Synapse 1.27.0rc2 (2021-02-11)

==============================
 
 Features
 --------
 
 - Further improvements to the user experience of registration via single sign-on. ([\#9297](https://github.com/matrix-org/synapse/issues/9297))
 
 Bugfixes
 --------
 
 - Fix ratelimiting introduced in v1.27.0rc1 for invites to respect the `ratelimit` flag on application services. ([\#9302](https://github.com/matrix-org/synapse/issues/9302))
 - Do not automatically calculate `public_baseurl` since it can be wrong in some situations. Reverts behaviour introduced in v1.26.0. ([\#9313](https://github.com/matrix-org/synapse/issues/9313))
 
 Improved Documentation
 ----------------------
 
 - Clarify the sample configuration for changes made to the template loading code. ([\#9310](https://github.com/matrix-org/synapse/issues/9310))
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Merge tag 'v1.27.0rc2' into develop

Synapse 1.27.0rc2 (2021-02-11)
==============================

Features
--------

- Further improvements to the user experience of registration via single sign-on. ([\#9297](https://github.com/matrix-org/synapse/issues/9297))

Bugfixes
--------

- Fix ratelimiting introduced in v1.27.0rc1 for invites to respect the `ratelimit` flag on application services. ([\#9302](https://github.com/matrix-org/synapse/issues/9302))
- Do not automatically calculate `public_baseurl` since it can be wrong in some situations. Reverts behaviour introduced in v1.26.0. ([\#9313](https://github.com/matrix-org/synapse/issues/9313))

Improved Documentation
----------------------

- Clarify the sample configuration for changes made to the template loading code. ([\#9310](https://github.com/matrix-org/synapse/issues/9310))

synapse/config/cas.py

@@ -17,7 +17,7 @@ from typing import Any, List
 
 from synapse.config.sso import SsoAttributeRequirement
 
-from ._base import Config
+from ._base import Config, ConfigError
 from ._util import validate_config
 
 
@@ -35,13 +35,15 @@ class CasConfig(Config):
 
         if self.cas_enabled:
             self.cas_server_url = cas_config["server_url"]
-            public_base_url = cas_config.get("service_url") or self.public_baseurl
-            if public_base_url[-1] != "/":
-                public_base_url += "/"
+
+            # The public baseurl is required because it is used by the redirect
+            # template.
+            public_baseurl = self.public_baseurl
+            if not public_baseurl:
+                raise ConfigError("cas_config requires a public_baseurl to be set")
+
             # TODO Update this to a _synapse URL.
-            self.cas_service_url = (
-                public_base_url + "_matrix/client/r0/login/cas/ticket"
-            )
+            self.cas_service_url = public_baseurl + "_matrix/client/r0/login/cas/ticket"
             self.cas_displayname_attribute = cas_config.get("displayname_attribute")
             required_attributes = cas_config.get("required_attributes") or {}
             self.cas_required_attributes = _parsed_required_attributes_def(