CalDAV
******


Configuration
=============


calendarprefix
^^^^^^^^^^^^^^

   *This shows the default value: change it in imapd.conf to suit your
   needs.*

   "calendarprefix:" #calendars

      The prefix for the calendar mailboxes hierarchies.  The
      hierarchy delimiter will be automatically appended.  The public
      calendar hierarchy will be at the toplevel of the shared
      namespace.  A user's personal calendar hierarchy will be a child
      of their Inbox.

When enabled, the CalDAV module allows Cyrus to function as a calendar
and scheduling server. This module uses a subset of the mailbox
hierarchy as calendar collections, the toplevel of which is specified
by the "calendarprefix" option. The public calendar hierarchy will
reside at the toplevel of the shared mailbox namespace. A user's
personal calendar hierarchy will be a child of their Inbox.

For example, using the default value for calendarprefix, a calendar
named Default for user "murch" would reside in the mailbox named
"user.murch.#calendars.Default".

Warning:

  Note that mailboxes in the calendar hierarchies (those under
  calendarprefix) **should not** be accessed with an IMAP client as
  doing so will leave a mailbox in a state unsuitable for CalDAV. To
  this end, calendar mailboxes will not returned by Cyrus imapd in
  response to an IMAP client's request for the available calendar
  list, but Cyrus imapd can not otherwise prevent an IMAP client from
  accessing them.


caldav_allowscheduling
^^^^^^^^^^^^^^^^^^^^^^

   *This shows the default value: change it in imapd.conf to suit your
   needs.*

   "caldav_allowscheduling:" on

      Enable calendar scheduling operations. If set to "apple", the
      server will emulate Apple CalendarServer behavior as closely as
      possible. Allowed values: *off*, *on*, *apple*

By default, the CalDAV module will automatically perform scheduling
operations when a scheduling object (invite or reply) is stored on or
deleted from the server. Support for the calendar-auto-schedule
feature can be disabled with the "caldav_allowscheduling" option.


Administration
==============

The CalDAV module will *automatically* create the required calendars
for a user the first time that the user authenticates to the CalDAV
server. Note that the user MUST have an existing IMAP Inbox in order
for the calendars to be created.


autocreate options
^^^^^^^^^^^^^^^^^^

   *This shows the default value: change it in imapd.conf to suit your
   needs.*

   "caldav_create_default:" 1

      Create the 'Default' calendar if it doesn't already exist.

   "caldav_create_attach:" 1

      Create the 'Attachments' collection if it doesn't already exist.

   "caldav_create_sched:" 1

      Create the 'Inbox' and 'Outbox' calendars if they don't already
      exist.

Autocreate of the various calendars can be disabled with the
"caldav_create_default/sched/attach" options, if you have an alternate
mechanism to create calendars.

There is also a Cyrus web GUI for managing calendar resources. It
allows you to:

   * Create new collections, with whichever components are required

   * Alter existing collections with different components

   * Subscribe or download existing collections via prepared URLs

   * Set visibility attributes such as Public or Transparent

   * Delete existing collections

The Cyrus web GUI for CalDAV Collection Management is disabled by
default, but can be enabled with the "caldav_allowcalendaradmin"
option.


caldav_allowcalendaradmin
^^^^^^^^^^^^^^^^^^^^^^^^^

   *This shows the default value: change it in imapd.conf to suit your
   needs.*

   "caldav_allowcalendaradmin:" 0

      Enable per-user calendar administration web UI on the CalDAV
      server.

To access the Cyrus web GUI for CalDAV Collection Management, point a
web browser at "https://<servername>/dav/calendars/user/<username>"


Calendar access controls
------------------------

The CalDAV module uses the same access controls as the other Cyrus
services. The cyradm(8) tool can be used to adjust ACLs on calendars
as needed. The tables below show how the access controls are used by
the CalDAV module.




Freebusy URL
============

When enabled in conjunction with the CalDAV module, the Freebusy URL
module allows non-CalDAV and/or remote calendaring clients to query
the freebusy information of Cyrus CalDAV users.

Access to the freebusy information is controlled by the "freebusy" ACL
(9) on a user's home calendar collection. (e.g. a mailbox named
"user.murch.#calendars"). To enable unauthenticated users (non-Cyrus)
to access freebusy information, the freebusy ACL must be given to
"anyone".

Freebusy information, consolidating the data of all user's calendars,
is accessed via URLs of the following form:
"https://<servername>/freebusy/user/<userid>".  Querying individual
CalDAV collections, when they have explicitly "freebusy" ACL (9) set,
is done via
"https://<servername>/freebusy/user/<userid>/<collection>".

Query parameters can be added to the URL per Section 4 of Freebusy
Read URL, allowing the user to choose to set the start, end, period
and format of their query results.


Time Zone Distribution Service (TZDist)
=======================================


What is TZDist
--------------

The TZDist module allows Cyrus to function as a Time Zone Distribution
Service (**RFC 7808** and **RFC 7809**), providing time zone data for
CalDAV and calendaring clients, without having to wait for their
client vendor and/or OS vendor to update the timezone information. The
responsibility for keeping the time zone information up to date then
falls upon the Cyrus administrator.

TZDist is optional: without Cyrus having TZDist enabled, calendar
clients should still be able to get their timezone information from
their client or their OS.

TZDist strips known VTIMEZONEs from incoming iCalendar data (as
advertised by the "calendar-no-timezone" DAV option from **RFC
7809**).


Configuration
-------------


zoneinfo config
^^^^^^^^^^^^^^^

   *This shows the default value: change it in imapd.conf to suit your
   needs.*

   "zoneinfo_db_path:" <none>

      The absolute path to the zoneinfo db file.  If not specified,
      will be configdirectory/zoneinfo.db



   "zoneinfo_db:" twoskip

      The cyrusdb backend to use for zoneinfo.  This database is used
      by the "tzdist" *httpmodules*, and is managed by
      **ctl_zoneinfo(8)**. Allowed values: *flat*, *skiplist*,
      *twoskip*, *zeroskip*



   "zoneinfo_dir:" <none>

      The absolute path to the zoneinfo directory, containing timezone
      definitions as generated by the vzic tool.  If not specified,
      whatever definitions libical finds will be used.

      If you are providing a Time Zone Data Distribution Service (i.e.
      you have "tzdist" listed in *httpmodules*), then this
      configuration option MUST be specified.

The TZDist module requires the "zoneinfo_dir" setting in imapd.conf(5)
to be set to the directory where your time zone data is stored.

The data is indexed by a database whose location is specified by the
"zoneinfo_db_path" option, using the format specified by the
"zoneinfo_db" option.


Administration
--------------

The TZDist module is designed to use the IANA Time Zone Database data
(a.k.a. Olson Database) converted to the iCalendar format.

vzic does convert the IANA TZ DB to iCalendar format.  For each time
zone it creates a separate file with its own TZID property. The TZID
property can have a vendor prefix, that is fixed when compiling vzic
by the "TZID_PREFIX" Makefile variable, which defaults to
*/citadel.org/%D_1/*.  Cyrus IMAP requires that the vendor prefix is
the empty string.

The cyrus-timezones package provides a vzic, which sets TZID_PREFIX to
the emtpy string.

The steps to populate the "zoneinfo_dir" directory are:

1. Acquire and build your choice of "vzic" tool.

2. Download the latest version of the Time Zone Database data from
   IANA. Note you only need the **data**, not the code.

3. Expand the downloaded time zone data into a temporary directory of
   your choice.

4. Copy leap-seconds.list from the temporary directory to
   "<zoneinfo_dir>".

5. Populate "zoneinfo_dir" with iCalendar data:

   *Initial Install Only*

   1. Convert the raw data into iCalendar format by running vzic as
      follows: "vzic --pure --olson-dir <location-of-raw-data>
      --output-dir <zoneinfo_dir>"

      This will create and install iCalendar data directly into the
      "<zoneinfo_dir>" directory.

   *Updating Data Only*

   2. Convert the raw data into iCalendar format by running vzic as
      follows: "vzic --pure --olson-dir <location-of-raw-data>"

      This will create a zoneinfo/ subdirectory in your current
      location

   3. Merge new/updated iCalendar data into the "<zoneinfo_dir>"
      directory by running vzic-merge.pl in your current location:
      "vzic-merge.pl"

6. Rebuild the Cyrus zoneinfo index by running ctl_zoneinfo(8) as
   follows: "ctl_zoneinfo -r <version-string>"

   where <version-string> contains description of the recently
   downloaded time zone data, colon, and the version of the data (e.g.
   "IANA Time Zone Database:2020a").

7. Check that the zoneinfo index database and all iCalendar data
   files/links are readable by the cyrus user.


iSchedule
=========


About iSchedule
---------------

Note:

  iSchedule support in Cyrus is a work in progress.

iSchedule allows CalDAV servers to:

* query an event participant's free/busy status prior to invitation in
  order to set up a good meeting time, which cannot be done over
  email.

* keep participant's local event current by updating the status of
  other participants automatically. This is not done when scheduling
  over email as it would result in too much mail traffic and extra
  manual overhead for the users.


caldav_allowscheduling
^^^^^^^^^^^^^^^^^^^^^^

   *This shows the default value: change it in imapd.conf to suit your
   needs.*

   "caldav_allowscheduling:" on

      Enable calendar scheduling operations. If set to "apple", the
      server will emulate Apple CalendarServer behavior as closely as
      possible. Allowed values: *off*, *on*, *apple*

iSchedule is automatically enabled in Cyrus if both the CalDAV module
and the "caldav_allowscheduling" options are enabled in a Cyrus
Murder. In this instance, Cyrus uses iSchedule to move scheduling
messages from frontend to backend servers.

Support for scheduling with external servers is currently under
development as there is the burden of authorization to verify the
authenticity and integrity of these messages to prevent inadvertent or
malicious data leaks or corruption.

What mechanism to use for authorization is under discussion with the
CalConnect standards body, whether this is DKIM or some other type of
message signature.
