From 824d5f69bec6c921680de87b025df20b911c36e3 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Love=20H=C3=B6rnquist=20=C3=85strand?= Date: Tue, 14 Jun 2005 03:33:48 +0000 Subject: [PATCH] x git-svn-id: svn://svn.h5l.se/heimdal/trunk/heimdal@15374 ec53bebd-3082-4978-b11e-865c3cabbd6b --- .../draft-zhu-kerb-enctype-nego-01.txt | 395 ++++++++++++++++++ 1 file changed, 395 insertions(+) create mode 100644 doc/standardisation/draft-zhu-kerb-enctype-nego-01.txt diff --git a/doc/standardisation/draft-zhu-kerb-enctype-nego-01.txt b/doc/standardisation/draft-zhu-kerb-enctype-nego-01.txt new file mode 100644 index 000000000..60be49b7a --- /dev/null +++ b/doc/standardisation/draft-zhu-kerb-enctype-nego-01.txt @@ -0,0 +1,395 @@ + + +NETWORK WORKING GROUP L. Zhu +Internet-Draft P. Leach +Expires: October 2, 2005 K. Jaganathan + Microsoft Corporation + March 31, 2005 + + + Kerberos Cryptosystem Negotiation Extension + draft-zhu-kerb-enctype-nego-01 + +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 October 2, 2005. + +Copyright Notice + + Copyright (C) The Internet Society (2005). + +Abstract + + This document specifies an extension by Kerberos to negotiate new + encryption types between the client-server peers. + + + + + + +Zhu, et al. Expires October 2, 2005 [Page 1] + +Internet-Draft Enctype Negotiation March 2005 + + +Table of Contents + + 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Conventions Used in This Document . . . . . . . . . . . . . . 3 + 3. Negotiation Extension . . . . . . . . . . . . . . . . . . . . 3 + 4. Security Considerations . . . . . . . . . . . . . . . . . . . 4 + 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 + 6. Normative References . . . . . . . . . . . . . . . . . . . . . 4 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . 5 + A. Leveraging this Enctype Negotiation in Windows SPNEGO + Implementations . . . . . . . . . . . . . . . . . . . . . . . 5 + Intellectual Property and Copyright Statements . . . . . . . . 7 + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + + +Zhu, et al. Expires October 2, 2005 [Page 2] + +Internet-Draft Enctype Negotiation March 2005 + + +1. Introduction + + Under the current mechanism [CLAR], the KDC must limit the ticket + session key enctype chosen for a given server to one it believes is + supported by both the client and the server. If both the client and + server understand a stronger enctype than the one selected by the + KDC, they can not negotiate it. As the result, the protection of + application traffic is often weaker than necessary when the server + can support different sets of enctypes depending on the server + application software being used. + + 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 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 + AP-REP message [CLAR]. + +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]. + +3. Negotiation Extension + + 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 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 + -- Specifies the enctypes supported by the client. + -- This enctype list is in decreasing preference order + -- (favorite choice first). + -- Int32 is defined in [CLAR]. + + + + +Zhu, et al. Expires October 2, 2005 [Page 3] + +Internet-Draft Enctype Negotiation March 2005 + + + If the EtypeList is present and the server prefers an enctype from + the client's enctype list over that of the 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 AP-REP message and it MUST be + used for subsequent communication. + + This negotiation extension MUST NOT be used when the client does not + expect the subkey in the AP-REP message from the server. + + Note that to preserve the quality of randomness provided by the KDC, + implementations of this extension SHOULD consider using the service + ticket session key value as a source of additional entropy when + generating the negotiated subkey. If the 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. + +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. + +5. IANA Considerations + + No IANA actions are required for this document. + +6. Normative References + + [CLAR] RFC-Editor: To be replaced by RFC number for draft-ietf- + krb-wg-kerberos-clarifications. Work in Progress. + + [GSS-CFX] RFC-Editor: To be replaced by RFC number for draft-ietf- + krb-wg-gssapi-cfx. Work in Progress. + + [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. + + + + +Zhu, et al. Expires October 2, 2005 [Page 4] + +Internet-Draft Enctype Negotiation March 2005 + + + [SPNEGOBIS] + RFC-Editor: To be replaced by RFC number for draft-ietf- + kitten-2478bis. Work in progress. + + [X690] ASN.1 encoding rules: Specification of Basic Encoding Rules + (BER), Canonical Encoding Rules (CER) and Distinguished + Encoding Rules (DER), ITU-T Recommendation X.690 (1997) | + ISO/IEC International Standard 8825-1:1998. + + +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 + + + Karthik Jaganathan + Microsoft Corporation + One Microsoft Way + Redmond, WA 98052 + US + + Email: karthikj@microsoft.com + +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: + + + + + +Zhu, et al. Expires October 2, 2005 [Page 5] + +Internet-Draft Enctype Negotiation March 2005 + + + 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 October 2, 2005 [Page 6] + +Internet-Draft Enctype Negotiation March 2005 + + +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. 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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 (2005). 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 October 2, 2005 [Page 7] + +