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Independent Submission                                      A. KeromytisRequest for Comments: 6042                           Columbia UniversityCategory: Informational                                     October 2010ISSN: 2070-1721Transport Layer Security (TLS) Authorization Using KeyNoteAbstract   This document specifies the use of the KeyNote trust-management   system as an authorization extension in the Transport Layer Security   (TLS) Handshake Protocol, according to guidelines inRFC 5878.   Extensions carried in the client and server hello messages confirm   that both parties support the desired authorization data types.   Then, if supported by both the client and the server, KeyNote   credentials are exchanged in the supplemental data handshake message.Status of This Memo   This document is not an Internet Standards Track specification; it is   published for informational purposes.   This is a contribution to the RFC Series, independently of any other   RFC stream.  The RFC Editor has chosen to publish this document at   its discretion and makes no statement about its value for   implementation or deployment.  Documents approved for publication by   the RFC Editor are not a candidate for any level of Internet   Standard; seeSection 2 of RFC 5741.   Information about the current status of this document, any errata,   and how to provide feedback on it may be obtained athttp://www.rfc-editor.org/info/rfc6042.Copyright Notice   Copyright (c) 2010 IETF Trust and the persons identified as the   document authors.  All rights reserved.   This document is subject toBCP 78 and the IETF Trust's Legal   Provisions Relating to IETF Documents   (http://trustee.ietf.org/license-info) in effect on the date of   publication of this document.  Please review these documents   carefully, as they describe your rights and restrictions with respect   to this document.Keromytis                     Informational                     [Page 1]

RFC 6042             TLS Authorization Using KeyNote        October 20101.  Introduction   This document describes the identifiers necessary to exchange KeyNote   [KEYNOTE] credential assertions inside a TLS [TLS1.0] [TLS1.1]   [TLS1.2] exchange.  Such credential assertions can authorize the   client and/or the server to perform certain actions.  In most usage   scenarios, the KeyNote credential assertions will be signed by a   cryptographic public key [RFC2792].  By using the X.509 key and   signature encoding [X509KEY], it is possible to add KeyNote-based   authorization and policy compliance support to the existing,   unmodified X.509 authentication exchange in TLS.   A list of KeyNote credentials (e.g., forming a delegation chain) may   be sent as part of the same payload.  Alternatively, a URL [RFC3986]   pointing to the location of such a list of KeyNote credentials may be   provided.   In most scenarios, at least one of these credentials will be issued   to the public key of the transmitter of the credentials, i.e., said   public key will appear in the "Licensees" field of at least one   KeyNote credential assertion.  The same public key will generally be   used by the transmitter of the same credentials to authenticate as   part of the TLS exchange.  The authentication material (e.g.,   cryptographic public key) that was used by the transmitter to   authenticate in the TLS exchange will be provided to the KeyNote   evaluation engine as an "Action Authorizer".1.1.  Conventions   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].2.  KeyNote Credential Assertion Lists   The KeyNote Assertion List type definition in the TLS Authorization   Data Formats registry is:      keynote_assertion_list(64)   When the keynote_assertion_list value is present, the authorization   data is a list of KeyNote credential assertions that conforms to the   profile inRFC 2704 [KEYNOTE].Keromytis                     Informational                     [Page 2]

RFC 6042             TLS Authorization Using KeyNote        October 2010   A KeyNote assertion list is transmitted inside an   AuthorizationDataEntry structure as an opaque sequence of   1 - 2^16-1 bytes:      opaque KeyNoteAssertionList<1..2^16-1>;   When KeyNoteAssertionList is used, the field contains an ASCII-   encoded list of signed KeyNote assertions, as described inRFC 2704   [KEYNOTE].  The assertions are separated by two "\n" (newline)   characters.  A KeyNote assertion is a structure similar to a public   key certificate; the main difference is that instead of a binding   between a name and a public key, KeyNote assertions bind public keys   to authorization rules that are evaluated by the peer when the sender   later issues specific requests.   When making an authorization decision based on a list of KeyNote   assertions, proper linkage between the KeyNote assertions and the   public key certificate that is transferred in the TLS Certificate   message is needed.  Receivers of a KeyNote assertion list should   initialize the ACTION_AUTHORIZER variable to be the sender's public   key, which was used to authenticate the TLS exchange.  If a different   authentication mechanism is used, it is the responsibility of the   credential issuer to issue the appropriate credentials.3.  KeyNote Credential Assertion List URL   The KeyNote Assertion List URL type definition in the TLS   Authorization Data Formats registry is:      keynote_assertion_list_url(65)   A KeyNote Assertion List URL is transmitted inside an   AuthorizationDataEntry structure as a URLandHash structure [AUTHZ].   When the keynote_assertion_list_url value is present, the   authorization data is a list of KeyNote assertions as described inSection 2; however, the KeyNote assertion list is fetched with the   supplied URL.  A one-way hash value is provided to ensure that the   intended KeyNote credential assertion is obtained.   Implementations that support keynote_assertion_list_url MUST support   URLs that employ the HTTP scheme [HTTP].  These implementations MUST   confirm that the hash value computed on the fetched authorization   matches the one received in the handshake.  Mismatch of the hash   values SHOULD be treated as though the authorization was not   provided, which will result in a bad_certificate alert [AUTHZ].Keromytis                     Informational                     [Page 3]

RFC 6042             TLS Authorization Using KeyNote        October 2010   Other schemes may also be supported.  When dereferencing these URLs,   circular dependencies MUST be avoided.  Avoiding TLS when   dereferencing these URLs is one way to avoid circular dependencies.   Therefore, clients using the HTTP scheme MUST NOT use these TLS   extensions if the Upgrade mechanism in HTTP [UPGRADE] is used.  For   other schemes, similar care must be taken to avoid using these TLS   extensions.4.  IANA Considerations   With this document, IANA has registered two new entries in the TLS   Authorization Data Formats registry: keynote_assertion_list(64) and   keynote_assertion_list_url(65).  This registry is defined in [AUTHZ].5.  Security Considerations   There are no security considerations beyond those discussed in   [KEYNOTE], [RFC2792], and [AUTHZ].6.  References6.1.  Normative References   [RFC2119]   Bradner, S., "Key words for use in RFCs to Indicate               Requirement Levels",BCP 14,RFC 2119, March 1997.   [TLS1.0]    Dierks, T. and C. Allen, "The TLS Protocol Version 1.0",RFC 2246, January 1999.   [TLS1.1]    Dierks, T. and E. Rescorla, "The Transport Layer Security               (TLS) Protocol Version 1.1",RFC 4346, April 2006.   [TLS1.2]    Dierks, T. and E. Rescorla, "The Transport Layer Security               (TLS) Protocol Version 1.2",RFC 5246, August 2008.   [HTTP]      Fielding, R., Gettys, J., Mogul, J., Frystyk, H.,               Masinter, L., Leach, P., and T. Berners-Lee, "Hypertext               Transfer Protocol -- HTTP/1.1",RFC 2616, June 1999.   [UPGRADE]   Khare, R. and S. Lawrence, "Upgrading to TLS Within               HTTP/1.1",RFC 2817, May 2000.   [KEYNOTE]   Blaze, M., Feigenbaum, J., Ioannidis, J., and A.               Keromytis, "The KeyNote Trust-Management System               Version 2",RFC 2704, September 1999.   [AUTHZ]     Brown, M. and R. Housley, "Transport Layer Security (TLS)               Authorization Extensions",RFC 5878, May 2010.Keromytis                     Informational                     [Page 4]

RFC 6042             TLS Authorization Using KeyNote        October 20106.2.  Informative References   [RFC2792]   Blaze, M., Ioannidis, J., and A. Keromytis, "DSA and RSA               Key and Signature Encoding for the KeyNote Trust               Management System",RFC 2792, March 2000.   [X509KEY]   Keromytis, A., "X.509 Key and Signature Encoding for the               KeyNote Trust Management System",RFC 5708, January 2010.   [RFC3986]   Berners-Lee, T., Fielding, R., and L. Masinter, "Uniform               Resource Identifier (URI): Generic Syntax", STD 66,RFC 3986, January 2005.Keromytis                     Informational                     [Page 5]

RFC 6042             TLS Authorization Using KeyNote        October 2010Appendix A.  Updated TLS Authorization Data Structures   For clarity, this Appendix shows an updated version of the relevant   data structures from Section 3.3 in [AUTHZ] with the new entries   described in this document.  The added elements are denoted with two   asterisks ("**") at the end of the respective lines.      struct {         AuthorizationDataEntry authz_data_list<1..2^16-1>;      } AuthorizationData;      struct {         AuthzDataFormat authz_format;         select (AuthzDataFormat) {            case x509_attr_cert:              X509AttrCert;            case saml_assertion:              SAMLAssertion;            case x509_attr_cert_url:          URLandHash;            case saml_assertion_url:          URLandHash;            case keynote_assertion_list:      KeyNoteAssertionList;   **            case keynote_assertion_list_url:  URLandHash;             **         }      } AuthorizationDataEntry;      enum {         x509_attr_cert(0), saml_assertion(1), x509_attr_cert_url(2),         saml_assertion_url(3),         keynote_assertion_list(64), keynote_assertion_list_url(65),  **         (255)      } AuthzDataFormat;      opaque X509AttrCert<1..2^16-1>;      opaque SAMLAssertion<1..2^16-1>;      opaque KeyNoteAssertionList<1..2^16-1>;                         **      struct {         opaque url<1..2^16-1>;         HashAlgorithm hash_alg;         select (hash_alg) {            case md5:    MD5Hash;            case sha1:   SHA1Hash;            case sha224: SHA224Hash;            case sha256: SHA256Hash;            case sha384: SHA384Hash;            case sha512: SHA512Hash;         } hash;      } URLandHash;Keromytis                     Informational                     [Page 6]

RFC 6042             TLS Authorization Using KeyNote        October 2010      enum {         none(0), md5(1), sha1(2), sha224(3), sha256(4), sha384(5),         sha512(6), (255)      } HashAlgorithm;      opaque MD5Hash[16];      opaque SHA1Hash[20];      opaque SHA224Hash[28];      opaque SHA256Hash[32];      opaque SHA384Hash[48];      opaque SHA512Hash[64];Author's Address   Angelos D. Keromytis   Department of Computer Science   Columbia University   Mail Code 0401   1214 Amsterdam Avenue   New York, NY  10027   USA   EMail: angelos@cs.columbia.eduKeromytis                     Informational                     [Page 7]