INTERNET-DRAFT Editor: R. Harrison
-draft-ietf-ldapbis-authmeth-09.txt Novell, Inc.
-Obsoletes: 2251, 2829, 2830 5 December 2003
+draft-ietf-ldapbis-authmeth-10.txt Novell, Inc.
+Obsoletes: 2829, 2830 10 February 2003
Intended Category: Draft Standard
- LDAP: Authentication Methods
+ LDAP: Authentication Methods
and
- Connection Level Security Mechanisms
+ Connection Level Security Mechanisms
Status of this Memo
This document is intended to be, after appropriate review and
revision, submitted to the RFC Editor as a Standard Track document.
Distribution of this memo is unlimited. Technical discussion of
- this document will take place on the IETF LDAP Extension Working
+ this document will take place on the IETF LDAP Revision Working
Group mailing list <ietf-ldapbis@OpenLDAP.org>. Please send
editorial comments directly to the author
<roger_harrison@novell.com>.
security mechanisms of the Lightweight Directory Access Protocol
(LDAP).
- This document details the simple Bind authentication method
+ This document also details establishment of TLS (Transport Layer
+ Security) using the Start TLS operation.
+
+ This document also details the simple Bind authentication method
including anonymous, unauthenticated, and plain-text password
methods and the SASL (Simple Authentication and Security Layer) Bind
- authentication method including the use of DIGEST-MD5 and EXTERNAL
- mechanisms.
-
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- This document also details establishment of TLS (Transport Layer
- Security) using the Start TLS operation.
+ authentication method including the use of DIGEST-MD5 and EXTERNAL
+ mechanisms.
This document describes various authentication and authorization
states through which a connection to an LDAP server may pass and the
actions that trigger these state changes.
+Table of Contents
+
+ 1. Introduction................................................3
+ 1.1. Relationship to Other Documents...........................5
+ 2. Conventions Used in this Document...........................5
+ 2.1. Glossary of Terms.........................................5
+ 2.2. Security Terms and Concepts...............................5
+ 2.3. Keywords..................................................6
+ 3. Start TLS Operation.........................................6
+ 3.1. Sequencing of the Start TLS Operation ....................6
+ 3.1.1. Start TLS Request.......................................6
+ 3.1.2. Start TLS Response......................................7
+ 3.1.3. TLS Version Negotiation.................................7
+ 3.1.4. Discovery of Resultant Security Level...................7
+ 3.1.5. Server Identity Check...................................7
+ 3.1.6. Refresh of Server Capabilities Information..............8
+ 3.2. Effects of TLS on a Client's Authorization Identity.......8
+ 3.2.1. TLS Connection Establishment Effects....................9
+ 3.2.2. Client Assertion of Authorization Identity..............9
+ 3.2.3. TLS Connection Closure Effects..........................9
+ 4. Bind Operation..............................................9
+ 4.1. Simple Authentication.....................................9
+ 4.2. SASL Authentication.......................................9
+ 5. Anonymous LDAP Association on Unbound Connections......... 10
+ 6. Anonymous Authentication ................................. 10
+ 7. Simple Authentication..................................... 10
+ 8. SASL Authentication Profile............................... 11
+ 8.1. SASL Service Name for LDAP.............................. 11
+ 8.2. SASL Authentication Initiation and Protocol Exchange.... 11
+ 8.3. Octet Where Negotiated Security Mechanisms Take Effect.. 12
+ 8.4. Determination of Supported SASL Mechanisms.............. 12
+ 8.5. Rules for Using SASL Security Layers.................... 13
+ 9. SASL EXTERNAL Mechanism................................... 13
+ 9.1. Implicit Assertion...................................... 13
+ 9.2. Explicit Assertion...................................... 14
+ 9.3. SASL Authorization Identity............................. 14
+ 9.4 Authorization Identity Syntax............................ 14
+ 10. SASL DIGEST-MD5 Mechanism................................ 15
+ 11. General Requirements for Password-based Authentication .. 15
+ 12. Invalidated Associations................................. 16
+ 13. TLS Ciphersuites......................................... 16
+
+
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+ 13.1. TLS Ciphersuites Recommendations....................... 17
+ 14. Security Considerations ................................. 18
+ 14.1. Start TLS Security Considerations...................... 18
+ 15. IANA Considerations...................................... 19
+ Acknowledgements............................................. 19
+ Normative References......................................... 19
+ Informative References....................................... 21
+ Author's Address............................................. 21
+ Appendix A. LDAP Association State Transition Tables......... 21
+ A.1. LDAP Association States................................. 21
+ A.2. Actions that Affect LDAP Association State.............. 22
+ A.3. Decisions Used in Making LDAP Association State Changes. 22
+ A.4. LDAP Association State Transition Table................. 22
+ Appendix B. Example Deployment Scenarios..................... 23
+ Appendix C. Authentication and Authorization Concepts........ 24
+ C.1. Access Control Policy................................... 24
+ C.2. Access Control Factors ................................. 24
+ C.3. Authentication, Credentials, Identity .................. 25
+ C.4. Authorization Identity ................................. 25
+ Appendix D. RFC 2829 Change History ......................... 25
+ Appendix E. RFC 2830 Change History ......................... 29
+ Appendix F. RFC 2251 Change History ......................... 30
+ Appendix G. Change History to Combined Document.............. 30
+ Appendix H. Issues to be Resolved............................ 41
+
+
1. Introduction
The Lightweight Directory Access Protocol (LDAP) [Protocol] is a
(1) Unauthorized access to directory data via data-retrieval
operations,
- (2) Unauthorized access to reusable client authentication
+ (2) Unauthorized access to directory data by monitoring others'
+ access,
+
+ (3) Unauthorized access to reusable client authentication
information by monitoring others' access,
+
+ (4) Unauthorized modification of directory data,
- (3) Unauthorized access to directory data by monitoring others'
- access,
- (4) Unauthorized modification of directory data,
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(5) Unauthorized modification of configuration information,
- (6) Unauthorized or excessive use of resources (denial of service),
- and
+ (6) Denial of Service: Use of resources (commonly in excess) in a
+ manner intended to deny service to others. and
- (7) Spoofing of directory: Tricking a 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,
either by modifying data in transit or misdirecting the client's
- connection. Also, tricking a client into sending privileged
+ connection. Tricking a user or client into sending privileged
information to a hostile entity that appears to be the directory
- but is not.
+ server but is not. Tricking a directory server into believing
+ that information came from a particular client when in fact it
+ came from a hostile entity.
+
+ (8) Hijacking of prototocol sessions.
Threats (1), (4), (5) and (6) are due to hostile clients. Threats
(2), (3) and (7) are due to hostile agents on the path between
- client and server or hostile agents posing as a server.
-
- LDAP can be protected with the following security mechanisms:
-
- (1) Client authentication by means of the Secure Authentication and
- Security Layer (SASL) [SASL] mechanism set, possibly backed by
- the Transport Layer Security (TLS) [TLS] credentials exchange
- mechanism,
+ client and server or hostile agents posing as a server, e.g. IP
+ spoofing.
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+ LDAP offers the following security mechanisms:
+ (1) Authentication by means of the Bind operation. The Bind
+ operation provides a simple method which supports anonymous,
+ unauthenticated, and authenticated with password mechanisms, and
+ the Secure Authentication and Security Layer (SASL) method which
+ supports a wide variety of authentication mechanisms and which
+ may be extended to support additional methods of authentication.
(2) Client authorization by means of access control based on the
requestor's authenticated identity,
alternatives is not a strategy that is likely to lead to
interoperability. In the absence of mandates, clients will be
written that do not support any security function supported by the
- server, or worse, they will support only mechanisms like the LDAP
- simple bind using clear text passwords that provide inadequate
- security for most circumstances.
+
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+ server, or worse, they will support only clear text passwords that
+ provide inadequate security for most circumstances.
Given the presence of the Directory, there is a strong desire to see
mechanisms where identities take the form of an LDAP distinguished
carry identities not represented as LDAP DNs that are familiar to
the user or that are used in other systems.
- The set of security mechanisms provided in LDAP and described in
- this document is intended to meet the security needs for a wide
- range of deployment scenarios and still provide a high degree of
- interoperability among various LDAP implementations and
- deployments. Appendix A contains example deployment scenarios that
- list the mechanisms that might be used to achieve a reasonable
- level of security in various circumstances.
+ The set of security mechanisms provided in LDAP and described in
+ this document is intended to meet the security needs for a wide
+ range of deployment scenarios and still provide a high degree of
+ interoperability among various LDAP implementations and deployments.
+ Appendix B contains example deployment scenarios that list the
+ mechanisms that might be used to achieve a reasonable level of
+ security in various circumstances.
1.1. Relationship to Other Documents
This document obsoletes RFC 2829.
-
-
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Sections 2 and 4 of RFC 2830 are obsoleted by [Protocol]. The
remainder of RFC 2830 is obsoleted by this document.
- "connection" and "LDAP connection" both refer to the underlying
transport protocol connection between two protocol peers.
- - "TLS connection" refers to a TLS-protected LDAP connection.
+ - "TLS connection" refers to a TLS-protected [TLS] LDAP
+ connection.
- "association" and "LDAP association" both refer to the
association of the LDAP connection and its current
2.2. Security Terms and Concepts
+
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In general, security terms in this document are used consistently
- with the definitions provided in [RFC2828]. In addition, several
+ with the definitions provided in [Glossary]. In addition, several
terms and concepts relating to security, authentication, and
- authorization are presented in Appendix B of this document. While
+ authorization are presented in Appendix C of this document. While
the formal definition of these terms and concepts is outside the
scope of this document, an understanding of them is prerequisite to
understanding much of the material in this document. Readers who are
unfamiliar with security-related concepts are encouraged to review
- Appendix B before reading the remainder of this document.
+ Appendix C before reading the remainder of this document.
2.3. Keywords
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
- document are to be interpreted as described in RFC 2119 [RFC2119].
+ document are to be interpreted as described in RFC 2119 [Keyword].
+
+3. Start TLS Operation
+
+ The Start Transport Layer Security (Start TLS) operation defined in
+ section 4.13 of [Protocol] provides the ability to establish [TLS]
+ on an LDAP connection.
+
+3.1. Sequencing of the Start TLS Operation
+
+ This section describes the overall procedures clients and servers
+ must follow for TLS establishment. These procedures take into
+ consideration various aspects of the overall security of the LDAP
+ association including discovery of resultant security level and
+ assertion of the client's authorization identity.
+
+ Note that the precise effects, on a client's authorization identity,
+ of establishing TLS on an LDAP connection are described in detail in
+ section 3.2.
+
+3.1.1. Start TLS Request
+
+ A client may send the Start TLS extended request at any time after
+ establishing an LDAP connection, except:
+
+ - when TLS is currently established on the connection,
+ - when a multi-stage SASL negotiation is in progress on the
+ connection, or
+ - when there are outstanding LDAP operations on the connection.
+
+ The result of violating any of these requirements is a resultCode of
+ operationsError, as described in [Protocol] section 4.13.2.2. Client
+ implementers should note that it is possible to receive a resultCode
+ of success for a Start TLS operation that is sent on a connection
+ with outstanding LDAP operations if the server has sufficient time
+ to process them prior to its receiving the Start TLS request.
+ Implementors of clients should ensure that they do not inadvertently
+ depend upon this race condition.
+
+
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+ There is no requirement that the client have or have not already
+ performed a Bind operation (section 4) before sending a Start TLS
+ operation request.
+
+ If the client did not establish a TLS connection before sending some
+ other request, and the server requires the client to establish a TLS
+ connection before performing that request, the server MUST reject
+ that request by sending a resultCode of confidentialityRequired or
+ strongAuthRequired.
+
+ An LDAP server which requests that clients provide their certificate
+ during TLS negotiation MAY use a local security policy to determine
+ whether to successfully complete TLS negotiation if the client did
+ not present a certificate which could be validated.
+
+3.1.2. Start TLS Response
+
+ The server will return an extended response with the resultCode of
+ success if it is willing and able to negotiate TLS. It will return
+ other resultCode values (documented in [Protocol] section 4.13.2.2)
+ if it is unwilling or unable to do so.
+
+ In the successful case, the client (which has ceased to transfer
+ LDAP requests on the connection) MUST either begin a TLS negotiation
+ or close the connection. The client will send PDUs in the TLS Record
+ Protocol directly over the underlying transport connection to the
+ server to initiate [TLS] negotiation.
+
+3.1.3. TLS Version Negotiation
+
+ Negotiating the version of TLS to be used is a part of the TLS
+ Handshake Protocol [TLS]. Please refer to that document for details.
+
+3.1.4. Discovery of Resultant Security Level
+
+ After a TLS connection is established on an LDAP connection, both
+ parties must individually decide whether or not to continue based on
+ the security level achieved. Ascertaining the TLS connection's
+ security level is implementation dependent and accomplished by
+ communicating with one's respective local TLS implementation.
+
+ If the client or server decides that the level of authentication or
+ security is not high enough for it to continue, it SHOULD gracefully
+ close the TLS connection immediately after the TLS negotiation has
+ completed (see [Protocol] section 4.13.3.1 and section 3.2.3 below).
+ If the client decides to continue, it may gracefully close the TLS
+ connection and attempt to Start TLS again, it may send an unbind
+ request, or it may send any other LDAP request.
+
+3.1.5. Server Identity Check
+
+ The client MUST check its understanding of the server's hostname
+ against the server's identity as presented in the server's
+ Certificate message in order to prevent man-in-the-middle attacks.
+
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+
+ Matching is performed according to these rules:
+
+ - The client MUST use the server provided by the user (or other
+ trusted entity) as the value to compare against the server name
+ as expressed in the server's certificate. A hostname derived
+ from the user input is to be considered provided by the user
+ only if derived in a secure fashion (e.g., DNSSEC).
+
+ - If a subjectAltName extension of type dNSName is present in the
+ certificate, it SHOULD be used as the source of the server's
+ identity.
+
+ - Matching is case-insensitive.
+
+ - The "*" wildcard character is allowed. If present, it applies
+ only to the left-most name component.
+
+ For example, *.bar.com would match a.bar.com and b.bar.com, but
+ it would not match a.x.bar.com nor would it match bar.com. If
+ more than one identity of a given type is present in the
+ certificate (e.g. more than one dNSName name), a match in any
+ one of the set is considered acceptable.
+
+ If the hostname does not match the dNSName-based identity in the
+ certificate per the above check, user-oriented clients SHOULD either
+ notify the user (clients may give the user the opportunity to
+ continue with the connection in any case) or terminate the
+ connection and indicate that the server's identity is suspect.
+ Automated clients SHOULD close the connection, returning and/or
+ logging an error indicating that the server's identity is suspect.
+
+ Beyond the server identity checks described in this section, clients
+ SHOULD be prepared to do further checking to ensure that the server
+ is authorized to provide the service it is observed to provide. The
+ client may need to make use of local policy information in making
+ this determination.
+
+3.1.6. Refresh of Server Capabilities Information
+
+ Upon TLS session establishment, the client SHOULD discard or refresh
+ all information about the server it obtained prior to the initiation
+ of the TLS negotiation and not obtained through secure mechanisms.
+ This protects against active-intermediary attacks that may have
+ altered any server capabilities information retrieved prior to TLS
+ establishment.
+
+ The server may advertise different capabilities after TLS
+ establishment. In particular, the value of supportedSASLMechanisms
+ may be different after TLS has been negotiated (specifically, the
+ EXTERNAL and PLAIN [PLAIN] mechanisms are likely to be listed only
+ after a TLS negotiation has been performed).
+
+3.2. Effects of TLS on a Client's Authorization Identity
+
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+
+ This section describes the effects on a client's authorization
+ identity brought about by establishing TLS on an LDAP connection.
+ The default effects are described first, and next the facilities for
+ client assertion of authorization identity are discussed including
+ error conditions. Finally, the effects of closing the TLS connection
+ are described.
+
+ Authorization identities and related concepts are described in
+ Appendix C.
+
+3.2.1. TLS Connection Establishment Effects
+
+ The decision to keep or invalidate the established authentication
+ and authorization identities in place after TLS closure is a matter
+ of local server policy.
+
+3.2.2. Client Assertion of Authorization Identity
+
+ After successfully establishing a TLS session, a client may request
+ that its credentials exchanged during the TLS establishment be
+ utilized to authenticate the LDAP association and thus determine the
+ client's authorization status. The client accomplishes this via an
+ LDAP Bind request specifying a SASL mechanism of EXTERNAL [SASL]
+ (section 9). LDAP server implementations SHOULD support this
+ authentication method.
+
+3.2.3. TLS Connection Closure Effects
+
+ The decision to keep or invalidate the established authentication
+ and authorization identities in place after TLS closure is a matter
+ of local server policy.
-3. Bind Operation
+4. Bind Operation
The Bind operation defined in section 4.2 of [Protocol] allows
authentication information to be exchanged between the client and
- server to establish a new LDAP association. The new LDAP association
- is established upon successful completion of the authentication
- exchange.
+ server to establish a new LDAP association.
-3.1. Implied Anonymous Bind on LDAP Association
+ Upon receipt of a Bind request, the LDAP association is moved to an
+ anonymous state and only upon successful completion of the
+ authentication exchange (and the Bind operation) is the association
+ moved to an authenticated state.
+
+4.1. Simple Authentication
+
+ The simple authentication choice of the Bind Operation provides
+ minimal facilities for establishing an anonymous association
+ (section 6) or for establishing an LDAP association based upon
+ credentials consisting of a name (in the form of an LDAP
+ distinguished name [LDAPDN]) and a password (section 7).
+
+4.2. SASL Authentication
- Prior to the successful completion of a Bind operation and during
- any subsequent authentication exchange, the session has an anonymous
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+ The sasl authentication choice of the Bind Operation provides
+ facilities for authenticating via SASL mechanisms (sections 8-10).
+
+5. Anonymous LDAP Association on Unbound Connections
+
+ Prior to the successful completion of a Bind operation and during
+ any subsequent authentication exchange, the session has an anonymous
LDAP association. Among other things this implies that the client
need not send a Bind Request in the first PDU of the connection. The
client may send any operation request prior to binding, and the
bind operation. This authentication state on an LDAP association is
sometimes referred to as an implied anonymous bind.
-3.2. Simple Authentication
+6. Anonymous Authentication
+
+ Directory operations that modify entries or access protected
+ attributes or entries generally require client authentication.
+ Clients that do not intend to perform any of these operations
+ typically use anonymous authentication.
+
+ An LDAP client may explicitly establish an anonymous association by
+ sending a Bind Request with the simple authentication choice
+ containing a value--construed as the password--of zero length. A
+ bind request where both the name and password are of zero length is
+ said to be an anonymous bind. A bind request where the name, a DN,
+ is of non-zero length, and the password is of zero length is said to
+ be an unauthenticated bind. Both variations produce an anonymous
+ association.
+
+ Unauthenticated binds can have significant security issues (see
+ section 14). Servers SHOULD by default reject unauthenticated bind
+ requests with a resultCode of invalidCredentials, and clients may
+ need to actively detect situations where they would make an
+ unauthenticated bind request.
+
+ An LDAP server may use other information about the client provided
+ by the lower layers or external means to grant or deny access even
+ to anonymously authenticated clients.
+
+ LDAP implementations MUST support anonymous authentication.
+
+7. Simple Authentication
+
+ An LDAP client may establish an LDAP association by sending a Bind
+ Request with a name value consisting of an LDAP distinguished name
+ [LDAPDN] and specifying the simple authentication choice with a
+ password value.
- The simple authentication choice provides minimal facilities for
- establishing an anonymous association or for establishing an LDAP
- association based upon credentials consisting of a name (in the form
- of an [LDAPDN] and a password.
+ DSAs that map the DN sent in the bind request to a directory entry
+ with an associated set of one or more passwords will compare the
+ presented password to the set of passwords associated with that
+ entry. If the presented password matches any member of that set,
+
- The simple authentication choice provides two different methods
- for establishing an anonymous association: anonymous bind and
- unauthenticated bind (see section 5.1).
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- The simple authentication choice provides one method for
- establishing a non-anonymous association: simple password bind.
+ then the server will respond with a success resultCode, otherwise
+ the server will respond with an invalidCredentials resultCode.
-3.3. SASL Authentication Profile
+ The simple authentication choice is not suitable for authentication
+ in environments where there is no network or transport layer
+ confidentiality. LDAP implementations SHOULD support authentication
+ with the "simple" authentication choice when the connection is
+ protected against eavesdropping using TLS, as defined in section 4.
+ LDAP implementations SHOULD NOT support authentication with the
+ "simple" authentication choice unless the data on the connection is
+ protected using TLS or other data confidentiality and data integrity
+ protection.
+
+8. SASL Authentication Profile
LDAP allows authentication via any SASL mechanism [SASL]. As LDAP
includes native anonymous and plaintext authentication methods, the
protocol ([SASL] section 5). This section explains how each of these
profiling requirements are met by LDAP.
-3.3.1. SASL Service Name for LDAP
+8.1. SASL Service Name for LDAP
The SASL service name for LDAP is "ldap", which has been registered
with the IANA as a GSSAPI service name.
-3.3.2. SASL authentication initiation and protocol exchange
+8.2. SASL Authentication Initiation and Protocol Exchange
SASL authentication is initiated via an LDAP bind request
([Protocol] section 4.2) with the following parameters:
In general, a SASL authentication protocol exchange consists of a
series of server challenges and client responses, the contents of
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which are specific to and defined by the SASL mechanism. Thus for
some SASL authentication mechanisms, it may be necessary for the
client to respond to one or more server challenges by invoking the
BindRequest multiple times. A challenge is indicated by the server
sending a BindResponse with the resultCode set to
saslBindInProgress. This indicates that the server requires the
- client to send a new bind request, with the same sasl mechanism to
+ client to send a new bind request with the same sasl mechanism to
continue the authentication process.
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To the encapsulating protocol, these challenges and responses are
opaque binary tokens of arbitrary length. LDAP servers use the
mechanisms which are defined to have the server send additional data
along with the indication of successful completion.
-3.3.3. Octet where negotiated security mechanisms take effect
+8.3. Octet Where Negotiated Security Mechanisms Take Effect
- When negotiated, SASL security layers take effect following the
- transmission by the server and reception by the client of the final
+ SASL security layers take effect following the transmission by the
+ server and reception by the client of the final successful
BindResponse in the exchange.
Once a SASL security layer providing integrity or confidentiality
is installed (i.e. at the first octet following the final
BindResponse of the bind operation that caused the new layer to take
effect).
+
+8.4. Determination of Supported SASL Mechanisms
+
+ Clients may determine the SASL mechanisms a server supports by
+ reading the 'supportedSASLMechanisms ' attribute from the root DSE
+ (DSA-Specific Entry) ([Models] section 5.1). The values of this
+ attribute, if any, list the mechanisms the server supports in the
+ current LDAP session state.
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-3.3.4. Determination of supported SASL mechanisms
-
- An LDAP client may determine the SASL mechanisms a server supports
- by performing a search request on the root DSE, requesting the
- supportedSASLMechanisms attribute. The values of this attribute, if
- any, list the mechanisms the server supports.
-3.3.5. Rules for using SASL security layers
+ LDAP servers SHOULD allow an anonymously-bound client to retrieve
+ the supportedSASLMechanisms attribute of the root DSE.
+
+8.5. Rules for Using SASL Security Layers
If a SASL security layer is negotiated, the client SHOULD discard
information about the server it obtained prior to the initiation of
and servers should allow the user to specify what mechanisms are
acceptable and allow only those mechanisms to be used.
-3.3.6. Use of EXTERNAL SASL Mechanism
+9. SASL EXTERNAL Mechanism
A client can use the EXTERNAL SASL [SASL] mechanism to request the
LDAP server to make use of security credentials exchanged by a lower
security layer (such as by TLS authentication or IP-level security
- [RFC2401]).
+ [SecArch]).
If the client's authentication credentials have not been established
at a lower security layer, the SASL EXTERNAL bind MUST fail with a
with its authenticated TLS credentials. The former is known as an
implicit assertion, and the latter as an explicit assertion.
-3.3.6.1. Implicit Assertion
+9.1. Implicit Assertion
An implicit authorization identity assertion is performed by
invoking a Bind request of the SASL form using the EXTERNAL
- mechanism name that SHALL NOT include the optional credentials octet
+ mechanism name that does not include the optional credentials octet
string (found within the SaslCredentials sequence in the Bind
Request). The server will derive the client's authorization identity
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from the authentication identity supplied by the security layer
(e.g., a public key certificate used during TLS establishment)
according to local policy. The underlying mechanics of how this is
accomplished are implementation specific.
+
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-3.3.6.2. Explicit Assertion
+9.2. Explicit Assertion
An explicit authorization identity assertion is performed by
invoking a Bind request of the SASL form using the EXTERNAL
- mechanism name that SHALL include the credentials octet string. This
+ mechanism name that includes the credentials octet string. This
string MUST be constructed as documented in section 3.4.1.
- The server MUST that the client's authentication identity as
+ The server MUST verify that the client's authentication identity as
supplied in its TLS credentials is permitted to be mapped to the
asserted authorization identity. The server MUST reject the Bind
operation with an invalidCredentials resultCode in the Bind response
if the client is not so authorized.
-3.3.6.3. SASL Authorization Identity
+9.3. SASL Authorization Identity
When the EXTERNAL SASL mechanism is being negotiated, if the
SaslCredentials credentials field is present, it contains an
authorization identity is represented in the authzId form described
below.
-3.3.6.4 Authorization Identity Syntax
+9.4 Authorization Identity Syntax
The authorization identity is a string of [UTF-8] encoded [Unicode]
characters corresponding to the following [ABNF] grammar:
The dnAuthzId choice allows clients to assert authorization
identities in the form of a distinguished name to be matched in
+ accordance with the distinguishedNameMatch matching rule [Syntaxes].
+ The decision to allow or disallow an authentication identity to have
+ access to the requested authorization identity is a matter of local
+
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- accordance with the distinguishedName matching rule [Syntaxes]. The
- decision to allow or disallow an authentication identity to have
- access to the requested authorization identity is a matter of local
policy ([SASL] section 4.2). For this reason there is no requirement
that the asserted dn be that of an entry in directory.
to assert an authorization identity to a local directory but do not
have that identity in distinguished name form. The value contained
within a uAuthzId MUST be prepared using [SASLPrep] before being
- compared octet-wise. The format of utf8string is defined as only a
+ compared octet-wise. The format of userid is defined as only a
sequence of [UTF-8] encoded [Unicode] characters, and further
interpretation is subject to prior agreement between the client and
server.
email address. A uAuthzId SHOULD NOT be assumed to be globally
unique.
-4. Start TLS Operation
+10. SASL DIGEST-MD5 Mechanism
- The Start Transport Layer Security (Start TLS) operation defined in
- section 4.13 of [Protocol] provides the ability to establish [TLS]
- on an LDAP association.
-
-4.1. Sequencing of the Start TLS Operation
-
- This section describes the overall procedures clients and servers
- must follow for TLS establishment. These procedures take into
- consideration various aspects of the overall security of the LDAP
- association including discovery of resultant security level and
- assertion of the client's authorization identity.
-
- Note that the precise effects, on a client's authorization identity,
- of establishing TLS on an LDAP association are described in detail
- in section 4.2.
-
-4.1.1. Start TLS Request
-
- The client MAY send the Start TLS extended request at any time after
- establishing an LDAP connection, except:
-
- - when TLS is currently established on the connection,
- - when a multi-stage SASL negotiation is in progress on the
- connection, or
- - when there are one or more outstanding LDAP operations on the
- connection.
-
- The result of violating any of these requirements is a resultCode of
- operationsError, as described in [Protocol] section 4.13.2.2. Client
- implementers should note that it is possible to receive a resultCode
- of success for a Start TLS operation that is sent on a connection
- with outstanding LDAP operations and the server has sufficient time
-
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-
- to process them prior to its receiving the Start TLS request.
- Implementors of clients should ensure that they do not inadvertently
- depend upon this race condition.
-
- In particular, there is no requirement that the client have or have
- not already performed a Bind operation before sending a Start TLS
- operation request. The client may have already performed a Bind
- operation when it sends a Start TLS request, or the client might
- have not yet bound.
-
- If the client did not establish a TLS connection before sending any
- other requests, and the server requires the client to establish a
- TLS connection before performing a particular request, the server
- MUST reject that request by sending a resultCode of
- confidentialityRequired or strongAuthRequired.
-
-4.1.2. Start TLS Response
-
- The server will return an extended response with the resultCode of
- success if it is willing and able to negotiate TLS. It will return
- other resultCode values (documented in [Protocol] section 4.13.2.2)
- if it is unwilling or unable to do so.
-
- In the successful case, the client (which has ceased to transfer
- LDAP requests on the connection) MUST either begin a TLS negotiation
- or close the connection. The client will send PDUs in the TLS Record
- Protocol directly over the underlying transport connection to the
- server to initiate [TLS] negotiation.
-
-4.1.3. TLS Version Negotiation
-
- Negotiating the version of TLS or SSL to be used is a part of the
- [TLS] Handshake Protocol. Please refer to that document for details.
-
-4.1.4. Discovery of Resultant Security Level
-
- After a TLS connection is established on an LDAP association, both
- parties must individually decide whether or not to continue based on
- the security level achieved. Ascertaining the TLS connection's
- security level is implementation dependent and accomplished by
- communicating with one's respective local TLS implementation.
-
- If the client or server decides that the level of authentication or
- security is not high enough for it to continue, it SHOULD gracefully
- close the TLS connection immediately after the TLS negotiation has
- completed (see [Protocol] section 4.13.3.1 and section 4.2.3 below).
- If the client decides to continue, it may gracefully close the TLS
- connection and attempt to Start TLS again, it may send an unbind
- request, or it may send any other LDAP request.
-
-4.1.5. Server Identity Check
-
-
-
-
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-
- The client MUST check its understanding of the server's hostname
- against the server's identity as presented in the server's
- Certificate message in order to prevent man-in-the-middle attacks.
-
- Matching is performed according to these rules:
-
- - The client MUST use the server provided by the user (or other
- trusted entity) as the value to compare against the server name
- as expressed in the server's certificate. A hostname derived
- from the user input is to be considered provided by the user
- only if derived in a secure fashion (e.g., DNSSEC).
-
- - If a subjectAltName extension of type dNSName is present in the
- certificate, it SHOULD be used as the source of the server's
- identity.
-
- - Matching is case-insensitive.
-
- - The "*" wildcard character is allowed. If present, it applies
- only to the left-most name component.
-
- For example, *.bar.com would match a.bar.com and b.bar.com, but
- it would not match a.x.bar.com nor would it match bar.com. If
- more than one identity of a given type is present in the
- certificate (e.g. more than one dNSName name), a match in any
- one of the set is considered acceptable.
-
- If the hostname does not match the dNSName-based identity in the
- certificate per the above check, user-oriented clients SHOULD either
- notify the user (clients may give the user the opportunity to
- continue with the connection in any case) or terminate the
- connection and indicate that the server's identity is suspect.
- Automated clients SHOULD close the connection, returning and/or
- logging an error indicating that the server's identity is suspect.
-
- Beyond the server identity checks described in this section, clients
- SHOULD be prepared to do further checking to ensure that the server
- is authorized to provide the service it is observed to provide. The
- client may need to make use of local policy information in making
- this determination.
-
-4.1.6. Refresh of Server Capabilities Information
-
- Upon TLS session establishment, the client SHOULD discard or refresh
- all information about the server it obtained prior to the initiation
- of the TLS negotiation and not obtained through secure mechanisms.
- This protects against active-intermediary attacks that may have
- altered any server capabilities information retrieved prior to TLS
- establishment.
-
- The server may advertise different capabilities after TLS
- establishment. In particular, the value of supportedSASLMechanisms
- may be different after TLS has been negotiated (specifically, the
-
-
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- EXTERNAL and PLAIN [PLAIN] mechanisms are likely to be listed only
- after a TLS negotiation has been performed).
-
-4.2. Effects of TLS on a Client's Authorization Identity
-
- This section describes the effects on a client's authorization
- identity brought about by establishing TLS on an LDAP association.
- The default effects are described first, and next the facilities for
- client assertion of authorization identity are discussed including
- error conditions. Finally, the effects of closing the TLS connection
- are described.
-
- Authorization identities and related concepts are described in
- Appendix B.
-
-4.2.1. TLS Connection Establishment Effects
-
- The decision to keep or invalidate the established authentication
- and authorization identities in place after TLS is negotiated is a
- matter of local server policy. If a server chooses to invalidate
- established authentication and authorization identities after TLS is
- negotiated, it MUST reply to subsequent valid operation requests
- until the next TLS closure or successful bind request with a
- resultCode of strongAuthRequired to indicate that the client needs
- to bind to reestablish its authentication. If the client attempts to
- bind using a method the server is unwilling to support, it responds
- to the with a resultCode of authMethodNotSupported (per [Protocol])
- to indicate that a different authentication method should be used.
-
-4.2.2. Client Assertion of Authorization Identity
+ LDAP servers that implement any authentication method or mechanism
+ other than simple anonymous bind MUST implement the SASL
+ DIGEST-MD5 mechanism [DIGEST-MD5]. This provides client
+ authentication with protection against passive eavesdropping attacks
+ but does not provide protection against active intermediary attacks.
+ DIGEST-MD5 also provides data integrity and data confidentiality
+ capabilities.
- After successfully establishing a TLS session, a client may request
- that its credentials exchanged during the TLS establishment be
- utilized to determine the client's authorization status. The client
- accomplishes this via an LDAP Bind request specifying a SASL
- mechanism of EXTERNAL [SASL]. See section 3.3.6 for additional
- details.
-4.2.3. TLS Connection Closure Effects
+ Support for subsequent authentication ([DIGEST-MD5] section 2.2) is
+ OPTIONAL in clients and servers.
- The decision to keep or invalidate the established authentication
- and authorization identities in place after TLS closure is a matter
- of local server policy. If a server chooses to invalidate
- established authentication and authorization identities after TLS is
- negotiated, it MUST reply to subsequent valid operation requests
- until the next TLS closure or successful bind request with a
- resultCode of strongAuthRequired to indicate that the client needs
- to bind to reestablish its authentication. If the client attempts to
- bind using a method the server is unwilling to support, it responds
- to the with a resultCode of authMethodNotSupported (per [Protocol])
- to indicate that a different authentication method should be used.
-
-5. Anonymous Authentication
-
-
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-
- Directory operations that modify entries or access protected
- attributes or entries generally require client authentication.
- Clients that do not intend to perform any of these operations
- typically use anonymous authentication.
-
- LDAP implementations MUST support anonymous authentication, as
- defined in section 5.1.
-
- LDAP implementations MAY support anonymous authentication with TLS,
- as defined in section 5.2.
-
- While there may be access control restrictions to prevent access to
- directory entries, an LDAP server SHOULD allow an anonymously-bound
- client to retrieve the supportedSASLMechanisms attribute of the root
- DSE.
-
- An LDAP server may use other information about the client provided
- by the lower layers or external means to grant or deny access even
- to anonymously authenticated clients.
-
-5.1. Anonymous Authentication Procedure
-
- Prior to successfully completing a Bind operation, the LDAP
- association is anonymous. See section 3.1.
+ Implementers must take care to ensure that they maintain the
+ semantics of the DIGEST-MD5 specification even when handling data
+ that has different semantics in the LDAP protocol.
+ For example, the SASL DIGEST-MD5 authentication mechanism utilizes
+ realm and username values ([DIGEST-MD5] section 2.1) which are
+ syntactically simple strings and semantically simple realm and
+ username values. These values are not LDAP DNs, and there is no
+ requirement that they be represented or treated as such. Username
+ and realm values that look like LDAP DNs in form, e.g. <cn=bob,
+ dc=example,dc=com>, are syntactically allowed, however DIGEST-MD5
+ treats them as simple strings for comparison purposes. To illustrate
+ further, the two DNs <cn=Bob,dc=example,dc=com> (upper case "B") and
+ <cn=bob,dc=example,dc=com> (lower case "b") are equivalent when
+ being compared semantically as LDAP DNs because the cn attribute is
+ defined to be case insensitive, however the two values are not
+ equivalent if they represent username values in DIGEST-MD5 because
+ [SASLPrep] semantics are used by DIGEST-MD5.
- An LDAP client may also explicitly establish an anonymous
- association by sending a Bind Request with the simple authentication
- option and a password of zero length. A bind request where both the
- name and password are of zero length is said to be an anonymous
- bind. A bind request where the name, a DN, is of non-zero length,
- and the password is of zero length is said to be an unauthenticated
- bind. Both variations produce an anonymous association.
+11. General Requirements for Password-based Authentication
- Unauthenticated binds can have significant security issues (see
- section 10). Servers SHOULD by default reject unauthenticated bind
- requests with a resultCode of invalidCredentials, and clients may
- need to actively detect situations where they would make an
- unauthenticated bind request.
-
-5.2. Anonymous Authentication and TLS
-
- An LDAP client may use the Start TLS operation (section 5) to
- negotiate the use of [TLS] security. If the client has not bound
- beforehand, then until the client uses the EXTERNAL SASL mechanism
- to negotiate the recognition of the client's certificate, the client
- is anonymously authenticated.
-
- Recommendations on TLS ciphersuites are given in section 9.
-
- An LDAP server which requests that clients provide their certificate
- during TLS negotiation MAY use a local security policy to determine
- whether to successfully complete TLS negotiation if the client did
- not present a certificate which could be validated.
-
+ The transmission of passwords in the clear--typically for
+ authentication or modification--poses a significant security risk.
+ This risk can be avoided by using SASL authentication [SASL]
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-6. Password-based Authentication
-
- This section discusses various options for performing password-based
- authentication to LDAP compliant servers and the environments
- suitable for their use.
-
- The transmission of passwords in the clear--typically for
- authentication or modification--poses a significant security risk.
- This risk can be avoided by using SASL bind [SASL] mechanisms that
- do not transmit passwords in the clear and by negotiating transport
- or session layer confidentiality services before transmitting
- password values.
+ mechanisms that do not transmit passwords in the clear or by
+ negotiating transport or session layer confidentiality services
+ before transmitting password values.
To mitigate the security risks associated with the use of passwords,
a server implementation MUST implement a configuration that at the
including a userPassword value, etc.), even if the password
value is correct.
-6.1. Simple Authentication
-
- The LDAP "simple" authentication choice is not suitable for
- authentication in environments where there is no network or
- transport layer confidentiality. LDAP implementations SHOULD support
- authentication with the "simple" authentication choice when the
- connection is protected against eavesdropping using TLS, as defined
- in section 4. LDAP implementations SHOULD NOT support authentication
- with the "simple" authentication choice unless the data on the
- connection is protected using TLS or other data confidentiality and
- data integrity protection.
-
-6.2. Digest Authentication
-
- LDAP servers that implement any authentication method or mechanism
- (other than simple anonymous bind) MUST implement the SASL
- DIGEST-MD5 mechanism [DIGEST-MD5]. This provides client
- authentication with protection against passive eavesdropping
- attacks, but does not provide protection against active intermediary
- attacks. DIGEST-MD5 also provides data integrity and data
- confidentiality capabilities.
-
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-
-
- Support for subsequent authentication is OPTIONAL in clients and
- servers.
-
- Implementors must take care to ensure that they maintain the
- semantics of the DIGEST-MD5 specification even when handling data
- that has different semantics in the LDAP protocol.
- For example, the SASL DIGEST-MD5 authentication mechanism utilizes
- realm and username values ([DigestAuth section 2.1) which are
- syntactically simple strings and semsantically simple realm and
- username values. These values are not LDAP DNs, and there is no
- requirement that they be represented or treated as such. Username
- and realm values that look like LDAP DNs in form, e.g. <cn=bob,
- dc=example,dc=com>, are syntactically allowed, however DIGEST-MD5
- treats them as simple strings for comparison purposes. To illustrate
- further, the two DNs <cn=Bob,dc=example,dc=com> (upper case "B") and
- <cn=bob,dc=example,dc=com> (lower case "b") are equivalent when
- being compared semantically as LDAP DNs because the cn attribute is
- defined to be case insensitive, however the two values are not
- equivalent if they represent username values in DIGEST-MD5 because
- [SASLPrep] semantics are used by DIGEST-MD5.
-
-6.3. simple authentication choice under TLS encryption
-
- Following the negotiation of an appropriate TLS ciphersuite
- providing connection confidentiality, a client MAY authenticate to a
- directory that supports the simple authentication choice by
- performing a simple bind operation
-
- Simple authentication with TLS encryption protection is performed as
- follows:
-
- 1. The client will use the Start TLS operation [Protocol] to
- negotiate the use of TLS security [TLS] on the connection to
- the LDAP server. The client need not have bound to the
- directory beforehand.
-
- For the subsequent authentication procedure to be performed
- securely, the client and server MUST negotiate a ciphersuite
- which contains a bulk encryption algorithm of appropriate
- strength. Recommendations on cipher suites are given in
- section 9.
-
- 2. Following the successful completion of TLS negotiation, the
- client MUST send an LDAP bind request with the version number
- of 3, the name field containing a DN, and the simple
- authentication choice, containing a password.
-
-6.3.1. simple Authentication Choice
-
- DSAs that map the DN sent in the bind request to a directory entry
- with an associated set of one or more passwords will compare the
- presented password to the set of passwords associated with that
- entry. If the presented password matches any member of that set,
-
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-
- then the server will respond with a success resultCode, otherwise
- the server will respond with an invalidCredentials resultCode.
-
-6.4. Other authentication choices with TLS
-
- It is also possible, following the negotiation of TLS, to perform a
- SASL authentication that does not involve the exchange of plaintext
- reusable passwords. In this case the client and server need not
- negotiate a ciphersuite that provides confidentiality if the only
- service required is data integrity.
-
-7. Certificate-based authentication
-
- LDAP server implementations SHOULD support authentication via a
- client certificate in TLS, as defined in section 7.1.
-
-7.1. Certificate-based authentication with TLS
-
- A user who has a public/private key pair in which the public key has
- been signed by a Certification Authority may use this key pair to
- authenticate to the directory server if the user's certificate is
- requested by the server. The user's certificate subject field SHOULD
- be the name of the user's directory entry, and the Certification
- Authority that issued the user's certificate must be sufficiently
- trusted by the directory server in order for the server to process
- the certificate. The means by which servers validate certificate
- paths is outside the scope of this document.
-
- A server MAY support mappings for certificates in which the subject
- field name is different from the name of the user's directory entry.
- A server which supports mappings of names MUST be capable of being
- configured to support certificates for which no mapping is required.
-
- The client will use the Start TLS operation [Protocol] to negotiate
- the use of TLS security [TLS] on the connection to the LDAP server.
- The client need not have bound to the directory beforehand.
-
- In the TLS negotiation, the server MUST request a certificate. The
- client will provide its certificate to the server, and the server
- MUST perform a private key-based encryption, proving it has the
- private key associated with the certificate.
-
- In deployments that require protection of sensitive data in transit,
- the client and server MUST negotiate a ciphersuite that contains a
- bulk encryption algorithm of appropriate strength. Recommendations
- of cipher suites are given in section 9.
-
- The server MUST verify that the client's certificate is valid. The
- server will normally check that the certificate is issued by a known
- certification authority (CA), and that none of the certificates on
- the client's certificate chain are invalid or revoked. There are
- several procedures by which the server can perform these checks.
+12. Invalidated Associations
-
-
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-
- Following the successful completion of TLS negotiation, the client
- will send an LDAP bind request with the SASL EXTERNAL mechanism.
-
-8. LDAP Association State Transition Tables
-
- To comprehensively diagram the various authentication and TLS states
- through hich an LDAP association may pass, this section provides a
- state transition table to represent a state diagram for the various
- states through which an LDAP association may pass during the course
- of its existence and the actions that cause these changes in state.
-
-8.1. LDAP Association States
-
- The following table lists the valid LDAP association states and
- provides a description of each state. The ID for each state is used
- in the state transition table in section 8.4.
-
- ID State Description
- -- --------------------------------------------------------------
- S1 Anonymous
- no Authentication ID is associated with the LDAP connection
- no Authorization ID is in force
- S2 Authenticated
- Authentication ID = I
- Authorization ID = X
- S3 Authenticated SASL EXTERNAL, implicit authorization ID
- Authentication ID = J
- Authorization ID = Y
- S4 Authenticated SASL EXTERNAL, explicit authorization ID
- Authentication ID = J
- Authorization ID = Z
-
-8.2. Actions that Affect LDAP Association State
-
- The following table lists the actions that can affect the
- authentication and authorization state of an LDAP association. The
- ID for each action is used in the state transition table in section
- 8.4.
-
- ID Action
- -- --------------------------------------------------------------
- A1 Client bind request fails
- A2 Client successfully performs anonymous simple bind
- A3 Client successfully performs unauthenticated simple bind
- A4 Client successfully performs simple bind with name and
- password OR SASL bind with any mechanism except EXTERNAL using
- an authentication ID = I that maps to authorization ID X
- A5 Client Binds SASL EXTERNAL with implicit assertion of
- authorization ID (section 3.3.6.1)]. The current
- authentication ID maps to authorization ID = Y.
- A6 Client Binds SASL EXTERNAL with explicit assertion of
- authorization ID = Z (section 3.3.6.2)]
-
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- A7 Client abandons a bind operation, and server processes the
- abandon
- A8 Client abandons a bind operation, and server does not process
- the abandon
- A9 Client Start TLS request fails
- A10 Client Start TLS request succeeds
- A11 Client or Server: graceful TLS closure ([Protocol] section
- 4.13.3.1.)
-
-8.3. Decisions Used in Making LDAP Association State Changes
-
- Certain changes in the authentication and authorization state of an
- LDAP association are only allowed if the server can affirmatively
- answer a question. These questions are applied as part of the
- criteria for allowing or disallowing a state transition in the state
- transition table in section 8.4.
-
- ID Decision Question
- -- --------------------------------------------------------------
- D1 Are lower-layer credentials available?
- D2 Can lower-layer credentials for Auth ID "K" be mapped asserted
- AuthZID "L"?
-
-8.4. LDAP Association State Transition Table
-
- The LDAP Association table below lists the valid authentication and
- authorization states for an LDAP association and the actions that
- could affect them. For any given row in the table, the Current State
- column gives the state of an LDAP association, the Action column
- gives an action that could affect the state of an LDAP assocation,
- and the Next State column gives the resulting state of an LDAP
- association after the action occurs.
-
- S1, the initial state for the state machine described in this table,
- is the authentication state when an LDAP connection is initially
- established.
-
- Current Next
- State Action State Comment
- ------- ------- ----- ---------------------------------------
- Any A1 S1 [Protocol] section 4.2.1
- Any A2 S1 Section 6
- Any A3 S1 Section 6
- Any A4 S2 Sections 6.1, 6.2
- Any A5, S1 Failed bind, section 3.3.6
- D1=no
- Any A5, S3
- D1=yes
- Any A6, S1 failed bind, section 3.3.6
- D1=no
- Any A6, S1 failed bind, section 3.3.6.2
- D1=yes,
- D2=no
-
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- Any A6, S4
- D1=yes,
- D2=yes
- Any A7 S1 [Protocol] section 4.2.1. Clients
- cannot detect this state.
- Any A8 no [Protocol] section 4.2.1. Clients
- change cannot detect this state.
- Any A9 no [Protocol] section 4.13.2.2
- change
- Any A10 no Section 4.2.1
- change
- Any A11 S1 Section 4.2.3
+ The server may, at any time, invalidate the association, e.g. if the
+ established security association between the client and server has
+ unexpectedly failed or been compromised. The association remains
+ invalidated until the next successful bind request. While the
+ association is invalidated, the server may reject any operation
+ request other than Bind, Unbind, and Start TLS by responding with a
+ resultCode of strongAuthRequired to indicate that the client needs
+ to bind to reestablish its authentication state before performing
+ the requested operation.
-9. TLS Ciphersuites
+13. TLS Ciphersuites
- A client or server that supports TLS MUST support
- TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA and MAY support other ciphersuites
- offering equivalent or better protection.
+ A client or server that supports TLS MUST support
+ TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA. Servers SHOULD NOT support
+ weaker ciphersuites unless other data integrity and
+ confidentiality protection (such as a SASL security layer) is
+ in place
Several issues should be considered when selecting TLS ciphersuites
that are appropriate for use in a given circumstance. These issues
some TLS ciphersuites provide no confidentiality protection
while other ciphersuites that do provide confidentiality
protection may be vulnerable to being cracked using brute force
+
+
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+
methods, especially in light of ever-increasing CPU speeds that
reduce the time needed to successfully mount such attacks.
data, unless the network configuration is such that the danger
of a man-in-the-middle attack is tolerable.
-9.1. TLS Ciphersuites Recommendations
+13.1. TLS Ciphersuites Recommendations
As of the writing of this document, the following recommendations
regarding TLS ciphersuites are applicable. Because circumstances are
but is hoped that it will serve as a useful starting point for
implementers.
-
-
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-
The following ciphersuites defined in [TLS] MUST NOT be used for
confidentiality protection of passwords or data:
TLS_DH_anon_WITH_DES_CBC_SHA
TLS_DH_anon_WITH_3DES_EDE_CBC_SHA
-
-10. Security Considerations
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+
- Security issues are discussed throughout this memo; the
- (unsurprising) conclusion is that mandatory security is important
- and that session confidentiality protection is required when
- snooping is a problem.
+
+14. Security Considerations
- Servers are encouraged to prevent modifications by anonymous users.
+ Security issues are discussed throughout this memo; the unsurprising
+ conclusion is that mandatory security is important and that session
+ confidentiality protection is required when snooping is a problem.
Servers can minimize denial of service attacks by timing out idle
connections, and returning the unwillingToPerform resultCode rather
Operational experience shows that clients can (and frequently do)
misuse unauthenticated bind (see section 5.1). For example, a
client program might make a decision to grant access to non-
-
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-
directory information on the basis of completing a successful bind
operation. Some LDAP server implementations will return a success
response to an unauthenticated bind thus leaving the client with the
Access control SHOULD always be applied when reading sensitive
information or updating directory information.
- A connection on which the client has not performed the Start TLS
- operation or negotiated a suitable SASL mechanism for connection
- integrity and encryption services is subject to man-in-the-middle
- attacks to view and modify information in transit.
+ A connection on which the client has not established connection
+ integrity and privacy services (e.g via Start TLS, IPSec or a
+ suitable SASL mechanism) is subject to man-in-the-middle attacks to
+ view and modify information in transit.
-10.1. Start TLS Security Considerations
+14.1. Start TLS Security Considerations
The goals of using the TLS protocol with LDAP are to ensure
connection confidentiality and integrity, and to optionally provide
Once established, TLS only provides for and ensures confidentiality
and integrity of the operations and data in transit over the LDAP
- association--and only if the implementations on the client and
- server support and negotiate it. The use of TLS does not provide or
- ensure for confidentiality and/or non-repudiation of the data housed
- by an LDAP-based directory server. Nor does it secure the data from
+ connection--and only if the implementations on the client and server
+ support and negotiate it. The use of TLS does not provide or ensure
+ for confidentiality and/or non-repudiation of the data housed by an
+
+
+Harrison Expires July 2004 [Page 18]
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+
+ LDAP-based directory server. Nor does it secure the data from
inspection by the server administrators.
The level of security provided though the use of TLS depends
directly on both the quality of the TLS implementation used and the
style of usage of that implementation. Additionally, an active-
intermediary attacker can remove the Start TLS extended operation
- from the supportedExtension attribute of the root DSE. Therefore,
- both parties SHOULD independently ascertain and consent to the
- security level achieved once TLS is established and before beginning
- use of the TLS connection. For example, the security level of the
- TLS connection might have been negotiated down to plaintext.
+ from the supported attribute of the root DSE. Therefore, both
+ parties SHOULD independently ascertain and consent to the security
+ level achieved once TLS is established and before beginning use of
+ the TLS connection. For example, the security level of the TLS
+ connection might have been negotiated down to plaintext.
Clients SHOULD either warn the user when the security level achieved
- does not provide confidentiality and/or integrity protection, or be
- configurable to refuse to proceed without an acceptable level of
- security.
+ does not provide data confidentiality and/or integrity protection,
+ or be configurable to refuse to proceed without an acceptable level
+ of security.
Client and server implementors SHOULD take measures to ensure proper
protection of credentials and other confidential data where such
measures are not otherwise provided by the TLS implementation.
-
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-
Server implementors SHOULD allow for server administrators to elect
whether and when connection confidentiality and/or integrity is
Additional security considerations relating to the EXTERNAL
mechanism to negotiate TLS can be found in [SASL] and [TLS].
-11. IANA Considerations
+15. IANA Considerations
The following IANA considerations apply to this document:
Normative References
- [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
- Requirement Levels", BCP 14, RFC 2119, March 1997.
-
- [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
- Specifications: ABNF", RFC 2234, November 1997.
+
+Harrison Expires July 2004 [Page 19]
+\f
+Internet-Draft LDAP Authentication Methods 5 December 2003
+
+ [ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for
+ Syntax Specifications: ABNF", RFC 2234, November 1997.
+
[DIGEST-MD5] Leach, P. C. Newman, and A. Melnikov, "Using Digest
- Authentication as a SASL Mechanism", draft-ietf-sasl-rfc2831bis-
- xx.txt, a work in progress.
+ Authentication as a SASL Mechanism", draft-ietf-sasl-
+ rfc2831bis-xx.txt, a work in progress.
- [LDAPDN] Zeilenga, Kurt D. (editor), "LDAP: String Representation of
- Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, a work in
- progress.
+ [Keyword] Bradner, S., "Key Words for use in RFCs to Indicate
+ Requirement Levels", BCP 14, RFC 2119, March 1997.
- [Models] Zeilenga, Kurt D. (editor), "LDAP: Directory Information
- Models", draft-ietf-ldapbis-models-xx.txt, a work in progress.
+ [LDAPDN] Zeilenga, Kurt D. (editor), "LDAP: String
+ Representation of Distinguished Names", draft-ietf-
+ ldapbis-dn-xx.txt, a work in progress.
- [Protocol] Sermersheim, J., "LDAP: The Protocol", draft-ietf-
- ldapbis-protocol-xx.txt, a work in progress.
+ [Models] Zeilenga, Kurt D. (editor), "LDAP: Directory
+ Information Models", draft-ietf-ldapbis-models-xx.txt,
+ a work in progress.
- [Roadmap] K. Zeilenga, "LDAP: Technical Specification Road Map",
- draft-ietf-ldapbis-roadmap-xx.txt, a work in progress.
-
-Harrison Expires June 2004 [Page 22]
-\f
-Internet-Draft LDAP Authentication Methods 5 December 2003
-
+ [Protocol] Sermersheim, J., "LDAP: The Protocol", draft-ietf-
+ ldapbis-protocol-xx.txt, a work in progress.
- [SASL] Melnikov, A. (editor), "Simple Authentication and Security
- Layer (SASL)", draft-ietf-sasl-rfc2222bis-xx.txt, a work in
- progress.
+ [Roadmap] K. Zeilenga, "LDAP: Technical Specification Road Map",
+ draft-ietf-ldapbis-roadmap-xx.txt, a work in progress.
- [SASLPrep] Zeilenga, K., "Stringprep profile for user names and
- passwords", draft-ietf-sasl-saslprep-xx.txt, (a work in
- progress).
+ [SASL] Melnikov, A. (editor), "Simple Authentication and
+ Security Layer (SASL)", draft-ietf-sasl-rfc2222bis-
+ xx.txt, a work in progress.
- [StringPrep] Hoffman P. and M. Blanchet, "Preparation of
- Internationalized Strings ('stringprep')", draft-hoffman-
- rfc3454bis-xx.txt, a work in progress.
+ [SASLPrep] Zeilenga, K., "Stringprep profile for user names and
+ passwords", draft-ietf-sasl-saslprep-xx.txt, (a work in
+ progress).
- [Syntaxes] Legg, S. (editor), "LDAP: Syntaxes and Matching Rules",
- draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress.
+ [StringPrep] Hoffman P. and M. Blanchet, "Preparation of
+ Internationalized Strings ('stringprep')", draft-
+ hoffman-rfc3454bis-xx.txt, a work in progress.
- [TLS] Dierks, T. and C. Allen. "The TLS Protocol Version 1.1",
- draft-ietf-tls-rfc2246-bis-xx.txt, a work in progress.
-
- [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO 10646",
- RFC 3629, STD 63, November 2003.
+ [Syntaxes] Legg, S. (editor), "LDAP: Syntaxes and Matching Rules",
+ draft-ietf-ldapbis-syntaxes-xx.txt, a work in progress.
+
+ [TLS] Dierks, T. and C. Allen. "The TLS Protocol Version
+ 1.1", draft-ietf-tls-rfc2246-bis-xx.txt, a work in
+ progress.
- [Unicode] The Unicode Consortium, "The Unicode Standard, Version
- 3.2.0" is defined by "The Unicode Standard, Version 3.0"
- (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-61633-5), as
- amended by the "Unicode Standard Annex #27: Unicode 3.1"
- (http://www.unicode.org/reports/tr27/) and by the öUnicode
- Standard Annex #28: Unicode 3.2"
- (http://www.unicode.org/reports/tr28/).
+ [UTF-8] Yergeau, F., "UTF-8, a transformation format of ISO
+ 10646", RFC 3629, STD 63, November 2003.
+
+ [Unicode] The Unicode Consortium, "The Unicode Standard, Version
+ 3.2.0" is defined by "The Unicode Standard, Version
+ 3.0" (Reading, MA, Addison-Wesley, 2000. ISBN 0-201-
+ 61633-5), as amended by the "Unicode Standard Annex
+ #27: Unicode 3.1"
+ (http://www.unicode.org/reports/tr27/) and by the
+ "Unicode Standard Annex #28: Unicode 3.2"
+ (http://www.unicode.org/reports/tr28/).
+
+Harrison Expires July 2004 [Page 20]
+\f
+Internet-Draft LDAP Authentication Methods 5 December 2003
+
Informative References
- [ANONYMOUS] Zeilenga, K.,"Anonymous SASL Mechanism", draft-zeilenga-
- sasl-anon-xx.txt, a work in progress.
+ [ANONYMOUS] Zeilenga, K.,"Anonymous SASL Mechanism", draft-
+ zeilenga-sasl-anon-xx.txt, a work in progress.
- [PLAIN] Zeilenga, K.,"Plain SASL Mechanism", draft-zeilenga-sasl-
- plain-xx.txt, a work in progress.
+ [Glossary] Shirey, R., "Internet Security Glossary", RFC 2828, May
+ 2000.
- [RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May
- 2000.
+ [PLAIN] Zeilenga, K.,"Plain SASL Mechanism", draft-zeilenga-
+ sasl-plain-xx.txt, a work in progress.
- [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
- Internet Protocol", RFC 2401, November 1998.
+ [SecArch] Kent, S. and R. Atkinson, "Security Architecture for
+ the Internet Protocol", RFC 2401, November 1998.
Author's Address
Novell, Inc.
1800 S. Novell Place
Provo, UT 84606
+ USA
+1 801 861 2642
roger_harrison@novell.com
+Appendix A. LDAP Association State Transition Tables
+
+ This section provides a state transition table to represent a state
+ diagram for the various authentication and TLS states through which
+ an LDAP association may pass during the course of its existence and
+ the actions that cause these changes in state.
+
+ This section is based entirely on information found in this document
+ and other documents that are part of the LDAP Technical
+ Specification [Roadmap]. As such, it is strictly informational in
+ nature.
+
+A.1. LDAP Association States
+
+ The following table lists the valid LDAP association states and
+ provides a description of each state. The ID for each state is used
+ in the state transition table in section A.4.
+
+ ID State Description
+ -- --------------------------------------------------------------
+ S1 Anonymous
+ no Authentication ID is associated with the LDAP connection
+ no Authorization ID is in force
+ S2 Authenticated
+ Authentication ID = I
+ Authorization ID = X
+ S3 Authenticated SASL EXTERNAL, implicit authorization ID
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-Appendix A. Example Deployment Scenarios
+ Authentication ID = J
+ Authorization ID = Y
+ S4 Authenticated SASL EXTERNAL, explicit authorization ID
+ Authentication ID = J
+ Authorization ID = Z
+
+A.2. Actions that Affect LDAP Association State
+
+ The following table lists the actions that can affect the
+ authentication and authorization state of an LDAP association. The
+ ID for each action is used in the state transition table in section
+ A.4.
+
+ ID Action
+ -- --------------------------------------------------------------
+ A1 Client bind request fails
+ A2 Client successfully performs anonymous simple bind
+ A3 Client successfully performs unauthenticated simple bind
+ A4 Client successfully performs simple bind with name and
+ password OR SASL bind with any mechanism except EXTERNAL using
+ an authentication ID = I that maps to authorization ID X
+ A5 Client Binds SASL EXTERNAL with implicit assertion of
+ authorization ID (section 3.3.6.1)]. The current
+ authentication ID maps to authorization ID = Y.
+ A6 Client Binds SASL EXTERNAL with explicit assertion of
+ authorization ID = Z (section 3.3.6.2)]
+ A7 Client abandons a bind operation, and server processes the
+ abandon
+ A8 Client abandons a bind operation, and server does not process
+ the abandon
+ A9 Client Start TLS request fails
+ A10 Client Start TLS request succeeds
+ A11 Client or Server: graceful TLS closure ([Protocol] section
+ 4.13.3.1.)
+
+A.3. Decisions Used in Making LDAP Association State Changes
+
+ Certain changes in the authentication and authorization state of an
+ LDAP association are only allowed if the server can affirmatively
+ answer a question. These questions are applied as part of the
+ criteria for allowing or disallowing a state transition in the state
+ transition table in section A.4.
+
+ ID Decision Question
+ -- --------------------------------------------------------------
+ D1 Are lower-layer credentials available?
+ D2 Can lower-layer credentials for Auth ID "K" be mapped to
+ asserted AuthZID "L"?
+
+A.4. LDAP Association State Transition Table
+
+ The LDAP Association table below lists the valid authentication and
+ authorization states for an LDAP association and the actions that
+
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+
+ could affect them. For any given row in the table, the Current State
+ column gives the state of an LDAP association, the Action column
+ gives an action that could affect the state of an LDAP assocation,
+ and the Next State column gives the resulting state of an LDAP
+ association after the action occurs.
+
+ S1, the initial state for the state machine described in this table,
+ is the authentication state when an LDAP connection is initially
+ established.
+
+ Current Next
+ State Action State Comment
+ ------- ------- ----- ---------------------------------------
+ Any A1 S1 [Protocol] section 4.2.1
+ Any A2 S1 Section 6
+ Any A3 S1 Section 6
+ Any A4 S2 Sections 6.1, 6.2
+ Any A5, S1 Failed bind, section 3.3.6
+ D1=no
+ Any A5, S3
+ D1=yes
+ Any A6, S1 failed bind, section 3.3.6
+ D1=no
+ Any A6, S1 failed bind, section 3.3.6.2
+ D1=yes,
+ D2=no
+ Any A6, S4
+ D1=yes,
+ D2=yes
+ Any A7 S1 [Protocol] section 4.2.1. Clients
+ cannot detect this state.
+ Any A8 no [Protocol] section 4.2.1. Clients
+ change cannot detect this state.
+ Any A9 no [Protocol] section 4.13.2.2
+ change
+ Any A10 no Section 4.2.1
+ change
+ Any A11 S1 Section 4.2.3
+
+Appendix B. Example Deployment Scenarios
The following scenarios are typical for LDAP directories on the
Internet, and have different security requirements. (In the
(1) A read-only directory, containing no sensitive data, accessible
to "anyone", and TCP connection hijacking or IP spoofing is not
a problem. Anonymous authentication, described in section 7, is
+
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+
suitable for this type of deployment, and requires no additional
security functions except administrative service limits.
(5) A directory containing sensitive data. This scenario requires
data confidentiality protection AND secure authentication.
-Appendix B. Authentication and Authorization: Definitions and Concepts
+Appendix C. Authentication and Authorization Concepts
This appendix defines basic terms, concepts, and interrelationships
regarding authentication, authorization, credentials, and identity.
These concepts are used in describing how various security
approaches are utilized in client authentication and authorization.
-B.1. Access Control Policy
+C.1. Access Control Policy
An access control policy is a set of rules defining the protection
of resources, generally in terms of the capabilities of persons or
- other entities accessing those resources. A common expression of an
- access control policy is an access control list. Security objects
- and mechanisms, such as those described here, enable the expression
- of access control policies and their enforcement. Access control
-
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+ other entities accessing those resources. Security objects and
+ mechanisms, such as those described here, enable the expression of
+ access control policies and their enforcement.
- policies are typically expressed in terms of access control factors
- as described below.
-
-B.2. Access Control Factors
+C.2. Access Control Factors
A request, when it is being processed by a server, may be associated
with a wide variety of security-related factors (section 4.2 of
Access control policies are expressed in terms of access control
factors. E.g., a request having ACFs i,j,k can perform operation Y
+
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+
on resource Z. The set of ACFs that a server makes available for
such expressions is implementation-specific.
-B.3. Authentication, Credentials, Identity
+C.3. Authentication, Credentials, Identity
Authentication credentials are the evidence supplied by one party to
another, asserting the identity of the supplying party (e.g. a user)
mechanism may constrain the form of authentication identities used
with it.
-B.4. Authorization Identity
+C.4. Authorization Identity
An authorization identity is one kind of access control factor. It
is the name of the user or other entity that requests that
privileges of the identity for which they are proxying [SASL]. Also,
the form of authentication identity supplied by a service like TLS
may not correspond to the authorization identities used to express a
-
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-
server's access control policy, requiring a server-specific mapping
to be done. The method by which a server composes and validates an
authorization identity from the authentication credentials supplied
by a client is implementation-specific.
-Appendix C. RFC 2829 Change History
+Appendix D. RFC 2829 Change History
This appendix lists the changes made to the text of RFC 2829 in
preparing this document.
-C.0. General Editorial Changes
+D.0. General Editorial Changes
Version -00
- Changed other instances of the term LDAP to LDAP where v3 of the
protocol is implied. Also made all references to LDAP use the
same wording.
+
+Harrison Expires July 2004 [Page 25]
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+
- Miscellaneous grammatical changes to improve readability.
- Made capitalization in section headings consistent.
- Changed title to reflect inclusion of material from RFC 2830 and
2251.
-C.1. Changes to Section 1
+D.1. Changes to Section 1
Version -01
- Moved conventions used in document to a separate section.
-C.2. Changes to Section 2
+D.2. Changes to Section 2
Version -01
- Moved section to an appendix.
-C.3. Changes to Section 3
+D.3. Changes to Section 3
Version -01
- Moved section to an appendix.
-C.4 Changes to Section 4
+D.4 Changes to Section 4
Version -00
- Changed "Distinguished Name" to "LDAP distinguished name".
-C.5. Changes to Section 5
+D.5. Changes to Section 5
Version -00
-
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-\f
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-
- Added the following sentence: "Servers SHOULD NOT allow clients
with anonymous authentication to modify directory entries or
access sensitive information in directory entries."
-C.5.1. Changes to Section 5.1
+D.5.1. Changes to Section 5.1
Version -00
- Brought text describing procedure for performing an anonymous
bind from section 4.2 of RFC 2251 bis. This text will be
removed from the draft standard version of that document.
+
+Harrison Expires July 2004 [Page 26]
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+
-C.6. Changes to Section 6.
+D.6. Changes to Section 6.
Version -00
implementations MUST support authentication with a password...")
to section on Digest Authentication (Now section 6.2).
-C.6.1. Changes to Section 6.1.
+D.6.1. Changes to Section 6.1.
Version -00 Renamed section to 6.2
DIGEST-MD5 SASL mechanism is required for all conforming LDAP
implementations
-C.6.2. Changes to Section 6.2
+D.6.2. Changes to Section 6.2
Version -00
- Renamed section to 6.3
-
-
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-
- Reworded first paragraph to remove reference to user and the
userPassword password attribute Made the first paragraph more
general by simply saying that if a directory supports simple
sent in the bind request to a directory entry with a
userPassword attribute."
-C.6.3. Changes to section 6.3.
+D.6.3. Changes to section 6.3.
+
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+\f
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+
Version -00
- Renamed to section 6.4.
-C.7. Changes to section 7.
+D.7. Changes to section 7.
none
-C.7.1. Changes to section 7.1.
+D.7.1. Changes to section 7.1.
Version -00
"to have issued the certificate" immediately after
"Certification Authority."
-C.8. Changes to section 8.
+D.8. Changes to section 8.
Version -00
for Other Security Services) to bring material on SASL
mechanisms together into one location.
-C.9. Changes to section 9.
-
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-
+D.9. Changes to section 9.
Version -00
- Added section 9.1.1. heading.
- Added section 9.1.2. heading.
+
+Harrison Expires July 2004 [Page 28]
+\f
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+
Version -01
- Moved entire section 9 to become section 3.5 so that it would be
with other SASL material.
-C.10. Changes to Section 10.
+D.10. Changes to Section 10.
Version -00
equivalent or better protection," to the last paragraph of the
section.
-C.11. Changes to Section 11.
+D.11. Changes to Section 11.
Version -01
- Moved to section 3.6 to be with other SASL material.
-C.12. Changes to Section 12.
+D.12. Changes to Section 12.
Version -00
is renumbered to become section 13.
Version -01
-
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-\f
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-
- Moved to section 3.7 to be with other SASL material.
-C.13. Changes to Section 13 (original section 12).
+D.13. Changes to Section 13 (original section 12).
None
-Appendix D. RFC 2830 Change History
+Appendix E. RFC 2830 Change History
This appendix lists the changes made to the text of RFC 2830 in
preparing this document.
-D.0. General Editorial Changes
+E.0. General Editorial Changes
- Material showing the PDUs for the Start TLS response was broken
out into a new section.
+
+
+Harrison Expires July 2004 [Page 29]
+\f
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+
- The wording of the definition of the Start TLS request and Start
TLS response was changed to make them parallel. NO changes were
made to the ASN.1 definition or the associated values of the
- A separate section heading for graceful TLS closure was added
for parallelism with section on abrupt TLS closure.
-Appendix E. RFC 2251 Change History
+Appendix F. RFC 2251 Change History
This appendix lists the changes made to the text of RFC 2251 in
preparing this document.
-E.0. General Editorial Changes
+F.0. General Editorial Changes
- All material from section 4.2 of RFC 2251 was moved into this
document.
the discussion of the Bind operation (primarily sections 4.4 -
4.7).
-Appendix F. Change History to Combined Document
+Appendix G. Change History to Combined Document
-F.1. Changes for draft-ldap-bis-authmeth-02
+G.1. Changes for draft-ldap-bis-authmeth-02
General
-
-
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-\f
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-
- Added references to other LDAP standard documents, to sections
within the document, and fixed broken references.
Section 3.
+
+
+Harrison Expires July 2004 [Page 30]
+\f
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+
- Brought language in requirement (3) in line with security
glossary.
- Brought security terminology in line with IETF security glossary
throughout the appendix.
-F.2. Changes for draft-ldap-bis-authmeth-03
-
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-\f
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-
+G.2. Changes for draft-ldap-bis-authmeth-03
General
references to conform to WG chair suggestions for the overall
technical specification.
- - Several issues--G.13, G.14, G.16, G.17--were resolved without
+ - Several issues--H.13, H.14, H.16, H.17--were resolved without
requiring changes to the document.
Section 3
Section 4
+
+
+Harrison Expires July 2004 [Page 31]
+\f
+Internet-Draft LDAP Authentication Methods 5 December 2003
+
- Removed sections 4.1, 4.2 and parts of section 4.3. This
information was being duplicated in the protocol specification
and will now reside there permanently.
information.
-F.3. Changes for draft-ldap-bis-authmeth-04
+G.3. Changes for draft-ldap-bis-authmeth-04
General
- Changed references to use [RFCnnnn] format wherever possible.
(References to works in progress still use [name] format.)
-
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-\f
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-
- Various edits to correct typos and bring field names, etc. in
line with specification in [Protocol] draft.
- - Several issues--G.13, G.14, G.16, G.17--were resolved without
+ - Several issues--H.13, H.14, H.16, H.17--were resolved without
requiring changes to the document.
Section 4.4.1.
- Removed sections 5.1, 5.2, and 5.4 that will be added to
[Protocol]. Renumbered sections to accommodate this change.
-
+
+Harrison Expires July 2004 [Page 32]
+\f
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+
Section 6
that actions are in ascending order (makes analyzing the table
much more logical). Added action A2 to several states where it
was missing and valid. Added actions A7 and A8 placeholders to
- states S1, S2, S4 and S5 pending resolution of issue G.28.
+ states S1, S2, S4 and S5 pending resolution of issue H.28.
Section 11
- Verified all normative references and moved informative
references to a new section 14.
-F.4. Changes for draft-ldap-bis-authmeth-05
+G.4. Changes for draft-ldap-bis-authmeth-05
General
- Updated to match current contents of documents. This was needed
due to movement of material on Bind and Start TLS operations to
[Protocol] in this revision.
-
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-\f
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-
Section 3.
revision of the draft.
+
+
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+\f
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+
- Paragraph beginning, " If TLS is negotiated, the client MUST
discard all information..." was moved to section 5.1.7 and
integrated with related material there.
Section 5.1.7.
-
-
-
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-
- Wording from section 3 paragraph beginning " If TLS is
negotiated, the client MUST discard all information..." was
moved to this section and integrated with existing text.
Section 8.1.
+
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+
- Changed term "data privacy" to "data confidentiality" to be
consistent with usage in rest of document.
confidentiality protection" to be consistent with usage in rest
of document.
- Appendix A.
+ Appendix B.
- Began changes to incorporate information on deployment scenarios
removed from section 3.
-F.5. Changes for draft-ldap-bis-authmeth-06
+G.5. Changes for draft-ldap-bis-authmeth-06
General
Section 1
-
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-
- Added additional example of spoofing under threat (7).
Section 2.1
- Began edits to LDAP Association state table to clarify meaning
of various states and actions.
+
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+
- Added action A9 to cover abandoned bind operation and added
appropriate transitions to the state transition table to
- Added a clarifying example to the consideration regarding misuse
of unauthenticated access.
-F.6. Changes for draft-ldap-bis-authmeth-07
+G.6. Changes for draft-ldap-bis-authmeth-07
General
- Rewrote much of section 3.3 to meet the SASL profile
requirements of draft-ietf-sasl-rfc2222bis-xx.txt section 5.
-
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-
- Changed treatement of SASL ANONYMOUS and PLAIN mechanisms to
bring in line with WG consensus.
The local policy in place for implicit assertion is adequate.
Section 7
+
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+
- Removed most of section 7.2 as the information is now covered
adequately via the new SASL profile in section 3.3. Added note
to any member of the set of stored passwords constitutes a
successful authentication.
-F.6. Changes for draft-ldap-bis-authmeth-08
+G.7. Changes for draft-ldap-bis-authmeth-08
General
- Added 1.5 sentences at end of introductory paragraph indicating
the effect of the Bind op on the LDAP association.
-
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-
Section 3.1
- Retitled section and clarified wording
Section 3.3.5
+
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+
- Changed requirement to discard information about server fetched
prior to SASL negotiation from MUST to SHOULD to allow for
information obtained through secure mechanisms.
Section 4.1.6
- Renumbered to 4.1.5.
-
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-
- Updated server identity check rules for server's name based on
WG list discussion.
Section 10
+
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+
- Added security consideration (moved from elsewhere) discouraging
use of cleartext passwords on unprotected communication
channels.
- Added an IANA consideration to update GSSAPI service name
registry to point to [Roadmap] and [Authmeth]
-F.7. Changes for draft-ldap-bis-authmeth-09
+G.8. Changes for draft-ldap-bis-authmeth-09
General
- Reworded sentence beginning, "It is also desireable to allow
authentication methods to carry identities based on existingù
- non-LDAP DNùforms..."
+ non-LDAP DN-forms..."
- Clarified relationship of this document to other documents in
the LDAP TS.
Section 3.3.5
-
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-
- Removed paragraph beginning,"If the client is configured to
support multiple SASL mechanisms..." because the actions
- Moved most of section 4.2.2, Client Assertion of Authorization
Identity, to sections 3.3.6, 3.3.6.1, and 3.3.6.2.
+
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+
Section 3.3.6.4
- Moved some normative comments into text body.
- Added sentence describing protections provided by DIGEST-MD5
method.
- Changed DNs in exmple to be dc=example,dc=com.
-
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-
Section 10
- Substantial rework of consideration on misuse of unauthenticated
bind.
-Appendix G. Issues to be Resolved
+G.9. Changes for draft-ldap-bis-authmeth-10
+
+
+ - Reorganized content of sections 3-9 to improve document flow and
+ reduce redundancy.
+ - Resolved issue of effect of Start TLS and TLS closure on LDAP
+ association state.
+ - Made numerous minor wording changes based on WG feedback.
+ - Updated list of threats for Section 1.
+
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+
+ - Recommendation that servers should not support weaker TLS
+ ciphersuites unless other protection is in place.
+ - Moved authentication state table to appendix and relettered
+ appendices.
+
+Appendix H. Issues to be Resolved
This appendix lists open questions and issues that need to be
resolved before work on this document is deemed complete.
-G.1.
+H.1.
Section 1 lists 6 security mechanisms that can be used by LDAP
servers. I'm not sure what mechanism 5, "Resource limitation by
Status: resolved. Changed wording to "administrative service limits"
to clarify meaning.
-G.2.
+H.2.
Section 2 paragraph 1 defines the term, "sensitive." Do we want to
bring this term and other security-related terms in alignment with
Status: resolved. WG input at IETF 51 was that we should do this, so
the appropriate changes have been made.
-G.3.
+H.3.
Section 2, deployment scenario 2: What is meant by the term "secure
authentication function?"
data confidentiality for sensitive authentication information and
data integrity for all authentication information.
-G.4.
+H.4.
Section 3, deployment scenario 3: What is meant by the phrase,
"directory data is authenticated by the server?"
the identity of the directory server and the integrity of the data
sent from that server to the client, and explictly stated such.
-G.5.
+H.5.
-
+ Section 4 paragraph 3: What is meant by the phrase, "this means that
+ either this data is useless for faking authentication (like the Unix
+ "/etc/passwd" file format used to be)?"
+
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- Section 4 paragraph 3: What is meant by the phrase, "this means that
- either this data is useless for faking authentication (like the Unix
- "/etc/passwd" file format used to be)?"
-
Status: resolved. Discussion at IETF 52 along with discussions with
the original authors of this material have convinced us that this
reference is simply too arcane to be left in place. In -03 the text
update it in session well protected against snooping, and the
reference to /etc/passwd has been removed.
-G.6.
+H.6.
Section 4 paragraph 7 begins: "For a directory needing session
protection..." Is this referring to data confidentiality or data
Status: resolved. Changed wording to say, "For a directory needing
data security (both data integrity and data confidentiality)..."
-G.7.
+H.7.
Section 4 paragraph 8 indicates that "information about the server
fetched prior to the TLS negotiation" must be discarded. Do we want
meeting, this has been changed to explicitly state, "fetched prior
to the initiation of the TLS negotiation..."
-G.8.
+H.8.
Section 4 paragraph 9 indicates that clients SHOULD check the
supportedSASLMechanisms list both before and after a SASL security
Approach 2: Clients MUST check the supportedSASLMechanisms list
both before and after SASL negotiation UNLESS they use a
+ different trusted source to determine available supported SASL
+ mechanisms.
+
+
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- different trusted source to determine available supported SASL
- mechanisms.
-
Status: resolved. WG input at IETF 51 was that Approach 1 was
probably best. I ended up keeping the basic structure similar to the
original to meet this intent.
-G.9.
+H.9.
Section 6.3.1 states: "DSAs that map the DN sent in the bind request
to a directory entry with a userPassword attribute will... compare
"user" in referring to the directory entry specified by the DN in
the bind request.
-G.10 userPassword and simple bind
+H.10 userPassword and simple bind
We need to be sure that we don't require userPassword to be the only
attribute used for authenticating via simple bind. (See 2251 sec 4.2
"user" in referring to the directory entry specified by the DN in
the bind request.
-G.11. Meaning of LDAP Association
+H.11. Meaning of LDAP Association
The original RFC 2830 uses the term "LDAP association" in describing
a connection between an LDAP client and server regardless of the
clarified somewhere in the draft. Added "LDAP association" to a
glossary in section 1.
-G.12. Is DIGEST-MD5 mandatory for all implementations?
+H.12. Is DIGEST-MD5 mandatory for all implementations?
Reading 2829bis I think DIGEST-MD5 is mandatory ONLY IF your server
supports password based authentication...but the following makes it
sound mandatory to provide BOTH password authentication AND DIGEST-
+ MD5:
+
+ "6.2. Digest authentication
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- MD5:
-
- "6.2. Digest authentication
LDAP implementations MUST support authentication with a password
using the DIGEST-MD5 SASL mechanism for password protection, as
beginning of section 8.2 stating that LDAP server implementations
must support this method.
-G.13. Ordering of authentication levels requested
+H.13. Ordering of authentication levels requested
Again on the subject of authentication level, is it possible to
define an ordering on authentication levels which defines their
Status: out of scope. This is outside the scope of this document and
will not be addressed.
-G.14. Document vulnerabilities of various mechanisms
+H.14. Document vulnerabilities of various mechanisms
While I'm here...in 2829, I think it would be good to have some
comments or explicit reference to a place where the security
Status: out of scope. This is outside the scope of this document and
will not be addressed.
-G.15. Include a Start TLS state transition table
+H.15. Include a Start TLS state transition table
The pictoral representation it is nominally based on is here (URL
possibly folded):
http://www.stanford.edu/~hodges/doc/LDAPAssociationStateDiagram-
1999-12-14.html
-Harrison Expires June 2004 [Page 44]
+ (Source: Jeff Hodges)
+
+
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-
- (Source: Jeff Hodges)
-
Status: Resolved.
Table provided in -03. Review of content for accuracy in -04.
were based on suggestions from WG and greatly simplified overall
table.
-G.16. Empty sasl credentials question
+H.16. Empty sasl credentials question
I spent some more time looking microscopically at ldap-auth-methods
and ldap-ext-tls drafts. The drafts say that the credential must
discussion at IETF 52 that SASL AuthzID credentials empty and absent
are equivalent in the latest SASL ID. This resolves the issue.
-G.17. Hostname check from MUST to SHOULD?
+H.17. Hostname check from MUST to SHOULD?
I am uneasy about the hostname check. My experience from PKI with
HTTP probably is a contributing factor; we have people using the
Status: resolved. Based on discussion at IETF 52 ldapbis WG meeting,
this text will stand as it is. The check is a MUST, but the behavior
+ afterward is a SHOULD. This gives server implementations the room to
+ maneuver as needed.
+
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- afterward is a SHOULD. This gives server implementations the room to
- maneuver as needed.
-
-G.18. Must SASL DN exist in the directory?
+H.18. Must SASL DN exist in the directory?
If the 'dn:' form of sasl creds is used, is it the intention of the
draft(ers) that this DN must exist in the directory and the client
policy driven [SASL] section 4.2, and (3) keeping this paragraph is
not required for interoperability.
-G.19. DN used in conjunction with SASL mechanism
+H.19. DN used in conjunction with SASL mechanism
We need to specify whether the DN field in Bind operation can/cannot
be used when SASL mechanism is specified. (source: RL Bob)
conflicts with this draft. The editor of [Protocol] has been
notified of the discrepancy, and they have been handled.
-G.20. Bind states
+H.20. Bind states
Differences between unauthenticated and anonymous. There are four
states you can get into. One is completely undefined (this is now
called out in [AuthMeth]. State 3 is called out in [Protocol]; this
seems appropriate based on review of alternatives.
+H.21. Misuse of unauthenticated access
+
+
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-G.21. Misuse of unauthenticated access
-
Add a security consideration that operational experience shows that
clients can misuse unauthenticated access (simple bind with name but
no password). Servers SHOULD by default reject authentication
Status: Resolved. Added to security considerations in -03.
-G.22. Need to move Start TLS protocol information to [Protocol]
+H.22. Need to move Start TLS protocol information to [Protocol]
Status: Resolved. Removed Sections 5.1, 5.2, and 5.4 for -04 and
they are [Protocol] -11.
-G.23. Split Normative and Non-normative references into separate
+H.23. Split Normative and Non-normative references into separate
sections.
Status: Resolved. Changes made in -04
-G.24. What is the authentication state if a Bind operation is
+H.24. What is the authentication state if a Bind operation is
abandoned?
Status: Resolved.
(6/28/03): The state table in section 6 of [AuthMeth] has been
updated to reflect this wording.
-G.25. Difference between checking server hostname and server's
+H.25. Difference between checking server hostname and server's
canonical DNS name in Server Identity Check?
Section 4.1.6: I now understand the intent of the check (prevent
(11/21/02): RL Bob Morgan will provide wording that allows
derivations of the name that are provided securely.
+ (6/28/03): posted to the WG list asking Bob or any other WG member
+ who is knowledgeable about the issues involved to help me with
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- (6/28/03): posted to the WG list asking Bob or any other WG member
- who is knowledgeable about the issues involved to help me with
wording or other information I can use to make this change and close
the work item.
(e.g., DNSSEC)."
-G.26. Server Identity Check using servers located via SRV records
+H.26. Server Identity Check using servers located via SRV records
Section 4.1.6: What should be done if the server was found using SRV
records based on the "locate" draft/RFC? (Source: Tim Hahn).
This is the right location for this information, and the coverage
appears to be adequate.
-G.27 Inconsistency in effect of TLS closure on LDAP association.
+H.27 Inconsistency in effect of TLS closure on LDAP association.
Section 4.4.1 of authmeth -03 (section 4.1 of RFC2830) states that
TLS closure alert will leave the LDAP association intact. Contrast
intact. The authentication state table in [AuthMeth] specifies the
effect on the LDAP association.
-G.28 Ordering of external sources of authorization identities
+H.28 Ordering of external sources of authorization identities
+ Section 4.3.2 implies that external sources of authorization
+ identities other than TLS are permitted. What is the behavior when
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- Section 4.3.2 implies that external sources of authorization
- identities other than TLS are permitted. What is the behavior when
two external sources of authentication credentials are available
(e.g. TLS and IPsec are both present (is this possible?)) and a SASL
EXTERNAL Bind operation is performed?
states that the decision to allow or disallow the asserted identity
is based on an implementation defined policy.
-G.29 Rewrite of Section 9, TLS Ciphersuites
+H.29 Rewrite of Section 9, TLS Ciphersuites
This section contains anachronistic references and needs to be
updated/rewritten in a way that provides useful guidance for future
general issues and considerations involved in selecting TLS
ciphersuites.
-G.30 Update to Appendix A, Example Deployment Scenarios
+H.30 Update to Appendix A, Example Deployment Scenarios
This section needs to be updated to indicate which security
mechanisms and/or combinations of security mechanisms described
elsewhere in the document can provide the types of protections
suggested in this appendix.
-G.31 Use of PLAIN SASL Mechanism
+H.31 Use of PLAIN SASL Mechanism
At least one LDAP server implementer has found the SASL "PLAIN"
mechanism useful in authenticating to legacy systems that do not
allow any SASL mechanism.
-G.32 Clarification on use of SASL mechanisms
+H.32 Clarification on use of SASL mechanisms
Section 3.3.1: BTW, what _are_ the "ANONYMOUS" and "PLAIN" SASL
mechanisms? They are not defined in RFC2222. If you refer to other
+ SASL mechanisms than those in rfc2222, Maybe you should only list
+
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- SASL mechanisms than those in rfc2222, Maybe you should only list
which mechanisms _are_used, instead of which ones are _not. (Source:
Hallvard Furuseth)
-G.33 Clarification on use of password protection based on AuthZID form
+H.33 Clarification on use of password protection based on AuthZID form
Section 3.3.1: "If an authorization identity of a form different
from a DN is requested by the client, a mechanism that protects the
security consideration that covers this issue.
-G.34 Clarification on use of matching rules in Server Identity Check
+H.34 Clarification on use of matching rules in Server Identity Check
The text in section 4.1.6 isn't explicit on whether all rules apply
to both CN and dNSName values. The text should be clear as to which
rules. (Source: Kurt Zeilenga)
-G.35 Requested Additions to Security Considerations
+H.35 Requested Additions to Security Considerations
Requested to mention hostile servers which the user might have been
fooled to into contacting. Which mechanisms that are standardized by
Requested list of methods that need/don't need the server to know
the user's plaintext password. (I say 'know' instead of 'store'
+
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(Source: Hallvard Furuseth)
-G.36 Add reference to definition of DIGEST-MD5
+H.36 Add reference to definition of DIGEST-MD5
Need a reference to the definition of DIGEST-MD5 SASL mechanism in
section 7.2 (Source: Hallvard Furuseth)
Status: Resolved. A reference to to the DIGEST-MD5 SASL mechanism,
[DigestAuth], is included in the -07 revision.
-G.37 Clarification on procedure for certificate-based authentication
+H.37 Clarification on procedure for certificate-based authentication
8.1. Certificate-based authentication with TLS states: "Following
immediately following, or just some time later? Should the wording,
"the client will send..." actually read, "the client MUST send..."?
-G.38 Effect of Start TLS on authentication state
+ Status: Resolved. In -10 this text has been absorbed into the SASL
+ EXTERNAL mechanism section.
+
+H.38 Effect of Start TLS on authentication state
Should the server drop all knowledge of connection, i.e. return to
anonymous state, if it gets a Start TLS request on a connection that
has successfully bound using the simple method?
-G.39 Be sure that there is a consideration in [SCHEMA] that discusses
+ Status: Resolved. In -09 the effect on an LDAP association by a
+ Start TLS operation is made a matter of local policy. This is based
+ on editorÆs perception of WG consensus gaged by conversations at
+ IETF 58 and subsequent discussion on the WG mail list.
+
+H.39 Be sure that there is a consideration in [SCHEMA] that discusses
multiple password values in userPassword
Allowing multiple values obviously does raise a number of security
implementations should be encouraged to provide administrative
controls which, if enabled, restrict userPassword to one value.
-G.40. Clarify need to verify mapping between authentication identity
+H.40. Clarify need to verify mapping between authentication identity
and resulting authorization identity on implicit assertion of AuthZID.
4.2.2.3. Error Conditions
"For either form of assertion, the server MUST verify that the
+
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+
client's authentication identity as supplied in its TLS credentials
is permitted to be mapped to the asserted authorization identity."
IMHO, the mapping can be done as two steps:
a). deriving LDAP authentication identity from TLS credentials; If t
this steps fails, EXTERNAL mechanism returns failure.
-
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-
b). verify that the authorization identity is allowed for the
derived authentication identity. This is always "noop" for the
implicit case.
This text has been moved to apply only to the explicit assertion
case.
-G.41. Section 7.2 contains unnecessary and misleading detail.
+H.41. Section 7.2 contains unnecessary and misleading detail.
" I am not sure why this section is required in the document.
DIGEST-MD5 is defined in a separate document and there should be
rfc2831bis. I then dramatically reduced the material in section 7.2
to a bare minimum and let the SASL profile stand on its own.
-G.42. Does change for G.41 cause interoperability issue?
+H.42. Does change for H.41 cause interoperability issue?
There is one issue with the way the authmeth draft is currently
written that changes the SASL DIGEST-MD5 behavior on the way the
Status: Resolved
+
+
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+
(10/08/03) This item was discussed on the WG list between 5/2/03 and
5/9/03. Consensus apppears to support the notion that RFC 2829 was
in error and that the semantics of RFC 2831 are correct and should
be reflected in authmeth. This is already the case as of the -07
draft.
-G.43. DIGEST-MD5 Realms recommendations for LDAP
+H.43. DIGEST-MD5 Realms recommendations for LDAP
-
-
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From http://www.ietf.org/internet-drafts/draft-ietf-sasl-rfc2222bis-
02.txt: A protocol profile SHOULD provide a guidance how realms are
to be constructed and used in the protocol and MAY further restrict
submissions to provide guidance on the use of realm and realm values
in LDAP.
-G.44. Use of DNs in usernames and realms in DIGEST-MD5
+H.44. Use of DNs in usernames and realms in DIGEST-MD5
+
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+
In reading the discussion on the mailing list, I reach the following
conclusions:
these strings allows strings that look like DNs in form, however,
DIGEST-MD5 treats them a simple strings for comparision purposes.
For example, the DNs cn=roger, o=US and cn=roger,o=us are equivalent
-
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-
when being compared semantically as DNs, however, these would be
considered two different username values in DIGEST-MD5 because
simple octet-wise semantics (rather than DN semantics) are used to
In -07 revision I added notes to implementors expressing this issue
in section 7.2.
-G.45: Open Issue: Is Simple+TLS mandatory to implement?
+H.45: Open Issue: Is Simple+TLS mandatory to implement?
Going forward, it would be much better to clarify that simple
+TLS is to be used for DN/password credentials and DIGEST-MD5
IETF's procedures with respect to rights in standards-track and
standards-related documentation can be found in BCP-11. Copies of
claims of rights made available for publication and any assurances
+
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+
of licenses to be made available, or the result of an attempt made
to obtain a general license or permission for the use of such
proprietary rights by implementors or users of this specification
The IETF invites any interested party to bring to its attention any
copyrights, patents or patent applications, or other proprietary
rights which may cover technology that may be required to practice
-
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-
this standard. Please address the information to the IETF Executive
Director.
-
-
-
-
-
-
-
-
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