*******************
Modern XMPP Server
*******************
This is what I did to configure my XMPP server, using only `packages
supported in Debian `_ and 100%
compliant with the `tests for XEP-0459: XMPP Compliance Suites 2022 on
conversations' website `_.
This guide was written for prosody 0.9 under Debian jessie, but is being
kept up to date as I upgrade my server to new Debian releases.
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How
===
I've decided to install prosody_, mostly because it was recommended by
the `RTC QuickStart Guide`_; I've heard that similar results can be
reached with ejabberd_ and other servers.
.. _prosody: https://prosody.im/
.. _`RTC QuickStart Guide`: http://rtcquickstart.org/
.. _ejabberd: https://www.ejabberd.im/
I'm also targetting Debian_ stable (+ backports_); currently that's
bullseye and prosody 0.11 (upgrade to bookworm is planned soon).
.. _Debian: https://www.debian.org
.. _backports: https://backports.debian.org/
Installation and prerequisites
------------------------------
You will need to install the packages ``prosody`` and
``prosody-modules``; on jessie the versions in backports were needed,
but currently not on buster.
You also need to setup some TLS certificates (I used `Let's Encrypt`_);
and make them readable by the ``prosody`` user; you can see `Chapter 12
of the RTC QuickStart Guide
`_ for
more details.
With prosody 0.10+ you will also need to configure the location of the
certificate for https with a configuration stanza such as::
https_ssl = {
certificate = "/etc/ssl/public/example.org.pem";
key = "/etc/ssl/private/example.org-key.pem";
}
or see the `prosody documentation on certificates
`_ to see where to put certificates
so that prosody is able to autodetect them.
.. _`Let's Encrypt`: https://letsencrypt.org/
On your firewall, you'll need to open the following TCP ports:
* 5222 (client2server)
* 5269 (server2server)
* 5280 (default http port for prosody)
* 5281 (default https port for prosody)
The latter two are needed to enable some services provided via http(s),
including rich media transfers.
With just a handful of users, I didn't bother to configure LDAP or
anything else, but just created users manually via::
prosodyctl adduser alice@example.org
In-band registration is disabled by default (and I've left it that way,
to prevent my server from being used to send spim_).
.. _spim: https://en.wikipedia.org/wiki/Messaging_spam
prosody configuration
---------------------
You can then start configuring prosody by editing
``/etc/prosody/prosody.cfg.lua`` and changing a few values from the
distribution defaults.
First of all, enforce the use of encryption and certificate checking
both for client2server and server2server communications with::
c2s_require_encryption = true
s2s_secure_auth = true
and then, if you need to, add to the whitelist any server that you want
to talk to and doesn't support secure s2s communication (but note that
gmail.com is no longer needed, as it doesn't support xmpp any longer)::
s2s_insecure_domains = { "gmail.com" }
virtualhosts
------------
For each virtualhost you want to configure, create a file
``/etc/prosody/conf.avail/chat.example.org.cfg.lua`` with contents like
the following::
VirtualHost "chat.example.org"
enabled = true
ssl = {
key = "/etc/ssl/private/example.org-key.pem";
certificate = "/etc/ssl/public/example.org.pem";
}
For the domains where you also want to enable MUCs, add the follwing
lines::
Component "conference.chat.example.org" "muc"
restrict_room_creation = "local"
modules_enabled = {
"mam_muc",
"vcard_muc",
}
the ``"local"`` configures prosody so that only local users are allowed
to create new rooms (but then everybody can join them, if the room
administrator allows it): this may help reduce unwanted usages of your
server by random people.
Enabling the ``mam_muc`` module (on prosody 0.10 only) allows people to
syncronize message history between multiple clients (XEP-0313)
You can also add the following line to enable rich media transfers via
http uploads (XEP-0363_)::
Component "upload.chat.example.org" "http_upload"
The defaults are pretty sane, but see
https://modules.prosody.im/mod_http_upload.html for details on what
knobs you can configure for this module; you may want e.g. to change the
maximum file size limit and setup an expiry date::
Component "upload.chat.example.org" "http_upload"
http_upload_file_size_limit = 1024 * 1024 * 2
http_upload_expire_after = 60 * 60 * 24 * 7
.. _XEP-0363: https://xmpp.org/extensions/xep-0363.html
Don't forget to enable the virtualhost by linking the file inside
``/etc/prosody/conf.d/``.
additional modules
------------------
Most of the other interesting XEPs are enabled by loading additional
modules inside ``/etc/prosody/prosody.cfg.lua`` (under
``modules_enabled``); to enable ``mod_something`` just add a line like::
"something";
Most of these come from the ``prosody-modules`` package (and thus from
https://modules.prosody.im/ ) and some may require changing when prosody
0.10 will be available; when this is the case it is mentioned below.
``mod_blocklist`` (XEP-0191)
To allow user-controlled blocking of users, including as an anti-spim
measure.
``mod_smacks`` (XEP-0198)
Allow clients to resume a disconnected session before a customizable
timeout and prevent message loss.
``mod_mam`` (XEP-0313)
Archive messages on the server for a limited period of time (default
1 week) and allow clients to retrieve them; this is required to
syncronize message history between multiple clients.
With prosody 0.9 only an in-memory storage backend is available,
which may make this module problematic on servers with many users.
prosody 0.10 will fix this by adding support for an SQL backed
storage with archiving capabilities.
``mod_throttle_presence`` + ``mod_filter_chatstates`` (XEP-0352)
Filter out presence updates and chat states when the client announces
(via Client State Indication) that the user isn't looking.
This is useful to reduce power and bandwidth usage for "useless"
traffic.
``cloud_notify`` (XEP-0357)
Allow clients to register an “app server” that is notified about new
messages
See also
========
* `The State of Mobile XMPP in 2016 `_
(blog post by the maintainer of Conversations)
* `Prosody installation instructions in the FreedomBox wiki
`_
(for basic prosody configuration)
* `What Prosody modules do I need to support Conversations?
`_
(on Server Fault)
* `This HOWTO on my old website
`_
* `Enrico's post on how we configured the server before compliance.conversations.im was a thing `_
..
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