WDIFF

draft-ietf-ldapbis-authmeth-11.txt --> draft-ietf-ldapbis-authmeth-12.txt

INTERNET-DRAFT Editor: R. Harrison
draft-ietf-ldapbis-authmeth-11.txt
draft-ietf-ldapbis-authmeth-12.txt Novell, Inc.
Obsoletes: 2829, 2830 July, August, 2004
Intended Category: Draft Standard

LDAP: Authentication Methods
and
Connection Level Security Mechanisms

Status of this Memo

This document is an Internet-Draft and is in full conformance with
all

By submitting this Internet-Draft, I accept the provisions of
Section 10 4 of RFC 3667. By submitting this Internet-Draft, I certify
that any applicable patent or other IPR claims of which I am aware
have been disclosed, and any of RFC2026. which I become aware will be
disclosed, in accordance with RFC 3668.

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

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Abstract

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

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

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

This document discusses various authentication and authorization
states through which a connection 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 Used in this Document..............................5 Document..............................6
1.2.1. Glossary of Terms............................................5 Terms............................................6
1.2.2. Security Terms and Concepts..................................6
1.2.3. Keywords.....................................................6
2. Implementation Requirements......................................6
3. Start TLS Operation..............................................7 StartTLS Operation...............................................7
3.1. Sequencing of the Start TLS Operation..........................7 StartTLS Operation...........................7
3.1.1. Start TLS StartTLS Request ...........................................7 ............................................7
3.1.2. Start TLS Response...........................................8 StartTLS Response............................................8
3.1.3. TLS Version Negotiation......................................8
3.1.4. Client Certificate...........................................8
3.1.5. Discovery of Resultant Security Level........................8
3.1.6. Server Identity Check........................................8 Check........................................9
3.1.7. Refresh of Server Capabilities Information...................9
3.2. Effects of TLS on a Client's Authorization Identity............9 Identity...........10
3.2.1. TLS Connection Establishment Effects........................10
3.2.2. Client Assertion of Authorization Identity..................10
3.2.3. TLS Connection Closure Effects..............................10
3.3. TLS Ciphersuites..............................................10
3.3.1. TLS Ciphersuites Recommendations............................11
4. LDAP Associations...............................................10 Associations...............................................12
4.1. Anonymous LDAP Association on Unbound Connections.............10
4.2 Connections.............12
4.2. Anonymous LDAP Association After Failed Bind...................10 Bind..................12
4.3. Invalidated Associations......................................11 Associations......................................12
5. Bind Operation .................................................11 Operation..................................................12
5.1. Simple Authentication Choice..................................11 Choice..................................13
5.2. SASL Authentication Choice....................................11 Choice....................................13
6. Anonymous Authentication Mechanism of Simple Bind...............12 Bind...............13
7. Unauthenticated Authentication Mechanism of Simple Bind.........12 Bind.........13

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8. Simple Authentication Mechanism of Simple Bind .................12 .................14
9. SASL Protocol Profile...........................................13 Profile...........................................14
9.1. SASL Service Name for LDAP....................................13 LDAP....................................14
9.2. SASL Authentication Initiation and Protocol Exchange..........13 Exchange..........15
9.3. Octet Where Negotiated Security Mechanisms Take Effect........14 Effect........16
9.4. Determination of Supported SASL Mechanisms....................15 Mechanisms....................16
9.5. Rules for Using SASL Security Layers..........................15

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9.6 Support for Multiple Authentications...........................15 Authentications...........................17
10. SASL EXTERNAL Mechanism........................................15 Mechanism........................................17
10.1. Implicit Assertion...........................................16 Assertion...........................................17
10.2. Explicit Assertion...........................................16 Assertion...........................................17
10.3. SASL Authorization Identity..................................16 Identity..................................17
10.4. SASL Authorization Identity Syntax...........................16 Syntax...........................18
11. SASL DIGEST-MD5 Mechanism......................................17 Mechanism......................................19
12. General Requirements for Password Handling.....................18
13. TLS Ciphersuites...............................................18
13.1. TLS Ciphersuites Recommendations.............................19
14. Security Considerations........................................20
14.1. Start TLS
12.1. General LDAP Security Considerations............................20
15. Considerations.........................20
12.1.1.Password-related Security Considerations....................21
12.2. StartTLS Security Considerations.............................22
12.3. Unauthenticated Mechanism Security Considerations............22
12.4. Simple Mechanism Security Considerations.....................23
12.5. SASL DIGEST-MD5 Mechanism Security Considerations............23
12.6. Related Security Considerations..............................23
13. IANA Considerations............................................21
Acknowledgments....................................................21 Considerations............................................23
Acknowledgments....................................................23
Normative References...............................................22 References...............................................24
Informative References.............................................23 References.............................................25
Author's Address...................................................23 Address...................................................25
Appendix A. LDAP Association State Transition Tables...............23 Tables...............25
A.1. LDAP Association States.......................................23 States.......................................25
A.2. Actions that Affect LDAP Association State....................24 State....................26
A.3. Decisions Used in Making LDAP Association State Changes.......24 Changes.......26
A.4. LDAP Association State Transition Table.......................24 Table.......................27
Appendix B. Example Deployment Scenarios...........................25
Appendix C. Authentication and Authorization Concepts..............26
C.1. Concepts..............27
B.1. Access Control Policy.........................................26
C.2. Policy.........................................28
B.2. Access Control Factors........................................26
C.3. Factors........................................28
B.3. Authentication, Credentials, Identity.........................26
C.4. Identity.........................28
B.4. Authorization Identity........................................27 Identity........................................28
Appendix D. C. RFC 2829 Change History................................27 History................................29
Appendix E. D. RFC 2830 Change History................................31 History................................33
Appendix F. E. RFC 2251 Change History................................32 History................................33
Appendix G. F. Change History to Combined Document....................32
Appendix H. Issues to be Resolved..................................43 Document....................33
Intellectual Property Rights.......................................57 Rights.......................................52

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.

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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:

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

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

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

(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
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, and

(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 mechanisms, and
the Secure Authentication and Security Layer (SASL) method which
supports a wide variety of authentication mechanisms,

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

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(3) Data integrity protection by means of TLS or SASL mechanisms
with security layers that provide data integrity protection,

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

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

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

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.

It seems clear that allowing implementations, faced with the above
requirements, to simply pick and choose among the possible
alternatives is not a strategy that is likely to lead to
interoperability. In the absence of mandates, clients will be
written that do not support any security function supported by the
server, or worse, they will support only 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
these authentication mechanisms transmit credentials in plain text
form and other authentication mechanisms do not provide data
security services, it is desirable to ensure secure interopability
by indentifying a 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.

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1.2. Conventions Used in this Document

1.2.1. Glossary of Terms

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

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

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

- "TLS connection" refers to a TLS-protected [TLS] an LDAP
connection.

- "association" and "LDAP connection with TLS
protection [TLS].

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

1.2.2. Security Terms and Concepts

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

1.2.3. Keywords

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

2. Implementation Requirements

LDAP server implementations MUST support the anonymous
authentication mechanism of simple bind (as discussed in Section 6).

LDAP implementations that support any authentication mechanism other
than the anonymous authentication mechanism of simple bind MUST
support the DIGEST-MD5 [DIGEST-MD5] mechanism of SASL bind (as
detailed in section 11). DIGEST-MD5 is a reasonably strong
authentication mechanism that provides (mandatory-to-implement) data
security (data integrity and data confidentiality) services.

LDAP impementations SHOULD support the simple (DN and password)
authentication mechanism of simple bind (as detailed in section 8).

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Implementations that support this mechanism MUST be capable of
protecting it by establishment of TLS (as discussed in section 3) or
other suitable suitable data confidentiality and data integrity
protection (e.g. IPSec).

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Implementations MAY support additional mechanisms of the simple and
SASL bind choices. 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).

LDAP server implementations SHOULD support the StartTLS operation,
and server implementations that do support the StartTLS operation
MUST support the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite.

3. Start TLS StartTLS Operation

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

3.1. Sequencing of the Start TLS 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 overall security of the LDAP
association including discovery of resultant security level and
assertion of the client's authorization identity.

Note that the precise effects, on a client's authorization identity,
of establishing TLS on an LDAP connection are described in detail in
section 3.2.

3.1.1. Start TLS StartTLS Request

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

- when TLS is currently established on the connection,
- when a multi-stage SASL negotiation is in progress on the
connection, or
- when it has not yet received responses for all operation
requests previously issued on the connection.

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

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these requirements due to server hardware speed, network latencies,
etc.

There is no general requirement that the client have or have not
already performed a Bind operation (section 4) before sending a
Start TLS
StartTLS operation request.

If the client did not establish a TLS connection before sending a
request and the server requires the client to establish a TLS

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connection before performing that request, the server MUST reject
that request by sending a resultCode of confidentialityRequired.

3.1.2. Start TLS StartTLS Response

The server will return an extended response with the resultCode of
success if it is willing and able to negotiate TLS.

It will return a resultCode other than success (documented in
[Protocol] section 4.13.2.2) if it is unwilling or unable to do so.
The client's current association is unaffected if a non-success
resultCode is returned.

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

3.1.3. TLS Version Negotiation

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

3.1.4. Client Certificate

In an LDAP server requests a client to provide its certificate
during TLS negotiation and the client does not present a suitablle
certifcate (e.g. one that can be validated), the server MAY use a
local security policy to determine whether to successfully complete
TLS negotiation.

If the client provides a certificate that can be validated,
information in the certificate may be used by the server in
establishing the client's authorization identity by use of the SASL
external mechanism as discussed in Section 9.

3.1.5. Discovery of Resultant Security Level

After a TLS connection is established on an LDAP connection, both
parties must individually decide whether or not to continue based on
the security level achieved. The procedure for ascertaining the TLS
connection's security level is implementation dependent.

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If the client or server decides that the security level is not high
enough for it to continue, it SHOULD gracefully close the TLS
connection immediately after the TLS negotiation has completed (see
[Protocol] section 4.13.3.1 and section 3.2.3 below). The client
may then close the connection, attempt to Start TLS StartTLS again, send an
unbind request, or send any other LDAP request.

3.1.6. Server Identity Check

The client MUST check its understanding of the server's hostname
against the server's identity as presented in the server's
Certificate message in order to prevent man-in-the-middle attacks.

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Matching is performed according to these rules:

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

- If a subjectAltName extension of type dNSName is present in the
certificate, it SHOULD be used as the source of the server's
identity.

- Matching is case-insensitive. The string values to be compared MUST be prepared according to
the rules described in [Matching].

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

For example, *.bar.com would match a.bar.com and b.bar.com, but
it would not match a.x.bar.com nor would it match bar.com. If
more than one identity of a given type is present in the
certificate (e.g. more than one dNSName name), a match in any
one of the set is considered acceptable.

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

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

3.1.7. Refresh of Server Capabilities Information

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Upon TLS session establishment, 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
establishment.

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

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

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

Authorization identities and related concepts are described in
Appendix C.

3.2.1. TLS Connection Establishment Effects

The decision to keep or invalidate the established LDAP association
(section 12) after TLS connection establishment is a matter of local
server policy.

3.2.2. Client Assertion of Authorization Identity

After successfully establishing a TLS session, a client may request
that its certificate exchanged during the TLS establishment be
utilized to determine the authorization identity of the LDAP
association. The client accomplishes this via an LDAP Bind request
specifying a SASL mechanism of EXTERNAL [SASL] (section 9).

3.2.3. TLS Connection Closure Effects

The decision to keep or invalidate the established LDAP association
after TLS closure is a matter of local server policy.

4. LDAP Associations

Every LDAP connection has an associated authentication and
authorization state referred to as

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 "LDAP association". following:

- The Bind
operation defined in section 4.2 of [Protocol] and discussed further
in section 5 below allows authentication information ciphersuite's ability to be exchanged
between the client provide adequate confidentiality
protection for passwords and server to set other data sent over the authentication and
authorization state LDAP
connection. Client and thus establish a new LDAP association.

4.1. Anonymous LDAP Association on Unbound Connections

Prior to the successful completion of a Bind operation and during
any subsequent authentication exchange, the session has an anonymous
LDAP association. Among other things this implies that the client
need not send a Bind Request in the first PDU of the connection. The
client may send any operation request prior to binding, and the server MUST treat it as if it had been performed after an anonymous
bind operation (section 6). This authentication state on an LDAP
association is sometimes referred to as an implied anonymous bind.

4.2 Anonymous LDAP Association After Failed Bind

Upon receipt of a Bind request, the LDAP association is moved to an
anonymous state and only upon successful completion of the implementers should recognize that
some TLS ciphersuites provide no confidentiality protection

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authentication exchange (and the Bind operation) is the association
moved

while other ciphersuites that do provide confidentiality
protection may be vulnerable to an authenticated state. Thus, a failed Bind operation
produces an anonymous LDAP association on being cracked using brute force
methods, especially in light of ever-increasing CPU speeds that
reduce the session.

4.3. Invalidated Associations

The time needed to successfully mount such attacks.

Client and server may invalidate the LDAP association at any time, e.g. if implementers should carefully consider the established security association between
value of the client and server
has unexpectedly failed password or been compromised. The association
remains invalidated until the next bind request. While data being protected versus the
association is invalidated, level
of confidentially protection provided by the server may reject any operation
request other than Bind, Unbind, and Start TLS by responding with a
resultCode of strongAuthRequired ciphersuite to indicate
ensure that the client needs
to bind to reestablish its authentication state before the server
will attempt to perform level of protection afforded by the requested operation. This behavior ciphersuite
is
explained here to help client implementers properly understand and
react to this situation.

5. Bind Operation appropriate.

- The Bind operation ([Protocol] section 4.2) allows authentication
information ciphersuite's vulnerability (or lack thereof) to be exchanged between the client and server man-in-the-
middle attacks. Ciphersuites vulnerable to
establish a new LDAP association.

The Bind request typically specifies the desired authentication
identity. Some Bind mechanisms also allow the client man-in-the-middle
attacks SHOULD NOT be used 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 protect passwords or sensitive
data, unless the authorization identity network configuration is specified the server MUST verify such that the client's authentication identity danger
of a man-in-the-middle attack is permitted tolerable.

3.3.1. TLS Ciphersuites Recommendations

[[TODO: Kurt will have someone from security to assume
(e.g. proxy for) the asserted authorization identity. The server
MUST reject the Bind operation with an invalidCredentials resultCode look at this and
will propose how to handle discussion of specific TLS ciphersuites
in this draft.]]

As of the Bind response if the client is not so authorized.

5.1. Simple Authentication Choice

The simple authentication choice writing of this document, the Bind Operation provides
three authentication mechanisms:

1. an anonymous authentication mechanism (section 6),

2. an unauthenticated authentication mechanism (section 7), and

3. a simple authentication mechanism using credentials consisting
of following recommendations
regarding TLS ciphersuites are applicable. Because circumstances are
constantly changing, this list must not be considered exhaustive,
but is hoped that it will serve as a name (in the form useful starting point for
implementers.

The following ciphersuites defined in [TLS] MUST NOT be used for
confidentiality protection of an LDAP distinguished name [LDAPDN])
and a password (section X).

5.2. SASL Authentication Choice passwords or data:

TLS_NULL_WITH_NULL_NULL
TLS_RSA_WITH_NULL_MD5
TLS_RSA_WITH_NULL_SHA

The sasl authentication choice following ciphersuites defined in [TLS] can be cracked easily
(less than a day of the Bind Operation provides
facilities CPU time on a standard CPU in 2000) and are NOT
RECOMMENDED for using any SASL mechanism (sections 9-11) including use in confidentiality protection of passwords or
data:

TLS_RSA_EXPORT_WITH_RC4_40_MD5
TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5
TLS_RSA_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA
TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA
TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA

The following ciphersuites are vulnerable to man-in-the-middle
attacks:

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TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
TLS_DH_anon_WITH_RC4_128_MD5
TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_anon_WITH_DES_CBC_SHA
TLS_DH_anon_WITH_3DES_EDE_CBC_SHA

4. LDAP Associations

Every LDAP connection has an associated authentication mechanisms and other services (e.g. data security
services).

6. Anonymous Authentication Mechanism of Simple Bind

An LDAP client may use
authorization state referred to as the anonymous authentication mechanism "LDAP association". The Bind
operation defined in section 4.2 of [Protocol] and discussed further
in section 5 below allows authentication information to be exchanged
between the
simple Bind choice client and server to explicitly set the authentication and
authorization state and thus establish an anonymous a new LDAP
association by sending association.

4.1. Anonymous LDAP Association on Unbound Connections

Prior to the successful completion of a Bind request with a name value of zero
length operation and with the simple authentication choice containing a
password value of zero length.

7. Unauthenticated Authentication Mechanism of Simple Bind

An LDAP client may use the unauthenticated during
any subsequent authentication mechanism
of exchange, the simple Bind choice to establish session has an anonymous
LDAP association
by sending association. Among other things this implies that the client
need not send a Bind request with a name value, a distinguished name Request in
LDAP string form [LDAPDN], of non-zero length, and specifying the the simple authentication choice containing a password value of zero
length.

Unauthenticated binds can have significant security issues (see
section 14). Servers SHOULD by default reject unauthenticated bind
requests with a resultCode first PDU of invalidCredentials, and clients the connection. The
client may
need send any operation request prior to actively detect situations where they would unintentionally
make binding, and the
server MUST treat it as if it had been performed after an unauthenticated anonymous
bind request.

8. Simple Authentication Mechanism of Simple Bind

An LDAP client may use the simple operation (section 6). This authentication mechanism of the
simple Bind choice to establish state on an authenticated LDAP
association by
sending a is sometimes referred to as an implied anonymous bind.

4.2. Anonymous LDAP Association After Failed Bind request with a name value,

Upon receipt of a distinguished name in Bind request, the LDAP string form [LDAPDN], association is moved to an
anonymous state and specifying only upon successful completion of the simple
authentication
choice containing an OCTET STRING password value of non-zero length.

Servers that map exchange (and the DN sent in Bind operation) is the bind request association
moved to an authenticated state. Thus, a directory
entry with failed Bind operation
produces an associated set of one or more passwords, will compare
the presented password to anonymous LDAP association on the set of passwords associated with that
entry. session.

4.3. Invalidated Associations

The presented password is considered valid if it matches server may invalidate the LDAP association at any
member of this set.

If time, e.g. if
the DN is not valid, established security association between the client and server
has unexpectedly failed or been compromised. The association
remains invalidated until the password is not valid for next bind request. While the DN, or
association is invalidated, the server otherwise considers may reject any operation
request other than Bind, Unbind, and StartTLS by responding with a
resultCode of strongAuthRequired to indicate that the credentials client needs
to be invalid, bind to reestablish its authentication state before the server is
will attempt to return perform the invalidCredentials result code. The server requested operation. This behavior is only
explained here to return success result code when the credentials are valid help client implementers properly understand and the server is willing
react to provide service this situation.

5. Bind Operation

The Bind operation ([Protocol] section 4.2) allows authentication
information to be exchanged between the entity these
credentials identify.

Server behavior is undefined for Bind requests with a zero-length
name value client and specifying the simple authentication choice with server to
establish a
value of non-zero length.

The simple authentication mechanism of simple bind is not suitable
for authentication in environments where there is no network or new LDAP association.

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transport layer confidentiality. LDAP implementations MUST be
capable of protecting it by establishment of TLS (as discussed in
section 3) or other suitable data confidentiality and data integrity
protection(e.g. IPSec). LDAP implementations
SHOULD support authentication with

The Bind request typically specifies the "simple" desired authentication
choice when
identity. Some Bind mechanisms also allow the connection client to specify the
authorization identity. If the authorization identity is protected against eavesdropping using
TLS, as defined not
specified, the server derives it from the authentication identity in section 4. LDAP implementations SHOULD NOT
support
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 "simple" Bind response if the client is not so authorized.

5.1. Simple Authentication Choice

The simple authentication choice
unless the data on of the connection is protected Bind Operation provides
three authentication mechanisms:

1. an anonymous authentication mechanism (section 6),

2. an unauthenticated authentication mechanism (section 7), and

3. a simple authentication mechanism using TLS or other
data confidentiality credentials consisting
of a name (in the form of an LDAP distinguished name [LDAPDN])
and data integrity protection.

9. a password (section X).

5.2. SASL Protocol Profile

LDAP allows Authentication Choice

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

6. Anonymous Authentication Mechanism of Simple Bind

An LDAP
includes native client may use the anonymous and simple (plain text) authentication
methods, mechanism of the ANONYMOUS [ANONYMOUS] and PLAIN [PLAIN] SASL mechanisms
are typically not used with LDAP.

Each protocol that utilizes SASL services is required
simple Bind choice 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. SASL Service Name for explicitly establish an anonymous LDAP

The SASL service
association by sending a Bind request with a name for LDAP is "ldap", which has been registered value of zero
length and with the IANA as simple authentication choice containing a GSSAPI service name.

9.2. SASL
password value of zero length.

7. Unauthenticated Authentication Initiation and Protocol Exchange

SASL Mechanism of Simple Bind

An LDAP client may use the unauthenticated authentication is initiated via mechanism
of the simple Bind choice to establish an anonymous LDAP bind association
by sending a Bind request
([Protocol] section 4.2) with the following parameters:

- The version is 3.
- The AuthenticationChoice is sasl.
- The mechanism element a name value, a distinguished name in
LDAP string form [LDAPDN], of non-zero length, and specifying the SaslCredentials sequence contains
the simple authentication choice containing a password value of the desired SASL mechanism.
- The optional credentials field zero
length.

Unauthenticated binds can have significant security issues (see
section 14). Servers SHOULD by default reject unauthenticated bind
requests with a resultCode of the SaslCredentials sequence invalidCredentials, and clients may be used

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need to provide actively detect situations where they would unintentionally
make an initial unauthenticated bind request.

8. Simple Authentication Mechanism of Simple Bind

An LDAP client response for
mechanisms that are defined to have may use the client send data first
(see [SASL] sections 5 and 5.1).

In general, a SASL simple authentication protocol exchange consists mechanism of a
series of server challenges and client responses, the contents of
which are specific
simple Bind choice to and defined establish an authenticated LDAP association by
sending a Bind request with a name value, a distinguished name in
LDAP string form [LDAPDN], and specifying the SASL mechanism. Thus for
some SASL simple authentication mechanisms, it may be necessary for
choice containing an OCTET STRING password value of non-zero length.

Servers that map the
client to respond DN sent in the bind request to a directory
entry with an associated set of one or more server challenges by invoking the
BindRequest multiple times. A challenge is indicated by passwords, will compare
the server
sending a BindResponse with presented password to the resultCode set to
saslBindInProgress. This indicates of passwords associated with that
entry. The presented password is considered valid if it matches any
member of this set.

If the DN is not valid, or the password is not valid for the DN, or
the server requires otherwise considers the
client credentials to send a new bind request with be invalid, the same sasl mechanism
server is to
continue return the authentication process.

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To invalidCredentials result code. The server
is only to return success result code when the LDAP protocol, these challenges and responses credentials are opaque
binary tokens of arbitrary length. LDAP servers use valid
and the
serverSaslCreds field, an OCTET STRING, in a bind response message server is willing to provide service to transmit each challenge. LDAP clients use the entity these
credentials field,
an OCTET STRING, in the SaslCredentials sequence of identify.

Server behavior is undefined for Bind requests with a bind request
message to transmit each response. Note that unlike some Internet
protocols where SASL is used, LDAP is not text-based, thus no Base64
transformati ons are performed on these challenge and response
values.

Clients sending a bind request with the sasl choice selected SHOULD
send an zero-length value in the
name field. Servers receiving a
bind request with the sasl choice selected SHALL ignore any value in and specifying the name field.

A client may abort a SASL bind negotiation by sending a BindRequest simple authentication choice with a different
value in the of non-zero length.

The simple authentication mechanism field of SaslCredentials, simple bind is not suitable
for authentication in environments where there is no network or
transport layer confidentiality. LDAP implementations MUST be
capable of protecting it by establish::qment of TLS (as discussed in
section 3) or
an AuthenticationChoice other than sasl.

If the client sends a BindRequest suitable data confidentiality and data integrity
protection(e.g. IPSec). LDAP implementations
SHOULD support authentication with the sasl mechanism field as
an empty string, "simple" authentication
choice when the server MUST return a BindResponse with
authMethodNotSupported connection is protected against eavesdropping using
TLS, as the resultCode. This will allow clients to
abort a negotiation if it wishes to try again defined in section 4. LDAP implementations SHOULD NOT
support authentication with the same SASL
mechanism.

The server indicates completion of "simple" authentication choice
unless the SASL challenge-response
exchange by responding with a bind response in which data on the resultCode connection is either success, protected using TLS or an error indication.

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

[[TODO: Some implementations send back a serverSaslCreds field with
zero length rather than just omitting it as part of the final bind
response. Some clients expect this present/zero-length behavior.
Need to provide clarification at this point of the document on what
behavior is expected and what servers confidentiality and clients should do to
promote interoperability when unexpected behavior occurs. This issue
is being taken up with the data integrity protection.

9. SASL WG. Likely outcome: both approaches
will be declared equivalent, servers will be advised to send back
present, zero-length field, clients will be advised to accept
either.]]

9.3. Octet Where Negotiated Security Mechanisms Take Effect Protocol Profile

LDAP allows authentication via any SASL security layers take effect following the transmission by the
server mechanism [SASL]. As LDAP
includes native anonymous and reception by the client of the final successful
BindResponse in simple (plain text) authentication
methods, the exchange.

Once a ANONYMOUS [ANONYMOUS] and PLAIN [PLAIN] SASL mechanisms
are typically not used with LDAP.

Each protocol that utilizes SASL security layer providing integrity or confidentiality services takes effect, the layer remains in effect until a new layer is installed (i.e. at required to supply
certain information profiling the first octet following way they are exposed through the final
protocol ([SASL] section 5). This section explains how each of these
profiling requirements are met by LDAP.

9.1. SASL Service Name for LDAP

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BindResponse of the bind operation that caused the new layer to take
effect). Thus, an established

The SASL security layer service name for LDAP is not affected
by "ldap", which has been registered
with the IANA as a failed or non-SASL Bind.

9.4. Determination of Supported GSSAPI service name.

9.2. SASL Mechanisms

Clients may determine the Authentication Initiation and Protocol Exchange

SASL mechanisms a server supports by
reading the supportedSASLMechanisms attribute from the root DSE
(DSA-Specific Entry) ([Models] authentication is initiated via an LDAP bind request
([Protocol] section 5.1). 4.2) with the following parameters:

- The values version is 3.
- The AuthenticationChoice is sasl.
- The mechanism element of this
attribute, if any, list the mechanisms the server supports in the
current LDAP session state. LDAP servers SHOULD allow an
anonymously-bound client to retrieve SaslCredentials sequence contains
the supportedSASLMechanisms
attribute value of the root DSE.

Because desired SASL mechanisms provide critical security functions, clients
and servers should mechanism.
- The optional credentials field of the SaslCredentials sequence
may be configurable used to specify what provide an initial client response for
mechanisms that are
acceptable and allow only those mechanisms defined to be used. Both clients have the client send data first
(see [SASL] sections 5 and servers must confirm that 5.1).

In general, a SASL authentication protocol exchange consists of a
series of server challenges and client responses, the negotiated security level meets
their requirements before proceeding contents of
which are specific to use and defined by the connection.

9.5. Rules for Using SASL Security Layers

If a mechanism. Thus for
some SASL security layer is negotiated, authentication mechanisms, it may be necessary for the
client SHOULD discard
information about the server it obtained prior to respond to one or more server challenges by invoking the initiation of
BindRequest multiple times. A challenge is indicated by the SASL negotiation and not obtained through secure mechanisms.

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

9.6 Support for Multiple Authentications

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

10. SASL EXTERNAL Mechanism

A
client can use to send a new bind request with the EXTERNAL SASL [SASL] same sasl mechanism to request
continue the authentication process.

To the LDAP server to authenticate protocol, these challenges 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]).

The resulting authentication identity responses are opaque
binary tokens of arbitrary length. LDAP servers use the
serverSaslCreds field, an OCTET STRING, in a bind response message
to transmit each challenge. LDAP association is
derived from clients use the security credentials in field,
an implementation-specific
manner. If OCTET STRING, in the client's authentication credentials have not been
established at SaslCredentials sequence of a lower security layer, the bind request
message to transmit each response. Note that unlike some Internet
protocols where SASL EXTERNAL is used, LDAP is not text-based, thus no Base64
transformations are performed on these challenge and response values.

Clients sending a bind MUST
fail request with a resultCode of inappropriateAuthentication. Although
this situation has the effect of leaving the LDAP association sasl choice selected SHOULD
send an zero-length value in the name field. Servers receiving a
bind request with the sasl choice selected SHALL ignore any value in
the name field.

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

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

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anonymous state (section 5), the state

The server indicates completion of any established security
layer the SASL challenge-response
exchange by responding with a bind response in which the resultCode
is unaffected.

A client may either implicitly request that its LDAP authorization
identity be derived from its authentication credentials exchanged at
a lower security layer success, or it may explicitly provide an authorization
identity and assert that it be used in combination with those
authentication credentials. error indication.

The former is known as an implicit
assertion, and serverSaslCreds field in the latter as BindResponse can be used to include
an explicit assertion.

10.1. Implicit Assertion

An implicit authorization identity assertion is performed by
invoking optional challenge with a Bind request of success notification for mechanisms
which are defined to have the SASL form using server send additional data along with
the EXTERNAL
mechanism name that indication of successful completion. If a server does not include intend
to send a challenge value in a BindResponse message, the optional credentials octet
string (found within server
SHALL omit the SaslCredentials sequence in serverSaslCreds field (rather than including the Bind
Request). The server will derive
field with a zero-length value).

9.3. Octet Where Negotiated Security Mechanisms Take Effect

SASL security layers take effect following the client's authorization identity
from transmission by the authentication identity supplied
server and reception by the client of the final successful
BindResponse in the exchange.

Once a SASL security layer
(e.g., providing integrity or confidentiality
services takes effect, the layer remains in effect until a public key certificate used during TLS establishment)
according to local policy. The underlying mechanics of how this new layer
is
accomplished are implementation specific.

10.2. Explicit Assertion

An explicit authorization identity assertion installed (i.e. at the first octet following the final
BindResponse of the bind operation that caused the new layer to take
effect). Thus, an established SASL security layer is performed not affected
by
invoking a Bind request failed or non-SASL Bind.

9.4. Determination of Supported SASL Mechanisms

Clients may determine the SASL form using mechanisms a server supports by
reading the EXTERNAL
mechanism name that includes supportedSASLMechanisms attribute from the credentials octet string. This
string MUST be constructed as documented in root DSE
(DSA-Specific Entry) ([Models] section 3.4.1.

10.3. SASL Authorization Identity

When the EXTERNAL SASL mechanism is being negotiated, 5.1). The values of this
attribute, if any, list the
SaslCredentials credentials field is present, it contains an
authorization identity. Other mechanisms define the location of the
authorization identity server supports in the credentials field. In either case,
current LDAP session state. LDAP servers SHOULD allow an
anonymously-bound client to retrieve the
authorization identity is represented in supportedSASLMechanisms
attribute of the authzId form described
below.

10.4. SASL Authorization Identity Syntax

The authorization identity 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. Rules for Using SASL Security Layers

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

If a string lower level security layer (such as TLS) is negotiated, any
SASL security services SHALL be layered on top of such security
layers regardless of UTF-8 [RFC3629] encoded
[Unicode] characters corresponding to the following ABNF [RFC2234]
grammar:

authzId = dnAuthzId / uAuthzId

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

; distinguished-name-based authz id.
dnAuthzId = DNCOLON distinguishedName

; unspecified authorization id, UTF-8 encoded.
uAuthzId = UCOLON userid order of their negotiation. In all other
respects, SASL security services and other security layers act
independently, e.g. if both TLS and SASL security service are in
effect then removing the SASL security service does not affect the
continuing service of TLS and vice versa.

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userid = *UTF8 ; syntax unspecified

where the <distinguishedName> production is

9.6 Support for Multiple Authentications

LDAP supports multiple SASL authentications as defined in [SASL]
section 3 of
[LDAPDN] 6.3.

10. SASL EXTERNAL Mechanism

A client can use the EXTERNAL SASL [SASL] mechanism to request the
LDAP server to authenticate and <UTF8> production is defined in section 1.3 of [Models].

In order to support additional specific establish a resulting authorization
identity
forms, future updates to this specification may add new choices
supporting other forms using security credentials exchanged by a lower security
layer (such as by TLS authentication or IP-level security
[RFC2401]).

The resulting authentication identity of the authzId production.

The dnAuthzId choice LDAP association is used to assert authorization identities in
derived from the form of a distinguished name to be matched security credentials in accordance with
the distinguishedNameMatch matching rule [Syntaxes]. The decision to
allow or disallow an implementation-specific
manner. If the client's authentication identity to credentials have access to not been
established at a lower security layer, the
requested authorization identity is SASL EXTERNAL bind MUST
fail with a matter resultCode of local policy ([SASL]
section 4.2). For inappropriateAuthentication. Although
this reason there is no requirement that situation has the
asserted dn be that effect of an entry leaving the LDAP association in an
anonymous state (section 5), the directory.

The uAuthzId choice allows for compatibility with clients state of any established security
layer is unaffected.

A client may either implicitly request that wish
to assert an its LDAP authorization
identity to be derived from its authentication credentials exchanged at
a directory but do not have
that lower security layer or it may explicitly provide an authorization
identity in distinguished name form. The value contained within
a uAuthzId MUST and assert that it be prepared using [SASLPrep] before being compared
octet-wise. used in combination with those
authentication credentials. The format of userid former is defined known as only a sequence of
UTF-8 [RFC3629] encoded [Unicode] characters, an implicit
assertion, and further
interpretation is subject to prior agreement between the client and
server.

For example, the userid could identify latter as an explicit assertion.

10.1. Implicit Assertion

An implicit authorization identity assertion is performed by
invoking a user Bind request of a specific
directory service or be a login name or the local-part of an RFC 822
email address. A uAuthzId SHOULD NOT be assumed to be globally
unique.

11. SASL DIGEST-MD5 Mechanism

LDAP servers that implement any authentication method or mechanism
other than simple anonymous bind MUST implement form using the SASL
DIGEST-MD5 EXTERNAL
mechanism [DIGEST-MD5]. This provides client
authentication with protection against passive eavesdropping attacks
but name that 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 include the
semantics of optional credentials octet
string (found within the DIGEST-MD5 specification even when handling data
that has different semantics SaslCredentials sequence in the LDAP protocol.
For example, Bind
Request). The server will derive the client's authorization identity
from 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 identity supplied by the security layer
(e.g., a public key certificate used during TLS establishment)
according to local policy. The underlying mechanics of how this is
accomplished are not LDAP DNs, and there implementation specific.

10.2. Explicit Assertion

An explicit authorization identity assertion is no
requirement performed by
invoking a Bind request of the SASL form using the EXTERNAL
mechanism name that they be represented or treated as such. Username
and realm values that look like LDAP DNs includes the credentials octet string. This
string MUST be constructed as documented in form, e.g. <cn=bob,
dc=example,dc=com>, are syntactically allowed, however DIGEST-MD5 section 3.4.1.

10.3. SASL Authorization Identity

When the EXTERNAL SASL mechanism is being negotiated, if the
SaslCredentials credentials field is present, it contains an
authorization identity. Other mechanisms define the location of the

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treats them as simple strings for comparison purposes. To illustrate
further,

authorization identity in the two DNs <cn=Bob,dc=example,dc=com> (upper case "B") and
<cn=bob,dc=example,dc=com> (lower case "b") are equivalent when
being compared semantically as LDAP DNs because credentials field. In either case, the cn attribute
authorization identity is
defined to be case insensitive, however the two values are not
equivalent if they represent username values in DIGEST-MD5 because
[SASLPrep] semantics are used by DIGEST-MD5.

12. General Requirements for Password Handling

The transmission of passwords represented in the clear--typically for
authentication or modification--poses a significant security risk.
This risk can be avoided by using authzId form described
below.

10.4. SASL authentication [SASL]
mechanisms that do not transmit passwords in the clear or by
negotiating transport or session layer confidentiality services
before transmitting password values.

To mitigate the security risks associated with the use of passwords,
a server implementation that supports any password-based
authentication mechanism MUST implement Authorization Identity Syntax

The authorization identity is a configuration that at the
time string of authentication or password modification, requires:

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

2) Some other confidentiality mechanism that protects UTF-8 [RFC3629] encoded
[Unicode] characters corresponding to the password
value from snooping has been provided.

3) The server returns a resultCode following ABNF [RFC2234]
grammar:

authzId = dnAuthzId / uAuthzId

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

; distinguished-name-based authz id.
dnAuthzId = DNCOLON distinguishedName

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

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

In order to support additional specific authorization identity
forms, future updates to this specification may add new choices
supporting other forms of confidentialityRequired for the operation (i.e. simple bind with password value, SASL bind
transmitting authzId production.

The dnAuthzId choice is used to assert authorization identities in
the form of a password value distinguished name to be matched in accordance with
the clear, add distinguishedNameMatch matching rule [Syntaxes]. The decision to
allow or modify
including a userPassword value, etc.), even if disallow an authentication identity to have access to the password
value
requested authorization identity is correct.

13. TLS Ciphersuites

A client or server implementation that supports TLS MUST support
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA. Servers SHOULD NOT support weaker
ciphersuites unless other data integrity and confidentiality
protection (such as a SASL security layer) matter of local policy ([SASL]
section 4.2). For this reason there is in place.

Several issues should no requirement that the
asserted dn be considered when selecting TLS ciphersuites that are appropriate for use of an entry in a given circumstance. These issues
include the following:

- directory.

The ciphersuite's ability uAuthzId choice allows clients to provide adequate confidentiality
protection for passwords and other data sent over the LDAP
connection. Client and server implementers should recognize that
some TLS ciphersuites provide no confidentiality protection
while other ciphersuites assert an authorization
identity that do provide confidentiality
protection may is not in distinguished name form. The format of
userid is defined as only a sequence of UTF-8 [RFC3629] encoded
[Unicode] characters, and any further interpretation is a local
matter. To compare uAuthzID values, each uAuthzID value MUST be vulnerable to being cracked
prepared using brute force [SASLPrep] and then the two values are compared
octet-wise.

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.

11. SASL DIGEST-MD5 Mechanism

LDAP servers that implement any authentication method or mechanism
other than simple anonymous bind MUST implement the SASL

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methods, especially in light of ever-increasing CPU speeds that
reduce the time needed to successfully mount such

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

Client
DIGEST-MD5 also provides data integrity and server implementers SHOULD carefully consider the
value of the password or data being protected versus the level
of confidentially protection provided by the ciphersuite 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 level
semantics 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 DIGEST-MD5 specification even when handling data
that has different semantics in the danger
of a man-in-the-middle attack is tolerable.

13.1. TLS Ciphersuites Recommendations

As of the writing of this document, LDAP protocol.
For example, the following recommendations
regarding TLS ciphersuites SASL DIGEST-MD5 authentication mechanism utilizes
realm and username values ([DIGEST-MD5] section 2.1) which are applicable. Because circumstances
syntactically simple strings and semantically simple realm and
username values. These values are
constantly changing, this list must not be considered exhaustive,
but LDAP DNs, and there is hoped no
requirement that it will serve as a useful starting point for
implementers.

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

TLS_NULL_WITH_NULL_NULL
TLS_RSA_WITH_NULL_MD5
TLS_RSA_WITH_NULL_SHA

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

The following ciphersuites are vulnerable to man-in-the-middle
attacks:

TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
TLS_DH_anon_WITH_RC4_128_MD5
TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_anon_WITH_DES_CBC_SHA
TLS_DH_anon_WITH_3DES_EDE_CBC_SHA

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14. Security Considerations

Security issues DNs in form, e.g. <cn=bob,
dc=example,dc=com>, are discussed throughout this memo; syntactically allowed, however DIGEST-MD5
treats them as simple strings for comparison purposes. To illustrate
further, the unsurprising
conclusion is that mandatory security is important two DNs <cn=Bob,dc=example,dc=com> (upper case "B") and that session
confidentiality protection is required
<cn=bob,dc=example,dc=com> (lower case "b") are equivalent when snooping
being compared semantically as LDAP DNs because the cn attribute is a problem.

Servers can minimize denial of service attacks by timing out idle
connections, and returning
defined to be case insensitive, however the unwillingToPerform resultCode rather
than performing computationally expensive operations requested two values are not
equivalent if they represent username values in DIGEST-MD5 because
[SASLPrep] semantics are used by
unauthorized clients. DIGEST-MD5.

12. Security Considerations

Security issues are discussed throughout this document. The use of cleartext passwords and other unprotected authentication
credentials
unsurprising conclusion is strongly discouraged over open networks when the
underlying transport service cannot guarantee confidentiality.

Operational experience shows that clients can (and frequently do)
misuse unauthenticated bind (see security is an integral and
necessary part of LDAP. This section 5.1). For example, a
client program might make discusses a decision to grant access to non-
directory information on the basis number of completing a successful bind
operation. Some LDAP-
related security considerations.

12.1. General LDAP server implementations will return a success
response to an unauthenticated bind thus leaving the client with the
impression that the server has successfully authenticated Security Considerations

LDAP itself provides no security or protection from accessing or
updating the
identity represented directory by other means than through the user name, when in effect, an anonymous LDAP association has been created. Clients that use the results
protocol, e.g. from
a simple bind operation to make authorization decisions should
actively detect unauthenticated bind requests (by verifying that the
supplied password is not empty) and react appropriately. inspection by database administrators. Access
control SHOULD always be applied when reading sensitive information
or updating directory information.

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

A connection on which the client has not established connection
integrity and privacy services (e.g via Start TLS, StartTLS, IPSec or a
suitable SASL mechanism) is subject to man-in-the-middle attacks to
view and modify information in transit.

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 by database administrators. Client and server
implementors SHOULD take measures to protect
credentials and other confidential data from
these attacks by using data protection services as discussed in this
document.

Additional security considerations relating to the various
authentication methods and mechanisms discussed in this document
apply and can be found in [DIGEST-MD5], [SASL], [SASLPrep],
[StringPrep], [TLS] and [RFC3629].

14.1. Start TLS Security Considerations

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

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(although the authentication services of TLS

12.1.1.Password-related Security Considerations

LDAP allows multi-valued password attributes. In systems where
entries are available expected to LDAP
only in combination with the SASL EXTERNAL authentication method, have one and then only if the SASL EXTERNAL implementation chooses one password,
administrative controls should be provided to make
use of the TLS credentials).

All security gained via enforce this behavior.

The use of the Start TLS operation clear text passwords and other unprotected authentication
credentials is gained by strongly discouraged over open networks when the use of TLS itself. The Start TLS operation, on its own, does not
provide any additional security.
underlying transport service cannot guarantee confidentiality.

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

To mitigate the quality of security risks associated with the TLS 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 StartTLS encryption layer has been successfully negotiated.

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

The server returns a resultCode of confidentialityRequired for
the operation (i.e. simple bind with password value, SASL 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. StartTLS Security Considerations

The goals of using the TLS [TLS] protocol with LDAP are to ensure
connection 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,
and then only if the SASL EXTERNAL implementation chooses to make
use of the TLS credentials).

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.

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The level of security provided though the use of TLS depends
directly on both the quality of the TLS implementation used and the
style of usage of that implementation. Additionally, an a man-in-the-
middle attacker can remove the Start TLS 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. For example, the security level of the TLS connection
might have been negotiated down to plaintext.

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

Server implementors SHOULD allow for server administrators to elect
whether and when connection data confidentiality and/or and integrity is are required, as
well as elect whether and when client authentication
via TLS authentication of the client is required.

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

15. IANA

12.3. Unauthenticated Mechanism Security Considerations

The following IANA considerations apply to this document:

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

[To be completed]

Acknowledgments

This document combines

Operational experience shows that clients can (and frequently do)
misuse the unauthenticated authentication mechanism of simple bind
(see section 7). For example, a client program might make a
decision to grant access to non-directory information originally contained in RFC 2829
and RFC 2830. The editor acknowledges on the work basis
of Harald Tveit
Alvestrand, Jeff Hodges, Tim Howes, Steve Kille, RL "Bob" Morgan , completing a successful bind operation. LDAP server
implementations will return a success response to an unauthenticated
bind request thus leaving the client with the impression that the
server has successfully authenticated the identity represented by
the user name, when in effect, an anonymous LDAP association has
been established. Clients that use the results from a simple bind
operation to make authorization decisions should actively detect
unauthenticated bind requests (by verifying that the supplied
password is not empty) and Mark Wahl, each of whom authored one or more react appropriately.

12.4. Simple Mechanism Security Considerations

The simple authentication mechanism of these documents.

This document simple bind discloses the
password to server, which is based upon input of an inherent security risk. There are
other mechanisms such as DIGEST-MD5 that do not disclose password to
server.

12.5. SASL DIGEST-MD5 Mechanism Security Considerations

The SASL DIGEST-MD5 mechanism is prone to the IETF LDAP Revision working
group. qop substitution
attack, as discussed in 6.2 of RFC 2831. The contributions and suggestions made by its members qop substitution
attack can be mitigated (as discussed in 6.2 of RFC 2831).

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.

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shaping the

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

12.6. 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. IANA Considerations

The following IANA considerations apply to this document:

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

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

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.

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

Normative References

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

[RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for
Syntax Specifications: ABNF", RFC 2234, November 1997.

[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 in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997.

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

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

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

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

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

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

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

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

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[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/).

Informative References

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

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

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

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[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. LDAP Association State Transition Tables

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

This section is based entirely on information found in this document
and other documents that are part of the LDAP Technical
Specification [Roadmap]. As such, it is strictly informational in
nature.

A.1. LDAP Association States

The following table lists the valid LDAP association states and
provides a description of each state. The ID for each state is used
in the state transition table in section A.4.

ID State Description

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-- --------------------------------------------------------------
S1 Anonymous
no Authentication ID is associated with the LDAP connection
no Authorization ID is in force
S2 Authenticated
Authentication ID = I
Authorization ID = X
S3 Authenticated SASL EXTERNAL, implicit authorization ID
Authentication ID = J
Authorization ID = Y
S4 Authenticated SASL EXTERNAL, explicit authorization ID Z
Authentication ID = J
Authorization ID = Z

A.2. Actions that Affect LDAP Association State

The following table lists the actions that can affect the
authentication and authorization state of an LDAP association. The
ID for each action is used in the state transition table in section
A.4.

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ID Action
-- --------------------------------------------------------------
A1 Client bind request fails
A2 Client successfully performs anonymous simple bind
A3 Client successfully performs unauthenticated simple bind
A4 Client successfully performs simple bind with name and password
OR SASL bind with any mechanism except EXTERNAL using an
authentication ID = I that maps to authorization ID X
A5 Client Binds SASL EXTERNAL with implicit assertion of
authorization ID (section 9.1)]. The current authentication ID
maps to authorization ID = Y.
A6 Client Binds SASL EXTERNAL with explicit assertion of
authorization ID = Z (section 9.2)]
A7 Client Start TLS StartTLS request fails
A8 Client Start TLS StartTLS request succeeds
A9 Client or Server: graceful TLS removal

A.3. Decisions Used in Making LDAP Association State Changes

Certain changes in the authentication and authorization state of an
LDAP association are only allowed if the server can affirmatively
answer a question. These questions are applied as part of the
criteria for allowing or disallowing a state transition in the state
transition table in section A.4.

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

A.4. LDAP Association State Transition Table

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The LDAP Association table below lists the the actions that could
affect authentication and authorization state of an LDAP association
and the resulting state of an LDAP association after a given action
occurs.

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

Next
Action State Comment
------- ----- -------------------------------------------------
A1 S1 Section 4
A2 S1 Section 6
A3 S1 Section 7
A4 S2 Sections 8, 9
A5, S1 Failed bind, section 10.1
D1=no
A5, S3
D1=yes

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A6, S1 Failed bind, section 10.2
D1=no
A6, S1 Failed bind, section 10.2
D1=yes,
D2=no
A6, S4
D1=yes,
D2=yes
A7 no [Protocol] section 4.14.2.2
change
A8 no [Protocol] section 4.14.2.1
change
A9 S1 [Protocol] section 4.14.3.1

Appendix B. Example Deployment Scenarios
The following scenarios are typical for LDAP directories on the
Internet, and have different security requirements. (In the
following discussion, "sensitive data" refers to information whose
disclosure, alteration, destruction, or loss would adversely affect
the interests or business of its owner or user. Also note that there
may be data that is protected but not sensitive.) This is not
intended to be a comprehensive list; other scenarios are possible,
especially on physically protected networks.

(1) A read-only directory, containing no sensitive data, accessible
to "anyone", and TCP connection hijacking or IP spoofing is not
a problem. Anonymous authentication, described in section 7, is
suitable for this type of deployment, and requires no additional
security functions except administrative service limits.

(2) A read-only directory containing no sensitive data; read access
is granted based on identity. TCP connection hijacking is not

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currently a problem. This scenario requires data confidentiality
for sensitive authentication information AND data integrity for
all authentication information.

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

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

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

Appendix C. Authentication and Authorization Concepts

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

C.1.

B.1. Access Control Policy

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

C.2.

B.2. Access Control Factors

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

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

C.3.

B.3. Authentication, Credentials, Identity

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

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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.

C.4.

B.4. Authorization Identity

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

The authorization identity bound to an association is often exactly
the same as the authentication identity presented by the client, but
it may be different. SASL allows clients to specify an authorization
identity distinct from the authentication identity asserted by the
client's credentials. This permits agents such as proxy servers to
authenticate using their own credentials, yet request the access
privileges of the identity for which they are proxying [SASL]. Also,
the form of authentication identity supplied by a service like TLS
may not correspond to the authorization identities used to express a
server's access control policy, requiring a server-specific mapping
to be done. The method by which a server composes and validates an
authorization identity from the authentication credentials supplied
by a client is implementation-specific.

Appendix D. C. RFC 2829 Change History

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

D.0.

C.0. General Editorial Changes
Version -00

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

- Miscellaneous grammatical changes to improve readability.

- Made capitalization in section headings consistent.

Version -01

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

D.1.

C.1. Changes to Section 1

Version

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Version -01

- Moved conventions used in document to a separate section.

D.2.

C.2. Changes to Section 2

Version -01

- Moved section to an appendix.

D.3.

C.3. Changes to Section 3

Version -01

- Moved section to an appendix.

D.4

C.4 Changes to Section 4

Version -00

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

D.5.

C.5. Changes to Section 5

Version -00

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

D.5.1.

C.5.1. Changes to Section 5.1

Version -00

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

Version -01

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

D.6.

C.6. Changes to Section 6.

Version -00

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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 paragra phs for section 6 into
section 6.1. Added sentences to the paragraph indicating:

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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).

D.6.1.

C.6.1. Changes to Section 6.1.

Version -00 Renamed section to 6.2

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

D.6.2.

C.6.2. Changes to Section 6.2

Version -00

- Renamed section to 6.3

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

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

- Added Section 6.3.1 heading just prior to paragraph 5.

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

D.6.3.

C.6.3. Changes to section 6.3.

Version -00

- Renamed to section 6.4.

D.7.

C.7. Changes to section 7.

none

C.7.1. Changes to section 7.1.

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none

D.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."

D.8.

C.8. Changes to section 8.

Version -00

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

- Added section 8.1. heading just prior to second paragraph.

- Added section 8.2. heading just prior to third paragraph.

- Added section 8.3. heading just prior to fourth paragraph.

Version -01

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

D.9.

C.9. Changes to section 9.

Version -00

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

- Added section 9.1. heading.

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

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

- Added section 9.1.1. heading.

- Added section 9.1.2. heading.

Version -01

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

C.10. Changes to Section 10.

Version -00

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D.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.

D.11.

C.11. Changes to Section 11.

Version -01

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

D.12.

C.12. Changes to Section 12.

Version -00

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

Version -01

- Moved to section 3.7 to be with other SASL material.

D.13.

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

None

Appendix E. D. RFC 2830 Change History

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

E.0.

D.0. General Editorial Changes

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

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

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

Appendix F. E. RFC 2251 Change History

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

F.0.

E.0. General Editorial Changes

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

- A new section was created for the Bind Request

- Section 4.2.1 of RFC 2251 (Sequencing Bind Request) was moved
after the section on the Bind Response for parallelism with the
presentation of the Start TLS 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 G. F. Change History to Combined Document

G.1.

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

General

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

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

Section 1.

- Added glossary of terms and added sub-section headings

Section 2.

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

Section 3.

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

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

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

- Rewrote paragraph on SASL negotiation requirements to clarify
intent

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Section 4.4.

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

Section 5.3.6

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

Section 6

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

Appendix A

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

G.2.

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

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- 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.

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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.

G.3.

F.3. Changes for draft-ldap-bis-authmeth-04 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 LDAP Association State table for completeness and
accuracy. Renumbered actions A3, A4, and A5 to be A5, A3, and A4
respectively. Re-ordered several lines in the table to ensure
that actions are in ascending order (makes analyzing the table
much more logical). Added action A2 to several states where it

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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

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- 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.

G.4.

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

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- 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..."

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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.

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Section 11.

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

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Appendix B.

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

G.5.

F.5. Changes for draft-ldap-bis-authmeth-06 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 "LDAP association" and added terms,
"connection" and "TLS connection" to bring usage in line with
[Protocol].

Section 4.1.6

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

Section 5.1

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

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

Section 7.2

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

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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.

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Section 10

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

G.6.

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

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- 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.

G.7.

F.7. Changes for draft-ldap-bis-authmeth-08 draft-ldapbis-authmeth-08

General

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

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

Abstract

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

Section 2.1

- New definition of user.

Section 3

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

Section 3.1

- Retitled section and clarified wording

Section 3.2

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

Section 3.3.3

- 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.

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Section 3.4

- Minor clarifications in wording.

Section 3.4.1

- Minor clarifications in wording in first sentence.

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

Section 4.1.1

- Simplified wording describing conditions when Start TLS 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 passwords on unprotected communication
channels.

Section 11

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

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G.8. Changes for draft-ldap-bis-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.

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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 passwords to include
other unprotected authentication credentials
- Substantial rework of consideration on misuse of unauthenticated
bind.

G.9. Changes for draft-ldap-bis-authmeth-10

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

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- 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
Start TLS. Incorporates material moved from other sections of
authmeth -09.

Section 4
- New section added to discuss LDAP 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].

Appendix H. Issues to be Resolved

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

H.1.

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

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

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H.2.

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

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

H.3.

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

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

H.4.

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

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

H.5.

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

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

H.6.

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

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

H.7.

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

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

H.8.

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

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

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

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

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

H.9.

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

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

H.10 userPassword and simple bind

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

H.11. Meaning of LDAP Association

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

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

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

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

"6.2. Digest authentication

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

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

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

H.13. Ordering of authentication levels requested

Again on the subject of authentication level, is it possible to
define an ordering on authentication levels which defines their
relative "strengths" ? This would be useful in acl as you could say
things like"a given aci grants access to a given subject at this
authentication level AND ABOVE". David Chadwick raised this before

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in the context of denying access to a subject at a given
authentication level, in which case he wanted to express "deny
access to this subject at this authentication level AND TO ALL
IDENTITIES AUTHENTICATED BELOW THAT LEVEL". (Source: Rob Byrne)

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

H.14. Document vulnerabilities of various mechanisms

While I'm here...in 2829, I think it would be good to have some
comments or explicit reference to a place where the security
properties of the particular mandatory authentication schemes are
outlined. When I say "security properties" I mean stuff like "This
scheme is vulnerable to such and such attacks, is only safe if the
key size is > 50, this hash is widely considered the best, etc...".
I think an LDAP implementor is likely to be interested in that
information, without having to wade through the security RFCs.
(Source: Rob Byrne)

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

H.15. Include a Start TLS state transition table

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

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

(Source: Jeff Hodges)

Status: Resolved.

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

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

H.16. Empty sasl credentials question

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

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

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

H.17. Hostname check from MUST to SHOULD?

I am uneasy about the hostname check. My experience from PKI with
HTTP probably is a contributing factor; we have people using the
short hostname to get to a server which naturally has the FQDN in
the certificate, no end of problems. I have a certificate on my
laptop which has the FQDN for the case when the system is on our
Columbia network with a fixed IP; when I dial in however, I have
some horrible dialup name, and using the local https server becomes
annoying. Issuing a certificate in the name 'localhost' is not a
solution! Wildcard match does not solve this problem. For these
reasons I am inclined to argue for 'SHOULD' instead of
'MUST' in paragraph...

Also, The hostname check against the name in the certificate is a
very weak means of preventing man-in-the-middle attacks; the proper
solution is not here yet (SecureDNS or some equivalent). Faking out
DNS is not so hard, and we see this sort of thing in the press on a
pretty regular basis, where site A hijacks the DNS server for site B
and gets all their requests. Some mention of this should be made in
the draft. (Source: ariel@columbia.edu via Jeff Hodges)

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

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

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

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

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

(11/21/02) Feedback from mailing list has proposed removing this
paragraph entirely because (1) explicit assertion of authorization
identity should only be done when proxying (2) mapping of the
asserted authorization identity is implementation specific and

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policy driven [SASL] section 4.2, and (3) keeping this paragraph is
not required for interoperability.

H.19. DN used in conjunction with SASL mechanism

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

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

H.20. Bind states

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

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

H.21. Misuse of unauthenticated access

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

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

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

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

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

Status: Resolved. Changes made in -04

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

Status: Resolved.

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

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

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

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

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

Status: Resolved.

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

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

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

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

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

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

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

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

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

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

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

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

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

H.28 Ordering of external sources of authorization identities

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

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

H.29 Rewrite of Section 9, TLS Ciphersuites

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

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

H.30 Update to Appendix A, Example Deployment Scenarios

This section needs to be updated to indicate which security
mechanisms and/or combinations of security mechanisms described

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elsewhere in the document can provide the types of protections
suggested in this appendix.

H.31 Use of PLAIN SASL Mechanism

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

Status: Resolved.

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

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

H.32 Clarification on use of SASL mechanisms

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

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

Status: Resolved.

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

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

Section 3.3.1: "If an authorization identity of a form different
from a DN is requested by the client, a mechanism that protects the

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password in transit SHOULD be used." What has that to do with DNs?
A mechanism that protects the password in transit should be used in
any case, shouldn't it?

Status: Resolved.

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

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

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

H.35 Requested Additions to Security Considerations

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

Requested to mention denial of service attacks.

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

(Source: Hallvard Furuseth)

H.36 Add reference to definition of DIGEST-MD5

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

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

H.37 Clarification on procedure for certificate-based authentication

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

Status: Resolved. In -10 this text has been absorbed into the SASL
EXTERNAL mechanism section.

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H.38 Effect of Start TLS on authentication state

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

Status: Resolved. In -09 the effect on an LDAP association by a
Start TLS operation is made a matter of local policy. This is based
on editor�s perception of WG consensus gaged by conversations at
IETF 58 and subsequent discussion on the WG mail list.

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

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

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

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

4.2.2.3. Error Conditions

"For either form of assertion, the server MUST verify that the
client's authentication identity as supplied in its TLS credentials
is permitted to be mapped to the asserted authorization identity."

This makes sense for the explicit assertion case, but seems to be
ambiguous for the implicit case.
IMHO, the mapping can be done as two steps:
a). deriving LDAP authentication identity from TLS credentials; If t
this steps fails, EXTERNAL mechanism returns failure.
b). verify that the authorization identity is allowed for the
derived authentication identity. This is always "noop" for the
implicit case.
I am not sure that the text is saying this.
(Source: Alexey Melnikov email 8/1/2003 5:30:43 PM)

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

H.41. Section 7.2 contains unnecessary [Roadmap] and misleading detail. [Authmeth]

F.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

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" I am not sure why this

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 required 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 document.
DIGEST-MD5 LDAP TS.

Section 3.3.5

- Removed paragraph beginning,"If the client is defined configured to
support multiple SASL mechanisms..." because the actions
specified in the paragraph do not provide the protections
indicated. Added a separate document new paragraph indicating that clients and there
server should allow specification of acceptable mechanisms and
only allow those mechanisms to be
nothing magical about its usage used.

- Clarified independent behavior when TLS and SASL security layers
are both in LDAP. If DIGEST-MD5 description
creates confusion 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.

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Section 4.2.3

- Rewrote entire section tries based on WG feedback.

Section 5.1

- Moved imperative language regarding unauthenticated access from
security considerations to redefine DIGEST-MD5 behavior,
which is explicitly prohibited by the SASL specification."
(Source: Alexey Melnikov: email 8/1/2003 5:30:43 PM)

Status: Resolved.

After reading the comments and here.

Section 6

- Added several paragraphs regarding the text risks of the draft plus the
related text transmitting
passwords in draft-ietf-sasl-rfc2831bis-02.txt plus
http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
02.txt, I am inclined to agree with Alexey. In -07 I rewrote section
3.3 (SASL mechanisms) to match the profiling requirements
rfc2831bis. I then dramatically reduced the material in section 7.2 clear and requiring server implementations to
provide a bare minimum and let the SASL profile stand on its own.

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

There is one issue with the way the authmeth draft is currently
written specific configuration that changes the SASL reduces these risks.

Section 6.2

- Added sentence describing protections provided by DIGEST-MD5 behavior on the way the
server responds with the subsequent authentication information .
This has been documented
method.
- Changed DNs in this fashion since RFC 2829 (section
6.1) was originally published and may cause an interoperability
issue at this point if it changed exmple to follow the DIGEST-MD5 spec (as
it was in -07 be dc=example,dc=com.

Section 10

- Updated consideration on use of AuthMeth). Take this issue cleartext passwords to the list.

Status: include
other unprotected authentication credentials
- Substantial rework of consideration on misuse of unauthenticated
bind.

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

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

(10/08/03) This item was discussed issue of effect of Start TLS and TLS closure on LDAP
association state.
- Made numerous minor wording changes based on the WG feedback.
- Updated list between 5/2/03 and
5/9/03. Consensus apppears to support the notion that RFC 2829 was
in error and that the semantics of RFC 2831 are correct and threats for Section 1.
- Recommendation that servers should
be reflected in authmeth. This not support weaker TLS
ciphersuites unless other protection is already the case as of the -07
draft.

H.43. DIGEST-MD5 Realms recommendations for LDAP

From http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
02.txt: A protocol profile SHOULD provide a guidance how realms are
to be constructed and used in the protocol and MAY further restrict
its syntax place.
- Moved authentication state table to appendix and protocol-specific semantics."

I don't believe that any such guidance exists within the LDAP TS.
The most likely place relettered
appendices.

F.10. Changes for this draft-ldapbis-authmeth-11

General

- Many editorial changes throughout to reside is in the authmeth draft.

Related email clarify wording and better
express intent, primarily based on suggestions from Alexey Melnikov (8/4/2003 1:08:40 PM):

"The problem I have with the document is that it references realm
without explaining what it is (or at least some examples WG mail
list.
- More standard naming of valid
values). For LDAP, some recommendations should be given. For example:
1). Use a hardcoded string as the realm (one authentication mechanisms throughout
document, e.g. "Anonymous Authentication Mechanism of the implementations
I worked on was doing that) Simple
Bind Choice".

Section 1

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2). Use hostname (realm==host) or domain/cluster name (realm
includes multiple hosts).
3). Use a node in DIT above user entry, for example for "cn=Barbara
Jensen, ou=Accounting, o=Ace Industry, c=US"
and "cn=John Doe, ou=Accounting, o=Ace Industry, c=US" realm can be
"ou=Accounting, o=Ace Industry, c=US"
(or "o=Ace Industry, c=US"); for "cn=Gern Jensen, ou=Product
Testing,o=Ace Industry, c=US" realm can be "ou=Product Testing,
o=Ace Industry, c=US".

Of course other choices are possible.

Alexey

To summarize: I'd like authmeth

- Editorial changes to define a realm name 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
Digest-MD5 that corresponds
StartTLS. Incorporates material moved from other sections of
authmeth -09.

Section 4
- New section added to discuss LDAP DNs known to this server.
Authzid is okay, but perhaps could be better put Associations. Related material
was moved from various other sections of authmeth -09 and
incorporated into context.

John McMeeking (5/12/2003)

Status: Resolved.

draft-ietf-sasl-rfc2222bis-03.txt no longer requires this
information in a SASL protocol. In addition, the ldapbis WG chairs
have ruled this work out of scope. Individuals are welcome to make
submissions to provide guidance on the use of realm new section.

Section 5

- Added several paragraphs regarding transmission and realm values
in LDAP.

H.44. Use derivation
of DNs in usernames authentication and realms in DIGEST-MD5

In reading authorization identities using the discussion 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 mailing list, I reach the following
conclusions:

DIGEST-MD5 username actions table, and realm are simple strings. The syntax removing the current state column of
these strings allows strings that look like DNs in form, however,
DIGEST-MD5 treats them a simple strings for comparision purposes.
For example, the DNs cn=roger, o=US and cn=roger,o=us are equivalent
when being compared semantically as DNs, however, these would be
considered two different username values in DIGEST-MD5 because
simple octet-wise semantics (rather than DN semantics) are used to
compare username values in DIGEST-MD5. Ditto for realm values.

Status: Resolved.

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

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

Going forward, it would be much better to clarify that simple
+TLS is
state transition table. Updated references to be used for DN/password credentials authmeth and DIGEST-MD5
(or PLAIN+TLS) be used
[Protocol].

F.11. Changes for username/password credentials. (Kurt
Zeilenga, 5/12/2003) 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.

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I don't believe you can mandate simple/TLS! At the time RFC 2829 was
debated, a large number on the WG wanted this. They did not get
their way because of the complexity of

Section 2

- Added implementation requirement that server implementations
that SUPPORT StartTLS MUST support the solution. It was argued
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite.

Section 3.1.2

- Added wording clarifying that a password-based method would be better. I think they believed
it would still be DN/password, though. (Ron Ramsay, 5/12/2003)

This was officially opened as an issue by WG co-chair Kurt Zeilenga
on 5/12/03. Little direct discussion has occurred since, however
there has been significant discussion on client's association is
unaffected if a non-success resultCode is returned in the use
StartTLS response.

Section 9.2

- Final paragraph of DN values as the
username this section details requirements for DIGEST-MD5.

Status: Resolved.

Based
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 list discussion, Kurt Zeilenga has gaged a lack of WG
consensus that Simple+TLS should be mandatory feedback.

Section 13

- Moved section to implement. No
further discussion is necessary. become section 3.3.

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this standard. Please address the information to the IETF at ietf-
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Full Copyright Statement

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Copyright (C) The Internet Society (2004). This document is subject
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This document and the information contained herein are provided on
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