title: Azure AD B2C Single Logout implementation
body: <p>I have 2 web aplications using AAD B2C single sign-on, the Mainsite.mydomain.com and support.provider.com (note that they are in different domains). My B2C has only local users, so no external IdP (e.g. Google, Facebooks, etc).</p>
  
  <p>Single sign-on works as expected and the individual logout from each website works as expected. </p>
  
  <p>Now I want Single Logout, i.e. when the users logout from the Mainsite I want them to be automatically logged out from the Support website, too. At logout from each app I do call the OIDC /logout endpoint to kill the B2C session as per the <a href="https://docs.microsoft.com/en-us/azure/active-directory-b2c/active-directory-b2c-reference-oidc#send-a-sign-out-request" rel="nofollow noreferrer">documentation</a>, but that isn't enough to logout from the other application.</p>
  
  <p>Reading the OIDC specs it seems there are 3 ways to have single-logoff, as described <a href="https://medium.com/@robert.broeckelmann/openid-connect-logout-eccc73df758f" rel="nofollow noreferrer">here</a>, but none of them seem to be available for B2C:</p>
  
  <ul>
  <li>Front-end channel (it would require registering a Logout URL for each
  app, but B2C apps don't have this attribute)</li>
  <li>Back-end channel (it would require registering a Logout URL for each
  app, but B2C apps don't have this attribute)</li>
  <li>Session Management (this requires a check_session_iframe URL, which
  is not provided by the B2C /.well-known endpoint)</li>
  </ul>
  
  <p>So it seems that none of the standard methods are supported by B2C, did anybody manage to figure out  how to do it?</p>
  
  <p><strong>Note</strong>: There's another similar SO question <a href="https://stackoverflow.com/questions/41187094/azure-ad-b2c-sign-out-a-user-from-all-sessions">here</a> but the single response doesn't actually answer the question and the comments to it show that others couldn't do single logoff either. Even more, my case is even simpler as I don't have any external IdP.</p>