SAML

The Security plugin supports user authentication through SAML single sign-on. The Security plugin implements the web browser SSO profile of the SAML 2.0 protocol.

This profile is meant for use with web browsers. It is not a general-purpose way of authenticating users against the Security plugin, so its primary use case is to support OpenSearch Dashboards single sign-on.

Docker example

We provide a fully functional example that can help you understand how to use SAML with OpenSearch Dashboards.

  1. Visit the saml-demo branch of the demos repository and download it to a folder of your choice. If you’re not familiar with how to use GitHub, see the OpenSearch onboarding guide for instructions.

  2. Navigate to the demo folder:

    1. $ cd <path-to-demos-folder>/demo
  3. Review the following files, as needed:

    • .env:
      • Defines the OpenSearch and OpenSearch Dashboards version to use. The default is the latest version (2.15).
      • Defines the OPENSEARCH_INITIAL_ADMIN_PASSWORD variable required by versions 2.12 and later.
    • ./custom-config/opensearch_dashboards.yml: Includes the SAML settings for the default opensearch_dashboards.yml file.
    • ./custom-config/config.yml: Configures SAML for authentication.
    • docker-compose.yml: Defines an OpenSearch server node, an OpenSearch Dashboards server node, and a SAML server node.
    • ./saml/config/authsources.php: Contains the list of users that can be authenticated by this SAML domain.
  4. From the command line, run:

    1. $ docker-compose up.
  5. Access OpenSearch Dashboards at http://localhost:5601.

  6. Select Log in with single sign-on. This redirects you to the SAML login page.

  7. Log in to OpenSearch Dashboards with a user defined in ./saml/config/authsources.php (such as user1 with password user1pass).

  8. After logging in, note that the user ID shown in the upper-right corner of the screen is the same as the NameID attribute for the user defined in ./saml/config/authsources.php of the SAML server (that is, saml-test for user1).

  9. If you want to examine the SAML server, run docker ps to find its container ID and then docker exec -it <container-id> /bin/bash.

    In particular, you might find it helpful to review the contents of the /var/www/simplesamlphp/config/ and /var/www/simplesamlphp/metadata/ directories.

Activating SAML

To use SAML for authentication, you need to configure a respective authentication domain in the authc section of config/opensearch-security/config.yml. Because SAML works solely on the HTTP layer, you do not need any authentication_backend and can set it to noop. Place all SAML-specific configuration options in this chapter in the config section of the SAML HTTP authenticator:

  1. _meta:
  2. type: "config"
  3. config_version: 2
  4. config:
  5. dynamic:
  6. authc:
  7. saml_auth_domain:
  8. http_enabled: true
  9. transport_enabled: false
  10. order: 1
  11. http_authenticator:
  12. type: saml
  13. challenge: true
  14. config:
  15. idp:
  16. metadata_file: okta.xml
  17. ...
  18. authentication_backend:
  19. type: noop

After you have configured SAML in config.yml, you must also activate it in OpenSearch Dashboards.

Running multiple authentication domains

We recommend adding at least one other authentication domain, such as LDAP or the internal user database, to support API access to OpenSearch without SAML. For OpenSearch Dashboards and the internal OpenSearch Dashboards server user, you also must add another authentication domain that supports basic authentication. This authentication domain should be placed first in the chain, and the challenge flag must be set to false:

  1. _meta:
  2. type: "config"
  3. config_version: 2
  4. config:
  5. dynamic:
  6. authc:
  7. basic_internal_auth_domain:
  8. http_enabled: true
  9. transport_enabled: true
  10. order: 0
  11. http_authenticator:
  12. type: basic
  13. challenge: false
  14. authentication_backend:
  15. type: internal
  16. saml_auth_domain:
  17. http_enabled: true
  18. transport_enabled: false
  19. order: 1
  20. http_authenticator:
  21. type: saml
  22. challenge: true
  23. config:
  24. ...
  25. authentication_backend:
  26. type: noop

Identity provider metadata

A SAML identity provider (IdP) provides a SAML 2.0 metadata file describing the IdP’s capabilities and configuration. The Security plugin can read IdP metadata either from a URL or a file. The choice that you make depends on your IdP and your preferences. The SAML 2.0 metadata file is required.

NameDescription
idp.metadata_fileThe path to the SAML 2.0 metadata file of your IdP. Place the metadata file in the config directory of OpenSearch. The path has to be specified relative to the config directory. Required if idp.metadata_url is not set.
idp.metadata_urlThe SAML 2.0 metadata URL of your IdP. Required if idp.metadata_file is not set.

IdP and service provider entity ID

An entity ID is a globally unique name for a SAML entity, either an IdP or a service provider (SP). The IdP entity ID is usually provided by your IdP. The SP entity ID is the name of the configured application or client in your IdP. We recommend adding a new application for OpenSearch Dashboards and using the URL of your OpenSearch Dashboards installation as the SP entity ID.

NameDescription
idp.entity_idThe entity ID of your IdP. Required.
sp.entity_idThe entity ID of the service provider. Required.

Time disparity compensation for JWT validation

Occasionally you may find that the clock times between the authentication server and the OpenSearch node are not perfectly synchronized. When this is the case, even by a few seconds, the system that either issues or receives a JSON Web Token (JWT) may try to validate nbf (not before) and exp (expiration) claims and fail to authenticate the user due to the time disparity.

By default, OpenSearch Security allows for a window of 30 seconds to compensate for possible misalignment between server clock times. To set a custom value for this feature and override the default, you can add the jwt_clock_skew_tolerance_seconds setting to the config.yml.

  1. http_authenticator:
  2. type: saml
  3. challenge: true
  4. config:
  5. idp:
  6. metadata_file: okta.xml
  7. jwt_clock_skew_tolerance_seconds: 20

OpenSearch Dashboards settings

The web browser SSO profile exchanges information through HTTP GET or POST. For example, after you log in to your IdP, it sends an HTTP POST back to OpenSearch Dashboards containing the SAML response. You must configure the base URL of your OpenSearch Dashboards installation where the HTTP requests are being sent to.

NameDescription
kibana_urlThe OpenSearch Dashboards base URL. Required.

Username and Role attributes

Subjects (for example, user names) are usually stored in the NameID element of a SAML response:

  1. <saml2:Subject>
  2. <saml2:NameID>admin</saml2:NameID>
  3. ...
  4. </saml2:Subject>

If your IdP is compliant with the SAML 2.0 specification, you do not need to set anything special. If your IdP uses a different element name, you can also specify its name explicitly.

Role attributes are optional. However, most IdPs can be configured to add roles in the SAML assertions as well. If present, you can use these roles in your role mappings:

  1. <saml2:Attribute Name='Role'>
  2. <saml2:AttributeValue >Everyone</saml2:AttributeValue>
  3. <saml2:AttributeValue >Admins</saml2:AttributeValue>
  4. </saml2:Attribute>

If you want to extract roles from the SAML response, you need to specify the element name that contains the roles.

NameDescription
subject_keyThe attribute in the SAML response where the subject is stored. Optional. If not configured, the NameID attribute is used.
roles_keyThe attribute in the SAML response where the roles are stored. Optional. If not configured, no roles are used.

Request signing

Requests from the Security plugin to the IdP can optionally be signed. Use the following settings to configure request signing.

NameDescription
sp.signature_private_keyThe private key used to sign the requests or to decode encrypted assertions. Optional. Cannot be used when private_key_filepath is set.
sp.signature_private_key_passwordThe password of the private key, if any.
sp.signature_private_key_filepathPath to the private key. The file must be placed under the OpenSearch config directory, and the path must be specified relative to that same directory.
sp.signature_algorithmThe algorithm used to sign the requests. See the next table for possible values.

The private key must be in PKCS#8 format. If you want to use an encrypted key, it must be encrypted with a PKCS#12-compatible algorithm (3DES).

The Security plugin supports the following signature algorithms.

AlgorithmValue
DSA_SHA1http://www.w3.org/2000/09/xmldsig#dsa-sha1;
RSA_SHA1http://www.w3.org/2000/09/xmldsig#rsa-sha1;
RSA_SHA256http://www.w3.org/2001/04/xmldsig-more#rsa-sha256;
RSA_SHA384http://www.w3.org/2001/04/xmldsig-more#rsa-sha384;
RSA_SHA512http://www.w3.org/2001/04/xmldsig-more#rsa-sha512;

Logout

Usually, IdPs provide information about their individual logout URL in their SAML 2.0 metadata. If this is the case, the Security plugin uses them to render the correct logout link in OpenSearch Dashboards. If your IdP does not support an explicit logout, you can force a re-login when the user visits OpenSearch Dashboards again.

NameDescription
sp.forceAuthnForce a re-login even if the user has an active session with the IdP.

Currently, the Security plugin supports only the HTTP-Redirect logout binding. Make sure this is configured correctly in your IdP.

Exchange key settings

SAML, unlike other protocols, is not meant to be used for exchanging user credentials with each request. The Security plugin trades the SAML response for a lightweight JWT that stores the validated user attributes. This token is signed by an exchange key of your choice. Note that when you change this key, all tokens signed with it become invalid immediately.

NameDescription
exchange_keyThe key to sign the token. The algorithm is HMACSHA512, therefore we recommend to use 64 characters, for example 9a2h8ajasdfhsdiydfn7dtd6d5ashsd89a2h8ajasdHhsdiyLfn7dtd6d5ashsdI. Ensure that you enter a value for exchange_key, otherwise an error is returned.

TLS settings

If you are loading the IdP metadata from a URL, we recommend that you use SSL/TLS. If you use an external IdP like Okta or Auth0 that uses a trusted certificate, you usually do not need to configure anything. If you host the IdP yourself and use your own root CA, you can customize the TLS settings as follows. These settings are used only for loading SAML metadata over HTTPS.

NameDescription
idp.enable_sslWhether to enable the custom TLS configuration. Default is false (JDK settings are used).
idp.verify_hostnamesWhether to verify the hostnames of the server’s TLS certificate.

Example:

  1. authc:
  2. saml_auth_domain:
  3. http_enabled: true
  4. transport_enabled: false
  5. order: 1
  6. http_authenticator:
  7. type: saml
  8. challenge: true
  9. config:
  10. idp:
  11. enable_ssl: true
  12. verify_hostnames: true
  13. ...
  14. authentication_backend:
  15. type: noop

Certificate validation

Configure the root CA used for validating the IdP TLS certificate by setting one of the following configuration options:

  1. config:
  2. idp:
  3. pemtrustedcas_filepath: path/to/trusted_cas.pem
  1. config:
  2. idp:
  3. pemtrustedcas_content: |-
  4. -----BEGIN CERTIFICATE-----
  5. MIID/jCCAuagAwIBAgIBATANBgkqhkiG9w0BAQUFADCBjzETMBEGCgmSJomT8ixk
  6. ARkWA2NvbTEXMBUGCgmSJomT8ixkARkWB2V4YW1wbGUxGTAXBgNVBAoMEEV4YW1w
  7. bGUgQ29tIEluYy4xITAfBgNVBAsMGEV4YW1wbGUgQ29tIEluYy4gUm9vdCBDQTEh
  8. ...
  9. -----END CERTIFICATE-----
NameDescription
idp.pemtrustedcas_filepathPath to the PEM file containing the root CAs of your IdP. The files must be placed under the OpenSearch config directory, and you must specify the path relative to that same directory.
idp.pemtrustedcas_contentThe root CA content of your IdP server. Cannot be used when pemtrustedcas_filepath is set.

Client authentication

The Security plugin can use TLS client authentication when fetching the IdP metadata. If enabled, the Security plugin sends a TLS client certificate to the IdP for each metadata request. Use the following keys to configure client authentication.

NameDescription
idp.enable_ssl_client_authWhether to send a client certificate to the IdP server. Default is false.
idp.pemcert_filepathPath to the PEM file containing the client certificate. The file must be placed under the OpenSearch config directory, and the path must be specified relative to the config directory.
idp.pemcert_contentThe content of the client certificate. Cannot be used when pemcert_filepath is set.
idp.pemkey_filepathPath to the private key of the client certificate. The file must be placed under the OpenSearch config directory, and the path must be specified relative to the config directory.
idp.pemkey_contentThe content of the private key of your certificate. Cannot be used when pemkey_filepath is set.
idp.pemkey_passwordThe password of your private key, if any.

Enabled ciphers and protocols

You can limit the allowed ciphers and TLS protocols for the IdP connection. For example, you can only enable strong ciphers and limit the TLS versions to the most recent ones.

NameDescription
idp.enabled_ssl_ciphersArray of enabled TLS ciphers. Only the Java format is supported.
idp.enabled_ssl_protocolsArray of enabled TLS protocols. Only the Java format is supported.

Minimal configuration example

The following example shows the minimal configuration:

  1. _meta:
  2. type: "config"
  3. config_version: 2
  4. config:
  5. dynamic:
  6. authc:
  7. saml_auth_domain:
  8. http_enabled: true
  9. transport_enabled: false
  10. order: 1
  11. http_authenticator:
  12. type: saml
  13. challenge: true
  14. config:
  15. idp:
  16. metadata_file: metadata.xml
  17. entity_id: http://idp.example.com/
  18. sp:
  19. entity_id: https://opensearch-dashboards.example.com
  20. kibana_url: https://opensearch-dashboards.example.com:5601/
  21. roles_key: Role
  22. exchange_key: 'peuvgOLrjzuhXf ...'
  23. authentication_backend:
  24. type: noop

OpenSearch Dashboards configuration

Because most of the SAML-specific configuration is done in the Security plugin, just activate SAML in your opensearch_dashboards.yml by adding the following:

  1. opensearch_security.auth.type: "saml"

In addition, you must add the OpenSearch Dashboards endpoint for validating the SAML assertions to your allow list:

  1. server.xsrf.allowlist: ["/_opendistro/_security/saml/acs"]

If you use the logout POST binding, you also need to ad the logout endpoint to your allow list:

  1. server.xsrf.allowlist: ["/_opendistro/_security/saml/acs", "/_opendistro/_security/saml/logout"]

To include SAML with other authentication types in the Dashboards sign-in window, see Configuring sign-in options.

Session management with additional cookies

To improve session management—especially for users who have multiple roles assigned to them—Dashboards provides an option to split cookie payloads into multiple cookies and then recombine the payloads when receiving them. This can help prevent larger SAML assertions from exceeding size limits for each cookie. The two settings in the following example allow you to set a prefix name for additional cookies and specify the number of them. They are added to the opensearch_dashboards.yml file. The default number of additional cookies is three:

  1. opensearch_security.saml.extra_storage.cookie_prefix: security_authentication_saml
  2. opensearch_security.saml.extra_storage.additional_cookies: 3

Note that reducing the number of additional cookies can cause some of the cookies that were in use before the change to stop working. We recommend establishing a fixed number of additional cookies and not changing the configuration after that.

If the ID token from the IdP is especially large, OpenSearch may throw a server log authentication error indicating that the HTTP header is too large. In this case, you can increase the value for the http.max_header_size setting in the opensearch.yml file.

IdP-initiated SSO

To use IdP-initiated SSO, set the Assertion Consumer Service endpoint of your IdP to this:

  1. /_opendistro/_security/saml/acs/idpinitiated

Then add this endpoint to server.xsrf.allowlist in opensearch_dashboards.yml:

  1. server.xsrf.allowlist: ["/_opendistro/_security/saml/acs/idpinitiated", "/_opendistro/_security/saml/acs", "/_opendistro/_security/saml/logout"]