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# Cyrus IMAP

# CalDAV

## Configuration

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.

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 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.

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.

Mapping of IMAP Rights to WebDAV Privileges & HTTP Methods
IMAP rights | WebDAV privileges | HTTP methods
--- | --- | ---
l - lookup r - read | DAV:read | DAV:read-current-user-privilege-set CALDAV:read-free-busy | GET/HEAD COPY/MOVE (on source) PROPFIND REPORT
s - seen |  |
w - write n - write shared annotation | DAV:write-properties | PROPPATCH COPY/MOVE (on destination)
i - insert | DAV:write-content | PUT PATCH COPY/MOVE (on destination resource) LOCK UNLOCK (lock owner ONLY)
p - post | DAV:bind | CYRUS:add-resource | POST
k - create mailbox | CYRUS:make-collection | MKCOL MKCALENDAR COPY/MOVE (on destination collection)
x - delete mailbox | DAV:unbind | CYRUS:remove-collection | DELETE (collection) MOVE (on source collection)
t - delete message e - expunge | CYRUS:remove-resource | DELETE (resource) MOVE (on source resource)
a - admin | CYRUS:admin | DAV:read-acl DAV:write-acl DAV:share DAV:unlock | ACL PROPFIND (DAV:acl property ONLY) UNLOCK (ANY lock)
Regular Calendar Collections ONLY — read freebusy time?
9 - freebusy | CALDAV:read-free-busy | REPORT (CALDAV:free-busy-query ONLY) GET/HEAD (Freebusy URLs ONLY)
Scheduling Outbox ONLY — implicitly create/send iTIP message?
9 - freebusy | CALDAV:schedule-send | CALDAV:schedule-send-freebusy | POST (by organizer on scheduling Outbox)
8 - invite | CALDAV:schedule-send-invite | PUT/PATCH/DELETE (by organizer on calendar resource/collection)
7 - reply | CALDAV:schedule-send-reply | PUT/PATCH/DELETE (by attendee on calendar resource/collection)
Scheduling Inbox ONLY — implicitly deliver/process incoming iTIP message?
9 - freebusy | CALDAV:schedule-deliver | CALDAV:schedule-query-freebusy |
8 - invite | CALDAV:schedule-deliver-invite
7 - reply | CALDAV:schedule-deliver-reply

Default WebDAV Privileges by Collection
Collection | User ID | WebDAV Privileges | IMAP rights
--- | --- | --- | ---
Regular Calendar Collection | owner | DAV:all + CALDAV:read-free-busy | lrwipkxtan9
anyone | CALDAV:read-free-busy | 9
Managed Attachments Collection | owner | DAV:all | lrwipkxtan
anyone | DAV:read | lr
Scheduling Inbox | owner | DAV:all + CALDAV:schedule-deliver | lrwipkxtan789
anyone | CALDAV:schedule-deliver | 789
Scheduling Outbox | owner | DAV:all + CALDAV:schedule-send | lrwipkxtan789

## 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 is also required if you want the CalDAV server to strip known VTIMEZONEs from incoming iCalendar data (as advertised by the `calendar-no-timezone` DAV option from RFC 7809).

### Configuration

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.

We provide a modified vzic to convert IANA formatted data into iCalendar format, in the cyrus-timezones package to make the following steps easier.

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. 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`

5. 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”).

6. 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.

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.