Prosody

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Prosody (pronunciation: 1, 2) is an XMPP server written in the Lua programming language. Prosody is designed to be lightweight and highly extensible. It is licensed under a permissive MIT license. Prosody is available for Arch Linux in the Community repository with some optional dependencies available from the AUR.

Previous experience with building and installing packages from the AUR and basic knowledge of XMPP will be very helpful when following the guide. As per usual, when command line commands are provided, lines preceded by $ indicate that the command may be run as a regular user, while lines preceded by # indicate that the command must be run as root.

Installation

Prosody is available in the Community repository, and is straightforward to install via pacman:

# pacman -S prosody

Optional Dependencies

Prosody has optional depedencies that although not strictly required for its operation, provide useful features. These dependencies may also have to be built and installed from the AUR. If you are unfamiliar with how to build and install packages from the AUR please see this tutorial.

TLS/SSL Support (Recommended)
Allow Prosody to encrypt streams to prevent eavesdropping.
Requires: lua51-sec (Community)
Better Connection Scaling (Recommended)
Allow Prosody to use libevent to handle a greater number of simultaneous connections.
Requires: lua51-eventAUR (AUR)
Stream Compression
Allow Prosody to compress client-to-server streams for compatible clients to save bandwidth.
Requires: lua51-zlib (Community)
Cyrus SASL Support
Allow Prosody to use the Cyrus SASL library to provide authentication.
Requires: lua-cyrussaslAUR (AUR)

Configuration

Note: The posix module and pidfile setting contained in the default configuration file are required for Prosody's proper operation on Arch Linux. Please do not disable or alter them.

The main configuration file is located at /etc/prosody/prosody.cfg.lua, information on how to configure Prosody can be found in Prosody's documentation. The syntax of the configuration file can be checked after any changes are made by running:

$ luac -p /etc/prosody/prosody.cfg.lua

No output means the syntax is correct.

Logging

The Arch Linux Prosody package is pre-configured to log to /var/log/prosody/prosody.err and /var/log/prosody/prosody.log. The Arch Linux package also includes a logrotate script in /etc/logrotate.d/prosody, configure it to suit your needs. If you enabled the olddir path for rotated log files in /etc/logrotate.conf you will likely want to move old prosody log files. First create the directory:

# mkdir /var/log/old/prosody

Then uncomment the olddir line in /etc/logrotate.d/prosody.

Operation

You can start Prosody through the included Systemd script:

# systemctl start prosody

To automatically start Prosody at boot execute:

# systemctl enable prosody

Prosody uses the default XMPP ports, 5222 and 5269, for client-to-server and server-to-server communications respectively. Configure your firewall as necessary.

You can manipulate Prosody users by using the prosodyctl program. To add a user:

# prosodyctl adduser <JID>

Tip: You will likely want to make at least one user an administrator by adding their Jabber ID to the admins list in the configuration file.

Issue man prosodyctl to see the man page for prosodyctl.

Security

User Registration

Prosody supports XMPP's in-band registration standard, which allows users to register with an XMPP client from within their client and change their passwords. While this is convenient for users it does not allow administrators to moderate the registration of new users. As such, the register module is enabled in the default configuration but allow_registration is set to false. This allows existing users to change their passwords from within their client but does not allow new users to register themselves.

Tip: If you do decide to support new in-band registrations, you will likely find the watchregistrations and welcome modules useful.

Stream Encryption

Prosody can utilize TLS certificates to encrypt client-to-server communications (if the proper dependencies are installed). See the relevant sections of prosody.cfg.lua to configure Prosody to utilize these certificates.

To require encryption for client-to-server communications add the following to your configuration file: 

/etc/prosody/prosody.cfg.lua
Host "*"

    c2s_require_encryption = true


Similarly, for server-to-server communications you may do: 

/etc/prosody/prosody.cfg.lua
Host "*"

    s2s_require_encryption = true

While requiring client-to-server encryption is generally a good idea, please keep in mind that some popular XMPP services such as Google Talk/Gmail do not support server-to-server encryption.

Listing Users

A simple way to see a list of the registered users is 

# ls -l /var/lib/prosody/*/accounts/*

alternatively, you can download the module mod_listusers.lua, and use it as 

# prosodyctl mod_listusers

Removal

Prosody and all its (required) dependencies can be removed using pacman:

# pacman -Rs prosody

Check above for optional dependencies that may also be removed.

Prosody may leave the following directories on your filesystem that you may want to remove if you do not plan on reinstalling Prosody: /etc/prosody, /var/lib/prosody, /var/log/prosody, and /var/log/old/prosody.

Tips & Tricks

Components

Prosody supports XMPP components, which provide extra services to clients. Components are either provided internally by special Prosody modules or externally using the protocol specified in XEP-0114.

Note: Components must use a different hostname from the VirtualHosts defined in prosody.cfg.lua. Attempting to host a component on the same hostname as a defined VirtualHost will result in errors.

By default, Prosody will listen for external components. If you do not plan to use any external components with Prosody you can disable this behavior by adding the following your configuration: 

/etc/prosody/prosody.cfg.lua
component_ports = {}

Multi-User Chat

A common component used with XMPP servers is Multi-User Chat (MUC), which allows conferences between multiple users. MUC is provided as an internal component with Prosody. To enable MUC add the following to your configuration file: 

/etc/prosody/prosody.cfg.lua
Component "conference.example.com" "muc"

This will enable the MUC component on host conference.example.com.

Prosody Modules

Prosody Modules is a collection of extra modules not distributed with Prosody. These modules are in various states of development from highly experimental to relatively stable. You should consult a given module's wiki page for more information. An example of an extra module is pastebin, which when loaded will intercept long messages (for example, log file output) and replace them with a link to a pastebin hosted using Prosody's internal HTTP server (provided by the core module, httpserver).

To use an extra module download its raw file(s) from the source browser (when viewing a file, search for the link "View raw file"). Alternatively and likely easier, use Mercurial to clone the entire repository:

$ hg clone https://prosody-modules.googlecode.com/hg/ prosody-modules

Now you can copy the module (and any additional files it needs) to Prosody's module directory at /usr/lib/prosody/modules. To enable the module add it to your modules_enabled list in your prosody.cfg.lua for the host or component you wish to use it for. For example, to use the pastebin module on a MUC component: 

/etc/prosody/prosody.cfg.lua
Component "conference.example.com" "muc"
    modules_enabled = { "pastebin" }
Note: An enforced Prosody convention is that modules are named mod_foo.lua but simply enabled by adding foo to the modules_enabled list.

Console

Warning: The console does not require any authentication so any user on a multi-user system can connect and issue commands on the console. Therefore it is not recommended to enable the console module on a multi-user system.

The console module provides a telnet console from which administrative operations and queries can be performed. You can connect to the console by issuing:

$ telnet localhost 5582

You of course need the telnet program provided by the inetutils package. Use the help command in the console to get usage help.

The console even allows you to execute Lua commands directly on the server by preceding a command with >. For example to see if a client connection is compressed:

> full_sessions["romeo@montague.lit/Resource"].compressed

Will return true if the connection is compressed or nil if it is not.

Troubleshooting

One of Prosody's primary design principles is to be simple to use and configure. However, issues can still arise (and likely will as is the case with any complex software). If you encounter a problem there are a variety of steps you can take to narrow down the cause:

  • Check for known issues
    Look at the release notes for your Prosody version to see if your issue is listed as a known issue. Also check the issue tracker to see if your issue has already been reported.
  • Check configuration syntax
    Run luac -p /etc/prosody/prosody.cfg.lua to check for any syntax errors in your configuration file. If there is no output your syntax is fine.
  • Check the log files
    Log files are located in /var/log/prosody. Errors are only logged if there is a critical problem so always address those issues. If you think you have a very low level issue (like protocol compatibility between clients and servers with Prosody) then you can enable the very verbose debug level logging. The default configuration file has commented out lines to log debug messages to prosody.debug.
  • Check permissions
    The Prosody package should add a new prosody user and group to your system and set appropriate permissions, but it is always good to double check. Ensure that /etc/prosody and /var/lib/prosody are owned by the prosody user and that the user has appropriate permissions to read and write to those paths and all contained files.
  • Check listening ports
    When troubleshooting connection issues make sure that Prosody is actually listening for connections. You may do so by running ss -tul and making sure that xmpp-client (port 5222) and xmpp-server (port 5269) are listed.
  • Restart
    Like most things, it doesn't hurt to restart Prosody (/etc/rc.d/prosody restart) to see if it resolves an issue.

If you're unable to resolve your issue yourself there are a variety of resources you can use to seek help. In order of immediacy with which you'll likely receive help:

  1. XMPP Conference: prosody@conference.prosody.im
  2. Mailing List: Web Interface, Email
  3. Arch Forums (for package issues)

Development

Change Log

You may view the change log of the Prosody package by issuing the following command:

$ pacman -Qc prosody

Packages

Two development packages are maintained for Prosody in the AUR, prosody-develAUR and prosody-hg]AUR. prosody-devel tracks the latest source release of a development version (alpha, beta, release candidate) and will actually be behind the stable version if a final version of the development version is released. prosody-hg tracks the Mercurial repository tip for Prosody and will always contain the latest code as it is checked in. Both packages are built similarly to the stable package.

More Resources

Development

Documentation

Communication

Social

See also

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