Abstraction of various SASL mechanism responses.

v1.4.0 2024-04-02 10:30 UTC


The PHP SASL Authentification Library.

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Provides code to generate responses to common SASL mechanisms, including:

  • Digest-MD5
  • Cram-MD5
  • Plain
  • Anonymous
  • Login (Pseudo mechanism)

Full refactored version of the the original Auth_SASL2 Pear package.


The easiest way to install fabiang/sasl is by using Composer:

curl -sS https://getcomposer.org/installer | php
composer require fabiang/sasl


Use the factory method to create a authentication mechanism object:

use Fabiang\Sasl\Sasl;

$factory = new Sasl;

$mechanism = $factory->factory('SCRAM-SHA-1', array(
    'authcid'  => 'username',
    'secret'   => 'password',
    'authzid'  => 'authzid', // optional. Username to proxy as
    'service'  => 'servicename', // optional. Name of the service
    'hostname' => 'hostname', // optional. Hostname of the service

$response = $mechanism->createResponse();

Challenge-based authentication mechanisms implement the interface Fabiang\Sasl\Authentication\ChallengeAuthenticationInterface. For those mechanisms call the method again with the challenge:

$response = $mechanism->createResponse($challenge);

Note: The challenge must be Base64 decoded.

SCRAM verification

To verify the data returned by the server for SCRAM you can call:


If the method returns false you should disconnect.

SCRAM downgrade protection

To enable downgrade protection for SCRAM, you'll need to pass the allowed authentication mechanisms and channel-binding types via options to the factory:

Note: Channel-binding is currently not supported due to limitations of PHP.

$mechanism = $factory->factory('SCRAM-SHA-1', array(
    'authcid'  => 'username',
    'secret'   => 'password',
    'authzid'  => 'authzid', // optional. Username to proxy as
    'service'  => 'servicename', // optional. Name of the service
    'hostname' => 'hostname', // optional. Hostname of the service
    'downgrade_protection' => array( // optional. When `null` downgrade protection string from server won't be validated
        'allowed_mechanisms'       => array('SCRAM-SHA-1-PLUS', 'SCRAM-SHA-1'), // allowed mechanisms by the server
        'allowed_channel_bindings' => array('tls-unique', 'tls-exporter', 'tls-server-end-point'), // allowed channel-binding types by the server

Required options

List of options required by authentication mechanisms. For mechanisms that are challenge-based you'll need to call createResponse() again and send the returned value to the server.

Mechanism Authcid Secret Authzid Service Hostname Challenge
Anonymous yes no no no no no
Cram-MD5 yes yes no no no yes
Digest-MD5 yes yes optional yes yes yes
External no no yes no no no
Login yes yes no no no no
Plain yes yes optional no no no
SCRAM-* yes yes optional no no yes

Unit tests

If you like this library and you want to contribute, make sure the unit tests and integration tests are running.

Run the unit tests:


Integration tests

The integration tests verify the authentication methods against an Ejabberd and Dovecot server.

To launch the servers you can use the provided Docker Compose file. Just install Docker and run:

docker compose up -d

Note: ejabberd takes up to twenty minutes to start.

Now you can run the integration tests:



BSD-3-Clause. See the LICENSE.md.