Do not generate self-signed TLS certificates by default. (#4509)

changelog.d/4509.removal

@@ -0,0 +1 @@
+Synapse no longer generates self-signed TLS certificates when generating a configuration file.

synapse/config/tls.py

@@ -15,6 +15,7 @@
 
 import logging
 import os
+import warnings
 from datetime import datetime
 from hashlib import sha256
 
@@ -39,8 +40,8 @@ class TlsConfig(Config):
         self.acme_bind_addresses = acme_config.get("bind_addresses", ["127.0.0.1"])
         self.acme_reprovision_threshold = acme_config.get("reprovision_threshold", 30)
 
-        self.tls_certificate_file = os.path.abspath(config.get("tls_certificate_path"))
-        self.tls_private_key_file = os.path.abspath(config.get("tls_private_key_path"))
+        self.tls_certificate_file = self.abspath(config.get("tls_certificate_path"))
+        self.tls_private_key_file = self.abspath(config.get("tls_private_key_path"))
         self._original_tls_fingerprints = config["tls_fingerprints"]
         self.tls_fingerprints = list(self._original_tls_fingerprints)
         self.no_tls = config.get("no_tls", False)
@@ -94,6 +95,16 @@ class TlsConfig(Config):
         """
         self.tls_certificate = self.read_tls_certificate(self.tls_certificate_file)
 
+        # Check if it is self-signed, and issue a warning if so.
+        if self.tls_certificate.get_issuer() == self.tls_certificate.get_subject():
+            warnings.warn(
+                (
+                    "Self-signed TLS certificates will not be accepted by Synapse 1.0. "
+                    "Please either provide a valid certificate, or use Synapse's ACME "
+                    "support to provision one."
+                )
+            )
+
         if not self.no_tls:
             self.tls_private_key = self.read_tls_private_key(self.tls_private_key_file)
 
@@ -118,10 +129,11 @@ class TlsConfig(Config):
         return (
             """\
         # PEM encoded X509 certificate for TLS.
-        # You can replace the self-signed certificate that synapse
-        # autogenerates on launch with your own SSL certificate + key pair
-        # if you like.  Any required intermediary certificates can be
-        # appended after the primary certificate in hierarchical order.
+        # This certificate, as of Synapse 1.0, will need to be a valid
+        # and verifiable certificate, with a root that is available in
+        # the root store of other servers you wish to federate to. Any
+        # required intermediary certificates can be appended after the
+        # primary certificate in hierarchical order.
         tls_certificate_path: "%(tls_certificate_path)s"
 
         # PEM encoded private key for TLS
@@ -183,40 +195,3 @@ class TlsConfig(Config):
     def read_tls_private_key(self, private_key_path):
         private_key_pem = self.read_file(private_key_path, "tls_private_key")
         return crypto.load_privatekey(crypto.FILETYPE_PEM, private_key_pem)
-
-    def generate_files(self, config):
-        tls_certificate_path = config["tls_certificate_path"]
-        tls_private_key_path = config["tls_private_key_path"]
-
-        if not self.path_exists(tls_private_key_path):
-            with open(tls_private_key_path, "wb") as private_key_file:
-                tls_private_key = crypto.PKey()
-                tls_private_key.generate_key(crypto.TYPE_RSA, 2048)
-                private_key_pem = crypto.dump_privatekey(
-                    crypto.FILETYPE_PEM, tls_private_key
-                )
-                private_key_file.write(private_key_pem)
-        else:
-            with open(tls_private_key_path) as private_key_file:
-                private_key_pem = private_key_file.read()
-                tls_private_key = crypto.load_privatekey(
-                    crypto.FILETYPE_PEM, private_key_pem
-                )
-
-        if not self.path_exists(tls_certificate_path):
-            with open(tls_certificate_path, "wb") as certificate_file:
-                cert = crypto.X509()
-                subject = cert.get_subject()
-                subject.CN = config["server_name"]
-
-                cert.set_serial_number(1000)
-                cert.gmtime_adj_notBefore(0)
-                cert.gmtime_adj_notAfter(10 * 365 * 24 * 60 * 60)
-                cert.set_issuer(cert.get_subject())
-                cert.set_pubkey(tls_private_key)
-
-                cert.sign(tls_private_key, 'sha256')
-
-                cert_pem = crypto.dump_certificate(crypto.FILETYPE_PEM, cert)
-
-                certificate_file.write(cert_pem)

tests/config/test_generate.py

@@ -50,8 +50,6 @@ class ConfigGenerationTestCase(unittest.TestCase):
                     "homeserver.yaml",
                     "lemurs.win.log.config",
                     "lemurs.win.signing.key",
-                    "lemurs.win.tls.crt",
-                    "lemurs.win.tls.key",
                 ]
             ),
             set(os.listdir(self.dir)),

tests/config/test_tls.py

@@ -0,0 +1,75 @@
+# -*- coding: utf-8 -*-
+# Copyright 2019 New Vector Ltd
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#     http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import os
+
+from synapse.config.tls import TlsConfig
+
+from tests.unittest import TestCase
+
+
+class TLSConfigTests(TestCase):
+
+    def test_warn_self_signed(self):
+        """
+        Synapse will give a warning when it loads a self-signed certificate.
+        """
+        config_dir = self.mktemp()
+        os.mkdir(config_dir)
+        with open(os.path.join(config_dir, "cert.pem"), 'w') as f:
+            f.write("""-----BEGIN CERTIFICATE-----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=
+-----END CERTIFICATE-----""")
+
+        config = {
+            "tls_certificate_path": os.path.join(config_dir, "cert.pem"),
+            "no_tls": True,
+            "tls_fingerprints": []
+        }
+
+        t = TlsConfig()
+        t.read_config(config)
+        t.read_certificate_from_disk()
+
+        warnings = self.flushWarnings()
+        self.assertEqual(len(warnings), 1)
+        self.assertEqual(
+            warnings[0]["message"],
+            (
+                "Self-signed TLS certificates will not be accepted by "
+                "Synapse 1.0. Please either provide a valid certificate, "
+                "or use Synapse's ACME support to provision one."
+            )
+        )