---
labels:
- 'Stage-Alpha'
- 'Type-Auth'
summary: 'Authentication via external script/process'
...

Introduction
============

Allow client authentication to be handled by an external script/process.

Installation
============

mod\_auth\_external depends on a Lua module called
[lpty](http://www.tset.de/lpty/). You can install it on many platforms
using [LuaRocks](http://luarocks.org/), for example:

    sudo luarocks install lpty

Note: Earlier versions of the module did not depend on lpty. While using
the newer version is strongly recommended, you can find the [older
version
here](https://prosody-modules.googlecode.com/hg-history/50ee38e95e754bf1034d980364f93564028b2f34/mod_auth_external/mod_auth_external.lua)
if you need it (revision 50ee38e95e75 of the repository).

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

As with all auth modules, there is no need to add this to
modules\_enabled. Simply add in the global section, or for the relevant
hosts:

    authentication = "external"

These options are specific to mod\_auth\_external:

  -------------------------- -------------------------------------------------------------------------------------------------------------------------
  external\_auth\_protocol   May be "generic" or "ejabberd" (the latter for compatibility with ejabberd external auth scripts. Default is "generic".
  external\_auth\_command    The command/script to execute.
  -------------------------- -------------------------------------------------------------------------------------------------------------------------

Two other options are also available, depending on whether the module is
running in 'blocking' or 'non-blocking' mode:

  --------------------------- -------------- ------------------------------------------------------------------------------------------------------------------
  external\_auth\_timeout     blocking       The number of seconds to wait for a response from the auth process. Default is 5.
  external\_auth\_processes   non-blocking   The number of concurrent processes to spawn. Default is 1, increase to handle high connection rates efficiently.
  --------------------------- -------------- ------------------------------------------------------------------------------------------------------------------

Blocking vs non-blocking
------------------------

Non-blocking mode is automatically activated when:

-   Running Prosody trunk ([nightly](http://prosody.im/nightly/) build
    414+).
-   [libevent](http://prosody.im/doc/libevent) is enabled in the config,
    and LuaEvent is available.
-   lpty (see installation above) is version 1.0.1 or later.

Protocol
========

Prosody executes the given command/script, and sends it queries.

Your auth script should simply read a line from standard input, and
write the result to standard output. It must do this in a loop, until
there's nothing left to read. Prosody can keep sending more lines to the
script, with a command on each line.

Each command is one line, and the response is expected to be a single
line containing "0" for failure or "1" for success. Your script must
respond with "0" for anything it doesn't understand.

There are three commands used at the moment:

auth
----

Check if a user's password is valid.

Example: `auth:username:example.com:abc123`

Note: The password can contain colons. Make sure to handle that.

isuser
------

Check if a user exists.

Example: `isuser:username:example.com`

setpass
-------

Set a new password for the user. Implementing this is optional.

Example: `setpass:username:example.com:abc123`

Note: The password can contain colons. Make sure to handle that.

ejabberd compatibilty
---------------------

ejabberd implements a similar protocol. The main difference is that
Prosody's protocol is line-based, while ejabberd's is length-prefixed.

Add this to your config if you need to use an ejabberd auth script:

        external_auth_protocol = "ejabberd"

Compatibility
=============

  ----- -------
  0.8   Works
  0.9   Works
  ----- -------
