Slack cloud application

1. Sign in to your Google Admin console.

   Sign in using an account with super administrator privileges (does not end in @gmail.com).

2. In the Admin console, go to Menu  AppsWeb and mobile apps.
3. Click Add appSearch for apps.
4. Enter Slack in the search field.
5. In the search results, hover over the Slack SAML app and click Select.
6. On the Google Identity Provider details page:
   •  Download the IDP metadata.
   • Copy the SSO URL and EntityID.
7. Click Continue.
8. On the Service provider details page, edit the ACS URL, replacing {your-team-name} with your Slack team name.

   Note: The same Entity ID can't be used by more than one SAML app. So, if the Entity ID https://slack.com has already been used by another Slack SAML app, set the Entity ID to https://your-team-name.slack.com instead

9. Check the Signed response box.
10. Click Continue.
11. On the Attribute mapping page, click Select field menu and map the following Google directory attributes to their corresponding Slack attributes:
     

    Google directory attribute	Slack attribute
    Basic Information > Primary Email	User.Email (required)
    Basic Information > First Name	first_name
    Basic Information > Last Name	last_name

12. (Optional) To enter group names that are relevant for this app:

    1. For Group membership (optional), click Search for a group, enter one or more letters of the group name, and select the group name.
    2. Add additional groups as needed (maximum of 75 groups).
    3. For App attribute, enter the groups attribute name of the corresponding service provider.

    Regardless of how many group names you enter, the SAML response includes only groups that a user is a member of (directly or indirectly). For more information, go to About group membership mapping.

13. Click Finish.

1. Sign in to your Google Admin console.

   Sign in using an account with super administrator privileges (does not end in @gmail.com).

2. In the Admin console, go to Menu  AppsWeb and mobile apps.
3. Select Slack.
4. Click User access.

5. To turn a service on or off for everyone in your organization, click On for everyone or Off for everyone, and then click Save.

6. (Optional) To turn a service on or off for an organizational unit:

   1. At the left, select the organizational unit.
   2. To change the Service status, select On or Off.
   3. Choose one:
      • If the Service status is set to Inherited and you want to keep the updated setting, even if the parent setting changes, click Override.
      • If the Service status is set to Overridden, either click Inherit to revert to the same setting as its parent, or click Save to keep the new setting, even if the parent setting changes.
        Note: Learn more about organizational structure.
7. To turn on a service for a set of users across or within organizational units, select an access group. For details, go to Use groups to customize service access.
8. Ensure that your Slack user account email IDs match those in your Google domain.

Changes can take up to 24 hours but typically happen more quickly. Learn more

1. Sign in to Slack at https://your-team-name.slack.com/home with your organization's slack team owner or administrator account.
2. Click Settings & Permissions.
3. Click the Authentication tab.
4. Next to SAML authentication, click Configure.
5. Confirm your password.
6. In the Choose your SAML provider window, select Custom SAML 2.0 and then click Configure.
7. In the SAML 2.0 Endpoint (HTTP) field, paste the the SSO URL you copied in step 1.
8. In the Identity Provider Issuer field, paste the the Entity ID you copied in step 1.
9. In the Public Certificate field, paste the entire contents of the file you downloaded in step 1. This is an X.509 Certificate that’s required for SSO setup. You might need to rename the file extension to “.txt” so you can open the file with a text editor.
10. Under Advanced Options:
    1. If you set the Entity ID in your Slack SAML app to something other than https://slack.com, paste the Entity ID value into the Service Provider Issuer field.
    2. For Choose how the SAML response from your IDP is signed, check Responses Signed.
11. Under Settings, indicate how authentication should be applied to your team.
12. Click Save Configuration.

Slack supports both Identity Provider (IdP) initiated and Service Provider (SP) initiated SSO. Follow these steps to verify SSO in either mode:

IdP-initiated

1. Sign in to your Google Admin console.

   Sign in using an account with super administrator privileges (does not end in @gmail.com).

2. In the Admin console, go to Menu  AppsWeb and mobile apps.
3. Select Slack.
4. At the top left, click Test SAML login. 

   Slack should open in a separate tab. If it doesn’t, use the information in the resulting SAML error messages to update your IdP and SP settings as needed, then retest SAML login.

SP-initiated

1. Close all browser windows.
2. Open http://your-team-name.slack.com and attempt to sign in with SAML. You should be redirected to the Google sign-in page.
3. Enter your user name and password.

After your credentials are authenticated, you are redirected back to Slack.

As a super administrator, you can automatically provision users in the Slack application.