draft-ietf-krb-wg-anon-04.txt   draft-ietf-krb-wg-anon-05.txt 
NETWORK WORKING GROUP L. Zhu NETWORK WORKING GROUP L. Zhu
Internet-Draft P. Leach Internet-Draft P. Leach
Updates: 4120 (if approved) Microsoft Corporation Updates: 4120 (if approved) Microsoft Corporation
Intended status: Standards Track July 7, 2007 Intended status: Standards Track January 27, 2008
Expires: January 8, 2008 Expires: July 30, 2008
Anonymity Support for Kerberos Anonymity Support for Kerberos
draft-ietf-krb-wg-anon-04 draft-ietf-krb-wg-anon-05
Status of this Memo Status of this Memo
By submitting this Internet-Draft, each author represents that any By submitting this Internet-Draft, each author represents that any
applicable patent or other IPR claims of which he or she is aware applicable patent or other IPR claims of which he or she is aware
have been or will be disclosed, and any of which he or she becomes have been or will be disclosed, and any of which he or she becomes
aware will be disclosed, in accordance with Section 6 of BCP 79. aware will be disclosed, in accordance with Section 6 of BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF), its areas, and its working groups. Note that Task Force (IETF), its areas, and its working groups. Note that
skipping to change at page 1, line 35 skipping to change at page 1, line 35
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The list of current Internet-Drafts can be accessed at The list of current Internet-Drafts can be accessed at
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This Internet-Draft will expire on January 8, 2008. This Internet-Draft will expire on July 30, 2008.
Copyright Notice Copyright Notice
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
Abstract Abstract
This document defines extensions to the Kerberos protocol for the This document defines extensions to the Kerberos protocol for the
Kerberos client to authenticate the Kerberos Key Distribution Center Kerberos client to authenticate the Kerberos Key Distribution Center
and the Kerberos server, without revealing the client's identity. and the Kerberos server, without revealing the client's identity. It
These extensions can be used to secure communication between the updates RFC 4120. These extensions can be used to secure
anonymous client and the server. communication between the anonymous client and the server.
Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions Used in This Document . . . . . . . . . . . . . . 3 2. Conventions Used in This Document . . . . . . . . . . . . . . 3
3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Definitions . . . . . . . . . . . . . . . . . . . . . . . . . 3
4. Protocol Description . . . . . . . . . . . . . . . . . . . . . 4 4. Protocol Description . . . . . . . . . . . . . . . . . . . . . 4
5. GSS-API Implementation Notes . . . . . . . . . . . . . . . . . 8 5. GSS-API Implementation Notes . . . . . . . . . . . . . . . . . 7
6. Security Considerations . . . . . . . . . . . . . . . . . . . 8 6. Security Considerations . . . . . . . . . . . . . . . . . . . 8
7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9 7. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 9
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
9. Normative References . . . . . . . . . . . . . . . . . . . . . 10 9. Normative References . . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 10
Intellectual Property and Copyright Statements . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . . . . 11
1. Introduction 1. Introduction
In certain situations, the Kerberos [RFC4120] client may wish to In certain situations, the Kerberos [RFC4120] client may wish to
authenticate a server and/or protect communications without revealing authenticate a server and/or protect communications without revealing
its own identity. For example, consider an application which its own identity. For example, consider an application which
provides read access to a research database, and which permits provides read access to a research database, and which permits
queries by arbitrary requestors. A client of such a service might queries by arbitrary requestors. A client of such a service might
wish to authenticate the service, to establish trust in the wish to authenticate the service, to establish trust in the
information received from it, but might not wish to disclose its information received from it, but might not wish to disclose its
identity to the service for privacy reasons. identity to the service for privacy reasons.
Extensions to [RFC4120] are specified in this document by which a Extensions to Kerberos are specified in this document by which a
client can authenticate the Key Distribution Center (KDC) and request client can authenticate the Key Distribution Center (KDC) and request
an anonymous ticket. The client can use the anonymous ticket to an anonymous ticket. The client can use the anonymous ticket to
authenticate the server and protect subsequent client-server authenticate the server and protect subsequent client-server
communications. These extensions provide Kerberos with functional communications.
equivalence to Transport Layer Security (TLS) [RFC4346].
By using the extensions defined in this specification, the client may By using the extensions defined in this specification, the client may
reveal its identity in its initial request to its own KDC, but it can reveal its identity in its initial request to its own KDC, but it can
remain anonymous thereafter to KDCs on the cross-realm authentication remain anonymous thereafter to KDCs on the cross-realm authentication
path, and to the server with which it communicates. path, and to the server with which it communicates.
2. Conventions Used in This Document 2. Conventions Used in This Document
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 [RFC2119]. document are to be interpreted as described in [RFC2119].
3. Definitions 3. Definitions
The anonymous Kerberos realm name is defined as a well-known realm The anonymous Kerberos realm name is defined as a well-known realm
name based on [KRBNAM]. The value is the literal "WELLKNOWN: name based on [KRBNAM]. The value is the literal "WELLKNOWN:
ANONYMOUS". An anonymous Kerberos realm name MUST NOT be present in ANONYMOUS". An anonymous Kerberos realm name MUST NOT be present in
the transited field [RFC4120] of a ticket. the transited field of a ticket.
The anonymous Kerberos principal name is defined as a well-known The anonymous Kerberos principal name is defined as a well-known
Kerberos principal name based on [KRBNAM]. The value of the name- Kerberos principal name based on [KRBNAM]. The value of the name-
type field [RFC4120] is KRB_NT_WELLKNOWN [KRBNAM], and the value of type field is KRB_NT_WELLKNOWN [KRBNAM], and the value of the name-
the name-string field [RFC4120] is a sequence of two KerberosString string field is a sequence of two KerberosString components:
components: "WELLKNOWN", "ANONYMOUS". "WELLKNOWN", "ANONYMOUS".
Note that in this specification, the anonymous principal name and Note that in this specification, the anonymous principal name and
realm are only applicable to the client in Kerberos messages, the realm are only applicable to the client in Kerberos messages, the
server MUST NOT be anonymous in any Kerberos message. server MUST NOT be anonymous in any Kerberos message.
The anonymous ticket flag is defined as bit 14 (with the first bit The anonymous ticket flag is defined as bit 14 (with the first bit
being bit 0) in the TicketFlags: being bit 0) in the TicketFlags:
TicketFlags ::= KerberosFlags TicketFlags ::= KerberosFlags
-- anonymous(14) -- anonymous(14)
-- TicketFlags and KerberosFlags are defined in [RFC4120] -- TicketFlags and KerberosFlags are defined in [RFC4120]
An anonymous ticket is a ticket that has all of the following An anonymous ticket is a ticket that has all of the following
properties: properties:
o The cname field [RFC4120] contains the anonymous Kerberos o The cname field contains the anonymous Kerberos principal name.
principal name.
o The crealm field [RFC4120] contains the client's realm name, or o The crealm field contains the client's realm name, or the name of
the name of the realm that issued the initial ticket for the the realm that issued the initial ticket for the client principal,
client principal, or the anonymous realm name. or the anonymous realm name.
o The anonymous ticket contains no information that can reveal the o The anonymous ticket contains no information that can reveal the
client's identity. However the ticket may contain the client client's identity. However the ticket may contain the client
realm, intermediate realms on the client's authentication path, realm, intermediate realms on the client's authentication path,
and authorization data that may provide information related to the and authorization data that may provide information related to the
client's identity. For example, an anonymous principal that is client's identity. For example, an anonymous principal that is
identifiable only within a particular group of users can be identifiable only within a particular group of users can be
implemented using authorization data and such authorization data, implemented using authorization data and such authorization data,
if included in the anonymous ticket, shall disclose the client's if included in the anonymous ticket, shall disclose the client's
membership of that group. membership of that group.
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-- anonymous(14) -- anonymous(14)
-- KDCOptions and KerberosFlags are defined in [RFC4120] -- KDCOptions and KerberosFlags are defined in [RFC4120]
As described in Section 4, the anonymous KDC option is set to request As described in Section 4, the anonymous KDC option is set to request
an anonymous ticket. an anonymous ticket.
4. Protocol Description 4. Protocol Description
In order to request an anonymous ticket, the client sets the In order to request an anonymous ticket, the client sets the
anonymous KDC option in an Authentication Exchange (AS) or Ticket anonymous KDC option in an Authentication Exchange (AS) or Ticket
Granting Service (TGS) request [RFC4120]. The client can request an Granting Service (TGS) request. The client can request an anonymous
anonymous Ticket Granting Ticket (TGT) based on a normal TGT. Unless Ticket Granting Ticket (TGT) based on a normal TGT. Unless otherwise
otherwise specified, the client can obtain an anonymous ticket with specified, the client can obtain an anonymous ticket with the
the anonymous realm name only by requesting an anonymous ticket in an anonymous realm name only by requesting an anonymous ticket in an AS
AS exchange with the client realm set as anonymous in the request. exchange with the client realm set as anonymous in the request.
If the client wishes to authenticate the KDC anonymously, it sets the If the client wishes to authenticate the KDC anonymously, it sets the
client name as anonymous in the AS exchange and provides a client name as anonymous in the AS exchange and provides a
PA_PK_AS_REQ pre-authentication data [RFC4556] where both the PA_PK_AS_REQ pre-authentication data [RFC4556] where both the
signerInfos field and the certificates field of the SignedData signerInfos field and the certificates field of the SignedData
[RFC3852] of the PA_PK_AS_REQ are empty. Because the anonymous [RFC3852] of the PA_PK_AS_REQ are empty. Because the anonymous
client does not have an associated asymmetric key pair, the client client does not have an associated asymmetric key pair, the client
MUST choose the Diffie-Hellman key agreement method by filling in the MUST choose the Diffie-Hellman key agreement method by filling in the
Diffie-Hellman domain parameters in the clientPublicValue [RFC4556]. Diffie-Hellman domain parameters in the clientPublicValue [RFC4556].
If the ticket in the PA-TGS-REQ [RFC4120] of the TGS request is If the ticket in the PA-TGS-REQ of the TGS request is anonymous, or
anonymous, or if the client in the AS request is anonymous, the if the client in the AS request is anonymous, the anonymous KDC
anonymous KDC option MUST be set in the request. Otherwise, the KDC option MUST be set in the request. Otherwise, the KDC MUST return a
MUST return a KRB-ERROR message with the code KDC_ERR_BADOPTION KRB-ERROR message with the code KDC_ERR_BADOPTION.
[RFC4120], and there is no accompanying e-data defined in this
document.
Upon receiving the AS request with a PA_PK_AS_REQ [RFC4556] from the Upon receiving the AS request with a PA_PK_AS_REQ [RFC4556] from the
anonymous client, the KDC processes the request according to Section anonymous client, the KDC processes the request according to Section
3.1.2 of [RFC4120]. The KDC skips the checks for the client's 3.1.2 of [RFC4120]. The KDC skips the checks for the client's
signature and the client's public key (such as the verification of signature and the client's public key (such as the verification of
the binding between the client's public key and the client name), but the binding between the client's public key and the client name), but
performs otherwise-applicable checks, and proceeds as normal performs otherwise-applicable checks, and proceeds as normal
according to [RFC4556]. For example, the AS MUST check if the according to [RFC4556]. For example, the AS MUST check if the
client's Diffie-Hellman domain parameters are acceptable. The client's Diffie-Hellman domain parameters are acceptable. The
Diffie-Hellman key agreement method MUST be used and the reply key is Diffie-Hellman key agreement method MUST be used and the reply key is
derived according to Section 3.2.3.1 of [RFC4556]. If the derived according to Section 3.2.3.1 of [RFC4556]. If the
clientPublicValue is not present in the request, the KDC MUST return clientPublicValue is not present in the request, the KDC MUST return
a KRB-ERROR [RFC4120] with the code a KRB-ERROR with the code KDC_ERR_PUBLIC_KEY_ENCRYPTION_NOT_SUPPORTED
KDC_ERR_PUBLIC_KEY_ENCRYPTION_NOT_SUPPORTED [RFC4556] and there is no [RFC4556]. If all goes well, an anonymous ticket is generated
accompanying e-data. If all goes well, an anonymous ticket is according to Section 3.1.3 of [RFC4120] and a PA_PK_AS_REP [RFC4556]
generated according to Section 3.1.3 of [RFC4120] and a PA_PK_AS_REP pre-authentication data is included in the KDC reply according to
[RFC4556] pre-authentication data is included in the KDC reply [RFC4556]. If the KDC does not have an asymmetric key pair, it MAY
according to [RFC4556]. If the KDC does not have an asymmetric key reply anonymously or reject the authentication attempt. If the KDC
pair, it MAY reply anonymously or reject the authentication attempt. replies anonymously, both the signerInfos field and the certificates
If the KDC replies anonymously, both the signerInfos field and the field of the SignedData [RFC3852] of PA_PK_AS_REP in the reply are
certificates field of the SignedData [RFC3852] of PA_PK_AS_REP in the empty. The server name in the anonymous KDC reply contains the name
reply are empty. The server name in the anonymous KDC reply contains of the TGS.
the name of the TGS.
Upon receipt of the KDC reply that contains an anonymous ticket and a Upon receipt of the KDC reply that contains an anonymous ticket and a
PA_PK_AS_REP [RFC4556] pre-authentication data, the client can then PA_PK_AS_REP [RFC4556] pre-authentication data, the client can then
authenticate the KDC based on the KDC's signature in the authenticate the KDC based on the KDC's signature in the
PA_PK_AS_REP. If the KDC's signature is missing in the KDC reply PA_PK_AS_REP. If the KDC's signature is missing in the KDC reply
(the reply is anonymous), the client MUST reject the returned ticket (the reply is anonymous), the client MUST reject the returned ticket
if it cannot authenticate the KDC otherwise. if it cannot authenticate the KDC otherwise.
The client can use the client keys to mutually authenticate with the The client can use the client keys to mutually authenticate with the
KDC, request an anonymous TGT in the AS request. And in that case, KDC, request an anonymous TGT in the AS request. And in that case,
the reply key is selected as normal according to Section 3.1.3 of the reply key is selected as normal according to Section 3.1.3 of
[RFC4120]. [RFC4120].
For the TGS exchange, the reply key is selected as normal according For the TGS exchange, the reply key is selected as normal according
to Section 3.3.3 of [RFC4120]. to Section 3.3.3 of [RFC4120].
When policy allows, the KDC issues an anonymous ticket. Based on When policy allows, the KDC issues an anonymous ticket. Based on
local policy, the client realm in the anonymous ticket can be the local policy, the client realm in the anonymous ticket can be the
anonymous realm name or the realm of the KDC. However, in all cases, anonymous realm name or the realm of the KDC. However, in all cases,
the client name and the client realm in the EncKDCRepPart of the the client name and the client realm in the EncTicketPart of the
reply [RFC4120] MUST match with the corresponding client name and the reply MUST match with the corresponding client name and the client
client realm of the anonymous ticket in the reply. The client MUST realm of the anonymous ticket in the reply. The client MUST use the
use the client name and the client realm returned in the client name and the client realm returned in the KDC-REP in
EncKDCRepPart in subsequent message exchanges when using the obtained subsequent message exchanges when using the obtained anonymous
anonymous ticket. ticket.
When propagating authorization data in the ticket or in the enc- When propagating authorization data in the ticket or in the enc-
authorization-data field [RFC4120] of the request, the TGS MUST authorization-data field of the request, the TGS MUST ensure that the
ensure that the client confidentiality is not violated in the client confidentiality is not violated in the returned anonymous
returned anonymous ticket. The TGS MUST process the authorization ticket. The TGS MUST process the authorization data recursively
data recursively according to Section 5.2.6 of [RFC4120] beyond the according to Section 5.2.6 of [RFC4120] beyond the container levels
container levels such that all embedded authorization elements are such that all embedded authorization elements are interpreted.
interpreted. Identity-based authorization data SHOULD NOT be present Identity-based authorization data SHOULD NOT be present in an
in an anonymous ticket in that it typically reveals the client's anonymous ticket in that it typically reveals the client's identity.
identity. The specification of a new authorization data type MUST The specification of a new authorization data type MUST specify the
specify the processing rules of the authorization data when an processing rules of the authorization data when an anonymous ticket
anonymous ticket is returned. If there is no processing rule defined is returned. If there is no processing rule defined for an
for an authorization data element or the authorization data element authorization data element or the authorization data element is
is unknown, the TGS MUST process it when an anonymous ticket is unknown, the TGS MUST process it when an anonymous ticket is returned
returned as follows: as follows:
o If the authorization data element may reveal the client's o If the authorization data element may reveal the client's
identity, it MUST be removed unless otherwise specified. identity, it MUST be removed unless otherwise specified.
o If the authorization data element is intended to restrict the use o If the authorization data element is intended to restrict the use
of the ticket or limit the rights otherwise conveyed in the of the ticket or limit the rights otherwise conveyed in the
ticket, it cannot be removed in order to hide the client's ticket, it cannot be removed in order to hide the client's
identity. In this case, the authentication attempt MUST be identity. In this case, the authentication attempt MUST be
rejected, and the KDC MUST return an error message with the code rejected, and the KDC MUST return an error message with the code
KDC_ERR_POLICY [RFC4120]. There is no accompanying e-data defined KDC_ERR_POLICY. Note this is applicable to both critical and
in this document. Note this is applicable to both critical and
optional authorization data. optional authorization data.
o If the authorization data element is unknown, the TGS MAY remove o If the authorization data element is unknown, the TGS MAY remove
it, or transfer it into the returned anonymous ticket, or reject it, or transfer it into the returned anonymous ticket, or reject
the authentication attempt, based on local policy for that the authentication attempt, based on local policy for that
authorization data type unless otherwise specified. If there is authorization data type unless otherwise specified. If there is
no policy defined for a given unknown authorization data type, the no policy defined for a given unknown authorization data type, the
authentication MUST be rejected. The error code is KDC_ERR_POLICY authentication MUST be rejected. The error code is KDC_ERR_POLICY
when the authentication is rejected. when the authentication is rejected.
The AD-INITIAL-VERIFIED-CAS authorization data [RFC4556] MAY be The AD-INITIAL-VERIFIED-CAS authorization data [RFC4556] MAY be
removed from an anonymous ticket based on local policy of the TGS. removed from an anonymous ticket based on local policy of the TGS.
The TGS MUST add the name of the previous realm according to Section The TGS MUST add the name of the previous realm according to Section
3.3.3.2 of [RFC4120]. If the client's realm is the anonymous realm, 3.3.3.2 of [RFC4120]. If the client's realm is the anonymous realm,
the abbreviation forms [RFC4120] that build on the preceding name the abbreviation forms that build on the preceding name cannot be
cannot be used at the start of the transited encoding. The null- used at the start of the transited encoding. The null-subfield form
subfield form (e.g., encoding ending with ",") [RFC4120] could not be (e.g., encoding ending with ",") could not be used next to the
used next to the anonymous realm that can potentially be at the anonymous realm that can potentially be at the beginning where the
beginning where the client realm is filled in. client realm is filled in.
The KDC fills out the authtime field of the anonymous ticket in the
reply as follows: If the anonymous ticket is returned in an AS
exchange, the authtime field of the ticket contains the request time.
If the anonymous ticket is returned in a TGS exchange, the authtime
field contains the authtime of the ticket in the PA-TGS-REQ pre-
authentication data [RFC4120]. An anonymous ticket can be renewed,
and the authtime field of a renewed ticket is the authtime in the
anonymous ticket on which the renewed ticket was based.
If the client is anonymous and the KDC does not have a key to encrypt If the client is anonymous and the KDC does not have a key to encrypt
the reply (this can happen when, for example, the KDC does not the reply (this can happen when, for example, the KDC does not
support PKINIT [RFC4556]), the KDC MUST return an error message with support PKINIT [RFC4556]), the KDC MUST return an error message with
the code KDC_ERR_NULL_KEY [RFC4120] and there is no accompanying the code KDC_ERR_NULL_KEY [RFC4120].
e-data defined in this document.
If a client requires anonymous communication then the client MUST If a client requires anonymous communication then the client MUST
check to make sure that the ticket in the reply is actually anonymous check to make sure that the ticket in the reply is actually anonymous
by checking the presence of the anonymous ticket flag. This is by checking the presence of the anonymous ticket flag. This is
because KDCs ignore unknown KDC options. A KDC that does not because KDCs ignore unknown KDC options. A KDC that does not
understand the anonymous KDC option will not return an error, but understand the anonymous KDC option will not return an error, but
will instead return a normal ticket. will instead return a normal ticket.
The subsequent client and server communications then proceed as The subsequent client and server communications then proceed as
described in [RFC4120]. described in [RFC4120].
skipping to change at page 8, line 44 skipping to change at page 8, line 26
name as defined in Section 2.1.3 of [RFC1964] MUST signify the realm name as defined in Section 2.1.3 of [RFC1964] MUST signify the realm
name according to Section 2.1.1 of [RFC1964]. Note that in this name according to Section 2.1.1 of [RFC1964]. Note that in this
specification only the client/initiator can be anonymous. specification only the client/initiator can be anonymous.
Portable initiators are RECOMMENDED to use default credentials Portable initiators are RECOMMENDED to use default credentials
whenever possible, and request anonymity only through the input whenever possible, and request anonymity only through the input
anon_req_flag [RFC2743] to GSS_Init_Sec_Context(). anon_req_flag [RFC2743] to GSS_Init_Sec_Context().
6. Security Considerations 6. Security Considerations
Since KDCs ignore unknown options [RFC4120], a client requiring Since KDCs ignore unknown options, a client requiring anonymous
anonymous communication needs to make sure that the ticket is communication needs to make sure that the ticket is actually
actually anonymous. This is because a KDC that that does not anonymous. This is because a KDC that that does not understand the
understand the anonymous option would not return an anonymous ticket. anonymous option would not return an anonymous ticket.
By using the mechanism defined in this specification, the client does By using the mechanism defined in this specification, the client does
not reveal its identity to the server but its identity may be not reveal its identity to the server but its identity may be
revealed to the KDC of the server principal (when the server revealed to the KDC of the server principal (when the server
principal is in a different realm than that of the client), and any principal is in a different realm than that of the client), and any
KDC on the cross-realm authentication path. The Kerberos client MUST KDC on the cross-realm authentication path. The Kerberos client MUST
verify the ticket being used is indeed anonymous before communicating verify the ticket being used is indeed anonymous before communicating
with the server, otherwise the client's identity may be revealed with the server, otherwise the client's identity may be revealed
unintentionally. unintentionally.
skipping to change at page 9, line 25 skipping to change at page 9, line 8
If the KDC that issued an anonymous ticket were to maintain records If the KDC that issued an anonymous ticket were to maintain records
of the association of identities to an anonymous ticket, then someone of the association of identities to an anonymous ticket, then someone
obtaining such records could breach the anonymity. Additionally, the obtaining such records could breach the anonymity. Additionally, the
implementations of most (for now all) KDC's respond to requests at implementations of most (for now all) KDC's respond to requests at
the time that they are received. Traffic analysis on the connection the time that they are received. Traffic analysis on the connection
to the KDC will allow an attacker to match client identities to to the KDC will allow an attacker to match client identities to
anonymous tickets issued. Because there are plaintext parts of the anonymous tickets issued. Because there are plaintext parts of the
tickets that are exposed on the wire, such matching by a third party tickets that are exposed on the wire, such matching by a third party
observer is relatively straightforward. observer is relatively straightforward.
The client's real identity is not revealed when the client is
authenticated as the anonymous principal. Application servers MAY
reject the authentication in order to, for example, prevent
information disclosure or as part of Denial of Service (DOS)
prevention. Application servers MUST avoid accepting anonymous
credentials in situations where they must record the client's
identity; for example, when there must be an audit trail.
7. Acknowledgements 7. Acknowledgements
JK Jaganathan helped editing early revisions of this document. JK Jaganathan helped editing early revisions of this document.
Clifford Neuman contributed the core notions of this document. Clifford Neuman contributed the core notions of this document.
Ken Raeburn reviewed the document and provided suggestions for Ken Raeburn reviewed the document and provided suggestions for
improvements. improvements.
Martin Rex wrote the text for GSS-API considerations. Martin Rex wrote the text for GSS-API considerations.
Nicolas Williams reviewed the GSS-API considerations section and Nicolas Williams reviewed the GSS-API considerations section and
suggested ideas for improvements. suggested ideas for improvements.
Sam Hartman and Nicolas Williams were great champions of this work. Sam Hartman and Nicolas Williams were great champions of this work.
In addition, the following individuals made significant In addition, the following individuals made significant
contributions: Jeffery Altman, Tom Yu, Chaskiel M Grundman, Love contributions: Jeffrey Altman, Tom Yu, Chaskiel M Grundman, Love
Hoernquist Aestrand, and Jeffery Hutzelman. Hornquist Astrand, Jeffrey Hutzelman, and Olga Kornievskaia.
8. IANA Considerations 8. IANA Considerations
Section 3 defines the anonymous Kerberos name and the anonymous Section 3 defines the anonymous Kerberos name and the anonymous
Kerberos realm based on [KRBNAM]. The IANA registry for [KRBNAM] Kerberos realm based on [KRBNAM]. The IANA registry for [KRBNAM]
need to be updated to add references to this document. need to be updated to add references to this document.
9. Normative References 9. Normative References
[KRBNAM] Zhu, L., "Additonal Kerberos Naming Contraints", [KRBNAM] Zhu, L., "Additonal Kerberos Naming Contraints",
skipping to change at page 10, line 26 skipping to change at page 10, line 18
[RFC2743] Linn, J., "Generic Security Service Application Program [RFC2743] Linn, J., "Generic Security Service Application Program
Interface Version 2, Update 1", RFC 2743, January 2000. Interface Version 2, Update 1", RFC 2743, January 2000.
[RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)", [RFC3852] Housley, R., "Cryptographic Message Syntax (CMS)",
RFC 3852, July 2004. RFC 3852, July 2004.
[RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The [RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The
Kerberos Network Authentication Service (V5)", RFC 4120, Kerberos Network Authentication Service (V5)", RFC 4120,
July 2005. July 2005.
[RFC4346] Dierks, T. and E. Rescorla, "The Transport Layer Security
(TLS) Protocol Version 1.1", RFC 4346, April 2006.
[RFC4556] Zhu, L. and B. Tung, "Public Key Cryptography for Initial [RFC4556] Zhu, L. and B. Tung, "Public Key Cryptography for Initial
Authentication in Kerberos (PKINIT)", RFC 4556, June 2006. Authentication in Kerberos (PKINIT)", RFC 4556, June 2006.
Authors' Addresses Authors' Addresses
Larry Zhu Larry Zhu
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
US US
skipping to change at page 11, line 7 skipping to change at page 11, line 7
Paul Leach Paul Leach
Microsoft Corporation Microsoft Corporation
One Microsoft Way One Microsoft Way
Redmond, WA 98052 Redmond, WA 98052
US US
Email: paulle@microsoft.com Email: paulle@microsoft.com
Full Copyright Statement Full Copyright Statement
Copyright (C) The IETF Trust (2007). Copyright (C) The IETF Trust (2008).
This document is subject to the rights, licenses and restrictions This document is subject to the rights, licenses and restrictions
contained in BCP 78, and except as set forth therein, the authors contained in BCP 78, and except as set forth therein, the authors
retain all their rights. retain all their rights.
This document and the information contained herein are provided on an This document and the information contained herein are provided on an
"AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS
OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY, THE IETF TRUST AND
THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS THE INTERNET ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS
OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF
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