Defining a user for Sabre Dav (calendar)

Sabre is an open-source calendar server. It is well written and moderately powerful, being used by Nextcloud open-source groupware. However, setting up a Sabre calendar server is not that easy. As the documentation says, there is no web interface for creating users. Instead, it advises that you create them directly in the database. According to the instructions you need to:

1. Add an entry to the users table, specifying the user name and the digest of the password (it is pretty unclear what to do for this)
2. Add a corresponding entry to the principals table -- but no details are given

Looking at the two tables in question, users has three columns: id, username and digesta1. The first is the primary key and doesn't need to be set. The second and third columns are varbinary. that is, you specify them as hexidecimal strings preceded by '0x' and they will be defined and displayed in that form.

The principals table has id, uri, email and displayname columns. displayname is text, uri and email are varbinary. It is pretty simple if you know SQL to add entries to the princpals table. I'll concentrate on the format of the digesta1. According to the php source code it is an md5 hash of a string of the format:

username:realm:password

There is one user already defined: admin user. It is unclear what the realm is set to. Stepping through the debugger I discovered that it is set by default to SabreDAV. I tried creating the hash using md5sum on the commandline, but this didn't give the correct answer. You need to create it using the php function md5. Once I generated it that way, and plugged in the value to the digesta1 column of the users table I could login using my own password.

Stick a file with this content on your web-server and it will print out the digesta1 field value for the user username with password foobar:

<?php
echo('hash='.md5('username:SabreDAV:foobar'));
?>