Enhance SAML configuration instructions for Mattermost

source/administration-guide/onboard/sso-saml-entraid.rst

@@ -20,47 +20,115 @@ Prerequisites
 * A Microsoft Entra tenant containing applicable user data.
 * A verified custom domain for your tenant. See Microsoft's `Add your custom domain name to your tenant <https://learn.microsoft.com/en-us/entra/fundamentals/add-custom-domain>`__ documentation for details.
 * A Microsoft Entra ID P1 or P2 license.
+* An account with at least the **Application Administrator** role in your Entra tenant.
 
 Set up an enterprise app for Mattermost SSO in Entra ID
 --------------------------------------------------------
 
-1. Log into the Microsoft Azure portal and select the **Microsoft Entra ID** service.
-2. In the left menu, select **Manage > Enterprise applications**.
-3. Select the **New application** button.
-4. In the **Search application** field, search for **Microsoft Entra SAML Toolkit** and select **Microsoft Entra SAML Toolkit**.
-5. In the **Name** field, enter **Mattermost SAML** then select the **Create** button.
-6. In the **Mattermost SAML** enterprise application settings, select **Manage > Users and Groups** to assign users and/or groups to the application **or** select **Manage > Properties** then set **Assignment required?** to **No** then select **Save**.
-7. In the **Mattermost SAML** enterprise application settings, select **Manage > Single sign-on** then select **SAML** under **Select a single sign-on method**.
-8. Select **Edit** in the **Basic SAML Configuration section** then set the below fields then select **Save**:
+1. Sign in to the `Microsoft Entra admin center <https://entra.microsoft.com>`__ with an account that has at least the **Application Administrator** role.
+2. In the left navigation menu, select **Entra ID > Enterprise applications**.
+3. Select **+ New application**.
+4. Select **+ Create your own application**.
+5. In the **What's the name of your app?** field, enter **Mattermost**.
+6. Under **What are you looking to do with your application?**, select **Integrate any other application you don't find in the gallery (Non-gallery)**.
+7. Select **Create**. Entra provisions the application; this may take a few seconds.
+8. In the **Mattermost** enterprise application settings, select **Manage > Users and groups**, then assign the approved users and/or groups that should have access to Mattermost.
 
-  - **Identity (Entity ID)**: ``https://<your-mattermost-url>``
-  - **Reply URL (Assertion Consumer Service URL)**: ``https://<your-mattermost-url>/login/sso/saml``
-  - **Sign on URL**: ``https://<your-mattermost-url>/login``
+   .. warning::
 
-9. Select **Edit** in the **Attributes & Claims** section then set the below attributes:
+      Alternatively, you can select **Manage > Properties**, set **Assignment required?** to **No**, then select **Save**. This grants Mattermost access to **all users in your Entra tenant** — evaluate whether this aligns with your organization's access control requirements before proceeding.
+9. In the **Mattermost** enterprise application settings, select **Manage > Single sign-on**, then select **SAML** under **Select a single sign-on method**.
+10. Select **Edit** in the **Basic SAML Configuration** section, then set the fields below and select **Save**:
 
-  a. Set the the **Unique User Identifier (Name ID)** required claim **Name identifier format** and **Source attribute** values as required for your environment. Setting the **Source attribute** to an immutable value such as ``user.objectid`` is recommended.
-  b. Edit claim names **and namespaces** under **Additional claims** to match SAML attribute settings you wish to set in Mattermost. Configurable settings are Email, Username, Id, Guest, Admin, First Name, Last Name, Nickname, Position, and Preferred Language.
+   - **Identifier (Entity ID)**: ``https://<your-mattermost-url>``
+   - **Reply URL (Assertion Consumer Service URL)**: ``https://<your-mattermost-url>/login/sso/saml``
+   - **Sign on URL**: ``https://<your-mattermost-url>/login``
 
-.. important::
+11. Select **Edit** in the **Attributes & Claims** section, then configure the required claim and additional claims as described below.
 
-  Mattermost matches each attribute by its **full claim name**, including the namespace, exactly as it appears in the SAML assertion. By default, Entra ID emits its built-in claims under the namespace ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/`` — so the claim that appears in the **Claim name** column as ``emailaddress`` is actually sent in the assertion as ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress``.
+    **How Entra claims map to Mattermost**
 
-  This means the value you enter in each Mattermost attribute field (step 15 of **Configure SAML Sign-On for Mattermost**, below) must be the **fully-qualified** claim name. Entering only the short name (for example, ``email`` or ``name``) will **not** match, and login will fail with an error such as ``SAML login was unsuccessful because one of the attributes is incorrect... <attribute> attribute is missing``.
+    The SAML assertion Entra sends to Mattermost contains a set of *claims* — name/value pairs describing the user. Mattermost reads these claims based on the attribute names you configure in **System Console > Authentication > SAML 2.0 > Attributes** (for example, **Email Attribute**, **Username Attribute**, **First Name Attribute**).
 
-  You have two options:
+    The **Claim name** you set in Entra must match the value you enter in the corresponding Mattermost attribute field exactly, character for character. The **Value** (also called **Source attribute**) tells Entra which user property to send — for example, ``user.mail`` sends the user's email address.
 
-  - **Clear the namespace** on each claim in Entra ID under **Additional claims** so the claim name becomes the short value (for example, ``email``), then enter that same short value in Mattermost; **or**
-  - **Leave the default namespace** in Entra ID and enter the fully-qualified claim name in Mattermost (for example, ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress``).
+    a. **Required claim — Unique User Identifier (Name ID)**
 
-  Whichever option you choose, the value in Mattermost must match the assertion **character-for-character**. If a login fails, the safest way to confirm the exact claim names being sent is to capture and decode the SAML response from the browser (for example, with the `SAML-tracer <https://addons.mozilla.org/firefox/addon/saml-tracer/>`__ browser extension) and read the ``Name`` attribute of each ``<Attribute>`` element.
+       Set the **Name identifier format** and **Source attribute** values as required for your environment. The Name ID is part of the SAML assertion, but Mattermost account binding is controlled by the **Id Attribute (SAML)** setting if you configure it, or by email otherwise. If you want immutable user binding in Mattermost, add a separate ``Id`` claim under **Additional claims** and set its **Value** (source attribute) to an immutable Entra attribute such as ``user.objectid``. ``user.userprincipalname`` is also a common choice for Name ID when a human-readable identifier is preferred, with the trade-off that renames in Entra can orphan the corresponding Mattermost account if you rely on it for identity matching.
 
-10. Select **Edit** in the **SAML Certificates** section. Select **Sign SAML response and assertion** for **Signing Option** and **SHA-256** for **Signing Algorithm** then select **Save**.
-11. Select the **Certificate (Base64)** Download link in the **SAML Certificates** section. This is the **Identity Provider Public Certificate** to be uploaded to Mattermost.
-12. In the **Mattermost SAML** enterprise application settings, select **Security > Token encryption**. Select **Import Certificate** to import the Service Provider certificate. If you used the Bash script referenced in the **Before you begin** section, this is the ``mattermost-x509.crt`` file. The Import dialog says to upload a certificate with a file extension ``.cer``, but ``.crt`` files are also accepted. Upload the file then select **Add**.
-13. Select the ``...`` to the right of the imported certificate details, select **Activate token encryption certificate**, then select **Yes** to activate.
-14. On the **Home** page for **Microsoft Entra ID**, select the **Overview** link in the left navigation menu and copy the **Tenant ID** value. The **Tenant ID** will be used in Mattermost **SAML 2.0** URL settings.
-15. In the left navigation menu, select **Manage > Enterprise applications**. Select the **Mattermost SAML** application then copy the **Application ID**. The **Application ID** will be used in the **Identity Provider Metadata URL** setting in the Mattermost **SAML 2.0** settings. 
+    b. **Additional claims**
+
+       By default, Entra populates this section with four claims using the ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/...`` namespace. These work, but we recommend replacing them with short, readable names that match the attribute fields in Mattermost. To edit a claim, select it, update the **Name** field (and clear the **Namespace** field), then save.
+
+       .. important::
+
+          Mattermost matches each attribute by its **full claim name**, including the namespace, exactly as it appears in the SAML assertion. By default, Entra emits its built-in claims under the namespace ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/`` — so the claim that appears in the **Claim name** column as ``emailaddress`` is actually sent in the assertion as ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress``.
+
+          Entering only the short name (for example, ``email`` or ``name``) in a Mattermost attribute field will **not** match, and login will fail with an error such as ``SAML login was unsuccessful because one of the attributes is incorrect... <attribute> attribute is missing``.
+
+          You have two options:
+
+          - **Clear the namespace** on each claim in Entra ID (the approach shown in the table below) so the claim name becomes the short value (for example, ``email``), then enter that same short value in Mattermost; **or**
+          - **Leave the default namespace** in Entra ID and enter the fully-qualified claim name in Mattermost (for example, ``http://schemas.xmlsoap.org/ws/2005/05/identity/claims/emailaddress``).
+
+          If a login fails, the safest way to confirm the exact claim names being sent is to capture and decode the SAML response from the browser (for example, with the `SAML-tracer <https://addons.mozilla.org/firefox/addon/saml-tracer/>`__ browser extension) and read the ``Name`` attribute of each ``<Attribute>`` element.
+
+       The following claim configuration covers a typical Mattermost setup (using the clear-namespace option):
+
+       .. list-table::
+          :header-rows: 1
+          :widths: 30 25 45
+
+          * - Mattermost attribute field
+            - Entra claim name
+            - Entra source attribute
+          * - Email Attribute
+            - ``email``
+            - ``user.mail``
+          * - Username Attribute
+            - ``username``
+            - ``user.mailnickname``
+          * - First Name Attribute
+            - ``firstname``
+            - ``user.givenname``
+          * - Last Name Attribute
+            - ``lastname``
+            - ``user.surname``
+          * - Position Attribute
+            - ``position``
+            - ``user.jobtitle``
+
+       .. note::
+          Use ``user.mailnickname`` rather than ``user.userprincipalname`` as the source for the username claim. The user principal name is typically formatted as an email address (``user@domain.com``), but Mattermost usernames cannot contain the ``@`` character, so SAML logins using ``user.userprincipalname`` will fail. The mail nickname is the local part of the email address (the portion before ``@``) and maps cleanly to a valid Mattermost username.
+
+          If your organization doesn't populate ``mailnickname`` consistently, another option is a custom Entra attribute or a transformation that strips the domain from the UPN.
+
+       After editing, your **Attributes & Claims** page should look similar to the screenshot below:
+
+       .. image:: ../../images/entra-attributes-and-claims.png
+          :alt: Entra Attributes & Claims page showing simplified claim names
+          :width: 100%
+
+       The **Guest**, **Admin**, **Nickname**, and **Preferred Language** attributes are also configurable in Mattermost if you want to drive them from Entra. Use the same pattern: pick a short claim name in Entra, set its source attribute, and enter the matching claim name in the corresponding Mattermost attribute field.
+
+12. Select **Edit** in the **SAML Certificates** section. Select **Sign SAML response and assertion** for **Signing Option** and **SHA-256** for **Signing Algorithm**, then select **Save**.
+13. Select the **Certificate (Base64)** Download link in the **SAML Certificates** section. This is the **Identity Provider Public Certificate** to be uploaded to Mattermost.
+14. In the **Mattermost** enterprise application settings, select **Security > Token encryption**. Select **Import Certificate** to import the Service Provider certificate. If you used the Bash script referenced in the **Before you begin** section, this is the ``mattermost-x509.crt`` file. The Import dialog says to upload a certificate with a file extension ``.cer``, but ``.crt`` files are also accepted. Upload the file then select **Add**.
+15. Select the ``...`` to the right of the imported certificate details, select **Activate token encryption certificate**, then select **Yes** to activate.
+16. Copy the **Tenant ID** for use in the Mattermost **SAML 2.0** URL settings.
+
+    .. note::
+       Entra exposes three different GUIDs during this setup, and it's easy to confuse them. The **Tenant ID** identifies your entire Entra directory, while the **Application ID** and **Object ID** (visible on the enterprise application's **Properties** page) identify the Mattermost SAML application within that directory. Mattermost uses the Tenant ID and Application ID; the Object ID is not used.
+
+    To find the Tenant ID, select **Entra ID** from the admin center home, then locate the **Tenant ID** value in the **Basic information** panel on the **Overview** page.
+
+    .. image:: ../../images/entra-tenant-id.png
+       :alt: Where to find the Tenant ID
+       :width: 100%
+
+17. Copy the **Application ID** for use in the **Identity Provider Metadata URL** setting in the Mattermost **SAML 2.0** settings.
+
+    To find the Application ID, select **Entra ID > Enterprise applications** from the left navigation menu, select the **Mattermost** application, then copy the **Application ID** from the **Properties** page (shown alongside the Object ID, which is not needed).
 
 Configure SAML Sign-On for Mattermost
 --------------------------------------
@@ -71,25 +139,25 @@ Configure SAML Sign-On for Mattermost
 4. Select **Get SAML Metadata From IdP** to verify that the SAML metadata can be retrieved successfully.
 5. Set **SAML SSO URL**: ``https://login.microsoftonline.com/<your-tenant-id>/saml2``
 6. Set **Identity Provider Issuer URL** (trailing slash is required): ``https://sts.windows.net/<your-tenant-id>/``
-7. Choose the **Identity Provider Public Certificate** file from step 11 of **Set up an enterprise app for Mattermost SSO in Entra ID** then upload.
+7. Choose the **Identity Provider Public Certificate** file from step 13 of **Set up an enterprise app for Mattermost SSO in Entra ID** then upload.
 8. Set **Verify Signature** to **True**.
 9. Set **Service Provider Login URL**: ``https://<your-mattermost-url>/login/sso/saml``
 10. Set **Service Provider Identifier**: ``https://<your-mattermost-url>``
-11. Set **Enable Encryption** to **True**
-12. Choose your **Service Provider Private Key** file then upload.  If you used the Bash script referenced in the **Before you begin** section, this is the ``mattermost-x509.key`` file.
+11. Set **Enable Encryption** to **True**.
+12. Choose your **Service Provider Private Key** file then upload. If you used the Bash script referenced in the **Before you begin** section, this is the ``mattermost-x509.key`` file.
 13. Choose your **Service Provider Public Certificate** then upload. If you used the Bash script referenced in the **Before you begin** section, this is the ``mattermost-x509.crt`` file.
-14. Set **Sign Request** to suit your environment. The **Signature Algorithm** must match the algorithm set in Entra ID (**RSAwithSHA256** is recommended). 
+14. Set **Sign Request** to **True** if you want Mattermost to sign outbound AuthnRequests sent to Entra ID — this is distinct from Entra signing its SAML responses and assertions (configured in step 12 of the Entra setup). If enabled, set **Signature Algorithm** to **RSAwithSHA256** (Entra ID requires RSA-SHA256 for signed requests) and upload Mattermost's public certificate to Entra ID for request verification: in the enterprise application, select **SAML Certificates**, then upload the ``mattermost-x509.crt`` file under **Verification certificates**.
 
 .. note:: 
 
   The **Test single sign-on with Mattermost SAML** tool in Microsoft Entra ID does not sign the request even if **Sign Request** is set to **True** in Mattermost. Depending on your security settings and key length, the Entra ID testing tool may successfully sign in while an actual sign in request from your Mattermost login page results in the error **AADSTS90015: Requested query string is too long.** since Entra ID handles the initial request with an HTTP GET redirect rather than HTTP POST.
 
-15. Set attribute settings to match attributes configured in step 9 of the **Set up an enterprise app for Mattermost SSO in Entra ID** section. Each value must match the **full claim name** sent in the assertion, including the namespace, exactly. See the **important** note under step 9 for details and a common failure mode.
+15. Set attribute settings to match the attributes configured in step 11 of the **Set up an enterprise app for Mattermost SSO in Entra ID** section. Each value must match the **full claim name** sent in the assertion, including the namespace, exactly. See the **important** note under step 11 for details and a common failure mode.
 16. Set the **Login Button Text** to suit your environment.
 17. Select the **Save** button.
 
 .. include:: sso-saml-ldapsync.rst
 	:start-after: :nosearch:
 
 .. include:: sso-saml-faq.rst
-	:start-after: :nosearch:
+	:start-after: :nosearch: