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diff --git a/source4/heimdal/doc/standardisation/draft-zhu-kerb-enctype-nego-00.txt b/source4/heimdal/doc/standardisation/draft-zhu-kerb-enctype-nego-00.txt new file mode 100644 index 00000000000..35d2f070961 --- /dev/null +++ b/source4/heimdal/doc/standardisation/draft-zhu-kerb-enctype-nego-00.txt @@ -0,0 +1,560 @@ + + +NETWORK WORKING GROUP L. Zhu +Internet-Draft P. Leach +Expires: June 4, 2005 K. Jaganathan + Microsoft Corporation + December 2004 + + + Kerberos Cryptosystem Negotiation Extension + draft-zhu-kerb-enctype-nego-00 + +Status of this Memo + + This document is an Internet-Draft and is subject to all provisions + of Section 3 of RFC 3667. By submitting this Internet-Draft, each + author represents that any 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 become aware will be disclosed, in accordance with + RFC 3668. + + Internet-Drafts are working documents of the Internet Engineering + Task Force (IETF), its areas, and its working groups. Note that + other groups may also distribute working documents as + Internet-Drafts. + + Internet-Drafts are draft documents valid for a maximum of six months + and may be updated, replaced, or obsoleted by other documents at any + time. It is inappropriate to use Internet-Drafts as reference + material or to cite them other than as "work in progress." + + The list of current Internet-Drafts can be accessed at + http://www.ietf.org/ietf/1id-abstracts.txt. + + The list of Internet-Draft Shadow Directories can be accessed at + http://www.ietf.org/shadow.html. + + This Internet-Draft will expire on June 4, 2005. + +Copyright Notice + + Copyright (C) The Internet Society (2004). + +Abstract + + This document specifies an extension by Kerberos to negotiate new + encryption types between the client-server peers. + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 1] + +Internet-Draft Enctype Negotiation December 2004 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Conventions Used in This Document . . . . . . . . . . . . . 4 + 3. Negotiation Protocol . . . . . . . . . . . . . . . . . . . . 5 + 4. Security Considerations . . . . . . . . . . . . . . . . . . 6 + 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . 7 + 6. Normative References . . . . . . . . . . . . . . . . . . . . 7 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 7 + A. Leveraging this Enctype Negotiation in Windows SPNEGO + Implementations . . . . . . . . . . . . . . . . . . . . . . 9 + Intellectual Property and Copyright Statements . . . . . . . 10 + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 2] + +Internet-Draft Enctype Negotiation December 2004 + + +1. Introduction + + Under the current mechanism [CLAR], the KDC must limit the ticket + session key enctype chosen for a given service to one it believes is + supported by both the client and the server. If both the client and + server understand a stronger enctype than is selected by the KDC, + they can not negotiate it. As the result, the protection of + application traffic is often weaker than necessary when different + application software that support different set of enctypes can be + used by the same server principal. + + This document specifies an extension to Kerberos to allow clients and + servers to negotiate a different and possible stronger cryptosystem + to be used in subsequent communication. + + This extension utilizes an authorization data element in the + authenticator of the KRB_AP_REQ message [CLAR]. The client sends the + list of enctypes that it supports to the server, the server then + informs the client its choice. The negotiated subkey is sent in the + KRB_AP_REP. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 3] + +Internet-Draft Enctype Negotiation December 2004 + + +2. Conventions Used in This Document + + The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", + "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this + document are to be interpreted as described in [RFC2119]. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 4] + +Internet-Draft Enctype Negotiation December 2004 + + +3. Negotiation Protocol + + If the client prefers an enctype over that of the service ticket + session key, then it MUST send the list of enctypes it supports + (including the one selected by the KDC), in decreasing preference + order. + + The client sends the enctype list via the authorization-data of the + authenticator in the KRB_AP_REQ [CLAR]. A new authorization data + element type AD-ETYPE-NEGOTIATION (129) is defined. This + authorization data element itself is enclosed in the AD-IF-RELEVANT + container, thus a correctly implemented server that does not + understand this element should ignore it [CLAR]. The value of this + authorization element contains the DER [X60] encoding of the + following ASN.1 type: + + EtypeList ::= SEQUENCE OF Int32 + -- the client's proposed enctype list in decreasing + -- preference order, favorite choice first + + If the EtypeList is present and the server prefers an enctype from + the client's enctype list over that of the KRB_AP_REQ authenticator + subkey (if that is present) or the service ticket session key, the + server MUST create a subkey using that enctype. This negotiated + subkey is sent in the subkey field of KRB_AP_REP message and it MUST + be used for subsequent communication. + + Note that to preserve the quality of randomness provided by the KDC, + implementations of this protocol SHOULD consider using the service + ticket session key value as a source of additional entropy when + generating the negotiated subkey. If the KRB_AP_REQ authenticator + subkey is present, it MAY also be used as a source of entropy. + + The policy by which the client or the server chooses an enctype + (i.e., how the preference order for the supported enctypes is + selected) is an implementation-specific local matter. + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 5] + +Internet-Draft Enctype Negotiation December 2004 + + +4. Security Considerations + + The client's enctype list and the server's reply enctype are part of + encrypted data, thus the security considerations are the same as + those of the Kerberos encrypted data. + + In all cases, the communicating peers are exposed to the denial of + service threat. + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 6] + +Internet-Draft Enctype Negotiation December 2004 + + +5. IANA Considerations + + No IANA actions are required for this document. + +6. Normative References + + [CLAR] Neuman, B., Yu, Y., Hartman, S. and K. Raeburn, "The + Kerberos Network Authentication Service (V5)", August + 2004. + + [GSS-CFX] Zhu, L., Jaganathan, K. and S. Hartman, "The Kerberos + Version 5 GSS-API Mechanism: Version 2", November 2004. + + [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate + Requirement Levels", BCP 14, RFC 2119, March 1997. + + [RFC2743] Linn, J., "Generic Security Service Application Program + Interface Version 2, Update 1", RFC 2743, January 2000. + + [SPNEGOBIS] + Zhu, L., Leach, P., Jaganathan, K., Hartman, S. and W. + Ingersoll, "The Simple and Protected GSS-API Negotiation + Mechanism", November 2004. + + +Authors' Addresses + + Larry Zhu + Microsoft Corporation + One Microsoft Way + Redmond, WA 98052 + US + + Email: lzhu@microsoft.com + + + Paul Leach + Microsoft Corporation + One Microsoft Way + Redmond, WA 98052 + US + + Email: paulle@microsoft.com + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 7] + +Internet-Draft Enctype Negotiation December 2004 + + + Karthik Jaganathan + Microsoft Corporation + One Microsoft Way + Redmond, WA 98052 + US + + Email: karthikj@microsoft.com + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 8] + +Internet-Draft Enctype Negotiation December 2004 + + +Appendix A. Leveraging this Enctype Negotiation in Windows SPNEGO + Implementations + + The SPNEGO implementations in Windows 2000, Windows XP and Windows + 2003 do not generate or verify the mechlistMIC field when it is + required [SPNEGOBIS]. + + When the SPNEGO implementations that are updated according to + [SPNEGOBIS], an SSPI initiator or acceptor needs to determine if the + peer is updated, so that it can generate the mechlistMIC token when + the peer can process it. With the bidirectional negotiation, the + updated SPNEGO implementation can achieve the following two goals: + + o It can remain backward compatible with legacy implementations, if + local policy allows unsafe and unprotected negotiation with + downlevel implementations when the mechlistMIC token exchange + would otherwise be required by [SPNEGOBIS]. + o The mechanism negotiation is protected according to [SPNEGOBIS] + when both peers are updated. + + However, the updated SPNEGO implementation itself can not securely + inform the peer whether the local implementation is updated, thus it + has to obtain such information from the negotiated mechanism. + + For Windows SPNEGO implementations, both the initiator and the + acceptor are assumed to have been updated if a "newer" [CLAR] or + different enctype is negotiated for use by the Kerberos GSS-API + mechanism. + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires June 4, 2005 [Page 9] + +Internet-Draft Enctype Negotiation December 2004 + + +Intellectual Property Statement + + The IETF takes no position regarding the validity or scope of any + Intellectual Property Rights or other rights that might be claimed to + pertain to the implementation or use of the technology described in + this document or the extent to which any license under such rights + might or might not be available; nor does it represent that it has + made any independent effort to identify any such rights. Information + on the procedures with respect to rights in RFC documents can be + found in BCP 78 and BCP 79. + + Copies of IPR disclosures made to the IETF Secretariat and any + assurances of licenses to be made available, or the result of an + attempt made to obtain a general license or permission for the use of + such proprietary rights by implementers or users of this + specification can be obtained from the IETF on-line IPR repository at + http://www.ietf.org/ipr. + + The IETF invites any interested party to bring to its attention any + copyrights, patents or patent applications, or other proprietary + rights that may cover technology that may be required to implement + this standard. Please address the information to the IETF at + ietf-ipr@ietf.org. + + +Disclaimer of Validity + + This document and the information contained herein are provided on an + "AS IS" basis and THE CONTRIBUTOR, THE ORGANIZATION HE/SHE REPRESENTS + OR IS SPONSORED BY (IF ANY), THE INTERNET SOCIETY AND THE INTERNET + ENGINEERING TASK FORCE DISCLAIM ALL WARRANTIES, EXPRESS OR IMPLIED, + INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE + INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED + WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. + + +Copyright Statement + + Copyright (C) The Internet Society (2004). This document is subject + to the rights, licenses and restrictions contained in BCP 78, and + except as set forth therein, the authors retain all their rights. + + +Acknowledgment + + Funding for the RFC Editor function is currently provided by the + Internet Society. + + + + +Zhu, et al. Expires June 4, 2005 [Page 10] + + |