132 lines
5.9 KiB
Markdown
132 lines
5.9 KiB
Markdown
---
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title: Setting up the domain
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parent: Installation
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nav_order: 2
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permalink: /installation/domainname
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---
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# Setting up the domain
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Every Matrix server deployment requires a server name which uniquely identifies it. For
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example, if you are using the server name `example.com`, then your users will have usernames
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that take the format `@user:example.com`.
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For federation to work, the server name must be resolvable by other homeservers on the internet
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— that is, the domain must be registered and properly configured with the relevant DNS records.
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Matrix servers usually discover each other when federating using the following methods:
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1. If a well-known delegation exists on `example.com`, use the domain and port from the
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well-known file to connect to the remote homeserver;
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2. If a DNS SRV delegation exists on `example.com`, use the IP address and port from the DNS SRV
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record to connect to the remote homeserver;
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3. If neither well-known nor DNS SRV delegation are configured, attempt to connect to the remote
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homeserver by connecting to `example.com` port TCP/8448 using HTTPS.
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The exact details of how server name resolution works can be found in
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[the spec](https://spec.matrix.org/v1.3/server-server-api/#resolving-server-names).
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## TLS certificates
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Matrix federation requires that valid TLS certificates are present on the domain. You must
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obtain certificates from a publicly-trusted certificate authority (CA). [Let's Encrypt](https://letsencrypt.org)
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is a popular choice of CA because the certificates are publicly-trusted, free, and automated
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via the ACME protocol. (Self-signed certificates are not suitable for federation and will typically
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not be accepted by other homeservers.)
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Automating the renewal of TLS certificates is best practice. There are many tools for this,
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but the simplest way to achieve TLS automation is to have your reverse proxy do it for you.
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[Caddy](https://caddyserver.com) is recommended as a production-grade reverse proxy with
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automatic TLS which is commonly used in front of Dendrite. It obtains and renews TLS certificates
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automatically and by default as long as your domain name is pointed at your server first.
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Although the finer details of [configuring Caddy](https://caddyserver.com/docs/) is not described
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here, in general, you must reverse proxy all `/_matrix` paths to your Dendrite server. For example,
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with Caddy:
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```
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reverse_proxy /_matrix/* localhost:8008
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```
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It is possible for the reverse proxy to listen on the standard HTTPS port TCP/443 so long as your
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domain delegation is configured to point to port TCP/443.
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## Delegation
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Delegation allows you to specify the server name and port that your Dendrite installation is
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reachable at, or to host the Dendrite server at a different server name to the domain that
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is being delegated.
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For example, if your Dendrite installation is actually reachable at `matrix.example.com` port 8448,
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you will be able to delegate from `example.com` to `matrix.example.com` so that your users will have
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`@user:example.com` user names instead of `@user:matrix.example.com` usernames.
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Delegation can be performed in one of two ways:
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* **Well-known delegation (preferred)**: A well-known text file is served over HTTPS on the domain
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name that you want to use, pointing to your server on `matrix.example.com` port 8448;
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* **DNS SRV delegation (not recommended)**: See the SRV delegation section below for details.
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If you are using a reverse proxy to forward `/_matrix` to Dendrite, your well-known or delegation
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must refer to the hostname and port that the reverse proxy is listening on instead.
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## Well-known delegation
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Using well-known delegation requires that you are running a web server at `example.com` which
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is listening on the standard HTTPS port TCP/443.
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Assuming that your Dendrite installation is listening for HTTPS connections at `matrix.example.com`
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on port 8448, the delegation file must be served at `https://example.com/.well-known/matrix/server`
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and contain the following JSON document:
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```json
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{
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"m.server": "matrix.example.com:8448"
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}
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```
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For example, this can be done with the following Caddy config:
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```
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handle /.well-known/matrix/server {
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header Content-Type application/json
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header Access-Control-Allow-Origin *
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respond `{"m.server": "matrix.example.com:8448"}`
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}
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handle /.well-known/matrix/client {
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header Content-Type application/json
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header Access-Control-Allow-Origin *
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respond `{"m.homeserver": {"base_url": "https://matrix.example.com:8448"}}`
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}
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```
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You can also serve `.well-known` with Dendrite itself by setting the `well_known_server_name` config
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option to the value you want for `m.server`. This is primarily useful if Dendrite is exposed on
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`example.com:443` and you don't want to set up a separate webserver just for serving the `.well-known`
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file.
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```yaml
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global:
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...
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well_known_server_name: "example.com:443"
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```
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## DNS SRV delegation
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This method is not recommended, as the behavior of SRV records in Matrix is rather unintuitive:
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SRV records will only change the IP address and port that other servers connect to, they won't
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affect the domain name. In technical terms, the `Host` header and TLS SNI of federation requests
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will still be `example.com` even if the SRV record points at `matrix.example.com`.
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In practice, this means that the server must be configured with valid TLS certificates for
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`example.com`, rather than `matrix.example.com` as one might intuitively expect. If there's a
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reverse proxy in between, the proxy configuration must be written as if it's `example.com`, as the
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proxy will never see the name `matrix.example.com` in incoming requests.
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This behavior also means that if `example.com` and `matrix.example.com` point at the same IP
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address, there is no reason to have a SRV record pointing at `matrix.example.com`. It can still
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be used to change the port number, but it won't do anything else.
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If you understand how SRV records work and still want to use them, the service name is `_matrix` and
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the protocol is `_tcp`.
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