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99 lines
4.1 KiB
ReStructuredText
99 lines
4.1 KiB
ReStructuredText
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ACME
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====
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Synapse v1.0 requires that federation TLS certificates are verifiable by a
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trusted root CA. If you do not already have a valid certificate for your domain, the easiest
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way to get one is with Synapse's new ACME support, which will use the ACME
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protocol to provision a certificate automatically. By default, certificates
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will be obtained from the publicly trusted CA Let's Encrypt.
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For a sample configuration, please inspect the new ACME section in the example
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generated config by running the ``generate-config`` executable. For example::
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~/synapse/env3/bin/generate-config
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You will need to provide Let's Encrypt (or another ACME provider) access to
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your Synapse ACME challenge responder on port 80, at the domain of your
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homeserver. This requires you to either change the port of the ACME listener
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provided by Synapse to a high port and reverse proxy to it, or use a tool
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like ``authbind`` to allow Synapse to listen on port 80 without root access.
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(Do not run Synapse with root permissions!) Detailed instructions are
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available under "ACME setup" below.
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If you are already using self-signed certificates, you will need to back up
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or delete them (files ``example.com.tls.crt`` and ``example.com.tls.key`` in
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Synapse's root directory), Synapse's ACME implementation will not overwrite
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them.
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You may wish to use alternate methods such as Certbot to obtain a certificate
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from Let's Encrypt, depending on your server configuration. Of course, if you
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already have a valid certificate for your homeserver's domain, that can be
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placed in Synapse's config directory without the need for any ACME setup.
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ACME setup
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----------
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Synapse v1.0 will require valid TLS certificates for communication between servers
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(port ``8448`` by default) in addition to those that are client-facing (port
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``443``). In the case that your `server_name` config variable is the same as
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the hostname that the client connects to, then the same certificate can be
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used between client and federation ports without issue. Synapse v0.99.0+
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will provision server-to-server certificates automatically for you for
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free through `Let's Encrypt
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<https://letsencrypt.org/>`_ if you tell it to.
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In order for Synapse to complete the ACME challenge to provision a
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certificate, it needs access to port 80. Typically listening on port 80 is
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only granted to applications running as root. There are thus two solutions to
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this problem.
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**Using a reverse proxy**
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A reverse proxy such as Apache or nginx allows a single process (the web
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server) to listen on port 80 and proxy traffic to the appropriate program
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running on your server. It is the recommended method for setting up ACME as
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it allows you to use your existing webserver while also allowing Synapse to
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provision certificates as needed.
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For nginx users, add the following line to your existing ``server`` block::
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location /.well-known/acme-challenge {
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proxy_pass http://localhost:8009/;
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}
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For Apache, add the following to your existing webserver config::
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ProxyPass /.well-known/acme-challenge http://localhost:8009/.well-known/acme-challenge
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Make sure to restart/reload your webserver after making changes.
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**Authbind**
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``authbind`` allows a program which does not run as root to bind to
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low-numbered ports in a controlled way. The setup is simpler, but requires a
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webserver not to already be running on port 80. **This includes every time
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Synapse renews a certificate**, which may be cumbersome if you usually run a
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web server on port 80. Nevertheless, if you're sure port 80 is not being used
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for any other purpose then all that is necessary is the following:
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Install ``authbind``. For example, on Debian/Ubuntu::
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sudo apt-get install authbind
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Allow ``authbind`` to bind port 80::
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sudo touch /etc/authbind/byport/80
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sudo chmod 777 /etc/authbind/byport/80
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When Synapse is started, use the following syntax::
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authbind --deep <synapse start command>
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Finally, once Synapse's is able to listen on port 80 for ACME challenge
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requests, it must be told to perform ACME provisioning by setting ``enabled``
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to true under the ``acme`` section in ``homeserver.yaml``::
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acme:
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enabled: true
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