draft-ietf-ldapbis-authmeth-19.txt   rfc4513.txt 
INTERNET-DRAFT Editor: R. Harrison Network Working Group R. Harrison, Ed.
draft-ietf-ldapbis-authmeth-19.txt Novell, Inc. Request for Comments: 4513 Novell, Inc.
Obsoletes: 2251, 2829, 2830 February 2006 Obsoletes: 2251, 2829, 2830 June 2006
Intended Category: Standards Track Category: Standards Track
LDAP: Authentication Methods
and
Security Mechanisms
Status of this Memo
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This document is intended to be, after appropriate review and Lightweight Directory Access Protocol (LDAP):
revision, submitted to the RFC Editor as a Standard Track document. Authentication Methods and Security Mechanisms
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Abstract Abstract
This document describes authentication methods and security This document describes authentication methods and security
mechanisms of the Lightweight Directory Access Protocol (LDAP). mechanisms of the Lightweight Directory Access Protocol (LDAP). This
document details establishment of Transport Layer Security (TLS)
This document details establishment of Transport Layer Security using the StartTLS operation.
(TLS) using the StartTLS operation.
This document details the simple Bind authentication method This document details the simple Bind authentication method including
including anonymous, unauthenticated, and name/password mechanisms anonymous, unauthenticated, and name/password mechanisms and the
and the Simple Authentication and Security Layer (SASL) Bind Simple Authentication and Security Layer (SASL) Bind authentication
authentication method including the EXTERNAL mechanism. method including the EXTERNAL mechanism.
This document discusses various authentication and authorization This document discusses various authentication and authorization
states through which a session to an LDAP server may pass and the states through which a session to an LDAP server may pass and the
actions that trigger these state changes. actions that trigger these state changes.
This document, together with other documents in the LDAP Technical This document, together with other documents in the LDAP Technical
Specification (see section 1 of [Roadmap]), obsoletes RFC 2251, RFC Specification (see Section 1 of the specification's road map),
2829 and RFC 2830. obsoletes RFC 2251, RFC 2829, and RFC 2830.
Table of Contents Table of Contents
1. Introduction.....................................................3 1. Introduction ....................................................4
1.1. Relationship to Other Documents................................5 1.1. Relationship to Other Documents ............................6
1.2. Conventions....................................................6 1.2. Conventions ................................................6
2. Implementation Requirements......................................7 2. Implementation Requirements .....................................7
3. StartTLS Operation...............................................7 3. StartTLS Operation ..............................................8
3.1. TLS Establishment Procedures...................................7 3.1. TLS Establishment Procedures ..............................8
3.1.1. StartTLS Request Sequencing..................................8 3.1.1. StartTLS Request Sequencing .........................8
3.1.2. Client Certificate...........................................8 3.1.2. Client Certificate ..................................9
3.1.3. Server Identity Check........................................8 3.1.3. Server Identity Check ...............................9
3.1.3.1. Comparison of DNS Names...................................10 3.1.3.1. Comparison of DNS Names ...................10
3.1.3.2. Comparison of IP Addresses................................10 3.1.3.2. Comparison of IP Addresses ................11
3.1.3.3. Comparison of other subjectName types.....................10 3.1.3.3. Comparison of Other subjectName Types .....11
3.1.4. Discovery of Resultant Security Level.......................10 3.1.4. Discovery of Resultant Security Level ..............11
3.1.5. Refresh of Server Capabilities Information..................11 3.1.5. Refresh of Server Capabilities Information .........11
3.2. Effect of TLS on Authorization State..........................11 3.2. Effect of TLS on Authorization State .....................12
3.3. TLS Ciphersuites..............................................11 3.3. TLS Ciphersuites ..........................................12
4. Authorization State.............................................12 4. Authorization State ............................................13
5. Bind Operation..................................................13 5. Bind Operation .................................................14
5.1. Simple Authentication Method..................................13 5.1. Simple Authentication Method ..............................14
5.1.1. Anonymous Authentication Mechanism of Simple Bind...........13 5.1.1. Anonymous Authentication Mechanism of Simple Bind ..14
5.1.2. Unauthenticated Authentication Mechanism of Simple Bind.....13 5.1.2. Unauthenticated Authentication Mechanism of
5.1.3. Name/Password Authentication Mechanism of Simple Bind.......14 Simple Bind ........................................14
5.2. SASL Authentication Method....................................15 5.1.3. Name/Password Authentication Mechanism of
5.2.1. SASL Protocol Profile.......................................15 Simple Bind ........................................15
5.2.1.1. SASL Service Name for LDAP................................15 5.2. SASL Authentication Method ................................16
5.2.1.2. SASL Authentication Initiation and Protocol Exchange......15 5.2.1. SASL Protocol Profile ..............................16
5.2.1.3. Optional Fields...........................................16 5.2.1.1. SASL Service Name for LDAP ................16
5.2.1.4. Octet Where Negotiated Security Layers Take Effect........17 5.2.1.2. SASL Authentication Initiation and
5.2.1.5. Determination of Supported SASL Mechanisms................17 Protocol Exchange .........................16
5.2.1.6. Rules for Using SASL Layers...............................17 5.2.1.3. Optional Fields ...........................17
5.2.1.7. Support for Multiple Authentications......................18 5.2.1.4. Octet Where Negotiated Security
5.2.1.8. SASL Authorization Identities.............................18 Layers Take Effect ........................18
5.2.2. SASL Semantics Within LDAP..................................19 5.2.1.5. Determination of Supported SASL
5.2.3. SASL EXTERNAL Authentication Mechanism......................19 Mechanisms ................................18
5.2.3.1. Implicit Assertion........................................19 5.2.1.6. Rules for Using SASL Layers ...............19
5.2.3.2. Explicit Assertion........................................20 5.2.1.7. Support for Multiple Authentications ......19
6. Security Considerations.........................................20 5.2.1.8. SASL Authorization Identities .............19
6.1. General LDAP Security Considerations..........................20 5.2.2. SASL Semantics within LDAP .........................20
6.2. StartTLS Security Considerations..............................21 5.2.3. SASL EXTERNAL Authentication Mechanism .............20
6.3. Bind Operation Security Considerations........................21 5.2.3.1. Implicit Assertion ........................21
6.3.1. Unauthenticated Mechanism Security Considerations...........21 5.2.3.2. Explicit Assertion ........................21
6.3.2. Name/Password Mechanism Security Considerations.............22 6. Security Considerations ........................................21
6.3.3. Password-related Security Considerations....................22 6.1. General LDAP Security Considerations ......................21
6.3.4. Hashed Password Security Considerations.....................23 6.2. StartTLS Security Considerations ..........................22
6.4.SASL Security Considerations...................................23 6.3. Bind Operation Security Considerations ....................23
6.5. Related Security Considerations...............................23 6.3.1. Unauthenticated Mechanism Security Considerations ..23
7. IANA Considerations.............................................24 6.3.2. Name/Password Mechanism Security Considerations ....23
8. Acknowledgments.................................................24 6.3.3. Password-Related Security Considerations ...........23
9. Normative References............................................24 6.3.4. Hashed Password Security Considerations ............24
10. Informative References.........................................25 6.4. SASL Security Considerations ..............................24
Author's Address...................................................26 6.5. Related Security Considerations ...........................25
Appendix A. Authentication and Authorization Concepts..............26 7. IANA Considerations ............................................25
A.1. Access Control Policy.........................................26 8. Acknowledgements ...............................................25
A.2. Access Control Factors........................................26 9. Normative References ...........................................26
A.3. Authentication, Credentials, Identity.........................27 10. Informative References ........................................27
A.4. Authorization Identity........................................27 Appendix A. Authentication and Authorization Concepts .............28
Appendix B. Summary of Changes.....................................27 A.1. Access Control Policy .....................................28
B.1. Changes Made to RFC 2251......................................28 A.2. Access Control Factors ....................................28
B.1.1. Section 4.2.1 (Sequencing of the Bind Request)..............28 A.3. Authentication, Credentials, Identity .....................28
B.1.2. Section 4.2.2 (Authentication and Other Security Services)..28 A.4. Authorization Identity ....................................29
B.2. Changes Made to RFC 2829......................................28 Appendix B. Summary of Changes ....................................29
B.2.1. Section 4 (Required security mechanisms)....................29 B.1. Changes Made to RFC 2251 ..................................30
B.2.2. Section 5.1 (Anonymous authentication procedure)............29 B.1.1. Section 4.2.1 ("Sequencing of the Bind Request") ...30
B.2.3. Section 6 (Password-based authentication)...................29 B.1.2. Section 4.2.2 ("Authentication and Other Security
B.2.4. Section 6.1 (Digest authentication).........................29 Services") .........................................30
B.2.5. Section 6.2 ("simple" authentication choice with TLS).......29 B.2. Changes Made to RFC 2829 ..................................30
B.2.6. Section 6.3 (Other authentication choices with TLS).........29 B.2.1. Section 4 ("Required security mechanisms") .........30
B.2.7. Section 7.1 (Certificate-based authentication with TLS).....30 B.2.2. Section 5.1 ("Anonymous authentication
B.2.8. Section 8 (Other mechanisms)................................30 procedure") ........................................31
B.2.9. Section 9 (Authorization identity)..........................30 B.2.3. Section 6 ("Password-based authentication") ........31
B.2.10. Section 10 (TLS Ciphersuites)..............................30 B.2.4. Section 6.1 ("Digest authentication") ..............31
B.3. Changes Made to RFC 2830: ....................................30 B.2.5. Section 6.2 ("'simple' authentication choice under
B.3.1. Section 3.6 (Server Identity Check).........................30 TLS encryption") ...................................31
B.3.2. Section 3.7 (Refresh of Server Capabilities Information)....31 B.2.6. Section 6.3 ("Other authentication choices with
B.3.3. Section 5.2 (Effects of TLS on Authorization Identity)......31 TLS") ..............................................31
B.3.4. Section 5.1.1 (TLS Closure Effects).........................31 B.2.7. Section 7.1 ("Certificate-based authentication
Appendix C. Changes for draft-ldapbis-authmeth-19..................31 with TLS") .........................................31
Intellectual Property Rights.......................................32 B.2.8. Section 8 ("Other mechanisms") .....................32
Full Copyright Statement...........................................33 B.2.9. Section 9 ("Authorization Identity") ...............32
B.2.10. Section 10 ("TLS Ciphersuites") ...................32
B.3. Changes Made to RFC 2830 ..................................32
B.3.1. Section 3.6 ("Server Identity Check") ..............32
B.3.2. Section 3.7 ("Refresh of Server Capabilities
Information") ......................................33
B.3.3. Section 5 ("Effects of TLS on a Client's
Authorization Identity") ...........................33
B.3.4. Section 5.2 ("TLS Connection Closure Effects") .....33
1. Introduction 1. Introduction
The Lightweight Directory Access Protocol (LDAP) [Roadmap] is a
The Lightweight Directory Access Protocol (LDAP) [RFC4510] is a
powerful protocol for accessing directories. It offers means of powerful protocol for accessing directories. It offers means of
searching, retrieving and manipulating directory content and ways to searching, retrieving, and manipulating directory content and ways to
access a rich set of security functions. access a rich set of security functions.
It is vital that these security functions be interoperable among all It is vital that these security functions be interoperable among all
LDAP clients and servers on the Internet; therefore there has to be LDAP clients and servers on the Internet; therefore there has to be a
a minimum subset of security functions that is common to all minimum subset of security functions that is common to all
implementations that claim LDAP conformance. implementations that claim LDAP conformance.
Basic threats to an LDAP directory service include (but are not Basic threats to an LDAP directory service include (but are not
limited to): limited to):
(1) Unauthorized access to directory data via data-retrieval (1) Unauthorized access to directory data via data-retrieval
operations. operations.
(2) Unauthorized access to directory data by monitoring access of (2) Unauthorized access to directory data by monitoring access of
others. others.
(3) Unauthorized access to reusable client authentication (3) Unauthorized access to reusable client authentication information
information by monitoring access of others. by monitoring access of others.
(4) Unauthorized modification of directory data. (4) Unauthorized modification of directory data.
(5) Unauthorized modification of configuration information. (5) Unauthorized modification of configuration information.
(6) Denial of Service: Use of resources (commonly in excess) in a (6) Denial of Service: Use of resources (commonly in excess) in a
manner intended to deny service to others. manner intended to deny service to others.
(7) Spoofing: Tricking a user or client into believing that (7) Spoofing: Tricking a user or client into believing that
information came from the directory when in fact it did not, information came from the directory when in fact it did not,
either by modifying data in transit or misdirecting the client's either by modifying data in transit or misdirecting the client's
transport connection. Tricking a user or client into sending transport connection. Tricking a user or client into sending
privileged information to a hostile entity that appears to be privileged information to a hostile entity that appears to be the
the directory server but is not. Tricking a directory server directory server but is not. Tricking a directory server into
into believing that information came from a particular client believing that information came from a particular client when in
when in fact it came from a hostile entity. fact it came from a hostile entity.
(8) Hijacking: An attacker seizes control of an established protocol (8) Hijacking: An attacker seizes control of an established protocol
session. session.
Threats (1), (4), (5), (6), (7) are (8) are active attacks. Threats Threats (1), (4), (5), (6), (7), and (8) are active attacks. Threats
(2) and (3) are passive attacks. (2) and (3) are passive attacks.
Threats (1), (4), (5) and (6) are due to hostile clients. Threats 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 (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 client and server or hostile agents posing as a server, e.g., IP
spoofing. spoofing.
LDAP offers the following security mechanisms: LDAP offers the following security mechanisms:
(1) Authentication by means of the Bind operation. The Bind (1) Authentication by means of the Bind operation. The Bind
operation provides a simple method which supports anonymous, operation provides a simple method that supports anonymous,
unauthenticated, and name/password mechanisms, and the Simple unauthenticated, and name/password mechanisms, and the Simple
Authentication and Security Layer (SASL) method which supports a Authentication and Security Layer (SASL) method, which supports a
wide variety of authentication mechanisms. wide variety of authentication mechanisms.
(2) Mechanisms to support vendor-specific access control facilities (2) Mechanisms to support vendor-specific access control facilities
(LDAP does not offer a standard access control facility). (LDAP does not offer a standard access control facility).
(3) Data integrity service by means of security layers in Transport (3) Data integrity service by means of security layers in Transport
Layer Security (TLS) or SASL mechanisms. Layer Security (TLS) or SASL mechanisms.
(4) Data confidentiality service by means of security layers in TLS (4) Data confidentiality service by means of security layers in TLS
or SASL mechanisms. or SASL mechanisms.
(5) Server resource usage limitation by means of administrative (5) Server resource usage limitation by means of administrative
limits configured on the server. limits configured on the server.
(6) Server authentication by means of the TLS protocol or SASL (6) Server authentication by means of the TLS protocol or SASL
mechanisms. mechanisms.
LDAP may also be protected by means outside the LDAP protocol, e.g., LDAP may also be protected by means outside the LDAP protocol, e.g.,
with IP-level security [RFC4301]. with IP layer security [RFC4301].
Experience has shown that simply allowing implementations to pick Experience has shown that simply allowing implementations to pick and
and choose the security mechanisms that will be implemented is not a choose the security mechanisms that will be implemented is not a
strategy that leads to interoperability. In the absence of strategy that leads to interoperability. In the absence of mandates,
mandates, clients will continue to be written that do not support clients will continue to be written that do not support any security
any security function supported by the server, or worse, they will function supported by the server, or worse, they will only support
only support mechanisms that provide inadequate security for most mechanisms that provide inadequate security for most circumstances.
circumstances.
It is desirable to allow clients to authenticate using a variety of It is desirable to allow clients to authenticate using a variety of
mechanisms including mechanisms where identities are represented as mechanisms including mechanisms where identities are represented as
distinguished names [X.501][Models] in string form [LDAPDN] or as distinguished names [X.501][RFC4512], in string form [RFC4514], or as
used in different systems (e.g., simple user names [RFC4013]). used in different systems (e.g., simple user names [RFC4013]).
Because some authentication mechanisms transmit credentials in plain Because some authentication mechanisms transmit credentials in plain
text form, and/or do not provide data security services and/or are text form, and/or do not provide data security services and/or are
subject to passive attacks, it is necessary to ensure secure subject to passive attacks, it is necessary to ensure secure
interoperability by identifying a mandatory-to-implement mechanism interoperability by identifying a mandatory-to-implement mechanism
for establishing transport-layer security services. for establishing transport-layer security services.
The set of security mechanisms provided in LDAP and described in The set of security mechanisms provided in LDAP and described in this
this document is intended to meet the security needs for a wide document is intended to meet the security needs for a wide range of
range of deployment scenarios and still provide a high degree of deployment scenarios and still provide a high degree of
interoperability among various LDAP implementations and deployments. interoperability among various LDAP implementations and deployments.
1.1. Relationship to Other Documents 1.1. Relationship to Other Documents
This document is an integral part of the LDAP Technical This document is an integral part of the LDAP Technical Specification
Specification [Roadmap]. [RFC4510].
This document, together with [Roadmap], [Protocol], and [Models], This document, together with [RFC4510], [RFC4511], and [RFC4512],
obsoletes RFC 2251 in its entirety. Sections 4.2.1 (portions), and obsoletes RFC 2251 in its entirety. Sections 4.2.1 (portions) and
4.2.2 of RFC 2251 are obsoleted by this document. Appendix B.1 4.2.2 of RFC 2251 are obsoleted by this document. Appendix B.1
summarizes the substantive changes made to RFC 2251 by this document. summarizes the substantive changes made to RFC 2251 by this document.
This document obsoletes RFC 2829 in its entirety. Appendix B.2 This document obsoletes RFC 2829 in its entirety. Appendix B.2
summarizes the substantive changes made to RFC 2829 by this document. summarizes the substantive changes made to RFC 2829 by this document.
Sections 2 and 4 of RFC 2830 are obsoleted by [Protocol]. The Sections 2 and 4 of RFC 2830 are obsoleted by [RFC4511]. The
remainder of RFC 2830 is obsoleted by this document. Appendix B.3 remainder of RFC 2830 is obsoleted by this document. Appendix B.3
summarizes the substantive changes made to RFC 2830 by this document. summarizes the substantive changes made to RFC 2830 by this document.
1.2. Conventions 1.2. Conventions
The key words "MUST", "MUST NOT", "SHALL", "SHOULD", "SHOULD NOT", The key words "MUST", "MUST NOT", "SHALL", "SHOULD", "SHOULD NOT",
"MAY", and "OPTIONAL" in this document are to be interpreted as "MAY", and "OPTIONAL" in this document are to be interpreted as
described in RFC 2119 [RFC2119]. described in RFC 2119 [RFC2119].
The term "user" represents any human or application entity which is The term "user" represents any human or application entity that is
accessing the directory using a directory client. A directory accessing the directory using a directory client. A directory client
client (or client) is also known as a directory user agent (DUA). (or client) is also known as a directory user agent (DUA).
The term "transport connection" refers to the underlying transport The term "transport connection" refers to the underlying transport
services used to carry the protocol exchange, as well as services used to carry the protocol exchange, as well as associations
associations established by these services. established by these services.
The term "TLS layer" refers to TLS services used in providing The term "TLS layer" refers to TLS services used in providing
security services, as well as associations established by these security services, as well as associations established by these
services. services.
The term "SASL layer" refers to SASL services used in providing The term "SASL layer" refers to SASL services used in providing
security services, as well as associations established by these security services, as well as associations established by these
services. services.
The term "LDAP message layer" refers to the LDAP Message (PDU) The term "LDAP message layer" refers to the LDAP Message (PDU)
skipping to change at page 6, line 53 skipping to change at page 7, line 15
The term "LDAP session" refers to combined services (transport The term "LDAP session" refers to combined services (transport
connection, TLS layer, SASL layer, LDAP message layer) and their connection, TLS layer, SASL layer, LDAP message layer) and their
associations. associations.
In general, security terms in this document are used consistently In general, security terms in this document are used consistently
with the definitions provided in [RFC2828]. In addition, several with the definitions provided in [RFC2828]. In addition, several
terms and concepts relating to security, authentication, and terms and concepts relating to security, authentication, and
authorization are presented in Appendix A of this document. While authorization are presented in Appendix A of this document. While
the formal definition of these terms and concepts is outside the the formal definition of these terms and concepts is outside the
scope of this document, an understanding of them is prerequisite to scope of this document, an understanding of them is prerequisite to
understanding much of the material in this document. Readers who understanding much of the material in this document. Readers who are
are unfamiliar with security-related concepts are encouraged to unfamiliar with security-related concepts are encouraged to review
review Appendix A before reading the remainder of this document. Appendix A before reading the remainder of this document.
2. Implementation Requirements 2. Implementation Requirements
LDAP server implementations MUST support the anonymous LDAP server implementations MUST support the anonymous authentication
authentication mechanism of the simple Bind method (section 5.1.1). mechanism of the simple Bind method (Section 5.1.1).
LDAP implementations that support any authentication mechanism other LDAP implementations that support any authentication mechanism other
than the anonymous authentication mechanism of the simple Bind than the anonymous authentication mechanism of the simple Bind method
method MUST support the name/password authentication mechanism of MUST support the name/password authentication mechanism of the simple
the simple Bind method (section 5.1.3) and MUST be capable of Bind method (Section 5.1.3) and MUST be capable of protecting this
protecting this name/password authentication using TLS as name/password authentication using TLS as established by the StartTLS
established by the StartTLS operation (section 3). operation (Section 3).
Implementations SHOULD disallow the use of the name/password Implementations SHOULD disallow the use of the name/password
authentication mechanism by default when suitable data security authentication mechanism by default when suitable data security
services are not in place, and MAY provide other suitable data services are not in place, and they MAY provide other suitable data
security services for use with this authentication mechanism. security services for use with this authentication mechanism.
Implementations MAY support additional authentication mechanisms. Implementations MAY support additional authentication mechanisms.
Some of these mechanisms are discussed below. Some of these mechanisms are discussed below.
LDAP server implementations SHOULD support client assertion of LDAP server implementations SHOULD support client assertion of
authorization identity via the SASL EXTERNAL mechanism (section authorization identity via the SASL EXTERNAL mechanism (Section
5.2.3). 5.2.3).
LDAP server implementations that support no authentication mechanism LDAP server implementations that support no authentication mechanism
other than the anonymous mechanism of the simple bind method SHOULD other than the anonymous mechanism of the simple bind method SHOULD
support use of TLS as established by the the StartTLS operation support use of TLS as established by the StartTLS operation (Section
(section 3). (Other servers MUST support TLS per the second 3). (Other servers MUST support TLS per the second paragraph of this
paragraph of this section.) section.)
Implementations supporting TLS MUST support the Implementations supporting TLS MUST support the
TLS_RSA_WITH_3DES_EDE_CBC_SHA ciphersuite and SHOULD support the TLS_RSA_WITH_3DES_EDE_CBC_SHA ciphersuite and SHOULD support the
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite. Support for the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite. Support for the
latter ciphersuite is recommended to encourage interoperability with latter ciphersuite is recommended to encourage interoperability with
implementations conforming to earlier LDAP StartTLS specifications. implementations conforming to earlier LDAP StartTLS specifications.
3. StartTLS Operation 3. StartTLS Operation
The Start Transport Layer Security (StartTLS) operation defined in The Start Transport Layer Security (StartTLS) operation defined in
section 4.14 of [Protocol] provides the ability to establish TLS Section 4.14 of [RFC4511] provides the ability to establish TLS
[TLS] in an LDAP session. [RFC4346] in an LDAP session.
The goals of using the TLS [TLS] protocol with LDAP are to ensure The goals of using the TLS protocol with LDAP are to ensure data
data confidentiality and integrity, and to optionally provide for confidentiality and integrity, and to optionally provide for
authentication. TLS expressly provides these capabilities, although authentication. TLS expressly provides these capabilities, although
the authentication services of TLS are available to LDAP only in the authentication services of TLS are available to LDAP only in
combination with the SASL EXTERNAL authentication method (see combination with the SASL EXTERNAL authentication method (see Section
section 5.2.3), and then only if the SASL EXTERNAL implementation 5.2.3), and then only if the SASL EXTERNAL implementation chooses to
chooses to make use of the TLS credentials. make use of the TLS credentials.
3.1. TLS Establishment Procedures
3.1. TLS Establishment Procedures
This section describes the overall procedures clients and servers This section describes the overall procedures clients and servers
must follow for TLS establishment. These procedures take into must follow for TLS establishment. These procedures take into
consideration various aspects of the TLS layer including discovery consideration various aspects of the TLS layer including discovery of
of resultant security level and assertion of the client's resultant security level and assertion of the client's authorization
authorization identity. identity.
3.1.1. StartTLS Request Sequencing 3.1.1. StartTLS Request Sequencing
A client may send the StartTLS extended request at any time after A client may send the StartTLS extended request at any time after
establishing an LDAP session, except: establishing an LDAP session, except:
- when TLS is currently established on the session, - when TLS is currently established on the session,
- when a multi-stage SASL negotiation is in progress on the - when a multi-stage SASL negotiation is in progress on the
session, or session, or
- when there are outstanding responses for operation requests - when there are outstanding responses for operation requests
previously issued on the session. previously issued on the session.
As described in [Protocol] Section 4.14.1, a (detected) violation of As described in [RFC4511], Section 4.14.1, a (detected) violation of
any of these requirements results in a return of the operationsError any of these requirements results in a return of the operationsError
resultCode. resultCode.
Client implementers should ensure that they strictly follow these Client implementers should ensure that they strictly follow these
operation sequencing requirements to prevent interoperability operation sequencing requirements to prevent interoperability issues.
issues. Operational experience has shown that violating these Operational experience has shown that violating these requirements
requirements causes interoperability issues because there are race causes interoperability issues because there are race conditions that
conditions that prevent servers from detecting some violations of prevent servers from detecting some violations of these requirements
these requirements due to factors such as server hardware speed and due to factors such as server hardware speed and network latencies.
network latencies.
There is no general requirement that the client have or have not There is no general requirement that the client have or have not
already performed a Bind operation (section 5) before sending a already performed a Bind operation (Section 5) before sending a
StartTLS operation request, however where a client intends to StartTLS operation request; however, where a client intends to
perform both a Bind operation and a StartTLS operation, it SHOULD perform both a Bind operation and a StartTLS operation, it SHOULD
first perform the StartTLS operation so that the Bind request and first perform the StartTLS operation so that the Bind request and
response messages are protected by the data security services response messages are protected by the data security services
established by the StartTLS operation. established by the StartTLS operation.
3.1.2. Client Certificate 3.1.2. Client Certificate
If an LDAP server requests or demands that a client provide a user If an LDAP server requests or demands that a client provide a user
certificate during TLS negotiation and the client does not present a certificate during TLS negotiation and the client does not present a
suitable user certificate (e.g., one that can be validated), the suitable user certificate (e.g., one that can be validated), the
server may use a local security policy to determine whether to server may use a local security policy to determine whether to
successfully complete TLS negotiation. successfully complete TLS negotiation.
If a client that has provided a suitable certificate subsequently If a client that has provided a suitable certificate subsequently
performs a Bind operation using the SASL EXTERNAL authentication performs a Bind operation using the SASL EXTERNAL authentication
mechanism (section 5.2.3), information in the certificate may be mechanism (Section 5.2.3), information in the certificate may be used
used by the server to identify and authenticate the client. by the server to identify and authenticate the client.
3.1.3. Server Identity Check 3.1.3. Server Identity Check
In order to prevent man-in-the-middle attacks the client MUST verify
In order to prevent man-in-the-middle attacks, the client MUST verify
the server's identity (as presented in the server's Certificate the server's identity (as presented in the server's Certificate
message). In this section, the client's understanding of the message). In this section, the client's understanding of the
server's identity (typically the identity used to establish the server's identity (typically the identity used to establish the
transport connection) is called the "reference identity". transport connection) is called the "reference identity".
The client determines the type (e.g., DNS name or IP address) of the The client determines the type (e.g., DNS name or IP address) of the
reference identity and performs a comparison between the reference reference identity and performs a comparison between the reference
identity and each subjectAltName value of the corresponding type identity and each subjectAltName value of the corresponding type
until a match is produced. Once a match is produced, the server's until a match is produced. Once a match is produced, the server's
identity has been verified and the server identity check is identity has been verified, and the server identity check is
complete. Different subjectAltName types are matched in different complete. Different subjectAltName types are matched in different
ways. Sections 3.1.3.1 - 3.1.3.3 explain how to compare values of ways. Sections 3.1.3.1 - 3.1.3.3 explain how to compare values of
various subjectAltName types. various subjectAltName types.
The client may map the reference identity to a different type prior The client may map the reference identity to a different type prior
to performing a comparison. Mappings may be performed for all to performing a comparison. Mappings may be performed for all
available subjectAltName types to which the reference identity can available subjectAltName types to which the reference identity can be
be mapped, however the reference identity should only be mapped to mapped; however, the reference identity should only be mapped to
types for which the mapping is either inherently secure (e.g., types for which the mapping is either inherently secure (e.g.,
extracting the DNS name from a URI to compare with a subjectAltName extracting the DNS name from a URI to compare with a subjectAltName
of type dNSName) or for which the mapping is performed in a secure of type dNSName) or for which the mapping is performed in a secure
manner (e.g., using DNSSec, or using user- (or admin-) configured manner (e.g., using DNSSEC, or using user- or admin-configured host-
host-to-address/address-to-host lookup tables). to-address/address-to-host lookup tables).
The server's identity may also be verified by comparing the The server's identity may also be verified by comparing the reference
reference identity to the Common Name (CN) [Schema] value in the identity to the Common Name (CN) [RFC4519] value in the leaf Relative
leaf RDN of the subjectName field of the server's certificate. This Distinguished Name (RDN) of the subjectName field of the server's
comparison is performed using the rules for comparison of DNS names certificate. This comparison is performed using the rules for
in section 3.1.3.1 below, with the exception that no wildcard comparison of DNS names in Section 3.1.3.1, below, with the exception
matching is allowed. Although the use of the Common Name value is that no wildcard matching is allowed. Although the use of the Common
existing practice, it is deprecated and Certification Authorities Name value is existing practice, it is deprecated, and Certification
are encouraged to provide subjectAltName values instead. Note that Authorities are encouraged to provide subjectAltName values instead.
the TLS implementation may represent DNs in certificates according Note that the TLS implementation may represent DNs in certificates
to X.500 or other conventions. For example, some X.500 according to X.500 or other conventions. For example, some X.500
implementations order the RDNs in a DN using a left-to-right (most implementations order the RDNs in a DN using a left-to-right (most
significant to least significant) convention instead of LDAP's significant to least significant) convention instead of LDAP's
right-to-left convention. right-to-left convention.
If the server identity check fails, user-oriented clients SHOULD If the server identity check fails, user-oriented clients SHOULD
either notify the user (clients may give the user the opportunity to either notify the user (clients may give the user the opportunity to
continue with the LDAP session in this case) or close the transport continue with the LDAP session in this case) or close the transport
connection and indicate that the server's identity is suspect. connection and indicate that the server's identity is suspect.
Automated clients SHOULD close the transport connection and then Automated clients SHOULD close the transport connection and then
return or log an error indicating that the server's identity is return or log an error indicating that the server's identity is
suspect or both. suspect or both.
Beyond the server identity check described in this section, clients Beyond the server identity check described in this section, clients
should be prepared to do further checking to ensure that the server should be prepared to do further checking to ensure that the server
is authorized to provide the service it is requested to provide. is authorized to provide the service it is requested to provide. The
The client may need to make use of local policy information in client may need to make use of local policy information in making
making this determination. this determination.
3.1.3.1. Comparison of DNS Names 3.1.3.1. Comparison of DNS Names
If the reference identity is an internationalized domain name, If the reference identity is an internationalized domain name,
conforming implementations MUST convert it to the ASCII Compatible conforming implementations MUST convert it to the ASCII Compatible
Encoding (ACE) format as specified in section 4 of RFC 3490 Encoding (ACE) format as specified in Section 4 of RFC 3490 [RFC3490]
[RFC3490] before comparison with subjectAltName values of type before comparison with subjectAltName values of type dNSName.
dNSName. Specifically, conforming implementations MUST perform the Specifically, conforming implementations MUST perform the conversion
conversion operation specified in section 4 of RFC 3490 as follows: operation specified in Section 4 of RFC 3490 as follows:
* in step 1, the domain name SHALL be considered a "stored * in step 1, the domain name SHALL be considered a "stored
string"; string";
* in step 3, set the flag called "UseSTD3ASCIIRules"; * in step 3, set the flag called "UseSTD3ASCIIRules";
* in step 4, process each label with the "ToASCII" * in step 4, process each label with the "ToASCII" operation; and
operation; and * in step 5, change all label separators to U+002E (full stop).
* in step 5, change all label separators to U+002E (full
stop).
After performing the "to-ASCII" conversion, the DNS labels and names After performing the "to-ASCII" conversion, the DNS labels and names
MUST be compared for equality according to the rules specified in MUST be compared for equality according to the rules specified in
section 3 of RFC3490. Section 3 of RFC3490.
The '*' (ASCII 42) wildcard character is allowed in subjectAltName The '*' (ASCII 42) wildcard character is allowed in subjectAltName
values of type dNSName and then only as the left-most (least values of type dNSName, and then only as the left-most (least
significant) DNS label in that value. This wildcard matches any significant) DNS label in that value. This wildcard matches any
left-most DNS label in the server name. That is, the subject left-most DNS label in the server name. That is, the subject
*.example.com matches the server names a.example.com and *.example.com matches the server names a.example.com and
b.example.com but does not match example.com or a.b.example.com. b.example.com, but does not match example.com or a.b.example.com.
3.1.3.2. Comparison of IP Addresses 3.1.3.2. Comparison of IP Addresses
When the reference identity is an IP address, the identity MUST be When the reference identity is an IP address, the identity MUST be
converted to the "network byte order" octet string representation converted to the "network byte order" octet string representation
[RFC791][RFC2460]. For IP Version 4, as specified in RFC 791, the [RFC791][RFC2460]. For IP Version 4, as specified in RFC 791, the
octet string will contain exactly four octets. For IP Version 6, as octet string will contain exactly four octets. For IP Version 6, as
specified in RFC 2460, the octet string will contain exactly sixteen specified in RFC 2460, the octet string will contain exactly sixteen
octets. This octet string is then compared against subjectAltName octets. This octet string is then compared against subjectAltName
values of type iPAddress. A match occurs if the reference identity values of type iPAddress. A match occurs if the reference identity
octet string and value octet strings are identical. octet string and value octet strings are identical.
3.1.3.3. Comparison of other subjectName types 3.1.3.3. Comparison of Other subjectName Types
Client implementations MAY support matching against subjectAltName Client implementations MAY support matching against subjectAltName
values of other types as described in other documents. values of other types as described in other documents.
3.1.4. Discovery of Resultant Security Level 3.1.4. Discovery of Resultant Security Level
After a TLS layer is established in an LDAP session, both parties
are to each independently decide whether or not to continue based on After a TLS layer is established in an LDAP session, both parties are
to each independently decide whether or not to continue based on
local policy and the security level achieved. If either party local policy and the security level achieved. If either party
decides that the security level is inadequate for it to continue, it decides that the security level is inadequate for it to continue, it
SHOULD remove the TLS layer immediately after the TLS SHOULD remove the TLS layer immediately after the TLS (re)negotiation
(re)negotiation has completed (see [Protocol] section 4.14.3 and has completed (see [RFC4511], Section 4.14.3, and Section 3.2 below).
section 3.2 below). Implementations may reevaluate the security Implementations may reevaluate the security level at any time and,
level at any time and, upon finding it inadequate, should remove the upon finding it inadequate, should remove the TLS layer.
TLS layer.
3.1.5. Refresh of Server Capabilities Information 3.1.5. Refresh of Server Capabilities Information
After a TLS layer is established in an LDAP session, the client After a TLS layer is established in an LDAP session, the client
SHOULD discard or refresh all information about the server it SHOULD discard or refresh all information about the server that it
obtained prior to the initiation of the TLS negotiation and not obtained prior to the initiation of the TLS negotiation and that it
obtained through secure mechanisms. This protects against man-in- did not obtain through secure mechanisms. This protects against
the-middle attacks that may have altered any server capabilities man-in-the-middle attacks that may have altered any server
information retrieved prior to TLS layer installation. capabilities information retrieved prior to TLS layer installation.
The server may advertise different capabilities after installing a The server may advertise different capabilities after installing a
TLS layer. In particular, the value of 'supportedSASLMechanisms' TLS layer. In particular, the value of 'supportedSASLMechanisms' may
may be different after a TLS layer has been installed (specifically, be different after a TLS layer has been installed (specifically, the
the EXTERNAL and PLAIN [PLAIN] mechanisms are likely to be listed EXTERNAL and PLAIN [PLAIN] mechanisms are likely to be listed only
only after a TLS layer has been installed). after a TLS layer has been installed).
3.2. Effect of TLS on Authorization State 3.2. Effect of TLS on Authorization State
The establishment, change, and/or closure of TLS may cause the The establishment, change, and/or closure of TLS may cause the
authorization state to move to a new state. This is discussed authorization state to move to a new state. This is discussed
further in Section 4. further in Section 4.
3.3. TLS Ciphersuites 3.3. TLS Ciphersuites
Several issues should be considered when selecting TLS ciphersuites Several issues should be considered when selecting TLS ciphersuites
that are appropriate for use in a given circumstance. These issues that are appropriate for use in a given circumstance. These issues
include the following: include the following:
- The ciphersuite's ability to provide adequate confidentiality - The ciphersuite's ability to provide adequate confidentiality
protection for passwords and other data sent over the transport protection for passwords and other data sent over the transport
connection. Client and server implementers should recognize connection. Client and server implementers should recognize
that some TLS ciphersuites provide no confidentiality protection that some TLS ciphersuites provide no confidentiality
while other ciphersuites that do provide confidentiality protection, while other ciphersuites that do provide
protection may be vulnerable to being cracked using brute force confidentiality protection may be vulnerable to being cracked
methods, especially in light of ever-increasing CPU speeds that using brute force methods, especially in light of ever-
reduce the time needed to successfully mount such attacks. increasing CPU speeds that reduce the time needed to
successfully mount such attacks.
- Client and server implementers should carefully consider the - Client and server implementers should carefully consider the
value of the password or data being protected versus the level value of the password or data being protected versus the level
of confidentiality protection provided by the ciphersuite to of confidentiality protection provided by the ciphersuite to
ensure that the level of protection afforded by the ciphersuite ensure that the level of protection afforded by the ciphersuite
is appropriate. is appropriate.
- The ciphersuite's vulnerability (or lack thereof) to man-in-the- - The ciphersuite's vulnerability (or lack thereof) to man-in-the-
middle attacks. Ciphersuites vulnerable to man-in-the-middle middle attacks. Ciphersuites vulnerable to man-in-the-middle
attacks SHOULD NOT be used to protect passwords or sensitive attacks SHOULD NOT be used to protect passwords or sensitive
data, unless the network configuration is such that the danger data, unless the network configuration is such that the danger
of a man-in-the-middle attack is negligible. of a man-in-the-middle attack is negligible.
- After a TLS negotiation (either initial or subsequent) is - After a TLS negotiation (either initial or subsequent) is
completed, both protocol peers should independently verify that completed, both protocol peers should independently verify that
the security services provided by the negotiated ciphersuite are the security services provided by the negotiated ciphersuite are
adequate for the intended use of the LDAP session. If not, the adequate for the intended use of the LDAP session. If they are
TLS layer should be closed. not, the TLS layer should be closed.
4. Authorization State 4. Authorization State
Every LDAP session has an associated authorization state. This Every LDAP session has an associated authorization state. This state
state is comprised of numerous factors such as what (if any) is comprised of numerous factors such as what (if any) authentication
authorization state has been established, how it was established, state has been established, how it was established, and what security
and what security services are in place. Some factors may be services are in place. Some factors may be determined and/or
determined and/or affected by protocol events (e.g., Bind, StartTLS, affected by protocol events (e.g., Bind, StartTLS, or TLS closure),
or TLS closure), and some factors may be determined by external and some factors may be determined by external events (e.g., time of
events (e.g., time of day or server load). day or server load).
While it is often convenient to view authorization state in While it is often convenient to view authorization state in
simplistic terms (as we often do in this technical specification) simplistic terms (as we often do in this technical specification)
such as "an anonymous state", it is noted that authorization systems such as "an anonymous state", it is noted that authorization systems
in LDAP implementations commonly involve many factors which in LDAP implementations commonly involve many factors that
interrelate in complex manners. interrelate in complex manners.
Authorization in LDAP is a local matter. One of the key factors in Authorization in LDAP is a local matter. One of the key factors in
making authorization decisions is authorization identity. The Bind making authorization decisions is authorization identity. The Bind
operation defined in section 4.2 of [Protocol] and discussed further operation (defined in Section 4.2 of [RFC4511] and discussed further
in section 5 below allows information to be exchanged between the in Section 5 below) allows information to be exchanged between the
client and server to establish an authorization identity for the client and server to establish an authorization identity for the LDAP
LDAP session. The Bind operation may also be used to move the LDAP session. The Bind operation may also be used to move the LDAP
session to an anonymous authorization state (see section 5.1.1). session to an anonymous authorization state (see Section 5.1.1).
Upon initial establishment of the LDAP session, the session has an Upon initial establishment of the LDAP session, the session has an
anonymous authorization identity. Among other things this implies anonymous authorization identity. Among other things this implies
that the client need not send a BindRequest in the first PDU of the that the client need not send a BindRequest in the first PDU of the
LDAP message layer. The client may send any operation request prior LDAP message layer. The client may send any operation request prior
to performing a Bind operation, and the server MUST treat it as if to performing a Bind operation, and the server MUST treat it as if it
it had been performed after an anonymous Bind operation (section had been performed after an anonymous Bind operation (Section 5.1.1).
5.1.1).
Upon receipt of a Bind request, the server immediately moves the Upon receipt of a Bind request, the server immediately moves the
session to an anonymous authorization state. If the Bind request is session to an anonymous authorization state. If the Bind request is
successful, the session is moved to the requested authentication successful, the session is moved to the requested authentication
state with its associated authorization state. Otherwise, the state with its associated authorization state. Otherwise, the
session remains in an anonymous state. session remains in an anonymous state.
It is noted that other events both internal and external to LDAP may It is noted that other events both internal and external to LDAP may
result in the authentication and authorization states being moved to result in the authentication and authorization states being moved to
an anonymous one. For instance, the establishment, change or an anonymous one. For instance, the establishment, change, or
closure of data security services may result in a move to an closure of data security services may result in a move to an
anonymous state, or the user's credential information (e.g., anonymous state, or the user's credential information (e.g.,
certificate) may have expired. The former is an example of an event certificate) may have expired. The former is an example of an event
internal to LDAP whereas the latter is an example of an event internal to LDAP, whereas the latter is an example of an event
external to LDAP. external to LDAP.
5. Bind Operation 5. Bind Operation
The Bind operation ([Protocol] section 4.2) allows authentication The Bind operation ([RFC4511], Section 4.2) allows authentication
information to be exchanged between the client and server to information to be exchanged between the client and server to
establish a new authorization state. establish a new authorization state.
The Bind request typically specifies the desired authentication The Bind request typically specifies the desired authentication
identity. Some Bind mechanisms also allow the client to specify the identity. Some Bind mechanisms also allow the client to specify the
authorization identity. If the authorization identity is not authorization identity. If the authorization identity is not
specified, the server derives it from the authentication identity in specified, the server derives it from the authentication identity in
an implementation-specific manner. an implementation-specific manner.
If the authorization identity is specified, the server MUST verify If the authorization identity is specified, the server MUST verify
that the client's authentication identity is permitted to assume that the client's authentication identity is permitted to assume
(e.g., proxy for) the asserted authorization identity. The server (e.g., proxy for) the asserted authorization identity. The server
MUST reject the Bind operation with an invalidCredentials resultCode MUST reject the Bind operation with an invalidCredentials resultCode
in the Bind response if the client is not so authorized. in the Bind response if the client is not so authorized.
5.1. Simple Authentication Method 5.1. Simple Authentication Method
The simple authentication method of the Bind Operation provides The simple authentication method of the Bind Operation provides three
three authentication mechanisms: authentication mechanisms:
- An anonymous authentication mechanism (section 5.1.1). - An anonymous authentication mechanism (Section 5.1.1).
- An unauthenticated authentication mechanism (section 5.1.2). - An unauthenticated authentication mechanism (Section 5.1.2).
- A name/password authentication mechanism using credentials - A name/password authentication mechanism using credentials
consisting of a name (in the form of an LDAP distinguished name consisting of a name (in the form of an LDAP distinguished name
[LDAPDN]) and a password (section 5.1.3). [RFC4514]) and a password (Section 5.1.3).
5.1.1. Anonymous Authentication Mechanism of Simple Bind 5.1.1. Anonymous Authentication Mechanism of Simple Bind
An LDAP client may use the anonymous authentication mechanism of the An LDAP client may use the anonymous authentication mechanism of the
simple Bind method to explicitly establish an anonymous simple Bind method to explicitly establish an anonymous authorization
authorization state by sending a Bind request with a name value of state by sending a Bind request with a name value of zero length and
zero length and specifying the simple authentication choice specifying the simple authentication choice containing a password
containing a password value of zero length. value of zero length.
5.1.2. Unauthenticated Authentication Mechanism of Simple Bind
5.1.2. Unauthenticated Authentication Mechanism of Simple Bind
An LDAP client may use the unauthenticated authentication mechanism An LDAP client may use the unauthenticated authentication mechanism
of the simple Bind method to establish an anonymous authorization of the simple Bind method to establish an anonymous authorization
state by sending a Bind request with a name value (a distinguished state by sending a Bind request with a name value (a distinguished
name in LDAP string form [LDAPDN] of non-zero length) and specifying name in LDAP string form [RFC4514] of non-zero length) and specifying
the simple authentication choice containing a password value of zero the simple authentication choice containing a password value of zero
length. length.
The distinguished name value provided by the client is intended to The distinguished name value provided by the client is intended to be
be used for trace (e.g., logging) purposes only. The value is not used for trace (e.g., logging) purposes only. The value is not to be
to be authenticated or otherwise validated (including verification authenticated or otherwise validated (including verification that the
that the DN refers to an existing directory object). The value is DN refers to an existing directory object). The value is not to be
not to be used (directly or indirectly) for authorization purposes. used (directly or indirectly) for authorization purposes.
Unauthenticated Bind operations can have significant security issues Unauthenticated Bind operations can have significant security issues
(see section 6.3.1). In particular, users intending to perform (see Section 6.3.1). In particular, users intending to perform
Name/Password Authentication may inadvertently provide an empty Name/Password Authentication may inadvertently provide an empty
password and thus cause poorly implemented clients to request password and thus cause poorly implemented clients to request
Unauthenticated access. Clients SHOULD be implemented to require Unauthenticated access. Clients SHOULD be implemented to require
user selection of the Unauthenticated Authentication Mechanism by user selection of the Unauthenticated Authentication Mechanism by
means other than user input of an empty password. Clients SHOULD means other than user input of an empty password. Clients SHOULD
disallow an empty password input to a Name/Password Authentication disallow an empty password input to a Name/Password Authentication
user interface. Additionally, Servers SHOULD by default fail user interface. Additionally, Servers SHOULD by default fail
Unauthenticated Bind requests with a resultCode of Unauthenticated Bind requests with a resultCode of
unwillingToPerform. unwillingToPerform.
5.1.3. Name/Password Authentication Mechanism of Simple Bind 5.1.3. Name/Password Authentication Mechanism of Simple Bind
An LDAP client may use the name/password authentication mechanism of An LDAP client may use the name/password authentication mechanism of
the simple Bind method to establish an authenticated authorization the simple Bind method to establish an authenticated authorization
state by sending a Bind request with a name value (a distinguished state by sending a Bind request with a name value (a distinguished
name in LDAP string form [LDAPDN] of non-zero length) and specifying name in LDAP string form [RFC4514] of non-zero length) and specifying
the simple authentication choice containing an OCTET STRING password the simple authentication choice containing an OCTET STRING password
value of non-zero length. value of non-zero length.
Servers that map the DN sent in the Bind request to a directory Servers that map the DN sent in the Bind request to a directory entry
entry with an associated set of one or more passwords used with this with an associated set of one or more passwords used with this
mechanism will compare the presented password to that set of mechanism will compare the presented password to that set of
passwords. The presented password is considered valid if it matches passwords. The presented password is considered valid if it matches
any member of this set. any member of this set.
A resultCode of invalidDNSyntax indicates that the DN sent in the A resultCode of invalidDNSyntax indicates that the DN sent in the
name value is syntactically invalid. A resultCode of name value is syntactically invalid. A resultCode of
invalidCredentials indicates that the DN is syntactically correct invalidCredentials indicates that the DN is syntactically correct but
but not valid for purposes of authentication, or the password is not not valid for purposes of authentication, that the password is not
valid for the DN or the server otherwise considers the credentials valid for the DN, or that the server otherwise considers the
to be invalid. A resultCode of success indicates that the credentials invalid. A resultCode of success indicates that the
credentials are valid and the server is willing to provide service credentials are valid and that the server is willing to provide
to the entity these credentials identify. service to the entity these credentials identify.
Server behavior is undefined for Bind requests specifying the Server behavior is undefined for Bind requests specifying the
name/password authentication mechanism with a zero-length name value name/password authentication mechanism with a zero-length name value
and a password value of non-zero length. and a password value of non-zero length.
The name/password authentication mechanism of the simple Bind method The name/password authentication mechanism of the simple Bind method
is not suitable for authentication in environments without is not suitable for authentication in environments without
confidentiality protection. confidentiality protection.
5.2. SASL Authentication Method 5.2. SASL Authentication Method
The sasl authentication method of the Bind Operation provides The sasl authentication method of the Bind Operation provides
facilities for using any SASL mechanism including authentication facilities for using any SASL mechanism including authentication
mechanisms and other services (e.g., data security services). mechanisms and other services (e.g., data security services).
5.2.1. SASL Protocol Profile 5.2.1. SASL Protocol Profile
LDAP allows authentication via any SASL mechanism [SASL]. As LDAP LDAP allows authentication via any SASL mechanism [RFC4422]. As LDAP
includes native anonymous and name/password (plain text) includes native anonymous and name/password (plain text)
authentication methods, the ANONYMOUS [ANONYMOUS] and PLAIN [PLAIN] authentication methods, the ANONYMOUS [RFC4505] and PLAIN [PLAIN]
SASL mechanisms are typically not used with LDAP. SASL mechanisms are typically not used with LDAP.
Each protocol that utilizes SASL services is required to supply Each protocol that utilizes SASL services is required to supply
certain information profiling the way they are exposed through the certain information profiling the way they are exposed through the
protocol ([SASL] section 4). This section explains how each of protocol ([RFC4422], Section 4). This section explains how each of
these profiling requirements are met by LDAP. these profiling requirements is met by LDAP.
5.2.1.1. SASL Service Name for LDAP 5.2.1.1. SASL Service Name for LDAP
The SASL service name for LDAP is "ldap", which has been registered The SASL service name for LDAP is "ldap", which has been registered
with the IANA as a SASL service name. with the IANA as a SASL service name.
5.2.1.2. SASL Authentication Initiation and Protocol Exchange 5.2.1.2. SASL Authentication Initiation and Protocol Exchange
SASL authentication is initiated via a BindRequest message SASL authentication is initiated via a BindRequest message
([Protocol] section 4.2) with the following parameters: ([RFC4511], Section 4.2) with the following parameters:
- The version is 3. - The version is 3.
- The AuthenticationChoice is sasl. - The AuthenticationChoice is sasl.
- The mechanism element of the SaslCredentials sequence contains - The mechanism element of the SaslCredentials sequence contains
the value of the desired SASL mechanism. the value of the desired SASL mechanism.
- The optional credentials field of the SaslCredentials sequence - The optional credentials field of the SaslCredentials sequence
MAY be used to provide an initial client response for MAY be used to provide an initial client response for mechanisms
mechanisms that are defined to have the client send data first that are defined to have the client send data first (see
(see [SASL] sections 3 and 5 ). [RFC4422], Sections 3 and 5).
In general, a SASL authentication protocol exchange consists of a In general, a SASL authentication protocol exchange consists of a
series of server challenges and client responses, the contents of series of server challenges and client responses, the contents of
which are specific to and defined by the SASL mechanism. Thus for which are specific to and defined by the SASL mechanism. Thus, for
some SASL authentication mechanisms, it may be necessary for the some SASL authentication mechanisms, it may be necessary for the
client to respond to one or more server challenges by sending client to respond to one or more server challenges by sending
BindRequest messages multiple times. A challenge is indicated by BindRequest messages multiple times. A challenge is indicated by the
the server sending a BindResponse message with the resultCode set to server sending a BindResponse message with the resultCode set to
saslBindInProgress. This indicates that the server requires the saslBindInProgress. This indicates that the server requires the
client to send a new BindRequest message with the same SASL client to send a new BindRequest message with the same SASL mechanism
mechanism to continue the authentication process. to continue the authentication process.
To the LDAP message layer, these challenges and responses are opaque To the LDAP message layer, these challenges and responses are opaque
binary tokens of arbitrary length. LDAP servers use the binary tokens of arbitrary length. LDAP servers use the
serverSaslCreds field (an OCTET STRING) in a BindResponse message to serverSaslCreds field (an OCTET STRING) in a BindResponse message to
transmit each challenge. LDAP clients use the credentials field transmit each challenge. LDAP clients use the credentials field (an
(an OCTET STRING) in the SaslCredentials sequence of a BindRequest OCTET STRING) in the SaslCredentials sequence of a BindRequest
message to transmit each response. Note that unlike some Internet message to transmit each response. Note that unlike some Internet
protocols where SASL is used, LDAP is not text based and does not protocols where SASL is used, LDAP is not text based and does not
Base64-transform these challenge and response values. Base64-transform these challenge and response values.
Clients sending a BindRequest message with the sasl choice selected Clients sending a BindRequest message with the sasl choice selected
SHOULD send a zero-length value in the name field. Servers SHOULD send a zero-length value in the name field. Servers receiving
receiving a BindRequest message with the sasl choice selected SHALL a BindRequest message with the sasl choice selected SHALL ignore any
ignore any value in the name field. value in the name field.
A client may abort a SASL Bind negotiation by sending a BindRequest A client may abort a SASL Bind negotiation by sending a BindRequest
message with a different value in the mechanism field of message with a different value in the mechanism field of
SaslCredentials or with an AuthenticationChoice other than sasl. SaslCredentials or with an AuthenticationChoice other than sasl.
If the client sends a BindRequest with the sasl mechanism field as If the client sends a BindRequest with the sasl mechanism field as an
an empty string, the server MUST return a BindResponse with a empty string, the server MUST return a BindResponse with a resultCode
resultCode of authMethodNotSupported. This will allow the client to of authMethodNotSupported. This will allow the client to abort a
abort a negotiation if it wishes to try again with the same SASL negotiation if it wishes to try again with the same SASL mechanism.
mechanism.
The server indicates completion of the SASL challenge-response The server indicates completion of the SASL challenge-response
exchange by responding with a BindResponse in which the resultCode exchange by responding with a BindResponse in which the resultCode
value is not saslBindInProgress. value is not saslBindInProgress.
The serverSaslCreds field in the BindResponse can be used to include The serverSaslCreds field in the BindResponse can be used to include
an optional challenge with a success notification for mechanisms an optional challenge with a success notification for mechanisms that
which are defined to have the server send additional data along with are defined to have the server send additional data along with the
the indication of successful completion. indication of successful completion.
5.2.1.3. Optional Fields 5.2.1.3. Optional Fields
As discussed above, LDAP provides an optional field for carrying an As discussed above, LDAP provides an optional field for carrying an
initial response in the message initiating the SASL exchange and initial response in the message initiating the SASL exchange and
provides an optional field for carrying additional data in the provides an optional field for carrying additional data in the
message indicating outcome of the authentication exchange. As the message indicating the outcome of the authentication exchange. As
mechanism-specific content in these fields may be zero-length, SASL the mechanism-specific content in these fields may be zero length,
requires protocol specifications to detail how an empty field is SASL requires protocol specifications to detail how an empty field is
distinguished from an absent field. distinguished from an absent field.
Zero-length initial response data is distinguished from no initial Zero-length initial response data is distinguished from no initial
response data in the initiating message, a BindRequest PDU, by the response data in the initiating message, a BindRequest PDU, by the
presence of the SaslCredentials.credentials OCTET STRING (of length presence of the SaslCredentials.credentials OCTET STRING (of length
zero) in that PDU. If the client does not intend to send an zero) in that PDU. If the client does not intend to send an initial
initial response with the BindRequest initiating the SASL exchange, response with the BindRequest initiating the SASL exchange, it MUST
it MUST omit the SaslCredentials.credentials OCTET STRING (rather omit the SaslCredentials.credentials OCTET STRING (rather than
than including an zero-length OCTET STRING). include an zero-length OCTET STRING).
Zero-length additional data is distinguished from no additional Zero-length additional data is distinguished from no additional
response data in the outcome message, a BindResponse PDU, by the response data in the outcome message, a BindResponse PDU, by the
presence of the serverSaslCreds OCTET STRING (of length zero) in presence of the serverSaslCreds OCTET STRING (of length zero) in that
that PDU. If a server does not intend to send additional data in PDU. If a server does not intend to send additional data in the
the BindResponse message indicating outcome of the exchange, the BindResponse message indicating outcome of the exchange, the server
server SHALL omit the serverSaslCreds OCTET STRING (rather than SHALL omit the serverSaslCreds OCTET STRING (rather than including a
including a zero-length OCTET STRING). zero-length OCTET STRING).
5.2.1.4. Octet Where Negotiated Security Layers Take Effect 5.2.1.4. Octet Where Negotiated Security Layers Take Effect
SASL layers take effect following the transmission by the server and SASL layers take effect following the transmission by the server and
reception by the client of the final BindResponse in the SASL reception by the client of the final BindResponse in the SASL
exchange with a resultCode of success. exchange with a resultCode of success.
Once a SASL layer providing data integrity or confidentiality Once a SASL layer providing data integrity or confidentiality
services takes effect, the layer remains in effect until a new layer services takes effect, the layer remains in effect until a new layer
is installed (i.e. at the first octet following the final is installed (i.e., at the first octet following the final
BindResponse of the Bind operation that caused the new layer to take BindResponse of the Bind operation that caused the new layer to take
effect). Thus, an established SASL layer is not affected by a effect). Thus, an established SASL layer is not affected by a failed
failed or non-SASL Bind. or non-SASL Bind.
5.2.1.5. Determination of Supported SASL Mechanisms 5.2.1.5. Determination of Supported SASL Mechanisms
Clients may determine the SASL mechanisms a server supports by Clients may determine the SASL mechanisms a server supports by
reading the 'supportedSASLMechanisms' attribute from the root DSE reading the 'supportedSASLMechanisms' attribute from the root DSE
(DSA-Specific Entry) ([Models] section 5.1). The values of this (DSA-Specific Entry) ([RFC4512], Section 5.1). The values of this
attribute, if any, list the mechanisms the server supports in the attribute, if any, list the mechanisms the server supports in the
current LDAP session state. LDAP servers SHOULD allow all clients-- current LDAP session state. LDAP servers SHOULD allow all clients --
even those with an anonymous authorization--to retrieve the even those with an anonymous authorization -- to retrieve the
'supportedSASLMechanisms' attribute of the root DSE both before and 'supportedSASLMechanisms' attribute of the root DSE both before and
after the SASL authentication exchange. The purpose of the latter after the SASL authentication exchange. The purpose of the latter is
is to allow the client to detect possible downgrade attacks (see to allow the client to detect possible downgrade attacks (see Section
section 6.4 and [SASL] section 6.1.2). 6.4 and [RFC4422], Section 6.1.2).
Because SASL mechanisms provide critical security functions, clients Because SASL mechanisms provide critical security functions, clients
and servers should be configurable to specify what mechanisms are and servers should be configurable to specify what mechanisms are
acceptable and allow only those mechanisms to be used. Both clients acceptable and allow only those mechanisms to be used. Both clients
and servers must confirm that the negotiated security level meets and servers must confirm that the negotiated security level meets
their requirements before proceeding to use the session. their requirements before proceeding to use the session.
5.2.1.6. Rules for Using SASL Layers 5.2.1.6. Rules for Using SASL Layers
Upon installing a SASL layer, the client SHOULD discard or refresh Upon installing a SASL layer, the client SHOULD discard or refresh
all information about the server it obtained prior to the initiation all information about the server that it obtained prior to the
of the SASL negotiation and not obtained through secure mechanisms. initiation of the SASL negotiation and that it did not obtain through
secure mechanisms.
If a lower level security layer (such as TLS) is installed, any SASL If a lower-level security layer (such as TLS) is installed, any SASL
layer SHALL be layered on top of such security layers regardless of layer SHALL be layered on top of such security layers regardless of
the order of their negotiation. In all other respects, the SASL the order of their negotiation. In all other respects, the SASL
layer and other security layers act independently, e.g., if both a layer and other security layers act independently, e.g., if both a
TLS layer and a SASL layer are in effect then removing the TLS layer TLS layer and a SASL layer are in effect, then removing the TLS layer
does not affect the continuing service of the SASL layer. does not affect the continuing service of the SASL layer.
5.2.1.7. Support for Multiple Authentications 5.2.1.7. Support for Multiple Authentications
LDAP supports multiple SASL authentications as defined in [SASL] LDAP supports multiple SASL authentications as defined in [RFC4422],
section 4. Section 4.
5.2.1.8. SASL Authorization Identities 5.2.1.8. SASL Authorization Identities
Some SASL mechanisms allow clients to request a desired Some SASL mechanisms allow clients to request a desired authorization
authorization identity for the LDAP session ([SASL] section 3.4. identity for the LDAP session ([RFC4422], Section 3.4). The decision
The decision to allow or disallow the current authentication to allow or disallow the current authentication identity to have
identity to have access to the requested authorization identity is a access to the requested authorization identity is a matter of local
matter of local policy. The authorization identity is a string of policy. The authorization identity is a string of UTF-8 [RFC3629]
UTF-8 [RFC3629] encoded [Unicode] characters corresponding to the encoded [Unicode] characters corresponding to the following Augmented
following ABNF [RFC2234bis] grammar: Backus-Naur Form (ABNF) [RFC4234] grammar:
authzId = dnAuthzId / uAuthzId authzId = dnAuthzId / uAuthzId
; distinguished-name-based authz id ; distinguished-name-based authz id
dnAuthzId = "dn:" distinguishedName dnAuthzId = "dn:" distinguishedName
; unspecified authorization id, UTF-8 encoded ; unspecified authorization id, UTF-8 encoded
uAuthzId = "u:" userid uAuthzId = "u:" userid
userid = *UTF8 ; syntax unspecified userid = *UTF8 ; syntax unspecified
where the distinguishedName rule is defined in section 3 of [LDAPDN] where the distinguishedName rule is defined in Section 3 of [RFC4514]
and the UTF8 rule is defined in section 1.4 of [Models]. and the UTF8 rule is defined in Section 1.4 of [RFC4512].
The dnAuthzId choice is used to assert authorization identities in The dnAuthzId choice is used to assert authorization identities in
the form of a distinguished name to be matched in accordance with the form of a distinguished name to be matched in accordance with the
the distinguishedNameMatch matching rule [Syntaxes]. There is no distinguishedNameMatch matching rule ([RFC4517], Section 4.2.15).
requirement that the asserted distinguishedName value be that of an There is no requirement that the asserted distinguishedName value be
entry in the directory. that of an entry in the directory.
The uAuthzId choice allows clients to assert an authorization The uAuthzId choice allows clients to assert an authorization
identity that is not in distinguished name form. The format of identity that is not in distinguished name form. The format of
userid is defined only as a sequence of UTF-8 [RFC3629] encoded userid is defined only as a sequence of UTF-8 [RFC3629] encoded
[Unicode] characters, and any further interpretation is a local [Unicode] characters, and any further interpretation is a local
matter. For example, the userid could identify a user of a specific matter. For example, the userid could identify a user of a specific
directory service, be a login name or be an email address. A directory service, be a login name, or be an email address. A
uAuthzId SHOULD NOT be assumed to be globally unique. To compare uAuthzId SHOULD NOT be assumed to be globally unique. To compare
uAuthzID values, each uAuthzID value MUST be prepared as a "query" uAuthzId values, each uAuthzId value MUST be prepared as a "query"
string using [RFC4013] and then the two values are compared octet- string ([RFC3454], Section 7) using the SASLprep [RFC4013] algorithm,
wise. and then the two values are compared octet-wise.
The above grammar is extensible. The authzId production may be The above grammar is extensible. The authzId production may be
extended to support additional forms of identities. Each form is extended to support additional forms of identities. Each form is
distinguished by its unique prefix (see section 3.12 of [LDAPIANA] distinguished by its unique prefix (see Section 3.12 of [RFC4520] for
for registration requirements). registration requirements).
5.2.2. SASL Semantics Within LDAP 5.2.2. SASL Semantics within LDAP
Implementers must take care to maintain the semantics of SASL Implementers must take care to maintain the semantics of SASL
specifications when handling data that has different semantics in specifications when handling data that has different semantics in the
the LDAP protocol. LDAP protocol.
For example, the SASL DIGEST-MD5 authentication mechanism [RFC2829] For example, the SASL DIGEST-MD5 authentication mechanism
utilizes an authentication identity and a realm which are [DIGEST-MD5] utilizes an authentication identity and a realm that are
syntactically simple strings and semantically simple username and syntactically simple strings and semantically simple username
realm values ([DIGEST-MD5] section 2.1). These values are not LDAP [RFC4013] and realm values. These values are not LDAP DNs, and there
DNs, and there is no requirement that they be represented or treated is no requirement that they be represented or treated as such.
as such.
5.2.3. SASL EXTERNAL Authentication Mechanism 5.2.3. SASL EXTERNAL Authentication Mechanism
A client can use the SASL EXTERNAL [SASL] mechanism to request the A client can use the SASL EXTERNAL ([RFC4422], Appendix A) mechanism
LDAP server to authenticate and establish a resulting authorization to request the LDAP server to authenticate and establish a resulting
identity using security credentials exchanged by a lower security authorization identity using security credentials exchanged by a
layer (such as by TLS authentication). If the client's lower security layer (such as by TLS authentication). If the
authentication credentials have not been established at a lower client's authentication credentials have not been established at a
security layer, the SASL EXTERNAL Bind MUST fail with a resultCode lower security layer, the SASL EXTERNAL Bind MUST fail with a
of inappropriateAuthentication. Although this situation has the resultCode of inappropriateAuthentication. Although this situation
effect of leaving the LDAP session in an anonymous state (section has the effect of leaving the LDAP session in an anonymous state
4), the state of any installed security layer is unaffected. (Section 4), the state of any installed security layer is unaffected.
A client may either request that its authorization identity be A client may either request that its authorization identity be
automatically derived from its authentication credentials exchanged automatically derived from its authentication credentials exchanged
at a lower security layer or it may explicitly provide a desired at a lower security layer, or it may explicitly provide a desired
authorization identity. The former is known as an implicit authorization identity. The former is known as an implicit
assertion, and the latter as an explicit assertion. assertion, and the latter as an explicit assertion.
5.2.3.1. Implicit Assertion 5.2.3.1. Implicit Assertion
An implicit authorization identity assertion is performed by
invoking a Bind request of the SASL form using the EXTERNAL
mechanism name that does not include the optional credentials field
(found within the SaslCredentials sequence in the BindRequest). The
server will derive the client's authorization identity from the
authentication identity supplied by a security layer (e.g., a public
key certificate used during TLS layer installation) according to
local policy. The underlying mechanics of how this is accomplished
are implementation specific.
5.2.3.2. Explicit Assertion An implicit authorization identity assertion is performed by invoking
a Bind request of the SASL form using the EXTERNAL mechanism name
that does not include the optional credentials field (found within
the SaslCredentials sequence in the BindRequest). The server will
derive the client's authorization identity from the authentication
identity supplied by a security layer (e.g., a public key certificate
used during TLS layer installation) according to local policy. The
underlying mechanics of how this is accomplished are implementation
specific.
An explicit authorization identity assertion is performed by 5.2.3.2. Explicit Assertion
invoking a Bind request of the SASL form using the EXTERNAL
mechanism name that includes the credentials field (found within the
SaslCredentials sequence in the BindRequest). The value of the
credentials field (an OCTET STRING) is the asserted authorization
identity and MUST be constructed as documented in section 5.2.1.8.
6. Security Considerations An explicit authorization identity assertion is performed by invoking
a Bind request of the SASL form using the EXTERNAL mechanism name
that includes the credentials field (found within the SaslCredentials
sequence in the BindRequest). The value of the credentials field (an
OCTET STRING) is the asserted authorization identity and MUST be
constructed as documented in Section 5.2.1.8.
6. Security Considerations
Security issues are discussed throughout this document. The Security issues are discussed throughout this document. The
unsurprising conclusion is that security is an integral and unsurprising conclusion is that security is an integral and necessary
necessary part of LDAP. This section discusses a number of LDAP- part of LDAP. This section discusses a number of LDAP-related
related security considerations. security considerations.
6.1. General LDAP Security Considerations 6.1. General LDAP Security Considerations
LDAP itself provides no security or protection from accessing or LDAP itself provides no security or protection from accessing or
updating the directory by other means than through the LDAP updating the directory by means other than through the LDAP protocol,
protocol, e.g., from inspection of server database files by database e.g., from inspection of server database files by database
administrators. administrators.
Sensitive data may be carried in almost any LDAP message and its Sensitive data may be carried in almost any LDAP message, and its
disclosure may be subject to privacy laws or other legal regulation disclosure may be subject to privacy laws or other legal regulation
in many countries. Implementers should take appropriate measures to in many countries. Implementers should take appropriate measures to
protect sensitive data from disclosure to unauthorized entities. protect sensitive data from disclosure to unauthorized entities.
A session on which the client has not established data integrity and A session on which the client has not established data integrity and
privacy services (e.g., via StartTLS, IPsec or a suitable SASL privacy services (e.g., via StartTLS, IPsec, or a suitable SASL
mechanism) is subject to man-in-the-middle attacks to view and mechanism) is subject to man-in-the-middle attacks to view and modify
modify information in transit. Client and server implementers information in transit. Client and server implementers SHOULD take
SHOULD take measures to protect sensitive data in the LDAP session measures to protect sensitive data in the LDAP session from these
from these attacks by using data protection services as discussed in attacks by using data protection services as discussed in this
this document. Clients and servers should provide the ability to be document. Clients and servers should provide the ability to be
configured to require these protections. A resultCode of configured to require these protections. A resultCode of
confidentialityRequired indicates that the server requires confidentialityRequired indicates that the server requires
establishment of (stronger) data confidentiality protection in order establishment of (stronger) data confidentiality protection in order
to perform the requested operation. to perform the requested operation.
Access control should always be applied when reading sensitive Access control should always be applied when reading sensitive
information or updating directory information. information or updating directory information.
Various security factors, including authentication and authorization Various security factors, including authentication and authorization
information and data security services may change during the course information and data security services may change during the course
of the LDAP session, or even during the performance of a particular of the LDAP session, or even during the performance of a particular
operation. Implementations should be robust in the handling of operation. Implementations should be robust in the handling of
changing security factors. changing security factors.
6.2. StartTLS Security Considerations 6.2. StartTLS Security Considerations
All security gained via use of the StartTLS operation is gained by 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 the use of TLS itself. The StartTLS operation, on its own, does not
provide any additional security. provide any additional security.
The level of security provided through the use of TLS depends The level of security provided through the use of TLS depends
directly on both the quality of the TLS implementation used and the directly on both the quality of the TLS implementation used and the
style of usage of that implementation. Additionally, a man-in-the- style of usage of that implementation. Additionally, a man-in-the-
middle attacker can remove the StartTLS extended operation from the middle attacker can remove the StartTLS extended operation from the
'supportedExtension' attribute of the root DSE. Both parties SHOULD 'supportedExtension' attribute of the root DSE. Both parties SHOULD
independently ascertain and consent to the security level achieved independently ascertain and consent to the security level achieved
once TLS is established and before beginning use of the TLS- once TLS is established and before beginning use of the TLS-
protected session. For example, the security level of the TLS layer protected session. For example, the security level of the TLS layer
might have been negotiated down to plaintext. might have been negotiated down to plaintext.
Clients MUST either warn the user when the security level achieved Clients MUST either warn the user when the security level achieved
does not provide an acceptable level of data confidentiality and/or does not provide an acceptable level of data confidentiality and/or
data integrity protection, or be configurable to refuse to proceed data integrity protection, or be configurable to refuse to proceed
without an acceptable level of security. without an acceptable level of security.
As stated in section 3.1.2, a server may use a local security policy As stated in Section 3.1.2, a server may use a local security policy
to determine whether to successfully complete TLS negotiation. to determine whether to successfully complete TLS negotiation.
Information in the user's certificate that is originated or verified Information in the user's certificate that is originated or verified
by the certification authority should be used by the policy by the certification authority should be used by the policy
administrator when configuring the identification and authorization administrator when configuring the identification and authorization
policy. policy.
Server implementers SHOULD allow server administrators to elect Server implementers SHOULD allow server administrators to elect
whether and when data confidentiality and integrity are required, as whether and when data confidentiality and integrity are required, as
well as elect whether authentication of the client during the TLS well as elect whether authentication of the client during the TLS
handshake is required. handshake is required.
Implementers should be aware of and understand TLS security Implementers should be aware of and understand TLS security
considerations as discussed in the TLS specification [TLS]. considerations as discussed in the TLS specification [RFC4346].
6.3. Bind Operation Security Considerations 6.3. Bind Operation Security Considerations
This section discusses several security considerations relevant to This section discusses several security considerations relevant to
LDAP authentication via the Bind operation. LDAP authentication via the Bind operation.
6.3.1. Unauthenticated Mechanism Security Considerations 6.3.1. Unauthenticated Mechanism Security Considerations
Operational experience shows that clients can (and frequently do) Operational experience shows that clients can (and frequently do)
misuse the unauthenticated authentication mechanism of the simple misuse the unauthenticated authentication mechanism of the simple
Bind method (see section 5.1.2). For example, a client program Bind method (see Section 5.1.2). For example, a client program might
might make a decision to grant access to non-directory information make a decision to grant access to non-directory information on the
on the basis of successfully completing a Bind operation. LDAP basis of successfully completing a Bind operation. LDAP server
server implementations may return a success response to an implementations may return a success response to an unauthenticated
unauthenticated Bind request. This may erroneously leave the client Bind request. This may erroneously leave the client with the
with the impression that the server has successfully authenticated impression that the server has successfully authenticated the
the identity represented by the distinguished name when in reality, identity represented by the distinguished name when in reality, an
an anonymous authorization state has been established. Clients that anonymous authorization state has been established. Clients that use
use the results from a simple Bind operation to make authorization the results from a simple Bind operation to make authorization
decisions should actively detect unauthenticated Bind requests (by decisions should actively detect unauthenticated Bind requests (by
verifying that the supplied password is not empty) and react verifying that the supplied password is not empty) and react
appropriately. appropriately.
6.3.2. Name/Password Mechanism Security Considerations 6.3.2. Name/Password Mechanism Security Considerations
The name/password authentication mechanism of the simple Bind method The name/password authentication mechanism of the simple Bind method
discloses the password to the server, which is an inherent security discloses the password to the server, which is an inherent security
risk. There are other mechanisms such as SASL DIGEST-MD5 [RFC2829] risk. There are other mechanisms, such as SASL DIGEST-MD5
that do not disclose the password to the server. [DIGEST-MD5], that do not disclose the password to the server.
6.3.3. Password-related Security Considerations 6.3.3. Password-Related Security Considerations
LDAP allows multi-valued password attributes. In systems where LDAP allows multi-valued password attributes. In systems where
entries are expected to have one and only one password, entries are expected to have one and only one password,
administrative controls should be provided to enforce this behavior. administrative controls should be provided to enforce this behavior.
The use of clear text passwords and other unprotected authentication The use of clear text passwords and other unprotected authentication
credentials is strongly discouraged over open networks when the credentials is strongly discouraged over open networks when the
underlying transport service cannot guarantee confidentiality. LDAP underlying transport service cannot guarantee confidentiality. LDAP
implementations SHOULD NOT by default support authentication methods implementations SHOULD NOT by default support authentication methods
using clear text passwords and other unprotected authentication using clear text passwords and other unprotected authentication
credentials unless the data on the session is protected using TLS or credentials unless the data on the session is protected using TLS or
other data confidentiality and data integrity protection. other data confidentiality and data integrity protection.
The transmission of passwords in the clear--typically for The transmission of passwords in the clear -- typically for
authentication or modification--poses a significant security risk. authentication or modification -- poses a significant security risk.
This risk can be avoided by using SASL authentication [SASL] This risk can be avoided by using SASL authentication [RFC4422]
mechanisms that do not transmit passwords in the clear or by mechanisms that do not transmit passwords in the clear or by
negotiating transport or session layer data confidentiality services negotiating transport or session layer data confidentiality services
before transmitting password values. before transmitting password values.
To mitigate the security risks associated with the transfer of To mitigate the security risks associated with the transfer of
passwords, a server implementation that supports any password-based passwords, a server implementation that supports any password-based
authentication mechanism that transmits passwords in the clear MUST authentication mechanism that transmits passwords in the clear MUST
support a policy mechanism that at the time of authentication or support a policy mechanism that at the time of authentication or
password modification, requires: password modification, requires that:
A TLS layer has been successfully installed. A TLS layer has been successfully installed.
OR OR
Some other data confidentiality mechanism that protects the Some other data confidentiality mechanism that protects the
password value from eavesdropping has been provided. password value from eavesdropping has been provided.
OR OR
The server returns a resultCode of confidentialityRequired for The server returns a resultCode of confidentialityRequired for
the operation (i.e. name/password Bind with password value, the operation (i.e., name/password Bind with password value,
SASL Bind transmitting a password value in the clear, add or SASL Bind transmitting a password value in the clear, add or
modify including a userPassword value, etc.), even if the modify including a userPassword value, etc.), even if the
password value is correct. password value is correct.
Server implementations may also want to provide policy mechanisms to Server implementations may also want to provide policy mechanisms to
invalidate or otherwise protect accounts in situations where a invalidate or otherwise protect accounts in situations where a server
server detects that a password for an account has been transmitted detects that a password for an account has been transmitted in the
in the clear. clear.
6.3.4. Hashed Password Security Considerations 6.3.4. Hashed Password Security Considerations
Some authentication mechanisms (e.g., DIGEST-MD5) transmit a hash of Some authentication mechanisms (e.g., DIGEST-MD5) transmit a hash of
the password value that may be vulnerable to offline dictionary the password value that may be vulnerable to offline dictionary
attacks. Implementers should take care to protect such hashed attacks. Implementers should take care to protect such hashed
password values during transmission using TLS or other password values during transmission using TLS or other
confidentiality mechanisms. confidentiality mechanisms.
6.4.SASL Security Considerations 6.4. SASL Security Considerations
Until data integrity service is installed on an LDAP session, an Until data integrity service is installed on an LDAP session, an
attacker can modify the transmitted values of the attacker can modify the transmitted values of the
'supportedSASLMechanisms' attribute response and thus downgrade the 'supportedSASLMechanisms' attribute response and thus downgrade the
list of available SASL mechanisms to include only the least secure list of available SASL mechanisms to include only the least secure
mechanism. To detect this type of attack, the client may retrieve mechanism. To detect this type of attack, the client may retrieve
the SASL mechanisms the server makes available both before and after the SASL mechanisms the server makes available both before and after
data integrity service is installed on an LDAP session. If the data integrity service is installed on an LDAP session. If the
client finds that the integrity-protected list (the list obtained client finds that the integrity-protected list (the list obtained
after data integrity service was installed) contains a stronger after data integrity service was installed) contains a stronger
mechanism than those in the previously obtained list, the client mechanism than those in the previously obtained list, the client
should assume the previously obtained list was modified by an should assume the previously obtained list was modified by an
attacker. In this circumstance it is recommended that the client attacker. In this circumstance it is recommended that the client
close the underlying transport connection and then reconnect to close the underlying transport connection and then reconnect to
reestablish the session. reestablish the session.
6.5. Related Security Considerations 6.5. Related Security Considerations
Additional security considerations relating to the various Additional security considerations relating to the various
authentication methods and mechanisms discussed in this document authentication methods and mechanisms discussed in this document
apply and can be found in [SASL], [RFC4013], [StringPrep] and apply and can be found in [RFC4422], [RFC4013], [RFC3454], and
[RFC3629]. [RFC3629].
7. IANA Considerations 7. IANA Considerations
It is requested that the IANA update the LDAP Protocol Mechanism
registry to indicate that this document and [Protocol] provide the
definitive technical specification for the StartTLS
(1.3.6.1.4.1.1466.20037) extended operation.
8. Acknowledgments
This document combines information originally contained in RFC 2251,
RFC 2829 and RFC 2830 which are products of the LDAP Extensions
(LDAPEXT) Working Group.
This document is a product of the IETF LDAP Revision (LDAPBIS) The IANA has updated the LDAP Protocol Mechanism registry to indicate
working group. that this document and [RFC4511] provide the definitive technical
specification for the StartTLS (1.3.6.1.4.1.1466.20037) extended
operation.
9. Normative References The IANA has updated the LDAP LDAPMessage types registry to indicate
that this document and [RFC4511] provide the definitive technical
specification for the bindRequest (0) and bindResponse (1) message
types.
[[Note to the RFC Editor: please replace the citation tags used in The IANA has updated the LDAP Bind Authentication Method registry to
referencing Internet-Drafts with tags of the form RFCnnnn.]] indicate that this document and [RFC4511] provide the definitive
technical specification for the simple (0) and sasl (3) bind
authentication methods.
[LDAPDN] Zeilenga, Kurt D. (editor), "LDAP: String The IANA has updated the LDAP authzid prefixes registry to indicate
Representation of Distinguished Names", draft-ietf- that this document provides the definitive technical specification
ldapbis-dn-xx.txt, a work in progress. for the dnAuthzId (dn:) and uAuthzId (u:) authzid prefixes.
[LDAPIANA] Zeilenga, K., "IANA Considerations for LDAP", draft- 8. Acknowledgements
ietf-ldapbis-bcp64-xx.txt, (a work in progress).
[Matching] Hoffman, Paul and Steve Hanna, "Matching Text Strings This document combines information originally contained in RFC 2251,
in PKIX Certificates", draft-hoffman-pkix-stringmatch- RFC 2829, and RFC 2830. RFC 2251 was a product of the Access,
xx.txt, a work in progress. Searching, and Indexing of Directories (ASID) Working Group. RFC
2829 and RFC 2830 were products of the LDAP Extensions (LDAPEXT)
Working Group.
[Models] Zeilenga, Kurt D. (editor), "LDAP: Directory This document is a product of the IETF LDAP Revision (LDAPBIS)
Information Models", draft-ietf-ldapbis-models-xx.txt, working group.
a work in progress.
[Protocol] Sermersheim, J., "LDAP: The Protocol", draft-ietf- 9. Normative References
ldapbis-protocol-xx.txt, a work in progress.
[RFC791] Information Sciences Institute, "INTERNET PROTOCOL [RFC791] Postel, J., "Internet Protocol", STD 5, RFC 791,
DARPA INTERNET PROGRAM PROTOCOL SPECIFICATION", RFC September 1981.
791, September 1981.
[RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, March 1997. Requirement Levels", BCP 14, RFC 2119, March 1997.
[RFC2234bis] Crocker, D., Ed. and P. Overell, "Augmented BNF for [RFC2460] Deering, S. and R. Hinden, "Internet Protocol, Version 6
Syntax Specifications: ABNF", draft-crocker-abnf- (IPv6) Specification", RFC 2460, December 1998.
rfc2234bis-xx, a work in progress.
[RFC2460] Deering, S., R. Hinden, "Internet Protocol, Version 6 [RFC3454] Hoffman, P. and M. Blanchet, "Preparation of
(IPv6)", RFC 2460, December 1998. Internationalized Strings ("stringprep")", RFC 3454,
December 2002.
[RFC3490] Falstrom, P., P. Hoffman, and A. Costello, [RFC3490] Faltstrom, P., Hoffman, P., and A. Costello,
"Internationalizing Domain Names In Applications "Internationalizing Domain Names in Applications
(IDNA)", RFC 3490, March 2003. (IDNA)", RFC 3490, March 2003.
[RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO [RFC3629] Yergeau, F., "UTF-8, a transformation format of ISO
10646", RFC 3629, STD 63, November 2003. 10646", STD 63, RFC 3629, November 2003.
[RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User [RFC4013] Zeilenga, K., "SASLprep: Stringprep Profile for User
Names and Passwords", RFC 4013, February 2005. Names and Passwords", RFC 4013, February 2005.
[Roadmap] K. Zeilenga, "LDAP: Technical Specification Road Map", [RFC4234] Crocker, D. and P. Overell, "Augmented BNF for Syntax
draft-ietf-ldapbis-roadmap-xx.txt, a work in progress. Specifications: ABNF", RFC 4234, October 2005.
[SASL] Melnikov, A. (editor), "Simple Authentication and [RFC4346] Dierks, T. and E. Rescorla, "The TLS Protocol Version
Security Layer (SASL)", draft-ietf-sasl-rfc2222bis- 1.1", RFC 4346, March 2006.
xx.txt, a work in progress.
[Schema] Dally, K. (editor), "LDAP: User Schema", draft-ietf- [RFC4422] Melnikov, A., Ed. and K. Zeilenga, Ed., "Simple
ldapbis-user-schema-xx.txt, a work in progress. Authentication and Security Layer (SASL)", RFC 4422,
June 2006.
[StringPrep] M. Blanchet, "Preparation of Internationalized Strings [RFC4510] Zeilenga, K., Ed., "Lightweight Directory Access
('stringprep')", draft-hoffman-rfc3454bis-xx.txt, a Protocol (LDAP): Technical Specification Road Map", RFC
work in progress. 4510, June 2006.
[Syntaxes] Legg, S. (editor), "LDAP: Syntaxes and Matching Rules", [RFC4511] Sermersheim, J., Ed., "Lightweight Directory Access
draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress. Protocol (LDAP): The Protocol", RFC 4511, June 2006.
[TLS] Dierks, T. and C. Allen. "The TLS Protocol Version [RFC4512] Zeilenga, K., "Lightweight Directory Access Protocol
1.1", draft-ietf-tls-rfc2246-bis-xx.txt, a work in (LDAP): Directory Information Models", RFC 4512, June
progress. 2006.
[Unicode] The Unicode Consortium, "The Unicode Standard, Version [RFC4514] Zeilenga, K., Ed., "Lightweight Directory Access
3.2.0" is defined by "The Unicode Standard, Version Protocol (LDAP): String Representation of Distinguished
3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201- Names", RFC 4514, June 2006.
61633-5), as amended by the "Unicode Standard Annex
#27: Unicode 3.1"
(http://www.unicode.org/reports/tr27/) and by the
"Unicode Standard Annex #28: Unicode 3.2"
(http://www.unicode.org/reports/tr28/).
10. Informative References [RFC4517] Legg, S., Ed., "Lightweight Directory Access Protocol
(LDAP): Syntaxes and Matching Rules", RFC 4517, June
2006.
[[Note to the RFC Editor: please replace the citation tags used in [RFC4519] Sciberras, A., Ed., "Lightweight Directory Access
referencing Internet-Drafts with tags of the form RFCnnnn.]] Protocol (LDAP): Schema for User Applications", RFC
4519, June 2006.
[ANONYMOUS] Zeilenga, K., "Anonymous SASL Mechanism", draft- [RFC4520] Zeilenga, K., "Internet Assigned Numbers Authority
zeilenga-sasl-anon-xx.txt, a work in progress. (IANA) Considerations for the Lightweight Directory
Access Protocol (LDAP)", BCP 64, RFC 4520, June 2006.
[DIGEST-MD5] Leach, P. C. Newman, and A. Melnikov, "Using Digest [Unicode] The Unicode Consortium, "The Unicode Standard, Version
Authentication as a SASL Mechanism", draft-ietf-sasl- 3.2.0" is defined by "The Unicode Standard, Version 3.0"
rfc2831bis-xx.txt, a work in progress. (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/).
[PLAIN] Zeilenga, K.,"Plain SASL Mechanism", draft-zeilenga- [X.501] ITU-T Rec. X.501, "The Directory: Models", 1993.
sasl-plain-xx.txt, a work in progress.
[RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May 10. Informative References
2000.
[RFC2829] Wahl, M. et al, "Authentication Methods for LDAP", RFC [DIGEST-MD5] Leach, P., Newman, C., and A. Melnikov, "Using Digest
2829, May 2000. Authentication as a SASL Mechanism", Work in Progress,
March 2006.
[PLAIN] Zeilenga, K., "The Plain SASL Mechanism", Work in
Progress, March 2005.
[RFC2828] Shirey, R., "Internet Security Glossary", FYI 36, RFC
2828, May 2000.
[RFC4301] Kent, S. and K. Seo, "Security Architecture for the [RFC4301] Kent, S. and K. Seo, "Security Architecture for the
Internet Protocol", RFC 4301, December 2005. Internet Protocol", RFC 4301, December 2005.
Author's Address [RFC4505] Zeilenga, K., "The Anonymous SASL Mechanism", RFC 4505,
June 2006.
Roger Harrison
Novell, Inc.
1800 S. Novell Place
Provo, UT 84606
USA
+1 801 861 2642
roger_harrison@novell.com
Appendix A. Authentication and Authorization Concepts Appendix A. Authentication and Authorization Concepts
This appendix is non-normative. This appendix is non-normative.
This appendix defines basic terms, concepts, and interrelationships This appendix defines basic terms, concepts, and interrelationships
regarding authentication, authorization, credentials, and identity. regarding authentication, authorization, credentials, and identity.
These concepts are used in describing how various security These concepts are used in describing how various security approaches
approaches are utilized in client authentication and authorization. are utilized in client authentication and authorization.
A.1. Access Control Policy A.1. Access Control Policy
An access control policy is a set of rules defining the protection An access control policy is a set of rules defining the protection of
of resources, generally in terms of the capabilities of persons or resources, generally in terms of the capabilities of persons or other
other entities accessing those resources. Security objects and entities accessing those resources. Security objects and mechanisms,
mechanisms, such as those described here, enable the expression of such as those described here, enable the expression of access control
access control policies and their enforcement. policies and their enforcement.
A.2. Access Control Factors A.2. Access Control Factors
A request, when it is being processed by a server, may be associated A request, when it is being processed by a server, may be associated
with a wide variety of security-related factors ([Protocol] section with a wide variety of security-related factors. The server uses
4.2). The server uses these factors to determine whether and how to these factors to determine whether and how to process the request.
process the request. These are called access control factors These are called access control factors (ACFs). They might include
(ACFs). They might include source IP address, encryption strength, source IP address, encryption strength, the type of operation being
the type of operation being requested, time of day, etc.. Some requested, time of day, etc.. Some factors may be specific to the
factors may be specific to the request itself, others may be request itself; others may be associated with the transport
associated with the transport connection via which the request is connection via which the request is transmitted; and others (e.g.,
transmitted, others (e.g., time of day) may be "environmental". time of day) may be "environmental".
Access control policies are expressed in terms of access control Access control policies are expressed in terms of access control
factors. For example, "a request having ACFs i,j,k can perform factors; for example, "a request having ACFs i,j,k can perform
operation Y on resource Z." The set of ACFs that a server makes operation Y on resource Z". The set of ACFs that a server makes
available for such expressions is implementation-specific. available for such expressions is implementation specific.
A.3. Authentication, Credentials, Identity A.3. Authentication, Credentials, Identity
Authentication credentials are the evidence supplied by one party to Authentication credentials are the evidence supplied by one party to
another, asserting the identity of the supplying party (e.g., a another, asserting the identity of the supplying party (e.g., a user)
user) who is attempting to establish a new authorization state with who is attempting to establish a new authorization state with the
the other party (typically a server). Authentication is the process other party (typically a server). Authentication is the process of
of generating, transmitting, and verifying these credentials and generating, transmitting, and verifying these credentials and thus
thus the identity they assert. An authentication identity is the the identity they assert. An authentication identity is the name
name presented in a credential. presented in a credential.
There are many forms of authentication credentials. The form used There are many forms of authentication credentials. The form used
depends upon the particular authentication mechanism negotiated by depends upon the particular authentication mechanism negotiated by
the parties. X.509 certificates, Kerberos tickets, and simple the parties. X.509 certificates, Kerberos tickets, and simple
identity and password pairs are all examples of authentication identity and password pairs are all examples of authentication
credential forms. Note that an authentication mechanism may credential forms. Note that an authentication mechanism may
constrain the form of authentication identities used with it. constrain the form of authentication identities used with it.
A.4. Authorization Identity A.4. Authorization Identity
An authorization identity is one kind of access control factor. It An authorization identity is one kind of access control factor. It
is the name of the user or other entity that requests that is the name of the user or other entity that requests that operations
operations be performed. Access control policies are often be performed. Access control policies are often expressed in terms
expressed in terms of authorization identities; for example, "entity of authorization identities; for example, "entity X can perform
X can perform operation Y on resource Z." operation Y on resource Z".
The authorization identity of an LDAP session is often semantically The authorization identity of an LDAP session is often semantically
the same as the authentication identity presented by the client, but the same as the authentication identity presented by the client, but
it may be different. SASL allows clients to specify an it may be different. SASL allows clients to specify an authorization
authorization identity distinct from the authentication identity identity distinct from the authentication identity asserted by the
asserted by the client's credentials. This permits agents such as client's credentials. This permits agents such as proxy servers to
proxy servers to authenticate using their own credentials, yet authenticate using their own credentials, yet request the access
request the access privileges of the identity for which they are privileges of the identity for which they are proxying [RFC4422].
proxying [SASL]. Also, the form of authentication identity supplied Also, the form of authentication identity supplied by a service like
by a service like TLS may not correspond to the authorization TLS may not correspond to the authorization identities used to
identities used to express a server's access control policy, express a server's access control policy, thus requiring a server-
requiring a server-specific mapping to be done. The method by which specific mapping to be done. The method by which a server composes
a server composes and validates an authorization identity from the and validates an authorization identity from the authentication
authentication credentials supplied by a client is implementation credentials supplied by a client is implementation specific.
specific.
Appendix B. Summary of Changes Appendix B. Summary of Changes
This appendix is non-normative. This appendix is non-normative.
This appendix summarizes substantive changes made to RFC 2251, RFC This appendix summarizes substantive changes made to RFC 2251, RFC
2829 and RFC 2830. In addition to the specific changes detailed 2829 and RFC 2830. In addition to the specific changes detailed
below, the reader of this document should be aware that numerous below, the reader of this document should be aware that numerous
general editorial changes have been made to the original content general editorial changes have been made to the original content from
from the source documents. These changes include the following: the source documents. These changes include the following:
- The material originally found in RFC 2251 sections 4.2.1 and
4.2.2, RFC 2829 (all sections except sections 2 and 4) and RFC
2830 was combined into a single document
- The combined material was substantially reorganized and edited
to group related subjects, improve the document flow and clarify
intent.
- Changes were made throughout the text to align with definitions
of LDAP protocol layers and IETF security terminology.
- Substantial updates and additions were made to security
considerations from both documents based on current operational
experience.
B.1. Changes Made to RFC 2251
This section summarizes the substantive changes made to sections - The material originally found in RFC 2251 Sections 4.2.1 and 4.2.2,
4.2.1 and 4.2.2 of RFC 2251 by this document. Additional RFC 2829 (all sections except Sections 2 and 4), and RFC 2830 was
substantive changes to section 4.2.1 of RFC 2251 are also documented combined into a single document.
in [Protocol].
B.1.1. Section 4.2.1 (Sequencing of the Bind Request) - The combined material was substantially reorganized and edited to
group related subjects, improve the document flow, and clarify
intent.
- Paragraph 1: Removed the sentence, "If at any stage the client - Changes were made throughout the text to align with definitions of
wishes to abort the bind process it MAY unbind and then drop the LDAP protocol layers and IETF security terminology.
underlying connection." The Unbind operation still permits this
behavior, but it is not documented explicitly.
- Clarified that the session is moved to an anonymous state upon - Substantial updates and additions were made to security
receipt of the BindRequest PDU and that it is only moved to a considerations from both documents based on current operational
non-anonymous state if and when the Bind request is successful. experience.
B.1.2. Section 4.2.2 (Authentication and Other Security Services) B.1. Changes Made to RFC 2251
- RFC 2251 states that anonymous authentication MUST be performed This section summarizes the substantive changes made to Sections
using the simple bind method. This specification defines the 4.2.1 and 4.2.2 of RFC 2251 by this document. Additional substantive
anonymous authentication mechanism of the simple bind method and changes to Section 4.2.1 of RFC 2251 are also documented in
requires all conforming implementations to support it. Other [RFC4511].
authentication mechanisms producing anonymous authentication and
authorization state may also be implemented and used by
conforming implementations.
B.2. Changes Made to RFC 2829 B.1.1. Section 4.2.1 ("Sequencing of the Bind Request")
This section summarizes the substantive changes made to RFC 2829.
B.2.1. Section 4 (Required security mechanisms) - Paragraph 1: Removed the sentence, "If at any stage the client
wishes to abort the bind process it MAY unbind and then drop the
underlying connection". The Unbind operation still permits this
behavior, but it is not documented explicitly.
- The name/password authentication mechanism (see section B.2.5 - Clarified that the session is moved to an anonymous state upon
below) protected by TLS replaces the SASL DIGEST-MD5 mechanism receipt of the BindRequest PDU and that it is only moved to a non-
as LDAP's mandatory-to-implement password-based authentication anonymous state if and when the Bind request is successful.
mechanism. Implementations are encouraged to continue
supporting SASL DIGEST-MD5 [RFC2829].
B.2.2. Section 5.1 (Anonymous authentication procedure) B.1.2. Section 4.2.2 ("Authentication and Other Security Services")
- Clarified that anonymous authentication involves a name value of - RFC 2251 states that anonymous authentication MUST be performed
zero length and a password value of zero length. The using the simple bind method. This specification defines the
unauthenticated authentication mechanism was added to handle anonymous authentication mechanism of the simple bind method and
simple Bind requests involving a name value with a non-zero requires all conforming implementations to support it. Other
length and a password value of zero length. authentication mechanisms producing anonymous authentication and
authorization state may also be implemented and used by conforming
implementations.
B.2.3. Section 6 (Password-based authentication) B.2. Changes Made to RFC 2829
- See section B.2.1. This section summarizes the substantive changes made to RFC 2829.
B.2.4. Section 6.1 (Digest authentication) B.2.1. Section 4 ("Required security mechanisms")
- As the SASL-DIGEST-MD5 mechanism is no longer mandatory to - The name/password authentication mechanism (see Section B.2.5
implement, this section is now historical and was not included below) protected by TLS replaces the SASL DIGEST-MD5 mechanism as
in this document. RFC 2829 section 6.1 continues to document the LDAP's mandatory-to-implement password-based authentication
SASL DIGEST-MD5 authentication mechanism. mechanism. Implementations are encouraged to continue supporting
SASL DIGEST-MD5 [DIGEST-MD5].
B.2.5. Section 6.2 ("simple" authentication choice with TLS) B.2.2. Section 5.1 ("Anonymous authentication procedure")
- Renamed the "simple" authentication mechanism to the - Clarified that anonymous authentication involves a name value of
name/password authentication mechanism to better describe it. zero length and a password value of zero length. The
unauthenticated authentication mechanism was added to handle simple
Bind requests involving a name value with a non-zero length and a
password value of zero length.
- The use of TLS was generalized to align with definitions of LDAP B.2.3. Section 6 ("Password-based authentication")
protocol layers. TLS establishment is now discussed as an
independent subject and is generalized for use with all
authentication mechanisms and other security layers.
- Removed the implication that the userPassword attribute is the - See Section B.2.1.
sole location for storage of password values to be used in
authentication. There is no longer any implied requirement for
how or where passwords are stored at the server for use in
authentication.
B.2.6. Section 6.3 (Other authentication choices with TLS) B.2.4. Section 6.1 ("Digest authentication")
- See section B.2.5.
B.2.7. Section 7.1 (Certificate-based authentication with TLS) - As the SASL-DIGEST-MD5 mechanism is no longer mandatory to
implement, this section is now historical and was not included in
this document. RFC 2829, Section 6.1, continues to document the
SASL DIGEST-MD5 authentication mechanism.
- See section B.2.5. B.2.5. Section 6.2 ("'simple' authentication choice under TLS
encryption")
B.2.8. Section 8 (Other mechanisms) - Renamed the "simple" authentication mechanism to the name/password
authentication mechanism to better describe it.
- All SASL authentication mechanisms are explicitly allowed within - The use of TLS was generalized to align with definitions of LDAP
LDAP. Specifically, this means the SASL ANONYMOUS and SASL PLAIN protocol layers. TLS establishment is now discussed as an
mechanisms are no longer precluded from use within LDAP. independent subject and is generalized for use with all
authentication mechanisms and other security layers.
B.2.9. Section 9 (Authorization identity) - Removed the implication that the userPassword attribute is the sole
location for storage of password values to be used in
authentication. There is no longer any implied requirement for how
or where passwords are stored at the server for use in
authentication.
- Specified matching rules for dnAuthzID and uAuthzID values. In B.2.6. Section 6.3 ("Other authentication choices with TLS")
particular, the DN value in the dnAuthzID form must be matched
using DN matching rules and the uAuthzID value MUST be prepared
using SASLprep rules before being compared octet-wise.
- Clarified that uAuthzID values should not be assumed to be - See Section B.2.5.
globally unique.
B.2.10. Section 10 (TLS Ciphersuites) B.2.7. Section 7.1 ("Certificate-based authentication with TLS")
- TLS Ciphersuite recommendations are no longer included in this - See Section B.2.5.
specification. Implementations must still support the
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite.
- Clarified that anonymous authentication involves a name value of B.2.8. Section 8 ("Other mechanisms")
zero length and a password value of zero length. The
unauthenticated authentication mechanism was added to handle
simple Bind requests involving a name value with a non-zero
length and a password value of zero length.
B.3. Changes Made to RFC 2830: - All SASL authentication mechanisms are explicitly allowed within
LDAP. Specifically, this means the SASL ANONYMOUS and SASL PLAIN
mechanisms are no longer precluded from use within LDAP.
This section summarizes the substantive changes made to sections 3 B.2.9. Section 9 ("Authorization Identity")
and 5 of RFC 2830. Readers should consult [Protocol] for summaries
of changes to other sections.
B.3.1. Section 3.6 (Server Identity Check) - Specified matching rules for dnAuthzId and uAuthzId values. In
- Substantially updated the server identity check algorithm to particular, the DN value in the dnAuthzId form must be matched
ensure that it is complete and robust. In particular, the use using DN matching rules, and the uAuthzId value MUST be prepared
of all relevant values in the subjectAltName and the subjectName using SASLprep rules before being compared octet-wise.
fields are covered by the algorithm and matching rules are
specified for each type of value. Mapped (derived) forms of the
server identity may now be used when the mapping is performed in
a secure fashion.
B.3.2. Section 3.7 (Refresh of Server Capabilities Information) - Clarified that uAuthzId values should not be assumed to be globally
unique.
- Clients are no longer required to always refresh information B.2.10. Section 10 ("TLS Ciphersuites")
about server capabilities following TLS establishment to allow
for situations where this information was obtained through a
secure mechanism.
B.3.3. Section 5.2 (Effects of TLS on Authorization Identity) - TLS ciphersuite recommendations are no longer included in this
specification. Implementations must now support the
TLS_RSA_WITH_3DES_EDE_CBC_SHA ciphersuite and should continue to
support the TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA ciphersuite.
- Establishing a TLS layer on an LDAP session may now cause the - Clarified that anonymous authentication involves a name value of
authorization state of the LDAP session to change. zero length and a password value of zero length. The
unauthenticated authentication mechanism was added to handle simple
Bind requests involving a name value with a non-zero length and a
password value of zero length.
B.3.4. Section 5.1.1 (TLS Closure Effects) B.3. Changes Made to RFC 2830
- Closing a TLS layer on an LDAP session changes the This section summarizes the substantive changes made to Sections 3
authentication and authorization state of the LDAP session based and 5 of RFC 2830. Readers should consult [RFC4511] for summaries of
on local policy. Specifically, this means that implementations changes to other sections.
are not required to to change the authentication and
authorization states to anonymous upon TLS closure.
Appendix C. Changes for draft-ldapbis-authmeth-19 B.3.1. Section 3.6 ("Server Identity Check")
[[Note to RFC Editor: Please remove this appendix upon publication - Substantially updated the server identity check algorithm to ensure
of this Internet-Draft as an RFC.]] that it is complete and robust. In particular, the use of all
relevant values in the subjectAltName and the subjectName fields
are covered by the algorithm and matching rules are specified for
each type of value. Mapped (derived) forms of the server identity
may now be used when the mapping is performed in a secure fashion.
This appendix is non-normative. B.3.2. Section 3.7 ("Refresh of Server Capabilities Information")
This appendix summarizes changes made in this revision of the - Clients are no longer required to always refresh information about
document. server capabilities following TLS establishment. This is to allow
for situations where this information was obtained through a secure
mechanism.
General B.3.3. Section 5 ("Effects of TLS on a Client's Authorization
Identity")
- This draft has addressed all issues raised for the -18 version. - Establishing a TLS layer on an LDAP session may now cause the
authorization state of the LDAP session to change.
- Several minor edits for clarity and to remove typos based on B.3.4. Section 5.2 ("TLS Connection Closure Effects")
feedback from WG, IETF and IESG reviews.
Abstract - Closing a TLS layer on an LDAP session changes the authentication
- Added statement regarding RFCs obsoleted by this document. and authorization state of the LDAP session based on local policy.
Specifically, this means that implementations are not required to
change the authentication and authorization states to anonymous
upon TLS closure.
Section 2 - Replaced references to RFC 2401 with RFC 4301.
- Changed mandatory-to-implement TLS ciphersuite from
TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA to
TLS_RSA_WITH_3DES_EDE_CBC_SHA based on IESG recommendation and
WG consensus.
Section 5.2.1.5 Author's Address
- Clarified that 'supportedSASLMechanisms' should be retrievable
by all clients both before and after SASL negotiation to allow
detection of mechanism downgrade attacks.
Section 5.2.1.6 Roger Harrison
- Changed wording to reflect the fact that SASL layers cannot be Novell, Inc.
uninstalled from the session. 1800 S. Novell Place
Provo, UT 84606
USA
Section 5.2.3 Phone: +1 801 861 2642
- Removed reference to IPsec as a source of authorization identity. EMail: roger_harrison@novell.com
Section 6.2 Full Copyright Statement
- When TLS layer does not provide an acceptable level of security
client MUST warn the user or refuse to proceed. (This was
changed from SHOULD based on IESG recommendation and WG
consensus.)
- Added a security consideration regarding the proper usage of Copyright (C) The Internet Society (2006).
information found in the client certificate.
Section 6.4 This document is subject to the rights, licenses and restrictions
- Added a new section on SASL security considerations that contained in BCP 78, and except as set forth therein, the authors
discusses SASL mechanism downgrade attacks. retain all their rights.
Section 10 This document and the information contained herein are provided on an
- Replaced references to RFC 2401 with RFC 4301. "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET
ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED,
INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE
INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED
WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
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