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Gondwana, Ed. 3 Internet-Draft FastMail 4 Updates: 6638 (if approved) March 8, 2019 5 Intended status: Standards Track 6 Expires: September 9, 2019 8 CalDAV Extension for scheduling controls 9 draft-gondwana-caldav-scheduling-controls-01 11 Abstract 13 This document adds headers to control and restrict the scheduling 14 behaviour of CalDAV servers when updating calendaring resources. 16 Status of This Memo 18 This Internet-Draft is submitted in full conformance with the 19 provisions of BCP 78 and BCP 79. 21 Internet-Drafts are working documents of the Internet Engineering 22 Task Force (IETF). Note that other groups may also distribute 23 working documents as Internet-Drafts. The list of current Internet- 24 Drafts is at https://datatracker.ietf.org/drafts/current/. 26 Internet-Drafts are draft documents valid for a maximum of six months 27 and may be updated, replaced, or obsoleted by other documents at any 28 time. It is inappropriate to use Internet-Drafts as reference 29 material or to cite them other than as "work in progress." 31 This Internet-Draft will expire on September 9, 2019. 33 Copyright Notice 35 Copyright (c) 2019 IETF Trust and the persons identified as the 36 document authors. All rights reserved. 38 This document is subject to BCP 78 and the IETF Trust's Legal 39 Provisions Relating to IETF Documents 40 (https://trustee.ietf.org/license-info) in effect on the date of 41 publication of this document. Please review these documents 42 carefully, as they describe your rights and restrictions with respect 43 to this document. Code Components extracted from this document must 44 include Simplified BSD License text as described in Section 4.e of 45 the Trust Legal Provisions and are provided without warranty as 46 described in the Simplified BSD License. 48 Table of Contents 50 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2 51 2. Conventions Used In This Document . . . . . . . . . . . . . . 3 52 3. Extending the CalDAV OPTIONS response . . . . . . . . . . . . 3 53 3.1. Example: Using OPTIONS for the Discovery of Scheduling 54 Controls Support . . . . . . . . . . . . . . . . . . . . 3 55 4. New headers . . . . . . . . . . . . . . . . . . . . . . . . . 3 56 4.1. Scheduling header . . . . . . . . . . . . . . . . . . . . 3 57 4.2. Schedule-User-Address header . . . . . . . . . . . . . . 4 58 5. Implementation considerations . . . . . . . . . . . . . . . . 5 59 6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 5 60 7. Security Considerations . . . . . . . . . . . . . . . . . . . 5 61 8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 5 62 9. Version History . . . . . . . . . . . . . . . . . . . . . . . 5 63 9.1. v01, 2019-03-08 . . . . . . . . . . . . . . . . . . . . . 5 64 9.2. v00, 2019-02-08 . . . . . . . . . . . . . . . . . . . . . 5 65 10. Normative References . . . . . . . . . . . . . . . . . . . . 6 66 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 6 68 1. Introduction 70 [RFC6638] defines automatic scheduling operations for resources 71 stored on [!@RFC4791] CalDAV servers. 73 [RFC6638] defines the "Schedule-Reply" header in Section 8.1, however 74 this header is not sufficient for controlling scheduling in all 75 cases. 77 Cases where it might be necessary to update the data store on a 78 server without causing scheduling messages to be sent include backup 79 after a data loss event on the server, or importing calendar events 80 from another system. 82 Calendar server operators deal with these other needs by either using 83 a different method than CalDAV to update their server, or by adding a 84 custom method to suppress scheduling. This document defines a 85 standard method to suppress scheduling, allowing CalDAV to be 86 directly used for restores and imports. 88 Complex sites can have users who have multiple aliases, and in the 89 most complex cases, a user may have multiple identities who are 90 present on a scheduling event as organizer and/or attendee. When an 91 event is updated over CalDAV, the server must calculate or guess 92 which of those addresses the current user is acting as. This 93 document defines a header which allows the client to inform the 94 server precisely which address they are acting as when adding, 95 modifying or removing a resource. 97 2. Conventions Used In This Document 99 In examples, "C:" indicates data sent by a client that is connected 100 to a server. "S:" indicates data sent by the server to the client. 102 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 103 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 104 document are to be interpreted as described in [RFC2119] when they 105 appear in ALL CAPS. These words may also appear in this document in 106 lower case as plain English words, absent their normative meanings. 108 3. Extending the CalDAV OPTIONS response 110 A server supporting the features described in this document MUST 111 include "scheduling-controls" as a field in the DAV response header 112 from an OPTIONS request. A value of "scheduling-controls" in the DAV 113 response header indicates to clients that the server supports all the 114 requirements specified in this document. 116 3.1. Example: Using OPTIONS for the Discovery of Scheduling Controls 117 Support 119 Request: 121 OPTIONS /home/brong/calendars/ HTTP/1.1 122 Host: cal.example.com 124 Response: 126 HTTP/1.1 200 OK 127 Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE 128 Allow: PROPFIND, PROPPATCH, LOCK, UNLOCK, REPORT, ACL 129 DAV: 1, 2, 3, access-control, calendar-access, 130 scheduling-controls 131 Date: Thu, 8 Feb 2019 10:16:37 GMT 132 Content-Length: 0 134 4. New headers 136 This document adds two new headers for use on PUT, PROPPATCH and 137 DELETE: 139 4.1. Scheduling header 141 Scheduling: {all|none|internal-only|external-only|X-...} 143 Default: all 144 Not providing this header, or providing the value of "all", instructs 145 the server to follow the behaviour in [RFC6638] Section 3.2. 147 Providing the value "none" instructs the server to perform no 148 scheduling at all, and to just store the event (useful for restoring 149 from backup) 151 The value "internal-only" instructs the server to update the events 152 in other calendars within its system where that can be done silently, 153 but not to send visible notifications to users (where permitted by 154 policy). This is useful when importing multiple related calendars 155 into a new system without flooding external parties with 156 notifications. 158 The value "external-only" instructs the server to import the data 159 without updating local calendars, but to send notifications to 160 external attendees so they are aware of the event. This is useful 161 when migrating calendar events to a new system where external parties 162 need to have a way to update their participation status in the new 163 system. 165 e.g. 167 Scheduling: none 169 TODO: specify error codes 171 4.2. Schedule-User-Address header 173 Schedule-User-Address: URI 175 Default: not present 177 If this header is not present, the server will calculate the address 178 from the authenticated user, or from the CALDAV:schedule-user-address 179 property on the calendar or principal. 181 If this header is provided, it overrides the server's internal 182 calculation, and informs the server to perform any scheduling as the 183 specified user. 185 TODO: specify error codes 187 e.g. 189 Schedule-User-Address: mailto:foo@example.com 191 5. Implementation considerations 193 Any server implementing this extension MUST ensure it has a way to 194 validate Schedule-User-Address settings. 196 6. IANA Considerations 198 TODO: IANA request for OPTIONS item 200 TODO: IANA request for named headers 202 7. Security Considerations 204 The "Scheduling" header only allows reduction of the cases in which 205 the server will creating scheduling requests. This is generally good 206 for user privacy, allowing copies of events to be updated without 207 notifying the owner or attendees. This is particularly valuable for 208 cleaning up spam. 210 The "Schedule-User-Address" header allows the client to override the 211 server choice of address for the user to act as. Servers MUST ensure 212 that the authenticated user has permission to act as the specified 213 address, as well as applying any local policy limitations. 215 8. Acknowledgments 217 o Lucia Kristiansen, Google 219 o CalConnect 221 o The calext working group 223 9. Version History 225 Remove before publishing 227 9.1. v01, 2019-03-08 229 o correct name in acknowledgements 231 9.2. v00, 2019-02-08 233 o Initial draft based on discussion at CalConnect about Google and 234 FastMail private implementations. 236 10. Normative References 238 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 239 Requirement Levels", BCP 14, RFC 2119, 240 DOI 10.17487/RFC2119, March 1997, 241 . 243 [RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to 244 CalDAV", RFC 6638, DOI 10.17487/RFC6638, June 2012, 245 . 247 Author's Address 249 Bron Gondwana (editor) 250 FastMail 251 Level 2, 114 William St 252 Melbourne VIC 3000 253 Australia 255 Email: brong@fastmailteam.com 256 URI: https://www.fastmail.com