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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 Network Working Group A. Melnikov 3 Internet-Draft Isode Ltd 4 Intended status: Informational July 12, 2021 5 Expires: January 13, 2022 7 S/MIME signature verification extension to JMAP 8 draft-ietf-jmap-smime-04 10 Abstract 12 This document specifies an extension to JMAP for returning S/MIME 13 signature verification status. 15 Status of This Memo 17 This Internet-Draft is submitted in full conformance with the 18 provisions of BCP 78 and BCP 79. 20 Internet-Drafts are working documents of the Internet Engineering 21 Task Force (IETF). Note that other groups may also distribute 22 working documents as Internet-Drafts. The list of current Internet- 23 Drafts is at https://datatracker.ietf.org/drafts/current/. 25 Internet-Drafts are draft documents valid for a maximum of six months 26 and may be updated, replaced, or obsoleted by other documents at any 27 time. It is inappropriate to use Internet-Drafts as reference 28 material or to cite them other than as "work in progress." 30 This Internet-Draft will expire on January 13, 2022. 32 Copyright Notice 34 Copyright (c) 2021 IETF Trust and the persons identified as the 35 document authors. All rights reserved. 37 This document is subject to BCP 78 and the IETF Trust's Legal 38 Provisions Relating to IETF Documents 39 (https://trustee.ietf.org/license-info) in effect on the date of 40 publication of this document. Please review these documents 41 carefully, as they describe your rights and restrictions with respect 42 to this document. Code Components extracted from this document must 43 include Simplified BSD License text as described in Section 4.e of 44 the Trust Legal Provisions and are provided without warranty as 45 described in the Simplified BSD License. 47 Table of Contents 49 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 50 2. Conventions Used in This Document . . . . . . . . . . . . . . 2 51 3. Addition to the capabilities object . . . . . . . . . . . . . 2 52 4. Extension to Email/get for S/MIME signature verification . . 2 53 5. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 54 5.1. JMAP capability registration for "smime" . . . . . . . . 6 55 6. Security Considerations . . . . . . . . . . . . . . . . . . . 7 56 7. Normative References . . . . . . . . . . . . . . . . . . . . 7 57 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 7 59 1. Introduction 61 [RFC8621] is a JSON based application protocol for synchronising 62 email data between a client and a server. 64 This document describes an extension to JMAP for returning S/MIME 65 [RFC8551] signature verification status, without requiring a JMAP 66 client to download the signature body part and all signed body parts 67 (when multipart/signed media type is used) or to download and decode 68 CMS (when application/pkcs7-mime media type is used). 70 2. Conventions Used in This Document 72 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 73 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 74 document are to be interpreted as described in [RFC2119]. 76 3. Addition to the capabilities object 78 The capabilities object is returned as part of the standard JMAP 79 Session object; see the JMAP spec. Servers supporting _this_ 80 specification MUST add a property called "urn:ietf:params:jmap:smime" 81 to the capabilities object. 83 The value of this property is an empty object in both the JMAP 84 session _capabilities_ property and an account's 85 _accountCapabilities_ property. 87 4. Extension to Email/get for S/MIME signature verification 89 [RFC8621] defines Email/get method for retrieving message specific 90 information. This document defines the following pseudo values in 91 the _properties_ argument: 92 o *smimeStatus*: If "smimeStatus" is included in the list of 93 requested properties, it MUST be interpreted by the server as a 94 request to return "smimeStatus" response property. 96 o *smimeErrors*: If "smimeErrors" is included in the list of 97 requested properties, it MUST be interpreted by the server as a 98 request to return "smimeErrors" response property. 99 o *smimeVerifiedAt*: If "smimeVerifiedAt" is included in the list of 100 requested properties, it MUST be interpreted by the server as a 101 request to return "smimeVerifiedAt" response property. 102 o *smimeStatusAtDelivery*: If "smimeStatusAtDelivery" is included in 103 the list of requested properties, it MUST be interpreted by the 104 server as a request to return "smimeStatusAtDelivery" response 105 property. (It effectively the same as "smimeStatus" value calculated 106 at the date/time of deliver, as specified by "receivedAt".) 108 The "smimeStatus" response property is defined as follows: 110 smimeStatus: "String|null". null signifies that the message doesn't 111 contain any signature. This property contains the S/MIME signature 112 and certificate verification status calculated according to [RFC8551] 113 and [RFC8550]. Possible string values of the property are listed 114 below. Servers MAY return other values not defined below. Client 115 MUST treat unrecognized values as "unknown" or "signed/failed". Note 116 that the value of this property might change over time. 118 unknown S/MIME message, but it is neither signed, nor encrypted. 119 This can also be returned for a multipart/signed message which 120 contains unrecognized signing protocol (for example OpenPGP). 122 signed S/MIME signed message, but the signature was not yet 123 verified. Some servers might not attempt to verify signature 124 until a particular message is requested by the client. JMAP 125 servers compliant with this document SHOULD return "signed/ 126 verified" or "signed/failed" instead of this signature status. 128 signed/verified S/MIME signed message and the sender's signature was 129 successfully verified, sender matches the From header field and 130 the sender's certificate (and the certificate chain) is trusted 131 for signing. 133 signed/failed S/MIME signed message, but the signature failed to 134 verify. This might be a policy related decision (message signer 135 doesn't match the From header field), message was modified, the 136 signer's certificate has expired or was revoked, etc. 138 The "smimeStatusAtDelivery" response property has the same syntax as 139 "smimeStatus", but calculated at the "receivedAt" date/time. Unlike 140 "smimeStatus", the "smimeStatusAtDelivery" response property value is 141 immutable. "smimeStatusAtDelivery" allows clients to compare S/MIME 142 signature verification status at delivery with the current status as 143 returned by "smimeStatus", for example it helps to answer questions 144 like "was the signature valid at the time of delivery?". 146 The "smimeErrors" response property is defined as follows: 148 smimeErrors: "String[]|null". null signifies that the message doesn't 149 contain any signature or that there were no errors when verifying 150 S/MIME signature. (I.e. this property is non null only when the 151 corresponding "smimeStatus" response property value is "signed/ 152 failed".) Each string in the array is a human readable description 153 (in the language specified in Content-Language header field, if any) 154 of a problem with the signature or the signing certificate. (See 155 Section 3.8 of [RFC8620] in regards to how this is affected by the 156 language selection.) For example, the signing certificate might be 157 expired and the message From email address might not correspond to 158 any of the email addresses in the signing certificate. Or the 159 certificate might be expired and the JMAP server might be unable to 160 retrieve CRL for the certificate. In both of these cases there would 161 be 2 elements in the array. 163 The "smimeVerifiedAt" response property is defined as follows: 165 smimeVerifiedAt: "UTCDate|null" (server-set). null signifies that the 166 message doesn't contain any S/MIME signature or that there is a 167 signature, but there was no attempt to verify it. In all other cases 168 it is set to the date and time of when S/MIME signature was verified 169 the last time. 171 "smimeStatus" and "smimeErrors" values are calculated at the time the 172 corresponding JMAP request was processed (but see below about result 173 caching), not at the time when the message was generated (according 174 to it's Date header field value). In all cases "smimeVerifiedAt" is 175 set to time when "smimeStatus" and "smimeErrors" were last updated. 176 As recalculating these values is expensive for the server they MAY be 177 cached for up to 10 minutes from the moment when they were 178 calculated. 180 ["Email/get", { 181 "ids": [ "f123u987" ], 182 "properties": [ "mailboxIds", "from", "subject", "date", 183 "smimeStatusAtDelivery", "receivedAt" ] 184 }, "#1"] 186 This will result in the following response: 188 [["Email/get", { 189 "accountId": "abc", 190 "state": "41234123231", 191 "list": [ 192 { 193 id: "f123u457", 194 mailboxIds: { "f123": true }, 195 from: [{name: "Joe Bloggs", email: "joe@bloggs.example.net"}], 196 subject: "Dinner tonight?", 197 date: "2020-07-07T14:12:00Z", 198 smimeStatusAtDelivery: "signed/verified", 199 receivedAt: "2020-07-07T14:15:18Z" 200 } 201 ] 202 }, "#1"]] 204 Example 1: 206 ["Email/get", { 207 "ids": [ "af123u123" ], 208 "properties": [ "mailboxIds", "from", "subject", "date", 209 "smimeStatus", "smimeErrors", "smimeVerifiedAt" ] 210 }, "#1"] 212 This will result in the following response: 214 [["Email/get", { 215 "accountId": "abc", 216 "state": "41234123231", 217 "list": [ 218 { 219 id: "af123u123", 220 mailboxIds: { "f123": true }, 221 from: [{name: "Jane Doe", 222 email: "jdoe@example.com"}], 223 subject: "Company takeover", 224 date: "2020-01-31T23:00:00Z", 225 smimeStatus: "signed/failed", 226 smimeErrors: [ 227 "From email address doesn't match the certificate", 228 "Can't retrieve CRL from the CRL URL"], 229 "smimeVerifiedAt": "2020-03-01T12:11:19Z" 230 } 231 ] 232 }, "#1"]] 234 Example 2: 236 5. IANA Considerations 238 5.1. JMAP capability registration for "smime" 240 IANA is requested to register the "smime" JMAP Capability as follows: 242 Capability Name: "urn:ietf:params:jmap:smime" 244 Specification document: this document 246 Intended use: common 248 Change Controller: IETF 250 Security and privacy considerations: this document, Section 6 252 6. Security Considerations 254 Server side S/MIME signature verification requires the client to 255 trust server verification code and configuration to perform S/MIME 256 signature verification. For example, if the server is not configured 257 with some Trust Anchors, some messages will have "signed/failed" 258 status instead of "signed/verified". 260 Constant recalculation of S/MIME signature status can result in 261 Denial-of-Service condition. For that reason it is RECOMMENDED to 262 cache results of signature verification for 10 minutes. 264 7. Normative References 266 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 267 Requirement Levels", BCP 14, RFC 2119, 268 DOI 10.17487/RFC2119, March 1997, 269 . 271 [RFC8550] Schaad, J., Ramsdell, B., and S. Turner, "Secure/ 272 Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 273 Certificate Handling", RFC 8550, DOI 10.17487/RFC8550, 274 April 2019, . 276 [RFC8551] Schaad, J., Ramsdell, B., and S. Turner, "Secure/ 277 Multipurpose Internet Mail Extensions (S/MIME) Version 4.0 278 Message Specification", RFC 8551, DOI 10.17487/RFC8551, 279 April 2019, . 281 [RFC8620] Jenkins, N. and C. Newman, "The JSON Meta Application 282 Protocol (JMAP)", RFC 8620, DOI 10.17487/RFC8620, July 283 2019, . 285 [RFC8621] Jenkins, N. and C. Newman, "The JSON Meta Application 286 Protocol (JMAP) for Mail", RFC 8621, DOI 10.17487/RFC8621, 287 August 2019, . 289 Author's Address 291 Alexey Melnikov 292 Isode Ltd 293 14 Castle Mews 294 Hampton, Middlesex TW12 2NP 295 UK 297 EMail: Alexey.Melnikov@isode.com