File-based User Authentication | X-Pack for the Elastic Stack [5.3]

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File-based User Authenticationedit

You can manage and authenticate users with the built-in file internal realm. With the file realm users are defined in local files on each node in the cluster.

As the administrator of the cluster, it is your responsibility to ensure the same users are defined on every node in the cluster. X-Pack security does not deliver any mechanism to guarantee this.

The file realm is primarily supported to serve as a fallback/recovery realm. It is mostly useful in situations where all users locked themselves out of the system (no one remembers their username/password). In this type of scenarios, the file realm is your only way out - you can define a new admin user in the file realm and use it to log in and reset the credentials of all other users.

When you configure realms in elasticsearch.yml, only the realms you specify are used for authentication. To use the file realm as a fallback, you must include it in the realm chain.

To define users, X-Pack security provides the users command-line tool. This tool enables you to add and remove users, assign user roles and manage user passwords.

Configuring a File Realmedit

The file realm is added to the realm chain by default. You don’t need to explicitly configure a file realm to manage users with the users tool.

Like other realms, you can configure options for a file realm in the xpack.security.authc.realms namespace in elasticsearch.yml.

To configure an file realm:

Add a realm configuration of type file to elasticsearch.yml under the xpack.security.authc.realms namespace. At a minimum, you must set the realm type to file. If you are configuring multiple realms, you should also explicitly set the order attribute. See File Realm Settings for all of the options you can set for a file realm.

For example, the following snippet shows a file realm configuration that sets the order to zero so the realm is checked first:
```
xpack:
  security:
    authc:
      realms:
        file1:
          type: file
          order: 0
```
Restart Elasticsearch.

File Realm Settingsedit

Setting	Required	Description
`type`	yes	Indicates the realm type. Must be set to `file`.
`order`	no	Indicates the priority of this realm within the realm chain. Realms with a lower order are consulted first. Although not required, we recommend explicitly setting this value when you configure multiple realms. Defaults to `Integer.MAX_VALUE`.
`enabled`	no	Indicates whether this realm is enabled or disabled. Enables you to disable a realm without removing its configuration. Defaults to `true`.
`cache.ttl`	no	Specifies the time-to-live for cached user entries. A user’s credentials are cached for this period of time. Specify the time period using the standard Elasticsearch time units. Defaults to `20m`.
`cache.max_users`	no	Specifies the maximum number of user entries that can be stored in the cache at one time. Defaults to 100,000.
`cache.hash_algo`	no	Specifies the hashing algorithm that is used for the cached user credentials. See Cache hash algorithms for the possible values. (Expert Setting).

Managing Usersedit

The users command-line tool is located in ES_HOME/bin/x-pack and enables several administrative tasks for managing users:

Adding Usersedit

Use the useradd sub-command to add a user to your local node.

To ensure that Elasticsearch can read the user and role information at startup, run users useradd as the same user you use to run Elasticsearch. Running the command as root or some other user will update the permissions for the users and users_roles files and prevent Elasticsearch from accessing them.

bin/x-pack/users useradd <username>

A username must be at least 1 character and no longer than 30 characters. The first character must be a letter (a-z or A-Z) or an underscore (_). Subsequent characters can be letters, underscores (_), digits (0-9), or any of the following symbols @, -, . or $.

You can specify the user’s password at the command-line with the -p option. When this option is absent, the command prompts you for the password. Omit the -p option to keep plaintext passwords out of the terminal session’s command history.

bin/x-pack/users useradd <username> -p <secret>

Passwords must be at least 6 characters long.

You can define a user’s roles with the -r option. This option accepts a comma-separated list of role names to assign to the user.

bin/x-pack/users useradd <username> -r <comma-separated list of role names>

The following example adds a new user named jacknich to the file realm. The password for this user is theshining, and this user is associated with the network and monitoring roles.

bin/x-pack/users useradd jacknich -p theshining -r network,monitoring

For valid role names please see Role Definitions.

Listing Usersedit

Use the list sub-command to list the users registered with the file realm on the local node.

bin/x-pack/users list
rdeniro        : admin
alpacino       : power_user
jacknich       : monitoring,network

Users are in the left-hand column and their corresponding roles are listed in the right-hand column.

The list <username> sub-command lists a specific user. Use this command to verify that a user was successfully added to the local file realm.

bin/x-pack/users list jacknich
jacknich       : monitoring,network

Managing User Passwordsedit

Use the passwd sub-command to reset a user’s password. You can specify the new password directly with the -p option. When -p option is omitted, the tool will prompt you to enter and confirm a password in interactive mode.

bin/x-pack/users passwd <username>

bin/x-pack/users passwd <username> -p <password>

Assigning Users to Rolesedit

Use the roles sub-command to manage the roles of a particular user. The -a option adds a comma-separated list of roles to a user. The -r option removes a comma-separated list of roles from a user. You can combine adding and removing roles within the same command to change a user’s roles.

bin/x-pack/users roles <username> -a <commma-separate list of roles> -r <comma-separated list of roles>

The following command removes the network and monitoring roles from user jacknich and adds the user role:

bin/x-pack/users roles jacknich -r network,monitoring -a user

Listing the user displays the new role assignment:

bin/x-pack/users list jacknich
jacknich       : user

Deleting Usersedit

Use the userdel sub-command to delete a user.

bin/x-pack/users userdel <username>

A Look Under the Hoodedit

All the data about the users for the file realm is stored in two files, users and users_roles. Both files are located in CONFIG_DIR/x-pack/ and are read on startup.

By default, X-Pack security checks these files for changes every 5 seconds. You can change this default behavior by changing the resource.reload.interval.high setting in the elasticsearch.yml file (as this is a common setting in Elasticsearch, changing its value may effect other schedules in the system).

These files are managed locally by the node and are not managed globally by the cluster. This means that with a typical multi-node cluster, the exact same changes need to be applied on each and every node in the cluster.

A safer approach would be to apply the change on one of the nodes and have the users and users_roles files distributed/copied to all other nodes in the cluster (either manually or using a configuration management system such as Puppet or Chef).

While it is possible to modify these files directly using any standard text editor, we strongly recommend using the bin/x-pack/users command-line tool to apply the required changes.

The `users` Fileedit

The users file stores all the users and their passwords. Each line in the users file represents a single user entry consisting of the username and hashed password.

rdeniro:$2a$10$BBJ/ILiyJ1eBTYoRKxkqbuDEdYECplvxnqQ47uiowE7yGqvCEgj9W
alpacino:$2a$10$cNwHnElYiMYZ/T3K4PvzGeJ1KbpXZp2PfoQD.gfaVdImnHOwIuBKS
jacknich:$2a$10$GYUNWyABV/Ols/.bcwxuBuuaQzV6WIauW6RdboojxcixBq3LtI3ni

X-Pack security uses bcrypt to hash the user passwords.

The `users_roles` Fileedit

The users_roles file stores the roles associated with the users, as in the following example:

admin:rdeniro
power_user:alpacino,jacknich
user:jacknich

Each row maps a role to a comma-separated list of all the users that are associated with that role.