# Matrix {#module-services-matrix}

[Matrix](https://matrix.org/) 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.

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 Element web client. See the
[Try Matrix Now!](https://matrix.org/docs/projects/try-matrix-now.html)
overview page for links to Element Apps for Android and iOS,
desktop clients, as well as bridges to other networks and other projects
around Matrix.

## Synapse Homeserver {#module-services-matrix-synapse}

[Synapse](https://github.com/element-hq/synapse) 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 `example.org` domain, served from
the host `myhostname.example.org`. For more information,
please refer to the
[installation instructions of Synapse](https://element-hq.github.io/synapse/latest/setup/installation.html) .
```
{ pkgs, lib, config, ... }:
let
  fqdn = "${config.networking.hostName}.${config.networking.domain}";
  baseUrl = "https://${fqdn}";
  clientConfig."m.homeserver".base_url = baseUrl;
  serverConfig."m.server" = "${fqdn}:443";
  mkWellKnown = data: ''
    default_type application/json;
    add_header Access-Control-Allow-Origin *;
    return 200 '${builtins.toJSON data}';
  '';
in {
  networking.hostName = "myhostname";
  networking.domain = "example.org";
  networking.firewall.allowedTCPPorts = [ 80 443 ];

  services.postgresql.enable = true;
  services.postgresql.initialScript = pkgs.writeText "synapse-init.sql" ''
    CREATE ROLE "matrix-synapse" WITH LOGIN PASSWORD 'synapse';
    CREATE DATABASE "matrix-synapse" WITH OWNER "matrix-synapse"
      TEMPLATE template0
      LC_COLLATE = "C"
      LC_CTYPE = "C";
  '';

  services.nginx = {
    enable = true;
    recommendedTlsSettings = true;
    recommendedOptimisation = true;
    recommendedGzipSettings = true;
    recommendedProxySettings = true;
    virtualHosts = {
      # If the A and AAAA DNS records on example.org do not point on the same host as the
      # records for myhostname.example.org, you can easily move the /.well-known
      # virtualHost section of the code to the host that is serving example.org, while
      # the rest stays on myhostname.example.org with no other changes required.
      # This pattern also allows to seamlessly move the homeserver from
      # myhostname.example.org to myotherhost.example.org by only changing the
      # /.well-known redirection target.
      "${config.networking.domain}" = {
        enableACME = true;
        forceSSL = true;
        # This section is not needed if the server_name of matrix-synapse is equal to
        # the domain (i.e. example.org from @foo:example.org) and the federation port
        # is 8448.
        # Further reference can be found in the docs about delegation under
        # https://element-hq.github.io/synapse/latest/delegate.html
        locations."= /.well-known/matrix/server".extraConfig = mkWellKnown serverConfig;
        # This is usually needed for homeserver discovery (from e.g. other Matrix clients).
        # Further reference can be found in the upstream docs at
        # https://spec.matrix.org/latest/client-server-api/#getwell-knownmatrixclient
        locations."= /.well-known/matrix/client".extraConfig = mkWellKnown clientConfig;
      };
      "${fqdn}" = {
        enableACME = true;
        forceSSL = true;
        # It's also possible to do a redirect here or something else, this vhost is not
        # needed for Matrix. It's recommended though to *not put* element
        # here, see also the section about Element.
        locations."/".extraConfig = ''
          return 404;
        '';
        # Forward all Matrix API calls to the synapse Matrix homeserver. A trailing slash
        # *must not* be used here.
        locations."/_matrix".proxyPass = "http://[::1]:8008";
        # Forward requests for e.g. SSO and password-resets.
        locations."/_synapse/client".proxyPass = "http://[::1]:8008";
      };
    };
  };

  services.matrix-synapse = {
    enable = true;
    settings.server_name = config.networking.domain;
    # The public base URL value must match the `base_url` value set in `clientConfig` above.
    # The default value here is based on `server_name`, so if your `server_name` is different
    # from the value of `fqdn` above, you will likely run into some mismatched domain names
    # in client applications.
    settings.public_baseurl = baseUrl;
    settings.listeners = [
      { port = 8008;
        bind_addresses = [ "::1" ];
        type = "http";
        tls = false;
        x_forwarded = true;
        resources = [ {
          names = [ "client" "federation" ];
          compress = true;
        } ];
      }
    ];
  };
}
```

## Registering Matrix users {#module-services-matrix-register-users}

If you want to run a server with public registration by anybody, you can
then enable `services.matrix-synapse.settings.enable_registration = true;`.
Otherwise, or you can generate a registration secret with
{command}`pwgen -s 64 1` and set it with
[](#opt-services.matrix-synapse.settings.registration_shared_secret).
To create a new user or admin, run the following after you have set the secret
and have rebuilt NixOS:
```ShellSession
$ nix-shell -p matrix-synapse
$ register_new_matrix_user -k your-registration-shared-secret http://localhost:8008
New user localpart: your-username
Password:
Confirm password:
Make admin [no]:
Success!
```
In the example, this would create a user with the Matrix Identifier
`@your-username:example.org`.

::: {.warning}
When using [](#opt-services.matrix-synapse.settings.registration_shared_secret), the secret
will end up in the world-readable store. Instead it's recommended to deploy the secret
in an additional file like this:

  - Create a file with the following contents:

    ```
    registration_shared_secret: your-very-secret-secret
    ```
  - Deploy the file with a secret-manager such as
    [{option}`deployment.keys`](https://nixops.readthedocs.io/en/latest/overview.html#managing-keys)
    from {manpage}`nixops(1)` or [sops-nix](https://github.com/Mic92/sops-nix/) to
    e.g. {file}`/run/secrets/matrix-shared-secret` and ensure that it's readable
    by `matrix-synapse`.
  - Include the file like this in your configuration:

    ```
    {
      services.matrix-synapse.extraConfigFiles = [
        "/run/secrets/matrix-shared-secret"
      ];
    }
    ```
:::

::: {.note}
It's also possible to user alternative authentication mechanism such as
[LDAP (via `matrix-synapse-ldap3`)](https://github.com/matrix-org/matrix-synapse-ldap3)
or [OpenID](https://element-hq.github.io/synapse/latest/openid.html).
:::

## Element (formerly known as Riot) Web Client {#module-services-matrix-element-web}

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

    root = pkgs.element-web.override {
      conf = {
        default_server_config = clientConfig; # see `clientConfig` from the snippet above.
      };
    };
  };
}
```

::: {.note}
The Element developers do not recommend running Element 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
`myhostname.example.org` virtualHost to also serve Element,
but instead serve it on a different subdomain, like
`element.example.org` in the example. See the
[Element Important Security Notes](https://github.com/vector-im/element-web/tree/v1.10.0#important-security-notes)
for more information on this subject.
:::
