draft-ietf-ldapbis-authmeth-03.txt   draft-ietf-ldapbis-authmeth-04.txt 
Individual Submission R. Harrison, Editor Internet-Draft Editor: R. Harrison
Internet Draft Novell, Inc. Intended Category: Draft Standard Novell, Inc.
Document: draft-ietf-ldapbis-authmeth-03.txt March 1, 2002 Document: draft-ietf-ldapbis-authmeth-04.txt November 2002
Intended Category: Draft Standard Obsoletes: RFC 2829, RFC 2830
LDAP: Authentication Methods LDAP: Authentication Methods
and and
Connection Level Security Mechanisms Connection Level Security Mechanisms
Status of this Memo Status of this Memo
This document is an Internet-Draft and is in full conformance with This document is an Internet-Draft and is in full conformance with
all provisions of Section 10 of RFC2026. all provisions of Section 10 of RFC2026.
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Among the mechanisms described are Among the mechanisms described are
- the LDAPv3 Bind operation used for authenticating LDAP clients - the LDAPv3 Bind operation used for authenticating LDAP clients
to LDAP servers. to LDAP servers.
- the Start TLS operation used to initiate Transport Layer - the Start TLS operation used to initiate Transport Layer
Security on an established connection between an LDAP client and Security on an established connection between an LDAP client and
server. server.
Authentication Methods for LDAPv3 Mar. 1, 2002 Authentication Methods for LDAPv3
- various forms of authentication including anonymous - various forms of authentication including anonymous
authentication, password-based authentication, and certificate authentication, password-based authentication, and certificate
based authentication. based authentication.
1. Conventions Used in this Document 1. Conventions Used in this Document
1.1. Glossary of Terms 1.1. Glossary of Terms
The following terms are used in this document. To aid the reader, The following terms are used in this document. To aid the reader,
these terms are defined here. these terms are defined here.
- "user" represents any application which is an LDAP client using - "user" represents any application which is an LDAP client using
the directory to retrieve or store information. the directory to retrieve or store information.
- "LDAP association" is used to distinguish the LDAP-level - "LDAP association" is used to distinguish the LDAP-level
connection from any underlying TLS-level connection that may or connection from any underlying TLS-level connection that may or
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the formal definition of these terms and concepts is outside the the formal definition of these terms and concepts is outside the
scope of this document, an understanding of them is prerequisite to scope of this document, an understanding of them is prerequisite to
understanding much of the material in this document. Readers who are understanding much of the material in this document. Readers who are
unfamiliar with security-related concepts are encouraged to review unfamiliar with security-related concepts are encouraged to review
Appendix B before reading the remainder of this document. Appendix B before reading the remainder of this document.
1.3. Keywords 1.3. Keywords
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 document are to be interpreted as described in RFC 2119 [RFC2119].
[ReqsKeywords].
2. Introduction 2. Introduction
This document is an integral part of the LDAP Technical This document is an integral part of the LDAP Technical
Specification [ROADMAP]. This document replaces RFC 2829 and RFC Specification [ROADMAP]. This document replaces RFC 2829 and RFC
2830. Changes to RFC 2829 are summarized in Appendix C and changes 2830. Changes to RFC 2829 are summarized in Appendix C and changes
to RFC 2830 are summared in Appendix D. to RFC 2830 are summarized in Appendix D.
LDAPv3 is a powerful access protocol for directories. It offers LDAPv3 is a powerful access protocol for directories. It offers
means of searching, fetching and manipulating directory content, and means of searching, fetching and manipulating directory content, and
ways to access a rich set of security functions. ways to access a rich set of security functions.
It is vital that these security functions be interoperable among all It is vital that these security functions be interoperable among all
LDAP clients and servers on the Internet; therefore there has to be LDAP clients and servers on the Internet; therefore there has to be
a minimum subset of security functions that is common to all a minimum subset of security functions that is common to all
implementations that claim LDAPv3 conformance. implementations that claim LDAPv3 conformance.
Authentication Methods for LDAPv3 Mar. 1, 2002
Basic threats to an LDAP directory service include: Basic threats to an LDAP directory service include:
Authentication Methods for LDAPv3
(1) Unauthorized access to directory data via data-fetching (1) Unauthorized access to directory data via data-fetching
operations, operations,
(2) Unauthorized access to reusable client authentication (2) Unauthorized access to reusable client authentication
information by monitoring others' access, information by monitoring others' access,
(3) Unauthorized access to directory data by monitoring others' (3) Unauthorized access to directory data by monitoring others'
access, access,
(4) Unauthorized modification of directory data, (4) Unauthorized modification of directory data,
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either by modifying data in transit or misdirecting the client's either by modifying data in transit or misdirecting the client's
connection. connection.
Threats (1), (4), (5) and (6) are due to hostile clients. Threats Threats (1), (4), (5) and (6) are due to hostile clients. Threats
(2), (3) and (7) are due to hostile agents on the path between (2), (3) and (7) are due to hostile agents on the path between
client and server or hostile agents posing as a server. client and server or hostile agents posing as a server.
The LDAP protocol suite can be protected with the following security The LDAP protocol suite can be protected with the following security
mechanisms: mechanisms:
(1) Client authentication by means of the SASL [SASL] mechanism set, (1) Client authentication by means of the SASL [RFC2222] mechanism
possibly backed by the TLS [TLS] credentials exchange mechanism, set, possibly backed by the TLS [RFC2246] credentials exchange
mechanism,
(2) Client authorization by means of access control based on the (2) Client authorization by means of access control based on the
requestor's authenticated identity, requestor's authenticated identity,
(3) Data integrity protection by means of the TLS protocol or SASL (3) Data integrity protection by means of the TLS protocol or SASL
mechanisms that provide data integrity services, mechanisms that provide data integrity services,
(4) Data confidentiality protection against snooping by means of the (4) Data confidentiality protection against snooping by means of the
TLS protocol or SASL mechanisms that provide data TLS protocol or SASL mechanisms that provide data
confidentiality services, confidentiality services,
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(5) Server resource usage limitation by means of administrative (5) Server resource usage limitation by means of administrative
service limits configured on the server, and service limits configured on the server, and
(6) Server authentication by means of the TLS protocol or SASL (6) Server authentication by means of the TLS protocol or SASL
mechanism. mechanism.
At the moment, imposition of access controls is done by means At the moment, imposition of access controls is done by means
outside the scope of the LDAP protocol. outside the scope of the LDAP protocol.
3. Required Security Mechanisms 3. Required Security Mechanisms
Authentication Methods for LDAPv3 Mar. 1, 2002 Authentication Methods for LDAPv3
It is clear that allowing any implementation, faced with the above It is clear that allowing any implementation, faced with the above
requirements, to pick and choose among the possible alternatives is requirements, to pick and choose among the possible alternatives is
not a strategy that is likely to lead to interoperability. In the not a strategy that is likely to lead to interoperability. In the
absence of mandates, clients will be written that do not support any absence of mandates, clients will be written that do not support any
security function supported by the server, or worse, support only security function supported by the server, or worse, support only
mechanisms like cleartext passwords that provide clearly inadequate mechanisms like cleartext passwords that provide clearly inadequate
security. security.
Active intermediary attacks are the most difficult for an attacker Active intermediary attacks are the most difficult for an attacker
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authentication services. authentication services.
Therefore, the following implementation conformance requirements are Therefore, the following implementation conformance requirements are
in place: in place:
(1) For a read-only, public directory, anonymous authentication, (1) For a read-only, public directory, anonymous authentication,
described in section 7, can be used. described in section 7, can be used.
(2) Implementations providing password-based authenticated access (2) Implementations providing password-based authenticated access
MUST support authentication using the DIGEST-MD5 SASL mechanism MUST support authentication using the DIGEST-MD5 SASL mechanism
[4], as described in section 8.2. This provides client [RFC2831], as described in section 8.2. This provides client
authentication with protection against passive eavesdropping authentication with protection against passive eavesdropping
attacks, but does not provide protection against active attacks, but does not provide protection against active
intermediary attacks. intermediary attacks.
(3) For a directory needing data security (both data integrity and (3) For a directory needing data security (both data integrity and
data confidentiality) and authentication, the Start TLS data confidentiality) and authentication, the Start TLS
operation described in section 5, and either the simple operation described in section 5, and either the simple
authentication choice or the SASL EXTERNAL mechanism, are to be authentication choice or the SASL EXTERNAL mechanism, are to be
used together. Implementations SHOULD support authentication used together. Implementations SHOULD support authentication
with a password as described in section 8.3, and SHOULD support with a password as described in section 8.3, and SHOULD support
authentication with a certificate as described in section 9.1. authentication with a certificate as described in section 9.1.
Together, these can provide integrity and disclosure protection Together, these can provide integrity and disclosure protection
of transmitted data, and authentication of client and server, of transmitted data, and authentication of client and server,
including protection against active intermediary attacks. including protection against active intermediary attacks.
If TLS is negotiated, the client MUST discard all information about If TLS is negotiated, the client MUST discard all information about
the server fetched prior to the initiation of the TLS negotiation. the server fetched prior to the initiation of the TLS negotiation.
In particular, the value of supportedSASLMechanisms MAY be different In particular, the value of supportedSASLMechanisms MAY be different
Authentication Methods for LDAPv3 Mar. 1, 2002
after TLS has been negotiated (specifically, the EXTERNAL mechanism after TLS has been negotiated (specifically, the EXTERNAL mechanism
Authentication Methods for LDAPv3
or the proposed PLAIN mechanism are likely to only be listed after a or the proposed PLAIN mechanism are likely to only be listed after a
TLS negotiation has been performed). TLS negotiation has been performed).
If a SASL security layer is negotiated, the client MUST discard all If a SASL security layer is negotiated, the client MUST discard all
information about the server fetched prior to the initiation of the information about the server fetched prior to the initiation of the
SASL negotiation. If the client is configured to support multiple SASL negotiation. If the client is configured to support multiple
SASL mechanisms, it SHOULD fetch the supportedSASLmechanisms list SASL mechanisms, it SHOULD fetch the supportedSASLmechanisms list
both before and after the SASL security layer is negotiated. This both before and after the SASL security layer is negotiated. This
allows the client to detect active attacks that remove supported allows the client to detect active attacks that remove supported
SASL mechanisms from the supportedSASLMechanisms list and allows the SASL mechanisms from the supportedSASLMechanisms list and allows the
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security in various circumstances. security in various circumstances.
4. Bind Operation 4. Bind Operation
The Bind operation defined in section 4.2 of [Protocol] allows The Bind operation defined in section 4.2 of [Protocol] allows
authentication information to be exchanged between the client and authentication information to be exchanged between the client and
server. server.
4.1. Unbound Connection Treated as Anonymous 4.1. Unbound Connection Treated as Anonymous
Unlike LDAP v2, the client need not send a Bind Request in the first Unlike LDAP version 2, the client need not send a Bind Request in
PDU of the connection. The client may request any operations and the the first PDU of the connection. The client may request any
server MUST treat these as anonymous. If the server requires that operations and the server MUST treat these as anonymous. If the
the client bind before browsing or modifying the directory, the server requires that the client bind before browsing or modifying
server MAY reject a request other than binding, unbinding or an the directory, the server MAY reject a request other than binding,
extended request with the "operationsError" result. unbinding or an extended request with the "operationsError" result.
4.2. Simple Authentication 4.2. Simple Authentication
The simple authentication option provides minimal authentication The simple authentication option provides minimal authentication
facilities, with the contents of the authentication field consisting facilities, with the contents of the authentication field consisting
only of a cleartext password. Note that the use of cleartext only of a cleartext password. Note that the use of cleartext
passwords is strongly discouraged over open networks when the passwords is strongly discouraged over open networks when the
underlying transport service cannot guarantee confidentiality; see underlying transport service cannot guarantee confidentiality (see
the "Security Considerations" section. section 11).
4.3. SASL Authentication 4.3. SASL Authentication
The sasl choice allows for any mechanism defined for use with SASL The sasl choice allows for any mechanism defined for use with SASL
[RFC2222] not specifically prohibited by this document (see section [RFC2222] not specifically prohibited by this document (see section
4.3.1). 4.3.1).
Authentication Methods for LDAPv3 Mar. 1, 2002
Clients sending a bind request with the sasl choice selected SHOULD Clients sending a bind request with the sasl choice selected SHOULD
NOT send a value in the name field. Servers receiving a bind request NOT send a value in the name field. Servers receiving a bind request
Authentication Methods for LDAPv3
with the sasl choice selected SHALL ignore any value in the name with the sasl choice selected SHALL ignore any value in the name
field. field.
The mechanism field in SaslCredentials contains the name of the The mechanism field in SaslCredentials contains the name of the
mechanism. The credentials field contains the arbitrary data used mechanism. The credentials field contains the arbitrary data used
for authentication, inside an OCTET STRING wrapper. Note that unlike for authentication, inside an OCTET STRING wrapper. Note that unlike
some Internet application protocols where SASL is used, LDAP is not some Internet application protocols where SASL is used, LDAP is not
text-based, thus no Base64 transformations are performed on the text-based, thus no Base64 transformations are performed on the
credentials. credentials.
If any SASL-based integrity or confidentiality services are enabled, If any SASL-based integrity or confidentiality services are enabled,
they take effect following the transmission by the server and they take effect following the transmission by the server and
reception by the client of the final BindResponse with resultCode reception by the client of the final BindResponse with a resultCode
success. of success.
The client can request that the server use authentication The client can request that the server use authentication
information from a lower layer protocol by using the SASL EXTERNAL information from a lower layer protocol by using the SASL EXTERNAL
mechanism (see section 5.5.1.2). mechanism (see section 5.5.1.2).
4.3.1. Use of ANONYMOUS and PLAIN SASL Mechanisms 4.3.1. Use of ANONYMOUS and PLAIN SASL Mechanisms
As LDAP includes native anonymous and plaintext authentication As LDAP includes native anonymous and plaintext authentication
methods, the "ANONYMOUS" and "PLAIN" SASL mechanisms are not used methods, the "ANONYMOUS" and "PLAIN" SASL mechanisms are not used
with LDAP. If an authorization identity of a form different from a with LDAP. If an authorization identity of a form different from a
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4.3.2. Use of EXTERNAL SASL Mechanism 4.3.2. Use of EXTERNAL SASL Mechanism
The "EXTERNAL" SASL mechanism can be used to request the LDAP server The "EXTERNAL" SASL mechanism can be used to request the LDAP server
make use of security credentials exchanged by a lower layer. If a make use of security credentials exchanged by a lower layer. If a
TLS session has not been established between the client and server TLS session has not been established between the client and server
prior to making the SASL EXTERNAL Bind request and there is no other prior to making the SASL EXTERNAL Bind request and there is no other
external source of authentication credentials (e.g. IP-level external source of authentication credentials (e.g. IP-level
security [RFC2401]), or if, during the process of establishing the security [RFC2401]), or if, during the process of establishing the
TLS session, the server did not request the client's authentication TLS session, the server did not request the client's authentication
credentials, the SASL EXTERNAL bind MUST fail with a result code of credentials, the SASL EXTERNAL bind MUST fail with a resultCode of
inappropriateAuthentication. Any client authentication and inappropriateAuthentication. Any client authentication and
authorization state of the LDAP association is lost, so the LDAP authorization state of the LDAP association is lost, so the LDAP
association is in an anonymous state after the failure. association is in an anonymous state after the failure.
4.3.3. SASL Mechanisms not Considered in this Document 4.3.3. SASL Mechanisms not Considered in this Document
The following SASL-based mechanisms are not considered in this The following SASL-based mechanisms are not considered in this
document: KERBEROS_V4, GSSAPI and SKEY. document: KERBEROS_V4, GSSAPI and SKEY.
4.4. SASL Authorization Identity 4.4. SASL Authorization Identity
The authorization identity is carried as part of the SASL The authorization identity is carried as part of the SaslCredentials
credentials field in the LDAP Bind request and response. credentials field in the Bind request and response.
Authentication Methods for LDAPv3 Mar. 1, 2002
When the "EXTERNAL" SASL mechanism is being negotiated, if the When the "EXTERNAL" SASL mechanism is being negotiated, if the
credentials field is present, it contains an authorization identity credentials field is present, it contains an authorization identity
of the authzId form described below. of the authzId form described below.
Authentication Methods for LDAPv3
Other mechanisms define the location of the authorization identity Other mechanisms define the location of the authorization identity
in the credentials field. in the credentials field.
4.4.1. Authorization Identity Syntax 4.4.1. Authorization Identity Syntax
The authorization identity is a string in the UTF-8 character set, The authorization identity is a string in the UTF-8 character set,
corresponding to the following ABNF grammar [ABNF]: corresponding to the following ABNF grammar [RFC2234]:
; Specific predefined authorization (authz) id schemes are ; Specific predefined authorization (authz) id schemes are
; defined below -- new schemes may be defined in the future. ; defined below -- new schemes may be defined in the future.
authzId = dnAuthzId / uAuthzId authzId = dnAuthzId / uAuthzId
DNCOLON = %x64 %x6e %x3a ; "dn:"
UCOLON = %x75 %x3a ; "u:"
; distinguished-name-based authz id. ; distinguished-name-based authz id.
dnAuthzId = "dn:" dn dnAuthzId = DNCOLON dn
dn = utf8string ; with syntax defined in [LDAPDN] section 3. dn = utf8string ; with syntax defined in [LDAPDN] section 3.
; unspecified authorization id, UTF-8 encoded. ; unspecified authorization id, UTF-8 encoded.
uAuthzId = "u:" userid uAuthzId = UCOLON userid
userid = utf8string ; syntax unspecified userid = utf8string ; syntax unspecified
4.4.1.1. DN-based Authorization Identity 4.4.1.1. DN-based Authorization Identity
All servers that support the storage of authentication credentials, All servers that support the storage of authentication credentials,
such as passwords or certificates, in the directory MUST support the such as passwords or certificates, in the directory MUST support the
dnAuthzId choice. The format for distinguishedName is defined in dnAuthzId choice. The format for distinguishedName is defined in
section 3 of [LDAPDN]. section 3 of [LDAPDN].
4.4.1.2. Unspecified Authorization Identity 4.4.1.2. Unspecified Authorization Identity
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For example, the userid could identify a user of a specific For example, the userid could identify a user of a specific
directory service, or be a login name or the local-part of an RFC directory service, or be a login name or the local-part of an RFC
822 email address. In general a uAuthzId MUST NOT be assumed to be 822 email address. In general a uAuthzId MUST NOT be assumed to be
globally unique. globally unique.
Additional authorization identity schemes MAY be defined in future Additional authorization identity schemes MAY be defined in future
versions of this document. versions of this document.
4.5. SASL Service Name for LDAP 4.5. SASL Service Name for LDAP
Authentication Methods for LDAPv3 Mar. 1, 2002 Authentication Methods for LDAPv3
For use with SASL [SASL], a protocol must specify a service name to For use with SASL [RFC2222], a protocol must specify a service name
be used with various SASL mechanisms, such as GSSAPI. For LDAP, the to be used with various SASL mechanisms, such as GSSAPI. For LDAP,
service name is "ldap", which has been registered with the IANA as a the service name is "ldap", which has been registered with the IANA
GSSAPI service name. as a GSSAPI service name.
4.6. SASL Integrity and Privacy Protections 4.6. SASL Integrity and Privacy Protections
Any negotiated SASL integrity and privacy protections SHALL start on Any negotiated SASL integrity and privacy protections SHALL start on
the first octet of the first LDAP PDU following successful the first octet of the first LDAP PDU following successful
completion of the SASL bind operation. If lower level security layer completion of the SASL bind operation. If lower level security layer
is negotiated, such as TLS, any SASL security services SHALL be is negotiated, such as TLS, any SASL security services SHALL be
layered on top of such security layers regardless of the order of layered on top of such security layers regardless of the order of
their negotiation. their negotiation.
5. Start TLS Operation 5. Start TLS Operation
The Start Transport Layer Security (StartTLS) operation provides the The Start Transport Layer Security (StartTLS) operation defined in
ability to establish Transport Layer Security [TLS] on an LDAP section x.x of [Protocol] provides the ability to establish
association. Transport Layer Security [RFC2246] on an LDAP association.
5.1. Start TLS Request
A client requests TLS establishment by transmitting a Start TLS
request PDU to the server. The Start TLS request is defined in terms
of the [Protocol] ExtendedRequest as follows:
ExtendedRequest ::= [APPLICATION 23] SEQUENCE {
requestName [0] LDAPOID,
requestValue [1] OCTET STRING OPTIONAL }
The requestName portion of the Start TLS request MUST be the OID
"1.3.6.1.4.1.1466.20037".
The requestValue field is absent.
The client MUST NOT send any PDUs on this connection following this
request until it receives a Start TLS extended response.
5.2. Start TLS Response
When a Start TLS request is made, the server MUST return a Start TLS
response PDU to the requestor. The Start TLS response id defined in
terms of the [Protocol] ExtendedResponse as follows:
ExtendedResponse ::= [APPLICATION 24] SEQUENCE {
COMPONENTS OF LDAPResult,
responseName [10] LDAPOID OPTIONAL,
response [11] OCTET STRING OPTIONAL }
The responseName portion of the Start TLS response MUST be the OID
"1.3.6.1.4.1.1466.20037". (Note that this OID is the same OID value
used in the requestName of the Start TLS request.)
Authentication Methods for LDAPv3 Mar. 1, 2002
The response field is absent.
The server MUST set the resultCode field to either success or one of
the other values outlined in section 5.2.2.
5.2.1. "Success" Response
If the ExtendedResponse contains a resultCode of success, this
indicates that the server is willing and able to negotiate TLS.
Refer to section 5.3, below, for details.
5.2.2. Response other than "success"
If the ExtendedResponse contains a resultCode other than success,
this indicates that the server is unwilling or unable to negotiate
TLS.
If the Start TLS extended request was not successful, the resultCode
will be one of:
operationsError (operations sequencing incorrect; e.g. TLS already
established)
protocolError (TLS not supported or incorrect PDU structure)
referral (this server doesn't do TLS, try this one)
unavailable (e.g. some major problem with TLS, or server is
shutting down)
The server MUST return operationsError if the client violates any of
the Start TLS extended operation sequencing requirements described
in section 5.3, below.
If the server does not support TLS (whether by design or by current
configuration), it MUST set the resultCode to protocolError (see
section 4.1.1 of [Protocol]), or to referral. The server MUST
include an actual referral value in the LDAP Result if it returns a
resultCode of referral. The client's current session is unaffected
if the server does not support TLS. The client MAY proceed with any
LDAP operation, or it MAY close the connection.
The server MUST return unavailable if it supports TLS but
cannot establish a TLS connection for some reason, e.g. the
certificate server not responding, it cannot contact its TLS
implementation, or if the server is in process of shutting
down. The client MAY retry the StartTLS operation, or it MAY
proceed with any other LDAP operation, or it MAY close the
connection.
5.3. Sequencing of the Start TLS Operation 5.1. Sequencing of the Start TLS Operation
Authentication Methods for LDAPv3 Mar. 1, 2002
This section describes the overall procedures clients and servers This section describes the overall procedures clients and servers
MUST follow for TLS establishment. These procedures take into MUST follow for TLS establishment. These procedures take into
consideration various aspects of the overall security of the LDAP consideration various aspects of the overall security of the LDAP
association including discovery of resultant security level and association including discovery of resultant security level and
assertion of the client's authorization identity. assertion of the client's authorization identity.
Note that the precise effects, on a 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 of establishing TLS on an LDAP association are described in detail
in section 5.5. in section 5.5.
5.3.1. Requesting to Start TLS on an LDAP Association 5.1.1. Requesting to Start TLS on an LDAP Association
The client MAY send the Start TLS extended request at any time after The client MAY send the Start TLS extended request at any time after
establishing an LDAP association, except that in the following cases establishing an LDAP association, except that in the following cases
the client MUST NOT send a Start TLS extended request: the client MUST NOT send a Start TLS extended request:
- if TLS is currently established on the connection, or - if TLS is currently established on the connection, or
- during a multi-stage SASL negotiation, or - during a multi-stage SASL negotiation, or
- if there are any LDAP operations outstanding on the - if there are any LDAP operations outstanding on the
connection. connection.
The result of violating any of these requirements is a resultCode of The result of violating any of these requirements is a resultCode of
operationsError, as described above in section 5.2.2. operationsError, as described above in section 5.2.2.
The client MAY have already performed a Bind operation when it sends In particular, there is no requirement that the client have or have
a Start TLS request, or the client might have not yet bound. 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 If the client did not establish a TLS connection before sending any
other requests, and the server requires the client to establish a other requests, and the server requires the client to establish a
Authentication Methods for LDAPv3
TLS connection before performing a particular request, the server TLS connection before performing a particular request, the server
MUST reject that request with a confidentialityRequired or MUST reject that request with a confidentialityRequired or
strongAuthRequired result. The client MAY send a Start TLS extended strongAuthRequired result. The client MAY send a Start TLS extended
request, or it MAY choose to close the connection. request, or it MAY choose to close the connection.
5.3.2. Starting TLS 5.1.2. Starting TLS
The server will return an extended response with the resultCode of The server will return an extended response with the resultCode of
success if it is willing and able to negotiate TLS. It will return success if it is willing and able to negotiate TLS. It will return
other resultCodes, documented above, if it is unable. other resultCodes, documented above, if it is unable.
In the successful case, the client, which has ceased to transfer In the successful case, the client, which has ceased to transfer
LDAP requests on the connection, MUST either begin a TLS negotiation LDAP requests on the connection, MUST either begin a TLS negotiation
or close the connection. The client will send PDUs in the TLS Record or close the connection. The client will send PDUs in the TLS Record
Protocol directly over the underlying transport connection to the Protocol directly over the underlying transport connection to the
server to initiate TLS negotiation [TLS]. server to initiate TLS negotiation [RFC2246].
5.3.3. TLS Version Negotiation 5.1.3. TLS Version Negotiation
Negotiating the version of TLS or SSL to be used is a part of the Negotiating the version of TLS or SSL to be used is a part of the
TLS Handshake Protocol, as documented in [TLS]. Please refer to that TLS Handshake Protocol, as documented in [RFC2246]. Please refer to
document for details. that document for details.
5.3.4. Discovery of Resultant Security Level 5.1.4. Discovery of Resultant Security Level
Authentication Methods for LDAPv3 Mar. 1, 2002
After a TLS connection is established on an LDAP association, both After a TLS connection is established on an LDAP association, both
parties MUST individually decide whether or not to continue based on parties MUST individually decide whether or not to continue based on
the privacy level achieved. Ascertaining the TLS connection's the privacy level achieved. Ascertaining the TLS connection's
privacy level is implementation dependent, and accomplished by privacy level is implementation dependent, and accomplished by
communicating with one's respective local TLS implementation. communicating with one's respective local TLS implementation.
If the client or server decides that the level of authentication or If the client or server decides that the level of authentication or
privacy is not high enough for it to continue, it SHOULD gracefully privacy is not high enough for it to continue, it SHOULD gracefully
close the TLS connection immediately after the TLS negotiation has close the TLS connection immediately after the TLS negotiation has
completed (see sections 5.4.1 and 5.5.2 below). If the client completed (see sections 5.4.1 and 5.5.2 below). If the client
decides to continue, it MAY attempt to Start TLS again, it MAY send decides to continue, it MAY attempt to Start TLS again, it MAY send
an unbind request, or it MAY send any other LDAP request. an unbind request, or it MAY send any other LDAP request.
5.3.5. Assertion of Client's Authorization Identity 5.1.5. Assertion of Client's Authorization Identity
The client MAY, upon receipt of a Start TLS response indicating The client MAY, upon receipt of a Start TLS response indicating
success, assert that a specific authorization identity be utilized success, assert that a specific authorization identity be utilized
in determining the client's authorization status. The client in determining the client's authorization status. The client
accomplishes this via an LDAP Bind request specifying a SASL accomplishes this via an LDAP Bind request specifying a SASL
mechanism of "EXTERNAL" [SASL] (see section 5.5.1.2 below). mechanism of "EXTERNAL" [RFC2222] (see section 5.5.1.2 below).
5.3.6. Server Identity Check 5.1.6. Server Identity Check
The client MUST check its understanding of the server's hostname The client MUST check its understanding of the server's hostname
against the server's identity as presented in the server's against the server's identity as presented in the server's
Certificate message, in order to prevent man-in-the-middle attacks. Certificate message, in order to prevent man-in-the-middle attacks.
Matching is performed according to these rules: Matching is performed according to these rules:
Authentication Methods for LDAPv3
- The client MUST use the server hostname it used to open the LDAP - The client MUST use the server hostname it used to open the LDAP
connection as the value to compare against the server name as connection as the value to compare against the server name as
expressed in the server's certificate. The client MUST NOT use expressed in the server's certificate. The client MUST NOT use
the server's canonical DNS name or any other derived form of the server's canonical DNS name or any other derived form of
name. name.
- If a subjectAltName extension of type dNSName is present in the - If a subjectAltName extension of type dNSName is present in the
certificate, it SHOULD be used as the source of the server's certificate, it SHOULD be used as the source of the server's
identity. identity.
skipping to change at page 12, line 4 skipping to change at page 10, line 30
only to the left-most name component. only to the left-most name component.
For example, *.bar.com would match a.bar.com and b.bar.com, but it 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 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 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 (e.g. more than one dNSName name), a match in any one of the set is
considered acceptable. considered acceptable.
If the hostname does not match the dNSName-based identity in the If the hostname does not match the dNSName-based identity in the
certificate per the above check, user-oriented clients SHOULD either certificate per the above check, user-oriented clients SHOULD either
Authentication Methods for LDAPv3 Mar. 1, 2002
notify the user (clients MAY give the user the opportunity to notify the user (clients MAY give the user the opportunity to
continue with the connection in any case) or terminate the continue with the connection in any case) or terminate the
connection and indicate that the server's identity is suspect. connection and indicate that the server's identity is suspect.
Automated clients SHOULD close the connection, returning and/or Automated clients SHOULD close the connection, returning and/or
logging an error indicating that the server's identity is suspect. logging an error indicating that the server's identity is suspect.
Beyond the server identity checks described in this section, clients Beyond the server identity checks described in this section, clients
SHOULD be prepared to do further checking to ensure that the server SHOULD be prepared to do further checking to ensure that the server
is authorized to provide the service it is observed to provide. The is authorized to provide the service it is observed to provide. The
client MAY need to make use of local policy information. client MAY need to make use of local policy information.
5.3.7. Refresh of Server Capabilities Information 5.1.7. Refresh of Server Capabilities Information
The client MUST refresh any cached server capabilities information The client MUST refresh any cached server capabilities information
(e.g. from the server's root DSE; see section 3.4 of [Protocol]) (e.g. from the server's root DSE; see section 3.4 of [Protocol])
upon TLS session establishment. This is necessary to protect against upon TLS session establishment. This is necessary to protect against
active-intermediary attacks that may have altered any server active-intermediary attacks that may have altered any server
capabilities information retrieved prior to TLS establishment. The capabilities information retrieved prior to TLS establishment. The
server MAY advertise different capabilities after TLS establishment. server MAY advertise different capabilities after TLS establishment.
5.4. Closing a TLS Connection 5.2. Effects of TLS on a Client's Authorization Identity
Two forms of TLS connection closure--graceful and abrupt--are
supported.
5.4.1. Graceful Closure
Either the client or server MAY terminate the TLS connection on an
LDAP association by sending a TLS closure alert. This will leave the
LDAP association intact.
Before closing a TLS connection, the client MUST [RGH9]either wait
for any outstanding LDAP operations to complete, or explicitly
abandon them [Protocol].
After the initiator of a close has sent a TLS closure alert, it MUST
discard any TLS messages until it has received a TLS closure alert
from the other party. It will cease to send TLS Record Protocol
PDUs, and following the receipt of the alert, MAY send and receive
LDAP PDUs.
The other party, if it receives a TLS closure alert, MUST
immediately transmit a TLS closure alert. It will subsequently
cease to send TLS Record Protocol PDUs, and MAY send and receive
LDAP PDUs.
5.4.2. Abrupt Closure
Either the client or server MAY abruptly close the entire LDAP
association and any TLS connection established on it by dropping the
underlying TCP connection. In this circumstance, a server MAY send
the client a Notice of Disconnection [Protocol] before dropping the
TCP connection.
Authentication Methods for LDAPv3 Mar. 1, 2002
5.5. Effects of TLS on a Client's Authorization Identity
This section describes the effects on a client's authorization This section describes the effects on a client's authorization
identity brought about by establishing TLS on an LDAP association. identity brought about by establishing TLS on an LDAP association.
The default effects are described first, and next the facilities for The default effects are described first, and next the facilities for
client assertion of authorization identity are discussed including client assertion of authorization identity are discussed including
error conditions. Lastly, the effects of closing the TLS connection error conditions. Lastly, the effects of closing the TLS connection
are described. are described.
Authorization identities and related concepts are described in Authorization identities and related concepts are described in
Appendix B. Appendix B.
5.5.1. TLS Connection Establishment Effects Authentication Methods for LDAPv3
5.5.1.1. Default Effects 5.2.1 TLS Connection Establishment Effects
5.2.1.1. Default Effects
Upon establishment of the TLS connection onto the LDAP association, Upon establishment of the TLS connection onto the LDAP association,
any previously established authentication and authorization any previously established authentication and authorization
identities MUST remain in force, including anonymous state. This identities MUST remain in force, including anonymous state. This
holds even in the case where the server requests client holds even in the case where the server requests client
authentication via TLS -- e.g. requests the client to supply its authentication via TLS -- e.g. requests the client to supply its
certificate during TLS negotiation (see [TLS]). certificate during TLS negotiation (see [RFC2246]).
5.5.1.2. Client Assertion of Authorization Identity 5.2.1.2. Client Assertion of Authorization Identity
A client MAY either implicitly request that its LDAP authorization A client MAY either implicitly request that its LDAP authorization
identity be derived from its authenticated TLS credentials or it MAY identity be derived from its authenticated TLS credentials or it MAY
explicitly provide an authorization identity and assert that it be explicitly provide an authorization identity and assert that it be
used in combination with its authenticated TLS credentials. The used in combination with its authenticated TLS credentials. The
former is known as an implicit assertion, and the latter as an former is known as an implicit assertion, and the latter as an
explicit assertion. explicit assertion.
5.5.1.2.1. Implicit Assertion 5.2.1.2.1. Implicit Assertion
An implicit authorization identity assertion is accomplished after An implicit authorization identity assertion is accomplished after
TLS establishment by invoking a Bind request of the SASL form using TLS establishment by invoking a Bind request of the SASL form using
the "EXTERNAL" mechanism name [SASL, LDAPv3] that SHALL NOT include the "EXTERNAL" mechanism name [RFC2222] [Protocol] that SHALL NOT
the optional credentials octet string (found within the include the optional credentials octet string (found within the
SaslCredentials sequence in the Bind Request). The server will SaslCredentials sequence in the Bind Request). The server will
derive the client's authorization identity from the authentication derive the client's authorization identity from the authentication
identity supplied in the client's TLS credentials (typically a identity supplied in the client's TLS credentials (typically a
public key certificate) according to local policy. The underlying public key certificate) according to local policy. The underlying
mechanics of how this is accomplished are implementation specific. mechanics of how this is accomplished are implementation specific.
5.5.1.2.2. Explicit Assertion 5.2.1.2.2. Explicit Assertion
An explicit authorization identity assertion is accomplished after An explicit authorization identity assertion is accomplished after
TLS establishment by invoking a Bind request of the SASL form using TLS establishment by invoking a Bind request of the SASL form using
the "EXTERNAL" mechanism name [SASL, LDAPv3] that SHALL include the the "EXTERNAL" mechanism name [RFC2222] [Protocol] that SHALL
credentials octet string. This string MUST be constructed as include the credentials octet string. This string MUST be
documented in section 4.5. constructed as documented in section 4.4.1.
Authentication Methods for LDAPv3 Mar. 1, 2002
5.5.1.2.3. Error Conditions 5.2.1.2.3. Error Conditions
For either form of assertion, the server MUST verify that the For either form of assertion, the server MUST verify that the
client's authentication identity as supplied in its TLS credentials client's authentication identity as supplied in its TLS credentials
is permitted to be mapped to the asserted authorization identity. is permitted to be mapped to the asserted authorization identity.
The server MUST reject the Bind operation with an invalidCredentials The server MUST reject the Bind operation with an invalidCredentials
resultCode in the Bind response if the client is not so authorized. resultCode in the Bind response if the client is not so authorized.
Additionally, with either form of assertion, if a TLS session has Additionally, with either form of assertion, if a TLS session has
not been established between the client and server prior to making not been established between the client and server prior to making
the SASL EXTERNAL Bind request and there is no other external source the SASL EXTERNAL Bind request and there is no other external source
of authentication credentials (e.g. IP-level security [IPSEC]), or of authentication credentials (e.g. IP-level security [RFC2401]), or
if, during the process of establishing the TLS session, the server if, during the process of establishing the TLS session, the server
Authentication Methods for LDAPv3
did not request the client's authentication credentials, the SASL did not request the client's authentication credentials, the SASL
EXTERNAL bind MUST fail with a result code of EXTERNAL bind MUST fail with a result code of
inappropriateAuthentication. inappropriateAuthentication.
After the above Bind operation failures, any client authentication After the above Bind operation failures, any client authentication
and authorization state of the LDAP association is lost, so the LDAP and authorization state of the LDAP association is lost, so the LDAP
association is in an anonymous state after the failure. TLS association is in an anonymous state after the failure. TLS
connection state is unaffected, though a server MAY end the TLS connection state is unaffected, though a server MAY end the TLS
connection, via a TLS close_notify message, based on the Bind connection, via a TLS close_notify message, based on the Bind
failure (as it MAY at any time). failure (as it MAY at any time).
5.5.2. TLS Connection Closure Effects 5.2.2. TLS Connection Closure Effects
Closure of the TLS connection MUST cause the LDAP association to Closure of the TLS connection MUST cause the LDAP association to
move to an anonymous authentication and authorization state move to an anonymous authentication and authorization state
regardless of the state established over TLS and regardless of the regardless of the state established over TLS and regardless of the
authentication and authorization state prior to TLS connection authentication and authorization state prior to TLS connection
establishment. establishment.
6. LDAP Association State Transition Tables 6. LDAP Association State Transition Tables
To comprehensively diagram the various authentication and TLS states To comprehensively diagram the various authentication and TLS states through which
through which an LDAP association may pass, this section provides a an LDAP association may pass, this section provides a state transition table to
state transition table to represent a state diagram for the various represent a state diagram for the various states through which an LDAP association
states through which an LDAP association may pass during the course may pass during the course of its existence and the actions that cause these
of its existence and the actions that cause these changes in state. changes in state.
6.1. LDAP Association States 6.1. LDAP Association States
The following table lists the valid LDAP association states and The following table lists the valid LDAP association states and provides a
provides a description of each state. The ID for each state is used description of each state. The ID for each state is used in the state transition
in the state transition table in section 6.4. table in section 6.4.
ID State Description ID State Description
-- -------------------------------------------------------------- -- --------------------------------------------------------------
S1 no Auth ID S1 no Auth ID
no AuthZ ID no AuthZ ID
TLS: no Creds OFF [TLS: no Creds, OFF]
S2 no Auth ID S2 no Auth ID
Authentication Methods for LDAPv3 Mar. 1, 2002
no AuthZ ID no AuthZ ID
TLS: no Creds ON [TLS: no Creds, ON]
S3 no Auth ID S3 no Auth ID
no AuthZ ID no AuthZ ID
TLS: Creds Auth ID "I", ON. [TLS: Creds Auth ID "I", ON]
S4 Auth ID = Xn S4 Auth ID = Xn
AuthZ ID= Yn AuthZ ID= Yn
[TLS: no Creds, Off] [TLS: no Creds, OFF]
S5 Auth ID = Xn S5 Auth ID = Xn
AuthZ ID= Yn AuthZ ID= Yn
[TLS: no Creds, On] [TLS: no Creds, ON]
S6 Auth ID = Xn S6 Auth ID = Xn
AuthZ ID= Yn AuthZ ID= Yn
[TLS: Creds Auth ID "I", On] [TLS: Creds Auth ID "I", ON]
Authentication Methods for LDAPv3
S7 Auth ID = I S7 Auth ID = I
AuthZ ID= Jn AuthZ ID= J
[TLS: Creds Auth ID "I", On] [TLS: Creds Auth ID "I", ON]
S8 Auth ID = I S8 Auth ID = I
AuthZ ID= is based on "I" AuthZ ID= K
[TLS: Creds Auth ID "I", On] [TLS: Creds Auth ID "I", ON]
6.2. Actions that Affect LDAP Association State 6.2. Actions that Affect LDAP Association State
The following table lists the actions that can affect the state of The following table lists the actions that can affect the state of an LDAP
an LDAP association. The ID for each action is used in the state association. The ID for each action is used in the state transition table in
transition table in section 6.4. section 6.4.
ID Action ID Action
-- ------------------------------------------------ -- ------------------------------------------------
A1 Client binds anonymously A1 Client binds anonymously
A2 Error: Inappropriate authentication A2 Inappropriate authentication: client attempts an anonymous bind or a bind
A3 Client or Server: close TLS connection (section 5.5.2) without supplying credentials to a server that requires the client to
A4 Client StartTLS provide some form of credentials.
A3 Client Start TLS request
Server: client auth NOT required Server: client auth NOT required
A4 Client: Start TLS request
A5 Client: StartTLS
Server: client creds requested Server: client creds requested
Client: {TLS creds: Auth ID "I"] Client: [TLS creds: Auth ID "I"]
A6 Client: Bind w/simple password or SASL mechanism (e.g. DIGEST- A5 Client or Server: send TLS closure alert ([Protocol] section X)
MD5 password, Kerberos, etc. - except EXTERNAL [Auth ID "X" A6 Client: Bind w/simple password or SASL mechanism (e.g. DIGEST-MD5 password,
maps to AuthZ ID "Y"] Kerberos, etc. --
A7 Client Binds SASL EXTERNAL w/ credentials: AuthZ ID "J" - except EXTERNAL [Auth ID "X" maps to AuthZ ID "Y"]
[Explicit Assertion (section 5.5.1.2.2)] A7 Client Binds SASL EXTERNAL with credentials: AuthZ ID "J" [Explicit
A8 Client Bind SASL EXTERNAL w/saslcredentials: NULL [Implicit Assertion (section 5.2.1.2.2)]
Assertion (section 5.5.1.2.1)] A8 Client Bind SASL EXTERNAL without credentials [Implicit Assertion (section
5.2 .1.2.1)]
6.3. Decisions Used in Making LDAP Association State Changes 6.3. Decisions Used in Making LDAP Association State Changes
Certain changes in the state of an LDAP association are only allowed Certain changes in the state of an LDAP association are only allowed if the server
if the server can affirmatively answer a question. These questions can affirmatively answer a question. These questions are applied as part of the
are applied as part of the criteria for allowing or disallowing a criteria for allowing or disallowing a state change in the state transition table
state change in the state transition table in section 6.4. in section 6.4.
Authentication Methods for LDAPv3 Mar. 1, 2002
ID Decision Question ID Decision Question
-- -------------------------------------------------------------- -- --------------------------------------------------------------
D1 Can TLS Credentials Auth ID "I" be mapped to AuthZ ID "J"? D1 Can TLS Credentials Auth ID "I" be mapped to AuthZ ID "J"?
D2 Can a valid AuthZ ID "J" be derived from TLS Credentials Auth D2 Can a valid AuthZ ID "K" be derived from TLS Credentials Auth ID "I"?
ID "I"?
6.4. LDAP Association State Transition Table 6.4. LDAP Association State Transition Table
The LDAP Association table below lists the valid states for an LDAP The LDAP Association table below lists the valid states for an LDAP association
association and the actions that could affect them. For any given and the actions that could affect them. For any given row in the table, the
row in the table, the Current State column gives the state of an Current State column gives the state of an LDAP association, the Action column
LDAP association, the Action column gives an action that could gives an action that could affect the state of an LDAP assocation, and the Next
affect the state of an LDAP assocation, and the Next State column State column gives the resulting state of an LDAP association after the action
gives the resulting state of an LDAP association after the action
occurs. occurs.
The initial state for the state machine described in this table is Authentication Methods for LDAPv3
S1.
The initial state for the state machine described in this table is S1.
Current Next Current Next
State Action State Comment State Action State Comment
------- ------------- ----- ----------------------------------- ------- ------------- ----- -----------------------------------
S1 A1 S1 S1 A1 S1
S1 A2 S1 Error: Inappropriate authentication S1 A2 S1 Error: Inappropriate authentication
S1 A4 S2 S1 A3 S2
S1 A5 S3 S1 A4 S3
S1 A6 S4 S1 A6 S4
S1 A7 ? identity could be provided by another
underlying mechanism such as IPSec.
S1 A8 ? identity could be provided by another
underlying mechanism such as IPSec.
S2 A1 S2 S2 A1 S2
S2 A2 S2 Error: Inappropriate authentication S2 A2 S2 Error: Inappropriate authentication
S2 A3 S1 S2 A5 S1
S2 A6 S5 S2 A6 S5
S2 A7 ? identity could be provided by another
underlying mechanism such as IPSec.
S2 A8 ? identity could be provided by another
underlying mechanism such as IPSec.
S3 A1 S3 S3 A1 S3
S3 A3 S1 S3 A2 S3 Error: Inappropriate authentication
S3 A5 S1
S3 A6 S6 S3 A6 S6
S3 A7 and D1=NO S3 Error: InvalidCredentials S3 A7 and D1=NO S3 Error: InvalidCredentials
S3 A7 and D1=YES S7 S3 A7 and D1=YES S7
S3 A8 and D2=NO S3 Error: InvalidCredentials S3 A8 and D2=NO S3 Error: InvalidCredentials
S3 A8 and D2=YES S8 S3 A8 and D2=YES S8
S4 A6 S4 S4 A1 S1
S4 A2 S4 Error: Inappropriate Authentication S4 A2 S4 Error: Inappropriate Authentication
S4 A3 S1 S4 A3 S5
S4 A4 S5 S4 A4 S6
S4 A5 S6 S4 A5 S1
S5 A6 S5 S4 A6 S4
S5 A2 S5 Error: Inappropriate Authentication S4 A7 ? identity could be provided by another
S5 A3 S1 underlying mechanism such as IPSec.
S4 A8 ? identity could be provided by another
underlying mechanism such as IPSec.
S5 A1 S2 S5 A1 S2
S6 A6 S6 S5 A2 S5 Error: Inappropriate Authentication
S6 A3 S1 S5 A5 S1
S5 A6 S5
S5 A7 ? identity could be provided by another
underlying mechanism such as IPSec.
S5 A8 ? identity could be provided by another
underlying mechanism such as IPSec.
S6 A1 S3 S6 A1 S3
Authentication Methods for LDAPv3 Mar. 1, 2002 S6 A2 S6 Error: Inappropriate Authentication
S6 A5 S1
Authentication Methods for LDAPv3
S6 A6 S6
S6 A7 and D1=NO S6 Error: InvalidCredentials S6 A7 and D1=NO S6 Error: InvalidCredentials
S6 A7 and D1=YES S10 S6 A7 and D1=YES S10
S6 A8 and D2=NO S6 Error: InvalidCredentials S6 A8 and D2=NO S6 Error: InvalidCredentials
S6 A8 and D2=YES S8 S6 A8 and D2=YES S8
S7 A1 S3 S7 A1 S3
S7 A3 S1 S7 A2 S7 Error: Inappropriate Authentication
S7 A5 S1
S7 A6 S6 S7 A6 S6
S7 A7 S7 S7 A7 S7
S7 A8 and D2=NO S3 Error: InvalidCredentials S7 A8 and D2=NO S3 Error: InvalidCredentials
S7 A8 and D2=YES S8 S7 A8 and D2=YES S8
S8 A1 S3 S8 A1 S3
S8 A3 S1 S8 A2 S8 Error: Inappropriate Authentication
S8 A8 S8 S8 A5 S1
S8 A6 S6
S8 A7 and D1=NO S6 Error: InvalidCredentials S8 A7 and D1=NO S6 Error: InvalidCredentials
S8 A7 and D1=YES S7 S8 A7 and D1=YES S7
S8 A6 S6 S8 A8 S8
7. Anonymous Authentication 7. Anonymous Authentication
Directory operations that modify entries or access protected Directory operations that modify entries or access protected
attributes or entries generally require client authentication. attributes or entries generally require client authentication.
Clients that do not intend to perform any of these operations Clients that do not intend to perform any of these operations
typically use anonymous authentication. Servers SHOULD NOT allow typically use anonymous authentication. Servers SHOULD NOT allow
clients with anonymous authentication to modify directory entries or clients with anonymous authentication to modify directory entries or
access sensitive information in directory entries. access sensitive information in directory entries.
skipping to change at page 17, line 55 skipping to change at page 16, line 4
to anonymously authenticated clients. to anonymously authenticated clients.
7.1. Anonymous Authentication Procedure 7.1. Anonymous Authentication Procedure
An LDAPv3 client that has not successfully completed a bind An LDAPv3 client that has not successfully completed a bind
operation on a connection is anonymously authenticated. See section operation on a connection is anonymously authenticated. See section
4.3.3. 4.3.3.
An LDAP client MAY also choose to explicitly bind anonymously. A An LDAP client MAY also choose to explicitly bind anonymously. A
client that wishes to do so MUST choose the simple authentication client that wishes to do so MUST choose the simple authentication
option in the Bind Request (see section 4.1) and set the password to Authentication Methods for LDAPv3
Authentication Methods for LDAPv3 Mar. 1, 2002
option in the Bind Request (see section 4.1) and set the password to
be of zero length. (This is often done by LDAPv2 clients.) Typically be of zero length. (This is often done by LDAPv2 clients.) Typically
the name is also of zero length. the name is also of zero length.
7.2. Anonymous Authentication and TLS 7.2. Anonymous Authentication and TLS
An LDAP client MAY use the Start TLS operation (section 5) to An LDAP client MAY use the Start TLS operation (section 5) to
negotiate the use of TLS security [TLS]. If the client has not bound negotiate the use of TLS security [RFC2246]. If the client has not
beforehand, then until the client uses the EXTERNAL SASL mechanism bound beforehand, then until the client uses the EXTERNAL SASL
to negotiate the recognition of the client's certificate, the client mechanism to negotiate the recognition of the client's certificate,
is anonymously authenticated. the client is anonymously authenticated.
Recommendations on TLS ciphersuites are given in section 11. Recommendations on TLS ciphersuites are given in section 11.
An LDAP server which requests that clients provide their certificate An LDAP server which requests that clients provide their certificate
during TLS negotiation MAY use a local security policy to determine during TLS negotiation MAY use a local security policy to determine
whether to successfully complete TLS negotiation if the client did whether to successfully complete TLS negotiation if the client did
not present a certificate which could be validated. not present a certificate which could be validated.
8. Password-based authentication 8. Password-based Authentication
8.1. Simple authentication 8.1. Simple Authentication
The LDAP "simple" authentication choice is not suitable for The LDAP "simple" authentication choice is not suitable for
authentication in environments where there is no network or authentication in environments where there is no network or
transport layer confidentiality. LDAP implementations SHOULD support transport layer confidentiality. LDAP implementations SHOULD support
authentication with the "simple" authentication choice when the authentication with the "simple" authentication choice when the
connection is protected against eavesdropping using TLS, as defined connection is protected against eavesdropping using TLS, as defined
in section 7.3. LDAP implementations SHOULD NOT support in section 5. LDAP implementations SHOULD NOT support authentication
authentication with the "simple" authentication choice unless the with the "simple" authentication choice unless the data on the
data on the connection is protected using TLS or other privacy and connection is protected using TLS or other privacy and data-
data-integrity protection. integrity protection.
8.2. Digest Authentication 8.2. Digest Authentication
LDAP server implementations MUST support authentication with a LDAP servers that implement any authentication method MUST support
password using the DIGEST-MD5 SASL mechanism for password authentication with a password using the DIGEST-MD5 SASL mechanism
protection. for password protection.
An LDAP client MAY determine whether the server supports this An LDAP client MAY determine whether the server supports this
mechanism by performing a search request on the root DSE, requesting mechanism by performing a search request on the root DSE, requesting
the supportedSASLMechanisms attribute, and checking whether the the supportedSASLMechanisms attribute, and checking whether the
string "DIGEST-MD5" is present as a value of this attribute. string "DIGEST-MD5" is present as a value of this attribute.
In the first stage of authentication, when the client is performing In the first stage of authentication, when the client is performing
an "initial authentication" as defined in section 2.1 of [RFC2831], an "initial authentication" as defined in section 2.1 of [RFC2831],
the client sends a bind request in which the version number is 3, the client sends a bind request in which the version number is 3,
the authentication choice is sasl, the sasl mechanism name is the authentication choice is sasl, the sasl mechanism name is
DIGEST- MD5, and the credentials are absent. The client then waits DIGEST- MD5, and the credentials are absent. The client then waits
for a response from the server to this request. for a response from the server to this request.
The server will respond with a bind response in which the resultCode The server will respond with a bind response in which the resultCode
is saslBindInProgress, and the serverSaslCreds field is present. The is saslBindInProgress, and the serverSaslCreds field is present. The
contents of this field is a string defined by "digest-challenge" in contents of this field is a string defined by "digest-challenge" in
Authentication Methods for LDAPv3 Mar. 1, 2002 Authentication Methods for LDAPv3
section 2.1.1 of [RFC2831]. The server SHOULD include a realm section 2.1.1 of [RFC2831]. The server SHOULD include a realm
indication and MUST indicate support for UTF-8. indication and MUST indicate support for UTF-8.
The client will send a bind request with a distinct message id, in The client will send a bind request with a distinct message id, in
which the version number is 3, the authentication choice is sasl, which the version number is 3, the authentication choice is sasl,
the sasl mechanism name is "DIGEST-MD5", and the credentials contain the sasl mechanism name is "DIGEST-MD5", and the credentials contain
the string defined by "digest-response" in section 2.1.2 of the string defined by "digest-response" in section 2.1.2 of
[RFC2831]. The serv-type is "ldap". [RFC2831]. The serv-type is "ldap".
The server will respond with a bind response in which the resultCode The server will respond with a bind response in which the resultCode
is either success, or an error indication. If the authentication is is either success, or an error indication. If the authentication is
successful and the server does not support subsequent successful and the server does not support subsequent
authentication, then the credentials field is absent. If the authentication, then the credentials field is absent. If the
authentication is successful and the server supports subsequent authentication is successful and the server supports subsequent
authentication, then the credentials field contains the string authentication, then the credentials field contains the string
defined by "response-auth" in section 2.1.3 of [4]. Support for defined by "response-auth" in section 2.1.3 of [RFC2831]. Support
subsequent authentication is OPTIONAL in clients and servers. for subsequent authentication is OPTIONAL in clients and servers.
8.3. "simple" authentication choice under TLS encryption 8.3. "simple" authentication choice under TLS encryption
Following the negotiation of an appropriate TLS ciphersuite Following the negotiation of an appropriate TLS ciphersuite
providing connection confidentiality [6], a client MAY authenticate providing connection confidentiality [RFC2246], a client MAY
to a directory that supports the simple authentication choice by authenticate to a directory that supports the simple authentication
performing a simple bind operation. choice by performing a simple bind operation.
The client will use the Start TLS operation [5] to negotiate the use The client will use the Start TLS operation [Protocol] to negotiate
of TLS security [6] on the connection to the LDAP server. The client the use of TLS security [RFC2246] on the connection to the LDAP
need not have bound to the directory beforehand. server. The client need not have bound to the directory beforehand.
For this authentication procedure to be successful, the client and For this authentication procedure to be successful, the client and
server MUST negotiate a ciphersuite which contains a bulk encryption server MUST negotiate a ciphersuite which contains a bulk encryption
algorithm of appropriate strength. Recommendations on cipher suites algorithm of appropriate strength. Recommendations on cipher suites
are given in section 11. are given in section 11.
Following the successful completion of TLS negotiation, the client Following the successful completion of TLS negotiation, the client
MUST send an LDAP bind request with the version number of 3, the MUST send an LDAP bind request with the version number of 3, the
name field containing a DN , and the "simple" authentication choice, name field containing a DN , and the "simple" authentication choice,
containing a password. containing a password.
skipping to change at page 20, line 4 skipping to change at page 18, line 4
presented password to the set of passwords associated with that presented password to the set of passwords associated with that
entry. If there is a match, then the server will respond with entry. If there is a match, then the server will respond with
resultCode success, otherwise the server will respond with resultCode success, otherwise the server will respond with
resultCode invalidCredentials. resultCode invalidCredentials.
8.4. Other authentication choices with TLS 8.4. Other authentication choices with TLS
It is also possible, following the negotiation of TLS, to perform a It is also possible, following the negotiation of TLS, to perform a
SASL authentication that does not involve the exchange of plaintext SASL authentication that does not involve the exchange of plaintext
reusable passwords. In this case the client and server need not reusable passwords. In this case the client and server need not
Authentication Methods for LDAPv3 Mar. 1, 2002 Authentication Methods for LDAPv3
negotiate a ciphersuite that provides confidentiality if the only negotiate a ciphersuite that provides confidentiality if the only
service required is data integrity. service required is data integrity.
9. Certificate-based authentication 9. Certificate-based authentication
LDAP implementations SHOULD support authentication via a client LDAP implementations SHOULD support authentication via a client
certificate in TLS, as defined in section 8.1. certificate in TLS, as defined in section 8.1.
9.1. Certificate-based authentication with TLS 9.1. Certificate-based authentication with TLS
skipping to change at page 20, line 31 skipping to change at page 18, line 31
Authority that issued the user's certificate must be sufficiently Authority that issued the user's certificate must be sufficiently
trusted by the directory server in order for the server to process trusted by the directory server in order for the server to process
the certificate. The means by which servers validate certificate the certificate. The means by which servers validate certificate
paths is outside the scope of this document. paths is outside the scope of this document.
A server MAY support mappings for certificates in which the subject A server MAY support mappings for certificates in which the subject
field name is different from the name of the user's directory entry. 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 A server which supports mappings of names MUST be capable of being
configured to support certificates for which no mapping is required. configured to support certificates for which no mapping is required.
The client will use the Start TLS operation [5] to negotiate the use The client will use the Start TLS operation [Protocol] to negotiate
of TLS security [6] on the connection to the LDAP server. The client the use of TLS security [RFC2246] on the connection to the LDAP
need not have bound to the directory beforehand. server. The client need not have bound to the directory beforehand.
In the TLS negotiation, the server MUST request a certificate. The In the TLS negotiation, the server MUST request a certificate. The
client will provide its certificate to the server, and the server client will provide its certificate to the server, and the server
MUST perform a private key-based encryption, proving it has the MUST perform a private key-based encryption, proving it has the
private key associated with the certificate. private key associated with the certificate.
In deployments that require protection of sensitive data in transit, In deployments that require protection of sensitive data in transit,
the client and server MUST negotiate a ciphersuite that contains a the client and server MUST negotiate a ciphersuite that contains a
bulk encryption algorithm of appropriate strength. Recommendations bulk encryption algorithm of appropriate strength. Recommendations
of cipher suites are given in section 11. of cipher suites are given in section 11.
skipping to change at page 20, line 56 skipping to change at page 18, line 56
server will normally check that the certificate is issued by a known server will normally check that the certificate is issued by a known
CA, and that none of the certificates on the client's certificate CA, and that none of the certificates on the client's certificate
chain are invalid or revoked. There are several procedures by which chain are invalid or revoked. There are several procedures by which
the server can perform these checks. the server can perform these checks.
Following the successful completion of TLS negotiation, the client Following the successful completion of TLS negotiation, the client
will send an LDAP bind request with the SASL "EXTERNAL" mechanism. will send an LDAP bind request with the SASL "EXTERNAL" mechanism.
10. TLS Ciphersuites 10. TLS Ciphersuites
The following ciphersuites defined in [6] MUST NOT be used for The following ciphersuites defined in [RFC2246] MUST NOT be used for
confidentiality protection of passwords or data: confidentiality protection of passwords or data:
Authentication Methods for LDAPv3 Mar. 1, 2002
TLS_NULL_WITH_NULL_NULL TLS_NULL_WITH_NULL_NULL
Authentication Methods for LDAPv3
TLS_RSA_WITH_NULL_MD5 TLS_RSA_WITH_NULL_MD5
TLS_RSA_WITH_NULL_SHA TLS_RSA_WITH_NULL_SHA
The following ciphersuites defined in [6] can be cracked easily The following ciphersuites defined in [RFC2246] can be cracked
(less than a day of CPU time on a standard CPU in 2000). These easily (less than a day of CPU time on a standard CPU in 2000).
ciphersuites are NOT RECOMMENDED for use in confidentiality These ciphersuites are NOT RECOMMENDED for use in confidentiality
protection of passwords or data. Client and server implementers protection of passwords or data. Client and server implementers
SHOULD carefully consider the value of the password or data being SHOULD carefully consider the value of the password or data being
protected before using these ciphersuites: protected before using these ciphersuites:
TLS_RSA_EXPORT_WITH_RC4_40_MD5 TLS_RSA_EXPORT_WITH_RC4_40_MD5
TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5 TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5
TLS_RSA_EXPORT_WITH_DES40_CBC_SHA TLS_RSA_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA
TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA
skipping to change at page 22, line 5 skipping to change at page 19, line 58
Servers may also wish to minimize denial of service attacks by Servers may also wish to minimize denial of service attacks by
timing out idle connections, and returning the unwillingToPerform timing out idle connections, and returning the unwillingToPerform
result code rather than performing computationally expensive result code rather than performing computationally expensive
operations requested by unauthorized clients. operations requested by unauthorized clients.
Operational experience shows that clients can misuse unauthenticated Operational experience shows that clients can misuse unauthenticated
access (simple bind with name but no password). For this reason, access (simple bind with name but no password). For this reason,
aervers SHOULD by default reject authentication requests that have a aervers SHOULD by default reject authentication requests that have a
DN with an empty password with an error of invalidCredentials. DN with an empty password with an error of invalidCredentials.
Authentication Methods for LDAPv3 Mar. 1, 2002 Access control SHOULD be applied when reading sensitive information
or updating directory information.
Access control MUST only be applied to authenticated clients and Authentication Methods for LDAPv3
SHOULD be applied when reading sensitive information or updating
directory information.
A connection on which the client has not performed the Start TLS A connection on which the client has not performed the Start TLS
operation or negotiated a suitable SASL mechanism for connection operation or negotiated a suitable SASL mechanism for connection
integrity and encryption services is subject to man-in-the-middle integrity and encryption services is subject to man-in-the-middle
attacks to view and modify information in transit. attacks to view and modify information in transit.
11.1. Start TLS Security Considerations 11.1. Start TLS Security Considerations
The goals of using the TLS protocol with LDAP are to ensure The goals of using the TLS protocol with LDAP are to ensure
connection confidentiality and integrity, and to optionally provide connection confidentiality and integrity, and to optionally provide
for authentication. TLS expressly provides these capabilities, as for authentication. TLS expressly provides these capabilities, as
described in [TLS]. described in [RFC2246].
All security gained via use of the Start TLS operation is gained by All security gained via use of the Start TLS operation is gained by
the use of TLS itself. The Start TLS operation, on its own, does not the use of TLS itself. The Start TLS operation, on its own, does not
provide any additional security. provide any additional security.
The use of TLS does not provide or ensure for confidentiality and/or The use of TLS does not provide or ensure for confidentiality and/or
non-repudiation of the data housed by an LDAP-based directory non-repudiation of the data housed by an LDAP-based directory
server. Nor does it secure the data from inspection by the server server. Nor does it secure the data from inspection by the server
administrators. Once established, TLS only provides for and ensures administrators. Once established, TLS only provides for and ensures
confidentiality and integrity of the operations and data in transit confidentiality and integrity of the operations and data in transit
skipping to change at page 23, line 5 skipping to change at page 20, line 55
Client and server implementors SHOULD take measures to ensure proper Client and server implementors SHOULD take measures to ensure proper
protection of credentials and other confidential data where such protection of credentials and other confidential data where such
measures are not otherwise provided by the TLS implementation. measures are not otherwise provided by the TLS implementation.
Server implementors SHOULD allow for server administrators to elect Server implementors SHOULD allow for server administrators to elect
whether and when connection confidentiality and/or integrity is whether and when connection confidentiality and/or integrity is
required, as well as elect whether and when client authentication required, as well as elect whether and when client authentication
via TLS is required. via TLS is required.
Authentication Methods for LDAPv3 Mar. 1, 2002
Additional security considerations relating to the EXTERNAL Additional security considerations relating to the EXTERNAL
mechanism to negotiate TLS can be found in [SASL] and [6]. mechanism to negotiate TLS can be found in [RFC2222] and [RFC2246].
12. Acknowledgements 12. Acknowledgements
Authentication Methods for LDAPv3
This document combines information originally contained in RFC 2829, This document combines information originally contained in RFC 2829,
RFC 2830 and portions of RFC 2251. The author acknowledges the work RFC 2830 and portions of RFC 2251. The author acknowledges the work
of Harald Tveit Alvestrand, Jeff Hodges, Tim Howes, Steve Kille, RL of Harald Tveit Alvestrand, Jeff Hodges, Tim Howes, Steve Kille, RL
"Bob" Morgan , and Mark Wahl, each of whom authored one or more of "Bob" Morgan , and Mark Wahl, each of whom authored one or more of
these documents. RFC 2829 and RFC 2830 were products of the IETF these documents. RFC 2829 and RFC 2830 were products of the IETF
LDAPEXT Working Group. RFC 2251 was a product of the ASID Working LDAPEXT Working Group. RFC 2251 was a product of the ASID Working
Group. Group.
This document is based upon input of the IETF LDAP Revision working This document is based upon input of the IETF LDAP Revision working
group. The contributions of its members is greatly appreciated. group. The contributions of its members is greatly appreciated.
13. Bibliography 13. Normative References
[ABNF] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Specifications: ABNF", RFC 2234, November 1997.
[IPSEC] Kent, S. and R. Atkinson, "Security Architecture for the [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
Internet Protocol", RFC 2401, November 1998. Requirement Levels", BCP 14, RFC 2119, March 1997.
[LDAPDN] Zeilenga, Kurt D., "Lightweight Directory Access Protocol [RFC2222] Myers, J., "Simple Authentication and Security Layer
(v3): UTF-8 String Representation of Distinguished Names", (SASL)", RFC 2222, October 1997.
draft-ietf-ldapbis-dn-06.txt, July, 2001.
[Protocol] Wahl, M., Kille S. and T. Howes, "Lightweight Directory [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
Access Protocol (v3)", RFC 2251, December 1997. Specifications: ABNF", RFC 2234, November 1997.
[RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May [RFC2246] Dierks, T. and C. Allen. "The TLS Protocol Version 1.0",
2000. RFC 2246, January 1999.
[RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the [RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as
Internet Protocol", RFC 2401, November 1998. a SASL Mechanism", RFC 2831, May 2000.
[RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as a [LDAPDN] Zeilenga, Kurt D. (editor), "LDAP: String Representation of
SASL Mechanism", RFC 2831, May 2000. Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, a work in
progress.
[ReqsKeywords] Bradner, S., "Key Words for use in RFCs to Indicate [Protocol] Sermersheim, J., "LDAP: The Protocol", draft-ietf-
Requirement Levels", BCP 14, RFC 2119, March 1997. ldapbis-protocol-xx.txt, a work in progress.
[ROADMAP] K. Zeilenga (editor), "LDAP: Technical Specification Road [ROADMAP] K. Zeilenga, "LDAP: Technical Specification Road Map",
Map", draft-ietf-ldapbis-roadmap-xx.txt (a work in progress). draft-ietf-ldapbis-roadmap-xx.txt, a work in progress.
[SASL] Myers, J., "Simple Authentication and Security Layer (SASL)", 14. Informative References
RFC 2222, October 1997.
[TLS] Dierks, T. and C. Allen. "The TLS Protocol Version 1.0", RFC [RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May
2246, January 1999. 2000.
Authentication Methods for LDAPv3 Mar. 1, 2002 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
Internet Protocol", RFC 2401, November 1998.
14. Author's Address 15. Author's Address
Roger Harrison Roger Harrison
Novell, Inc. Novell, Inc.
1800 S. Novell Place 1800 S. Novell Place
Provo, UT 84606 Provo, UT 84606
Authentication Methods for LDAPv3
+1 801 861 2642 +1 801 861 2642
roger_harrison@novell.com roger_harrison@novell.com
15. Full Copyright Statement 16. Full Copyright Statement
Copyright (C) The Internet Society (2000). All Rights Reserved. Copyright (C) The Internet Society (2000). All Rights Reserved.
This document and translations of it may be copied and furnished to This document and translations of it may be copied and furnished to
others, and derivative works that comment on or otherwise explain it others, and derivative works that comment on or otherwise explain it
or assist in its implementation may be prepared, copied, published or assist in its implementation may be prepared, copied, published
and distributed, in whole or in part, without restriction of any and distributed, in whole or in part, without restriction of any
kind, provided that the above copyright notice and this paragraph kind, provided that the above copyright notice and this paragraph
are included on all such copies and derivative works. However, this are included on all such copies and derivative works. However, this
document itself may not be modified in any way, such as by removing document itself may not be modified in any way, such as by removing
skipping to change at page 25, line 4 skipping to change at page 22, line 50
Internet, and have different security requirements. (In the Internet, and have different security requirements. (In the
following discussion, "sensitive data" refers to information whose following discussion, "sensitive data" refers to information whose
disclosure, alteration, destruction, or loss would adversely affect disclosure, alteration, destruction, or loss would adversely affect
the interests or business of its owner or user. Also note that there the interests or business of its owner or user. Also note that there
may be data that is protected but not sensitive.) This is not may be data that is protected but not sensitive.) This is not
intended to be a comprehensive list; other scenarios are possible, intended to be a comprehensive list; other scenarios are possible,
especially on physically protected networks. especially on physically protected networks.
(1) A read-only directory, containing no sensitive data, accessible (1) A read-only directory, containing no sensitive data, accessible
to "anyone", and TCP connection hijacking or IP spoofing is not to "anyone", and TCP connection hijacking or IP spoofing is not
Authentication Methods for LDAPv3 Mar. 1, 2002
a problem. This directory requires no security functions except a problem. This directory requires no security functions except
administrative service limits. administrative service limits.
(2) A read-only directory containing no sensitive data; read access (2) A read-only directory containing no sensitive data; read access
is granted based on identity. TCP connection hijacking is not is granted based on identity. TCP connection hijacking is not
currently a problem. This scenario requires data confidentiality currently a problem. This scenario requires data confidentiality
for sensitive authentication information AND data integrity for for sensitive authentication information AND data integrity for
all authentication information. all authentication information.
Authentication Methods for LDAPv3
(3) A read-only directory containing no sensitive data; and the (3) A read-only directory containing no sensitive data; and the
client needs to ensure the identity of the directory server and client needs to ensure the identity of the directory server and
that the directory data is not modified while being returned that the directory data is not modified while being returned
from the server. A data origin authentication service AND data from the server. A data origin authentication service AND data
integrity service are required. integrity service are required.
(4) A read-write directory, containing no sensitive data; read (4) A read-write directory, containing no sensitive data; read
access is available to "anyone", update access to properly access is available to "anyone", update access to properly
authorized persons. TCP connection hijacking is not currently a authorized persons. TCP connection hijacking is not currently a
problem. This scenario requires data confidentiality for problem. This scenario requires data confidentiality for
skipping to change at page 26, line 4 skipping to change at page 23, line 50
B.2. Access Control Factors B.2. Access Control Factors
A request, when it is being processed by a server, may be associated A request, when it is being processed by a server, may be associated
with a wide variety of security-related factors (section 4.2 of with a wide variety of security-related factors (section 4.2 of
[Protocol]). The server uses these factors to determine whether and [Protocol]). The server uses these factors to determine whether and
how to process the request. These are called access control factors how to process the request. These are called access control factors
(ACFs). They might include source IP address, encryption strength, (ACFs). They might include source IP address, encryption strength,
the type of operation being requested, time of day, etc. Some the type of operation being requested, time of day, etc. Some
factors may be specific to the request itself, others may be factors may be specific to the request itself, others may be
Authentication Methods for LDAPv3 Mar. 1, 2002
associated with the connection via which the request is transmitted, associated with the connection via which the request is transmitted,
others (e.g. time of day) may be "environmental". others (e.g. time of day) may be "environmental".
Access control policies are expressed in terms of access control Access control policies are expressed in terms of access control
factors. E.g., a request having ACFs i,j,k can perform operation Y factors. E.g., a request having ACFs i,j,k can perform operation Y
on resource Z. The set of ACFs that a server makes available for on resource Z. The set of ACFs that a server makes available for
such expressions is implementation-specific. such expressions is implementation-specific.
B.3. Authentication, Credentials, Identity B.3. Authentication, Credentials, Identity
Authentication Methods for LDAPv3
Authentication credentials are the evidence supplied by one party to Authentication credentials are the evidence supplied by one party to
another, asserting the identity of the supplying party (e.g. a user) another, asserting the identity of the supplying party (e.g. a user)
who is attempting to establish an association with the other party who is attempting to establish an association with the other party
(typically a server). Authentication is the process of generating, (typically a server). Authentication is the process of generating,
transmitting, and verifying these credentials and thus the identity transmitting, and verifying these credentials and thus the identity
they assert. An authentication identity is the name presented in a they assert. An authentication identity is the name presented in a
credential. credential.
There are many forms of authentication credentials -- the form used There are many forms of authentication credentials -- the form used
skipping to change at page 26, line 45 skipping to change at page 24, line 35
operations be performed. Access control policies are often expressed operations be performed. Access control policies are often expressed
in terms of authorization identities; e.g., entity X can perform in terms of authorization identities; e.g., entity X can perform
operation Y on resource Z. operation Y on resource Z.
The authorization identity bound to an association is often exactly The authorization identity bound to an association is often exactly
the same as the authentication identity presented by the client, but the same as the authentication identity presented by the client, but
it may be different. SASL allows clients to specify an authorization it may be different. SASL allows clients to specify an authorization
identity distinct from the authentication identity asserted by the identity distinct from the authentication identity asserted by the
client's credentials. This permits agents such as proxy servers to client's credentials. This permits agents such as proxy servers to
authenticate using their own credentials, yet request the access authenticate using their own credentials, yet request the access
privileges of the identity for which they are proxying [SASL]. Also, privileges of the identity for which they are proxying [RFC2222].
the form of authentication identity supplied by a service like TLS Also, the form of authentication identity supplied by a service like
may not correspond to the authorization identities used to express a TLS may not correspond to the authorization identities used to
server's access control policy, requiring a server-specific mapping express a server's access control policy, requiring a server-
to be done. The method by which a server composes and validates an specific mapping to be done. The method by which a server composes
authorization identity from the authentication credentials supplied and validates an authorization identity from the authentication
by a client is implementation-specific. credentials supplied by a client is implementation-specific.
Appendix C. RFC 2829 Change History Appendix C. RFC 2829 Change History
This appendix lists the changes made to the text of RFC 2829 in This appendix lists the changes made to the text of RFC 2829 in
preparing this document. preparing this document.
C.0. General Editorial Changes C.0. General Editorial Changes
Authentication Methods for LDAPv3 Mar. 1, 2002
Version -00 Version -00
- Changed other instances of the term LDAP to LDAPv3 where v3 of - Changed other instances of the term LDAP to LDAPv3 where v3 of
the protocol is implied. Also made all references to LDAPv3 use the protocol is implied. Also made all references to LDAPv3 use
the same wording. the same wording.
- Miscellaneous grammatical changes to improve readability. - Miscellaneous grammatical changes to improve readability.
- Made capitalization in section headings consistent. - Made capitalization in section headings consistent.
Version -01 Version -01
Authentication Methods for LDAPv3
- Changed title to reflect inclusion of material from RFC 2830 and - Changed title to reflect inclusion of material from RFC 2830 and
2251. 2251.
C.1. Changes to Section 1 C.1. Changes to Section 1
Version -01 Version -01
- Moved conventions used in document to a separate section. - Moved conventions used in document to a separate section.
skipping to change at page 28, line 4 skipping to change at page 25, line 44
Version -00 Version -00
- Added the following sentence: "Servers SHOULD NOT allow clients - Added the following sentence: "Servers SHOULD NOT allow clients
with anonymous authentication to modify directory entries or with anonymous authentication to modify directory entries or
access sensitive information in directory entries." access sensitive information in directory entries."
C.5.1. Changes to Section 5.1 C.5.1. Changes to Section 5.1
Version -00 Version -00
Authentication Methods for LDAPv3 Mar. 1, 2002
- Replaced the text describing the procedure for performing an - Replaced the text describing the procedure for performing an
anonymous bind (protocol) with a reference to section 4.2 of RFC anonymous bind (protocol) with a reference to section 4.2 of RFC
2251 (the protocol spec). 2251 (the protocol spec).
Version -01 Version -01
- Brought text describing procedure for performing an anonymous - Brought text describing procedure for performing an anonymous
bind from section 4.2 of RFC 2251 bis. This text will be bind from section 4.2 of RFC 2251 bis. This text will be
removed from the draft standard version of that document. removed from the draft standard version of that document.
C.6. Changes to Section 6. C.6. Changes to Section 6.
Version -00 Version -00
Authentication Methods for LDAPv3
Reorganized text in section 6.1 as follows: Reorganized text in section 6.1 as follows:
1. Added a new section (6.1) titled "Simple Authentication" and 1. Added a new section (6.1) titled "Simple Authentication" and
moved one of two introductory paragraphs for section 6 into moved one of two introductory paragraphs for section 6 into
section 6.1. Added sentences to the paragraph indicating: section 6.1. Added sentences to the paragraph indicating:
a. simple authentication is not suitable for environments where a. simple authentication is not suitable for environments where
confidentiality is not available. confidentiality is not available.
skipping to change at page 29, line 5 skipping to change at page 26, line 44
- Renamed section to 6.3 - Renamed section to 6.3
- Reworded first paragraph to remove reference to user and the - Reworded first paragraph to remove reference to user and the
userPassword password attribute Made the first paragraph more userPassword password attribute Made the first paragraph more
general by simply saying that if a directory supports simple general by simply saying that if a directory supports simple
authentication that the simple bind operation MAY performed authentication that the simple bind operation MAY performed
following negotiation of a TLS ciphersuite that supports following negotiation of a TLS ciphersuite that supports
confidentiality. confidentiality.
Authentication Methods for LDAPv3 Mar. 1, 2002
- Replaced "the name of the user's entry" with "a DN" since not - Replaced "the name of the user's entry" with "a DN" since not
all bind operations are performed on behalf of a "user." all bind operations are performed on behalf of a "user."
- Added Section 6.3.1 heading just prior to paragraph 5. - Added Section 6.3.1 heading just prior to paragraph 5.
- Paragraph 5: replaced "The server" with "DSAs that map the DN - Paragraph 5: replaced "The server" with "DSAs that map the DN
sent in the bind request to a directory entry with a sent in the bind request to a directory entry with a
userPassword attribute." userPassword attribute."
C.6.3. Changes to section 6.3. C.6.3. Changes to section 6.3.
Version -00 Version -00
- Renamed to section 6.4. - Renamed to section 6.4.
C.7. Changes to section 7. C.7. Changes to section 7.
Authentication Methods for LDAPv3
none none
C.7.1. Changes to section 7.1. C.7.1. Changes to section 7.1.
Version -00 Version -00
- Clarified the entity issuing a certificate by moving the phrase - Clarified the entity issuing a certificate by moving the phrase
"to have issued the certificate" immediately after "to have issued the certificate" immediately after
"Certification Authority." "Certification Authority."
skipping to change at page 30, line 4 skipping to change at page 27, line 42
- Moved entire section 8 of RFC 2829 into section 3.4 (Using SASL - Moved entire section 8 of RFC 2829 into section 3.4 (Using SASL
for Other Security Services) to bring material on SASL for Other Security Services) to bring material on SASL
mechanisms together into one location. mechanisms together into one location.
C.9. Changes to section 9. C.9. Changes to section 9.
Version -00 Version -00
- Paragraph 2: changed "EXTERNAL mechanism" to "EXTERNAL SASL - Paragraph 2: changed "EXTERNAL mechanism" to "EXTERNAL SASL
mechanism." mechanism."
Authentication Methods for LDAPv3 Mar. 1, 2002
- Added section 9.1. heading. - Added section 9.1. heading.
- Modified a comment in the ABNF from "unspecified userid" to - Modified a comment in the ABNF from "unspecified userid" to
"unspecified authz id". "unspecified authz id".
- Deleted sentence, "A utf8string is defined to be the UTF-8 - Deleted sentence, "A utf8string is defined to be the UTF-8
encoding of one or more ISO 10646 characters," because it is encoding of one or more ISO 10646 characters," because it is
redundant. redundant.
- Added section 9.1.1. heading. - Added section 9.1.1. heading.
- Added section 9.1.2. heading. - Added section 9.1.2. heading.
Version -01 Version -01
- Moved entire section 9 to become section 3.5 so that it would be - Moved entire section 9 to become section 3.5 so that it would be
with other SASL material. with other SASL material.
Authentication Methods for LDAPv3
C.10. Changes to Section 10. C.10. Changes to Section 10.
Version -00 Version -00
- Updated reference to cracking from a week of CPU time in 1997 to - Updated reference to cracking from a week of CPU time in 1997 to
be a day of CPU time in 2000. be a day of CPU time in 2000.
- Added text: "These ciphersuites are NOT RECOMMENDED for use... - Added text: "These ciphersuites are NOT RECOMMENDED for use...
and server implementers SHOULD" to sentence just prior the and server implementers SHOULD" to sentence just prior the
second list of ciphersuites. second list of ciphersuites.
skipping to change at page 31, line 5 skipping to change at page 28, line 42
- Inserted new section 12 that specifies when SASL protections - Inserted new section 12 that specifies when SASL protections
begin following SASL negotiation, etc. The original section 12 begin following SASL negotiation, etc. The original section 12
is renumbered to become section 13. is renumbered to become section 13.
Version -01 Version -01
- Moved to section 3.7 to be with other SASL material. - Moved to section 3.7 to be with other SASL material.
C.13. Changes to Section 13 (original section 12). C.13. Changes to Section 13 (original section 12).
Authentication Methods for LDAPv3 Mar. 1, 2002
None None
Appendix D. RFC 2830 Change History Appendix D. RFC 2830 Change History
This appendix lists the changes made to the text of RFC 2830 in This appendix lists the changes made to the text of RFC 2830 in
preparing this document. preparing this document.
D.0. General Editorial Changes D.0. General Editorial Changes
- Material showing the PDUs for the Start TLS response was broken - Material showing the PDUs for the Start TLS response was broken
out into a new section. out into a new section.
- The wording of the definition of the Start TLS request and Start - The wording of the definition of the Start TLS request and Start
TLS response was changed to make them parallel. NO changes were TLS response was changed to make them parallel. NO changes were
made to the ASN.1 definition or the associated values of the made to the ASN.1 definition or the associated values of the
parameters. parameters.
Authentication Methods for LDAPv3
- A separate section heading for graceful TLS closure was added - A separate section heading for graceful TLS closure was added
for parallelism with section on abrupt TLS closure. for parallelism with section on abrupt TLS closure.
Appendix E. RFC 2251 Change History Appendix E. RFC 2251 Change History
This appendix lists the changes made to the text of RFC 2251 in This appendix lists the changes made to the text of RFC 2251 in
preparing this document. preparing this document.
E.0. General Editorial Changes E.0. General Editorial Changes
skipping to change at page 31, line 51 skipping to change at page 29, line 34
presentation of the Start TLS operations. The section was also presentation of the Start TLS operations. The section was also
subdivided to explicitly call out the various effects being subdivided to explicitly call out the various effects being
described within it. described within it.
- All SASL profile information from RFC 2829 was brought within - All SASL profile information from RFC 2829 was brought within
the discussion of the Bind operation (primarily sections 4.4 - the discussion of the Bind operation (primarily sections 4.4 -
4.7). 4.7).
Appendix F. Change History to Combined Document Appendix F. Change History to Combined Document
F.1. Changes for draft-ldap-bis-authmeth-02.doc F.1. Changes for draft-ldap-bis-authmeth-02
General General
- Added references to other LDAP standard documents, to sections - Added references to other LDAP standard documents, to sections
within the document, and fixed broken references. within the document, and fixed broken references.
- General editorial changes¨punctuation, spelling, formatting, - General editorial changes
--
-
-
punctuation, spelling, formatting,
etc. etc.
Authentication Methods for LDAPv3 Mar. 1, 2002
Section 1. Section 1.
- Added glossary of terms and added sub-section headings - Added glossary of terms and added sub-section headings
Section 2. Section 2.
- Clarified security mechanisms 3, 4, & 5 and brought language in - Clarified security mechanisms 3, 4, & 5 and brought language in
line with IETF security glossary. line with IETF security glossary.
Section 3. Section 3.
- Brought language in requirement (3) in line with security - Brought language in requirement (3) in line with security
glossary. glossary.
- Clarified that information fetched prior to initiation of TLS - Clarified that information fetched prior to initiation of TLS
negotiation must be discarded negotiation must be discarded
Authentication Methods for LDAPv3
-Clarified that information fetched prior to initiation of SASL -Clarified that information fetched prior to initiation of SASL
negotiation must be discarded negotiation must be discarded
- Rewrote paragraph on SASL negotiation requirements to clarify - Rewrote paragraph on SASL negotiation requirements to clarify
intent intent
Section 4.4. Section 4.4.
- Added stipulation that sasl choice allows for any SASL mechanism - Added stipulation that sasl choice allows for any SASL mechanism
skipping to change at page 32, line 54 skipping to change at page 30, line 36
- Added LDAP Association State Transition Tables to show the - Added LDAP Association State Transition Tables to show the
various states through which an LDAP association may pass along various states through which an LDAP association may pass along
with the actions and decisions required to traverse from state with the actions and decisions required to traverse from state
to state. to state.
Appendix A Appendix A
- Brought security terminology in line with IETF security glossary - Brought security terminology in line with IETF security glossary
throughout the appendix. throughout the appendix.
F.2. Changes for draft-ldap-bis-authmeth-03.doc F.2. Changes for draft-ldap-bis-authmeth-03
General General
Authentication Methods for LDAPv3 Mar. 1, 2002
- Added introductory notes and changed title of document and - Added introductory notes and changed title of document and
references to conform to WG chair suggestions for the overall references to conform to WG chair suggestions for the overall
technical specification. technical specification.
- Several issues--G.13, G.14, G.16, G.17--were resolved without - Several issues--G.13, G.14, G.16, G.17--were resolved without
requiring changes to the document. requiring changes to the document.
Section 3 Section 3
- Removed reference to /etc/passwd file and associated text. - Removed reference to /etc/passwd file and associated text.
Section 4 Section 4
- Removed sections 4.1, 4.2 and parts of section 4.3. This - Removed sections 4.1, 4.2 and parts of section 4.3. This
information was being duplicated in the protocol specification information was being duplicated in the protocol specification
and will now reside there permanently. and will now reside there permanently.
Section 4.2 Section 4.2
- changed words, "not recommended" to "strongly discouraged" - changed words, "not recommended" to "strongly discouraged"
Authentication Methods for LDAPv3
Section 4.3 Section 4.3
- Based on ldapbis WG discussion at IETF52 two sentences were - Based on ldapbis WG discussion at IETF52 two sentences were
added indicating that clients SHOULD NOT send a DN value when added indicating that clients SHOULD NOT send a DN value when
binding with the sasl choice and servers SHALL ignore any value binding with the sasl choice and servers SHALL ignore any value
received in this circumstance. received in this circumstance.
- -
Section 8.3.1 Section 8.3.1
skipping to change at page 33, line 50 skipping to change at page 31, line 30
Section 11 Section 11
- Added security consideration regarding misuse of unauthenticated - Added security consideration regarding misuse of unauthenticated
access. access.
- Added security consideration requiring access control to be - Added security consideration requiring access control to be
applied only to authenticated users and recommending it be applied only to authenticated users and recommending it be
applied when reading sensitive information or updating directory applied when reading sensitive information or updating directory
information. information.
F.3. Changes for draft-ldap-bis-authmeth-04
General
- Changed references to use [RFCnnnn] format wherever possible.
(References to works in progress still use [name] format.)
- Various edits to correct typos and bring field names, etc. in
line with specification in [Protocol] draft.
- Several issues--G.13, G.14, G.16, G.17--were resolved without
requiring changes to the document.
Section 4.4.1.
- Changed ABNF grammar to use productions that are like those in
the model draft.
Section 5
- Removed sections 5.1, 5.2, and 5.4 that will be added to
[Protocol]. Renumbered sections to accommodate this change.
-
Section 6
- Reviewed LDAP Association State table for completeness and
accuracy. Renumbered actions A3, A4, and A5 to be A5, A3, and A4
respectively. Re-ordered several lines in the table to ensure
that actions are in ascending order (makes analyzing the table
Authentication Methods for LDAPv3
much more logical). Added action A2 to several states where it
was missing and valid. Added actions A7 and A8 placeholders to
states S1, S2, S4 and S5 pending resolution of issue G.28.
Section 11
- Modified security consideration (originally added in -03)
requiring access control to be applied only to authenticated
users. This seems nonsensical because anonymous users may have
access control applied to limit permissible actions.
-
Section 13
- Verified all normative references and moved informative
references to a new section 14.
Appendix G. Issues to be Resolved Appendix G. Issues to be Resolved
This appendix lists open questions and issues that need to be This appendix lists open questions and issues that need to be
resolved before work on this document is deemed complete. resolved before work on this document is deemed complete.
G.1. G.1.
Authentication Methods for LDAPv3 Mar. 1, 2002
Section 1 lists 6 security mechanisms that can be used by LDAP Section 1 lists 6 security mechanisms that can be used by LDAP
servers. I'm not sure what mechanism 5, "Resource limitation by servers. I'm not sure what mechanism 5, "Resource limitation by
means of administrative limits on service controls" means. means of administrative limits on service controls" means.
Status: resolved. Changed wording to "administrative service limits" Status: resolved. Changed wording to "administrative service limits"
to clarify meaning. to clarify meaning.
G.2. G.2.
Section 2 paragraph 1 defines the term, "sensitive." Do we want to Section 2 paragraph 1 defines the term, "sensitive." Do we want to
skipping to change at page 34, line 37 skipping to change at page 33, line 4
Status: resolved. Based on the idea that a "secure authentication Status: resolved. Based on the idea that a "secure authentication
function" could be provided by TLS, I changed the wording to require function" could be provided by TLS, I changed the wording to require
data confidentiality for sensitive authentication information and data confidentiality for sensitive authentication information and
data integrity for all authentication information. data integrity for all authentication information.
G.4. G.4.
Section 3, deployment scenario 3: What is meant by the phrase, Section 3, deployment scenario 3: What is meant by the phrase,
"directory data is authenticated by the server?" "directory data is authenticated by the server?"
Authentication Methods for LDAPv3
Status: resolved. I interpreted this to mean the ability to ensure Status: resolved. I interpreted this to mean the ability to ensure
the identity of the directory server and the integrity of the data the identity of the directory server and the integrity of the data
sent from that server to the client, and explictly stated such. sent from that server to the client, and explictly stated such.
G.5. G.5.
Section 4 paragraph 3: What is meant by the phrase, "this means that Section 4 paragraph 3: What is meant by the phrase, "this means that
either this data is useless for faking authentication (like the Unix either this data is useless for faking authentication (like the Unix
"/etc/passwd" file format used to be)?" "/etc/passwd" file format used to be)?"
skipping to change at page 35, line 5 skipping to change at page 33, line 26
Status: resolved. Discussion at IETF 52 along with discussions with Status: resolved. Discussion at IETF 52 along with discussions with
the original authors of this material have convinced us that this 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 reference is simply too arcane to be left in place. In -03 the text
has been modified to focus on the need to either update password has been modified to focus on the need to either update password
information in a protected fashion outside of the protocol or to information in a protected fashion outside of the protocol or to
update it in session well protected against snooping, and the update it in session well protected against snooping, and the
reference to /etc/passwd has been removed. reference to /etc/passwd has been removed.
G.6. G.6.
Authentication Methods for LDAPv3 Mar. 1, 2002
Section 4 paragraph 7 begins: "For a directory needing session Section 4 paragraph 7 begins: "For a directory needing session
protection..." Is this referring to data confidentiality or data protection..." Is this referring to data confidentiality or data
integrity or both? integrity or both?
Status: resolved. Changed wording to say, "For a directory needing Status: resolved. Changed wording to say, "For a directory needing
data security (both data integrity and data confidentiality)..." data security (both data integrity and data confidentiality)..."
G.7. G.7.
Section 4 paragraph 8 indicates that "information about the server Section 4 paragraph 8 indicates that "information about the server
skipping to change at page 35, line 40 skipping to change at page 34, line 5
layer is negotiated to ensure that they are using the best available layer is negotiated to ensure that they are using the best available
security mechanism supported mutually by the client and server. A security mechanism supported mutually by the client and server. A
note at the end of the paragraph indicates that this is a SHOULD note at the end of the paragraph indicates that this is a SHOULD
since there are environments where the client might get a list of since there are environments where the client might get a list of
supported SASL mechanisms from a different trusted source. supported SASL mechanisms from a different trusted source.
I wonder if the intent of this could be restated more plainly using I wonder if the intent of this could be restated more plainly using
one of these two approaches (I've paraphrased for the sake of one of these two approaches (I've paraphrased for the sake of
brevity): brevity):
Authentication Methods for LDAPv3
Approach 1: Clients SHOULD check the supportedSASLMechanisms Approach 1: Clients SHOULD check the supportedSASLMechanisms
list both before and after SASL negotiation or clients SHOULD list both before and after SASL negotiation or clients SHOULD
use a different trusted source to determine available supported use a different trusted source to determine available supported
SASL mechanisms. SASL mechanisms.
Approach 2: Clients MUST check the supportedSASLMechanisms list Approach 2: Clients MUST check the supportedSASLMechanisms list
both before and after SASL negotiation UNLESS they use a both before and after SASL negotiation UNLESS they use a
different trusted source to determine available supported SASL different trusted source to determine available supported SASL
mechanisms. mechanisms.
Status: Resolved. WG input at IETF 51 was that Approach 1 was Status: Resolved. WG input at IETF 51 was that Approach 1 was
probably best. I ended up keeping the basic structure similar to the probably best. I ended up keeping the basic structure similar to the
original to meet this intent. original to meet this intent.
G.9. G.9.
Section 6.3.1 states: "DSAs that map the DN sent in the bind request 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 to a directory entry with a userPassword attribute will... compare
[each value in the named user's entry]... with the presented [each value in the named user's entry]... with the presented
password." This implies that this this applies only to user entries password." This implies that this applies only to user entries with
Authentication Methods for LDAPv3 Mar. 1, 2002 userPassword attributes. What about other types of entries that
might allow passwords and might store in the password information in
with userPassword attributes. What about other types of entries other attributes? Do we want to make this text more general?
that might allow passwords and might store in the password
information in other attributes? Do we want to make this text more
general?
Status: Resolved in -03 draft by generalizing section 8.3.1 to not Status: Resolved in -03 draft by generalizing section 8.3.1 to not
refer to any specific password attribute and by removing the term refer to any specific password attribute and by removing the term
"user" in referring to the directory entry specified by the DN in "user" in referring to the directory entry specified by the DN in
the bind request. the bind request.
G.10 userPassword and simple bind G.10 userPassword and simple bind
We need to be sure that we don't require userPassword to be the only 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 attribute used for authenticating via simple bind. (See 2251 sec 4.2
skipping to change at page 36, line 40 skipping to change at page 35, line 4
G.11. Meaning of LDAP Association G.11. Meaning of LDAP Association
The original RFC 2830 uses the term "LDAP association" in describing The original RFC 2830 uses the term "LDAP association" in describing
a connection between an LDAP client and server regardless of the a connection between an LDAP client and server regardless of the
state of TLS on that connection. This term needs to be defined or state of TLS on that connection. This term needs to be defined or
possibly changed. possibly changed.
Status: Resolved. at IETF 51 Bob Morgan indicated that the term Status: Resolved. at IETF 51 Bob Morgan indicated that the term
"LDAP association" was intended to distinguish the LDAP-level "LDAP association" was intended to distinguish the LDAP-level
connection from the TLS-level connection. This still needs to be connection from the TLS-level connection. This still needs to be
Authentication Methods for LDAPv3
clarified somewhere in the draft. Added "LDAP association" to a clarified somewhere in the draft. Added "LDAP association" to a
glossary in section 1. glossary in section 1.
G.12. Is DIGEST-MD5 mandatory for all implementations? G.12. Is DIGEST-MD5 mandatory for all implementations?
Reading 2829bis I think DIGEST-MD5 is mandatory ONLY IF your server Reading 2829bis I think DIGEST-MD5 is mandatory ONLY IF your server
supports password based authentication...but the following makes it supports password based authentication...but the following makes it
sound mandatory to provide BOTH password authentication AND DIGEST- sound mandatory to provide BOTH password authentication AND DIGEST-
MD5: MD5:
"6.2. Digest authentication "6.2. Digest authentication
LDAP implementations MUST support authentication with a password LDAP implementations MUST support authentication with a password
using the DIGEST-MD5 SASL mechanism for password protection, as using the DIGEST-MD5 SASL mechanism for password protection, as
defined in section 6.1." defined in section 6.1."
The thing is for acl it would be nice (though not critical) to be The thing is for acl it would be nice (though not critical) to be
able to default the required authentication level for a subject to a able to default the required authentication level for a subject to a
Authentication Methods for LDAPv3 Mar. 1, 2002
single "fairly secure" mechanism--if there is no such mandatory single "fairly secure" mechanism--if there is no such mandatory
authentication scheme then you cannot do that. (Source: Rob Byrne) authentication scheme then you cannot do that. (Source: Rob Byrne)
Status: resolved. -00 version of the draft added a sentence at the Status: resolved. -00 version of the draft added a sentence at the
beginning of section 8.2 stating that LDAP server implementations beginning of section 8.2 stating that LDAP server implementations
must support this method. must support this method.
G.13. Ordering of authentication levels requested G.13. Ordering of authentication levels requested
Again on the subject of authentication level, is it possible to Again on the subject of authentication level, is it possible to
skipping to change at page 37, line 43 skipping to change at page 36, line 5
outlined. When I say "security properties" I mean stuff like "This outlined. When I say "security properties" I mean stuff like "This
scheme is vulnerable to such and such attacks, is only safe if the scheme is vulnerable to such and such attacks, is only safe if the
key size is > 50, this hash is widely considered the best, etc...". key size is > 50, this hash is widely considered the best, etc...".
I think an LDAP implementor is likely to be interested in that I think an LDAP implementor is likely to be interested in that
information, without having to wade through the security RFCs. information, without having to wade through the security RFCs.
(Source: Rob Byrne) (Source: Rob Byrne)
Status: out of scope. This is outside the scope of this document and Status: out of scope. This is outside the scope of this document and
will not be addressed. will not be addressed.
Authentication Methods for LDAPv3
G.15. Include a StartTLS state transition table G.15. Include a StartTLS state transition table
The pictoral representation it is nominally based on is here (URL The pictoral representation it is nominally based on is here (URL
possibly folded): possibly folded):
http://www.stanford.edu/~hodges/doc/LDAPAssociationStateDiagram- http://www.stanford.edu/~hodges/doc/LDAPAssociationStateDiagram-
1999-12-14.html 1999-12-14.html
(Source: Jeff Hodges) (Source: Jeff Hodges)
Status: Table provided. Final review of content for accuracy is Status: Resolved. Table provided in -03. Review of content for
still needed. accuracy in -04.
G.16. Empty sasl credentials question G.16. Empty sasl credentials question
Authentication Methods for LDAPv3 Mar. 1, 2002
I spent some more time looking microscopically at ldap-auth-methods I spent some more time looking microscopically at ldap-auth-methods
and ldap-ext-tls drafts. The drafts say that the credential must and ldap-ext-tls drafts. The drafts say that the credential must
have the form dn:xxx or u:xxx or be absent, and although they don't have the form dn:xxx or u:xxx or be absent, and although they don't
say what to do in the case of an empty octet string I would say that say what to do in the case of an empty octet string I would say that
we could send protocolError (claim it is a bad PDU). we could send protocolError (claim it is a bad PDU).
There is still the question of what to do if the credential is 'dn:' There is still the question of what to do if the credential is 'dn:'
(or 'u:') followed by the empty string. (Source: ariel@columbia.edu (or 'u:') followed by the empty string. (Source: ariel@columbia.edu
via Jeff Hodges) via Jeff Hodges)
skipping to change at page 38, line 44 skipping to change at page 37, line 4
Also, The hostname check against the name in the certificate is a Also, The hostname check against the name in the certificate is a
very weak means of preventing man-in-the-middle attacks; the proper very weak means of preventing man-in-the-middle attacks; the proper
solution is not here yet (SecureDNS or some equivalent). Faking out solution is not here yet (SecureDNS or some equivalent). Faking out
DNS is not so hard, and we see this sort of thing in the press on a DNS is not so hard, and we see this sort of thing in the press on a
pretty regular basis, where site A hijacks the DNS server for site B pretty regular basis, where site A hijacks the DNS server for site B
and gets all their requests. Some mention of this should be made in and gets all their requests. Some mention of this should be made in
the draft. (Source: ariel@columbia.edu via Jeff Hodges) the draft. (Source: ariel@columbia.edu via Jeff Hodges)
Status: resolved. Based on discussion at IETF 52 ldapbis WG meeting, 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 this text will stand as it is. The check is a MUST, but the behavior
Authentication Methods for LDAPv3
afterward is a SHOULD. This gives server implementations the room to afterward is a SHOULD. This gives server implementations the room to
maneuver as needed. maneuver as needed.
G.18. Must SASL DN exist in the directory? G.18. Must SASL DN exist in the directory?
If the 'dn:' form of sasl creds is used, is it the intention of the 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 draft(ers) that this DN must exist in the directory and the client
will have the privileges associated with that entry, or can the will have the privileges associated with that entry, or can the
server map the sasl DN to perhaps some other DN in the directory, server map the sasl DN to perhaps some other DN in the directory,
in an implementation-dependent fashion? in an implementation-dependent fashion?
We already know that if *no* sasl credentials are presented, the DN We already know that if *no* sasl credentials are presented, the DN
or altname in the client certificate may be mapped to a DN in an or altname in the client certificate may be mapped to a DN in an
implementation-dependent fashion, or indeed to something not in the implementation-dependent fashion, or indeed to something not in the
Authentication Methods for LDAPv3 Mar. 1, 2002
directory at all. (Right?) (Source: ariel@columbia.edu via Jeff directory at all. (Right?) (Source: ariel@columbia.edu via Jeff
Hodges) Hodges)
G.19. DN used in conjunction with SASL mechanism G.19. DN used in conjunction with SASL mechanism
We need to specify whether the DN field in Bind operation can/cannot We need to specify whether the DN field in Bind operation can/cannot
be used when SASL mechanism is specified. (source: RL Bob) be used when SASL mechanism is specified. (source: RL Bob)
Status: resolved. (-03) Based on ldapbis WG discussion at IETF52 two Status: in process. (-03) Based on ldapbis WG discussion at IETF52
sentences were added indicating that clients SHOULD NOT send a DN two sentences were added to section 4.3 indicating that clients
value when binding with the sasl choice and servers SHALL ignore any SHOULD NOT send a DN value when binding with the sasl choice and
value received in this circumstance. servers SHALL ignore any value received in this circumstance. During
edits for -04 version of draft it was noted that [Protocol] section
4.2 conflicts with this draft. The editor of [Protocol] has been
notified of the discrepancy, and discussion is underway.
G.20. Bind states G.20. Bind states
Differences between unauthenticated and anonymous. four states you Differences between unauthenticated and anonymous. four states you
can get into. One is completely undefined (this is now explicitly can get into. One is completely undefined (this is now explicitly
called out in document). This text needs to be moved from called out in document). This text needs to be moved from
RFC2251bis to this draft. (source: Jim Sermersheim) RFC2251bis to this draft. (source: Jim Sermersheim)
G.21. Misuse of unauthenticated access G.21. Misuse of unauthenticated access
Add a security consideration that operational experience shows that Add a security consideration that operational experience shows that
clients can misuse unauthenticated access (simple bind with name but clients can misuse unauthenticated access (simple bind with name but
no password). Servers SHOULD by default reject authentication no password). Servers SHOULD by default reject authentication
requests that have a DN with an empty password with an error of requests that have a DN with an empty password with an error of
invalidCredentials. (Source: Kurt Zeilenga and Chris Newman (Sun)) invalidCredentials. (Source: Kurt Zeilenga and Chris Newman (Sun))
Status: Resolved. Added to security considerations in ű03. Status: Resolved. Added to security considerations in -
-03.
G.22. Need to move StartTLS protocol information to [Protocol] G.22. Need to move StartTLS protocol information to [Protocol]
Status: In Process. Removed Sections 5.1, 5.2, and 5.4 for -04 and
requested that they be put into [Protocol].
G.23. Split Normative and Non-normative references into separate
sections.
Authentication Methods for LDAPv3
Status: Resolved. Changes made in -04
G.24. What is the authentication state if a Bind operation is
abandoned?
Status: new item discovered during -04 edits.
G.25. Difference between checking server hostname and server's
canonical DNS name in Server Identity Check?
Section 5.3.6: I now understand the intent of the check (prevent
man-in-the-middle attacks). But what is the subtle difference
between the "server hostname" and the "server's canonical DNS name"?
(Source: Tim Hahn)
Status: new item discovered during -04 edits.
6.26. Server Identity Check using servers located via SRV records
Section 5.3.6: What should be done if the server was found using SRV
records based on the "locate" draft/RFC? (Source: Tim Hahn).
Status: new item discovered during -04 edits.
G.27 Inconsistency in effect of TLS closure on LDAP association.
Section 5.4.1 of authmeth -04 (section 4.1 of RFC2830) states that
TLS closure alert will leave the LDAP association intact. Contrast
this with Section 5.5.2 (section 5.2 of RFC2830) that says that the
closure of the TLS connection MUST cause the LDAP association to
move to an anonymous authentication.
Status: new item discovered during -04 edits.
G.28 Ordering of external sources of authentication credentials
Section 4.3.2 implies that external sources of authentication
credentials other than TLS are permitted. What is the behavior when
two external sources of authentication credentials are available
(e.g. TLS and IPsec are both present (is this possible?)) and a SASL
EXTERNAL Bind operation is performed?
Status: new item discovered during -04 edits.
 End of changes. 

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