It is important to configure authentication on your Mosquitto instance, so unauthorised clients cannot connect. In Mosquitto 2.0 and up, you must choose your authentication options explicitly before clients can connect. In earlier versions the default is to allow clients to connect without authentication. There are three choices for authentication: password files, authentication plugins, and unauthorised/anonymous access. It is possible to use a combination of all three choices. It is possible to have different listeners use different authentication methods by setting `per_listener_settings true` in your configuration file. As well as authentication you should also consider some form of access control to determine what clients can access which topics. ## Password files Password files are a simple mechanism of storing usernames and passwords in a single file. They are good if you have a relatively small number of fairly static users. If you make changes to the password file you must trigger the broker to reload the file by sending a SIGHUP message: ``` kill -HUP ``` ### Creating a password file To create a password file, use the `mosquitto_passwd` utility, use the line below. You will be asked for the password. Note that `-c` means an existing file will be overwritten: ``` mosquitto_passwd -c ``` To add more users to an existing password file, or to change the password for an existing user, leave out the `-c` argument: ``` mosquitto_passwd ``` To remove a user from a password file: ``` mosquitto_passwd -D ``` You can also add/update a username and password in a single line, but be aware that this means the password is visible on the command line and in any command history: ``` mosquitto_passwd ``` ### Configuring the broker To start using your password file you must add the `password_file` option to your configuration file: ``` password_file ``` The password file must be able to be read by whatever user Mosquitto is running as. On Linux/POSIX systems this will typically be the `mosquitto` user, and `/etc/mosquitto/password_file` is a good place for the file itself. If you are using the `per_listener_settings true` option to have separate security settings per listener, you must place the password file option *after* the listener it is for: ``` listener 1883 password_file /etc/mosquitto/password_file ``` ## Authentication plugins If you want more control over authentication of your users than is offered by a password file, then an authentication plugin may be suitable for you. The features offered depend on which plugin you use. ### Configuring the plugin Configuring a plugin varies depending on the version of Mosquitto plugin interface the plugin was written for, either version 2.0 and up, or 1.6.x and earlier. For 1.6.x and below, use the `auth_plugin` option. These plugins are also supported by version 2.0: ``` listener 1883 auth_plugin ``` Some plugins require extra configuration which will be described in their documentation. For 2.0 and up, use the `plugin` option: ``` listener 1883 plugin ``` ### Available plugins * [Dynamic security](https://mosquitto.org/documentation/dynamic-security/), for 2.0 and up only, provided by the Mosquitto project to give flexible in-broker clients, groups, and roles that can be administered remotely. * [mosquitto-go-auth](https://github.com/iegomez/mosquitto-go-auth), which offers the use of a variety of backends to store user data, such as mysql, jwt, or redis. ## Unauthenticated access To configure unauthenticated access, use the `allow_anonymous` option: ``` listener 1883 allow_anonymous true ``` It is valid to allow anonmous and authenticated access on the same broker. In particular the dynamic security plugin allows you to assign different rights to anonymous users than to authenticated users, which may be useful for read-only access to data for example.