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Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) No issues found here. Summary: 0 errors (**), 0 flaws (~~), 1 warning (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Internet Engineering Task Force A. Jain 3 Internet-Draft Georgia Tech 4 Updates: 4120 (if approved) N. Kinder 5 Intended status: Standards Track N. McCallum 6 Expires: July 8, 2017 Red Hat, Inc. 7 January 4, 2017 9 Authentication Indicator in Kerberos Tickets 10 draft-ietf-kitten-krb-auth-indicator-06 12 Abstract 14 This document updates RFC 4120 in order to specify an extension in 15 the Kerberos protocol. It defines a new authorization data type AD- 16 AUTHENTICATION-INDICATOR. The purpose of introducing this data type 17 is to include an indicator of the strength of a client's 18 authentication in service tickets so that application services can 19 use it as an input into policy decisions. 21 Status of This Memo 23 This Internet-Draft is submitted in full conformance with the 24 provisions of BCP 78 and BCP 79. 26 Internet-Drafts are working documents of the Internet Engineering 27 Task Force (IETF). Note that other groups may also distribute 28 working documents as Internet-Drafts. The list of current Internet- 29 Drafts is at http://datatracker.ietf.org/drafts/current/. 31 Internet-Drafts are draft documents valid for a maximum of six months 32 and may be updated, replaced, or obsoleted by other documents at any 33 time. It is inappropriate to use Internet-Drafts as reference 34 material or to cite them other than as "work in progress." 36 This Internet-Draft will expire on July 8, 2017. 38 Copyright Notice 40 Copyright (c) 2017 IETF Trust and the persons identified as the 41 document authors. All rights reserved. 43 This document is subject to BCP 78 and the IETF Trust's Legal 44 Provisions Relating to IETF Documents 45 (http://trustee.ietf.org/license-info) in effect on the date of 46 publication of this document. Please review these documents 47 carefully, as they describe your rights and restrictions with respect 48 to this document. Code Components extracted from this document must 49 include Simplified BSD License text as described in Section 4.e of 50 the Trust Legal Provisions and are provided without warranty as 51 described in the Simplified BSD License. 53 Table of Contents 55 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 56 2. Document Conventions . . . . . . . . . . . . . . . . . . . . 2 57 3. AD Type Specification . . . . . . . . . . . . . . . . . . . . 2 58 4. Assigned Numbers . . . . . . . . . . . . . . . . . . . . . . 3 59 5. Security Considerations . . . . . . . . . . . . . . . . . . . 3 60 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 61 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 4 62 7.1. Normative References . . . . . . . . . . . . . . . . . . 4 63 7.2. Informative References . . . . . . . . . . . . . . . . . 5 64 Appendix A. ASN.1 Module . . . . . . . . . . . . . . . . . . . . 6 65 Appendix B. Acknowledgements . . . . . . . . . . . . . . . . . . 6 66 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 Kerberos [RFC4120] allows secure interaction among users and services 71 over a network. It supports a variety of authentication mechanisms 72 using its pre-authentication framework [RFC6113]. The Kerberos 73 authentication service has been architected to support password-based 74 authentication as well as multi-factor authentication using one-time 75 password devices, public-key cryptography and other pre- 76 authentication schemes. Implementations that offer pre- 77 authentication mechanisms supporting significantly different 78 strengths of client authentication may choose to keep track of the 79 strength of the authentication that was used, for use as an input 80 into policy decisions. 82 This document specifies a new authorization data type to convey 83 authentication strength information to application services. 84 Elements of this type appear within an AD-CAMMAC [RFC7751] container. 86 2. Document Conventions 88 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 89 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 90 document are to be interpreted as described in RFC 2119 [RFC2119]. 92 3. AD Type Specification 94 The KDC MAY include authorization data of ad-type 97, wrapped in AD- 95 CAMMAC, in initial credentials. The KDC MAY copy it from a ticket- 96 granting ticket into service tickets. 98 The corresponding ad-data field contains the DER encoding of the 99 following ASN.1 type: 101 AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String 103 Each UTF8String value is a short string that indicates that a 104 particular set of requirements was met during the initial 105 authentication. These strings are intended to be compared against 106 known values. They are not intended to store structured data. Each 107 string MUST be either: 109 * A URI which references a Level of Assurance Profile [RFC6711] 111 * A site-defined string, which MUST NOT contain a colon, whose 112 meaning is determined by the realm administrator. 114 Authorization data elements of type AD-AUTHENTICATION-INDICATOR MUST 115 be included in an AD-CAMMAC container so that their contents can be 116 verified as originating from the KDC. Elements of type AD- 117 AUTHENTICATION-INDICATOR MAY safely be ignored by applications and 118 KDCs that do not implement this element. 120 4. Assigned Numbers 122 RFC 4120 [RFC4120] is updated in the following way: 124 o The ad-type number 97 is assigned for AD-AUTHENTICATION-INDICATOR, 125 updating the table in Section 7.5.4 of RFC 4120 [RFC4120]. 127 o The table in Section 5.2.6 of RFC 4120 [RFC4120] is updated to map 128 the ad-type 97 to "DER encoding of AD-AUTHENTICATION-INDICATOR". 130 5. Security Considerations 132 Elements of type AD-AUTHENTICATION-INDICATOR are wrapped in AD-CAMMAC 133 containers. AD-CAMMAC supersedes AD-KDC-ISSUED, and allows both 134 application services and the KDC to verify the authenticity of the 135 contained authorization data. 137 KDC implementations MUST use AD-CAMMAC verifiers as described in the 138 the security considerations of RFC 7751 [RFC7751] to ensure that AD- 139 AUTHENTICATION-INDICATOR elements are not modified by an attacker. 140 Application servers MUST validate the AD-CAMMAC container before 141 making authorization decisions based on AD-AUTHENTICATION-INDICATOR 142 elements. Application servers MUST NOT make authorization decisions 143 based on AD-AUTHENTICATION-INDICATOR elements which appear outside of 144 AD-CAMMAC containers. 146 Using multiple strings in AD-AUTHENTICATION-INDICATOR may lead to 147 ambiguity when a service tries to make a decision based on the AD- 148 AUTHENTICATION-INDICATOR values. This ambiguity can be avoided if 149 indicator values are always used as a positive indication of certain 150 requirements being met during the initial authentication. For 151 example, if a "without-password" indicator is inserted whenever 152 authentication occurs without a password, a service might assume this 153 is an indication that a higher-strength client authentication 154 occurred. However, this indicator might also be inserted when no 155 authentication occurred at all (such as anonymous PKINIT). 157 Service evaluation of site-defined indicators MUST consider the realm 158 of original authentication in order to avoid cross-realm indicator 159 collisions. Failure to enforce this property can result in invalid 160 authorization. 162 6. IANA Considerations 164 This document has no actions for IANA. 166 7. References 168 7.1. Normative References 170 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 171 Requirement Levels", BCP 14, RFC 2119, 172 DOI 10.17487/RFC2119, March 1997, 173 . 175 [RFC4120] Neuman, C., Yu, T., Hartman, S., and K. Raeburn, "The 176 Kerberos Network Authentication Service (V5)", RFC 4120, 177 DOI 10.17487/RFC4120, July 2005, 178 . 180 [RFC6113] Hartman, S. and L. Zhu, "A Generalized Framework for 181 Kerberos Pre-Authentication", RFC 6113, 182 DOI 10.17487/RFC6113, April 2011, 183 . 185 [RFC7751] Sorce, S. and T. Yu, "Kerberos Authorization Data 186 Container Authenticated by Multiple Message Authentication 187 Codes (MACs)", RFC 7751, DOI 10.17487/RFC7751, March 2016, 188 . 190 7.2. Informative References 192 [RFC6711] Johansson, L., "An IANA Registry for Level of Assurance 193 (LoA) Profiles", RFC 6711, DOI 10.17487/RFC6711, August 194 2012, . 196 Appendix A. ASN.1 Module 198 KerberosV5AuthenticationIndicators { 199 iso(1) identified-organization(3) dod(6) internet(1) 200 security(5) kerberosV5(2) modules(4) 201 authentication-indicators(9) 202 } DEFINITIONS EXPLICIT TAGS ::= BEGIN 204 AD-AUTHENTICATION-INDICATOR ::= SEQUENCE OF UTF8String 206 END 208 Appendix B. Acknowledgements 210 Dmitri Pal (Red Hat) 211 Simo Sorce (Red Hat) 212 Greg Hudson (MIT) 214 Authors' Addresses 216 Anupam Jain 217 Georgia Tech 218 225 North Ave NW 219 Atlanta, GA 30332 220 USA 222 EMail: ajain323@gatech.edu 224 Nathan Kinder 225 Red Hat, Inc. 226 444 Castro St. 227 Suite 500 228 Mountain View, CA 94041 229 USA 231 EMail: nkinder@redhat.com 233 Nathaniel McCallum 234 Red Hat, Inc. 235 100 East Davie Street 236 Raleigh, NC 27601 237 USA 239 EMail: npmccallum@redhat.com