Remove redundant code to reload tls cert (#10054)

we don't need to reload the tls cert if we don't have any tls listeners.

Follow-up to #9280.

changelog.d/10054.misc

@@ -0,0 +1 @@
+Remove some dead code regarding TLS certificate handling.

synapse/app/_base.py

@@ -261,13 +261,10 @@ def refresh_certificate(hs):
     Refresh the TLS certificates that Synapse is using by re-reading them from
     disk and updating the TLS context factories to use them.
     """
-
     if not hs.config.has_tls_listener():
-        # attempt to reload the certs for the good of the tls_fingerprints
-        hs.config.read_certificate_from_disk(require_cert_and_key=False)
         return
 
-    hs.config.read_certificate_from_disk(require_cert_and_key=True)
+    hs.config.read_certificate_from_disk()
     hs.tls_server_context_factory = context_factory.ServerContextFactory(hs.config)
 
     if hs._listening_services:

synapse/config/tls.py

@@ -215,28 +215,12 @@ class TlsConfig(Config):
         days_remaining = (expires_on - now).days
         return days_remaining
 
-    def read_certificate_from_disk(self, require_cert_and_key: bool):
+    def read_certificate_from_disk(self):
         """
         Read the certificates and private key from disk.
-
-        Args:
-            require_cert_and_key: set to True to throw an error if the certificate
-                and key file are not given
         """
-        if require_cert_and_key:
-            self.tls_private_key = self.read_tls_private_key()
-            self.tls_certificate = self.read_tls_certificate()
-        elif self.tls_certificate_file:
-            # we only need the certificate for the tls_fingerprints. Reload it if we
-            # can, but it's not a fatal error if we can't.
-            try:
-                self.tls_certificate = self.read_tls_certificate()
-            except Exception as e:
-                logger.info(
-                    "Unable to read TLS certificate (%s). Ignoring as no "
-                    "tls listeners enabled.",
-                    e,
-                )
+        self.tls_private_key = self.read_tls_private_key()
+        self.tls_certificate = self.read_tls_certificate()
 
     def generate_config_section(
         self,

tests/config/test_tls.py

@@ -74,12 +74,11 @@ s4niecZKPBizL6aucT59CsunNmmb5Glq8rlAcU+1ZTZZzGYqVYhF6axB9Qg=
 
         config = {
             "tls_certificate_path": os.path.join(config_dir, "cert.pem"),
-            "tls_fingerprints": [],
         }
 
         t = TestConfig()
         t.read_config(config, config_dir_path="", data_dir_path="")
-        t.read_certificate_from_disk(require_cert_and_key=False)
+        t.read_tls_certificate()
 
         warnings = self.flushWarnings()
         self.assertEqual(len(warnings), 1)