3 Internet-Draft Editor: R. Harrison
4 Intended Category: Draft Standard Novell, Inc.
5 Document: draft-ietf-ldapbis-authmeth-05.txt March 2003
6 Obsoletes: RFC 2829, RFC 2830
9 LDAP: Authentication Methods
11 Connection Level Security Mechanisms
15 This document is an Internet-Draft and is in full conformance with
16 all provisions of Section 10 of RFC2026.
18 This document is intended to be, after appropriate review and
19 revision, submitted to the RFC Editor as a Standard Track document.
20 Distribution of this memo is unlimited. Technical discussion of
21 this document will take place on the IETF LDAP Extension Working
22 Group mailing list <ietf-ldapbis@OpenLDAP.org>. Please send
23 editorial comments directly to the author
24 <roger_harrison@novell.com>.
26 Internet-Drafts are working documents of the Internet Engineering
27 Task Force (IETF), its areas, and its working groups. Note that
28 other groups may also distribute working documents as Internet-
29 Drafts. Internet-Drafts are draft documents valid for a maximum of
30 six months and may be updated, replaced, or obsoleted by other
31 documents at any time. It is inappropriate to use Internet-Drafts
32 as reference material or to cite them other than as "work in
35 The list of current Internet-Drafts can be accessed at
36 http://www.ietf.org/ietf/1id-abstracts.txt The list of Internet-
37 Draft Shadow Directories can be accessed at
38 http://www.ietf.org/shadow.html.
42 This document describes LDAPv3 (Lightweight Directory Access
43 Protocol v3) authentication methods and connection level security
44 mechanisms that are required of all conforming LDAPv3 server
45 implementations and makes recommendations for combinations of these
46 mechanisms to be used in various deployment circumstances.
48 Among the mechanisms described are
50 - various forms of authentication including anonymous
51 authentication, password-based authentication, and certificate
53 - the use of SASL mechanisms with LDAPv3
54 - the use of TLS (Transport Layer Security) with LDAPv3
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59 Authentication Methods for LDAPv3
61 - the various authentication and authorization states through
62 which a connection to an LDAP server may pass and the actions
63 that trigger these state changes.
66 1. Conventions Used in this Document
68 1.1. Glossary of Terms
70 The following terms are used in this document. To aid the reader,
71 these terms are defined here.
73 - "user" represents any application which is an LDAP client using
74 the directory to retrieve or store information.
76 - "LDAP association" is used to distinguish the LDAP-level
77 connection from any underlying TLS-level connection that may or
80 1.2. Security Terms and Concepts
82 In general, security terms in this document are used consistently
83 with the definitions provided in [RFC2828]. In addition, several
84 terms and concepts relating to security, authentication, and
85 authorization are presented in Appendix B of this document. While
86 the formal definition of these terms and concepts is outside the
87 scope of this document, an understanding of them is prerequisite to
88 understanding much of the material in this document. Readers who are
89 unfamiliar with security-related concepts are encouraged to review
90 Appendix B before reading the remainder of this document.
94 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
95 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
96 document are to be interpreted as described in RFC 2119 [RFC2119].
100 This document is an integral part of the LDAP Technical
101 Specification [ROADMAP]. This document replaces RFC 2829 and
102 portions of RFC 2830. Changes to RFC 2829 are summarized in Appendix
103 C and changes to RFC 2830 are summarized in Appendix D.
105 LDAPv3 is a powerful access protocol for directories. It offers
106 means of searching, retrieving and manipulating directory content,
107 and ways to access a rich set of security functions.
109 It is vital that these security functions be interoperable among all
110 LDAP clients and servers on the Internet; therefore there has to be
111 a minimum subset of security functions that is common to all
112 implementations that claim LDAPv3 conformance.
114 Basic threats to an LDAP directory service include:
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121 (1) Unauthorized access to directory data via data-retrieval
124 (2) Unauthorized access to reusable client authentication
125 information by monitoring others' access,
127 (3) Unauthorized access to directory data by monitoring others'
130 (4) Unauthorized modification of directory data,
132 (5) Unauthorized modification of configuration information,
134 (6) Unauthorized or excessive use of resources (denial of service),
137 (7) Spoofing of directory: Tricking a client into believing that
138 information came from the directory when in fact it did not,
139 either by modifying data in transit or misdirecting the client's
142 Threats (1), (4), (5) and (6) are due to hostile clients. Threats
143 (2), (3) and (7) are due to hostile agents on the path between
144 client and server or hostile agents posing as a server.
146 The LDAP protocol suite can be protected with the following security
149 (1) Client authentication by means of the SASL [RFC2222] mechanism
150 set, possibly backed by the TLS [RFC2246] credentials exchange
153 (2) Client authorization by means of access control based on the
154 requestor's authenticated identity,
156 (3) Data integrity protection by means of the TLS protocol or SASL
157 mechanisms that provide data integrity services,
159 (4) Data confidentiality protection against snooping by means of the
160 TLS protocol or SASL mechanisms that provide data
161 confidentiality services,
163 (5) Server resource usage limitation by means of administrative
164 service limits configured on the server, and
166 (6) Server authentication by means of the TLS protocol or SASL
169 At the moment, imposition of access controls is done by means
170 outside the scope of the LDAPv3 protocol.
172 3. Rationale for LDAPv3 Security Mechanisms
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180 It seems clear that allowing any implementation, faced with the
181 above requirements, to simply pick and choose among the possible
182 alternatives is not a strategy that is likely to lead to
183 interoperability. In the absence of mandates, clients will be
184 written that do not support any security function supported by the
185 server, or worse, they will support only mechanisms like the LDAPv3
186 simple bind using clear text passwords that provide inadequate
187 security for most circumstances.
189 Given the presence of the Directory, there is a strong desire to see
190 mechanisms where identities take the form of an LDAP distinguished
191 name [LDAPDN] and authentication data can be stored in the
192 directory. This means that this data must be updated outside the
193 protocol or only updated in sessions well protected against
194 snooping. It is also desirable to allow authentication methods to
195 carry authorization identities based on existing--non-LDAP DN--forms
196 of user identities for backwards compatibility with non-LDAP-based
197 authentication services.
199 The set of security mechanisms provided in LDAPv3 and described in
200 this document is intended to meet the security needs for a wide
201 range of deployment scenarios and still provide a high degree of
202 interoperability among various LDAPv3 implementations and
203 deployments. Appendix A contains example deployment scenarios that
204 list the mechanisms that might be used to achieve a reasonable level
205 of security in various circumstances.
209 The Bind operation defined in section 4.2 of [Protocol] allows
210 authentication information to be exchanged between the client and
213 4.1. Unbound Connection Treated as Anonymous ("Implied Anonymous Bind")
215 Unlike LDAP version 2, the client need not send a Bind Request in
216 the first PDU of the connection. The client may send any operation
217 request prior to binding, and the server MUST treat it as if it had
218 been performed after an anonymous bind operation. If the server
219 requires that the client bind before browsing or modifying the
220 directory, the server MAY reject a request other than binding,
221 unbinding or an extended request with the "operationsError" result.
224 4.2. Simple Authentication
226 The simple authentication option provides minimal authentication
227 facilities, with the contents of the authentication field consisting
228 only of a cleartext password. Note that the use of cleartext
229 passwords is strongly discouraged over open networks when the
230 underlying transport service cannot guarantee confidentiality (see
233 4.3. SASL Authentication
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240 The sasl authentication option allows for any mechanism defined for
241 use with SASL [RFC2222] not specifically prohibited by this document
244 Clients sending a bind request with the sasl choice selected SHOULD
245 NOT send a value in the name field. Servers receiving a bind request
246 with the sasl choice selected SHALL ignore any value in the name
249 The mechanism field in SaslCredentials contains the name of the
250 mechanism. The credentials field contains the arbitrary data used
251 for authentication, inside an OCTET STRING wrapper. Note that unlike
252 some Internet application protocols where SASL is used, LDAP is not
253 text-based, thus no Base64 transformations are performed on the
256 If any SASL-based integrity or confidentiality services are enabled,
257 they take effect following the transmission by the server and
258 reception by the client of the final BindResponse with a resultCode
261 If a SASL security layer is negotiated, the client MUST discard all
262 information about the server fetched prior to the initiation of the
263 SASL negotiation. If the client is configured to support multiple
264 SASL mechanisms, it SHOULD fetch the supportedSASLmechanisms list
265 both before and after the SASL security layer is negotiated. This
266 allows the client to detect active attacks that remove supported
267 SASL mechanisms from the supportedSASLMechanisms list and allows the
268 client to ensure that it is using the best mechanism supported by
269 both client and server. (This requirement is a SHOULD to allow for
270 environments where the supportedSASLMechanisms list is provided to
271 the client through a different trusted source, e.g. as part of a
272 digitally signed object.)
274 The client can request that the server use authentication
275 information from a lower layer protocol by using the SASL EXTERNAL
276 mechanism (see section 5.2.2.).
278 4.3.1. Use of ANONYMOUS and PLAIN SASL Mechanisms
280 As LDAP includes native anonymous and plaintext authentication
281 methods, the "ANONYMOUS" and "PLAIN" SASL mechanisms are not used
282 with LDAP. If an authorization identity of a form different from a
283 DN is requested by the client, a data confidentiality mechanism that
284 protects the password in transit should be used.
286 4.3.2. Use of EXTERNAL SASL Mechanism
288 The "EXTERNAL" SASL mechanism can be used to request the LDAP server
289 make use of security credentials exchanged by a lower layer. If a
290 TLS session has not been established between the client and server
291 prior to making the SASL EXTERNAL Bind request and there is no other
292 external source of authentication credentials (e.g. IP-level
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298 security [RFC2401]), or if during the process of establishing the
299 TLS session, the server did not request the client's authentication
300 credentials, the SASL EXTERNAL bind MUST fail with a resultCode of
301 inappropriateAuthentication. Any client authentication and
302 authorization state of the LDAP association is lost, so the LDAP
303 association is in an anonymous state after the failure (see
304 [Protocol] section 4.2.1).
306 4.3.3. Other SASL Mechanisms
308 Other SASL mechanisms may be used with LDAP, but their usage is not
309 considered in this document.
311 4.4. SASL Authorization Identity
313 The authorization identity is carried as part of the SaslCredentials
314 credentials field in the Bind request and response.
316 When the "EXTERNAL" SASL mechanism is being negotiated, if the
317 credentials field is present, it contains an authorization identity
318 of the authzId form described below.
320 Other mechanisms define the location of the authorization identity
321 in the credentials field.
323 4.4.1. Authorization Identity Syntax
325 The authorization identity is a string in the UTF-8 character set,
326 corresponding to the following ABNF grammar [RFC2234]:
328 ; Specific predefined authorization (authz) id schemes are
329 ; defined below -- new schemes may be defined in the future.
331 authzId = dnAuthzId / uAuthzId
333 DNCOLON = %x64 %x6e %x3a ; "dn:"
334 UCOLON = %x75 %x3a ; "u:"
336 ; distinguished-name-based authz id.
337 dnAuthzId = DNCOLON dn
338 dn = utf8string ; with syntax defined in [LDAPDN] section 3.
341 ; unspecified authorization id, UTF-8 encoded.
342 uAuthzId = UCOLON userid
343 userid = utf8string ; syntax unspecified
345 The dnAuthzId choice allows client applications to assert
346 authorization identities in the form of a distinguished name. The
347 decision to allow or disallow an authentication identity to have
348 access to the requested authorization identity is a matter of local
349 policy ([SASL] section 4.2). For this reason there is no requirement
350 that the asserted dn be that of an entry in directory.
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357 The uAuthzId choice allows for compatibility with client
358 applications that wish to assert an authorization identity to a
359 local directory but do not have that identity in distinguished name
360 form. The format of utf8string is defined as only a sequence of UTF-
361 8 encoded ISO 10646 characters, and further interpretation is
362 subject to prior agreement between the client and server.
364 For example, the userid could identify a user of a specific
365 directory service, or be a login name or the local-part of an RFC
366 822 email address. In general, a uAuthzId MUST NOT be assumed to be
369 Additional authorization identity schemes MAY be defined in future
370 versions of this document.
372 4.5. SASL Service Name for LDAP
374 For use with SASL [RFC2222], a protocol must specify a service name
375 to be used with various SASL mechanisms, such as GSSAPI. For LDAP,
376 the service name is "ldap", which has been registered with the IANA
377 as a GSSAPI service name.
379 4.6. SASL Integrity and Privacy Protections
381 Any negotiated SASL integrity and privacy protections SHALL start on
382 the first octet of the first LDAP PDU following successful
383 completion of the SASL bind operation. If lower level security layer
384 is negotiated, such as TLS, any SASL security services SHALL be
385 layered on top of such security layers regardless of the order of
388 5. Start TLS Operation
390 The Start Transport Layer Security (StartTLS) operation defined in
391 section 4.13 of [Protocol] provides the ability to establish
392 Transport Layer Security [RFC2246] on an LDAP association.
394 5.1. Sequencing of the Start TLS Operation
396 This section describes the overall procedures clients and servers
397 must follow for TLS establishment. These procedures take into
398 consideration various aspects of the overall security of the LDAP
399 association including discovery of resultant security level and
400 assertion of the client's authorization identity.
402 Note that the precise effects, on a client's authorization identity,
403 of establishing TLS on an LDAP association are described in detail
406 5.1.1. Requesting to Start TLS on an LDAP Association
408 The client MAY send the Start TLS extended request at any time after
409 establishing an LDAP association, except that in the following cases
410 the client MUST NOT send a Start TLS extended request:
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417 - if TLS is currently established on the connection, or
418 - during a multi-stage SASL negotiation, or
419 - if there are any LDAP operations outstanding on the
422 The result of violating any of these requirements is a resultCode of
423 operationsError, as described above in [Protocol] section 14.3.2.2.
425 In particular, there is no requirement that the client have or have
426 not already performed a Bind operation before sending a Start TLS
427 operation request. The client may have already performed a Bind
428 operation when it sends a Start TLS request, or the client might
431 If the client did not establish a TLS connection before sending any
432 other requests, and the server requires the client to establish a
433 TLS connection before performing a particular request, the server
434 MUST reject that request by sending a resultCode of
435 confidentialityRequired or strongAuthRequired. In response, the
436 client MAY send a Start TLS extended request, or it MAY choose to
437 close the connection.
441 The server will return an extended response with the resultCode of
442 success if it is willing and able to negotiate TLS. It will return
443 other resultCodes (documented in [Protocol] section 4.13.2.2) if it
446 In the successful case, the client (which has ceased to transfer
447 LDAP requests on the connection) MUST either begin a TLS negotiation
448 or close the connection. The client will send PDUs in the TLS Record
449 Protocol directly over the underlying transport connection to the
450 server to initiate TLS negotiation [RFC2246].
452 5.1.3. TLS Version Negotiation
454 Negotiating the version of TLS or SSL to be used is a part of the
455 TLS Handshake Protocol, as documented in [RFC2246]. Please refer to
456 that document for details.
458 5.1.4. Discovery of Resultant Security Level
460 After a TLS connection is established on an LDAP association, both
461 parties MUST individually decide whether or not to continue based on
462 the privacy level achieved. Ascertaining the TLS connection's
463 privacy level is implementation dependent, and accomplished by
464 communicating with one's respective local TLS implementation.
466 If the client or server decides that the level of authentication or
467 privacy is not high enough for it to continue, it SHOULD gracefully
468 close the TLS connection immediately after the TLS negotiation has
469 completed (see [Protocol] section 4.13.3.1 and section 5.2.3 below).
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475 If the client decides to continue, it MAY attempt to Start TLS
476 again, it MAY send an unbind request, or it MAY send any other LDAP
479 5.1.5. Assertion of Client's Authorization Identity
481 The client MAY, upon receipt of a Start TLS response indicating
482 success, assert that a specific authorization identity be utilized
483 in determining the client's authorization status. The client
484 accomplishes this via an LDAP Bind request specifying a SASL
485 mechanism of "EXTERNAL" [RFC2222] (see section 5.5.1.2 below).
487 5.1.6. Server Identity Check
489 The client MUST check its understanding of the server's hostname
490 against the server's identity as presented in the server's
491 Certificate message, in order to prevent man-in-the-middle attacks.
493 Matching is performed according to these rules:
495 - The client MUST use the server hostname it used to open the LDAP
496 connection as the value to compare against the server name as
497 expressed in the server's certificate. The client MUST NOT use
498 the any other derived form of name including the server's
501 - If a subjectAltName extension of type dNSName is present in the
502 certificate, it SHOULD be used as the source of the server's
505 - Matching is case-insensitive.
507 - The "*" wildcard character is allowed. If present, it applies
508 only to the left-most name component.
510 For example, *.bar.com would match a.bar.com and b.bar.com, but it
511 would not match a.x.bar.com nor would it match bar.com. If more
512 than one identity of a given type is present in the certificate
513 (e.g. more than one dNSName name), a match in any one of the set is
514 considered acceptable.
516 If the hostname does not match the dNSName-based identity in the
517 certificate per the above check, user-oriented clients SHOULD either
518 notify the user (clients MAY give the user the opportunity to
519 continue with the connection in any case) or terminate the
520 connection and indicate that the server's identity is suspect.
521 Automated clients SHOULD close the connection, returning and/or
522 logging an error indicating that the server's identity is suspect.
524 Beyond the server identity checks described in this section, clients
525 SHOULD be prepared to do further checking to ensure that the server
526 is authorized to provide the service it is observed to provide. The
527 client MAY need to make use of local policy information.
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534 5.1.7. Refresh of Server Capabilities Information
536 Upon TLS session establishment, the client MUST discard all
537 information about the server fetched prior to the initiation of the
538 TLS negotiation and MUST refresh any cached server capabilities
539 information (e.g. from the server's root DSE; see section 3.4 of
540 [Protocol]). This is necessary to protect against active-
541 intermediary attacks that may have altered any server capabilities
542 information retrieved prior to TLS establishment.
544 The server MAY advertise different capabilities after TLS
545 establishment. In particular, the value of supportedSASLMechanisms
546 MAY be different after TLS has been negotiated (specifically, the
547 EXTERNAL mechanism or the proposed PLAIN mechanism are likely to
548 only be listed after a TLS negotiation has been performed).
550 5.2. Effects of TLS on a Client's Authorization Identity
552 This section describes the effects on a client's authorization
553 identity brought about by establishing TLS on an LDAP association.
554 The default effects are described first, and next the facilities for
555 client assertion of authorization identity are discussed including
556 error conditions. Finally, the effects of closing the TLS connection
559 Authorization identities and related concepts are described in
562 5.2.1. Default Effects
564 Upon establishment of the TLS session onto the LDAP association, any
565 previously established authentication and authorization identities
566 MUST remain in force, including anonymous state. This holds even in
567 the case where the server requests client authentication via TLS --
568 e.g. requests the client to supply its certificate during TLS
569 negotiation (see [RFC2246]).
571 5.2.2. Client Assertion of Authorization Identity
573 A client MAY either implicitly request that its LDAP authorization
574 identity be derived from its authenticated TLS credentials or it MAY
575 explicitly provide an authorization identity and assert that it be
576 used in combination with its authenticated TLS credentials. The
577 former is known as an implicit assertion, and the latter as an
580 5.2.2.1. Implicit Assertion
582 An implicit authorization identity assertion is accomplished after
583 TLS establishment by invoking a Bind request of the SASL form using
584 the "EXTERNAL" mechanism name [RFC2222] [Protocol] that SHALL NOT
585 include the optional credentials octet string (found within the
586 SaslCredentials sequence in the Bind Request). The server will
587 derive the client's authorization identity from the authentication
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593 identity supplied in the client's TLS credentials (typically a
594 public key certificate) according to local policy. The underlying
595 mechanics of how this is accomplished are implementation specific.
597 5.2.2.2. Explicit Assertion
599 An explicit authorization identity assertion is accomplished after
600 TLS establishment by invoking a Bind request of the SASL form using
601 the "EXTERNAL" mechanism name [RFC2222] [Protocol] that SHALL
602 include the credentials octet string. This string MUST be
603 constructed as documented in section 4.4.1.
605 5.2.2.3. Error Conditions
607 For either form of assertion, the server MUST verify that the
608 client's authentication identity as supplied in its TLS credentials
609 is permitted to be mapped to the asserted authorization identity.
610 The server MUST reject the Bind operation with an invalidCredentials
611 resultCode in the Bind response if the client is not so authorized.
613 Additionally, with either form of assertion, if a TLS session has
614 not been established between the client and server prior to making
615 the SASL EXTERNAL Bind request and there is no other external source
616 of authentication credentials (e.g. IP-level security [RFC2401]), or
617 if during the process of establishing the TLS session, the server
618 did not request the client's authentication credentials, the SASL
619 EXTERNAL bind MUST fail with a result code of
620 inappropriateAuthentication.
622 After the above Bind operation failures, any client authentication
623 and authorization state of the LDAP association is lost (see
624 [Protocol] section 4.2.1), so the LDAP association is in an
625 anonymous state after the failure. The TLS session state is
626 unaffected, though a server MAY end the TLS session, via a TLS
627 close_notify message, based on the Bind failure (as it MAY at any
630 5.2.3. TLS Connection Closure Effects
632 Closure of the TLS session MUST cause the LDAP association to move
633 to an anonymous authentication and authorization state regardless of
634 the state established over TLS and regardless of the authentication
635 and authorization state prior to TLS session establishment.
637 6. LDAP Association State Transition Tables
639 To comprehensively diagram the various authentication and TLS states
640 through which an LDAP association may pass, this section provides a
641 state transition table to represent a state diagram for the various
642 states through which an LDAP association may pass during the course
643 of its existence and the actions that cause these changes in state.
645 6.1. LDAP Association States
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652 The following table lists the valid LDAP association states and
653 provides a description of each state. The ID for each state is used
654 in the state transition table in section 6.4.
657 -- --------------------------------------------------------------
666 [TLS: Creds Auth ID "I", ON]
675 [TLS: Creds Auth ID "I", ON]
678 [TLS: Creds Auth ID "I", ON]
681 [TLS: Creds Auth ID "I", ON]
683 6.2. Actions that Affect LDAP Association State
685 The following table lists the actions that can affect the state of
686 an LDAP association. The ID for each action is used in the state
687 transition table in section 6.4.
690 -- ------------------------------------------------
691 A1 Client binds anonymously
692 A2 Inappropriate authentication: client attempts an anonymous
693 bind or a bind without supplying credentials to a server that
694 requires the client to provide some form of credentials.
695 A3 Client Start TLS request
696 Server: client auth NOT required
697 A4 Client: Start TLS request
698 Server: client creds requested
699 Client: [TLS creds: Auth ID "I"]
700 A5 Client or Server: send TLS closure alert ([Protocol] section
702 A6 Client: Bind w/simple password or SASL mechanism (e.g. DIGEST-
703 MD5 password, Kerberos, etc. -รป except EXTERNAL [Auth ID "X"
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709 maps to AuthZ ID "Y"]
710 A7 Client Binds SASL EXTERNAL with credentials: AuthZ ID "J"
711 [Explicit Assertion (section 5.2.1.2.2)]
712 A8 Client Bind SASL EXTERNAL without credentials [Implicit
713 Assertion (section 5.2 .1.2.1)]
715 6.3. Decisions Used in Making LDAP Association State Changes
717 Certain changes in the state of an LDAP association are only allowed
718 if the server can affirmatively answer a question. These questions
719 are applied as part of the criteria for allowing or disallowing a
720 state change in the state transition table in section 6.4.
723 -- --------------------------------------------------------------
724 D1 Can TLS Credentials Auth ID "I" be mapped to AuthZ ID "J"?
725 D2 Can a valid AuthZ ID "K" be derived from TLS Credentials Auth
728 6.4. LDAP Association State Transition Table
730 The LDAP Association table below lists the valid states for an LDAP
731 association and the actions that could affect them. For any given
732 row in the table, the Current State column gives the state of an
733 LDAP association, the Action column gives an action that could
734 affect the state of an LDAP assocation, and the Next State column
735 gives the resulting state of an LDAP association after the action
738 The initial state for the state machine described in this table is
742 State Action State Comment
743 ------- ------------- ----- -----------------------------------
745 S1 A2 S1 Error: Inappropriate authentication
749 S1 A7 ? identity could be provided by
750 another underlying mechanism such
752 S1 A8 ? identity could be provided by
753 another underlying mechanism such
756 S2 A2 S2 Error: Inappropriate authentication
759 S2 A7 ? identity could be provided by
760 another underlying mechanism such
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767 S2 A8 ? identity could be provided by
768 another underlying mechanism such
771 S3 A2 S3 Error: Inappropriate authentication
774 S3 A7 and D1=NO S3 Error: InvalidCredentials
776 S3 A8 and D2=NO S3 Error: InvalidCredentials
779 S4 A2 S4 Error: Inappropriate Authentication
784 S4 A7 ? identity could be provided by
785 another underlying mechanism such
787 S4 A8 ? identity could be provided by
788 another underlying mechanism such
791 S5 A2 S5 Error: Inappropriate Authentication
794 S5 A7 ? identity could be provided by
795 another underlying mechanism such
797 S5 A8 ? identity could be provided by
798 another underlying mechanism such
801 S6 A2 S6 Error: Inappropriate Authentication
804 S6 A7 and D1=NO S6 Error: InvalidCredentials
806 S6 A8 and D2=NO S6 Error: InvalidCredentials
809 S7 A2 S7 Error: Inappropriate Authentication
813 S7 A8 and D2=NO S3 Error: InvalidCredentials
816 S8 A2 S8 Error: Inappropriate Authentication
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824 S8 A7 and D1=NO S6 Error: InvalidCredentials
829 7. Anonymous Authentication
831 Directory operations that modify entries or access protected
832 attributes or entries generally require client authentication.
833 Clients that do not intend to perform any of these operations
834 typically use anonymous authentication. Servers SHOULD NOT allow
835 clients with anonymous authentication to modify directory entries or
836 access sensitive information in directory entries.
838 LDAP implementations MUST support anonymous authentication, as
839 defined in section 7.1.
841 LDAP implementations MAY support anonymous authentication with TLS,
842 as defined in section 7.2.
844 While there MAY be access control restrictions to prevent access to
845 directory entries, an LDAP server SHOULD allow an anonymously-bound
846 client to retrieve the supportedSASLMechanisms attribute of the root
849 An LDAP server MAY use other information about the client provided
850 by the lower layers or external means to grant or deny access even
851 to anonymously authenticated clients.
853 7.1. Anonymous Authentication Procedure
855 An LDAPv3 client that has not successfully completed a bind
856 operation on a connection is anonymously authenticated. See section
859 An LDAP client MAY also choose to explicitly bind anonymously. A
860 client that wishes to do so MUST choose the simple authentication
861 option in the Bind Request (see section 4.1) and set the password to
862 be of zero length. (This is often done by LDAPv2 clients.) Typically
863 the name is also of zero length.
865 7.2. Anonymous Authentication and TLS
867 An LDAP client MAY use the Start TLS operation (section 5) to
868 negotiate the use of TLS security [RFC2246]. If the client has not
869 bound beforehand, then until the client uses the EXTERNAL SASL
870 mechanism to negotiate the recognition of the client's certificate,
871 the client is anonymously authenticated.
873 Recommendations on TLS ciphersuites are given in section 10.
875 An LDAP server which requests that clients provide their certificate
876 during TLS negotiation MAY use a local security policy to determine
879 Harrison Expires September 2003 [Page 15]
881 Authentication Methods for LDAPv3
883 whether to successfully complete TLS negotiation if the client did
884 not present a certificate which could be validated.
886 8. Password-based Authentication
888 This section discusses various options for performing password-based
889 authentication to LDAPv3 compliant servers and the environments
890 suitable for their use.
892 8.1. Simple Authentication
894 The LDAP "simple" authentication choice is not suitable for
895 authentication in environments where there is no network or
896 transport layer confidentiality. LDAP implementations SHOULD support
897 authentication with the "simple" authentication choice when the
898 connection is protected against eavesdropping using TLS, as defined
899 in section 5. LDAP implementations SHOULD NOT support authentication
900 with the "simple" authentication choice unless the data on the
901 connection is protected using TLS or other data confidentiality and
902 data integrity protection.
904 8.2. Digest Authentication
906 LDAP servers that implement any password-based authentication method
907 MUST support authentication with a password using the DIGEST-MD5
908 SASL mechanism for password protection.
910 An LDAP client MAY determine whether the server supports this
911 mechanism by performing a search request on the root DSE, requesting
912 the supportedSASLMechanisms attribute, and checking whether the
913 string "DIGEST-MD5" is present as a value of this attribute.
915 In the first stage of authentication, when the client is performing
916 an "initial authentication" as defined in section 2.1 of [RFC2831],
917 the client sends a bind request in which the version number is 3,
918 the authentication choice is sasl, the sasl mechanism name is
919 "DIGEST-MD5", and the credentials are absent. The client then waits
920 for a response from the server to this request.
922 The server will respond with a bind response in which the resultCode
923 is saslBindInProgress, and the serverSaslCreds field is present. The
924 contents of this field is a string defined by "digest-challenge" in
925 section 2.1.1 of [RFC2831]. The server SHOULD include a realm
926 indication and MUST indicate support for UTF-8.
928 The client will send a bind request with a distinct message id, in
929 which the version number is 3, the authentication choice is sasl,
930 the sasl mechanism name is "DIGEST-MD5", and the credentials contain
931 the string defined by "digest-response" in section 2.1.2 of
932 [RFC2831]. The serv-type is "ldap".
934 The server will respond with a bind response in which the resultCode
935 is either success, or an error indication. If the authentication is
936 successful and the server does not support subsequent
938 Harrison Expires September 2003 [Page 16]
940 Authentication Methods for LDAPv3
942 authentication, then the credentials field is absent. If the
943 authentication is successful and the server supports subsequent
944 authentication, then the credentials field contains the string
945 defined by "response-auth" in section 2.1.3 of [RFC2831]. Support
946 for subsequent authentication is OPTIONAL in clients and servers.
948 8.3. "simple" authentication choice under TLS encryption
950 Following the negotiation of an appropriate TLS ciphersuite
951 providing connection confidentiality [RFC2246], a client MAY
952 authenticate to a directory that supports the simple authentication
953 choice by performing a simple bind operation.
955 The client will use the Start TLS operation [Protocol] to negotiate
956 the use of TLS security [RFC2246] on the connection to the LDAP
957 server. The client need not have bound to the directory beforehand.
959 For this authentication procedure to be successful, the client and
960 server MUST negotiate a ciphersuite which contains a bulk encryption
961 algorithm of appropriate strength. Recommendations on cipher suites
962 are given in section 10.
964 Following the successful completion of TLS negotiation, the client
965 MUST send an LDAP bind request with the version number of 3, the
966 name field containing a DN, and the "simple" authentication choice,
967 containing a password.
969 8.3.1. "simple" Authentication Choice
971 DSAs that map the DN sent in the bind request to a directory entry
972 with an associated set of one or more passwords will compare the
973 presented password to the set of passwords associated with that
974 entry. If there is a match, then the server will respond with
975 resultCode success, otherwise the server will respond with
976 resultCode invalidCredentials.
978 8.4. Other authentication choices with TLS
980 It is also possible, following the negotiation of TLS, to perform a
981 SASL authentication that does not involve the exchange of plaintext
982 reusable passwords. In this case the client and server need not
983 negotiate a ciphersuite that provides confidentiality if the only
984 service required is data integrity.
986 9. Certificate-based authentication
988 LDAP server implementations SHOULD support authentication via a
989 client certificate in TLS, as defined in section 5.2.2.
991 9.1. Certificate-based authentication with TLS
993 A user who has a public/private key pair in which the public key has
994 been signed by a Certification Authority may use this key pair to
995 authenticate to the directory server if the user's certificate is
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999 Authentication Methods for LDAPv3
1001 requested by the server. The user's certificate subject field SHOULD
1002 be the name of the user's directory entry, and the Certification
1003 Authority that issued the user's certificate must be sufficiently
1004 trusted by the directory server in order for the server to process
1005 the certificate. The means by which servers validate certificate
1006 paths is outside the scope of this document.
1008 A server MAY support mappings for certificates in which the subject
1009 field name is different from the name of the user's directory entry.
1010 A server which supports mappings of names MUST be capable of being
1011 configured to support certificates for which no mapping is required.
1013 The client will use the Start TLS operation [Protocol] to negotiate
1014 the use of TLS security [RFC2246] on the connection to the LDAP
1015 server. The client need not have bound to the directory beforehand.
1017 In the TLS negotiation, the server MUST request a certificate. The
1018 client will provide its certificate to the server, and the server
1019 MUST perform a private key-based encryption, proving it has the
1020 private key associated with the certificate.
1022 In deployments that require protection of sensitive data in transit,
1023 the client and server MUST negotiate a ciphersuite that contains a
1024 bulk encryption algorithm of appropriate strength. Recommendations
1025 of cipher suites are given in section 10.
1027 The server MUST verify that the client's certificate is valid. The
1028 server will normally check that the certificate is issued by a known
1029 certification authority (CA), and that none of the certificates on
1030 the client's certificate chain are invalid or revoked. There are
1031 several procedures by which the server can perform these checks.
1033 Following the successful completion of TLS negotiation, the client
1034 will send an LDAP bind request with the SASL "EXTERNAL" mechanism.
1036 10. TLS Ciphersuites
1038 The following ciphersuites defined in [RFC2246] MUST NOT be used for
1039 confidentiality protection of passwords or data:
1041 TLS_NULL_WITH_NULL_NULL
1042 TLS_RSA_WITH_NULL_MD5
1043 TLS_RSA_WITH_NULL_SHA
1045 The following ciphersuites defined in [RFC2246] can be cracked
1046 easily (less than a day of CPU time on a standard CPU in 2000).
1047 These ciphersuites are NOT RECOMMENDED for use in confidentiality
1048 protection of passwords or data. Client and server implementers
1049 SHOULD carefully consider the value of the password or data being
1050 protected before using these ciphersuites:
1052 TLS_RSA_EXPORT_WITH_RC4_40_MD5
1053 TLS_RSA_EXPORT_WITH_RC2_CBC_40_MD5
1054 TLS_RSA_EXPORT_WITH_DES40_CBC_SHA
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1058 Authentication Methods for LDAPv3
1060 TLS_DH_DSS_EXPORT_WITH_DES40_CBC_SHA
1061 TLS_DH_RSA_EXPORT_WITH_DES40_CBC_SHA
1062 TLS_DHE_DSS_EXPORT_WITH_DES40_CBC_SHA
1063 TLS_DHE_RSA_EXPORT_WITH_DES40_CBC_SHA
1064 TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
1065 TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA
1067 The following ciphersuites are vulnerable to man-in-the-middle
1068 attacks, and SHOULD NOT be used to protect passwords or sensitive
1069 data, unless the network configuration is such that the danger of a
1070 man-in-the-middle attack is tolerable:
1072 TLS_DH_anon_EXPORT_WITH_RC4_40_MD5
1073 TLS_DH_anon_WITH_RC4_128_MD5
1074 TLS_DH_anon_EXPORT_WITH_DES40_CBC_SHA
1075 TLS_DH_anon_WITH_DES_CBC_SHA
1076 TLS_DH_anon_WITH_3DES_EDE_CBC_SHA
1078 A client or server that supports TLS MUST support
1079 TLS_DHE_DSS_WITH_3DES_EDE_CBC_SHA and MAY support other ciphersuites
1080 offering equivalent or better protection.
1082 11. Security Considerations
1084 Security issues are discussed throughout this memo; the
1085 (unsurprising) conclusion is that mandatory security is important
1086 and that session confidentiality protection is required when
1087 snooping is a problem.
1089 Servers are encouraged to prevent modifications by anonymous users.
1090 Servers may also wish to minimize denial of service attacks by
1091 timing out idle connections, and returning the unwillingToPerform
1092 result code rather than performing computationally expensive
1093 operations requested by unauthorized clients.
1095 Operational experience shows that clients can misuse unauthenticated
1096 access (simple bind with name but no password). For this reason,
1097 servers SHOULD by default reject authentication requests that have a
1098 DN with an empty password with an error of invalidCredentials.
1100 Access control SHOULD be applied when reading sensitive information
1101 or updating directory information.
1103 A connection on which the client has not performed the Start TLS
1104 operation or negotiated a suitable SASL mechanism for connection
1105 integrity and encryption services is subject to man-in-the-middle
1106 attacks to view and modify information in transit.
1108 11.1. Start TLS Security Considerations
1110 The goals of using the TLS protocol with LDAP are to ensure
1111 connection confidentiality and integrity, and to optionally provide
1112 for authentication. TLS expressly provides these capabilities, as
1113 described in [RFC2246].
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1117 Authentication Methods for LDAPv3
1120 All security gained via use of the Start TLS operation is gained by
1121 the use of TLS itself. The Start TLS operation, on its own, does not
1122 provide any additional security.
1124 Once established, TLS only provides for and ensures confidentiality
1125 and integrity of the operations and data in transit over the LDAP
1126 association--and only if the implementations on the client and
1127 server support and negotiate it. The use of TLS does not provide or
1128 ensure for confidentiality and/or non-repudiation of the data housed
1129 by an LDAP-based directory server. Nor does it secure the data from
1130 inspection by the server administrators.
1132 The level of security provided though the use of TLS depends
1133 directly on both the quality of the TLS implementation used and the
1134 style of usage of that implementation. Additionally, an active-
1135 intermediary attacker can remove the Start TLS extended operation
1136 from the supportedExtension attribute of the root DSE. Therefore,
1137 both parties SHOULD independently ascertain and consent to the
1138 security level achieved once TLS is established and before beginning
1139 use of the TLS connection. For example, the security level of the
1140 TLS connection might have been negotiated down to plaintext.
1142 Clients SHOULD either warn the user when the security level achieved
1143 does not provide confidentiality and/or integrity protection, or be
1144 configurable to refuse to proceed without an acceptable level of
1147 Client and server implementors SHOULD take measures to ensure proper
1148 protection of credentials and other confidential data where such
1149 measures are not otherwise provided by the TLS implementation.
1151 Server implementors SHOULD allow for server administrators to elect
1152 whether and when connection confidentiality and/or integrity is
1153 required, as well as elect whether and when client authentication
1154 via TLS is required.
1156 Additional security considerations relating to the EXTERNAL
1157 mechanism to negotiate TLS can be found in [RFC2222] and [RFC2246].
1160 12. Acknowledgements
1162 This document combines information originally contained in RFC 2829
1163 and RFC 2830. The author acknowledges the work of Harald Tveit
1164 Alvestrand, Jeff Hodges, Tim Howes, Steve Kille, RL "Bob" Morgan ,
1165 and Mark Wahl, each of whom authored one or more of these documents.
1166 RFC 2829 and RFC 2830 were products of the IETF LDAPEXT Working
1167 Group. RFC 2251 was a product of the ASID Working Group.
1169 This document is based upon input of the IETF LDAP Revision working
1170 group. The contributions of its members is greatly appreciated.
1172 13. Normative References
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1176 Authentication Methods for LDAPv3
1179 [RFC2119] Bradner, S., "Key Words for use in RFCs to Indicate
1180 Requirement Levels", BCP 14, RFC 2119, March 1997.
1182 [RFC2222] Myers, J., "Simple Authentication and Security Layer
1183 (SASL)", draft-myers-saslrev-xx.txt, a work in progress.
1185 [RFC2234] Crocker, D., Ed. and P. Overell, "Augmented BNF for Syntax
1186 Specifications: ABNF", RFC 2234, November 1997.
1188 [RFC2246] Dierks, T. and C. Allen. "The TLS Protocol Version 1.0",
1189 RFC 2246, January 1999.
1191 [RFC2831] Leach, P. and C. Newman, "Using Digest Authentication as
1192 a SASL Mechanism", RFC 2831, May 2000.
1194 [LDAPDN] Zeilenga, Kurt D. (editor), "LDAP: String Representation of
1195 Distinguished Names", draft-ietf-ldapbis-dn-xx.txt, a work in
1198 [Protocol] Sermersheim, J., "LDAP: The Protocol", draft-ietf-
1199 ldapbis-protocol-xx.txt, a work in progress.
1201 [ROADMAP] K. Zeilenga, "LDAP: Technical Specification Road Map",
1202 draft-ietf-ldapbis-roadmap-xx.txt, a work in progress.
1204 14. Informative References
1206 [RFC2828] Shirey, R., "Internet Security Glossary", RFC 2828, May
1209 [RFC2401] Kent, S. and R. Atkinson, "Security Architecture for the
1210 Internet Protocol", RFC 2401, November 1998.
1213 15. Author's Address
1217 1800 S. Novell Place
1220 roger_harrison@novell.com
1222 16. Full Copyright Statement
1224 Copyright (C) The Internet Society (2000). All Rights Reserved.
1226 This document and translations of it may be copied and furnished to
1227 others, and derivative works that comment on or otherwise explain it
1228 or assist in its implementation may be prepared, copied, published
1229 and distributed, in whole or in part, without restriction of any
1230 kind, provided that the above copyright notice and this paragraph
1231 are included on all such copies and derivative works. However, this
1233 Harrison Expires September 2003 [Page 21]
1235 Authentication Methods for LDAPv3
1237 document itself may not be modified in any way, such as by removing
1238 the copyright notice or references to the Internet Society or other
1239 Internet organizations, except as needed for the purpose of
1240 developing Internet standards in which case the procedures for
1241 copyrights defined in the Internet Standards process must be
1242 followed, or as required to translate it into languages other than
1245 The limited permissions granted above are perpetual and will not be
1246 revoked by the Internet Society or its successors or assigns.
1248 This document and the information contained herein is provided on an
1249 "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING
1250 TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING
1251 BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION
1252 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF
1253 MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE.
1255 Appendix A. Example Deployment Scenarios
1257 The following scenarios are typical for LDAP directories on the
1258 Internet, and have different security requirements. (In the
1259 following discussion, "sensitive data" refers to information whose
1260 disclosure, alteration, destruction, or loss would adversely affect
1261 the interests or business of its owner or user. Also note that there
1262 may be data that is protected but not sensitive.) This is not
1263 intended to be a comprehensive list; other scenarios are possible,
1264 especially on physically protected networks.
1266 (1) A read-only directory, containing no sensitive data, accessible
1267 to "anyone", and TCP connection hijacking or IP spoofing is not
1268 a problem. Anonymous authentication, described in section 7, is
1269 suitable for this type of deployment, and requires no additional
1270 security functions except administrative service limits.
1272 (2) A read-only directory containing no sensitive data; read access
1273 is granted based on identity. TCP connection hijacking is not
1274 currently a problem. This scenario requires data confidentiality
1275 for sensitive authentication information AND data integrity for
1276 all authentication information.
1278 (3) A read-only directory containing no sensitive data; and the
1279 client needs to ensure the identity of the directory server and
1280 that the directory data is not modified while being returned
1281 from the server. A data origin authentication service AND data
1282 integrity service are required.
1284 (4) A read-write directory, containing no sensitive data; read
1285 access is available to "anyone", update access to properly
1286 authorized persons. TCP connection hijacking is not currently a
1287 problem. This scenario requires data confidentiality for
1288 sensitive authentication information AND data integrity for all
1289 authentication information.
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1294 Authentication Methods for LDAPv3
1296 (5) A directory containing sensitive data. This scenario requires
1297 data confidentiality protection AND secure authentication.
1299 Appendix B. Authentication and Authorization: Definitions and Concepts
1301 This appendix defines basic terms, concepts, and interrelationships
1302 regarding authentication, authorization, credentials, and identity.
1303 These concepts are used in describing how various security
1304 approaches are utilized in client authentication and authorization.
1306 B.1. Access Control Policy
1308 An access control policy is a set of rules defining the protection
1309 of resources, generally in terms of the capabilities of persons or
1310 other entities accessing those resources. A common expression of an
1311 access control policy is an access control list. Security objects
1312 and mechanisms, such as those described here, enable the expression
1313 of access control policies and their enforcement. Access control
1314 policies are typically expressed in terms of access control
1315 attributes as described below.
1317 B.2. Access Control Factors
1319 A request, when it is being processed by a server, may be associated
1320 with a wide variety of security-related factors (section 4.2 of
1321 [Protocol]). The server uses these factors to determine whether and
1322 how to process the request. These are called access control factors
1323 (ACFs). They might include source IP address, encryption strength,
1324 the type of operation being requested, time of day, etc. Some
1325 factors may be specific to the request itself, others may be
1326 associated with the connection via which the request is transmitted,
1327 others (e.g. time of day) may be "environmental".
1329 Access control policies are expressed in terms of access control
1330 factors. E.g., a request having ACFs i,j,k can perform operation Y
1331 on resource Z. The set of ACFs that a server makes available for
1332 such expressions is implementation-specific.
1334 B.3. Authentication, Credentials, Identity
1336 Authentication credentials are the evidence supplied by one party to
1337 another, asserting the identity of the supplying party (e.g. a user)
1338 who is attempting to establish an association with the other party
1339 (typically a server). Authentication is the process of generating,
1340 transmitting, and verifying these credentials and thus the identity
1341 they assert. An authentication identity is the name presented in a
1344 There are many forms of authentication credentials -- the form used
1345 depends upon the particular authentication mechanism negotiated by
1346 the parties. For example: X.509 certificates, Kerberos tickets,
1347 simple identity and password pairs. Note that an authentication
1348 mechanism may constrain the form of authentication identities used
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1353 Authentication Methods for LDAPv3
1356 B.4. Authorization Identity
1358 An authorization identity is one kind of access control factor. It
1359 is the name of the user or other entity that requests that
1360 operations be performed. Access control policies are often expressed
1361 in terms of authorization identities; e.g., entity X can perform
1362 operation Y on resource Z.
1364 The authorization identity bound to an association is often exactly
1365 the same as the authentication identity presented by the client, but
1366 it may be different. SASL allows clients to specify an authorization
1367 identity distinct from the authentication identity asserted by the
1368 client's credentials. This permits agents such as proxy servers to
1369 authenticate using their own credentials, yet request the access
1370 privileges of the identity for which they are proxying [RFC2222].
1371 Also, the form of authentication identity supplied by a service like
1372 TLS may not correspond to the authorization identities used to
1373 express a server's access control policy, requiring a server-
1374 specific mapping to be done. The method by which a server composes
1375 and validates an authorization identity from the authentication
1376 credentials supplied by a client is implementation-specific.
1378 Appendix C. RFC 2829 Change History
1380 This appendix lists the changes made to the text of RFC 2829 in
1381 preparing this document.
1383 C.0. General Editorial Changes
1386 - Changed other instances of the term LDAP to LDAPv3 where v3 of
1387 the protocol is implied. Also made all references to LDAPv3 use
1390 - Miscellaneous grammatical changes to improve readability.
1392 - Made capitalization in section headings consistent.
1396 - Changed title to reflect inclusion of material from RFC 2830 and
1399 C.1. Changes to Section 1
1403 - Moved conventions used in document to a separate section.
1405 C.2. Changes to Section 2
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1412 Authentication Methods for LDAPv3
1414 - Moved section to an appendix.
1416 C.3. Changes to Section 3
1420 - Moved section to an appendix.
1422 C.4 Changes to Section 4
1426 - Changed "Distinguished Name" to "LDAP distinguished name".
1428 C.5. Changes to Section 5
1432 - Added the following sentence: "Servers SHOULD NOT allow clients
1433 with anonymous authentication to modify directory entries or
1434 access sensitive information in directory entries."
1436 C.5.1. Changes to Section 5.1
1440 - Replaced the text describing the procedure for performing an
1441 anonymous bind (protocol) with a reference to section 4.2 of RFC
1442 2251 (the protocol spec).
1446 - Brought text describing procedure for performing an anonymous
1447 bind from section 4.2 of RFC 2251 bis. This text will be
1448 removed from the draft standard version of that document.
1450 C.6. Changes to Section 6.
1454 Reorganized text in section 6.1 as follows:
1456 1. Added a new section (6.1) titled "Simple Authentication" and
1457 moved one of two introductory paragraphs for section 6 into
1458 section 6.1. Added sentences to the paragraph indicating:
1460 a. simple authentication is not suitable for environments where
1461 confidentiality is not available.
1463 b. LDAP implementations SHOULD NOT support simple
1464 authentication unless confidentiality and data integrity
1465 mechanisms are in force.
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1471 Authentication Methods for LDAPv3
1473 2. Moved first paragraph of section 6 (beginning with "LDAP
1474 implementations MUST support authentication with a passwordร ")
1475 to section on Digest Authentication (Now section 6.2).
1477 C.6.1. Changes to Section 6.1.
1479 Version -00 Renamed section to 6.2
1481 - Added sentence from original section 6 indicating that the
1482 DIGEST-MD5 SASL mechanism is required for all conforming LDAPv3
1485 C.6.2. Changes to Section 6.2
1489 - Renamed section to 6.3
1491 - Reworded first paragraph to remove reference to user and the
1492 userPassword password attribute Made the first paragraph more
1493 general by simply saying that if a directory supports simple
1494 authentication that the simple bind operation MAY performed
1495 following negotiation of a TLS ciphersuite that supports
1498 - Replaced "the name of the user's entry" with "a DN" since not
1499 all bind operations are performed on behalf of a "user."
1501 - Added Section 6.3.1 heading just prior to paragraph 5.
1503 - Paragraph 5: replaced "The server" with "DSAs that map the DN
1504 sent in the bind request to a directory entry with a
1505 userPassword attribute."
1507 C.6.3. Changes to section 6.3.
1511 - Renamed to section 6.4.
1513 C.7. Changes to section 7.
1517 C.7.1. Changes to section 7.1.
1521 - Clarified the entity issuing a certificate by moving the phrase
1522 "to have issued the certificate" immediately after
1523 "Certification Authority."
1525 C.8. Changes to section 8.
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1530 Authentication Methods for LDAPv3
1534 - Removed the first paragraph because simple authentication is
1535 covered explicitly in section 6.
1537 - Added section 8.1. heading just prior to second paragraph.
1539 - Added section 8.2. heading just prior to third paragraph.
1541 - Added section 8.3. heading just prior to fourth paragraph.
1545 - Moved entire section 8 of RFC 2829 into section 3.4 (Using SASL
1546 for Other Security Services) to bring material on SASL
1547 mechanisms together into one location.
1549 C.9. Changes to section 9.
1553 - Paragraph 2: changed "EXTERNAL mechanism" to "EXTERNAL SASL
1556 - Added section 9.1. heading.
1558 - Modified a comment in the ABNF from "unspecified userid" to
1559 "unspecified authz id".
1561 - Deleted sentence, "A utf8string is defined to be the UTF-8
1562 encoding of one or more ISO 10646 characters," because it is
1565 - Added section 9.1.1. heading.
1567 - Added section 9.1.2. heading.
1571 - Moved entire section 9 to become section 3.5 so that it would be
1572 with other SASL material.
1574 C.10. Changes to Section 10.
1578 - Updated reference to cracking from a week of CPU time in 1997 to
1579 be a day of CPU time in 2000.
1581 - Added text: "These ciphersuites are NOT RECOMMENDED for use...
1582 and server implementers SHOULD" to sentence just prior the
1583 second list of ciphersuites.
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1589 Authentication Methods for LDAPv3
1591 - Added text: "and MAY support other ciphersuites offering
1592 equivalent or better protection," to the last paragraph of the
1595 C.11. Changes to Section 11.
1599 - Moved to section 3.6 to be with other SASL material.
1601 C.12. Changes to Section 12.
1605 - Inserted new section 12 that specifies when SASL protections
1606 begin following SASL negotiation, etc. The original section 12
1607 is renumbered to become section 13.
1611 - Moved to section 3.7 to be with other SASL material.
1613 C.13. Changes to Section 13 (original section 12).
1617 Appendix D. RFC 2830 Change History
1619 This appendix lists the changes made to the text of RFC 2830 in
1620 preparing this document.
1622 D.0. General Editorial Changes
1624 - Material showing the PDUs for the Start TLS response was broken
1625 out into a new section.
1627 - The wording of the definition of the Start TLS request and Start
1628 TLS response was changed to make them parallel. NO changes were
1629 made to the ASN.1 definition or the associated values of the
1632 - A separate section heading for graceful TLS closure was added
1633 for parallelism with section on abrupt TLS closure.
1635 Appendix E. RFC 2251 Change History
1637 This appendix lists the changes made to the text of RFC 2251 in
1638 preparing this document.
1640 E.0. General Editorial Changes
1642 - All material from section 4.2 of RFC 2251 was moved into this
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1648 Authentication Methods for LDAPv3
1650 - A new section was created for the Bind Request
1652 - Section 4.2.1 of RFC 2251 (Sequencing Bind Request) was moved
1653 after the section on the Bind Response for parallelism with the
1654 presentation of the Start TLS operations. The section was also
1655 subdivided to explicitly call out the various effects being
1656 described within it.
1658 - All SASL profile information from RFC 2829 was brought within
1659 the discussion of the Bind operation (primarily sections 4.4 -
1662 Appendix F. Change History to Combined Document
1664 F.1. Changes for draft-ldap-bis-authmeth-02
1668 - Added references to other LDAP standard documents, to sections
1669 within the document, and fixed broken references.
1671 - General editorial changesรนpunctuation, spelling, formatting,
1676 - Added glossary of terms and added sub-section headings
1680 - Clarified security mechanisms 3, 4, & 5 and brought language in
1681 line with IETF security glossary.
1685 - Brought language in requirement (3) in line with security
1688 - Clarified that information fetched prior to initiation of TLS
1689 negotiation must be discarded
1691 -Clarified that information fetched prior to initiation of SASL
1692 negotiation must be discarded
1694 - Rewrote paragraph on SASL negotiation requirements to clarify
1699 - Added stipulation that sasl choice allows for any SASL mechanism
1700 not prohibited by this document. (Resolved conflict between this
1701 statement and one that prohibited use of ANONYMOUS and PLAIN
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1707 Authentication Methods for LDAPv3
1711 - Added a.x.bar.com to wildcard matching example on hostname
1716 - Added LDAP Association State Transition Tables to show the
1717 various states through which an LDAP association may pass along
1718 with the actions and decisions required to traverse from state
1723 - Brought security terminology in line with IETF security glossary
1724 throughout the appendix.
1726 F.2. Changes for draft-ldap-bis-authmeth-03
1730 - Added introductory notes and changed title of document and
1731 references to conform to WG chair suggestions for the overall
1732 technical specification.
1734 - Several issues--G.13, G.14, G.16, G.17--were resolved without
1735 requiring changes to the document.
1739 - Removed reference to /etc/passwd file and associated text.
1743 - Removed sections 4.1, 4.2 and parts of section 4.3. This
1744 information was being duplicated in the protocol specification
1745 and will now reside there permanently.
1748 - changed words, "not recommended" to "strongly discouraged"
1752 - Based on ldapbis WG discussion at IETF52 two sentences were
1753 added indicating that clients SHOULD NOT send a DN value when
1754 binding with the sasl choice and servers SHALL ignore any value
1755 received in this circumstance.
1760 - Generalized the language of this section to not refer to any
1761 specific password attribute or to refer to the directory entry
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1766 Authentication Methods for LDAPv3
1771 - Added security consideration regarding misuse of unauthenticated
1774 - Added security consideration requiring access control to be
1775 applied only to authenticated users and recommending it be
1776 applied when reading sensitive information or updating directory
1780 F.3. Changes for draft-ldap-bis-authmeth-04
1784 - Changed references to use [RFCnnnn] format wherever possible.
1785 (References to works in progress still use [name] format.)
1786 - Various edits to correct typos and bring field names, etc. in
1787 line with specification in [Protocol] draft.
1789 - Several issues--G.13, G.14, G.16, G.17--were resolved without
1790 requiring changes to the document.
1794 - Changed ABNF grammar to use productions that are like those in
1799 - Removed sections 5.1, 5.2, and 5.4 that will be added to
1800 [Protocol]. Renumbered sections to accommodate this change.
1805 - Reviewed LDAP Association State table for completeness and
1806 accuracy. Renumbered actions A3, A4, and A5 to be A5, A3, and A4
1807 respectively. Re-ordered several lines in the table to ensure
1808 that actions are in ascending order (makes analyzing the table
1809 much more logical). Added action A2 to several states where it
1810 was missing and valid. Added actions A7 and A8 placeholders to
1811 states S1, S2, S4 and S5 pending resolution of issue G.28.
1815 - Modified security consideration (originally added in -03)
1816 requiring access control to be applied only to authenticated
1817 users. This seems nonsensical because anonymous users may have
1818 access control applied to limit permissible actions.
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1825 Authentication Methods for LDAPv3
1827 - Verified all normative references and moved informative
1828 references to a new section 14.
1830 F.4. Changes for draft-ldap-bis-authmeth-05
1834 - General editory changes to fix punctuation, spelling, line
1836 - Verified and updated intra- and inter-document references
1838 - Document-wide review for proper usage of RFC 2119 keywords with
1839 several changes to correct improper usage.
1842 - Updated to match current contents of documents. This was needed
1843 due to movement of material on Bind and Start TLS operations to
1844 [Protocol] in this revision.
1848 - Renamed section to "Rationale for LDAPv3 Security Mechanisms"
1849 and removed text that did not support this theme. Part of the
1850 motivation for this change was to remove the implication of the
1851 previous section title, "Required Security Mechanisms", and
1852 other text found in the section that everything in the section
1855 - Information from several removed paragraphs that describe
1856 deployment scenarios will be added Appendix A in the next
1857 revision of the draft.
1860 - Paragraph beginning, " If TLS is negotiated, the client MUST
1861 discard all information..." was moved to section 5.1.7 and
1862 integrated with related material there.
1864 - Paragraph beginning, "If a SASL security layer is negotiated..."
1865 was moved to section 4.2
1869 - Changed wording of first paragraph to clarify meaning.
1872 - Added paragraph from section 3 of -04 beginning, "If a SASL
1873 security layer is negotiated..."
1876 - Renamed to "Other SASL Mechanisms" and completely rewrote the
1877 section (one sentence) to generalize the treatment of SASL
1878 mechanisms not explicitly mentioned in this document.
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1884 Authentication Methods for LDAPv3
1887 - Added paragraph beginning, "The dnAuthzID choice allows client
1888 applications..." to clarify whether DN form authorization
1889 identities have to also have a corresponding directory entry.
1890 This change was based on editor's perception of WG consensus.
1892 - Made minor clarifying edits in the paragraph beginning, "The
1893 uAuthzID choice allows for compatibility..."
1897 - Made minor clarifying edits in the last paragraph of the
1902 - Wording from section 3 paragraph beginning " If TLS is
1903 negotiated, the client MUST discard all information..." was
1904 moved to this section and integrated with existing text.
1908 - Changed usage of "TLS connection" to "TLS session" throughout.
1910 - Removed empty section 5.2.1 and renumbered sections it had
1911 previously contained.
1915 - Added introductory paragraph at beginning of section.
1919 - Changed term "data privacy" to "data confidentiality" to be
1920 consistent with usage in rest of document.
1924 - Changed first paragraph to require implementations that
1925 implement *password-based* authentication to implement and
1926 support DIGEST-MD5 SASL authentication.
1930 - First paragraph: changed "session encryption" to "session
1931 confidentiality protection" to be consistent with usage in rest
1936 - Began changes to incorporate information on deployment scenarios
1937 removed from section 3.
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1943 Authentication Methods for LDAPv3
1945 Appendix G. Issues to be Resolved
1947 This appendix lists open questions and issues that need to be
1948 resolved before work on this document is deemed complete.
1952 Section 1 lists 6 security mechanisms that can be used by LDAP
1953 servers. I'm not sure what mechanism 5, "Resource limitation by
1954 means of administrative limits on service controls" means.
1956 Status: resolved. Changed wording to "administrative service limits"
1961 Section 2 paragraph 1 defines the term, "sensitive." Do we want to
1962 bring this term and other security-related terms in alignment with
1963 usage with the IETF security glossary (RFC 2828)?
1965 Status: resolved. WG input at IETF 51 was that we should do this, so
1966 the appropriate changes have been made.
1970 Section 2, deployment scenario 2: What is meant by the term "secure
1971 authentication function?"
1973 Status: resolved. Based on the idea that a "secure authentication
1974 function" could be provided by TLS, I changed the wording to require
1975 data confidentiality for sensitive authentication information and
1976 data integrity for all authentication information.
1980 Section 3, deployment scenario 3: What is meant by the phrase,
1981 "directory data is authenticated by the server?"
1983 Status: resolved. I interpreted this to mean the ability to ensure
1984 the identity of the directory server and the integrity of the data
1985 sent from that server to the client, and explictly stated such.
1989 Section 4 paragraph 3: What is meant by the phrase, "this means that
1990 either this data is useless for faking authentication (like the Unix
1991 "/etc/passwd" file format used to be)?"
1993 Status: resolved. Discussion at IETF 52 along with discussions with
1994 the original authors of this material have convinced us that this
1995 reference is simply too arcane to be left in place. In -03 the text
1996 has been modified to focus on the need to either update password
1997 information in a protected fashion outside of the protocol or to
2000 Harrison Expires September 2003 [Page 34]
2002 Authentication Methods for LDAPv3
2004 update it in session well protected against snooping, and the
2005 reference to /etc/passwd has been removed.
2009 Section 4 paragraph 7 begins: "For a directory needing session
2010 protection..." Is this referring to data confidentiality or data
2013 Status: resolved. Changed wording to say, "For a directory needing
2014 data security (both data integrity and data confidentiality)..."
2018 Section 4 paragraph 8 indicates that "information about the server
2019 fetched fetched prior to the TLS negotiation" must be discarded. Do
2020 we want to explicitly state that this applies to information fetched
2021 prior to the *completion* of the TLS negotiation or is this going
2024 Status: resolved. Based on comments in the IETF 51 LDAPBIS WG
2025 meeting, this has been changed to explicitly state, "fetched prior
2026 to the initiation of the TLS negotiation..."
2030 Section 4 paragraph 9 indicates that clients SHOULD check the
2031 supportedSASLMechanisms list both before and after a SASL security
2032 layer is negotiated to ensure that they are using the best available
2033 security mechanism supported mutually by the client and server. A
2034 note at the end of the paragraph indicates that this is a SHOULD
2035 since there are environments where the client might get a list of
2036 supported SASL mechanisms from a different trusted source.
2038 I wonder if the intent of this could be restated more plainly using
2039 one of these two approaches (I've paraphrased for the sake of
2042 Approach 1: Clients SHOULD check the supportedSASLMechanisms
2043 list both before and after SASL negotiation or clients SHOULD
2044 use a different trusted source to determine available supported
2047 Approach 2: Clients MUST check the supportedSASLMechanisms list
2048 both before and after SASL negotiation UNLESS they use a
2049 different trusted source to determine available supported SASL
2052 Status: resolved. WG input at IETF 51 was that Approach 1 was
2053 probably best. I ended up keeping the basic structure similar to the
2054 original to meet this intent.
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2061 Authentication Methods for LDAPv3
2063 Section 6.3.1 states: "DSAs that map the DN sent in the bind request
2064 to a directory entry with a userPassword attribute will... compare
2065 [each value in the named user's entry]... with the presented
2066 password." This implies that this applies only to user entries with
2067 userPassword attributes. What about other types of entries that
2068 might allow passwords and might store in the password information in
2069 other attributes? Do we want to make this text more general?
2071 Status: resolved in -03 draft by generalizing section 8.3.1 to not
2072 refer to any specific password attribute and by removing the term
2073 "user" in referring to the directory entry specified by the DN in
2076 G.10 userPassword and simple bind
2078 We need to be sure that we don't require userPassword to be the only
2079 attribute used for authenticating via simple bind. (See 2251 sec 4.2
2080 and authmeth 6.3.1. Work with Jim Sermersheim on resolution to this.
2081 On publication state something like: "This is the specific
2082 implementation of what we discussed in our general reorg
2083 conversation on the list." (Source: Kurt Zeilenga)
2085 Status: resolved in -03 draft by generalizing section 8.3.1 to not
2086 refer to any specific password attribute and by removing the term
2087 "user" in referring to the directory entry specified by the DN in
2090 G.11. Meaning of LDAP Association
2092 The original RFC 2830 uses the term "LDAP association" in describing
2093 a connection between an LDAP client and server regardless of the
2094 state of TLS on that connection. This term needs to be defined or
2097 Status: resolved. at IETF 51 Bob Morgan indicated that the term
2098 "LDAP association" was intended to distinguish the LDAP-level
2099 connection from the TLS-level connection. This still needs to be
2100 clarified somewhere in the draft. Added "LDAP association" to a
2101 glossary in section 1.
2103 G.12. Is DIGEST-MD5 mandatory for all implementations?
2105 Reading 2829bis I think DIGEST-MD5 is mandatory ONLY IF your server
2106 supports password based authentication...but the following makes it
2107 sound mandatory to provide BOTH password authentication AND DIGEST-
2110 "6.2. Digest authentication
2112 LDAP implementations MUST support authentication with a password
2113 using the DIGEST-MD5 SASL mechanism for password protection, as
2114 defined in section 6.1."
2116 The thing is for acl it would be nice (though not critical) to be
2118 Harrison Expires September 2003 [Page 36]
2120 Authentication Methods for LDAPv3
2122 able to default the required authentication level for a subject to a
2123 single "fairly secure" mechanism--if there is no such mandatory
2124 authentication scheme then you cannot do that. (Source: Rob Byrne)
2126 Status: resolved. -00 version of the draft added a sentence at the
2127 beginning of section 8.2 stating that LDAP server implementations
2128 must support this method.
2130 G.13. Ordering of authentication levels requested
2132 Again on the subject of authentication level, is it possible to
2133 define an ordering on authentication levels which defines their
2134 relative "strengths" ? This would be useful in acl as you could say
2135 things like"a given aci grants access to a given subject at this
2136 authentication level AND ABOVE". David Chadwick raised this before
2137 in the context of denying access to a subject at a given
2138 authentication level, in which case he wanted to express "deny
2139 access to this subject at this authentication level AND TO ALL
2140 IDENTITIES AUTHENTICATED BELOW THAT LEVEL". (Source: Rob Byrne)
2142 Status: out of scope. This is outside the scope of this document and
2143 will not be addressed.
2145 G.14. Document vulnerabilities of various mechanisms
2147 While I'm here...in 2829, I think it would be good to have some
2148 comments or explicit reference to a place where the security
2149 properties of the particular mandatory authentication schemes are
2150 outlined. When I say "security properties" I mean stuff like "This
2151 scheme is vulnerable to such and such attacks, is only safe if the
2152 key size is > 50, this hash is widely considered the best, etc...".
2153 I think an LDAP implementor is likely to be interested in that
2154 information, without having to wade through the security RFCs.
2157 Status: out of scope. This is outside the scope of this document and
2158 will not be addressed.
2160 G.15. Include a StartTLS state transition table
2162 The pictoral representation it is nominally based on is here (URL
2165 http://www.stanford.edu/~hodges/doc/LDAPAssociationStateDiagram-
2168 (Source: Jeff Hodges)
2170 Status: In Process. Table provided in -03. Review of content for
2171 accuracy in -04. Additional review is needed, plus comments from WG
2172 members indicate that additional description of each state's meaning
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2179 Authentication Methods for LDAPv3
2181 G.16. Empty sasl credentials question
2183 I spent some more time looking microscopically at ldap-auth-methods
2184 and ldap-ext-tls drafts. The drafts say that the credential must
2185 have the form dn:xxx or u:xxx or be absent, and although they don't
2186 say what to do in the case of an empty octet string I would say that
2187 we could send protocolError (claim it is a bad PDU).
2189 There is still the question of what to do if the credential is 'dn:'
2190 (or 'u:') followed by the empty string. (Source: ariel@columbia.edu
2193 Status: resolved. Kurt Zeilenga indicated during ldapbis WG
2194 discussion at IETF 52 that SASL AuthzID credentials empty and absent
2195 are equivalent in the latest SASL ID. This resolves the issue.
2197 G.17. Hostname check from MUST to SHOULD?
2199 I am uneasy about the hostname check. My experience from PKI with
2200 HTTP probably is a contributing factor; we have people using the
2201 short hostname to get to a server which naturally has the FQDN in
2202 the certificate, no end of problems. I have a certificate on my
2203 laptop which has the FQDN for the casse when the system is on our
2204 Columbia network with a fixed IP; when I dial in however, I have
2205 some horrible dialup name, and using the local https server becomes
2206 annoying. Issuing a certificate in the name 'localhost' is not a
2207 solution! Wildcard match does not solve this problem. For these
2208 reasons I am inclined to argue for 'SHOULD' instead of
2209 'MUST' in paragraph...
2211 Also, The hostname check against the name in the certificate is a
2212 very weak means of preventing man-in-the-middle attacks; the proper
2213 solution is not here yet (SecureDNS or some equivalent). Faking out
2214 DNS is not so hard, and we see this sort of thing in the press on a
2215 pretty regular basis, where site A hijacks the DNS server for site B
2216 and gets all their requests. Some mention of this should be made in
2217 the draft. (Source: ariel@columbia.edu via Jeff Hodges)
2219 Status: resolved. Based on discussion at IETF 52 ldapbis WG meeting,
2220 this text will stand as it is. The check is a MUST, but the behavior
2221 afterward is a SHOULD. This gives server implementations the room to
2224 G.18. Must SASL DN exist in the directory?
2226 If the 'dn:' form of sasl creds is used, is it the intention of the
2227 draft(ers) that this DN must exist in the directory and the client
2228 will have the privileges associated with that entry, or can the
2229 server map the sasl DN to perhaps some other DN in the directory,
2230 in an implementation-dependent fashion?
2232 We already know that if *no* sasl credentials are presented, the DN
2233 or altname in the client certificate may be mapped to a DN in an
2234 implementation-dependent fashion, or indeed to something not in the
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2238 Authentication Methods for LDAPv3
2240 directory at all. (Right?) (Source: ariel@columbia.edu via Jeff
2243 Status: resolved. (11/12/02)Based on my research I propose that the
2244 DN MUST exist in the directory when the DN form of sasl creds is
2245 used. I have made this proposal to the ldapbis mailing list.
2247 (11/21/02) Feedback from mailing list has proposed removing this
2248 paragraph entirely because (1) explicit assertion of authorization
2249 identity should only be done when proxying (2) mapping of the
2250 asserted authorization identity is implementation specific and
2251 policy driven [SASL] section 4.2, and (3) keeping this paragraph is
2252 not required for interoperability.
2254 G.19. DN used in conjunction with SASL mechanism
2256 We need to specify whether the DN field in Bind operation can/cannot
2257 be used when SASL mechanism is specified. (source: RL Bob)
2259 Status: resolved. (-03) Based on ldapbis WG discussion at IETF52 two
2260 sentences were added to section 4.3 indicating that clients SHOULD
2261 NOT send a DN value when binding with the sasl choice and servers
2262 SHALL ignore any value received in this circumstance. During edits
2263 for -04 version of draft it was noted that [Protocol] section 4.2
2264 conflicts with this draft. The editor of [Protocol] has been
2265 notified of the discrepancy, and they have been handled.
2269 Differences between unauthenticated and anonymous. There are four
2270 states you can get into. One is completely undefined (this is now
2271 explicitly called out in [Protocol]). This text needs to be moved
2272 from [Protocol] to this draft. (source: Jim Sermersheim)
2274 Status: Resolved. There are four states: (1) no name, no password
2275 (anon); (2) name, no password (anon); (3) no name, password
2276 (invalid); (4) name, password (simple bind). States 1, 2, and 4 are
2277 called out in [AuthMeth]. State 3 is called out in [Protocol]; this
2278 seems appropriate based on review of alternatives.
2280 G.21. Misuse of unauthenticated access
2282 Add a security consideration that operational experience shows that
2283 clients can misuse unauthenticated access (simple bind with name but
2284 no password). Servers SHOULD by default reject authentication
2285 requests that have a DN with an empty password with an error of
2286 invalidCredentials. (Source: Kurt Zeilenga and Chris Newman (Sun))
2288 Status: Resolved. Added to security considerations in รป03.
2290 G.22. Need to move StartTLS protocol information to [Protocol]
2292 Status: Resolved. Removed Sections 5.1, 5.2, and 5.4 for -04 and
2293 they are [Protocol] -11.
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2297 Authentication Methods for LDAPv3
2300 G.23. Split Normative and Non-normative references into separate
2303 Status: Resolved. Changes made in -04
2305 G.24. What is the authentication state if a Bind operation is
2308 Status: In process. (11/12/02) This text was suggested to be added
2309 to [Protocol] -11 to cover what happens if a bind operation is
2312 "If a server receives an Abandon request for a Bind operation, the
2313 server SHOULD leave the connection in the anonymous state. Clients
2314 that abandon a Bind operation MUST rebind after abandoning the Bind
2315 request in order to have a known authentication state on the
2318 (11/21/02) Jim Sermersheim prposed the following wording on the
2319 ldapbis mail list: "Authentication from earlier binds are
2320 subsequently ignored. A failed or abandoned Bind Operation has the
2321 effect of leaving the connection in an anonymous state. Clients MUST
2322 rebind after abandoning a bind operation in order to determine a
2323 known authentication state."
2325 Once this is resolved in [Protocol] the state table in section 6 of
2326 [AuthMeth] will need to be updated to reflect the consensus wording.
2328 G.25. Difference between checking server hostname and server's
2329 canonical DNS name in Server Identity Check?
2331 Section 5.1.6: I now understand the intent of the check (prevent
2332 man-in-the-middle attacks). But what is the subtle difference
2333 between the "server hostname" and the "server's canonical DNS name"?
2336 Status: In Process. (11/12/02) Sent suggested wording change to this
2337 paragraph to the ldapbis mail list and also asked for opinion as to
2338 whether we should discuss the distinction between server DNS
2339 hostname and server canonical DNS hostname in [AuthMeth].
2341 (11/21/02): RL Bob Morgan will provide wording that allows
2342 derivations of the name that are provided securely.
2344 6.26. Server Identity Check using servers located via SRV records
2346 Section 5.1.6: What should be done if the server was found using SRV
2347 records based on the "locate" draft/RFC? (Source: Tim Hahn).
2349 Status: Resolved. Section 5 of draft-ietf-ldapext-locate-08
2350 specifically calls out how the server identity should be performed
2351 if the server is located using the method defined in that draft.
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2356 Authentication Methods for LDAPv3
2358 This is the right location for this information, and the coverage
2359 appears to be adequate.
2361 G.27 Inconsistency in effect of TLS closure on LDAP association.
2363 Section 5.4.1 of authmeth -03 (section 4.1 of RFC2830) states that
2364 TLS closure alert will leave the LDAP association intact. Contrast
2365 this with Section 5.5.2 (section 5.2 of RFC2830) that says that the
2366 closure of the TLS connection MUST cause the LDAP association to
2367 move to an anonymous authentication.
2369 Status: in process. (11/12/02) This is actually a [Protocol] issue
2370 because these sections have now been moved to [Protocol] -11. I have
2371 proposed the following text for Section 5.4.1 of [AuthMeth] -03
2372 (section 4.13.3.1 of [Protocol]) to resolve this apparent
2375 "Either the client or server MAY terminate the TLS connection on an
2376 LDAP association by sending a TLS closure alert. The LDAP
2377 connection remains open for further communication after TLS closure
2378 occurs although the authentication state of the LDAP connection is
2379 affected (see [AuthMeth] section 5.2.2).
2381 (11/21/02): resolution to this is expected in [Protocol] -12
2383 G.28 Ordering of external sources of authorization identities
2385 Section 4.3.2 implies that external sources of authorization
2386 identities other than TLS are permitted. What is the behavior when
2387 two external sources of authentication credentials are available
2388 (e.g. TLS and IPsec are both present (is this possible?)) and a SASL
2389 EXTERNAL Bind operation is performed?
2391 Status: resolved. 11/20/02: Resolved by Section 4.2 of [SASL] which
2392 states that the decision to allow or disallow the asserted identity
2393 is based on an implementation defined policy.
2395 G.29 Rewrite of Section 10, TLS Ciphersuites
2397 This section contains anachronistic references and needs to be
2398 updated/rewritten in a way that provides useful guidance for future
2399 readers in a way that will transcend the passage of time.
2401 G.30 Update to Appendix A, Example Deployment Scenarios
2403 This section needs to be updated to indicate which security
2404 mechanisms and/or combinations of security mechanisms described
2405 elsewhere in the document can provide the types of protections
2406 suggested in this appendix.
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