== 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:

* <<esusers-add,Adding users>>
* <<esusers-list,Listing users and roles>>
* <<esusers-pass,Managing user passwords>>
* <<esusers-roles,Managing users' roles>>
* <<esusers-del,Removing users>>

[float]
[[esusers-add]]
=== 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.

[source,shell]
----------------------------------------
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.

[source,shell]
----------------------------------------------------
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.

[source,shell]
-------------------------------------------------------------------
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.

[source,shell]
---------------------------------------------------------
esusers useradd jacknich -p theshining -r logstash,marvel
---------------------------------------------------------

For valid role names please see <<valid-role-name, Role Definitions>>.

[float]
[[esusers-list]]
=== Listing Users
The `esusers list` command lists the users registered in the _esusers_ realm, as in the following example:

[source, shell]
----------------------------------
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.

[source,shell]
-----------------------------------
esusers list jacknich
jacknich       : marvel,logstash
-----------------------------------

[float]
[[esusers-pass]]
=== 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.

[source,shell]
--------------------------------------------------
esusers passwd <username>
--------------------------------------------------

[source,shell]
--------------------------------------------------
esusers passwd <username> -p <password>
--------------------------------------------------

[float]
[[esusers-roles]]
=== 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.

[source,shell]
------------------------------------------------------------------------------------------------------------
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:

[source,shell]
---------------------------------------------------------------
esusers roles jacknich -r logstash,marvel -a user
---------------------------------------------------------------

Listing the user displays the new role assignment:

[source,shell]
---------------------------------
esusers list jacknich
jacknich       : user
---------------------------------

[float]
[[esusers-del]]
=== Deleting Users

The `esusers userdel` command deletes a user.

[source,shell]
--------------------------------------------------
userdel <username>
--------------------------------------------------

[float]
=== 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.

[float]
[[users-file]]
==== 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.

[source,bash]
----------------------------------------------------------------------
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.

[float]
[[users_defining-roles]]
==== The `users_roles` File

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

[source,shell]
--------------------------------------------------
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.

[float]
[[user-cache]]
==== 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 <<esusers-settings,above>> that the cache characteristics can be configured. The following table
describes the different hash algorithm that can be set:

[[esusers-cache-hash-algo]]

.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`).
|=======================

[float]
[[cache-eviction-api]]
==== Cache Eviction API
Shield exposes an API to force cached user eviction. The following example, evicts all users from the `esusers`
realm:

[source, java]
------------------------------------------------------------
$ 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:

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

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

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