Allow reactivate a user without password

synapse/rest/admin/users.py

@@ -406,15 +406,6 @@ class UserRestServletV2(RestServlet):
                         target_user.to_string(), False, requester, by_admin=True
                     )
                 elif not deactivate and user["deactivated"]:
-                    if (
-                        "password" not in body
-                        and self.auth_handler.can_change_password()
-                    ):
-                        raise SynapseError(
-                            HTTPStatus.BAD_REQUEST,
-                            "Must provide a password to re-activate an account.",
-                        )
-
                     await self.deactivate_account_handler.activate_account(
                         target_user.to_string()
                     )

tests/rest/admin/test_user.py

@@ -2741,7 +2741,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         profile = self.get_success(self.store._get_user_in_directory(self.other_user))
         self.assertIsNone(profile)
 
-    def test_reactivate_user(self) -> None:
+    def test_reactivate_user_with_password(self) -> None:
         """
         Test reactivating another user.
         """
@@ -2749,16 +2749,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         # Deactivate the user.
         self._deactivate_user("@user:test")
 
-        # Attempt to reactivate the user (without a password).
-        channel = self.make_request(
-            "PUT",
-            self.url_other_user,
-            access_token=self.admin_user_tok,
-            content={"deactivated": False},
-        )
-        self.assertEqual(400, channel.code, msg=channel.json_body)
-
-        # Reactivate the user.
+        # Reactivate the user with password.
         channel = self.make_request(
             "PUT",
             self.url_other_user,
@@ -2773,6 +2764,30 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         # This key was removed intentionally. Ensure it is not accidentally re-included.
         self.assertNotIn("password_hash", channel.json_body)
 
+    def test_reactivate_user_without_password(self) -> None:
+        """
+        Test reactivating another user without a password.
+        This can be using some local users and some user with SSO (password = `null`).
+        """
+
+        # Deactivate the user.
+        self._deactivate_user("@user:test")
+
+        # Reactivate the user without a password.
+        channel = self.make_request(
+            "PUT",
+            self.url_other_user,
+            access_token=self.admin_user_tok,
+            content={"deactivated": False},
+        )
+        self.assertEqual(200, channel.code, msg=channel.json_body)
+        self.assertEqual("@user:test", channel.json_body["name"])
+        self.assertFalse(channel.json_body["deactivated"])
+        self._is_erased("@user:test", False)
+
+        # This key was removed intentionally. Ensure it is not accidentally re-included.
+        self.assertNotIn("password_hash", channel.json_body)
+
     @override_config({"password_config": {"localdb_enabled": False}})
     def test_reactivate_user_localdb_disabled(self) -> None:
         """
@@ -2782,7 +2797,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         # Deactivate the user.
         self._deactivate_user("@user:test")
 
-        # Reactivate the user with a password
+        # Reactivate the user with a password.
         channel = self.make_request(
             "PUT",
             self.url_other_user,
@@ -2816,7 +2831,7 @@ class UserRestTestCase(unittest.HomeserverTestCase):
         # Deactivate the user.
         self._deactivate_user("@user:test")
 
-        # Reactivate the user with a password
+        # Reactivate the user with a password.
         channel = self.make_request(
             "PUT",
             self.url_other_user,