A secure Elasticsearch cluster can authenticate users from a Active Directory using the LDAP protocol. With the Active Directory Realm Authentication, you can assign roles to Active Directory groups. When a user authenticates with Active Directory, the privileges for that user are the union of all privileges defined by the roles assigned to the set of groups that the user belongs to.
The Active Directory Realm uses LDAP to communicate with Active Directory. The Active Directory Realm is similar to the LDAP realm but takes advantage of extra features and streamlines configuration.
A general overview of LDAP will help with the configuration. LDAP databases, like Active Directory, store users and
groups hierarchically, similar to the way folders are grouped in a file system. The path to any
entry is a Distinguished Name, or DN. A DN uniquely identifies a user or group. User and group names typically use
attributes such as common name (
cn) or unique ID (
uid). An LDAP directory’s hierarchy is built from containers
such as the organizational unit (
ou), organization (
o), or domain controller (
LDAP ignores white space in a DN definition. The following two DNs are equivalent:
"cn=admin,dc=example,dc=com" "cn =admin ,dc= example , dc = com"
Although optional, connections to the Active Directory server should use the Secure Sockets Layer (SSL/TLS) protocol to protect passwords. Clients and nodes that connect via SSL/TLS to the LDAP server require the certificate or the root CA for the server. These certificates should be put into each node’s keystore/truststore.
Like all realms, the
active_directory realm is configured under the
shield.authc.realms settings namespace in the
elasticsearch.yml file. The following snippet shows an example of such configuration:
Example Active Directory Configuration.
shield: authc: realms: active_directory: type: active_directory order: 0 domain_name: example.com unmapped_groups_as_roles: true ...
Table 5. Active Directory Realm Settings
Indicates the realm type and must be set to
Indicates the priority of this realm within the realm chain. Realms with lower order will be consulted first. Although not required, it is highly recommended to explicitly set this value when multiple realms are configured. Defaults to
Indicates whether this realm is enabled/disabled. Provides an easy way to disable realms in the chain without removing their configuration. Defaults to
Specifies the domain name of the Active Directory. The cluster can derive the LDAP URL and
Specifies a LDAP URL in the form of
Specifies the context to search for the user. The default value for this element is the root of the Active Directory domain.
Specifies whether the user search should be
Specifies a filter to use to lookup a user given a username. The default filter looks up
Specifies the context to search for groups in which the user has membership. The default value for this element is the root of the Active Directory domain.
Specifies whether the group search should be
When set to
When set to
Specified the time-to-live for cached user entries (a user and its credentials will be cached for this configured period of time). Defaults to
Specified the maximum number of user entries that can live in the cache at a given time. Defaults to 100,000.
(Expert Setting) Specifies the hashing algorithm that will be used for the in-memory cached user credentials (see here for possible values).
Active Directory authentication expects the username entered to be the same name as the
userPrincipalName and not the
CommonName (CN). The URL is optional, but allows the use of custom ports.
Binding to Active Directory fails when the domain name is not mapped in DNS. If DNS is not being provided
by a Windows DNS server, add a mapping for the domain in the local
By default, the mapping file that connects groups and roles is
config/shield/role_mapping.yml. You can configure
the path and name of the mapping file by setting the appropriate value for the
configuration parameter. When you map roles to groups, the roles of a user in that group are the combination of the roles
assigned to that group and the roles assigned to that user.
role_mapping.yml file uses the YAML format. Within a mapping file, Elasticsearch roles are keys and
Active Directory groups are values. Groups and roles can have a many-to-many mapping.
Example Group and Role Mapping File.
# Example LDAP group mapping configuration: # roleA this is an elasticsearch role # - groupA-DN this is any group distinguished name # - groupB-DN monitoring: - "cn=admins,dc=example,dc=com" user: - "cn=users,dc=example,dc=com" - "cn=admins,dc=example,dc=com"
After setting up group-to-role mappings, copy this file to each node node. Tools like Puppet or Chef can help with this.
To use SSL/TLS to access your Active Directory server over an URL with the
ldaps protocol, make sure the client
used by Shield can access the certificate of the CA that signed the LDAP server’s certificate. This will enable
Shield’s client to authenticate the Active Directory server before sending any passwords to it.
To do this, first obtain a certificate for the Active Directory servers or a CA certificate that has signed the certificate.
You can use the
openssl command to fetch the certificate and add the certificate to the
ldap.crt file, as in
the following Unix example:
echo | openssl s_client -connect ldap.example.com:636 2>/dev/null | openssl x509 > ldap.crt
This certificate needs to be stored in the node keystore/truststore. Import the certificate into the truststore with the following command, providing the password for the keystore when prompted.
keytool -import -keystore node01.jks -file ldap.crt
If not already configured, add the path of the keystore/truststore to
elasticsearch.yml as described in Securing Nodes.
By default, Shield will attempt to verify the hostname or IP address used in the
url with the values in the
certificate. If the values in the certificate do not match, Shield will not allow a connection to the Active Directory server.
This behavior can be disabled by setting the
Finally, restart Elasticsearch to pick up the changes to
To avoid connecting to the Active Directory server for every incoming request, the users and their credentials are cached locally on each node. This is a common practice when authenticating against remote servers and as can be seen in the table above, the characteristics of this cache are configurable.
The cached user credentials are hashed in memory, and there are several hash algorithms to choose from:
Table 6. Cache hash algorithms
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
Shield exposes an API to force cached user eviction. The following example, evicts all users from the
$ curl -XPOST 'http://localhost:9200/_shield/realm/ad1/_cache/clear'
It is also possible to evict specific users:
$ curl -XPOST 'http://localhost:9200/_shield/realm/ad1/_cache/clear?usernames=rdeniro,alpacino'
Multiple realms can also be specified using comma-delimited list:
$ curl -XPOST 'http://localhost:9200/_shield/realm/ad1,ad2/_cache/clear'