mirror of
https://git.friendi.ca/friendica/friendica-addons.git
synced 2024-11-05 14:42:55 +00:00
560 lines
17 KiB
Text
560 lines
17 KiB
Text
|
||
|
||
|
||
Calendar Server Extension C. Daboo
|
||
Apple Computer
|
||
May 3, 2007
|
||
|
||
|
||
Calendar User Proxy Functionality in CalDAV
|
||
caldav-cu-proxy-02
|
||
|
||
Abstract
|
||
|
||
This specification defines an extension to CalDAV that makes it easy
|
||
for clients to setup and manage calendar user proxies, using the
|
||
WebDAV Access Control List extension as a basis.
|
||
|
||
|
||
Table of Contents
|
||
|
||
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 2
|
||
2. Conventions Used in This Document . . . . . . . . . . . . . . 2
|
||
3. Overview . . . . . . . . . . . . . . . . . . . . . . . . . . . 3
|
||
3.1. Server . . . . . . . . . . . . . . . . . . . . . . . . . . 3
|
||
3.2. Client . . . . . . . . . . . . . . . . . . . . . . . . . . 3
|
||
4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . . 4
|
||
5. New features in CalDAV . . . . . . . . . . . . . . . . . . . . 4
|
||
5.1. Proxy Principal Resource . . . . . . . . . . . . . . . . . 4
|
||
5.2. Privilege Provisioning . . . . . . . . . . . . . . . . . . 8
|
||
6. Security Considerations . . . . . . . . . . . . . . . . . . . 9
|
||
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
|
||
8. Normative References . . . . . . . . . . . . . . . . . . . . . 9
|
||
Appendix A. Acknowledgments . . . . . . . . . . . . . . . . . . . 9
|
||
Appendix B. Change History . . . . . . . . . . . . . . . . . . . 10
|
||
Author's Address . . . . . . . . . . . . . . . . . . . . . . . . . 10
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Daboo [Page 1]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
1. Introduction
|
||
|
||
CalDAV [RFC4791] provides a way for calendar users to store calendar
|
||
data and exchange this data via scheduling operations. Based on the
|
||
WebDAV protocol [RFC2518], it also includes the ability to manage
|
||
access to calendar data via the WebDAV ACL extension [RFC3744].
|
||
|
||
It is often common for a calendar user to delegate some form of
|
||
responsibility for their calendar and schedules to another calendar
|
||
user (e.g., a boss allows an assistant to check a calendar or to send
|
||
and accept scheduling invites on his behalf). The user handling the
|
||
calendar data on behalf of someone else is often referred to as a
|
||
"calendar user proxy".
|
||
|
||
Whilst CalDAV does have fine-grained access control features that can
|
||
be used to setup complex sharing and management of calendars, often
|
||
the proxy behavior required is an "all-or-nothing" approach - i.e.
|
||
the proxy has access to all the calendars or to no calendars (in
|
||
which case they are of course not a proxy). So a simple way to
|
||
manage access to an entire set of calendars and scheduling ability
|
||
would be handy.
|
||
|
||
In addition, calendar user agents will often want to display to a
|
||
user who has proxy access to their calendars, or to whom they are
|
||
acting as a proxy. Again, CalDAV's access control discovery and
|
||
report features can be used to do that, but with fine-grained control
|
||
that exists, it can be hard to tell who is a "real" proxy as opposed
|
||
to someone just granted rights to some subset of calendars. Again, a
|
||
simple way to discover proxy information would be handy.
|
||
|
||
|
||
2. Conventions Used in This Document
|
||
|
||
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
|
||
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
|
||
document are to be interpreted as described in [RFC2119].
|
||
|
||
When XML element types in the namespace "DAV:" are referenced in this
|
||
document outside of the context of an XML fragment, the string "DAV:"
|
||
will be prefixed to the element type names.
|
||
|
||
When XML element types in the namespaces "DAV:" and
|
||
"urn:ietf:params:xml:ns:caldav" are referenced in this document
|
||
outside of the context of an XML fragment, the string "DAV:" and
|
||
"CALDAV:" will be prefixed to the element type names respectively.
|
||
|
||
The namespace "http://calendarserver.org/ns/" is used for XML
|
||
elements defined in this specification. When XML element types in
|
||
|
||
|
||
|
||
Daboo [Page 2]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
this namespace are referenced in this document outside of the context
|
||
of an XML fragment, the string "CS:" will be prefixed to the element
|
||
type names respectively.
|
||
|
||
|
||
3. Overview
|
||
|
||
3.1. Server
|
||
|
||
For each calendar user principal on the server, the server will
|
||
generate two group principals - "proxy groups". One is used to hold
|
||
the list of principals who have read-only proxy access to the main
|
||
principal's calendars, the other holds the list of principals who
|
||
have read-write and scheduling proxy access. NB these new group
|
||
principals would have no equivalent in Open Directory.
|
||
|
||
Privileges on each "proxy group" principal will be set so that the
|
||
"owner" has the ability to change property values.
|
||
|
||
The "proxy group" principals will be child resources of the user
|
||
principal resource with specific resource types and thus are easy to
|
||
discover. As a result the user principal resources will also be
|
||
collection resources.
|
||
|
||
When provisioning the calendar user home collection, the server will:
|
||
|
||
a. Add an ACE to the calendar home collection giving the read-only
|
||
"proxy group" inheritable read access.
|
||
|
||
b. Add an ACE to the calendar home collection giving the read-write
|
||
"proxy group" inheritable read-write access.
|
||
|
||
c. Add an ACE to each of the calendar Inbox and Outbox collections
|
||
giving the CALDAV:schedule privilege
|
||
[I-D.desruisseaux-caldav-sched] to the read-write "proxy group".
|
||
|
||
3.2. Client
|
||
|
||
A client can see who the proxies are for the current principal by
|
||
examining the principal resource for the two "proxy group" properties
|
||
and then looking at the DAV:group-member-set property of each.
|
||
|
||
The client can edit the list of proxies for the current principal by
|
||
editing the DAV:group-member-set property on the relevant "proxy
|
||
group" principal resource.
|
||
|
||
The client can find out who the current principal is a proxy for by
|
||
running a DAV:principal-match REPORT on the principal collection.
|
||
|
||
|
||
|
||
Daboo [Page 3]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
Alternatively, the client can find out who the current principal is a
|
||
proxy for by examining the DAV:group-membership property on the
|
||
current principal resource looking for membership in other users'
|
||
"proxy groups".
|
||
|
||
|
||
4. Open Issues
|
||
|
||
1. Do we want to separate read-write access to calendars vs the
|
||
ability to schedule as a proxy?
|
||
|
||
2. We may want to restrict changing properties on the proxy group
|
||
collections to just the DAV:group-member-set property?
|
||
|
||
3. There is no way for a proxy to be able to manage the list of
|
||
proxies. We could allow the main calendar user DAV:write-acl on
|
||
their "proxy group" principals, in which case they could grant
|
||
others the right to modify the group membership.
|
||
|
||
4. Should the "proxy group" principals also be collections given
|
||
that the regular principal resources will be?
|
||
|
||
|
||
5. New features in CalDAV
|
||
|
||
5.1. Proxy Principal Resource
|
||
|
||
Each "regular" principal resource that needs to allow calendar user
|
||
proxy support MUST be a collection resource. i.e. in addition to
|
||
including the DAV:principal XML element in the DAV:resourcetype
|
||
property on the resource, it MUST also include the DAV:collection XML
|
||
element.
|
||
|
||
Each "regular" principal resource MUST contain two child resources
|
||
with names "calendar-proxy-read" and "calendar-proxy-write" (note
|
||
that these are only suggested names - the server could choose any
|
||
unique name for these). These resources are themselves principal
|
||
resources that are groups contain the list of principals for calendar
|
||
users who can act as a read-only or read-write proxy respectively.
|
||
|
||
The server MUST include the CS:calendar-proxy-read or CS:calendar-
|
||
proxy-write XML elements in the DAV:resourcetype property of the
|
||
child resources, respectively. This allows clients to discover the
|
||
"proxy group" principals by using a PROPFIND, Depth:1 request on the
|
||
current user's principal resource and requesting the DAV:resourcetype
|
||
property be returned. The element type declarations are:
|
||
|
||
|
||
|
||
|
||
|
||
Daboo [Page 4]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
<!ELEMENT calendar-proxy-read EMPTY>
|
||
|
||
<!ELEMENT calendar-proxy-write EMPTY>
|
||
|
||
The server MUST allow the "parent" principal to change the DAV:group-
|
||
member-set property on each of the "child" "proxy group" principal
|
||
resources. When a principal is listed as a member of the "child"
|
||
resource, the server MUST include the "child" resource URI in the
|
||
DAV:group-membership property on the included principal resource.
|
||
Note that this is just "normal" behavior for a group principal.
|
||
|
||
An example principal resource layout might be:
|
||
|
||
+ /
|
||
+ principals/
|
||
+ users/
|
||
+ cyrus/
|
||
calendar-proxy-read
|
||
calendar-proxy-write
|
||
+ red/
|
||
calendar-proxy-read
|
||
calendar-proxy-write
|
||
+ wilfredo/
|
||
calendar-proxy-read
|
||
calendar-proxy-write
|
||
|
||
If the principal "cyrus" wishes to have the principal "red" act as a
|
||
calendar user proxy on his behalf and have the ability to change
|
||
items on his calendar or schedule meetings on his behalf, then he
|
||
would add the principal resource URI for "red" to the DAV:group-
|
||
member-set property of the principal resource /principals/users/
|
||
cyrus/calendar-proxy-write, giving:
|
||
|
||
<DAV:group-member-set>
|
||
<DAV:href>/principals/users/red/</DAV:href>
|
||
</DAV:group-member-set>
|
||
|
||
The DAV:group-membership property on the resource /principals/users/
|
||
red/ would be:
|
||
|
||
<DAV:group-membership>
|
||
<DAV:href>/principals/users/cyrus/calendar-proxy-write</DAV:href>
|
||
</DAV:group-membership>
|
||
|
||
If the principal "red" was also a read-only proxy for the principal
|
||
"wilfredo", then the DA:group-membership property on the resource
|
||
/principals/users/red/ would be:
|
||
|
||
|
||
|
||
|
||
Daboo [Page 5]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
<DAV:group-membership>
|
||
<DAV:href>/principals/users/cyrus/calendar-proxy-write</DAV:href>
|
||
<DAV:href>/principals/users/wilfredo/calendar-proxy-read</DAV:href>
|
||
</DAV:group-membership>
|
||
|
||
Thus a client can discover to which principals a particular principal
|
||
is acting as a calendar user proxy for by examining the DAV:group-
|
||
membership property.
|
||
|
||
An alternative to discovering which principals a user can proxy as is
|
||
to use the WebDAV ACL principal-match report, targeted at the
|
||
principal collections available on the server.
|
||
|
||
Example:
|
||
|
||
>> Request <<
|
||
|
||
REPORT /principals/ HTTP/1.1
|
||
Host: cal.example.com
|
||
Depth: 0
|
||
Content-Type: application/xml; charset="utf-8"
|
||
Content-Length: xxxx
|
||
Authorization: Digest username="red",
|
||
realm="cal.example.com", nonce="...",
|
||
uri="/principals/", response="...", opaque="..."
|
||
|
||
<?xml version="1.0" encoding="utf-8" ?>
|
||
<D:principal-match xmlns:D="DAV:">
|
||
<D:self/>
|
||
<D:prop>
|
||
<D:resourcetype/>
|
||
</D:prop>
|
||
</D:principal-match>
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Daboo [Page 6]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
>> Response <<
|
||
|
||
HTTP/1.1 207 Multi-Status
|
||
Date: Fri, 10 Nov 2006 09:32:12 GMT
|
||
Content-Type: application/xml; charset="utf-8"
|
||
Content-Length: xxxx
|
||
|
||
<?xml version="1.0" encoding="utf-8" ?>
|
||
<D:multistatus xmlns:D="DAV:"
|
||
xmlns:A="http://calendarserver.org/ns/">
|
||
<D:response>
|
||
<D:href>/principals/users/red/</D:href>
|
||
<D:propstat>
|
||
<D:prop>
|
||
<D:resourcetype>
|
||
<D:principal/>
|
||
<D:collection/>
|
||
</D:resourcetype>
|
||
</D:prop>
|
||
<D:status>HTTP/1.1 200 OK</D:status>
|
||
</D:propstat>
|
||
</D:response>
|
||
<D:response>
|
||
<D:href>/principals/users/cyrus/calendar-proxy-write</D:href>
|
||
<D:propstat>
|
||
<D:prop>
|
||
<D:resourcetype>
|
||
<D:principal/>
|
||
<A:calendar-proxy-write/>
|
||
</D:resourcetype>
|
||
</D:prop>
|
||
<D:status>HTTP/1.1 200 OK</D:status>
|
||
</D:propstat>
|
||
</D:response>
|
||
<D:response>
|
||
<D:href>/principals/users/wilfredo/calendar-proxy-read</D:href>
|
||
<D:propstat>
|
||
<D:prop>
|
||
<D:resourcetype>
|
||
<D:principal/>
|
||
<A:calendar-proxy-read/>
|
||
</D:resourcetype>
|
||
</D:prop>
|
||
<D:status>HTTP/1.1 200 OK</D:status>
|
||
</D:propstat>
|
||
</D:response>
|
||
</D:multistatus>
|
||
|
||
|
||
|
||
|
||
Daboo [Page 7]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
5.2. Privilege Provisioning
|
||
|
||
In order for a calendar user proxy to be able to access the calendars
|
||
of the user they are proxying for the server MUST ensure that the
|
||
privileges on the relevant calendars are setup accordingly:
|
||
|
||
The DAV:read privilege MUST be granted for read-only and read-
|
||
write calendar user proxy principals
|
||
|
||
The DAV:write privilege MUST be granted for read-write calendar
|
||
user proxy principals.
|
||
|
||
Additionally, the CalDAV scheduling Inbox and Outbox calendar
|
||
collections for the user allowing proxy access, MUST have the CALDAV:
|
||
schedule privilege [I-D.desruisseaux-caldav-sched] granted for read-
|
||
write calendar user proxy principals.
|
||
|
||
Note that with a suitable repository layout, a server may be able to
|
||
grant the appropriate privileges on a parent collection and ensure
|
||
that all the contained collections and resources inherit that. For
|
||
example, given the following repository layout:
|
||
|
||
+ /
|
||
+ calendars/
|
||
+ users/
|
||
+ cyrus/
|
||
inbox
|
||
outbox
|
||
home
|
||
work
|
||
+ red/
|
||
inbox
|
||
outbox
|
||
work
|
||
soccer
|
||
+ wilfredo/
|
||
inbox
|
||
outbox
|
||
home
|
||
work
|
||
flying
|
||
|
||
In order for the principal "red" to act as a read-write proxy for the
|
||
principal "cyrus", the following WebDAV ACE will need to be granted
|
||
on the resource /calendars/users/cyrus/ and all children of that
|
||
resource:
|
||
|
||
|
||
|
||
|
||
|
||
Daboo [Page 8]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
<DAV:ace>
|
||
<DAV:principal>
|
||
<DAV:href>/principals/users/cyrus/calendar-proxy-write</DAV:href>
|
||
</DAV:principal>
|
||
<DAV:privileges>
|
||
<DAV:grant><DAV:read/><DAV:write/></DAV:grant>
|
||
</DAV:privileges>
|
||
</DAV:ace>
|
||
|
||
|
||
6. Security Considerations
|
||
|
||
TBD
|
||
|
||
|
||
7. IANA Considerations
|
||
|
||
This document does not require any actions on the part of IANA.
|
||
|
||
|
||
8. Normative References
|
||
|
||
[I-D.desruisseaux-caldav-sched]
|
||
Desruisseaux, B., "Scheduling Extensions to CalDAV",
|
||
draft-desruisseaux-caldav-sched-03 (work in progress),
|
||
January 2007.
|
||
|
||
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
|
||
Requirement Levels", BCP 14, RFC 2119, March 1997.
|
||
|
||
[RFC2518] Goland, Y., Whitehead, E., Faizi, A., Carter, S., and D.
|
||
Jensen, "HTTP Extensions for Distributed Authoring --
|
||
WEBDAV", RFC 2518, February 1999.
|
||
|
||
[RFC3744] Clemm, G., Reschke, J., Sedlar, E., and J. Whitehead, "Web
|
||
Distributed Authoring and Versioning (WebDAV) Access
|
||
Control Protocol", RFC 3744, May 2004.
|
||
|
||
[RFC4791] Daboo, C., Desruisseaux, B., and L. Dusseault,
|
||
"Calendaring Extensions to WebDAV (CalDAV)", RFC 4791,
|
||
March 2007.
|
||
|
||
|
||
Appendix A. Acknowledgments
|
||
|
||
This specification is the result of discussions between the Apple
|
||
calendar server and client teams.
|
||
|
||
|
||
|
||
|
||
Daboo [Page 9]
|
||
|
||
CalDAV Proxy May 2007
|
||
|
||
|
||
Appendix B. Change History
|
||
|
||
Changes from -00:
|
||
|
||
1. Updated to RFC 4791 reference.
|
||
|
||
Changes from -00:
|
||
|
||
1. Added more details on actual CalDAV protocol changes.
|
||
|
||
2. Changed namespace from http://apple.com/ns/calendarserver/ to
|
||
http://calendarserver.org/ns/.
|
||
|
||
3. Made "proxy group" principals child resources of their "owner"
|
||
principals.
|
||
|
||
4. The "proxy group" principals now have their own resourcetype.
|
||
|
||
|
||
Author's Address
|
||
|
||
Cyrus Daboo
|
||
Apple Computer, Inc.
|
||
1 Infinite Loop
|
||
Cupertino, CA 95014
|
||
USA
|
||
|
||
Email: cyrus@daboo.name
|
||
URI: http://www.apple.com/
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
|
||
Daboo [Page 10]
|
||
|