Configure SAML with Microsoft ADFS

The following process provides steps to configure SAML 2.0 with Microsoft ADFS for Mattermost.

Before you begin

Before you configure SAML:

  1. Make sure you have the XML Security Library installed on your Mattermost instance. The XML Security Library is usually included as part of Debian GNU/Linux.
  2. Install the xmlsec1-openssl library
  • On Ubuntu: sudo apt-get install xmlsec1
  • On RHEL: sudo yum install xmlsec1-openssl
  1. 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.
The following are basic requirements to use ADFS for Mattermost:
  • An Active Directory instance where all users have a 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 Microsoft Server running. 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, note down the value of the SAML 2.0/W-Federation URL in ADFS Endpoints section, 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. In ADFS management sidebar, go to AD FS > Trust Relationships > Relying Party Trusts and click Add Relying Party Trust

    ../_images/adfs_1_add_new_relying_party_trust.PNG
  2. A configuration wizard for adding a new relying party trust opens. In the Welcome screen, click Start.

    ../_images/adfs_2_start_wizard.PNG
  3. In the Select Data Source screen, select the option Enter data about the relying party manually.

    ../_images/adfs_3_select_data_source.PNG
  4. In the Specify Display Name screen, enter a Display Name to recognize the trust, such as Mattermost, and add any notes you want to make.

    ../_images/adfs_4_specify_display_name.PNG
  5. In the Choose Profile screen, select the option AD FS profile.

    ../_images/adfs_5_choose_profile.PNG
  6. In the Configure Certificate screen, leave the certificate settings at their default values.

    ../_images/adfs_6_configure_certificate_default.PNG

However, if you would like to set up encryption for your SAML connection, click the Browse button and upload your Service Provider Public Certificate.

../_images/adfs_7_configure_certificate_encryption.PNG
  1. In the Configure URL screen, select the option Enable Support for the SAML 2.0 WebSSO protocol and enter the SAML 2.0 SSO service URL, which is of the form https://<your-mattermost-url>/login/sso/saml where https://<your-mattermost-url> should typically match the Mattermost Site URL.

    ../_images/adfs_8_configure_url.PNG
  2. In the Configure Identifiers screen, enter the Relying party trust identifier (also known as the Identity Provider Issuer URL) of the form https://<your-idp-url>/adfs/services/trust and click Add.

    ../_images/adfs_9_configure_identifiers.PNG
  3. In the Configure Multi-factor Authentication Now screen, you may enable multi-factor authentication, but this is beyond the scope of this guide.

    ../_images/adfs_10_configure_mfa.PNG
  4. In the Choose Issuance Authorization Rules screen, select the option Permit all users to access this relying party.

    ../_images/adfs_11_authorization.PNG
  5. In the Ready to Add Trust screen, you can review your settings.

    ../_images/adfs_12_ready_to_add_trust.PNG
  6. In the Finish screen, select the option Open the Edit Claim Rules dialog for this relying party trust when the wizard closes, and click Close. You will now exit configuration wizard and a Claim Rules editor opens.

    ../_images/adfs_13_finish_trust.PNG

Create Claim Rules

  1. In the Issuance Transform Rules of the Claim Rules editor, click the Add Rule… button. This action opens an Add Transform Claim Rule Wizard.

    ../_images/adfs_14_claim_rules_editor.PNG
  2. In the Choose Rule Type screen, select Send LDAP Attributes as Claims from the drop-down menu, then click Next.

    ../_images/adfs_15_choose_rule_type.PNG
  3. In the Configure Claim Rule screen, enter a Claim Rule Name of your choice, select Active Directory as the Attribute Store and do the following:

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

For Mattermost 3.4 and later, the FirstName and LastName attributes are optional.

Then, click Finish to add the rule.

Note that the entries in the Outgoing Claim Type column can be chosen to be something else. They can contain dashes but no spaces. Note that they will be used to map the corresponding fields in Mattermost later.

../_images/adfs_16_configure_claim_rule.PNG
  1. Create another new rule by clicking the Add Rule button.

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

    ../_images/adfs_17_transformation_of_incoming_claim.PNG
  3. In 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

Moreover, select the Pass through all claim values option. Then click Finish.

../_images/adfs_18_configure_incoming_claim.PNG
  1. Click Finish to create the claim rule, then OK to finish creating rules.
  2. Open Windows PowerShell as an administrator and run the following command:
Set-ADFSRelyingPartyTrust -TargetName <display-name> -SamlResponseSignature "MessageAndAssertion"

where <display-name> is the name you specified in step 7. In our example it would be mattermost.

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

Export Identity Provider Certificate

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

  1. In ADFS management sidebar, go to AD FS > Service > Certificates and double click on the certificate under Token-signing. You may alternatively right-click the field, then click View Certificate

    ../_images/adfs_19_export_idp_cert_start.PNG
  2. In the Certificate screen, go to the Details tab and click Copy to File, then OK. This opens a Certificate Export Wizard.

    ../_images/adfs_20_export_idp_cert_copy.PNG
  3. In the Certificate Export Wizard screen, click Next. Then, select the option Base-64 encoded X.509 (.CER) and click Next again.

    ../_images/adfs_21_export_idp_cert_wizard.PNG
  4. In the Certificate Export Wizard screen, click Browse to specify the location you want the Identity Provider Certificate to be exported, and specify the file name.

    ../_images/adfs_21-2_export_idp_cert_wizard.PNG
  5. Click Save. In the Certificate Export Wizard screen, verify the file path is correct, and click Next.

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

    ../_images/adfs_21-3_export_idp_cert_wizard.PNG

You’re now about to finish configuring SAML for Mattermost!

Configure SAML sign-in for Mattermost

  1. Start Mattermost server and sign into Mattermost as a System Administrator. Go to System Console > Authentication > SAML.
  • SAML SSO URL: SAML 2.0/W-Federation URL ADFS Endpoint you copied earlier.

  • Identity Provider Issuer URL: Relying party trust identifier from ADFS you specified earlier.

  • Identity Provider Public Certificate: X.509 Public Certificate you downloaded earlier.

    ../_images/adfs_22_mattermost_basics.PNG
  1. Configure Mattermost to verify the signature. The Service Provider Login URL is the SAML 2.0 SSO service URL you specified in ADFS earlier.

    ../_images/adfs_23_mattermost_verification.PNG
  2. Enable encryption by uploading the Service Provider Private Key and Service Provider Public Certificate you generated earlier.

    ../_images/adfs_24_mattermost_encryption.PNG
  3. 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/adfs_25_mattermost_attributes.PNG
  1. (Optional) Customize the login button text.
../_images/adfs_26_mattermost_login_button.PNG
  1. Click Save.
  2. (Optional) If you configured First Name Attribute and Last Name Attribute, go to System Console > General > Users and Teams and 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 > General > Sign-in Method > Switch to SAML SSO and sign in with your SAML credentials to complete the switch.

It is also recommended to post an announcement about how the migration will work to users.

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

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 will not update until they log in to the server.

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 > SAML and set Enable Synchronizing SAML Accounts With AD/LDAP to true.
  2. Go to System Console > AD/LDAP and set Enable Synchronization with AD/LDAP to true.
  3. 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, keep Enable sign-in with AD/LDAP as false.
  1. Set Syncronization Interval to specify how often Mattermost synchronizes SAML user accounts with AD/LDAP. The default setting is 60 minutes. If you want to synchronize immediately after disabling an account, use the “AD/LDAP Synchronize Now” button in System Console > AD/LDAP.
  2. To test Mattermost can successfully connect to your AD/LDAP server, click the AD/LDAP Test button.

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 in System Console > Configuration > Purge All Caches.
  3. Run AD/LDAP sync in System Console > AD/LDAP > AD/LDAP Synchronize Now.
  4. Purge all caches again in Mattermost in System Console > Configuration > Purge All Caches, which 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.

Technical description of SAML synchronization with AD/LDAP

When enabled, SAML synchronization with AD/LDAP occurs in phases:

  1. Get all the current LDAP users from the Mattermost database who have Users.AuthService set to ldap. This is a SQL query issued against the Mattermost database: SELECT * FROM Users WHERE AuthService = 'ldap'.
  2. Get all the current SAML users from the Mattermost database who have Users.AuthService set to saml. This is a SQL query issued against the Mattermost database: SELECT * FROM Users WHERE AuthService = 'saml'.
  3. Get all the current LDAP users from the LDAP server as defined by LdapSettings.UserFilter. This is an LDAP query issued against the LDAP server. Users are retrieved in batches as defined by LdapSettings.MaxPageSize.
  4. Update LDAP attributes. For each existing Mattermost user retrieved in step 1, attempt to find a match against the list of LDAP users from step 3. To find matches, Users.AuthData field of the Mattermost user is compared against the LdapSettings.IdAttribute LDAP setting.
  • If any attribute of the user has changed, that attribute is copied from the LDAP server and the user is marked as updated.
  • If the corresponding LdapSettings.IdAttribute is not found, the user is assumed to be deleted from the LDAP server, and deactivated from Mattermost by setting the Users.DeleteAt field to a valid timestamp.
  1. Update SAML attributes. For each existing Mattermost user retrieved in step 2, attempt to find a match against the list of LDAP users from step 3. To find matches, SamlSettings.Email is compared against the LdapSettings.EmailAttribute LDAP setting.
  • If any attribute of the user has changed, that attribute is copied from the LDAP server and the user is marked as updated.
  • If the corresponding LdapSettings.EmailAttribute is not found, the user is assumed to be deleted from the LDAP server, and deactivated from Mattermost by setting the Users.DeleteAt field to a valid timestamp.

Override SAML Data with AD/LDAP Data

Alternatively, you can choose to override SAML bind data with AD/LDAP information. For more infomation 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 on System Console > SAML > Id Attribute.
  2. Set System Console > SAML > Override SAML bind data with AD/LDAP information to true.
  3. Set System Console > SAML > Enable Synchronizing SAML Accounts With AD/LDAP to true.
  4. Run AD/LDAP sync in System Console > AD/LDAP > AD/LDAP Synchronize Now.

Troubleshooting

The following are troubleshooting suggestions on common error messages and issues.

  1. System Administrator locks themselves out of the system
If the System Administrator is locked out of the system during SAML configuration process, they can set an existing account to System Administrator using a command line tool.
  1. Received error message: An account with that username already exists. Please contact your Administrator.

This usually means an existing account has another authentication method enabled. If so, the user should sign in using that method (such as email and password), then change their sign-in method to SAML via Account Settings > Security > Sign-in method.

This error message can also be received if the Username Attribute of their SAML credentials doesn’t match the username of their Mattermost account. If so, the user can update the attribute at their identity provider (for instance, back to the old value if it had been previously updated).

  1. Received error message: An account with that email already exists. Please contact your Administrator.

This usually means an existing account has another authentication method enabled. If so, the user should sign in using that method (such as email and password), then change their sign-in method to SAML via Account Settings > Security > Sign-in method.

This error message can also be received if the Email Attribute of their SAML credentials doesn’t match the email address of their Mattermost account. If so, the user can update the attribute at their identity provider (for instance, back to the old value if it had been previously updated).

  1. Received error message: SAML login was unsuccessful because one of the attributes is incorrect. Please contact your System Administrator.
Confirm all attributes, including Email Attribute and Username Attribute, are correct in both the Identity Provider configuration and in System Console > SAML.
  1. Unable to switch to SAML authentication successfully

First, ensure you have installed the XML Security Library on your Mattermost instance and that it is available in your PATH.

Second, ensure you have completed each step of the SAML configuration.

If you are still having trouble with configuration, feel free to post in our Troubleshooting forum and we’ll be happy to help with issues during setup.