<chapter xmlns="http://docbook.org/ns/docbook"
         xmlns:xlink="http://www.w3.org/1999/xlink"
         xmlns:xi="http://www.w3.org/2001/XInclude"
         version="5.0"
         xml:id="module-services-matrix">
 <title>Matrix</title>
 <para>
  <link xlink:href="https://matrix.org/">Matrix</link> is an open standard for
  interoperable, decentralised, real-time communication over IP. It can be used
  to power Instant Messaging, VoIP/WebRTC signalling, Internet of Things
  communication - or anywhere you need a standard HTTP API for publishing and
  subscribing to data whilst tracking the conversation history.
 </para>
 <para>
  This chapter will show you how to set up your own, self-hosted Matrix
  homeserver using the Synapse reference homeserver, and how to serve your own
  copy of the Riot web client. See the
  <link xlink:href="https://matrix.org/docs/projects/try-matrix-now.html">Try
  Matrix Now!</link> overview page for links to Riot Apps for Android and iOS,
  desktop clients, as well as bridges to other networks and other projects
  around Matrix.
 </para>
 <section xml:id="module-services-matrix-synapse">
  <title>Synapse Homeserver</title>

  <para>
   <link xlink:href="https://github.com/matrix-org/synapse">Synapse</link> is
   the reference homeserver implementation of Matrix from the core development
   team at matrix.org. The following configuration example will set up a
   synapse server for the <literal>example.org</literal> domain, served from
   the host <literal>myhostname.example.org</literal>. For more information,
   please refer to the
   <link xlink:href="https://github.com/matrix-org/synapse#synapse-installation">
   installation instructions of Synapse </link>.
<programlisting>
let
  fqdn =
    let
      join = hostName: domain: hostName + optionalString (domain != null) ".${domain}";
    in join config.networking.hostName config.networking.domain;
in {
  networking = {
    hostName = "myhostname";
    domain = "example.org";
  };
  networking.firewall.allowedTCPPorts = [ 80 443 ];

  services.nginx = {
    enable = true;
    # only recommendedProxySettings and recommendedGzipSettings are strictly required,
    # but the rest make sense as well
    recommendedTlsSettings = true;
    recommendedOptimisation = true;
    recommendedGzipSettings = true;
    recommendedProxySettings = true;

    virtualHosts = {
      # This host section can be placed on a different host than the rest,
      # i.e. to delegate from the host being accessible as ${config.networking.domain}
      # to another host actually running the Matrix homeserver.
      "${config.networking.domain}" = {
        locations."= /.well-known/matrix/server".extraConfig =
          let
            # use 443 instead of the default 8448 port to unite
            # the client-server and server-server port for simplicity
            server = { "m.server" = "${fqdn}:443"; };
          in ''
            add_header Content-Type application/json;
            return 200 '${builtins.toJSON server}';
          '';
        locations."= /.well-known/matrix/client".extraConfig =
          let
            client = {
              "m.homeserver" =  { "base_url" = "https://${fqdn}"; };
              "m.identity_server" =  { "base_url" = "https://vector.im"; };
            };
          # ACAO required to allow riot-web on any URL to request this json file
          in ''
            add_header Content-Type application/json;
            add_header Access-Control-Allow-Origin *;
            return 200 '${builtins.toJSON client}';
          '';
      };

      # Reverse proxy for Matrix client-server and server-server communication
      ${fqdn} = {
        enableACME = true;
        forceSSL = true;

        # Or do a redirect instead of the 404, or whatever is appropriate for you.
        # But do not put a Matrix Web client here! See the Riot Web section below.
        locations."/".extraConfig = ''
          return 404;
        '';

        # forward all Matrix API calls to the synapse Matrix homeserver
        locations."/_matrix" = {
          proxyPass = "http://[::1]:8008/_matrix";
        };
      };
    };
  };
  services.matrix-synapse = {
    enable = true;
    server_name = config.networking.domain;
    listeners = [
      {
        port = 8008;
        bind_address = "::1";
        type = "http";
        tls = false;
        x_forwarded = true;
        resources = [
          { names = [ "client" "federation" ]; compress = false; }
        ];
      }
    ];
  };
};
</programlisting>
  </para>

  <para>
   If the <code>A</code> and <code>AAAA</code> DNS records on
   <literal>example.org</literal> do not point on the same host as the records
   for <code>myhostname.example.org</code>, you can easily move the
   <code>/.well-known</code> virtualHost section of the code to the host that
   is serving <literal>example.org</literal>, while the rest stays on
   <literal>myhostname.example.org</literal> with no other changes required.
   This pattern also allows to seamlessly move the homeserver from
   <literal>myhostname.example.org</literal> to
   <literal>myotherhost.example.org</literal> by only changing the
   <code>/.well-known</code> redirection target.
  </para>

  <para>
   If you want to run a server with public registration by anybody, you can
   then enable <option>services.matrix-synapse.enable_registration =
   true;</option>. Otherwise, or you can generate a registration secret with
   <command>pwgen -s 64 1</command> and set it with
   <option>services.matrix-synapse.registration_shared_secret</option>. To
   create a new user or admin, run the following after you have set the secret
   and have rebuilt NixOS:
<screen>
<prompt>$ </prompt>nix run nixpkgs.matrix-synapse
<prompt>$ </prompt>register_new_matrix_user -k <replaceable>your-registration-shared-secret</replaceable> http://localhost:8008
<prompt>New user localpart: </prompt><replaceable>your-username</replaceable>
<prompt>Password:</prompt>
<prompt>Confirm password:</prompt>
<prompt>Make admin [no]:</prompt>
Success!
</screen>
   In the example, this would create a user with the Matrix Identifier
   <literal>@your-username:example.org</literal>. Note that the registration
   secret ends up in the nix store and therefore is world-readable by any user
   on your machine, so it makes sense to only temporarily activate the
   <option>registration_shared_secret</option> option until a better solution
   for NixOS is in place.
  </para>
 </section>
 <section xml:id="module-services-matrix-riot-web">
  <title>Riot Web Client</title>

  <para>
   <link xlink:href="https://github.com/vector-im/riot-web/">Riot Web</link> is
   the reference web client for Matrix and developed by the core team at
   matrix.org. The following snippet can be optionally added to the code before
   to complete the synapse installation with a web client served at
   <code>https://riot.myhostname.example.org</code> and
   <code>https://riot.example.org</code>. Alternatively, you can use the hosted
   copy at <link xlink:href="https://riot.im/app">https://riot.im/app</link>,
   or use other web clients or native client applications. Due to the
   <literal>/.well-known</literal> urls set up done above, many clients should
   fill in the required connection details automatically when you enter your
   Matrix Identifier. See
   <link xlink:href="https://matrix.org/docs/projects/try-matrix-now.html">Try
   Matrix Now!</link> for a list of existing clients and their supported
   featureset.
<programlisting>
services.nginx.virtualHosts."riot.${fqdn}" = {
  enableACME = true;
  forceSSL = true;
  serverAliases = [
    "riot.${config.networking.domain}"
  ];

  root = pkgs.riot-web;
};
</programlisting>
  </para>

  <para>
   Note that the Riot developers do not recommend running Riot and your Matrix
   homeserver on the same fully-qualified domain name for security reasons. In
   the example, this means that you should not reuse the
   <literal>myhostname.example.org</literal> virtualHost to also serve Riot,
   but instead serve it on a different subdomain, like
   <literal>riot.example.org</literal> in the example. See the
   <link xlink:href="https://github.com/vector-im/riot-web#important-security-note">Riot
   Important Security Notes</link> for more information on this subject.
  </para>
 </section>
</chapter>
