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Is this intentional? Checking references for intended status: Informational ---------------------------------------------------------------------------- No issues found here. Summary: 1 error (**), 0 flaws (~~), 1 warning (==), 1 comment (--). Run idnits with the --verbose option for more detailed information about the items above. -------------------------------------------------------------------------------- 2 Individual T. Ito 3 Internet-Draft SECOM CO., LTD. 4 Intended status: Informational T. Okubo 5 Expires: October 3, 2021 DigiCert, Inc. 6 April 01, 2021 8 General Purpose Extended Key Usage (EKU) for Document Signing X.509 9 Certificates 10 draft-ito-documentsigning-eku-00 12 Abstract 14 [RFC5280] specifies several extended key usages for X.509 15 certificates. This document defines a general purpose document 16 signing extended key usage for X.509 public key certificates which 17 restricts the usage of the certificates for document signing. 19 Status of This Memo 21 This Internet-Draft is submitted in full conformance with the 22 provisions of BCP 78 and BCP 79. 24 Internet-Drafts are working documents of the Internet Engineering 25 Task Force (IETF). Note that other groups may also distribute 26 working documents as Internet-Drafts. The list of current Internet- 27 Drafts is at https://datatracker.ietf.org/drafts/current/. 29 Internet-Drafts are draft documents valid for a maximum of six months 30 and may be updated, replaced, or obsoleted by other documents at any 31 time. It is inappropriate to use Internet-Drafts as reference 32 material or to cite them other than as "work in progress." 34 This Internet-Draft will expire on October 3, 2021. 36 Copyright Notice 38 Copyright (c) 2021 IETF Trust and the persons identified as the 39 document authors. All rights reserved. 41 This document is subject to BCP 78 and the IETF Trust's Legal 42 Provisions Relating to IETF Documents 43 (https://trustee.ietf.org/license-info) in effect on the date of 44 publication of this document. Please review these documents 45 carefully, as they describe your rights and restrictions with respect 46 to this document. Code Components extracted from this document must 47 include Simplified BSD License text as described in Section 4.e of 48 the Trust Legal Provisions and are provided without warranty as 49 described in the Simplified BSD License. 51 Table of Contents 53 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 54 2. Conventions and Definitions . . . . . . . . . . . . . . . . . 3 55 3. Extended Key usage for DocumentSigning . . . . . . . . . . . 3 56 3.1. Extended Key Usage Values for Document Signing . . . . . 3 57 4. Implications for a Certification Authority . . . . . . . . . 4 58 5. Security Considerations . . . . . . . . . . . . . . . . . . . 4 59 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 4 60 7. Normative References . . . . . . . . . . . . . . . . . . . . 4 61 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 5 63 1. Introduction 65 [RFC5280] specifies several extended key usages for X.509 66 certificates. In addition, several extended key usage had been 67 added[RFC7299] as public OID under the IANA repository. While usage 68 of any extended key usage is bad practice for publicly trusted 69 certificates, there are no public and general extended key usage 70 explicitly assigned for Document Signing certificates. The current 71 practice is to use id-kp-emailProtection, id-kp-codeSigning or vendor 72 defined Object ID for general document signing purposes. 74 In circumstances where code signing and S/MIME certificates are also 75 widely used for document signing, the technical or policy changes 76 that are made to code signing and S/MIME certificates may cause 77 unexpected behaviors or have an adverse impact such as decreased 78 cryptographic agility on the document signing ecosystem and vice 79 versa. 81 There is no issue if the vendor defined OIDs are used in a PKI (or a 82 trust program) governed by the vendor. However, if the OID is used 83 outside of the vendor governance, the usage can easily become out of 84 control (e.g. - When the end user encounters vendor defined OIDs, 85 they might want to ask that vendor about use of the certificate, 86 however, the vendor may not know about the particular use. - If the 87 issuance of the cert is not under the control of the OID owner, there 88 is no way for the OID owner to know what the impact will be if any 89 change is made to the OID in question, and it would restrict vendor's 90 choice of OID management. etc.). 92 Therefore, it is not favorable to use a vendor defined EKU for 93 signing a document that is not governed by the vendor. 95 This document defines a general Document Signing extended key usage. 97 2. Conventions and Definitions 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and 101 "OPTIONAL" in this document are to be interpreted as described in BCP 102 14 [RFC2119] [RFC8174] when, and only when, they appear in all 103 capitals, as shown here. 105 3. Extended Key usage for DocumentSigning 107 This specification defines the KeyPurposeId id-kp-documentSigning. 108 Inclusion of this KeyPurposeId in a certificate indicates that the 109 use of any Subject names in the certificate is restricted to use by a 110 document signing. 112 Term of "Document Sign" in this paper is digitaly signing human 113 readable data or data that is intended to be human readable by means 114 of services and software. 116 3.1. Extended Key Usage Values for Document Signing 118 [RFC5280] specifies the EKU X.509 certificate extension for use in 119 the Internet. The extension indicates one or more purposes for which 120 the certified public key is valid. The EKU extension can be used in 121 conjunction with the key usage extension, which indicates how the 122 public key in the certificate is used, in a more basic cryptographic 123 way. 125 The EKU extension syntax is repeated here for convenience: 127 ExtKeyUsageSyntax ::= SEQUENCE SIZE (1..MAX) OF KeyPurposeId 128 KeyPurposeId ::= OBJECT IDENTIFIER 130 This specification defines the KeyPurposeId id-kp-documentSigning. 131 Inclusion of this KeyPurposeId in a certificate indicates that the 132 use of any Subject names in the certificate is restricted to use by a 133 document signing service or a software (along with any usages allowed 134 by other EKU values). 136 id-kp OBJECT IDENTIFIER ::= 137 { iso(1) identified-organization(3) dod(6) internet(1) 138 security(5) mechanisms(5) pkix(7) 3 } 139 id-kp-documentSigning OBJECT IDENTIFIER ::= { id-kp XX } 141 4. Implications for a Certification Authority 143 The procedures and practices employed by a certification authority 144 MUST ensure that the correct values for the EKU extension are 145 inserted in each certificate that is issued. Unless certificates are 146 governed by a vendor specific PKI (or trust program), certificates 147 that indicate usage for document signing MAY include the id-kp- 148 documentSigning EKU extension. This does not encompass the mandatory 149 usage of the id-kp-documentSigning EKU in conjunction with the vendor 150 specific EKU. However, this does not restrict the CA from including 151 multiple EKUs related to document signing. 153 5. Security Considerations 155 The Use of id-kp-documentSigning EKU can prevents the usage of id-kp- 156 emailProtection for none-email purposes and id-kp-codeSigning for 157 signing objects other than binary codes. An id-kp-documentSigning 158 EKU value does not introduce any new security or privacy concerns. 160 6. IANA Considerations 162 The id-kp-documentSigning purpose requires an object identifier 163 (OID). The objects are defined in an arc delegated by IANA to 164 Limited Additional Mechanisms for PKIX and SMIME (lamps). No further 165 action is necessary by IANA. 167 7. Normative References 169 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 170 Requirement Levels", BCP 14, RFC 2119, 171 DOI 10.17487/RFC2119, March 1997, 172 . 174 [RFC5280] Cooper, D., Santesson, S., Farrell, S., Boeyen, S., 175 Housley, R., and W. Polk, "Internet X.509 Public Key 176 Infrastructure Certificate and Certificate Revocation List 177 (CRL) Profile", RFC 5280, DOI 10.17487/RFC5280, May 2008, 178 . 180 [RFC7299] Housley, R., "Object Identifier Registry for the PKIX 181 Working Group", RFC 7299, DOI 10.17487/RFC7299, July 2014, 182 . 184 [RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC 185 2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174, 186 May 2017, . 188 Authors' Addresses 190 Tadahiko Ito 191 SECOM CO., LTD. 193 Email: tadahiko.ito.public@gmail.com 195 Tomofumi Okubo 196 DigiCert, Inc. 198 Email: tomofumi.okubo+ietf@gmail.com