Managing Users in an esusers Realm

The esusers command line tool is located in ES_HOME/bin/shield and enables several administrative tasks for managing users:

Adding Users

The esusers useradd command adds a user to your cluster.

Note

To ensure that Elasticsearch can read the user and role information at startup, run esusers 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.

esusers 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 esusers command prompts you for the password. Omit the -p option to keep plaintext passwords out of the terminal session’s command history.

esusers useradd <username> -p <secret>

Passwords must be at least 6 characters long.

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

esusers useradd <username> -r <comma-separated list of role names>

The following example adds a new user named jacknich to the esusers realm. The password for this user is theshining, and this user is associated with the logstash and marvel roles.

esusers useradd jacknich -p theshining -r logstash,marvel

For valid role names please see Role Definitions.

Listing Users

The esusers list command lists the users registered in the esusers realm, as in the following example:

esusers list
rdeniro        : admin
alpacino       : power_user
jacknich       : marvel,logstash

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

The esusers list <username> command lists a specific user. Use this command to verify that a user has been successfully added to the cluster.

esusers list jacknich
jacknich       : marvel,logstash

Managing User Passwords

The esusers passwd command enables you 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.

esusers passwd <username>
esusers passwd <username> -p <password>

Assigning Users to Roles

The esusers roles command manages the roles associated to 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.

esusers roles <username> -a <commma-separate list of roles> -r <commma-separate list of roles>

The following command removes the logstash and marvel roles from user jacknich, as well as adding the user role:

esusers roles jacknich -r logstash,marvel -a user

Listing the user displays the new role assignment:

esusers list jacknich
jacknich       : user

Deleting Users

The esusers userdel command deletes a user.

userdel <username>

About esusers

The esusers tool manipulates two files, users and users_roles, in CONFIG_DIR/shield/. These two files store all user data for the esusers realm and are read by Shield on startup.

By default, Shield checks these files for changes every 5 seconds. You can change this default behavior by changing the value of the watcher.interval.high setting in the elasticsearch.yml file.

Important

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 esusers command-line tool to apply the required changes.

The users File

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
Note

The esusers command-line tool uses bcrypt to hash the password by default.

The users_roles File

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.

User Cache

The user credentials are not stored on disk in clear text. The esusers creates a bcrypt hashes of the passwords and stores those. bcrypt is considered to be highly secured hash and by default it uses 10 rounds to generate the salts it hashes with. While highly secured, it is also relatively slow. For this reason, Shield also introduce an in-memory cache over the esusers store. This cache can use a different hashing algorithm for storing the passwords in memeory. The default hashing algorithm that is used is ssha256 - a salted SHA-256 algorithm.

We’ve seen in the table above that the cache characteristics can be configured. The following table describes the different hash algorithm that can be set:

Table 5. Cache hash algorithms

Algorithm

Description

ssha256

Uses a salted SHA-256 algorithm (default).

md5

Uses MD5 algorithm.

sha1

Uses SHA1 algorithm.

bcrypt

Uses bcrypt algorithm with salt generated in 10 rounds.

bcrypt4

Uses bcrypt algorithm with salt generated in 4 rounds.

bcrypt5

Uses bcrypt algorithm with salt generated in 5 rounds.

bcrypt6

Uses bcrypt algorithm with salt generated in 6 rounds.

bcrypt7

Uses bcrypt algorithm with salt generated in 7 rounds.

bcrypt8

Uses bcrypt algorithm with salt generated in 8 rounds.

bcrypt9

Uses bcrypt algorithm with salt generated in 9 rounds.

noop,clear_text

Doesn’t hash the credentials and keeps it in clear text in memory. CAUTION: keeping clear text is considered insecure and can be compromised at the OS level (e.g. memory dumps and ptrace).


Cache Eviction API

Shield exposes an API to force cached user eviction. The following example, evicts all users from the esusers realm:

$ curl -XPOST 'http://localhost:9200/_shield/realm/esusers/_cache/clear'
Note

if no realm is defined, the default realm name, default_esusers can be used to clear the cache of the default esusers realm.

It is also possible to evict specific users:

$ curl -XPOST 'http://localhost:9200/_shield/realm/esusers/_cache/clear?usernames=rdeniro,alpacino'

Multiple realms can also be specified using comma-delimited list:

$ curl -XPOST 'http://localhost:9200/_shield/realm/esusers,ldap1/_cache/clear'