4. LDAP association, implementations SHOULD NOT support authentication
   with the Action column gives an action that could
   affect "simple" authentication choice unless the state of an LDAP assocation, and data on the Next State column
   gives the resulting state of an LDAP association after the action
   occurs.

   The initial state for the state machine described in this table is
   S1.

   Current                 Next
    State  Action         State Comment
   ------- -------------  ----- -----------------------------------
      S1    A1              S1
      S1    A2              S1   Error: Inappropriate authentication
      S1    A3              S2
      S1    A4              S3
      S1    A6              S4
      S1    A7               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S1    A8               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S2    A1              S2
      S2    A2              S2   Error: Inappropriate authentication
      S2    A5              S1
      S2    A6              S5
      S2    A7               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S2    A8               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S3    A1              S3
      S3    A2              S3   Error: Inappropriate authentication
      S3    A5              S1
      S3    A6              S6
      S3    A7 and D1=NO    S3   Error: InvalidCredentials
      S3    A7 and D1=YES   S7
      S3    A8 and D2=NO    S3   Error: InvalidCredentials
      S3    A8 and D2=YES   S8
      S4    A1              S1
      S4    A2              S1   Error: Inappropriate Authentication
      S4    A3              S5
      S4    A4              S6
      S4    A5              S1
      S4    A6              S4
      S4    A7               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S4    A8               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S5    A1              S2
      S5    A2              S2   Error: Inappropriate Authentication
      S5    A5              S1
      S5    A6              S5
      S5    A7               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S5    A8               ?   identity could be provided by
                                  another underlying mechanism such
                                  as IPSec.
      S6    A1              S3
      S6    A2              S2   Error: Inappropriate Authentication
      S6    A5              S1
      S6    A6              S6
      S6    A7 and D1=NO    S6   Error: InvalidCredentials
      S6    A7 and D1=YES   S7
      S6    A8 and D2=NO    S3   Error: InvalidCredentials
      S6    A8 and D2=YES   S8
      S7    A1              S3
      S7    A2              S2   Error: Inappropriate Authentication
      S7    A5              S1
      S7    A6              S6
      S7    A7              S7
      S7    A8 and D2=NO    S3   Error: InvalidCredentials
      S7    A8 and D2=YES   S8
      S8    A1              S3
      S8    A2              S2   Error: Inappropriate Authentication
      S8    A5              S1
      S8    A6              S6
      S8    A7 and D1=NO    S6   Error: InvalidCredentials
      S8    A7 and D1=YES   S7
      S8    A8              S8
     Any   A9              S1   See [Protocol] section 4.2.1.

6. Anonymous Authentication

   Directory operations that modify entries or access
   connection is protected
   attributes using TLS or entries generally require client authentication.
   Clients other data confidentiality and
   data integrity protection.

6.2. Digest Authentication

   LDAP servers that do not intend to perform implement any of these operations
   typically use anonymous authentication. Servers SHOULD NOT allow
   clients with anonymous authentication to modify directory entries method or
   access sensitive information in directory entries.

   LDAP implementations MUST support anonymous authentication, as
   defined in section 6.1.

   LDAP implementations MAY support mechanism
   (other than simple anonymous bind) MUST implement the SASL
   DIGEST-MD5 mechanism [DIGEST-MD5].  This provides client
   authentication with TLS,
   as defined protection against passive eavesdropping
   attacks, but does not provide protection against active intermediary
   attacks.  DIGEST-MD5 also provides data integrity and data
   confidentiality capabilities.

   Support for subsequent authentication is OPTIONAL 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 clients and
   servers.

   Implementors must take care to retrieve ensure that they maintain the supportedSASLMechanisms attribute
   semantics 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 DIGEST-MD5 specification even
   to anonymously authenticated clients.

6.1. Anonymous Authentication Procedure

   Prior to successfully completing a Bind operation, when handling data
   that has different semantics in the LDAP
   association is anonymous. See section 3.1.

   An LDAP client may also explicitly establish an anonymous
   association. A client that wishes to do so MUST choose protocol.
   For example, the SASL DIGEST-MD5 authentication mechanism utilizes
   realm and username values ([DigestAuth section 2.1) which are
   syntactically simple
   authentication option in the Bind Request strings and set the password to be
   of zero length. (This is often done by LDAPv2 clients.) Typically
   the name is also of zero length. A bind request where both the name semsantically simple realm and password
   username values. These values are of zero length not LDAP DNs, and there is said to no
   requirement that they be an anonymous bind. A
   bind request where represented or treated as such. Username
   and realm values that look like LDAP DNs in form, e.g. <cn=bob,
   dc=example,dc=com>, are syntactically allowed, however DIGEST-MD5
   treats them as simple strings for comparison purposes. To illustrate
   further, the name, a DN, is of non-zero length, two DNs <cn=Bob,dc=example,dc=com> (upper case "B") and
   <cn=bob,dc=example,dc=com> (lower case "b") are equivalent when
   being compared semantically as LDAP DNs because the
   password is of zero length cn attribute is said
   defined to be case insensitive, however the two values are not
   equivalent if they represent username values in DIGEST-MD5 because
   [SASLPrep] semantics are used by DIGEST-MD5.

6.3. simple authentication choice under TLS encryption

   Following the negotiation of an unauthenticated bind.
   Both variations produce an anonymous association.

6.2. Anonymous Authentication and appropriate TLS

   An LDAP ciphersuite
   providing connection confidentiality, a client MAY authenticate to a
   directory that supports the simple authentication choice by
   performing a simple bind operation

   Simple authentication with TLS encryption protection is performed as
   follows:

      1. The client will use the Start TLS operation (section 5) [Protocol] to
        negotiate the use of TLS security [TLS] security. If on the connection to
        the LDAP server. The client has need not have bound
   beforehand, then until to the client uses
        directory beforehand.

         For the EXTERNAL SASL mechanism subsequent authentication procedure to negotiate be performed
         securely, the recognition client and server MUST negotiate a ciphersuite
         which contains a bulk encryption algorithm of the client's certificate, the client
   is anonymously authenticated. appropriate
         strength. Recommendations on TLS ciphersuites cipher suites are given in
         section 9.

   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

      2. Following the successful completion of TLS negotiation if negotiation, the
         client did
   not present a certificate which could be validated.

7. Password-based Authentication

   This section discusses various options for performing password-based
   authentication to MUST send an LDAP compliant servers bind request with the version number
         of 3, the name field containing a DN, and the environments
   suitable for their use.

7.1. Simple Authentication

   The LDAP "simple" authentication choice is not suitable for simple
         authentication choice, containing a password.

6.3.1. simple Authentication Choice

   DSAs that map the DN sent in environments where there is no network or
   transport layer confidentiality. LDAP implementations SHOULD support
   authentication the bind request to a directory entry
   with an associated set of one or more passwords will compare the "simple" authentication choice when
   presented password to the
   connection is protected against eavesdropping using TLS, as defined
   in section 4. LDAP implementations SHOULD NOT support authentication set of passwords associated with that
   entry. If the "simple" authentication choice unless presented password matches any member of that set,
   then the data on server will respond with a success resultCode, otherwise
   the
   connection is protected using TLS or other data confidentiality and
   data integrity protection.

7.2. Digest Authentication

   LDAP servers that implement any server will respond with an invalidCredentials resultCode.

6.4. Other authentication method or mechanism
   (other than simple anonymous bind) MUST implement choices with TLS

   It is also possible, following the negotiation of TLS, to perform a
   SASL
   DIGEST-MD5 mechanism [DigestAuth].

   Support for subsequent authentication is OPTIONAL in clients and
   servers.

   Implementors must take care to ensure that they maintain does not involve the
   semantics exchange of plaintext
   reusable passwords. In this case the DIGEST-MD5 specification even when handling data client and server need not
   negotiate a ciphersuite that has different semantics in provides confidentiality if the only
   service required is data integrity.

7. Certificate-based authentication

   LDAP protocol.
   For example, the SASL DIGEST-MD5 server implementations SHOULD support authentication mechanism utilizes
   realm and username values ([DigestAuth via a
   client certificate in TLS, as defined in section 2.1) 7.1.

7.1. Certificate-based authentication with TLS

   A user who has a public/private key pair in which are
   syntactically simple strings and semsantically simple realm and
   username values. These values are not LDAP DNs, and there 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 no
   requirement that they
   requested by the server. The user's certificate subject field SHOULD
   be represented or treated as such. Username the name of the user's directory entry, and realm values the Certification
   Authority that look like LDAP DNs in form, e.g. "cn=bob,
   o=Ace Industry ", are syntactically allowed, however DIGEST-MD5
   treats them as simple strings for comparison purposes. To illustrate
   further, issued the two DNs "cn=bob, o=Ace Industry" (space between RDNs)
   and "cn=bob,o=Ace Industry" (no space between RDNs) would user's certificate must be
   equivalent when being compared semantically as LDAP DNs, however
   they are not equivalent if they were used to represent username
   values sufficiently
   trusted by the directory server in DIGEST-MD5 because simple octet-wise comparision semantics
   are used order for the server to process
   the certificate. The means by DIGEST-MD5.

7.3. "simple" authentication choice under TLS encryption

   Following which servers validate certificate
   paths is outside the negotiation scope of an appropriate TLS ciphersuite
   providing connection confidentiality, a client this document.

   A server MAY authenticate to a support mappings for certificates in which the subject
   field name is different from the name of the user's directory that entry.
   A server which supports the simple authentication choice by
   performing a simple bind operation

   Simple authentication with TLS encryption protection mappings of names MUST be capable of being
   configured to support certificates for which no mapping is performed as
   follows:

      1. required.

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

         For the subsequent authentication procedure to be performed
         securely, 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 9.

      2. Following

   In the successful completion of TLS negotiation, the
         client server 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 an associated set of one or more passwords certificate. The
   client will compare the
   presented password provide its certificate to the set of passwords associated with that
   entry. If the presented password matches any member of that set,
   then server, and the server will respond with
   MUST perform a success resultCode, otherwise private key-based encryption, proving it has the server will respond with an invalidCredentials resultCode.

7.4. Other authentication choices with TLS

   It is also possible, following
   private key associated with the negotiation of TLS, to perform a
   SASL authentication certificate.

   In deployments that does not involve the exchange require protection of plaintext
   reusable passwords. In this case sensitive data in transit,
   the client and server need not MUST negotiate a ciphersuite that provides confidentiality if the only
   service required is data integrity.

8. Certificate-based authentication

   LDAP server implementations SHOULD support authentication via contains a
   client certificate in TLS, as defined
   bulk encryption algorithm of appropriate strength. Recommendations
   of cipher suites are given in section 8.1.

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 9.

   The server if MUST verify that the user's client's certificate is
   requested by the server. valid. The user's certificate subject field SHOULD
   be the name of
   server will normally check that the user's directory entry, certificate is issued by a known
   certification authority (CA), and the Certification
   Authority that issued none of the user's certificates on
   the client's certificate must be sufficiently
   trusted chain are invalid or revoked. There are
   several procedures by which the directory server in order for can perform these checks.

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

8. LDAP Association State Transition Tables

   To comprehensively diagram the various authentication and TLS states
   through hich an LDAP association may pass, this section provides a
   state transition table to process represent a state diagram for the certificate. various
   states through which an LDAP association may pass during the course
   of its existence and the actions that cause these changes in state.

8.1. LDAP Association States

   The means by which servers validate certificate
   paths is outside following table lists the scope valid LDAP association states and
   provides a description of this document.

   A server MAY support mappings each state. The ID for certificates each state is used
   in which the subject
   field name state transition table in section 8.4.

   ID State Description
   -- --------------------------------------------------------------
   S1 Anonymous
          no Authentication ID is different from the name of associated with the user's directory entry.
   A server which supports mappings of names MUST be capable of being
   configured to support certificates for which LDAP connection
          no mapping Authorization ID is required. in force
   S2 Authenticated
          Authentication ID = I
          Authorization ID = X
   S3 Authenticated SASL EXTERNAL, implicit authorization ID
          Authentication ID = J
          Authorization ID = Y
   S4 Authenticated SASL EXTERNAL, explicit authorization ID
          Authentication ID = J
          Authorization ID = Z

8.2. Actions that Affect LDAP Association State

   The client will use following table lists the Start TLS operation [Protocol] to negotiate actions that can affect the use
   authentication and authorization state of TLS security [TLS] on an LDAP association. The
   ID for each action is used in the connection state transition table in section
   8.4.

   ID  Action
   --  --------------------------------------------------------------
   A1  Client bind request fails
   A2  Client successfully performs anonymous simple bind
   A3  Client successfully performs unauthenticated simple bind
   A4  Client successfully performs simple bind with name and
        password OR SASL bind with any mechanism except EXTERNAL using
        an authentication ID = I that maps to the LDAP server. authorization ID X
   A5  Client Binds SASL EXTERNAL with implicit assertion of
        authorization ID (section 3.3.6.1)]. The client need not have bound current
        authentication ID maps to authorization ID = Y.
   A6  Client Binds SASL EXTERNAL with explicit assertion of
        authorization ID = Z (section 3.3.6.2)]
   A7  Client abandons a bind operation, and server processes the directory beforehand.

   In
        abandon
   A8  Client abandons a bind operation, and server does not process
        the abandon
   A9  Client Start TLS negotiation, the server MUST request a certificate. The
   client will provide its certificate to fails
   A10 Client Start TLS request succeeds
   A11 Client or Server: graceful TLS closure ([Protocol] section
        4.13.3.1.)

8.3. Decisions Used in Making LDAP Association State Changes

   Certain changes in the server, authentication and authorization state of an
   LDAP association are only allowed if the server
   MUST perform can affirmatively
   answer a private key-based encryption, proving it has the
   private key associated with the certificate.

   In deployments that require protection question. These questions are applied as part of sensitive data in transit, the client and server MUST negotiate a ciphersuite that contains
   criteria for allowing or disallowing a
   bulk encryption algorithm of appropriate strength. Recommendations
   of cipher suites are given state transition in section 9.

   The server MUST verify that the client's certificate is valid. state
   transition table in section 8.4.

   ID Decision Question
   -- --------------------------------------------------------------
   D1 Are lower-layer credentials available?
   D2 Can lower-layer credentials for Auth ID "K" be mapped asserted
       AuthZID "L"?

8.4. LDAP Association State Transition Table

   The
   server will normally check that LDAP Association table below lists the certificate is issued by a known
   certification authority (CA), valid authentication and
   authorization states for an LDAP association and the actions that none of
   could affect them. For any given row in the certificates on table, the client's certificate chain are invalid or revoked. There are
   several procedures by which Current State
   column gives the state of an LDAP association, the server can perform these checks.

   Following Action column
   gives an action that could affect the successful completion state of TLS negotiation, an LDAP assocation,
   and the client
   will send Next State column gives the resulting state of an LDAP bind request with
   association after the SASL "EXTERNAL" mechanism. action occurs.

   S1, the initial state for the state machine described in this table,
   is the authentication state when an LDAP connection is initially
   established.

   Current            Next
    State  Action     State  Comment
   ------- -------    -----  ---------------------------------------
     Any   A1          S1    [Protocol] section 4.2.1
     Any   A2          S1    Section 6
     Any   A3          S1    Section 6
     Any   A4          S2    Sections 6.1, 6.2
     Any   A5,         S1    Failed bind, section 3.3.6
            D1=no
     Any   A5,         S3
            D1=yes
     Any   A6,         S1    failed bind, section 3.3.6
            D1=no
     Any   A6,         S1    failed bind, section 3.3.6.2
            D1=yes,
            D2=no
     Any   A6,         S4
            D1=yes,
            D2=yes
     Any   A7          S1    [Protocol] section 4.2.1. Clients
                               cannot detect this state.
     Any   A8          no    [Protocol] section 4.2.1. Clients
                      change  cannot detect this state.
     Any   A9          no    [Protocol] section 4.13.2.2
                      change
     Any   A10         no    Section 4.2.1
                      change
     Any   A11         S1    Section 4.2.3

9. TLS Ciphersuites

   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.

   Several issues should be considered when selecting TLS ciphersuites
   that are appropriate for use in a given circumstance. These issues
   include the following:

     - The ciphersuite's ability to provide adequate confidentiality
       protection for passwords and other data sent over the LDAP
       connection. Client and server implementers should recognize that
       some TLS ciphersuites provide no confidentiality protection
       while other ciphersuites that do provide confidentiality
       protection may be vulnerable to being cracked using brute force
       methods, especially in light of ever-increasing CPU speeds that
       reduce the time needed to successfully mount such attacks.

       Client and server implementers SHOULD carefully consider the
       value of the password or data being protected versus the level
       of confidentially protection provided by the ciphersuite to
       ensure that the level of protection afforded by the ciphersuite
       is appropriate.

     - The ciphersuite's vulnerability (or lack thereof) to man-in-the-
       middle attacks. Ciphersuites vulnerable to man-in-the-middle
       attacks SHOULD NOT be used to protect passwords or sensitive
       data, unless the network configuration is such that the danger
       of a man-in-the-middle attack is tolerable.

9.1. TLS Ciphersuites Recommendations

   As of the writing of this document, the following recommendations
   regarding TLS ciphersuites are applicable. Because circumstances are
   constantly changing, this list must not be considered exhaustive,
   but is hoped that it will serve as a useful starting point for
   implementers.

   The following ciphersuites defined in [TLS] 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 [TLS] can be cracked easily
   (less than a day of CPU time on a standard CPU in 2000) and are NOT
   RECOMMENDED for use in confidentiality protection of passwords or
   data.

         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:

         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

10. Security Considerations

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

   Servers are encouraged to prevent modifications by anonymous users.

   Servers may also wish to can minimize denial of service attacks by timing out idle
   connections, and returning the unwillingToPerform resultCode rather
   than performing computationally expensive operations requested by
   unauthorized clients.

   The use of cleartext passwords and other unprotected authentication
   credentials is strongly discouraged over open networks when the
   underlying transport service cannot guarantee confidentiality.

   Operational experience shows that clients can (and frequently do)
   misuse unauthenticated
   access (simple bind with name but no password). (see section 5.1).  For example, a
   client program might authenticate make a user via LDAP and then decision to grant access to information not stored in the non-
   directory information on the basis of completing a successful bind. bind
   operation. Some LDAP server implementations will return a success
   response to a simple bind that consists of a user name and an empty password unauthenticated bind thus leaving the client with the
   impression that the client server has successfully authenticated the
   identity represented by the user name, when in reality, the directory server has simply performed effect, an anonymous bind.  For this reason, servers SHOULD by default reject
   authentication requests
   LDAP association has been created. Clients that have use the results from
   a DN with an simple bind operation to make authorization decisions should
   actively detect unauthenticated bind requests (via the empty
   password with
   an error of invalidCredentials. value) and react appropriately.

   Access control SHOULD always be applied when reading sensitive
   information or updating directory information.

   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.

   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.

   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 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.

   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-
   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 [TLS].

11. IANA Considerations

   The following IANA considerations apply to this document:

   Please update the GSSAPI service name registry to point to [Roadmap]
   and this document.

   [To be completed]

Contributors

Acknowledgements

   This document combines information originally contained in RFC 2829
   and RFC 2830. The editor 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.

Acknowledgements

   This document is based upon input of the IETF LDAP Revision working
   group. The contributions and suggestions made by its members in
   shaping the contents and technical accuracy of this document is
   greatly appreciated.

Normative References

   [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
       Requirement Levels", BCP 14, RFC 2119, March 1997.

   [RFC2234]

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

   [DigestAuth]

   [DIGEST-MD5] Leach, P. C. Newman, and A. Melnikov, "Using Digest
      Authentication as a SASL Mechanism", draft-ietf-sasl-rfc2831bis-
      xx.txt, a work in progress.

   [LDAPDN] Zeilenga, Kurt D. (editor), "LDAP: String Representation of
      Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, a work in
      progress.

   [Model]

   [Models] Zeilenga, Kurt D. (editor), "LDAP: Directory Information
       Models", draft-ietf-ldapbis-models-xx.txt, a work in progress.

   [Protocol] Sermersheim, J., "LDAP: The Protocol", draft-ietf-
       ldapbis-protocol-xx.txt, a work in progress.

   [Roadmap] K. Zeilenga, "LDAP: Technical Specification Road Map",
       draft-ietf-ldapbis-roadmap-xx.txt, a work in progress.

   [SASL] Melnikov, A. (editor), "Simple Authentication and Security
       Layer (SASL)", draft-ietf-sasl-rfc2222bis-xx.txt, a work in
       progress.

   [SASLPrep] Zeilenga, K., "Stringprep profile for user names and
       passwords", draft-ietf-sasl-saslprep-xx.txt, (a work in
       progress).

   [StringPrep]  Hoffman P. and M. Blanchet, "Preparation of
       Internationalized Strings ('stringprep')", draft-hoffman-
       rfc3454bis-xx.txt, a work in progress.

   [Syntaxes] Legg, S. (editor), "LDAP: Syntaxes and Matching Rules",
       draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress.

   [TLS] Dierks, T. and C. Allen. "The TLS Protocol Version 1.1",
       draft-ietf-tls-rfc2246-bis-xx.txt, a work in progress.

   [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
       RFC 2279, January 1998.

   [Unicode] International Organization for Standardization, "Universal
       Multiple-Octet Coded Character Set (UCS) - Architecture and
       Basic Multilingual Plane", ISO/IEC 10646-1 : 1993.

Informative References

   [ANONYMOUS] Zeilenga, K.,"Anonymous SASL Mechanism", draft-zeilenga-
       sasl-anon-xx.txt, a work in progress.

   [PLAIN] Zeilenga, K.,"Plain SASL Mechanism", draft-zeilenga-sasl-
       plain-xx.txt, a work in progress.

    [RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May
       2000.

   [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
       Internet Protocol", RFC 2401, 3629, STD 63, November 1998.

Author's Address

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

Full Copyright Statement

   Copyright (C) 2003.

   [Unicode] The Internet Society (2003). 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 Unicode Consortium, "The Unicode Standard, Version
       3.2.0" is defined in the Internet Standards process must be
   followed, or by "The Unicode Standard, Version 3.0"
       (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5), as required to translate it into languages other than
   English.

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

   This document "Unicode Standard Annex #27: Unicode 3.1"
       (http://www.unicode.org/reports/tr27/) and by the information contained herein is provided on an
   "AS IS" basis ÷Unicode
       Standard Annex #28: Unicode 3.2"
       (http://www.unicode.org/reports/tr28/).

Informative References

   [ANONYMOUS] Zeilenga, K.,"Anonymous SASL Mechanism", draft-zeilenga-
       sasl-anon-xx.txt, a work in progress.

   [PLAIN] Zeilenga, K.,"Plain SASL Mechanism", draft-zeilenga-sasl-
       plain-xx.txt, a work in progress.

    [RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May
       2000.

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

Author's Address

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

Appendix A. Example Deployment Scenarios

   The following scenarios are typical for LDAP directories on the
   Internet, and have different security requirements. (In the
   following discussion, "sensitive data" refers to information whose
   disclosure, alteration, destruction, or loss would adversely affect
   the interests or business of its owner or user. Also note that 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. Anonymous authentication, described in section 7, is
       suitable for this type of deployment, and requires no additional
       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 data confidentiality
       for sensitive authentication information AND data integrity for
       all authentication information.

   (3) A read-only directory containing no sensitive data; and the
       client needs to ensure the identity of the directory server and
       that the directory data is not modified while being returned
       from the server. A data origin authentication service AND data
       integrity service are required.

   (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 data confidentiality for
       sensitive authentication information AND data integrity for all
       authentication information.

   (5) A directory containing sensitive data. This scenario requires
       data 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 factors
   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
   [Protocol]). The server uses these factors to determine whether and
   how to process the request. These are called access control factors
   (ACFs). They might include source IP address, encryption strength,
   the type of operation being requested, time of day, etc. Some
   factors may be specific to the request itself, others may be
   associated with the connection via which the request is transmitted,
   others (e.g. time of day) may be "environmental".

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

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.

C.0. General Editorial Changes
   Version -00

     - Changed other instances of the term LDAP to LDAP where v3 of the
       protocol is implied. Also made all references to LDAP 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

     - 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 password...")
       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 LDAP
       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.

     - 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."

     - Added section 9.1. heading.

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

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

     - Added section 9.1.1. heading.

     - Added section 9.1.2. heading.

   Version -01

     - Moved entire section 9 to become section 3.5 so that it would be
       with other SASL material.

C.10. Changes to Section 10.

   Version -00

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

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

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

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 section 3.7 to be with other SASL material.

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

   None

Appendix D. RFC 2830 Change History

   This appendix lists the changes made to the text of RFC 2830 in
   preparing this document.

D.0. General Editorial Changes

     - Material showing the PDUs for the Start TLS response was broken
       out into a new section.

     - The wording of the definition of the Start TLS request and Start
       TLS response was changed to make them parallel. NO changes were
       made to the ASN.1 definition or the associated values of the
       parameters.

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

Appendix E. RFC 2251 Change History

   This appendix lists the changes made to the 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 was brought within
       the discussion of the Bind operation (primarily sections 4.4 -
       4.7).

Appendix F. Change History to Combined Document

F.1. Changes for draft-ldap-bis-authmeth-02

   General
     - Added references to other LDAP standard documents, to sections
       within the document, and fixed broken references.

     - General editorial changes--punctuation, spelling, formatting,
       etc.

   Section 1.

     - Added glossary of terms and added sub-section headings

   Section 2.

     - Clarified security mechanisms 3, 4, & 5 and brought language in
       line with IETF security glossary.

   Section 3.

     - Brought language in requirement (3) in line with security
       glossary.

     - Clarified that information fetched prior to initiation of TLS
       negotiation must be discarded

     -Clarified that information fetched prior to initiation of SASL
       negotiation must be discarded

     - Rewrote paragraph on SASL negotiation requirements to clarify
       intent

   Section 4.4.

     - Added stipulation that sasl choice allows for any SASL mechanism
       not prohibited by this document. (Resolved conflict between this
       statement and one that prohibited use of ANONYMOUS and PLAIN
       SASL mechanisms.)

   Section 5.3.6

     - Added a.x.bar.com to wildcard matching example on hostname
       check.

   Section 6

     - Added LDAP Association State Transition Tables to show the
       various states through which an LDAP association may pass along
       with the actions and decisions required to traverse from state
       to state.

   Appendix A

     - Brought security terminology in line with IETF security glossary
       throughout the appendix.

F.2. Changes for draft-ldap-bis-authmeth-03
   General

     - Added introductory notes and changed title of document and
       references to conform to WG chair suggestions for the overall
       technical specification.

     - Several issues--G.13, G.14, G.16, G.17--were resolved without
       requiring changes to the document.

   Section 3

     - Removed reference to /etc/passwd file and associated text.

   Section 4

     - Removed sections 4.1, 4.2 and parts of section 4.3. This
       information was being duplicated in the protocol specification
       and will now reside there permanently.
   Section 4.2

     - changed words, "not recommended" to "strongly discouraged"

   Section 4.3

     - Based on ldapbis WG discussion at IETF52 two sentences were
       added indicating that clients SHOULD NOT send a DN value when
       binding with the sasl choice and servers SHALL ignore any value
       received in this circumstance.
     -

   Section 8.3.1

     - Generalized the language of this section to not refer to any
       specific password attribute or to refer to the directory entry
       as a "user" entry.

   Section 11

     - Added security consideration regarding misuse of unauthenticated
       access.

     - Added security consideration requiring access control to be
       applied only to authenticated users and recommending it be
       applied when reading sensitive information or updating directory
       information.

F.3. Changes for draft-ldap-bis-authmeth-04

   General

     - Changed references to use [RFCnnnn] format wherever possible.
       (References to works in progress still use [name] format.)
     - Various edits to correct typos and bring field names, etc. in
       line with specification in [Protocol] draft.

     - Several issues--G.13, G.14, G.16, G.17--were resolved without
       requiring changes to the document.

   Section 4.4.1.

     - Changed ABNF grammar to use productions that are like those in
       the model draft.

   Section 5

     - Removed sections 5.1, 5.2, and 5.4 that will be added to
       [Protocol]. Renumbered sections to accommodate this change.
     -

   Section 6

     - Reviewed LDAP Association State table for completeness and
       accuracy. Renumbered actions A3, A4, and A5 to be A5, A3, and A4
       respectively. Re-ordered several lines in the table to ensure
       that actions are in ascending order (makes analyzing the table
       much more logical). Added action A2 to several states where it
       was missing and valid. Added actions A7 and A8 placeholders to
       states S1, S2, S4 and S5 pending resolution of issue G.28.

   Section 11

     - Modified security consideration (originally added in -03)
       requiring access control to be applied only to authenticated
       users. This seems nonsensical because anonymous users may have
       access control applied to limit permissible actions.
     -
   Section 13

     - Verified all normative references and moved informative
       references to a new section 14.

F.4. Changes for draft-ldap-bis-authmeth-05

   General

     - General editory changes to fix punctuation, spelling, line
       length issues, etc.
     - Verified and updated intra- and inter-document references
       throughout.
     - Document-wide review for proper usage of RFC 2119 keywords with
       several changes to correct improper usage.

   Abstract
     - Updated to match current contents of documents. This was needed
       due to movement of material on Bind and Start TLS operations to
       [Protocol] in this revision.

   Section 3.

     - Renamed section to "Rationale for LDAP Security Mechanisms" and
       removed text that did not support this theme. Part of the
       motivation for this change was to remove the implication of the
       previous section title, "Required Security Mechanisms", and
       other text found in the section that everything in the section
       was a requirement

     - Information from several removed paragraphs that describe
       deployment scenarios will be added Appendix A in the next
       revision of the draft.

     - Paragraph beginning, " If TLS is negotiated, the client MUST
       discard all information..." was moved to section 5.1.7 and
       integrated with related material there.

     - Paragraph beginning, "If a SASL security layer is negotiated..."
       was moved to section 4.2

   Section 4.l.

     - Changed wording of first paragraph to clarify meaning.

   Section 4.2.
     - Added paragraph from section 3 of -04 beginning, "If a SASL
       security layer is negotiated..."

   Section 4.3.3.
     - Renamed to "Other SASL Mechanisms" and completely rewrote the
       section (one sentence) to generalize the treatment of SASL
       mechanisms not explicitly mentioned in this document.

   Section 4.4.1.

     - Added paragraph beginning, "The dnAuthzID choice allows client
       applications..." to clarify whether DN form authorization
       identities have to also have a corresponding directory entry.
       This change was based on editor's perception of WG consensus.

     - Made minor clarifying edits in the paragraph beginning, "The
       uAuthzID choice allows for compatibility..."

   Section 5.1.1.

     - Made minor clarifying edits in the last paragraph of the
       section.

   Section 5.1.7.

     - Wording from section 3 paragraph beginning " If TLS is
       negotiated, the client MUST discard all information..." was
       moved to this section and integrated with existing text.

   Section 5.2.

     - Changed usage of "TLS connection" to "TLS session" throughout.

     - Removed empty section 5.2.1 and renumbered sections it had
       previously contained.

   Section 8.

     - Added introductory paragraph at beginning of section.

   Section 8.1.

     - Changed term  "data privacy" to "data confidentiality" to be
       consistent with usage in rest of document.

   Section 8.2.

     - Changed first paragraph to require implementations that
       implement *password-based* authentication to implement and
       support DIGEST-MD5 SASL authentication.

   Section 11.

     - First paragraph: changed "session encryption" to "session
       confidentiality protection" to be consistent with usage in rest
       of document.

   Appendix A.

     - Began changes to incorporate information on deployment scenarios
       removed from section 3.

F.5. Changes for draft-ldap-bis-authmeth-06

   General

     - Combined Section 2 (Introduction) and Section 3 (Motivation) and
       moved Introduction to section 1. All following sections numbers
       were decremented by one as result.

     - Edits to fix typos, I-D nits, etc.

     - Opened several new issues in Appendix G based on feedback from
       WG. Some of these have been resolved. Others require further
       discussion.

   Section 1
     - Added additional example of spoofing under threat (7).

   Section 2.1

     - Changed definition of "LDAP association" and added terms,
       "connection" and "TLS connection" to bring usage in line with
       [Protocol].

   Section 4.1.6

     - Clarified sentence stating that the client MUST NOT use derived
       forms of DNS names.

   Section 5.1

     - Began edits to LDAP Association state table to clarify meaning
       of various states and actions.

     - Added action A9 to cover abandoned bind operation and added
       appropriate transitions to the state transition table to
       accommodate it.

   Section 7.2

     - Replaced first paragraph to clarify that the "DIGEST-MD5" SASL
       mechanism is required to implement.

   Section 9

     - Rewrote the section to make the advice more applicable over the
       long term, i.e. more "timeless." The intent of content in the
       original section was preserved.

   Section 10

     - Added a clarifying example to the consideration regarding misuse
       of unauthenticated access.

F.6. Changes for draft-ldap-bis-authmeth-07

   General

     - Updated external and internal references to accommodate changes
       in recent drafts.

     - Opened several new issues in Appendix G based on feedback from
       WG. Some of these have been resolved. Others require further
       discussion.

   Section 3

     - Rewrote much of section 3.3 to mee meet the SASL profile
       requirements of draft-ietf-sasl-rfc2222bis-xx.txt section 5.

     - Changed treatement of SASL ANONYMOUS and PLAIN mechanisms to
       bring in line with WG consensus.

   Section 4

     - Note to implementers in section 4.1.1 based on operational
       experience.

     - Clarification on client continuing by performing a Start TLS
       with TLS already established in section 4.1.4.

     - Moved verification of mapping of client's authentication ID to
       asserted authorization ID to apply only to explicit assertion.
       The local policy in place for implicit assertion is adequate.

   Section 7

     - Removed most of section 7.2 as the information is now covered
       adequately via the new SASL profile in section 3.3. Added note
       to implementors regarding the treatment of username and realm
       values in DIGEST-MD5.

     - Section 7.3. Minor clarifications in wording.

     - Section 7.3.1. Clarification that a match of the presented value
       to any member of the set of stored passwords constitutes a
       successful authentication.

F.6. Changes for draft-ldap-bis-authmeth-08

   General

     - Changed usage from LDAPv3 to LDAP for usage consistency across
       LDAP technical specification.

     - Fixed a number of usage nits for consistency and to bring doc in
       conformance with publication guidelines.

   Abstract

     - Significant cleanup and rewording of abstract based on WG
       feedback.

   Section 2.1

     - New definition of user.

   Section 3

     - Added 1.5 sentences at end of introductory paragraph indicating
       the effect of the Bind op on the LDAP association.

   Section 3.1

     - Retitled section and clarified wording

   Section 3.2

     - Clarified that simple authentication choice provides three types
       of authentication: anonymous, unauthenticated, and simple
       password.

   Section 3.3.3 3.3.3

     - New wording clarifying when negotiated security mechanisms take
       effect.

   Section 3.3.5

     - Changed requirement to discard information about server fetched
       prior to SASL negotiation from MUST to SHOULD to allow for
       information obtained through secure mechanisms.

   Section 3.3.6

     - Simplified wording of first paragraph based on suggestion from
       WG.

   Section 3.4

     - Minor clarifications in wording.

   Section 3.4.1

     - Minor clarifications in wording in first sentence.
     - Explicitly called out that the DN value in the dnAuthzID form is
       to be matched using DN matching rules.
     - Called out that the uAuthzID MUST be prepared using SASLprep
       rules before being compared.
     - Clarified requirement on assuming global uniqueness by changing
       a "generally... MUST" wording to "SHOULD".

   Section 4.1.1

     - Simplified wording describing conditions when Start TLS cannot
       be sent.
     - Simplified wording in note to implementers regarding race
       condition with outstanding LDAP operations on connection.

   Section 4.1.5

     - Removed section and moved relevant text to section 4.2.2.

   Section 4.1.6

     - Renumbered to 4.1.5.

     - Updated server identity check rules for server's name based on
       WG list discussion.

   Section 4.1.7

     - New wording clarifying when negotiated security mechanisms take
       effect.

   Section 3.3.5 Renumbered to 4.1.6
     - Changed requirement to discard information about server fetched
       prior to SASL TLS negotion from MUST to SHOULD to allow for
       information obtained through secure mechanisms.

   Section 3.3.6 6.1

     - Simplified wording Clarified wording.
     - Added definition of first paragraph based on suggestion from
       WG. anonymous and unauthenticated binds.

   Section 3.4 10

     - Minor clarifications in wording. Added security consideration (moved from elsewhere) discouraging
       use of cleartext passwords on unprotected communication
       channels.

   Section 3.4.1 11

     - Minor larifications in wording Added an IANA consideration to update GSSAPI service name
       registry to point to [Roadmap] and [Authmeth]

F.7. Changes for draft-ldap-bis-authmeth-09

   General

     - Updated section references within document
     - Changed reference tags to match other docs in first sentence. LDAP TS
     - Explicitly called out that the DN value Used non-quoted names for all SAL mechanisms

   Abstract

     - Inspected keyword usage and removed several improper usages.

     - Removed sentence saying DIGEST-MD5 is LDAP's mandatory-to-
       implement mechanism. This is covered elsewhere in the dnAuthzID form document.

     - Moved section 5, authentication state table, of -08 draft to
       section 8 of -09 and completely rewrote it.

   Section 1

     - Reworded sentence beginning, "It is also desireable to be matched using DN matching rules. allow
       authentication methods to carry identities based on existing¨
       non-LDAP DN¨forms..."
     - Called out that Clarified relationship of this document to other documents in
       the uAuthzID MUST be prepared using SASLprep
       rules before being compared. LDAP TS.

   Section 3.3.5
     - Clarified requirement on assuming global uniqueness by changing Removed paragraph beginning,"If the client is configured to
       support multiple SASL mechanisms..." because the actions
       specified in the paragraph do not provide the protections
       indicated. Added a "generally... MUST" wording new paragraph indicating that clients and
       server should allow specification of acceptable mechanisms and
       only allow those mechanisms to "SHOULD".

   Section 4.1.1 be used.

     - Simplified wording describing conditions Clarified independent behavior when Start TLS cannot
       be sent.
     - Simplified wording and SASL security layers
       are both in note to implementers regarding race
       condition with outstanding LDAP operations on connection. force (e.g. one being removed doesn't affect the
       other).

   Section 4.1.5 3.3.6

     - Removed Moved most of section 4.2.2, Client Assertion of Authorization
       Identity, to sections 3.3.6, 3.3.6.1, and moved relevant 3.3.6.2.

   Section 3.3.6.4

     - Moved some normative comments into text to section 4.2.2. body.

   Section 4.1.6 4.1.2

     - Renumbered Non success resultCode values are valid if server is *unwilling*
       or unable to 4.1.5. negotiate TLS.

   Section 4.2.1

     - Updated server identity check rules for server's name Rewrote entire section based on WG list discussion. feedback.

   Section 4.1.7 4.2.2

     - Renumbered Moved most of this section to 4.1.6 3.3.6 for better document flow.

   Section 4.2.3

     - Changed requirement to discard information about server fetched
       prior to TLS negotion Rewrote entire section based on WG feedback.

   Section 5.1

     - Moved imperative language regarding unauthenticated access from MUST to SHOULD
       security considerations to allow for
       information obtained through secure mechanisms. here.

   Section 6.1

     - Clarified wording. 6

     - Added definition several paragraphs regarding the risks of anonymous transmitting
       passwords in the clear and unauthenticated binds. requiring server implementations to
       provide a specific configuration that reduces these risks.

   Section 10 6.2

     - Added security sentence describing protections provided by DIGEST-MD5
       method.
     - Changed DNs in exmple to be dc=example,dc=com.

   Section 10

     - Updated consideration (moved from elsewhere) discouraging on use of cleartext passwords on to include
       other unprotected communication
       channels.

   Section 11 authentication credentials
     - Added an IANA Substantial rework of consideration to update GSSAPI service name
       registry to point to [Roadmap] and [Authmeth] on misuse of unauthenticated
       bind.

Appendix G. Issues to be Resolved

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

G.1.

   Section 1 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.

   Status: resolved. Changed wording to "administrative service limits"
   to clarify meaning.

G.2.

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

   Status: resolved. WG input at IETF 51 was that we should do this, so
   the appropriate changes have been made.

G.3.

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

   Status: resolved. Based on the idea that a "secure authentication
   function" could be provided by TLS, I changed the wording to require
   data confidentiality for sensitive authentication information and
   data integrity for all authentication information.

G.4.

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

   Status: resolved. I interpreted this to mean the ability to ensure
   the identity of the directory server and the integrity of the data
   sent from that server to the client, and explictly stated such.

G.5.

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

   Status: resolved. Discussion at IETF 52 along with discussions with
   the original authors of this material have convinced us that this
   reference is simply too arcane to be left in place. In -03 the text
   has been modified to focus on the need to either update password
   information in a protected fashion outside of the protocol or to
   update it in session well protected against snooping, and the
   reference to /etc/passwd has been removed.

G.6.

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

   Status: resolved. Changed wording to say, "For a directory needing
   data security (both data integrity and data confidentiality)..."

G.7.

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

   Status: resolved. Based on comments in the IETF 51 LDAPBIS WG
   meeting, this has been changed to explicitly state, "fetched prior
   to the initiation of the TLS negotiation..."

G.8.

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

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

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

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

   Status: resolved. WG input at IETF 51 was that Approach 1 was
   probably best. I ended up keeping the basic structure similar to the
   original to meet this intent.

G.9.

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

   Status: resolved in -03 draft by generalizing section 8.3.1 to not
   refer to any specific password attribute and by removing the term
   "user" in referring to the directory entry specified by the DN in
   the bind request.

G.10 userPassword and simple bind

   We need to be sure that we don't require userPassword to be the only
   attribute used for authenticating via simple bind. (See 2251 sec 4.2
   and authmeth 6.3.1. Work with Jim Sermersheim on resolution to this.
   On publication state something like: "This is the specific
   implementation of what we discussed in our general reorg
   conversation on the list." (Source: Kurt Zeilenga)

   Status: resolved in -03 draft by generalizing section 8.3.1 to not
   refer to any specific password attribute and by removing the term
   "user" in referring to the directory entry specified by the DN in
   the bind request.

G.11. Meaning of LDAP Association

   The original RFC 2830 uses the term "LDAP association" in describing
   a connection between an LDAP client and server regardless of the
   state of TLS on that connection. This term needs to be defined or
   possibly changed.

   Status: resolved. at IETF 51 Bob Morgan indicated that the term
   "LDAP association" was intended to distinguish the LDAP-level
   connection from the TLS-level connection.  This still needs to be
   clarified somewhere in the draft. Added "LDAP association" to a
   glossary in section 1.

G.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 mechanism for password protection, as
   defined in section 6.1."

   The thing is for acl it would be nice (though not critical) to be
   able to default the required authentication level for a subject to a
   single "fairly secure" mechanism--if there is no such mandatory
   authentication scheme then you cannot do that. (Source: Rob Byrne)

   Status: resolved. -00 version of the draft added a sentence at the
   beginning of section 8.2 stating that LDAP server implementations
   must support this method.

G.13. Ordering of authentication levels requested

   Again on the subject of authentication level, is it possible to
   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
   authentication level AND ABOVE". David Chadwick raised this before
   in the 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)

   Status: out of scope. This is outside the scope of this document and
   will not be addressed.

G.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
   properties of the particular mandatory authentication schemes are
   outlined. When I say "security properties" I mean stuff like "This
   scheme is vulnerable to such and such attacks, is only safe if the
   key size is > 50, this hash is widely considered the best, etc...".
   I think an LDAP implementor is likely to be interested in that
   information, without having to wade through the security RFCs.
   (Source: Rob Byrne)

   Status: out of scope. This is outside the scope of this document and
   will not be addressed.

G.15. Include a StartTLS Start TLS 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)

   Status: In Process. Resolved.

   Table provided in -03. Review of content for accuracy in -04.
   Additional review is needed, plus comments from WG members indicate
   that additional description of each state's meaning would be
   helpful.

   Did a significant revision of state transition table in -09. Changes
   were based on suggestions from WG and greatly simplified overall
   table.

G.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 absent, and although they don't
   say what to do in the case of an empty octet string I would say that
   we could send protocolError (claim it is a bad PDU).

   There is still the question of what to do if the credential is 'dn:'
   (or 'u:') followed by the empty string. (Source: ariel@columbia.edu
   via Jeff Hodges)

   Status: resolved. Kurt Zeilenga indicated during ldapbis WG
   discussion at IETF 52 that SASL AuthzID credentials empty and absent
   are equivalent in the latest SASL ID. This resolves the issue.

G.17. Hostname check from MUST to SHOULD?

   I am uneasy about the hostname check. My experience from PKI with
   HTTP probably is a contributing factor; we have people using the
   short hostname to get to a server which naturally has the 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
   Columbia network with a fixed IP; when I dial in however, I have
   some horrible dialup name, and 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 name in the certificate is a
   very weak means of preventing man-in-the-middle attacks; the proper
   solution is not here yet (SecureDNS or some equivalent). Faking out
   DNS is not so hard, and we see this sort of thing in the press on a
   pretty regular basis, where site A hijacks the DNS server for site B
   and gets all their requests. Some mention of this should be made in
   the draft. (Source: ariel@columbia.edu via Jeff Hodges)

   Status: resolved. Based on discussion at IETF 52 ldapbis WG meeting,
   this text will stand as it is. The check is a MUST, but the behavior
   afterward is a SHOULD. This gives server implementations the room to
   maneuver as needed.

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

   If the 'dn:' form of sasl creds is used, is it the intention of the
   draft(ers) that this DN must exist in the directory and the client
   will have the privileges associated with that entry, or can the
   server map the sasl DN to perhaps some other DN in the directory,
   in an implementation-dependent fashion?

   We already know that if *no* sasl credentials are presented, the DN
   or altname in the client certificate may be mapped to a DN in an
   implementation-dependent fashion, or indeed to something not in the
   directory at all. (Right?)  (Source: ariel@columbia.edu via Jeff
   Hodges)

   Status: resolved. (11/12/02)Based on my research I propose that the
   DN MUST exist in the directory when the DN form of sasl creds is
   used. I have made this proposal to the ldapbis mailing list.

   (11/21/02) Feedback from mailing list has proposed removing this
   paragraph entirely because (1) explicit assertion of authorization
   identity should only be done when proxying (2) mapping of the
   asserted authorization identity is implementation specific and
   policy driven [SASL] section 4.2, and (3) keeping this paragraph is
   not required for interoperability.

G.19. DN used in conjunction with SASL mechanism

   We need to specify whether the DN field in Bind operation can/cannot
   be used when SASL mechanism is specified. (source: RL Bob)

   Status: resolved. (-03) Based on ldapbis WG discussion at IETF52 two
   sentences were added to section 4.3 indicating that clients SHOULD
   NOT send a DN value when binding with the sasl choice and servers
   SHALL ignore any value received in this circumstance. During edits
   for -04 version of draft it was noted that [Protocol] section 4.2
   conflicts with this draft. The editor of [Protocol] has been
   notified of the discrepancy, and they have been handled.

G.20. Bind states

   Differences between unauthenticated and anonymous. There are four
   states you can get into. One is completely undefined (this is now
   explicitly called out in [Protocol]).  This text needs to be moved
   from [Protocol] to this draft. (source: Jim Sermersheim)

   Status: Resolved. There are four states: (1) no name, no password
   (anon); (2) name, no password (anon); (3) no name, password
   (invalid); (4) name, password (simple bind).  States 1, 2, and 4 are
   called out in [AuthMeth]. State 3 is called out in [Protocol]; this
   seems appropriate based on review of alternatives.

G.21. Misuse of unauthenticated access

   Add a security consideration that operational experience shows that
   clients can misuse unauthenticated access (simple bind with name but
   no password).  Servers SHOULD by default reject authentication
   requests that have a DN with an empty password with an error of
   invalidCredentials. (Source: Kurt Zeilenga and Chris Newman (Sun))

   Status: Resolved. Added to security considerations in -03.

G.22. Need to move StartTLS Start TLS protocol information to [Protocol]

   Status: Resolved. Removed Sections 5.1, 5.2, and 5.4 for -04 and
   they are [Protocol] -11.

G.23. Split Normative and Non-normative references into separate
sections.

   Status: Resolved. Changes made in -04

G.24. What is the authentication state if a Bind operation is
abandoned?

   Status: Resolved.

   (3/24/03) This following text appears in section 4.2.1 of [Protocol]
   revision -13 to cover what happens if a bind operation is abandoned:

   A failed or abandoned Bind Operation has the effect of leaving the
   connection in an anonymous state. To arrive at a known
   authentication state after abandoning a bind operation, clients may
   unbind, rebind, or make use of the BindResponse.

   (6/28/03): The state table in section 6 of [AuthMeth] has been
   updated to reflect this wording.

G.25. Difference between checking server hostname and server's
canonical DNS name in Server Identity Check?

   Section 4.1.6: I now understand the intent of the check (prevent
   man-in-the-middle attacks).  But what is the subtle difference
   between the "server hostname" and the "server's canonical DNS name"?
   (Source: Tim Hahn)

   Status: Resolved.

   (11/12/02) Sent suggested wording change to this paragraph to the
   ldapbis mail list and also asked for opinion as to whether we should
   discuss the distinction between server DNS hostname and server
   canonical DNS hostname in [AuthMeth].

   (11/21/02): RL Bob Morgan will provide wording that allows
   derivations of the name that are provided securely.

   (6/28/03): posted to the WG list asking Bob or any other WG member
   who is knowledgeable about the issues involved to help me with
   wording or other information I can use to make this change and close
   the work item.

   (10/08/03): Based on WG list feedback, I've updated this text to
   read what I judge to be the WG consensus, "The client MUST use the
   server provided by the user (or other trusted entity) as the value
   to compare against the server name as expressed in the server's
   certificate. A hostname derived from the user input is to be
   considered provided by the user only if derived in a secure fashion
   (e.g., DNSSEC)."

G.26. Server Identity Check using servers located via SRV records

   Section 4.1.6: What should be done if the server was found using SRV
   records based on the "locate" draft/RFC? (Source: Tim Hahn).

   Status: Resolved. Section 5 of draft-ietf-ldapext-locate-08
   specifically calls out how the server identity should be performed
   if the server is located using the method defined in that draft.
   This is the right location for this information, and the coverage
   appears to be adequate.

G.27 Inconsistency in effect of TLS closure on LDAP association.

   Section 4.4.1 of authmeth -03 (section 4.1 of RFC2830) states that
   TLS closure alert will leave the LDAP association intact. Contrast
   this with Section 4.5.2 (section 5.2 of RFC2830) that says that the
   closure of the TLS connection MUST cause the LDAP association to
   move to an anonymous authentication.

   Status: Resolved. (11/12/02) This is actually a [Protocol] issue
   because these sections have now been moved to [Protocol] -11. I have
   proposed the following text for Section 4.4.1 of [AuthMeth] -03
   (section 4.13.3.1 of [Protocol]) to resolve this apparent
   discrepancy:

   "Either the client or server MAY terminate the TLS connection on an
   LDAP association by sending a TLS closure alert.  The LDAP
   connection remains open for further communication after TLS closure
   occurs although the authentication state of the LDAP connection is
   affected (see [AuthMeth] section 4.2.2).

   (11/21/02): resolution to this is expected in [Protocol] -12

   (06/28/03): [Protocol]-15 clarifies that a TLS closure alert
   terminates the TLS connection while leaving the LDAP connection
   intact. The authentication state table in [AuthMeth] specifies the
   effect on the LDAP association.

G.28 Ordering of external sources of authorization identities
   Section 4.3.2 implies that external sources of authorization
   identities other than TLS are permitted. What is the behavior when
   two external sources of authentication credentials are available
   (e.g. TLS and IPsec are both present (is this possible?)) and a SASL
   EXTERNAL Bind operation is performed?

   Status: resolved. 11/20/02: Resolved by Section 4.2 of [SASL] which
   states that the decision to allow or disallow the asserted identity
   is based on an implementation defined policy.

G.29 Rewrite of Section 9, TLS Ciphersuites

   This section contains anachronistic references and needs to be
   updated/rewritten in a way that provides useful guidance for future
   readers in a way that will transcend the passage of time.

   Status: Resolved. (6/28/03): Rewrote the section to cover the
   general issues and considerations involved in selecting TLS
   ciphersuites.

G.30 Update to Appendix A, Example Deployment Scenarios

   This section needs to be updated to indicate which security
   mechanisms and/or combinations of security mechanisms described
   elsewhere in the document can provide the types of protections
   suggested in this appendix.

G.31 Use of PLAIN SASL Mechanism

   At least one LDAP server implementer has found the SASL "PLAIN"
   mechanism useful in authenticating to legacy systems that do not
   represent authentication identities as DNs. Section 3.3.1 appears to
   implicitly disallow the use of the SASL "PLAIN" mechanism with LDAP.
   Should we allow the use of this mechanism? I.e. is this "SASL"
   "PLAIN" MUST NOT be used with LDAP, or is it simply that LDAP
   doesn't define bindings for these mechanism. If SASL "PLAIN" is
   allowed, the following adjustments will be needed to section 3.3.1:
   (a) change section heading, (b) remove reference to "PLAIN" in the
   section, (c) ensure wording of last sentence regarding non-DN
   AuthZIDs is consistent with rest of the section.

   Status: Resolved.

   (6/28/03): email to WG list stating issue and asking if we should
   remove the reference to SASL "PLAIN".

   For -07 draft I've generalized the SASL profile in section 3.3 to
   allow any SASL mechanism.

G.32 Clarification on use of SASL mechanisms

   Section 3.3.1: BTW, what _are_ the "ANONYMOUS" and "PLAIN" SASL
   mechanisms?  They are not defined in RFC2222.  If you refer to other
   SASL mechanisms than those in rfc2222, Maybe you should only list
   which mechanisms _are_used, instead of which ones are _not. (Source:
   Hallvard Furuseth)

   I (Kurt Zeilenga) note[s] as well that the ANONYMOUS/PLAIN section
   (4.2) should
   be deleted.  ANONYMOUS and PLAIN, like in other mechanism,
   can be used in LDAP if a) supported and b) enabled.  I note
   that they each offer capabilities not found in their simple
   bind equivalents (and hence are used in some deployments).
   For example, PLAIN (over TLS) is quite useful when interacting
   with legacy authentication subsystems.  (Source: Kurt Zeilenga)

   Status: Resolved.

   For -07 draft I've generalized the SASL profile in section 3.3 to
   allow any SASL mechanism.

G.33 Clarification on use of password protection based on AuthZID form

   Section 3.3.1: "If an authorization identity of a form different
   from a DN is requested by the client, a mechanism that protects the
   password in transit SHOULD be used." What has that to do with DNs?
   A mechanism that protects the password in transit should be used in
   any case, shouldn't it?

   Status: Resolved.

   In -08 draft this text was removed. There is already a general
   security consideration that covers this issue.

G.34 Clarification on use of matching rules in Server Identity Check

   The text in section 4.1.6 isn't explicit on whether all rules apply
   to both CN and dNSName values.  The text should be clear as to which
   rules apply to which values....  in particular, the wildcard
   rules. (Source: Kurt Zeilenga)

G.35 Requested Additions to Security Considerations

   Requested to mention hostile servers which the user might have been
   fooled to into contacting. Which mechanisms that are standardized by
   the LDAP standard do/do not disclose the user's password to the
   server? (Or to servers doing man-in-the-middle attack? Or is that a
   stupid question?)

   Requested to mention denial of service attacks.

   Requested list of methods that need/don't need the server to know
   the user's plaintext password. (I say 'know' instead of 'store'
   because it could still store the password encrypted, but in a way
   which it knows how to decrypt.)

   (Source: Hallvard Furuseth)

G.36 Add reference to definition of DIGEST-MD5

   Need a reference to the definition of DIGEST-MD5 SASL mechanism in
   section 7.2 (Source: Hallvard Furuseth)

   Status: Resolved. A reference to to the DIGEST-MD5 SASL mechanism,
   [DigestAuth], is included in the -07 revision.

G.37 Clarification on procedure for certificate-based authentication

   8.1. Certificate-based authentication with TLS states: "Following
   the successful completion of TLS negotiation, the client will send
   an LDAP bind request with the SASL "EXTERNAL" mechanism." Is this
   immediately following, or just some time later? Should the wording,
   "the client will send..." actually read, "the client MUST send..."?

G.38 Effect of StartTLS Start TLS on authentication state

   Should the server drop all knowledge of connection, i.e. return to
   anonymous state, if it gets a StartTLS Start TLS request on a connection that
   has successfully bound using the simple method?

G.39 Be sure that there is a consideration in [SCHEMA] that discusses
multiple password values in userPassword

   Allowing multiple values obviously does raise a number of security
   considerations and these need to be discussed in the document.

   Certainly applications which intend to replace the userPassword with
   new value(s) should use modify/replaceValues (or
   modify/deleteAttribute+addAttribute). Additionally, server
   implementations should be encouraged to provide administrative
   controls which, if enabled, restrict userPassword to one value.

G.40. Clarify need to verify mapping between authentication identity
and resulting authorization identity on implicit assertion of AuthZID.

   4.2.2.3. 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."

   This makes sense for the explicit assertion case, but seems to be
   ambiguous for the implicit case.
   IMHO, the mapping can be done as two steps:
   a). deriving LDAP authentication identity from TLS credentials; If t
   this steps fails, EXTERNAL mechanism returns failure.

   b). verify that the authorization identity is allowed for the
   derived authentication identity. This is always "noop" for the
   implicit case.
   I am not sure that the text text is saying this.
   (Source: Alexey Melnikov email 8/1/2003 5:30:43 PM)

   Status: Resolved in -07. After reading the comments and the text of
   the draft, I believe that this should be clarified. The local policy
   used to map the AuthNID to the AuthZID in the implicit case is
   sufficient and that no additional verification is useful or needed.
   This text has been moved to apply only to the explicit assertion
   case.

G.41. Section 7.2 contains unnecessary and misleading detail.

   " I am not sure why this section is required in the document.
   DIGEST-MD5 is defined in a separate document and there should be
   nothing magical about its usage in LDAP. If DIGEST-MD5 description
   creates confusion for LDAP implementors, let's fix the DIGEST-MD5
   document! Also, this section tries to redefine DIGEST-MD5 behavior,
   which is explicitly prohibited by the SASL specification."
   (Source: Alexey Melnikov: email 8/1/2003 5:30:43 PM)

   Status: Resolved.

   After reading the comments and the text of the draft plus the
   related text in draft-ietf-sasl-rfc2831bis-02.txt plus
   http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
   02.txt, I am inclined to agree with Alexey. In -07 I rewrote section
   3.3 (SASL mechanisms) to match the profiling requirements
   rfc2831bis. I then dramatically reduced the material in section 7.2
   to a bare minimum and let the SASL profile stand on its own.

G.42. Does change for G.41 cause interoperability issue?

   There is one issue with the way the authmeth draft is saying this.
   (Source: Alexey Melnikov email 8/1/2003 5:30:43 PM)

   Status: Resolved in -07. After reading currently
   written that changes the comments and SASL DIGEST-MD5 behavior on the text of way the draft, I believe that
   server responds with the subsequent authentication information .
   This has been documented in this should be clarified. The local policy
   used fashion since RFC 2829 (section
   6.1) was originally published and may cause an interoperability
   issue at this point if it changed to map follow the AuthNID DIGEST-MD5 spec (as
   it was in -07 of AuthMeth). Take this issue to the AuthZID in list.

   Status: Resolved

   (10/08/03) This item was discussed on the implicit case is
   sufficient WG list between 5/2/03 and that no additional verification is useful or needed.
   This text has been moved to apply only
   5/9/03. Consensus apppears to support the explicit assertion
   case.

G.41. Section 7.2 contains  unnecessary and misleading detail.

   " I am not sure why this section is required notion that RFC 2829 was
   in error and that the document.
   DIGEST-MD5 is defined in a separate document semantics of RFC 2831 are correct and there should
   be
   nothing magical about its usage reflected in LDAP. If authmeth. This is already the case as of the -07
   draft.

G.43. DIGEST-MD5 description
   creates confusion Realms recommendations for LDAP implementors, let's fix
   From http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
   02.txt: A protocol profile SHOULD provide a guidance how realms are
   to be constructed and used in the DIGEST-MD5
   document! Also, this section tries protocol and MAY further restrict
   its syntax and protocol-specific semantics."

   I don't believe that any such guidance exists within the LDAP TS.
   The most likely place for this to redefine DIGEST-MD5 behavior,
   which reside is explicitly prohibited by in the SASL specification."
   (Source: Alexey Melnikov: authmeth draft.

   Related email 8/1/2003 5:30:43 PM)

   Status: Resolved.

   After reading the comments and from Alexey Melnikov (8/4/2003 1:08:40 PM):

   "The problem I have with the text document is that it references realm
   without explaining what it is (or at least some examples of valid
   values). For LDAP, some recommendations should be given. For
   example:
   1). Use a hardcoded string as the draft plus the
   related text in draft-ietf-sasl-rfc2831bis-02.txt plus
   http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
   02.txt, I am inclined to agree with Alexey. In -07 I rewrote section
   3.3 (SASL mechanisms) to match realm (one of the profiling requirements
   rfc2831bis. implementations
   I then dramatically reduced the material worked on was doing that)
   2). Use hostname (realm==host) or domain/cluster name (realm
   includes multiple hosts).
   3). Use a node in section 7.2 DIT above user entry, for example for "cn=Barbara
   Jensen, ou=Accounting, o=Ace Industry, c=US"
    and "cn=John Doe, ou=Accounting, o=Ace Industry, c=US" realm can be
   "ou=Accounting, o=Ace Industry, c=US"
   (or "o=Ace Industry, c=US"); for "cn=Gern Jensen, ou=Product
   Testing,o=Ace Industry, c=US" realm can be "ou=Product Testing,
   o=Ace Industry, c=US".

   Of course other choices are possible.

   Alexey

   To summarize:  I'd like authmeth to define a bare minimum and let the SASL profile stand on its own.

G.42. Does change realm name for G.41 cause interoperability issue?

   There is one issue use with the way the authmeth draft is currently
   written
   Digest-MD5 that changes the SASL DIGEST-MD5 behavior on the way the
   server responds with the subsequent authentication corresponds to LDAP DNs known to this server.
   Authzid is okay, but perhaps could be better put into context.

   John  McMeeking (5/12/2003)

   Status: Resolved.

   draft-ietf-sasl-rfc2222bis-03.txt no longer requires this
   information .
   This has been documented in a SASL protocol. In addition, the ldapbis WG chairs
   have ruled this fashion since RFC 2829 (section
   6.1) was originally published and may cause an interoperability
   issue at this point if it changed work out of scope. Individuals are welcome to follow make
   submissions to provide guidance on the DIGEST-MD5 spec (as
   it was use of realm and realm values
   in -07 LDAP.

G.44. Use of AuthMeth). Take this issue to DNs in usernames and realms in DIGEST-MD5

   In reading the list.

   Status: Resolved
   (10/08/03) This item was discussed discussion on the WG list between 5/2/03 and
   5/9/03. Consensus apppears to support mailing list, I reach the notion that RFC 2829 was
   in error following
   conclusions:

   DIGEST-MD5 username and realm are simple strings. The syntax of
   these strings allows strings that look like DNs in form, however,
   DIGEST-MD5 treats them a simple strings for comparision purposes.
   For example, the semantics of RFC 2831 are correct DNs cn=roger, o=US and should cn=roger,o=us are equivalent
   when being compared semantically as DNs, however, these would be reflected
   considered two different username values in authmeth. This is already the case as of the -07
   draft.

G.43. DIGEST-MD5 Realms recommendations for LDAP

   From http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
   02.txt: A protocol profile SHOULD provide a guidance how realms because
   simple octet-wise semantics (rather than DN semantics) are used to
   compare username values in DIGEST-MD5. Ditto for realm values.

   Status: Resolved.

   In -07 revision I added notes to implementors expressing this issue
   in section 7.2.

G.45: Open Issue: Is Simple+TLS mandatory to implement?

   Going forward, it would be much better to clarify that simple
   +TLS is to be constructed and used in the protocol and MAY further restrict
   its syntax for DN/password credentials and protocol-specific semantics." DIGEST-MD5
   (or PLAIN+TLS) be used for username/password credentials. (Kurt
   Zeilenga, 5/12/2003)

   I don't believe that any such guidance exists within the LDAP TS.
   The most likely place for this to reside is in you can mandate simple/TLS! At the authmeth draft.

   Related email from Alexey Melnikov (8/4/2003 1:08:40 PM):

   "The problem I have with time RFC 2829 was
   debated, a large number on the document is that it references realm
   without explaining what it is (or at least some examples WG wanted this. They did not get
   their way because of valid
   values). For LDAP, some recommendations should be given. For
   example:
   1). Use a hardcoded string as the realm (one complexity of the implementations
   I worked on solution. It was doing that)
   2). Use hostname (realm==host) or domain/cluster name (realm
   includes multiple hosts).
   3). Use argued
   that a node in DIT above user entry, for example for "cn=Barbara
   Jensen, ou=Accounting, o=Ace Industry, c=US"
    and "cn=John Doe, ou=Accounting, o=Ace Industry, c=US" realm can password-based method would be
   "ou=Accounting, o=Ace Industry, c=US"
   (or "o=Ace Industry, c=US"); for "cn=Gern Jensen, ou=Product
   Testing,o=Ace Industry, c=US" realm can better. I think they believed
   it would still be "ou=Product Testing,
   o=Ace Industry, c=US".

   Of course other choices are possible.

   Alexey

   To summarize:  I'd like authmeth to define a realm name for DN/password, though. (Ron Ramsay, 5/12/2003)

   This was officially opened as an issue by WG co-chair Kurt Zeilenga
   on 5/12/03. Little direct discussion has occurred since, however
   there has been significant discussion on the use with
   Digest-MD5 of DN values as the
   username for DIGEST-MD5.

   Status: Resolved.

   Based on WG list discussion, Kurt Zeilenga has gaged a lack of WG
   consensus that corresponds to LDAP DNs known Simple+TLS should be mandatory to this server.
   Authzid implement. No
   further discussion is okay, but perhaps could necessary.

Intellectual Property Rights

   The IETF takes no position regarding the validity or scope of any
   intellectual property or other rights that might be better put into context.

   John  McMeeking (5/12/2003)

G.44. Use claimed to
   pertain to the implementation or use of DNs in usernames and realms the technology described in DIGEST-MD5

   In reading
   this document or the discussion extent to which any license under such rights
   might or might not be available; neither does it represent that it
   has made any effort to identify any such rights.  Information on the mailing list, I reach the following
   conclusions:

   DIGEST-MD5 username
   IETF's procedures with respect to rights in standards-track and realm are simple strings. The syntax of
   these strings allows strings that look like DNs
   standards-related documentation can be found in form, however,
   DIGEST-MD5 treats them a simple strings BCP-11.  Copies of
   claims of rights made available for comparision purposes.
   For example, the DNs cn=roger, o=US publication and cn=roger,o=us are equivalent
   when being compared semantically as DNs, however, these would any assurances
   of licenses to be
   considered two different username values in DIGEST-MD5 because
   simple octet-wise semantics (rather than DN semantics) are used made available, or the result of an attempt made
   to
   compare username values in DIGEST-MD5. Ditto obtain a general license or permission for realm values.

   Status: Resolved.

   In -07 revision I added notes the use of such
   proprietary rights by implementors or users of this specification
   can be obtained from the IETF Secretariat.

   The IETF invites any interested party to bring to its attention any
   copyrights, patents or patent applications, or other proprietary
   rights which may cover technology that may be required to implementors expressing practice
   this issue
   in section 7.2.

G.45: Open Issue: Is Simple+TLS mandatory standard.  Please address the information to implement?

   Going forward, the IETF Executive
   Director.

Full Copyright

   Copyright (C) The Internet Society (2003). All Rights Reserved.

   This document and translations of it would may be much better copied and furnished to clarify
   others, and derivative works that simple
   +TLS is to comment on or otherwise explain it
   or assist in its implementation may be used for DN/password credentials prepared, copied, published
   and DIGEST-MD5
   (or PLAIN+TLS) be used for username/password credentials. (Kurt
   Zeilenga, 5/12/2003)

   I don't believe you can mandate simple/TLS! At distributed, in whole or in part, without restriction of any
   kind, provided that the time RFC 2829 was
   debated, a large number above copyright notice and this paragraph
   are included on the WG wanted this. They did all such copies and derivative works. However, this
   document itself may not get
   their way because of the complexity of the solution. It was argued
   that a password-based method would be better. I think they believed
   it would still be DN/password, though. (Ron Ramsay, 5/12/2003)

   This was officially opened modified in any way, such as an issue by WG co-chair Kurt Zeilenga
   on 5/12/03. Little direct discussion has occurred since, however
   there has been significant discussion on removing
   the use of DN values copyright notice or references to the Internet Society or other
   Internet organizations, except as needed for the
   username purpose of
   developing Internet standards in which case the procedures for DIGEST-MD5.
   copyrights defined in the Internet Standards process must be
   followed, or as required to translate it into languages other than
   English.