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))

7 files changed, 52 insertions, 26 deletions

diff --git a/synapse/config/cas.py b/synapse/config/cas.py
index daea848d24..dbf5085965 100644
--- a/synapse/config/cas.py
+++ b/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(
diff --git a/synapse/config/emailconfig.py b/synapse/config/emailconfig.py
index 6a487afd34..d4328c46b9 100644
--- a/synapse/config/emailconfig.py
+++ b/synapse/config/emailconfig.py
@@ -166,6 +166,11 @@ class EmailConfig(Config):
             if not self.email_notif_from:
                 missing.append("email.notif_from")
 
+            # public_baseurl is required to build password reset and validation links that
+            # will be emailed to users
+            if config.get("public_baseurl") is None:
+                missing.append("public_baseurl")
+
             if missing:
                 raise ConfigError(
                     MISSING_PASSWORD_RESET_CONFIG_ERROR % (", ".join(missing),)
@@ -264,6 +269,9 @@ class EmailConfig(Config):
             if not self.email_notif_from:
                 missing.append("email.notif_from")
 
+            if config.get("public_baseurl") is None:
+                missing.append("public_baseurl")
+
             if missing:
                 raise ConfigError(
                     "email.enable_notifs is True but required keys are missing: %s"
diff --git a/synapse/config/oidc_config.py b/synapse/config/oidc_config.py
index 9d8196d8c3..d081f36fa5 100644
--- a/synapse/config/oidc_config.py
+++ b/synapse/config/oidc_config.py
@@ -53,7 +53,10 @@ class OIDCConfig(Config):
                     "Multiple OIDC providers have the idp_id %r." % idp_id
                 )
 
-        self.oidc_callback_url = self.public_baseurl + "_synapse/client/oidc/callback"
+        public_baseurl = self.public_baseurl
+        if public_baseurl is None:
+            raise ConfigError("oidc_config requires a public_baseurl to be set")
+        self.oidc_callback_url = public_baseurl + "_synapse/client/oidc/callback"
 
     @property
     def oidc_enabled(self) -> bool:
diff --git a/synapse/config/registration.py b/synapse/config/registration.py
index afb3e0b2a1..ead007ba5a 100644
--- a/synapse/config/registration.py
+++ b/synapse/config/registration.py
@@ -49,6 +49,10 @@ class AccountValidityConfig(Config):
 
             self.startup_job_max_delta = self.period * 10.0 / 100.0
 
+        if self.renew_by_email_enabled:
+            if "public_baseurl" not in synapse_config:
+                raise ConfigError("Can't send renewal emails without 'public_baseurl'")
+
         template_dir = config.get("template_dir")
 
         if not template_dir:
@@ -105,6 +109,13 @@ class RegistrationConfig(Config):
         account_threepid_delegates = config.get("account_threepid_delegates") or {}
         self.account_threepid_delegate_email = account_threepid_delegates.get("email")
         self.account_threepid_delegate_msisdn = account_threepid_delegates.get("msisdn")
+        if self.account_threepid_delegate_msisdn and not self.public_baseurl:
+            raise ConfigError(
+                "The configuration option `public_baseurl` is required if "
+                "`account_threepid_delegate.msisdn` is set, such that "
+                "clients know where to submit validation tokens to. Please "
+                "configure `public_baseurl`."
+            )
 
         self.default_identity_server = config.get("default_identity_server")
         self.allow_guest_access = config.get("allow_guest_access", False)
@@ -227,9 +238,8 @@ class RegistrationConfig(Config):
           # send an email to the account's email address with a renewal link. By
           # default, no such emails are sent.
           #
-          # If you enable this setting, you will also need to fill out the 'email'
-          # configuration section. You should also check that 'public_baseurl' is set
-          # correctly.
+          # If you enable this setting, you will also need to fill out the 'email' and
+          # 'public_baseurl' configuration sections.
           #
           #renew_at: 1w
 
@@ -320,7 +330,8 @@ class RegistrationConfig(Config):
         # The identity server which we suggest that clients should use when users log
         # in on this server.
         #
-        # (By default, no suggestion is made, so it is left up to the client.)
+        # (By default, no suggestion is made, so it is left up to the client.
+        # This setting is ignored unless public_baseurl is also set.)
         #
         #default_identity_server: https://matrix.org
 
@@ -345,6 +356,8 @@ class RegistrationConfig(Config):
         # by the Matrix Identity Service API specification:
         # https://matrix.org/docs/spec/identity_service/latest
         #
+        # If a delegate is specified, the config option public_baseurl must also be filled out.
+        #
         account_threepid_delegates:
             #email: https://example.com     # Delegate email sending to example.com
             #msisdn: http://localhost:8090  # Delegate SMS sending to this local process
diff --git a/synapse/config/saml2_config.py b/synapse/config/saml2_config.py
index 1820614bc0..4b494f217f 100644
--- a/synapse/config/saml2_config.py
+++ b/synapse/config/saml2_config.py
@@ -188,6 +188,8 @@ class SAML2Config(Config):
         import saml2
 
         public_baseurl = self.public_baseurl
+        if public_baseurl is None:
+            raise ConfigError("saml2_config requires a public_baseurl to be set")
 
         if self.saml2_grandfathered_mxid_source_attribute:
             optional_attributes.add(self.saml2_grandfathered_mxid_source_attribute)
diff --git a/synapse/config/server.py b/synapse/config/server.py
index b5e82ba3d0..a635b8a7dc 100644
--- a/synapse/config/server.py
+++ b/synapse/config/server.py
@@ -230,11 +230,7 @@ class ServerConfig(Config):
         self.print_pidfile = config.get("print_pidfile")
         self.user_agent_suffix = config.get("user_agent_suffix")
         self.use_frozen_dicts = config.get("use_frozen_dicts", False)
-        self.public_baseurl = config.get("public_baseurl") or "https://%s/" % (
-            self.server_name,
-        )
-        if self.public_baseurl[-1] != "/":
-            self.public_baseurl += "/"
+        self.public_baseurl = config.get("public_baseurl")
 
         # Whether to enable user presence.
         self.use_presence = config.get("use_presence", True)
@@ -386,6 +382,9 @@ class ServerConfig(Config):
             config_path=("federation_ip_range_blacklist",),
         )
 
+        if self.public_baseurl is not None:
+            if self.public_baseurl[-1] != "/":
+                self.public_baseurl += "/"
         self.start_pushers = config.get("start_pushers", True)
 
         # (undocumented) option for torturing the worker-mode replication a bit,
@@ -813,10 +812,6 @@ class ServerConfig(Config):
         # Otherwise, it should be the URL to reach Synapse's client HTTP listener (see
         # 'listeners' below).
         #
-        # If this is left unset, it defaults to 'https://<server_name>/'. (Note that
-        # that will not work unless you configure Synapse or a reverse-proxy to listen
-        # on port 443.)
-        #
         #public_baseurl: https://example.com/
 
         # Set the soft limit on the number of file descriptors synapse can use
diff --git a/synapse/config/sso.py b/synapse/config/sso.py
index b94d3cd5e1..07ba217f89 100644
--- a/synapse/config/sso.py
+++ b/synapse/config/sso.py
@@ -81,8 +81,11 @@ class SSOConfig(Config):
         # gracefully to the client). This would make it pointless to ask the user for
         # confirmation, since the URL the confirmation page would be showing wouldn't be
         # the client's.
-        login_fallback_url = self.public_baseurl + "_matrix/static/client/login"
-        self.sso_client_whitelist.append(login_fallback_url)
+        # public_baseurl is an optional setting, so we only add the fallback's URL to the
+        # list if it's provided (because we can't figure out what that URL is otherwise).
+        if self.public_baseurl:
+            login_fallback_url = self.public_baseurl + "_matrix/static/client/login"
+            self.sso_client_whitelist.append(login_fallback_url)
 
     def generate_config_section(self, **kwargs):
         return """\
@@ -100,9 +103,9 @@ class SSOConfig(Config):
             # phishing attacks from evil.site. To avoid this, include a slash after the
             # hostname: "https://my.client/".
             #
-            # The login fallback page (used by clients that don't natively support the
-            # required login flows) is automatically whitelisted in addition to any URLs
-            # in this list.
+            # If public_baseurl is set, then the login fallback page (used by clients
+            # that don't natively support the required login flows) is whitelisted in
+            # addition to any URLs in this list.
             #
             # By default, this list is empty.
             #