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Gondwana, Ed. 3 Internet-Draft FastMail 4 Updates: 6638 (if approved) February 8, 2019 5 Intended status: Standards Track 6 Expires: August 12, 2019 8 CalDAV Extension for scheduling controls 9 draft-gondwana-caldav-scheduling-controls-00 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 August 12, 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. Normative References . . . . . . . . . . . . . . . . . . . . 5 63 Author's Address . . . . . . . . . . . . . . . . . . . . . . . . 5 65 1. Introduction 67 [RFC6638] defines automatic scheduling operations for resources 68 stored on [!@RFC4791] CalDAV servers. 70 [RFC6638] defines the "Schedule-Reply" header in Section 8.1, however 71 this header is not sufficient for controlling scheduling in all 72 cases. 74 Cases where it might be necessary to update the data store on a 75 server without causing scheduling messages to be sent include backup 76 after a data loss event on the server, or importing calendar events 77 from another system. 79 Calendar server operators deal with these other needs by either using 80 a different method than CalDAV to update their server, or by adding a 81 custom method to suppress scheduling. This document defines a 82 standard method to suppress scheduling, allowing CalDAV to be 83 directly used for restores and imports. 85 Complex sites can have users who have multiple aliases, and in the 86 most complex cases, a user may have multiple identities who are 87 present on a scheduling event as organizer and/or attendee. When an 88 event is updated over CalDAV, the server must calculate or guess 89 which of those addresses the current user is acting as. This 90 document defines a header which allows the client to inform the 91 server precisely which address they are acting as when adding, 92 modifying or removing a resource. 94 2. Conventions Used In This Document 96 In examples, "C:" indicates data sent by a client that is connected 97 to a server. "S:" indicates data sent by the server to the client. 99 The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", 100 "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this 101 document are to be interpreted as described in [RFC2119] when they 102 appear in ALL CAPS. These words may also appear in this document in 103 lower case as plain English words, absent their normative meanings. 105 3. Extending the CalDAV OPTIONS response 107 A server supporting the features described in this document MUST 108 include "scheduling-controls" as a field in the DAV response header 109 from an OPTIONS request. A value of "scheduling-controls" in the DAV 110 response header indicates to clients that the server supports all the 111 requirements specified in this document. 113 3.1. Example: Using OPTIONS for the Discovery of Scheduling Controls 114 Support 116 Request: 118 OPTIONS /home/brong/calendars/ HTTP/1.1 119 Host: cal.example.com 121 Response: 123 HTTP/1.1 200 OK 124 Allow: OPTIONS, GET, HEAD, POST, PUT, DELETE, TRACE, COPY, MOVE 125 Allow: PROPFIND, PROPPATCH, LOCK, UNLOCK, REPORT, ACL 126 DAV: 1, 2, 3, access-control, calendar-access, 127 scheduling-controls 128 Date: Thu, 8 Feb 2019 10:16:37 GMT 129 Content-Length: 0 131 4. New headers 133 This document adds two new headers for use on PUT, PROPPATCH and 134 DELETE: 136 4.1. Scheduling header 138 Scheduling: {all|none|internal-only|external-only|X-...} 140 Default: all 141 Not providing this header, or providing the value of "all", instructs 142 the server to follow the behaviour in [RFC6638] Section 3.2. 144 Providing the value "none" instructs the server to perform no 145 scheduling at all, and to just store the event (useful for restoring 146 from backup) 148 The value "internal-only" instructs the server to update the events 149 in other calendars within its system where that can be done silently, 150 but not to send visible notifications to users (where permitted by 151 policy). This is useful when importing multiple related calendars 152 into a new system without flooding external parties with 153 notifications. 155 The value "external-only" instructs the server to import the data 156 without updating local calendars, but to send notifications to 157 external attendees so they are aware of the event. This is useful 158 when migrating calendar events to a new system where external parties 159 need to have a way to update their participation status in the new 160 system. 162 e.g. 164 Scheduling: none 166 TODO: specify error codes 168 4.2. Schedule-User-Address header 170 Schedule-User-Address: URI 172 Default: not present 174 If this header is not present, the server will calculate the address 175 from the authenticated user, or from the CALDAV:schedule-user-address 176 property on the calendar or principal. 178 If this header is provided, it overrides the server's internal 179 calculation, and informs the server to perform any scheduling as the 180 specified user. 182 TODO: specify error codes 184 e.g. 186 Schedule-User-Address: mailto:foo@example.com 188 5. Implementation considerations 190 Any server implementing this extension MUST ensure it has a way to 191 validate Schedule-User-Address settings. 193 6. IANA Considerations 195 TODO: IANA request for OPTIONS item 197 TODO: IANA request for named headers 199 7. Security Considerations 201 The "Scheduling" header only allows reduction of the cases in which 202 the server will creating scheduling requests. This is generally good 203 for user privacy, allowing copies of events to be updated without 204 notifying the owner or attendees. This is particularly valuable for 205 cleaning up spam. 207 The "Schedule-User-Address" header allows the client to override the 208 server choice of address for the user to act as. Servers MUST ensure 209 that the authenticated user has permission to act as the specified 210 address, as well as applying any local policy limitations. 212 8. Acknowledgments 214 o Lucia Federova, Google 216 o CalConnect 218 o The calext working group 220 9. Normative References 222 [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate 223 Requirement Levels", BCP 14, RFC 2119, 224 DOI 10.17487/RFC2119, March 1997, 225 . 227 [RFC6638] Daboo, C. and B. Desruisseaux, "Scheduling Extensions to 228 CalDAV", RFC 6638, DOI 10.17487/RFC6638, June 2012, 229 . 231 Author's Address 232 Bron Gondwana (editor) 233 FastMail 234 Level 2, 114 William St 235 Melbourne VIC 3000 236 Australia 238 Email: brong@fastmailteam.com 239 URI: https://www.fastmail.com