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# Authentication

## Supported Methods

The authentication methods supported by ejabberd are:

- `internal` — See section Internal.

- `external` — See section External Script.

- `ldap` — See section LDAP.

- `sql` — See section Relational Databases.

- `anonymous` — See section Anonymous Login and SASL Anonymous.

- `pam` — See section PAM Authentication.

- `jwt` — See section JWT Authentication.

The top-level option auth_method defines the authentication methods that are used for user authentication. The option syntax is:

    auth_method: [Method1, Method2, ...]

When the `auth_method` option is omitted, ejabberd relies on the default database which is configured in `default_db` option. If this option is not set neither, then the default authentication method will be `internal`.

Account creation is only supported by `internal`, `external` and `sql` auth methods.

## General Options

The top-level option auth_password_format allows to store the passwords in SCRAM format, see the SCRAM section.

Other top-level options that are relevant to the authentication configuration: disable_sasl_mechanisms, fqdn.

Authentication caching is enabled by default, and can be disabled in a specific vhost with the option auth_use_cache. The global authentication cache can be configured for all the authentication methods with the global top-level options: auth_cache_missed, auth_cache_size, auth_cache_life_time. For example:

    auth_cache_size: 1500
    auth_cache_life_time: 10 minutes

    host_config:
      example.org:
        auth_method: [internal]
      example.net:
        auth_method: [ldap]
        auth_use_cache: false

## Internal

ejabberd uses its internal Mnesia database as the default authentication method. The value `internal` will enable the internal authentication method.

To store the passwords in SCRAM format instead of plaintext, see the SCRAM section.

Examples:

- To use internal authentication on `example.org` and LDAP authentication on `example.net`:

      host_config:
        example.org:
          auth_method: [internal]
        example.net:
          auth_method: [ldap]

- To use internal authentication with hashed passwords on all virtual hosts:

      auth_method: internal
      auth_password_format: scram

## External Script

In the `external` authentication method, ejabberd uses a custom script to perform authentication tasks. The server administrator can write that external authentication script in any programming language.

Please check some example scripts, and the details on the interface between ejabberd and the script in the Developers > Internals > External Authentication section.

Options:

- extauth_pool_name
- extauth_pool_size
- extauth_program

Please note that caching interferes with the ability to maintain multiple passwords per account. So if your authentication mechanism supports application-specific passwords, caching must be disabled in the host that uses this authentication method with the option auth_use_cache.

This example sets external authentication, specifies the extauth script, disables caching, and starts three instances of the script for each virtual host defined in ejabberd:

    auth_method: [external]
    extauth_program: /etc/ejabberd/JabberAuth.class.php
    extauth_pool_size: 3
    auth_use_cache: false

## Anonymous Login and SASL Anonymous

The `anonymous` authentication method enables two modes for anonymous authentication:

`Anonymous login`: This is a standard login, that use the classical login and password mechanisms, but where password is accepted or preconfigured for all anonymous users. This login is compliant with SASL authentication, password and digest non-SASL authentication, so this option will work with almost all XMPP clients

`SASL Anonymous`: This is a special SASL authentication mechanism that allows to login without providing username or password (see `XEP-0175`). The main advantage of SASL Anonymous is that the protocol was designed to give the user a login. This is useful to avoid in some case, where the server has many users already logged or registered and when it is hard to find a free username. The main disadvantage is that you need a client that specifically supports the SASL Anonymous protocol.

The anonymous authentication method can be configured with the following options. Remember that you can use the host_config option to set virtual host specific options (see section Virtual Hosting):

- allow_multiple_connections
- anonymous_protocol

Examples:

- To enable anonymous login on all virtual hosts:

      auth_method: [anonymous]
      anonymous_protocol: login_anon

- Similar as previous example, but limited to `public.example.org`:

      host_config:
        public.example.org:
          auth_method: [anonymous]
          anonymous_protoco: login_anon

- To enable anonymous login and internal authentication on a virtual host:

      host_config:
        public.example.org:
          auth_method:
            - internal
            - anonymous
          anonymous_protocol: login_anon

- To enable SASL Anonymous on a virtual host:

      host_config:
        public.example.org:
          auth_method: [anonymous]
          anonymous_protocol: sasl_anon

- To enable SASL Anonymous and anonymous login on a virtual host:

      host_config:
        public.example.org:
          auth_method: [anonymous]
          anonymous_protocol: both

- To enable SASL Anonymous, anonymous login, and internal authentication on a virtual host:

      host_config:
        public.example.org:
          auth_method:
            - internal
            - anonymous
          anonymous_protocol: both

There are more configuration examples and XMPP client example stanzas in `Anonymous users support`.

## PAM Authentication

ejabberd supports authentication via Pluggable Authentication Modules (PAM). PAM is currently supported in AIX, FreeBSD, HP-UX, Linux, Mac OS X, NetBSD and Solaris.

If compiling ejabberd from source code, PAM support is disabled by default, so you have to enable PAM support when configuring the ejabberd compilation: `./configure --enable-pam`

Options:

- pam_service
- pam_userinfotype

Example:

    auth_method: [pam]
    pam_service: ejabberd

Though it is quite easy to set up PAM support in ejabberd, there are several problems that you may need to solve:

- To perform PAM authentication, ejabberd uses external C-program called `epam`. By default, it is located in `/var/lib/ejabberd/priv/bin/` directory. You have to set it root on execution in the case when your PAM module requires root privileges (`pam_unix.so` for example). Also you have to grant access for ejabberd to this file and remove all other permissions from it. Execute with root privileges:

      chown root:ejabberd /var/lib/ejabberd/priv/bin/epam
      chmod 4750 /var/lib/ejabberd/priv/bin/epam

- Make sure you have the latest version of PAM installed on your system. Some old versions of PAM modules cause memory leaks. If you are not able to use the latest version, you can `kill(1)` `epam` process periodically to reduce its memory consumption: ejabberd will restart this process immediately.

- ejabberd binary installers include `epam` pointing to module paths that may not work in your system. If authentication doesn't work correctly, check if syslog (example: `journalctl -t epam -f`) reports errors like `PAM unable to dlopen(/home/runner/... No such file or directory`. In that case, create a PAM configuration file (example: `/etc/pam.d/ejabberd`) and provide the real path to that file in your machine:

      #%PAM-1.0
      auth        sufficient  /usr/lib/x86_64-linux-gnu/security/pam_unix.so audit
      account     sufficient  /usr/lib/x86_64-linux-gnu/security/pam_unix.so audit

- `epam` program tries to turn off delays on authentication failures. However, some PAM modules ignore this behavior and rely on their own configuration options. You can create a configuration file (in Debian it would be `/etc/pam.d/ejabberd`). This example shows how to turn off delays in `pam_unix.so` module:

      #%PAM-1.0
      auth        sufficient  pam_unix.so likeauth nullok nodelay
      account     sufficient  pam_unix.so

  That is not a ready to use configuration file: you must use it as a hint when building your own PAM configuration instead. Note that if you want to disable delays on authentication failures in the PAM configuration file, you have to restrict access to this file, so a malicious user can’t use your configuration to perform brute-force attacks.

- You may want to allow login access only for certain users. `pam_listfile.so` module provides such functionality.

- If you use `pam_winbind` to authorize against a Windows Active Directory, then `/etc/nsswitch.conf` must be configured to use `winbind` as well.

## JWT Authentication

ejabberd supports authentication using JSON Web Token (JWT). When enabled, clients send signed tokens instead of passwords, which are checked using a private key specified in the jwt_key option. JWT payload must look like this:

    {
      "jid": "test@example.org",
      "exp": 1564436511
    }

Options:

- jwt_key
- jwt_auth_only_rule
- jwt_jid_field

Example:

    auth_method: jwt
    jwt_key: /path/to/jwt/key

In this example, admins can use both JWT and plain passwords, while the rest of users can use only JWT.

    # the order is important here, don't use [sql, jwt]
    auth_method: [jwt, sql]

    access_rules:
      jwt_only:
        deny: admin
        allow: all

    jwt_auth_only_rule: jwt_only

Please notice that, when using JWT authentication, mod_offline will not work. With JWT authentication the accounts do not exist in the database, and there is no way to know if a given account exists or not.

For more information about JWT authentication, you can check a brief tutorial in the ejabberd 19.08 release notes.

## SCRAM

The top-level option `auth_password_format` defines in what format the users passwords are stored: SCRAM format or plaintext format.

The top-level option `auth_scram_hash` defines the hash algorithm that will be used to scram the password.

ejabberd supports channel binding to the external channel, allowing the clients to use `-PLUS` authentication mechanisms.

In summary, depending on the configured options, ejabberd supports:

- `SCRAM_SHA-1(-PLUS)`
- `SCRAM_SHA-256(-PLUS)`
- `SCRAM_SHA-512(-PLUS)`

For details about the client-server communication when using SCRAM, refer to SASL Authentication and SCRAM.

### Internal storage

When ejabberd starts with internal auth method and SCRAM password format configured:

    auth_method: internal
    auth_password_format: scram

and detects that there are plaintext passwords stored, they are automatically converted to SCRAM format:

    [info] Passwords in Mnesia table 'passwd' will be SCRAM'ed
    [info] Transforming table 'passwd', this may take a while

### SQL Database

Please note that if you use SQL auth method and SCRAM password format, the plaintext passwords already stored in the database are not automatically converted to SCRAM format.

To convert plaintext passwords to SCRAM format in your database, use the convert_to_scram command:

    ejabberdctl convert_to_scram example.org

### Foreign authentication

Note on SCRAM using and foreign authentication limitations: when using the SCRAM password format, it is not possible to use foreign authentication method in ejabberd, as the real password is not known.

Foreign authentication are use to authenticate through various bridges ejabberd provide. Foreign authentication includes at the moment SIP and TURN auth support and they will not be working with SCRAM.