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(The document does seem to have the reference to RFC 2119 which the ID-Checklist requires). -- The document date (22 October 2021) is 907 days in the past. Is this intentional? Checking references for intended status: Proposed Standard ---------------------------------------------------------------------------- (See RFCs 3967 and 4897 for information about using normative references to lower-maturity documents in RFCs) -- Looks like a reference, but probably isn't: '1' on line 218 == Unused Reference: 'BCP14' is defined on line 258, but no explicit reference was found in the text Summary: 0 errors (**), 0 flaws (~~), 3 warnings (==), 2 comments (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 LAMPS Working Group M. Richardson 3 Internet-Draft Sandelman Software Works 4 Intended status: Standards Track D. Harkins 5 Expires: 25 April 2022 The Industrial Lounge 6 D. von Oheimb 7 Siemens 8 O. Friel 9 Cisco 10 22 October 2021 12 Clarification of RFC7030 CSR Attributes definition 13 draft-richardson-lamps-rfc7030-csrattrs-00 15 Abstract 17 Enrollment over Secure Transport (EST) is ambiguous in specification 18 of the CSR Attributes Response. This has resulted in implementation 19 challenges and implementor confusion. This document updates EST and 20 clarifies how the CSR Attributes Response can be used by an EST 21 server to specify both CSR attribute OIDs and also CSR attribute 22 values that the server expects the client to include in its CSR 23 request. 25 Status of This Memo 27 This Internet-Draft is submitted in full conformance with the 28 provisions of BCP 78 and BCP 79. 30 Internet-Drafts are working documents of the Internet Engineering 31 Task Force (IETF). Note that other groups may also distribute 32 working documents as Internet-Drafts. The list of current Internet- 33 Drafts is at https://datatracker.ietf.org/drafts/current/. 35 Internet-Drafts are draft documents valid for a maximum of six months 36 and may be updated, replaced, or obsoleted by other documents at any 37 time. It is inappropriate to use Internet-Drafts as reference 38 material or to cite them other than as "work in progress." 40 This Internet-Draft will expire on 25 April 2022. 42 Copyright Notice 44 Copyright (c) 2021 IETF Trust and the persons identified as the 45 document authors. All rights reserved. 47 This document is subject to BCP 78 and the IETF Trust's Legal 48 Provisions Relating to IETF Documents (https://trustee.ietf.org/ 49 license-info) in effect on the date of publication of this document. 50 Please review these documents carefully, as they describe your rights 51 and restrictions with respect to this document. Code Components 52 extracted from this document must include Simplified BSD License text 53 as described in Section 4.e of the Trust Legal Provisions and are 54 provided without warranty as described in the Simplified BSD License. 56 Table of Contents 58 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 59 2. CSR Attributes Handling . . . . . . . . . . . . . . . . . . . 3 60 2.1. Current EST Specification . . . . . . . . . . . . . . . . 3 61 2.2. Updated CSR Attributes Handling . . . . . . . . . . . . . 4 62 2.2.1. Subject Handling . . . . . . . . . . . . . . . . . . 4 63 2.3. Extend CSR structure to allow values: . . . . . . . . . . 5 64 3. Security Considerations . . . . . . . . . . . . . . . . . . . 5 65 3.1. Identity and Privacy Considerations . . . . . . . . . . . 6 66 4. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 67 5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 68 6. Changelog . . . . . . . . . . . . . . . . . . . . . . . . . . 6 69 7. References . . . . . . . . . . . . . . . . . . . . . . . . . 6 70 7.1. Normative References . . . . . . . . . . . . . . . . . . 6 71 7.2. Informative References . . . . . . . . . . . . . . . . . 6 72 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 74 1. Introduction 76 Enrollment over Secure Transport [RFC7030] (EST) has been used in a 77 wide variety of applications. In particular, [RFC8994] and [RFC8995] 78 describe a way to use it in order to build out an autonomic control 79 plane (ACP) [RFC8368]. 81 The ACP requires that each node be given a very specific 82 SubjectAltName. So, the solution was for the EST server to use 83 section 2.6 of [RFC7030] to convey to the EST client the actual 84 SubjectAltName that will end up in its certificate. 86 As a result of some implementation challenges, it came to light that 87 this particular way of using the CSR attributes was not universally 88 agreed upon, and in fact runs contrary to section 2.6, which says 89 that the CSR attributes "provide additional descriptive information 90 that the EST server cannot access itself" (when, in this case, it is 91 the EST server and not the EST client that has access to this 92 information). 94 In particular, it is not universally agreed that a CSR Attributes 95 response can be used by an EST server to specify both attribute OIDs 96 and attribute values. This document, therefore, updates section 2.6 97 to define this behavior. 99 This document also updates section 4.5 to include revised ASN.1 that 100 covers all uses and is backward compatible with the existing use. 102 Additional examples are provided in an appendix. 104 2. CSR Attributes Handling 106 2.1. Current EST Specification 108 The ASN.1 for CSR Attributes as defined in EST section 4.5.2 is: 110 CsrAttrs ::= SEQUENCE SIZE (0..MAX) OF AttrOrOID 112 AttrOrOID ::= CHOICE (oid OBJECT IDENTIFIER, attribute Attribute } 114 Attribute { ATTRIBUTE:IOSet } ::= SEQUENCE { 115 type ATTRIBUTE.&id({IOSet}), 116 values SET SIZE(1..MAX) OF ATTRIBUTE.&Type({IOSet}{@type}) } 118 That section also states the following: 120 the values indicating the particular 121 attributes desired to be included in the resulting certificate's 122 extensions 124 This has been interpreted by some implementations as meaning that the 125 CSR Attributes response can only include values for the attribute 126 OIDs that the client should include in its CSR, and cannot include 127 the actual values of those attributes. This is further reinforced by 128 the example: 130 Attribute: type = extensionRequest (1.2.840.113549.1.9.14) 131 value = macAddress (1.3.6.1.1.1.1.22) 133 This example illustrates that the 'value' specified is an attribute 134 OID, for example the macAddress OID, and not the value of the 135 attribute itself. 137 There is no clearly documented mechanism with supporting examples 138 that specifies how a CSR Attributes response can include a value for 139 a given attribute such as SubjectAltName. 141 EST section 4.5.2 also states the following: 143 The structure of the CSR Attributes Response SHOULD, to the 144 greatest extent possible, reflect the structure of the CSR 145 it is requesting. 147 This statement aligns closely with the goal of this document. 148 Additionally, EST Extensions [RFC8295] Appendix A has an informative 149 appendix that outlines how a full CSR can be included in the CSR 150 Attributes response. 152 2.2. Updated CSR Attributes Handling 154 This is option one. 156 This document defines how a CSR Attributes response is aligned with 157 the PKCS#10 'CertificationRequestInfo' structure. The CSR Attributes 158 response includes a PKCS#10 CSR structure that optionally includes 159 any required values for included attributes. The following 160 formatting rules apply to the CSR Attributes PKCSC#10 161 'CertificationRequestInfo' structure included in a CSR Attributes 162 response: 164 * Concrete attribute values may be ommitted. If an attribute OID is 165 included but the attribute value is not included, this indicates 166 to the client that it should include and specify that attribute 167 value. 169 * Additional attribute OIDs may be included. For example, for 170 requesting the use of challengePassword, or for specifying public- 171 key algorithms. 173 TODO Rule for multiple attributes. RFC 2986 and 5967 do not describe 174 how handle conflicting attributes. There was a suggestion to not 175 allow more than one instance of an attribute. However, you can have 176 multiple SubjectAltNames... 178 2.2.1. Subject Handling 180 There is no defined OID for the 'subject' field. An EST server can 181 specify 'subject' field values in a CSR Attributes response by 182 including all required relative distinguished names as a sequence of 183 OIDs, for example: 185 SEQUENCE { 186 OBJECT IDENTIFIER commonName (2 5 4 3) 187 UTF8String "example.com" 188 } 190 SEQUENCE { 191 OBJECT IDENTIFIER serialNumber (2 5 4 5) 192 PrintableString "EXAMPLE123' 193 } 195 2.3. Extend CSR structure to allow values: 197 This is option two. 199 This would just add a value to the SEQUENCE: 201      OBJECT challengePassword 202      SEQUENCE 203        OBJECT subjectAltName 204        SET 205          OBJECT someACPgoo 206      SEQUENCE 207        OBJECT id-ecPublicKey 208        SET 209          OBJECT secp384r1 210      OBJECT ecdsa-with-SHA384 212 For example: 214 0 30: SEQUENCE { 215 2 28: SEQUENCE { 216 4 3: OBJECT IDENTIFIER subjectAltName (2 5 29 17) 217 9 21: SET { 218 11 19: [1] { 219 13 17: UTF8String 'hello@example.com' 220 : } 221 : } 222 : } 223 : } 225 3. Security Considerations 227 All security considertions from EST [RFC7030] section 6 are 228 applicable. 230 3.1. Identity and Privacy Considerations 232 An EST server may use this mechanism to instruct the EST client about 233 the identities it should include in the CSR it sends as part of 234 enrollment. The client may only be aware of its IDevID Subject, 235 which includes a manufacturer serial number. The EST server can use 236 this mechanism to tell the client to include a specific fully 237 qualified domain name in the CSR in order to complete domain 238 ownership proofs required by the CA. Additionally, the EST server 239 may deem the manufacturer serial number in an IDevID as personally 240 identifiable information, and may want to specify a new random opaque 241 identifier that the pledge should use in its CSR. This may be 242 desirable if the CA and EST server have different operators. 244 4. IANA Considerations 246 None. 248 5. Acknowledgements 250 TODO 252 6. Changelog 254 7. References 256 7.1. Normative References 258 [BCP14] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 259 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 260 May 2017, . 262 [RFC7030] Pritikin, M., Ed., Yee, P., Ed., and D. Harkins, Ed., 263 "Enrollment over Secure Transport", RFC 7030, 264 DOI 10.17487/RFC7030, October 2013, 265 . 267 [RFC8994] Eckert, T., Ed., Behringer, M., Ed., and S. Bjarnason, "An 268 Autonomic Control Plane (ACP)", RFC 8994, 269 DOI 10.17487/RFC8994, May 2021, 270 . 272 [RFC8995] Pritikin, M., Richardson, M., Eckert, T., Behringer, M., 273 and K. Watsen, "Bootstrapping Remote Secure Key 274 Infrastructure (BRSKI)", RFC 8995, DOI 10.17487/RFC8995, 275 May 2021, . 277 7.2. Informative References 279 [RFC8295] Turner, S., "EST (Enrollment over Secure Transport) 280 Extensions", RFC 8295, DOI 10.17487/RFC8295, January 2018, 281 . 283 [RFC8368] Eckert, T., Ed. and M. Behringer, "Using an Autonomic 284 Control Plane for Stable Connectivity of Network 285 Operations, Administration, and Maintenance (OAM)", 286 RFC 8368, DOI 10.17487/RFC8368, May 2018, 287 . 289 Authors' Addresses 291 Michael Richardson 292 Sandelman Software Works 294 Email: mcr+ietf@sandelman.ca 296 Dan Harkins 297 The Industrial Lounge 299 Email: dharkins@lounge.org 301 Dr. David von Oheimb 302 Siemens 304 Email: dev@ddvo.net 306 Owen Friel 307 Cisco 309 Email: ofriel@cisco.com