auth: Report to mobile apps the availability of RemoteUserBackend.

This is necessary for mobile apps to do the right thing when only
RemoteUserBackend is enabled, namely, directly redirect to the
third-party SSO auth site as soon as the user enters the server URL
(no need to display a login form, since it'll be useless).

zerver/tests/test_auth_backends.py

@@ -1320,6 +1320,7 @@ class FetchAuthBackends(ZulipTestCase):
                     ('email', check_bool),
                     ('ldap', check_bool),
                     ('dev', check_bool),
+                    ('remoteuser', check_bool),
                     ('password', check_bool),
                 ])),
                 ('email_auth_enabled', check_bool),
@@ -1353,7 +1354,7 @@ class FetchAuthBackends(ZulipTestCase):
         data = result.json()
         self.assertEqual(set(data.keys()),
                          {'msg', 'password', 'github', 'google', 'email', 'ldap',
-                          'dev', 'result', 'zulip_version'})
+                          'dev', 'result', 'remoteuser', 'zulip_version'})
         for backend in set(data.keys()) - {'msg', 'result', 'zulip_version'}:
             self.assertTrue(isinstance(data[backend], bool))
 
@@ -1371,6 +1372,7 @@ class FetchAuthBackends(ZulipTestCase):
                 'dev': True,
                 'email': False,
                 'ldap': False,
+                'remoteuser': False,
                 'result': 'success',
                 'zulip_version': ZULIP_VERSION,
             })
@@ -1387,6 +1389,7 @@ class FetchAuthBackends(ZulipTestCase):
                     'google': True,
                     'email': False,
                     'ldap': False,
+                    'remoteuser': False,
                     'dev': True,
                     'result': 'success',
                     'zulip_version': ZULIP_VERSION,
@@ -1412,6 +1415,7 @@ class FetchAuthBackends(ZulipTestCase):
                     'google': False,
                     'email': False,
                     'ldap': False,
+                    'remoteuser': False,
                     'dev': True,
                     'result': 'success',
                     'zulip_version': ZULIP_VERSION,
@@ -1433,6 +1437,7 @@ class FetchAuthBackends(ZulipTestCase):
                     'github': False,
                     'google': False,
                     'email': False,
+                    'remoteuser': False,
                     'ldap': False,
                     'dev': True,
                     'result': 'success',

zerver/views/auth.py

@@ -35,7 +35,8 @@ from zerver.models import PreregistrationUser, UserProfile, remote_user_to_email
 from zerver.signals import email_on_new_login
 from zproject.backends import password_auth_enabled, dev_auth_enabled, \
     github_auth_enabled, google_auth_enabled, ldap_auth_enabled, \
-    ZulipLDAPConfigurationError, ZulipLDAPAuthBackend, email_auth_enabled
+    ZulipLDAPConfigurationError, ZulipLDAPAuthBackend, email_auth_enabled, \
+    remote_auth_enabled
 from version import ZULIP_VERSION
 
 import hashlib
@@ -698,6 +699,7 @@ def get_auth_backends_data(request: HttpRequest) -> Dict[str, Any]:
         "email": email_auth_enabled(realm),
         "github": github_auth_enabled(realm),
         "google": google_auth_enabled(realm),
+        "remoteuser": remote_auth_enabled(realm),
         "ldap": ldap_auth_enabled(realm),
     }
 

zproject/backends.py

@@ -63,6 +63,9 @@ def google_auth_enabled(realm: Optional[Realm]=None) -> bool:
 def github_auth_enabled(realm: Optional[Realm]=None) -> bool:
     return auth_enabled_helper(['GitHub'], realm)
 
+def remote_auth_enabled(realm: Optional[Realm]=None) -> bool:
+    return auth_enabled_helper(['RemoteUser'], realm)
+
 def any_oauth_backend_enabled(realm: Optional[Realm]=None) -> bool:
     """Used by the login page process to determine whether to show the
     'OR' for login with Google"""