Document using a certificate with a full chain (#4849)

INSTALL.md

@@ -375,9 +375,13 @@ To configure Synapse to expose an HTTPS port, you will need to edit
 * You will also need to uncomment the `tls_certificate_path` and
   `tls_private_key_path` lines under the `TLS` section. You can either
   point these settings at an existing certificate and key, or you can
-  enable Synapse's built-in ACME (Let's Encrypt) support.  Instructions
+  enable Synapse's built-in ACME (Let's Encrypt) support. Instructions
   for having Synapse automatically provision and renew federation
-  certificates through ACME can be found at [ACME.md](docs/ACME.md).
+  certificates through ACME can be found at [ACME.md](docs/ACME.md). If you
+  are using your own certificate, be sure to use a `.pem` file that includes
+  the full certificate chain including any intermediate certificates (for
+  instance, if using certbot, use `fullchain.pem` as your certificate, not
+  `cert.pem`).
 
 For those of you upgrading your TLS certificate in readiness for Synapse 1.0,
 please take a look at `our guide <docs/MSC1711_certificates_FAQ.md#configuring-certificates-for-compatibility-with-synapse-100>`_.

changelog.d/4849.misc

@@ -0,0 +1 @@
+Update install docs to explicitly state a full-chain (not just the top-level) TLS certificate must be provided to Synapse. This caused some people's Synapse ports to appear correct in a browser but still (rightfully so) upset the federation tester.

docs/sample_config.yaml

@@ -246,6 +246,11 @@ listeners:
 # See 'ACME support' below to enable auto-provisioning this certificate via
 # Let's Encrypt.
 #
+# If supplying your own, be sure to use a `.pem` file that includes the
+# full certificate chain including any intermediate certificates (for
+# instance, if using certbot, use `fullchain.pem` as your certificate,
+# not `cert.pem`).
+#
 #tls_certificate_path: "CONFDIR/SERVERNAME.tls.crt"
 
 # PEM-encoded private key for TLS

synapse/config/tls.py

@@ -181,6 +181,11 @@ class TlsConfig(Config):
         # See 'ACME support' below to enable auto-provisioning this certificate via
         # Let's Encrypt.
         #
+        # If supplying your own, be sure to use a `.pem` file that includes the
+        # full certificate chain including any intermediate certificates (for
+        # instance, if using certbot, use `fullchain.pem` as your certificate,
+        # not `cert.pem`).
+        #
         #tls_certificate_path: "%(tls_certificate_path)s"
 
         # PEM-encoded private key for TLS