Configure SAML with Microsoft ADFS using Microsoft Windows Server 2016

This document provides steps to configure SAML 2.0 with Microsoft ADFS for Mattermost and Microsoft Windows Server 2016.

Before You Begin

Before you begin, you need generate encryption certificates for encrypting the SAML connection.

  1. You can use the Bash script from the mattermost/docs repository on GitHub, or any other suitable method.

  2. Save the two files that are generated. They are the private key and the public key. In the System Console, they are referred to as the Service Provider Private Key and the Service Provider Public Certificate respectively.

Prerequisites

  • An Active Directory instance where all users have specified email and username attributes. For Mattermost servers running 3.3 and earlier, users must also have their first name and last name attributes specified.

  • A running Microsoft Server. The screenshots used in this guide are from Microsoft Server 2012R2, but similar steps should work for other versions.

  • An SSL certificate to sign your ADFS login page.

  • ADFS installed on your Microsoft Server. You can find a detailed guide for deploying and configuring ADFS in this article.

On your ADFS installation, open the ADFS console. Select Service, then select Endpoints. In the Type column, search for SAML 2.0/WS-Federation and note down the value of URL Path column. This is also known as the SAML SSO URL Endpoint in this guide. If you chose the defaults for the installation, this will be /adfs/ls.

Add a Relying Party Trust

  1. Open the ADFS management snap-in, then select AD FS > Relying Party Trusts > Add Relying Party Trust from the right sidebar. You can also right-click Relying Party Trusts, then select Add Relying Party Trust from the context menu.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_000.png
  2. On the Welcome screen of the configuration wizard, select Claims aware, then select Start.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_001.png
  3. On the Select Data Source screen, select Enter data about the relying party manually.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_002.png
  4. On the Specify Display Name screen, enter a Display Name (e.g., Mattermost). You can add optional notes.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_003.png
  5. On the Configure Certificate screen, leave the certificate settings at their default values.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_004.png

If you would like to set up encryption for your SAML connection, select Browse, then upload your Service Provider Public Certificate.

../_images/SSO-SAML-ADFS_add-new-relying-party-trust_005.png
  1. On the Configure URL screen, select Enable Support for the SAML 2.0 WebSSO protocol, then enter the SAML 2.0 SSO service URL in the following format:https://<your-mattermost-url>/login/sso/saml where <your-mattermost-url> should typically match the Mattermost Site URL.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_006.png
  2. On the Configure Identifiers screen, enter the Relying party trust identifier. This identifies the claims being requested. The SAML 2.0 SSO service URL format should be https://<your-mattermost-url>/login/sso/saml where <your-mattermost-url> matches your Mattermost Site URL. Then choose Next.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_007.png ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_008.png

This string must match the Service Provider Identifier string. For more information about the Relying party trust identifier and how prefix matching is applied see this documentation.

Add your SAML 2.0 SSO service URL using this same process.

  1. On the Choose Access Control Policy screen, select the access control policy suitable for your environment. This guide assumes the default values Permit everyone and an unchecked box.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_009.png
  2. On the Ready to Add Trust screen, review your settings.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_010.png
  3. On the Finish screen, select Configure claims issuance policy for this application, then select Close.

    ../_images/SSO-SAML-ADFS_add-new-relying-party-trust_011.png

Create Claim Rules

  1. In the Issuance Transform Rules tab of the Claim Rules editor, select Add Rule….

    ../_images/SSO-SAML-ADFS_create-claim-rules_001.png
  2. On the Choose Rule Type screen, select Send LDAP Attributes as Claims from the drop-down menu, then select Next.

    ../_images/SSO-SAML-ADFS_create-claim-rules_002.png
  3. On the Configure Claim Rule screen, enter a Claim Rule Name of your choice, select Active Directory as the Attribute Store, then add the following mapping:

  • From the LDAP Attribute column, select E-Mail-Addresses. From the Outgoing Claim Type, type Email.

  • From the LDAP Attribute column, select E-Mail-Addresses. From the Outgoing Claim Type, type Name ID.

  • From the LDAP Attribute column, select Given-Name. From the Outgoing Claim Type, type FirstName.

  • From the LDAP Attribute column, select Surname. From the Outgoing Claim Type, type LastName.

  • From the LDAP Attribute column, select SAM-Account-Name. From the Outgoing Claim Type, type Username.

From Mattermost version 3.4, the FirstName and LastName attributes are optional.

Select Finish to add the rule.

The entries in the Outgoing Claim Type column can be modified. The entries may contain dashes but no spaces. They are used to map the corresponding fields in Mattermost.

../_images/SSO-SAML-ADFS_create-claim-rules_003.png
  1. Select Add Rule to create another new rule.

  2. On the Choose Rule Type screen, select Transform an Incoming Claim from the drop-down menu, then select Next.

    ../_images/SSO-SAML-ADFS_create-claim-rules_004.png
  3. On the Configure Claim Rule screen, enter a Claim Rule Name of your choice, then:

  • Select Name ID for the Incoming claim type

  • Select Unspecified for the Incoming name ID format

  • Select E-Mail Address for the Outgoing claim type

Select Pass through all claim values, then select Finish.

../_images/SSO-SAML-ADFS_create-claim-rules_005.png
  1. Select Finish to create the claim rule, then select OK to finish creating rules.

  2. Open Windows PowerShell as an administrator, then run the following command:

Set-ADFSRelyingPartyTrust -TargetName <display-name> -SamlResponseSignature "MessageAndAssertion"

where <display-name>``is the name you specified in step 4 when you added a relying party trust. In this example, ``<display-name> would be mattermost.

This action adds the signature to SAML messages, making verification successful.

Export Identity Provider Certificate

Next, export the identity provider certificate, which will be later uploaded to Mattermost to finish SAML configuration.

  1. Open the ADFS management snap-in, select AD FS > Service > Certificates, then double-click on the certificate under Token-signing. You can also right-click the field, then select View Certificate in the context menu.

    ../_images/SSO-SAML-ADFS_export-id-provider-cert_001.png
  2. On the Certificate screen, open the Details tab, select Copy to File, then select OK.

    ../_images/SSO-SAML-ADFS_export-id-provider-cert_003.png
  3. On the Certificate Export Wizard screen, select Next.

    ../_images/SSO-SAML-ADFS_export-id-provider-cert_004.png
  4. Select Base-64 encoded X.509 (.CER), then select Next again.

    ../_images/SSO-SAML-ADFS_export-id-provider-cert_005.png
  5. On the Certificate Export Wizard screen, select Browse to specify the location where you want the Identity Provider Certificate to be exported, then specify the file name.

    ../_images/SSO-SAML-ADFS_export-id-provider-cert_006.png
  6. Select Save. On the Certificate Export Wizard screen, verify the file path is correct, then select Next.

  7. In the Completing the Certificate Export Wizard, select Finish, then select OK to confirm the export was successful.

    ../_images/SSO-SAML-ADFS_export-id-provider-cert_007.png

Configure SAML Sign-in for Mattermost

Create a metadata URL by appending “FederationMetadata/2007-06/FederationMetadata.xml” to the root URL of the ADFS server, for example: https://<adfs.domain.com>/federationmetadata/2007-06/FederationMetadata.xml>.

Next, start the Mattermost server, then sign into Mattermost as a System Administrator. Go to System Console > Authentication > SAML, paste the metadata URL in the Identity Provider Metadata URL field, then select Get SAML Metadata from IdP.

This populates the SAML SSO URL and the Identity Provider Issuer URL fields automatically. The Identity Provider Public Certificate is also downloaded from the server and set locally.

The following fields can be selected:
  • Set Enable Login With SAML 2.0 to true.

  • Set Enable Synchronizing SAML Accounts With AD/LDAP to suit your environment.

  • Set Override SAML bind data with AD/LDAP information to suit your environment.

If you don’t plan to use a metadata URL, you can manually enter the following fields:
  • For SAML SSO URL use the SAML 2.0/W-Federation URL ADFS Endpoint you copied at the beginning of the process.

  • For Identity Provider Issuer URL use the Relying party trust identifier from ADFS.

  • For Identity Provider Public Certificate use the``X.509 Public Certificate``.

    ../_images/SSO-SAML-ADFS_configure-saml_001.png
  1. Configure Mattermost to verify the signature.

  • Set Verify Signature to true.

  • For Service Provider Login URL use the SAML 2.0 SSO service URL you specified in ADFS.

    ../_images/SSO-SAML-ADFS_configure-saml_002.png
  1. Enable encryption.

  • Set Enable Encryption to true.

  • For Service Provider Private Key use the Service Provider Private Key generated at the start of this process.

  • For Service Provider Public Certificate use the Service Provider Public Certificate you generated at the start of this process.

  • Set Sign Request to suit your environment.

    ../_images/SSO-SAML-ADFS_configure-saml_003.png
  1. Set attributes for the SAML Assertions, which will be used to update user information in Mattermost. Attributes for email and username are required and should match the values you entered in ADFS earlier. See documentation on SAML configuration settings for more detail.

For Mattermost servers running 3.3 and earlier, the first name and last name attributes are also required fields.

../_images/SSO-SAML-ADFS_configure-saml_004.png
  1. Select Save.

  2. (Optional) If you configured First Name Attribute and the Last Name Attribute, go to System Console > Site Configuration > Users and Teams, then set Teammate Name Display to Show first and last name. This is recommended for a better user experience.

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 Account Settings > Security > Sign-in Method > Switch to SAML SSO, then sign in with your SAML credentials to complete the switch.

We also recommend that you post an announcement about how the migration will work to your users.

You may also configure SAML for ADFS by editing the config.json file to enable SAML based on SAML configuration settings. You must restart the Mattermost server for the changes to take effect.

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.

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.

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.