Configure SAML with Keycloak 

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The following process provides steps to configure SAML with Keycloak for Mattermost.

Set up a connection app for Mattermost SSO 

Note

This was tested with Keycloak v18.0.0.

Additionally, you don’t typically need to make a realm dedicated to Mattermost. We recommend adding Mattermost as a client to your primary realm.

  1. Log in to Keycloak as an administrator.

  2. Select Clients, then Create and Save. You’ll use this client ID in a later step.

    • Client ID: mattermost

    • Client Protocol: saml

  3. Edit the Mattermost client to have the below values:

    • Enabled: ON

    • Encrypt Assertions: ON

    • Force Name ID Format: ON

    • Name ID Format: Email

    • Valid Redirects: https://<<siteURL>>/login/sso/saml

    • Base URL: https://<<siteURL>>/login/sso/saml

In Keycloak, create the Mattermost client, specify the Client ID and Client Protocol, then save your changes.

  1. Save the client config.

  2. Navigate to Keys within the client config.

  3. Select Generate new keys.

  4. Select Export, use the values below, and then select Download. Once you’ve downloaded it, navigate back to the Mattermost client in Keycloak for the next steps.

    • Archive Format: PKCS12

    • Key Alias: mattermost

    • Key Password: mattermost

    • Store Password: mattermost

    Note

    In the image below, we used Mattermost for the Realm Certificate Alias. You can use any value that you would like here, as it’s designed to identify what this certificate is within your Keycloak realm.

In Keycloak, on the Keys tab, generate new keys, export using the values documented, then select Download.

  1. Add the default attributes:

    1. Within your Mattermost client select Mappers.

    2. Select Add Buildin

    3. Select the X500 email, X500 givenName, and X500 surname attributes.

    4. Select Add selected.

In Keycloak, on the Mappers tab, add default attributes

  1. Add the username and ID attribute.

    If you’re planning to sync your SAML users with LDAP within Mattermost, the ID value used here must match with your Mattermost LDAP ID Attribute.

    1. With the Mappers section of your client, select Create.

    2. Set Name to Username.

    3. Under Mapper Type select User Property.

    4. Set Property to username (This is case sensitive and must be lowercase).

    5. Set SAML Attribute Name to username.

    6. Select Save.

    7. Repeat this step and use the property of id to create the ID Attribute.

Example of protocol mapper configuration.

  1. Get the metadata URL from Keycloak:

    1. Within your Realm, select Realm Settings.

    2. At the bottom of the General tab you should see a SAML 2.0 Identity Provider Metadata endpoint. Right-click and copy this URL. Store for the next step.

Within your Realm, select Realm Settings. At the bottom of the General tab, you should see a SAML 2.0 Identify Provider Metadata endpoint. Copy this URL for the next step.

Configure SAML for Mattermost 

  1. Start the Mattermost server and log in to Mattermost as a System Administrator. Go to System Console > Authentication > SAML.

  2. Set the Identity Provider Metadata URL to the value you copied from the step above and select Get SAML Metadata from IdP. The metadata import will populate fields related to your Keycloak configuration.

    If you have any issues with this import, you can check the mattermost.log file for more information. You will need to turn on debug logging and try again if you do not already have debug logging enabled.

In Mattermost, configure SAML in the System Console by going to Authentication > SAML. Set the Identity Provider Metadata URL to the value you copied in the previous step. When you select Get SAML Metadata from IdP, fields related to your Keycloak configuration are populated.

  1. Set the below fields:

    • Verify Signature: false

    • Service Provider Login URL: http://<<siteURL>>/login/sso/saml

    • Service Provider Identifier: mattermost

    The Service Provider Identifier will match the Client ID that you configured in the second Keycloak step.

In the System Console, configure SAML as documented, where the Service Provider Identifier matches the Client ID you configured in Keycloak.

  1. Configure the Encryption using the key you downloaded in step 8 of the Keycloak config.

    1. Generate the .crt file from the .p12 file.

      openssl pkcs12 -in keystore.p12 -out mattermost.crt -nodes

    2. Generate the .key file from the .p12 file.

      openssl pkcs12 -in keystore.p12 -out mattermost.key -nodes -nocerts

    3. Upload both of these files within the Mattermost System Console. Make sure to select Upload.

    • Service Provider Private Key: mattermost.key

    • Service Provider Private Certificate: mattermost.crt

In the System Console, upload both the Service Provider Private Key and the Service Provider Private Certificate.

  1. (Optional) Set up request signing with the below parameters.

In the System Console, you can optionally request signing with configured parameters.

  1. Set attributes for the SAML Assertions, which will update user information in Mattermost.

    The attributes below are from steps 8 and 9 above. These values must be the SAML Attribute Name within Keycloak. See documentation on SAML configuration settings for more details.

    • Email Attribute: email

    • Username Attribute: username

    • Id Attribute: id

Set attributes for the SAML assertions which updates user information in Mattermost.

  1. Select Save.

You’re done! If you’d like to confirm SAML SSO is successfully enabled, switch your System Administrator account from email to SAML-based authentication via Profile > Security > Sign-in Method > Switch to SAML SSO and log in with your SAML credentials to complete the switch.

It’s also recommended to post an announcement about how the migration will work for users.

You may also configure SAML for Keycloak by editing config.json. Before starting the Mattermost server, edit config.json to enable SAML based on SAML configuration settings. You must restart the Mattermost server for the changes to take effect.

Configure SAML synchronization with AD/LDAP 

In addition to configuring SAML sign-in, you can optionally configure synchronizing SAML accounts with AD/LDAP. When configured:

  • Mattermost queries AD/LDAP for relevant account information and updates SAML accounts based on changes to attributes (first name, last name, and nickname)

  • Accounts disabled in AD/LDAP are made inactive in Mattermost, and their active sessions are revoked once Mattermost synchronizes attributes.

To configure SAML synchronization with AD/LDAP:

  1. Go to System Console > Authentication > SAML 2.0, then set Enable Synchronizing SAML Accounts With AD/LDAP to true.

  2. Go to System Console > Authentication > AD/LDAP, then set Enable Synchronization with AD/LDAP to true.

  3. To ignore guest users when sychronizing, go to System Console > Authentication > SAML 2.0, then set Ignore Guest Users when Synchronizing with AD/LDAP to true.

  4. Set the rest of the AD/LDAP settings based on configuration settings documentation to connect Mattermost with your AD/LDAP server.

  • If you don’t want to enable AD/LDAP sign-in, go to System Console > Authentication > AD/LDAP, then set Enable sign-in with AD/LDAP to false.

  1. To specify how often Mattermost synchronizes SAML user accounts with AD/LDAP, go to System Console > Authentication > AD/LDAP, then set a Synchronization Interval in minutes. The default setting is 60 minutes. If you want to synchronize immediately after disabling an account, select AD/LDAP Synchronize Now.

  2. To confirm that Mattermost can successfully connect to your AD/LDAP server, go to System Console > Authentication > AD/LDAP, then select AD/LDAP Test.

Once the synchronization with AD/LDAP is enabled, user attributes are synchronized with AD/LDAP based on their email address. If a user with a given email address doesn’t have an AD/LDAP account, they will be deactivated in Mattermost on the next AD/LDAP sync.

To re-activate the account:

  1. Add the user to your AD/LDAP server.

  2. Purge all caches in Mattermost by going to System Console > Environment > Web Server, then select Purge All Caches.

  3. Run AD/LDAP synchronization by going to System Console > Authentication > AD/LDAP, then select AD/LDAP Synchronize Now.

  4. Purge all caches again in Mattermost by going to System Console > Environment > Web Server, then select Purge All Caches again. This re-activates the account in Mattermost.

Note

If a user is deactivated from AD/LDAP, they will be deactivated in Mattermost on the next sync. They will be shown as “Inactive” in the System Console users list, all of their sessions will expire and they won’t be able to log back in to Mattermost.

If a user is deactivated from SAML, their session won’t expire until they’re deactivated from AD/LDAP. However, they won’t be able to log back in to Mattermost.

Note

SAML synchronization with AD/LDAP is designed to pull user attributes such as first name and last name from your AD/LDAP, not to control authentication.

In particular, the user filter cannot be used to control who can log in to Mattermost, this should be controlled by your SAML service provider’s group permissions.

See technical description of SAML synchronization with AD/LDAP for more details.

Override SAML data with AD/LDAP data 

Alternatively, you can choose to override SAML bind data with AD/LDAP information. For more information on binding a user with the SAML ID Attribute, please refer to this documentation.

This process overrides SAML email address with AD/LDAP email address data or SAML Id Attribute with AD/LDAP Id Attribute if configured. We recommend using this configuration with the SAML ID Attribute to help ensure new users are not created when the email address changes for a user.

To ensure existing user accounts do not get disabled in this process, ensure the SAML IDs match the LDAP IDs by exporting data from both systems and comparing the ID data. Mapping ID Attributes for both AD/LDAP and SAML within Mattermost to fields that hold the same data will ensure the IDs match as well.

  1. Set the SAML Id Attribute by going to System Console > Authentication > SAML 2.0 > Id Attribute.

  2. Set System Console > Authentication > SAML 2.0 > Override SAML bind data with AD/LDAP information to true.

  3. Set System Console > Authentication > SAML 2.0 > Enable Synchronizing SAML Accounts With AD/LDAP to true.

  4. Run AD/LDAP sync by going to System Console > Authentication > AD/LDAP, then select AD/LDAP Synchronize Now.

Frequently Asked Questions 

How to bind authentication to Id attribute instead of email 

Alternatively, you can use an Id attribute instead of email to bind the user. We recommend choosing an ID that is unique and will not change over time.

Configuring with an Id attribute allows you to reuse an email address for a new user without the old user’s information being exposed. For instance, if a user with an email address joe.smith@mattermost.com was once an employee, a new employee named Joe Smith can use the same email. This configuration is also useful when a user’s name changes and their email needs to be updated.

This process was designed with backwards compatibility to email binding. Here is the process applied to new account creations and to accounts logging in after the configuration:

  • A user authenticated with SAML is bound to the SAML service user using the Id Attribute (as long as it has been configured) or bound by email using the email received from SAML.

  • When the user tries to login and the SAML server responds with a valid authentication, then the server uses the “Id” field of the SAML authentication to search the user.

  • If a user bound to that ID already exists, it logs in as that user.

  • If a user bound to that ID does not exist, it will search base on the email.

  • If a user bound to the email exists, it logs in with email and updates the autentication data to the ID, instead of the email.

  • If a user bound to the ID or email does not exist, it will create a new Mattermost account bound to the SAML account by ID and will allow the user to log in.

Note

Existing accounts won’t update until they log in to the server.

Can SAML via Microsoft ADFS be configured with Integrated Windows Authentication (IWA)? 

Yes. IWA is supported on the browser, with support added to iOS and Android mobile apps in Q2/2019 (mobile apps v1.18 and later).

However, IWA is not supported on the Mattermost Desktop Apps due to a limitation in Electron. As a workaround you may create a browser desktop shortcut for quick access to Mattermost, just like a Desktop App.

Can I provision and deprovision users who log in via SAML? 

Yes, but this relies on AD/LDAP to do so. Currently, we do not support SCIM. See “How do I deactivate users?” for more information.

How is SAML different from OAuth 2.0 and OpenId Connect? 

OAuth 2.0 was primarily intended for delegated authorization, where an app is authorized to access resources, such as Google contact list. It doesn’t deal with authentication.

OpenID Connect is built on top of OAuth 2.0, which supports authentication and thus direct SSO.

SAML is like OpenID Connect, except typically used in enterprise settings. OpenID Connect is more common in consumer websites and web/mobile apps.

Learn more at https://hackernoon.com/demystifying-oauth-2-0-and-openid-connect-and-saml-12aa4cf9fdba.