INTERNET-DRAFT                                      Editor: R. Harrison
draft-ietf-ldapbis-authmeth-15.txt
draft-ietf-ldapbis-authmeth-16.txt                         Novell, Inc.
Obsoletes: 2829, 2830                                      August,                                     October, 2005
Intended Category: Standards Track

                      LDAP: Authentication Methods
                                  and
                  Connection Level
                          Security Mechanisms

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Copyright Notice

   Copyright (C) The Internet Society (2005).  All Rights Reserved.

Abstract

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

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

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

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

Table of Contents

   1. Introduction.....................................................3
   1.1. Relationship to Other Documents................................5
   1.2.Conventions.....................................................5
   2. Implementation Requirements......................................6
   3. StartTLS Operation...............................................7
   3.1. Sequencing of the StartTLS Operation...........................7
   3.1.1. StartTLS Request ............................................7
   3.1.2. StartTLS Response............................................8 Response............................................7
   3.1.3. Client Certificate...........................................8
   3.1.4. Discovery of Resultant Security Level........................8
   3.1.5. Server Identity Check........................................8
   3.1.5.1. Comparison of DNS Names....................................9
   3.1.5.2. Comparison of IP Addresses................................10
   3.1.5.3. Comparison of other subjectName types.....................10
   3.1.6. Refresh of Server Capabilities Information...................9 Information..................10
   3.2. Effect of TLS on Authorization State..........................10
   3.3. TLS Ciphersuites..............................................10
   4. Authorization State.............................................10
   4.1. Anonymous Authorization on Unbound Connections................11
   4.2. Anonymous Authorization After Failed Bind.....................11
   4.3. Invalidated Authorization State...............................11 State.............................................11
   5. Bind Operation..................................................11 Operation..................................................12
   5.1. Simple Authentication Choice..................................12
   5.2. SASL Authentication Choice....................................12
   6. Method..................................12
   5.1.1. Anonymous Authentication Mechanism of Simple Bind...............12
   7. Bind...........12
   5.1.2. Unauthenticated Authentication Mechanism of Simple Bind.........12
   8. Simple Bind.....13
   5.1.3. Name/Password Authentication Mechanism of Simple Bind .................13
   9. ......13
   5.2. SASL Authentication Method....................................14
   5.2.1. SASL Protocol Profile...........................................13
   9.1. Profile.......................................14
   5.2.1.1. SASL Service Name for LDAP....................................13
   9.2. LDAP................................14
   5.2.1.2. SASL Authentication Initiation and Protocol Exchange..........14
   9.3. Exchange......14
   5.2.1.3. Octet Where Negotiated Security Mechanisms Layers Take Effect........15
   9.4.
   5.2.1.4. Determination of Supported SASL Mechanisms....................15
   9.5. Mechanisms................16
   5.2.1.5. Rules for Using SASL Layers...................................15
   9.6 Layers...............................16
   5.2.1.6. Support for Multiple Authentications...........................16
   9.7.SASL Authorization Identities..................................16
   10. Authentications......................16
   5.2.1.7 SASL DIGEST-MD5 Authentication Mechanism.......................16
   11. Authorization Identities..............................16
   5.2.2. SASL EXTERNAL Authentication Mechanism.........................17
   11.1. Mechanism......................17
   5.2.2.1. Implicit Assertion...........................................17
   11.2. Assertion........................................17
   5.2.2.2. Explicit Assertion...........................................17
   12. Assertion........................................18
   6. Security Considerations........................................18
   12.1. Considerations.........................................18
   6.1. General LDAP Security Considerations.........................18
   12.2. Considerations..........................18
   6.2. Password-related Security Considerations.....................18
   12.2. Considerations......................19
   6.3. StartTLS Security Considerations.............................19
   12.3. Considerations..............................19
   6.4. Unauthenticated Mechanism Security Considerations............20
   12.4. Simple Mechanism Security Considerations.....................20
   12.5. SASL DIGEST-MD5 Considerations.............20
   6.5. Name/Password Mechanism Security Considerations............20
   12.6. Considerations...............20
   6.6. Related Security Considerations..............................20
   13. Considerations...............................20
   7. IANA Considerations............................................21
   Acknowledgments....................................................21 Considerations.............................................21
   8. Acknowledgments.................................................21
   9. Normative References...............................................21 References............................................21
   10. Informative References.............................................22 References.........................................22
   Author's Address...................................................23
   Appendix A. Authentication and Authorization Concepts..............23
   A.1. Access Control Policy.........................................23
   A.2. Access Control Factors........................................23
   A.3. Authentication, Credentials, Identity.........................23
   A.4. Authorization Identity........................................24
   Appendix B. Summary of Changes.....................................24
   Appendix B. RFC 2829 Change History................................24 History................................25
   Appendix C. RFC 2830 Change History................................28 History................................29
   Appendix D. RFC 2251 Change History................................28 History................................29
   Appendix E. Change History to Combined Document....................29
   Intellectual Property Rights.......................................44 Rights.......................................45

1. Introduction

   The Lightweight Directory Access Protocol (LDAP) [Roadmap] is a
   powerful protocol for accessing 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: include (but are not
   limited to):

   (1) Unauthorized access to directory data via data-retrieval
       operations.

   (2) Unauthorized access to directory data by monitoring access of
       others.

   (3) Unauthorized access to reusable client authentication
       information by monitoring access of others.

   (4) Unauthorized modification of directory data.

   (5) Unauthorized modification of configuration information,

   (6) Denial of Service: Use of resources (commonly in excess) in a
       manner intended to deny service to others.

   (7) Spoofing: Tricking a user or 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
       transport connection.  Tricking a user or client into sending
       privileged information to a hostile entity that appears to be
       the directory server but is not.  Tricking a directory server
       into believing that information came from a particular client
       when in fact it came from a hostile entity.

   (8) Hijacking: An attacker seizes control of an established protocol
       session.

   Threats (1), (4), (5), (6), (7) are (8) are active attacks.  Threats
   (2) and (3) are passive attacks.

   Threats (1), (4), (5) and (6) are due to hostile clients.  Threats
   (2), (3), (7) and (8) are due to hostile agents on the path between
   client and server or hostile agents posing as a server, e.g. IP
   spoofing.

   LDAP offers the following security mechanisms:

   (1) Authentication by means of the Bind operation.  The Bind
       operation provides a simple method which supports anonymous,
       unauthenticated, and authenticated-with-password name/password mechanisms, and the Secure
       Authentication and Security Layer (SASL) method which supports a
       wide variety of authentication mechanisms, mechanisms.

   (2) Mechanisms to support vendor-specific access control facilities
       (LDAP does not offer a standard access control facility) facility).

   (3) Data integrity service by means of security layers in TLS Transport
       Layer Security (TLS) or SASL mechanisms, mechanisms.

   (4) Data confidentiality service by means of security layers in TLS
       or SASL mechanisms, mechanisms.

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

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

   LDAP may also be protected by means outside the LDAP protocol, e.g.
   with IP-level security [RFC2401].

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

   Experience has shown that simply allowing implementations to pick
   and choose the security mechanisms that will be implemented is not a
   strategy that leads to interoperability.  In the absence of
   mandates, clients will continue to be written that do not support
   any security function supported by the server, or worse, they will
   support only clear text passwords that provide inadequate security
   for most circumstances.

   It is desirable to allow clients to authenticate using a variety of
   mechanisms including mechanisms where identities are represented as
   distinguished names [X.501][Models] in string form [LDAPDN] or are
   used in different systems (e.g. user name in string form).  Because
   some authentication mechanisms transmit credentials in plain text
   form
   form, and/or do not provide data security services, services and/or are
   subject to passive attacks, it is necessary to ensure secure
   interoperability by identifying a mandatory-to-
   implement mandatory-to-implement mechanism
   for establishing transport-layer security services.

   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 B 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 obsoletes RFC 2829.

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

1.2.Conventions

   The key words "MUST", "MUST NOT", "SHALL", "SHOULD", "SHOULD NOT",
   "MAY", and "OPTIONAL" in this document are to be interpreted as
   described in RFC 2119 [RFC2119].

   The term "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).

   The term "transport connection" refers to the underlying transport
   services used to carry the protocol exchange, as well as
   associations established by these services.

   The term "TLS layer" refers to TLS services used in providing
   security services, as well as associations established by these
   services.

   The term "SASL layer" refers to SASL services used in providing
   security services, as well as associations established by these
   services.

   The term "LDAP message layer" refers to the LDAP Message (PDU)
   services used in providing directory services, as well as
   associations established by these services.

   The term "LDAP session" refers to combined services (transport
   connection, TLS layer, SASL layer, LDAP message layer) and their
   associations.

   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 C A 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 C A before reading the remainder of this document.

2. Implementation Requirements

   LDAP server implementations MUST support the anonymous
   authentication mechanism of the simple bind Bind method (section 6). 5.1.1).

   LDAP implementations that support any authentication mechanism other
   than the anonymous authentication mechanism of the simple bind Bind
   method MUST support the DIGEST-MD5 [DIGEST-MD5] name/password authentication mechanism of SASL bind
   the simple Bind method (section
   10).  DIGEST-MD5 is a reasonably strong 5.1.2) and MUST be capable
   protecting this name/password authentication mechanism
   that provides (mandatory-to-implement) using TLS as
   established by the StartTLS operation (section 3).  Implementations
   SHOULD disallow the use of name/password authentication by default
   when suitable data security (data integrity
   and data confidentiality) services. are not in place.

   LDAP implementations SHOULD support the simple (DN and password) name/password
   authentication mechanism of the simple bind Bind method (section 8). 5.1.3).
   Implementations that support this authentication mechanism MUST be
   capable of protecting it using TLS as established by the StartTLS
   operation (section 3), SHOULD disallow the use of this
   authentication mechanism by default when suitable data security
   services are not in place, and MAY provide other suitable data
   security services for use with this authentication mechanism.

   Implementations MAY support additional authentication mechanisms.
   Some of these mechanisms are discussed below.

   LDAP server implementations SHOULD support client assertion of
   authorization identity via the SASL EXTERNAL mechanism (sections
   3.2.2 and 9). 5.2.1).

   LDAP server implementations that support no authentication mechanism
   other than the anonymous mechanism of the simple bind method SHOULD
   support use of TLS as established by the the StartTLS operation
   (section 3), and server implementations that do 3).  (Other servers MUST support TLS per the StartTLS
   operation second
   paragraph of this section.)

   Implementations supporting TLS MUST support the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA
   TLS_DHE_DSS_WITH_3DES_EBE_CBC_SHA ciphersuite.

3. StartTLS Operation

   The Start Transport Layer Security (StartTLS) operation defined in
   section 4.14 of [Protocol] provides the ability to establish TLS
   [TLS] on in an LDAP connection. session.

   The goals of using the TLS [TLS] protocol with LDAP are to ensure
   data confidentiality and integrity, and to optionally provide for
   authentication.  TLS expressly provides these capabilities, although
   the authentication services of TLS are available to LDAP only in
   combination with the SASL EXTERNAL authentication method (see
   section 11), 5.2.2), and then only if the SASL EXTERNAL implementation
   chooses to make use of the TLS credentials.

3.1. Sequencing of the StartTLS Operation

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

3.1.1. StartTLS Request

   A client may send the StartTLS extended request at any time after
   establishing an LDAP connection, session, except:

      - when TLS is currently established on the connection, session,
      - when a multi-stage SASL negotiation is in progress on the
        connection,
        session, or
      - when there are outstanding responses for operation requests
        previously issued on the connection. session.

   As described in [Protocol] Section 4.14.2.2, a (detected) violation
   of any of these requirements results in a return of the
   operationsError resultCode.

   Client implementers should ensure that they strictly follow these
   operation sequencing requirements to prevent interoperability
   issues.  Operational experience has shown that violating these
   requirements causes interoperability issues because there are race
   conditions that prevent servers from detecting some violations of
   these requirements due to server hardware speed, network latencies,
   etc.
   etc..

   There is no general requirement that the client have or have not
   already performed a Bind operation (section 4) before sending a
   StartTLS operation request. request, however where a client intends to
   perform both Bind operation and a StartTLS operation, it SHOULD
   first perform the StartTLS operation so that the Bind request and
   response messages is protected by the data security services
   established by the StartTLS operation.

3.1.2. StartTLS Response
   The server will return a resultCode other than success (as
   documented in [Protocol] section 4.13.2.2) 4.14.2) if it is unwilling or
   unable to negotiate TLS.  In this case the LDAP session is left
   without a TLS layer.

3.1.3. Client Certificate

   If an LDAP server requests or demands that a client provide its a user
   certificate during TLS negotiation and the client does not present a
   suitable user certificate (e.g. one that can be validated), the
   server may use a local security policy to determine whether to
   successfully complete TLS negotiation.

   If a client that has provided a suitable certificate subsequently
   binds
   performs a Bind operation using the SASL EXTERNAL authentication
   mechanism (section 9), 5.2.1), information in the certificate may
   subsequently be used by the server to identify and authenticate the
   client.

3.1.4. Discovery of Resultant Security Level

   After a TLS layer is established on a transport connection, in an LDAP session, both parties
   are to individually each independently decide whether or not to continue based on
   local policy and the security level achieved. The procedure for ascertaining the
   TLS layer's security level is implementation dependent.  If the client or server either party
   decides that the security level is not high
   enough inadequate for it to continue, it
   SHOULD gracefully remove the TLS
   connection layer immediately after the TLS negotiation
   (re)negotiation has completed (see [Protocol] section 4.13.3.1 4.14.3 and
   section 3.2.3 3.2 below).  The client  Implementations may then either close reevaluate the transport connection, attempt to StartTLS
   again, send an unbind request, or send security
   level at any other LDAP request. time and, upon finding it inadequate, should gracefully
   close the TLS layer.

3.1.5. Server Identity Check

   The

   In order to prevent man-in-the-middle attacks the client MUST check its understanding of the server's name against verify
   the server's identity as (as presented in the server's Certificate
   message in order
   message).  In this section, the client's understanding of the
   server's identity (typically the identity used to prevent man-in-the-middle attacks. establish the
   transport connection) is called the "reference identity".

   Matching is performed according to these rules:

     -

    1. The client MUST use determines the server type (ege. DNS name provided by or IP address) of
       the user (or
       other trusted entity) as reference identity and performs a comparison between the
       reference identity and each subjectAltName value to compare against of the server
       name as expressed in
       corresponding type until a match is produced.  Once a match is
       produced, the server's certificate. A server name
       derived from user input identity is to be considered provided by verified and the user
       only if derived in a secure fashion (e.g., DNSSEC).

     - If a subjectAltName extension of type dNSName server
       identity check is present complete.  Different subjectAltName types are
       matched in different ways.  The following sections explain how
       to compare various types of subjectAltName.

    2. If no match is produced in step 1, the
       certificate, it MUST be used as the source client may map the
       reference identity to a different type and repeat step 1 using
       subjectAltName values of that type.  Step 2 may be repeated for
       all available subjectAltName types to which the server's
       identity. Otherwise, if reference
       identity can be mapped, however the reference identity should
       only be mapped to types for which the mapping is either
       inherently secure, e.g. extracting the DNS name from a URI to
       compare with a subjectAltName extension of type
       iPAddress dNSName, or for which the
       mapping is present performed in a secure manner that is not subject to
       attack (e.g. using DNSSec, or using user- (or admin-) configured
       host-to-address/address-to-host lookup tables).

    3. If no match is produced after exhausting all appropriate
       subjectAltName values via step 2, the certificate it SHOULD server's identity may be used as
       verified by comparing the
       source reference identity to the Common Name
       value of the leftmost RDN of the subjectName field of the
       server's identity.  Implementations MAY support certificate.  This comparison is performed using the use
       comparison of other subjectAltName types as sources DNS names rules in section 3.1.5.1 below, with the
       exception that no wildcard matching is allowed.  Although the
       use of the server's
       identity.

     - Common Name is existing practice, it is deprecated
       and Certification Authorities are encouraged to provide
       subjectAltName values instead.

   If the server name provided by identity check fails, user-oriented clients SHOULD
   either notify the user (clients may give the user the opportunity to
   continue with the LDAP session in this case) or close the transport
   connection and indicate that the server's identity is suspect.
   Automated clients SHOULD close the transport connection and then
   return and/or log an error indicating that the server's identity is
   suspect.

   Beyond the server identity check 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 requested to provide.
   The client may need to make use of local policy information in
   making this determination.

3.1.5.1. Comparison of DNS Names

   If the reference identity is an internationalized domain name,
   conforming implementations MUST convert it to the ASCII Compatible
   Encoding (ACE) format as specified in section 4 of RFC 3490
   [RFC3490] before comparison with subjectAltName
       extensions values of type
   dNSName.  Specifically, conforming implementations MUST perform the
   conversion operation specified in section 4 of RFC 3490 as follows:

         * in step 1, the domain name SHALL be considered a "stored
           string";
         * in step 3, set the flag called "UseSTD3ASCIIRules";
         * in step 4, process each label with the "ToASCII"
           operation; and
         * in step 5, change all label separators to U+002E (full
           stop).

     -

   After performing the "to-ASCII" conversion, the DNS labels and names
   MUST be compared for equality according to the rules specified in
   section 3 of RFC3490.

   The "*" wildcard character is allowed in the server name
       provided by the user. subjectAltName values of
   type dNSName.  If present, it matches only the left-most label from
   the subjectAltName.  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.

     - When comparing DNS labels and names for equality, conforming
       implementations MUST perform matching according to the rules
       specified in section 3 of RFC 3490.

     - If more than one identity of a given type is present in the
       certificate (e.g. more than one dNSName name), a match with any
       one of the set is considered acceptable.

   If the server name 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 LDAP session in this case) or close the transport
   connection a.bar.com
   and indicate that b.bar.com, but it would not match a.x.bar.com nor would it match
   bar.com.

3.1.5.2. Comparison of IP Addresses

   When the server's reference identity is suspect.
   Automated clients SHOULD close the connection and then return and/or
   log an error indicating that IP address, the server's identity is suspect.

   Beyond MUST
   converted to the server identity checks described "network byte order" octet string representation
   [RFC791][RFC2460].  For IP Version 4, as specified in this section, clients
   SHOULD be prepared to do further checking to ensure that RFC 791, the server
   is authorized to provide
   octet string will contain exactly four octets.  For IP Version 6, as
   specified in RFC 2460, the service it octet string will contain exactly sixteen
   octets.  This octet string is requested to provide. The
   client then compared against subjectAltName
   values of type iPAddress.  A match occurs the reference identity
   octet string and value octet strings are identical.

3.1.5.3. Comparison of other subjectName types

   Client implementations may need to make use support matching against subjectAltName
   values of local policy information other types as described in making
   this determination. other documents.

3.1.6. Refresh of Server Capabilities Information

   Upon installing a TLS layer, the client SHOULD discard or refresh
   all information about the server it obtained prior to the initiation
   of the TLS negotiation and not obtained through secure mechanisms.
   This protects against man-in-the-middle attacks that may have
   altered any server capabilities information retrieved prior to TLS
   layer installation.

   The server may advertise different capabilities after installing a
   TLS layer.  In particular, the value of supportedSASLMechanisms may
   be different after a TLS layer has been installed (specifically, the
   EXTERNAL and PLAIN [PLAIN] mechanisms are likely to be listed only
   after a TLS layer has been installed).

3.2. Effect of TLS on Authorization State

   The decision to keep or invalidate establishment, change, and/or closure of TLS may cause the established
   authorization state (section 4.3) after TLS layer installation or removal is to move to a
   matter of local server policy. new state.  This is discussed
   further in Section 4.

3.3. TLS Ciphersuites

   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 transport
       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 confidentiality 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.

     - After TLS negotiation is completed, both protocol peers should
       independently verify that the security services provided by the
       negotiated ciphersuite are adequate for the intended use of the
       LDAP session.  If not, the TLS layer should be closed.

4. Authorization State
   Every State

   Every LDAP session has an associated authorization state.  This
   state is comprised of numerous factors such as what (if any)
   authorization identity has been established, how it was established,
   what security services are in place, etc..  Some factors may be
   determined and/or effected by protocol events (e.g., Bind, StartTLS,
   TLS closure), and some factors may be determined by external events
   (e.g., time of day, server load).

   While is often convenient to view authorization state in simplistic
   terms (as we often do in this technical specification) such as "an
   anonymous state", it is noted that authorization systems in LDAP
   implementations commonly involve many factors which interrelate in
   complex manners.

   Authorization in LDAP session has an associated is a local matter.  One of the key factors in
   making authorization state. decisions is authorization identity.  The Bind
   operation defined in section 4.2 of [Protocol] and discussed further
   in section 5 below allows information to be exchanged between the
   client and server to change the establish an authorization state of identity for the
   LDAP session.

4.1. Anonymous Authorization on Unbound Connections

   Prior to the completion of a  The Bind operation with a resultCode may also be used to move the LDAP
   session to an anonymous authorization state (see section 5.1.1).

   Upon initial establishment of
   success and during any subsequent authentication exchange, the LDAP session, the session has an
   anonymous authorization state. identity.  Among other things this implies
   that the client need not send a BindRequest in the first PDU of the
   LDAP message layer.  The client may send any operation request prior
   to binding, performing a Bind operation, and the server MUST treat it as if
   it had been performed after an anonymous bind Bind operation (section
   6). This authorization state is sometimes referred to as an implied
   anonymous bind.

4.2. Anonymous Authorization After Failed Bind
   5.1.1).

   Upon receipt of a Bind request, the LDAP server immediately moves the
   session is moved to an anonymous state and only upon completion of the authentication
   exchange (and authorization state.  If the Bind operation) with a resultCode of success request is
   successful, the LDAP session is moved to an authenticated state. Thus, a failed
   Bind operation produces the requested authentication
   state with its associated authorization state and identity.
   Otherwise, the session remains in an anonymous authorization state.

4.3. Invalidated Authorization State

   The server

   It is noted that other events both internal and external to LDAP may invalidate
   result in the existing authentication and authorization state at any
   time, e.g. if states being moved to
   an established security layer between anonymous one.  For instance, the client and
   server has unexpectedly failed establishment, change, or been compromised.  A resultCode
   closure of
   strongerAuthRequired security services may indicate that such a condition exists.  In
   practice, the strongerAuthRequired resultCode means that the client
   needs to bind to (re)establish result in a suitably strong authorization state
   before the server will attempt to perform the requested operation.
   In order to permit clients move to establish such an authorization anonymous
   state,
   servers should not respond to Bind, Unbind, and StartTLS requests
   with or the user's credential information (e.g., certificate) may
   have expired.  The former is an example of an event internal to LDAP
   whereas the stongerAuthRequired resultCode. latter is an example of an event external to LDAP.

5. Bind Operation

   The Bind operation ([Protocol] section 4.2) allows authentication
   information to be exchanged between the client and server to
   establish a new authorization state.

   The Bind request typically specifies the desired authentication
   identity.  Some Bind mechanisms also allow the client to specify the
   authorization identity.  If the authorization identity is not
   specified, the server derives it from the authentication identity in
   an implementation-specific manner.

   If the authorization identity is specified, the server MUST verify
   that the client's authentication identity is permitted to assume
   (e.g. proxy for) 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.

5.1. Simple Authentication Choice Method

   The simple authentication choice method of the Bind Operation provides
   three authentication mechanisms:

    1. An anonymous authentication mechanism (section 6), 5.1.1),

    2. An unauthenticated authentication mechanism (section 7), 5.1.2), and

    3. A simple name/password authentication mechanism using credentials
       consisting of a name (in the form of an LDAP distinguished name
       [LDAPDN]) and a password (section 8).

5.2. SASL Authentication Choice

   The sasl authentication choice of the Bind Operation provides
   facilities for using any SASL mechanism (sections 9-11) including
   authentication mechanisms and other services (e.g. data security
   services).

6. 5.1.3).

5.1.1. Anonymous Authentication Mechanism of Simple Bind
   An LDAP client may use the anonymous authentication mechanism of the
   simple Bind choice method to explicitly establish an anonymous
   authorization state by sending a Bind request with a name value of
   zero length and specifying the simple authentication choice
   containing a password value of zero length.

7.

5.1.2. Unauthenticated Authentication Mechanism of Simple Bind

   An LDAP client may use the unauthenticated authentication mechanism
   of the simple Bind choice method to establish an anonymous authorization
   state by sending a Bind request with a name value, a value (a distinguished
   name in LDAP string form [LDAPDN] of non-zero length, length) and specifying
   the the simple authentication choice containing a password value of zero
   length.

   The distinguished name value provided by the client is not used in to
   establish the authentication identity, but it may be used by the
   server for other purposes such as tracing.  Because no
   authentication of the distinguished name value is performed in this
   mechanism, it is non-authoritative, and it should be used in a
   manner consistent with this status.

   Unauthenticated binds Bind operations can have significant security issues
   (see section 12.3). 6.3).  Servers SHOULD by default reject unauthenticated bind
   Bind requests with a resultCode of invalidCredentials, and clients
   may need to actively detect situations where they would
   unintentionally make an unauthenticated bind Bind request.

8. Simple

5.1.3. Name/Password Authentication Mechanism of Simple Bind

   An LDAP client may use the simple name/password authentication mechanism of
   the simple Bind choice method to establish an authenticated authorization
   state by sending a Bind request with a name value, a value (a distinguished
   name in LDAP string form [LDAPDN] of non-zero length, length) and specifying
   the simple authentication choice containing an OCTET STRING password
   value of non-zero length.

   Servers that map the DN sent in the bind Bind request to a directory
   entry with an associated set of one or more passwords used with this
   mechanism will compare the presented password to that set of
   passwords. The presented password is considered valid if it matches
   any member of this set.

   A resultCode of invalidDNSyntax indicates that the DN sent in the
   name value is syntactically invalid.  A resultCode of
   invalidCredentials indicates that the DN is syntactically correct
   but not valid for purposes of authentication, or the password is not
   valid for the DN, or the server otherwise considers the credentials
   to be invalid.  A resultCode of success indicates that the
   credentials are valid and the server is willing to provide service
   to the entity these credentials identify.

   Server behavior is undefined for bind Bind requests specifying the simple
   name/password authentication mechanism with a zero-length name value
   and a password value of non-zero length.

   The simple name/password authentication mechanism of the simple bind Bind method
   is not suitable for authentication in environments without
   confidentiality protection.

9.

5.2. SASL Authentication Method

   The sasl authentication method of the Bind Operation provides
   facilities for using any SASL mechanism including authentication
   mechanisms and other services (e.g. data security services).

5.2.1. SASL Protocol Profile

   LDAP allows authentication via any SASL mechanism [SASL].  As LDAP
   includes native anonymous and simple name/password (plain text)
   authentication methods, the ANONYMOUS [ANONYMOUS] and 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.

9.1.

5.2.1.1. SASL Service Name for LDAP

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

9.2.

5.2.1.2. SASL Authentication Initiation and Protocol Exchange

   SASL authentication is initiated via a BindRequest message
   ([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 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 sending
   BindRequest messages multiple times.  A challenge is indicated by
   the server sending a BindResponse message with the resultCode set to
   saslBindInProgress.  This indicates that the server requires the
   client to send a new BindRequest message with the same sasl SASL
   mechanism to continue the authentication process.

   To the LDAP message layer, these challenges and responses are opaque
   binary tokens of arbitrary length.  LDAP servers use the
   serverSaslCreds field, an field (an OCTET STRING, STRING) in a BindResponse message to
   transmit each challenge.  LDAP clients use the credentials field, an field
   (an OCTET STRING, STRING) in the SaslCredentials sequence of a BindRequest
   message to transmit each response.  Note that unlike some Internet
   protocols where SASL is used, LDAP is not text based and does not
   Base64-transform these challenge and response values.

   Clients sending a BindRequest message with the sasl choice selected
   SHOULD send a zero-length value in the name field.  Servers
   receiving a BindRequest message with the sasl choice selected SHALL
   ignore any value in the name field.

   A client may abort a SASL bind Bind negotiation by sending a BindRequest
   message with a different value in the mechanism field of
   SaslCredentials or with 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 a
   resultCode of authMethodNotSupported.  This will allow the client t 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 BindResponse in which the resultCode
   value is not saslBindInProgress.

   The serverSaslCreds field in the BindResponse 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.  If a server does not
   intend to send a challenge in a BindResponse message, the server
   SHALL omit the serverSaslCreds field (rather than including the
   field with a zero-length value).

9.3.

5.2.1.3. Octet Where Negotiated Security Mechanisms Layers Take Effect

   SASL layers take effect following the transmission by the server and
   reception by the client of the final BindResponse in the SASL
   exchange with a resultCode of success.

   Once a SASL layer providing data 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 Bind operation that caused the new layer to take
   effect).  Thus, an established SASL layer is not affected by a
   failed or non-SASL Bind.

9.4.

5.2.1.4. Determination of Supported SASL Mechanisms

   Clients may determine the SASL mechanisms a server supports by
   reading the supportedSASLMechanisms attribute from the root DSE
   (DSA-Specific Entry) ([Models] section 5.1).  The values of this
   attribute, if any, list the mechanisms the server supports in the
   current LDAP session state.  LDAP servers SHOULD allow all clients--
   even those with an anonymous authorization--to retrieve the
   supportedSASLMechanisms attribute of the root DSE.

   Because SASL mechanisms provide critical security functions, clients
   and servers should be configurable to specify what mechanisms are
   acceptable and allow only those mechanisms to be used.  Both clients
   and servers must confirm that the negotiated security level meets
   their requirements before proceeding to use the connection.

9.5. session.

5.2.1.5. Rules for Using SASL Layers

   Upon installing a SASL layer, the client SHOULD discard or refresh
   all information about the server it obtained prior to the initiation
   of the SASL negotiation and not obtained through secure mechanisms.

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

9.6.

5.2.1.6. Support for Multiple Authentications

   LDAP supports multiple SASL authentications as defined in [SASL]
   section 6.3.

9.7.

5.2.1.7 SASL Authorization Identities

   Some SASL mechanisms allow clients to request a desired
   authorization identity for the LDAP session.  The decision to allow
   or disallow the current authentication identity to have access to
   the requested authorization identity is a matter of local policy
   ([SASL] section 4.2).  The authorization identity is a string of UTF-
   8
   UTF-8 [RFC3629] encoded [Unicode] characters corresponding to the
   following ABNF [RFC2234bis] grammar:

   authzId = dnAuthzId / uAuthzId
   ; distinguished-name-based authz id.
   dnAuthzId =  "dn:" distinguishedName

   ; unspecified authorization id, UTF-8 encoded.
   uAuthzId = "u:" userid
   userid = *UTF8    ; syntax unspecified

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

   The dnAuthzId choice is used to assert authorization identities in
   the form of a distinguished name to be matched in accordance with
   the distinguishedNameMatch matching rule [Syntaxes].  There is no
   requirement that the asserted distinguishedName value be that of an
   entry in the directory.

   The uAuthzId choice allows clients to assert an authorization
   identity that is not in distinguished name form.  The format of
   userid is defined as only as a sequence of UTF-8 [RFC3629] encoded
   [Unicode] characters, and any further interpretation is a local
   matter.  For example, the userid could identify a user of a specific
   directory service, be a login name, or be an email address.  A
   uAuthzId SHOULD NOT be assumed to be globally unique.  To compare
   uAuthzID values, each uAuthzID value MUST be prepared as a "query"
   string using [SASLPrep] and then the two values are compared octet-
   wise.

10. SASL DIGEST-MD5 Authentication Mechanism

   The SASL DIGEST-MD5 mechanism [DIGEST-MD5] provides client
   authentication with protection against passive eavesdropping attacks
   but does not provide protection against man-in-the-middle attacks.
   DIGEST-MD5 also provides data integrity and data confidentiality
   capabilities.

   Support for subsequent authentication ([DIGEST-MD5] section 2.2) is
   OPTIONAL in clients and servers.

   Implementers must take care to ensure that they maintain the
   semantics of the DIGEST-MD5 specification even when handling data
   that has different semantics in the LDAP protocol.
   For example, the SASL DIGEST-MD5 authentication mechanism utilizes
   realm and username values ([DIGEST-MD5] section 2.1) which are
   syntactically simple strings and semantically simple realm and
   username values. These values are not LDAP DNs, and there is no
   requirement that they be represented or treated be prepared as such. Username a "query"
   string using [SASLPrep] 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, then the two DNs <cn=Bob,dc=example,dc=com> (upper case "B") and
   <cn=bob,dc=example,dc=com> (lower case "b") values are equivalent when
   being compared semantically as LDAP DNs because the cn attribute octet-
   wise.

   The above grammar is
   defined to extensible.  The authzId production may be case insensitive, however the two values are not
   equivalent if they represent username values in DIGEST-MD5 because
   [SASLPrep] semantics are used
   extended to support additional forms of identities.  Each form
   distinguished by DIGEST-MD5.

11. its unique prefix (See 3.12 of [LDAPIANA] for
   registration requirements).

5.2.2. SASL EXTERNAL Authentication Mechanism

   A client can use the SASL EXTERNAL [SASL] mechanism to request the
   LDAP server to authenticate and establish a resulting authorization
   identity using security credentials exchanged by a lower 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 security layer, the SASL EXTERNAL bind Bind
   MUST fail with a resultCode of inappropriateAuthentication.
   Although this situation has the effect of leaving the LDAP session
   in an anonymous state (section 5), the state of any installed
   security layer is unaffected.

   A client may either request that its authorization identity be
   automatically derived from its authentication credentials exchanged
   at a lower security layer or it may explicitly provide a desired
   authorization identity.  The former is known as an implicit
   assertion, and the latter as an explicit assertion.

11.1.

5.2.2.1. Implicit Assertion
   An implicit authorization identity assertion is performed by
   invoking a Bind request of the SASL form using the EXTERNAL
   mechanism name that does not include the optional credentials field
   (found within the SaslCredentials sequence in the BindRequest).  The
   server will derive the client's authorization identity from the
   authentication identity supplied by a security layer (e.g., a public
   key certificate used during TLS layer installation) according to
   local policy.  The underlying mechanics of how this is accomplished
   are implementation specific.

11.2.

5.2.2.2. Explicit Assertion

   An explicit authorization identity assertion is performed by
   invoking a Bind request of the SASL form using the EXTERNAL
   mechanism name that includes the credentials field (found within the
   SaslCredentials sequence in the BindRequest).  The value of the
   credentials field, an octet string, field (an OCTET STRING) is the asserted authorization
   identity and MUST be constructed as documented in section 9.7.

12. 5.2.1.7.

6. Security Considerations

   Security issues are discussed throughout this document.  The
   unsurprising conclusion is that security is an integral and
   necessary part of LDAP.  This section discusses a number of LDAP-
   related security considerations.

12.1.

6.1. General LDAP Security Considerations

   LDAP itself provides no security or protection from accessing or
   updating the directory by other means than through the LDAP
   protocol, e.g. from inspection of server database files by database
   administrators.

   Sensitive data may be carried in almost any LDAP message and its
   disclosure may be subject to privacy laws or other legal regulation
   in many countries.  Implementers should take appropriate measures to
   protect sensitive data from disclosure to unauthorized entities.

   A connection session on which the client has not established data integrity and
   privacy services (e.g via StartTLS, IPSec or a suitable SASL
   mechanism) is subject to man-in-the-middle attacks to view and
   modify information in transit.  Client and server implementors
   SHOULD take measures to protect sensitive data in the LDAP session
   from these attacks by using data protection services as discussed in
   this document.  Clients and servers should provide the ability to be
   configured to require these protections.  A resultCode of
   confidentialityRequired indicates that the server requires
   establishment of (stronger) data confidentiality protection in order
   to perform the requested operation.

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

   Various security factors, including authentication and authorization
   information and data security services may change during the course
   of the LDAP session, or even during the performance of a particular
   operation.  Implementations should be robust in the handling of
   changing security factors.

12.2.

6.2. Password-related Security Considerations

   LDAP allows multi-valued password attributes.  In systems where
   entries are expected to have one and only one password,
   administrative controls should be provided to enforce this behavior.

   The use of clear text passwords and other unprotected authentication
   credentials is strongly discouraged over open networks when the
   underlying transport service cannot guarantee confidentiality.  LDAP
   implementations SHOULD NOT by default support authentication methods
   using cleartext clear text passwords and other unprotected authentication
   credentials unless the data on the connection session is protected using TLS or
   other data confidentiality and data integrity protection.

   The transmission of passwords in the clear--typically for
   authentication or modification--poses a significant security risk.
   This risk can be avoided by using SASL authentication [SASL]
   mechanisms that do not transmit passwords in the clear or by
   negotiating transport or session layer data confidentiality services
   before transmitting password values.

   To mitigate the security risks associated with the transfer of
   passwords, a server implementation that supports any password-based
   authentication mechanism that transmits passwords in the clear MUST
   support a policy mechanism that at the time of authentication or
   password modification, requires:

        A TLS layer has been successfully installed.

      OR

        Some other data confidentiality mechanism that protects the
        password value from eavesdropping has been provided.

      OR

        The server returns a resultCode of confidentialityRequired for
        the operation (i.e. simple bind name/password Bind with password value,
        SASL bind Bind transmitting a password value in the clear, add or
        modify including a userPassword value, etc.), even if the
        password value is correct.

12.2.

6.3. StartTLS Security Considerations

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

   The level of security provided though through the use of TLS depends
   directly on both the quality of the TLS implementation used and the
   style of usage of that implementation.  Additionally, a man-in-the-
   middle attacker can remove the StartTLS extended operation from the
   supportedExtension attribute of the root DSE.  Both parties SHOULD
   independently ascertain and consent to the security level achieved
   once TLS is established and before beginning use of the TLS
   connection. TLS-
   protected session.  For example, the security level of the TLS layer
   might have been negotiated down to plaintext.

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

   Server implementors SHOULD allow server administrators to elect
   whether and when data confidentiality and integrity are required, as
   well as elect whether authentication of the client during the TLS
   handshake is required.

   Implementers should be aware of and understand TLS security
   considerations as discussed in the TLS specification [TLS].

12.3.

6.4. Unauthenticated Mechanism Security Considerations

   Operational experience shows that clients can (and frequently do)
   misuse the unauthenticated authentication mechanism of the simple bind
   Bind method (see section 7). 5.1.2).  For example, a client program
   might make a decision to grant access to non-directory information
   on the basis of successfully completing a bind Bind operation.  LDAP
   server implementations may return a success response to an
   unauthenticated
   bind Bind request.  This may erroneously leave the client
   with the impression that the server has successfully authenticated
   the identity represented by the distinguished name when in reality,
   an anonymous authorization statehas been established.  Clients that
   use the results from a simple bind Bind operation to make authorization
   decisions should actively detect unauthenticated bind Bind requests (by
   verifying that the supplied password is not empty) and react
   appropriately.

12.4. Simple

6.5. Name/Password Mechanism Security Considerations

   The simple name/password authentication mechanism of the simple bind Bind method
   discloses the password to the server, which is an inherent security
   risk.  There are other mechanisms such as DIGEST-MD5 [[TODO: MECHANISM TBD]]
   that do not disclose the password to server.

12.5. SASL DIGEST-MD5 Mechanism Security Considerations

   The SASL DIGEST-MD5 mechanism is prone to the qop substitution
   attack, as discussed in 3.6 of [DIGEST-MD5].  The qop substitution
   attack can be mitigated (as discussed in 3.6 of [DIGEST-MD5]).

   The SASL DIGEST-MD5 mechanism [DIGEST-MD5] provides client
   authentication with protection against passive eavesdropping attacks
   but does not provide protection against man-in-the-middle attacks.

   Implementers should be aware of and understand DIGEST-MD5 security
   considerations as discussed in the DIGEST-MD5 specification [DIGEST-
   MD5].

12.6. server.

6.6. Related Security Considerations

   Additional security considerations relating to the various
   authentication methods and mechanisms discussed in this document
   apply and can be found in [SASL], [SASLPrep], [StringPrep] and
   [RFC3629].

13.

7. IANA Considerations

   The following IANA considerations apply to this document:

   It is requested that the IANA update the LDAP Protocol Mechanism
   registry to indicate that this document and [Protocol] provide the
   definitive technical specification for the StartTLS
   (1.3.6.1.4.1.1466.20037) extended operation.

   [[TODO: add any missing IANA Considerations.]]

8. Acknowledgments

   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. documents,
   which are products of the LDAP Extentions (LDAPEXT) Working Group.

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

9. Normative References

   [[Note to the RFC Editor: please replace the citation tags used in
   referencing Internet-Drafts with tags of the form RFCnnnn.]]

   [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.

   [RFC2119]    Bradner, S., "Key Words for use Mechanism", draft-ietf-sasl-
                rfc2831bis-xx.txt, a work in RFCs to Indicate
                Requirement Levels", BCP 14, RFC 2119, March 1997. progress.

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

   [LDAPIANA]   Zeilenga, K., "IANA Considerations for LDAP", draft-
                ietf-ldapbis-bcp64-xx.txt, (a work in progress).

   [Matching]   Hoffman, Paul and Steve Hanna, "Matching Text Strings
                in PKIX Certificates", draft-hoffman-pkix-stringmatch-
                xx.txt, a work in progress.

   [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.

   [RFC791]     Information Sciences Institute, "INTERNET PROTOCOL
                DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION", RFC
                791, September 1981.

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

   [RFC2234bis] Crocker, D., Ed. and P. Overell, "Augmented BNF for
                Syntax Specifications: ABNF", draft-crocker-abnf-
                rfc2234bis-xx, a work in progress.

   [RFC2460]    Deering, S., R. Hinden, "Internet Protocol, Version 6
                (IPv6)", RFC 2460, December 1998.

   [RFC3490]    Falstrom, P., P. Hoffman, and A. Costello,
                "Internationalizing Domain Names In Applications
                (IDNA)", RFC 3490, March 2003.

   [RFC3629]    Yergeau, F., "UTF-8, a transformation format of ISO
                10646", RFC 3629, STD 63, November 2003.

   [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] 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.

   [Unicode]    The Unicode Consortium, "The Unicode Standard, Version
                3.2.0" is defined by "The Unicode Standard, Version
                3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
                61633-5), as amended by the "Unicode Standard Annex
                #27: Unicode 3.1"
                (http://www.unicode.org/reports/tr27/) and by the
                "Unicode Standard Annex #28: Unicode 3.2"
                (http://www.unicode.org/reports/tr28/).

10. Informative References

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

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

   [RFC2829]    Wahl, M. et al, "Authentication Methods for LDAP", RFC
                2829, May 2000.

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

   [RFC2401]    Kent, S. and 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
   USA
   +1 801 861 2642
   roger_harrison@novell.com

Appendix A. Authentication and Authorization Concepts

   This appendix is non-normative.

   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.

A.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.  Security objects and
   mechanisms, such as those described here, enable the expression of
   access control policies and their enforcement.

A.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. etc..  Some
   factors may be specific to the request itself, others may be
   associated with the transport 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.  For example, "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.

A.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 a new authorization state 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.

A.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; for example, "entity
   X can perform operation Y on resource Z."

   The authorization identity of an LDAP session is often semantically
   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 B. Summary of Changes

   This appendix is non-normative.

   This appendix summarizes substantive changes made to RFC 2829 and
   RFC 2830.

   Changed LDAP's mandatory-to-implement "strong" authentication
   mechanism from SASL DIGEST-MD5 to the name/password mechanism
   protected by TLS (as discussed in section 2).  Implementatorsare
   encouraged to continue supporting SASL DIGEST-MD5 [RFC2829].

   [[TODO: complete this appendix.]]

Appendix B. RFC 2829 Change History

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

B.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.

B.1. Changes to Section 1

   Version -01

     - Moved conventions used in document to a separate section.

B.2. Changes to Section 2

   Version -01

     - Moved section to an appendix.

B.3. Changes to Section 3

   Version -01

     - Moved section to an appendix.

B.4 Changes to Section 4

   Version -00

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

B.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."

B.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.

B.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).

B.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

B.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."

B.6.3. Changes to section 6.3.

     Version -00

     - Renamed to section 6.4.

B.7. Changes to section 7.

   none

B.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."

B.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.

B.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.

B.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.

B.11. Changes to Section 11.

   Version -01

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

B.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.

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

   None

Appendix C. RFC 2830 Change History

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

C.0. General Editorial Changes

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

     - The wording of the definition of the StartTLS request and
       StartTLS 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 D. RFC 2251 Change History

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

D.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 StartTLS 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 E. Change History to Combined Document

E.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 Association State Transition Tables to show the various
       states through which an 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.

E.2. Changes for draft-ldapbis-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--H.13, H.14, H.16, H.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.

E.3. Changes for draft-ldapbis-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--H.13, H.14, H.16, H.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 Association State table for completeness and accuracy.
       Renumbered actions A3,  , 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 H.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.

E.4. Changes for draft-ldapbis-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 StartTLS 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 B.

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

E.5. Changes for draft-ldapbis-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 "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 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.

E.6. Changes for draft-ldapbis-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 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 StartTLS 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.

E.7. Changes for draft-ldapbis-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 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
     - 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 StartTLS 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

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

   Section 6.1
     - Clarified wording.
     - Added definition of anonymous and unauthenticated binds.

   Section 10

     - Added security consideration (moved from elsewhere) discouraging
       use of cleartext clear text passwords on unprotected communication
       channels.

   Section 11

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

E.8. Changes for draft-ldapbis-authmeth-09

   General

     - Updated section references within document
     - Changed reference tags to match other docs in LDAP TS
     - Used non-quoted names for all SASL 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 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 desirable to allow
       authentication methods to carry identities based on existing,
       non-LDAP DN-forms..."
     - Clarified relationship of this document to other documents in
       the LDAP TS.

   Section 3.3.5

     - 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 new paragraph indicating that clients and
       server should allow specification of acceptable mechanisms and
       only allow those mechanisms to be used.

     - Clarified independent behavior when TLS and SASL security layers
       are both in force (e.g. one being removed doesn't affect the
       other).

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

   Section 3.3.6.4

     - Moved some normative comments into text body.

   Section 4.1.2

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

   Section 4.2.1

     - Rewrote entire section based on WG feedback.

   Section 4.2.2

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

   Section 4.2.3

     - Rewrote entire section based on WG feedback.

   Section 5.1

     - Moved imperative language regarding unauthenticated access from
       security considerations to here.

   Section 6

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

   Section 6.2

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

   Section 10

     - Updated consideration on use of cleartext clear text passwords to include
       other unprotected authentication credentials
     - Substantial rework of consideration on misuse of unauthenticated
       bind.

E.9. Changes for draft-ldapbis-authmeth-10

     - Reorganized content of sections 3-9 to improve document flow and
       reduce redundancy.

     - Resolved issue of effect of Start TLS StartTLS and TLS closure on
       association state.
     - Made numerous minor wording changes based on WG feedback.
     - Updated list of threats for Section 1.
     - Recommendation that servers should not support weaker TLS
       ciphersuites unless other protection is in place.
     - Moved authentication state table to appendix and relettered
       appendices.

E.10. Changes for draft-ldapbis-authmeth-11

   General

     - Many editorial changes throughout to clarify wording and better
       express intent, primarily based on suggestions from WG mail
       list.
     - More standard naming of authentication mechanisms throughout
       document, e.g. "Anonymous Authentication Mechanism of the Simple
       Bind Choice".

   Section 1

     - Editorial changes to add clarity.
     - Moved section 2 of authmeth -09 into section 1

   Section 2

     - New section outlining implementation requirements.

   Section 3.1.1

     - Editorial clarification on need for following operation
       sequencing requirements.

   Section 3.1.4

     - New section added to describe use of client certificates with
       StartTLS. Incorporates material moved from other sections of
       authmeth -09.

   Section 4
     - New section added to discuss associations. Related material was
       moved from various other sections of authmeth -09 and
       incorporated into this new section.

   Section 5

     - Added several paragraphs regarding transmission and derivation
       of authentication and authorization identities using the Bind
       operation.

   Section 8
     - Clarified rules for determining valid credentials and situations
       where invalidCredentials result is to be returned.

   Section 14

     - Added three security considerations based on WG feedback.

   Appendix A

     - Simplfied state tables by removing two unnecessary actions from
       the actions table, and removing the current state column of the
       state transition table. Updated references to authmeth and
       [Protocol].

E.11. Changes for draft-ldapbis-authmeth-12

   General

     - Changed refererences from Start TLS to StartTLS.
     - Removed Appendix B: Example Deployment Scenarios
     - Removed Appendix H as all issues listed in the appendix are now
       resolved.

   Section 2

     - Added implementation requirement that server implementations
       that SUPPORT StartTLS MUST support the
       TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite.

   Section 3.1.2

     - Added wording clarifying that a client's association is
       unaffected if a non-success resultCode is returned in the
       StartTLS response.

   Section 9.2

     - Final paragraph of this section details requirements for
       serverSaslCreds field when no challenge value is sent.

   Section 10

     - Clarified language on uAuthzID usage.

   Section 12

     - Moved entire section into security considerations. New section
       number is 12.1.1.
     - Reorganized security considerations by topic.
     - Added several security considerations based on WG feedback.

   Section 13

     - Moved section to become section 3.3.

E.12. Changes for draft-ldapbis-authmeth-13

   General

     - General edits for clarity and to remove errors.
     - Reworded definition of association (section 1.2) and reworked
       usage of association throughout document. Current semantics:
       every connection has an association with the same lifetime as
       the connection, and that association passes through various
       authorization states.
     - Made usage of data confidentiality consistent throughout
       document.

   Section 1
     - Reworded mechanisms 3 and 4 for more parallelism.
     - Changed language on rationale for required mechanisms from
       future to past tense.

   Section 2
     - Clarified that implementations may support any additional
       authentication mechanism, not just mechanisms associated with
       simple and SASL bind choices.

   Section 3
     - Moved paragraph explaining goals for using TLS with LDAP from
       security considerations to here.

   Section 4.3
     - Reworked text to better explain meaning of strongAuthRequired
       resultCode when for invalidated associations.

   Section 8
     - Clarified action when simple bind request has a DN with invalid
       syntax.

   Section 12.1
     - Added ability to configure and enforce administrative service
       limits as a way to protect against denial of service attacks.

   Section 12.2
     - Clarified that this security consideration relates to performing
       client authentication during the TLS handshake and not to
       subsequent SASL EXTERNAL authentication.

   Appendix A
     - Updated tables by collapsing identical states and actions. Also
       added an invalidated association state and accompanying actions.

E.13. Changes for draft-ldapbis-authmeth-14

   General
     - Moved to standardized LDAP TS terms: transport connection, TLS
       layer, SASL layer, and LDAP message layer. Reworked usage of
       terminology throughout document to conform to latest usage.
     - Changed language on resultCode values to be less prescriptive
       and more descriptive.

   Section 1
     - Changed format and definitions of terms to parallel latest
       revision of [Protocol].

   Section 2
     - Updated implementation requirements for protecting LDAP simple
       bind mechanism to conform to WG consensus.

   Section 3.1.1
     - Moved last paragraph to security considerations and made
       generalized discussion of use of confidentialityRequired
       resultCode general for all data confidentiality services not
       just TLS.

   Section 3.1.4
     - Rewrote last paragraph to clarify that SASL EXTERNAL is a client
       action when server uses certificate information to derive
       authorization ID.

   Section 3.2
     - Collapsed three subsections into a single subsection. Removed
       text that implied that the TLS credentials were the only lower
       layer credentials that are used by SASL EXTERNAL in determining
       authentication ID and authorization ID.

   Section 8
     - Removed most of last paragraph that was redundant with
       implementation requirements in section 2.

   Section 10
     - Changed to SASL DIGEST-MD5 (was section 11 in -13 revision)

   Section 11
     - Changed to SASL EXTERNAL (was section 10 in -13 revision). Moved
       discussion of SASL authorization identities to Section 9.7.
       Clarified language around implicit and explicit assertion of
       authroization identities.

   Appendix A
     - Further collapsed identical states and actions continuing work
       in previous revisions.

E.14. Changes for draft-ldapbis-authmeth-15

   General
     - Resolved all known outstanding issues and comments for -14
       draft.
     - Replaced all usage of "LDAP assocation" with appropriate
       terminology basd on LDAP technical spec.
     - Edits for clarity and consistency.
     - Removed Section 3.1.3 of -14 draft on TLS version negotiation.
       (This is part of the TLS spec.)
     - Removed Section 3.3.1 of -14 draft on TLS ciphersuite
       recommendations.
     - Removed Appendix A - Association State Transition Tables

   Section 1
     - Updated some security terminology to be consistent with RFC
       2828.

   Section 3.1.2
     - Removed TLS operation details that are now covered in
       [Protocol].

   Section 3.1.5
     - Substantial edits to Server Identity Check. Most significant is
       the requirement that the check MUST be performed against a
       dNSName value if one is present in the subjectAltName of the
       server cert. Also added support for internationalized domain
       names.

   Section 4.3
     - Reworked entire section to clarify its intent. No changes to
       requirements.

   Section 7
     - Added clarification on usage of DN in unauthenticated mechanism.

   Section 9.2
     - Clarified cases where Base64 transforms are not needed for SASL
       challenges and responses. Also clarified use of the
       serverSaslCreds field in the BindResponse.

   Section 9.7
     - Simplified SASL authorization identity grammar.

   Section 12.1
     - Reworked several security considerations based on WG input.

E.15. Changes for draft-ldapbis-authmeth-16

   General

     - Resolved all known outstanding issues and comments for -15
       draft.
     - Numerous edits for clarity and consistency.
     - Renamed simple authentication mechanism to name/password
       mechanism.

     - Resolved some remaining issues with session/connection
       terminology
     - Replaced DIGEST-MD5 SASL authentication mechanism with
       name/password authentication protected with TLS as the "strong"
       mandatory-to-implement for LDAP.
     - Removed all normative references to SASL DIGEST-MD5 mechanism.
     - Moved sections on authentication mechanisms of the simple bind
       method into Simple Authentication Method.
     - Moved sections on SASL profile and SASL authentication
       mechanisms into section SASL Authentication Method section.

   Section 3.1.5
     - Rewrote server identity check algorithm.

   Section 4
     - Rewrote authorization state section.

   Section 5.1.2.7
     - Added text indicating the the authzID is an construct that can
       be extended by future publications.

   Appendix B
     - Began a new (and currently redundant) appendix to summarize
       substantive changes made to the protocol via this document. This
       appendix is currently unfinished.

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