[docs] add account domain documentation (#1065)

* [docs] add account domain documentation

* add note about parent/subdomain

docs/configuration/general.md

@@ -38,11 +38,18 @@ host: "localhost"
 # String. Domain to use when federating profiles. This is useful when you want your server to be at
 # eg., "gts.example.org", but you want the domain on accounts to be "example.org" because it looks better
 # or is just shorter/easier to remember.
+#
 # To make this setting work properly, you need to redirect requests at "example.org/.well-known/webfinger"
 # to "gts.example.org/.well-known/webfinger" so that GtS can handle them properly.
+#
 # You should also redirect requests at "example.org/.well-known/nodeinfo" in the same way.
 # An empty string (ie., not set) means that the same value as 'host' will be used.
+#
 # DO NOT change this after your server has already run once, or you will break things!
+#
+# Please read the appropriate section of the installation guide before you go messing around with this setting:
+# https://docs.gotosocial.org/installation_guide/advanced/#can-i-host-my-instance-at-fediexampleorg-but-have-just-exampleorg-in-my-username
+#
 # Examples: ["example.org","server.com"]
 # Default: ""
 account-domain: ""

docs/installation_guide/advanced.md

@@ -0,0 +1,158 @@
+# Advanced
+
+Advanced configuration options for GoToSocial.
+
+## Can I host my instance at `fedi.example.org` but have just `@example.org` in my username?
+
+Yes, you can! This is useful when you have something like a personal page or blog at `example.org`, but you also want your fediverse account to have `example.org` in it to avoid confusing people, or just because it looks nicer than `fedi.example.org`.
+
+Please note that you need to do this *BEFORE RUNNING GOTOSOCIAL* for the first time, or things will likely break.
+
+### Step 1: Configure GoToSocial
+
+This step is easy.
+
+In the settings, GoToSocial differentiates between `host`--the address at which your instance is accessible--and `account-domain`--which is the domain you want to show in accounts.
+
+Behold, from the example config.yaml file:
+
+```yaml
+# String. Hostname that this server will be reachable at. Defaults to localhost for local testing,
+# but you should *definitely* change this when running for real, or your server won't work at all.
+# DO NOT change this after your server has already run once, or you will break things!
+# Examples: ["gts.example.org","some.server.com"]
+# Default: "localhost"
+host: "localhost"
+
+# String. Domain to use when federating profiles. This is useful when you want your server to be at
+# eg., "gts.example.org", but you want the domain on accounts to be "example.org" because it looks better
+# or is just shorter/easier to remember.
+#
+# To make this setting work properly, you need to redirect requests at "example.org/.well-known/webfinger"
+# to "gts.example.org/.well-known/webfinger" so that GtS can handle them properly.
+#
+# You should also redirect requests at "example.org/.well-known/nodeinfo" in the same way.
+# An empty string (ie., not set) means that the same value as 'host' will be used.
+#
+# DO NOT change this after your server has already run once, or you will break things!
+#
+# Please read the appropriate section of the installation guide before you go messing around with this setting:
+# https://docs.gotosocial.org/installation_guide/advanced/#can-i-host-my-instance-at-fediexampleorg-but-have-just-exampleorg-in-my-username
+#
+# Examples: ["example.org","server.com"]
+# Default: ""
+account-domain: ""
+```
+
+The first value, `host`, is simple. In our scenario of wanting to run the GtS instance at `fedi.example.org`, this should be set to, yep, `fedi.example.org`.
+
+The second value, `account-domain` should be set to `example.org`, to indicate that that's the domain we want accounts to be displayed with.
+
+IMPORTANT: `account-domain` must be a *parent domain* of `host`, and `host` must be a *subdomain* of `account-domain`. So if your `host` is `fedi.example.org`, your `account-domain` cannot be `somewhere.else.com` or `example.com`, it **has to be** `example.org`.
+
+### Step 2: Redirect from `example.org` to `fedi.example.org`
+
+The next step is more difficult: we need to ensure that when remote instances search for the user `@user@example.org` via webfinger, they end up being pointed towards `fedi.example.org`, where our instance is actually hosted.
+
+Of course, we don't want to redirect *all* requests from `example.org` to `fedi.example.org` because that negates the purpose of having a separate domain in the first place, so we need to be specific.
+
+In the config.yaml above, there are two endpoints mentioned, both of which we need to redirect: `/.well-known/webfinger` and `/.well-known/nodeinfo`.
+
+Assuming we have an [nginx](https://nginx.org) reverse proxy running on `example.org`, we can get the redirect behavior we want by adding the following to the nginx config for `example.org`:
+
+```nginx
+http {
+    server {
+        listen 80;
+        listen [::]:80;
+        server_name example.org;
+
+        location /.well-known/webfinger {
+            rewrite ^.*$ https://fedi.example.org/.well-known/webfinger permanent;
+        }
+
+        location /.well-known/nodeinfo {
+            rewrite ^.*$ https://fedi.example.org/.well-known/nodeinfo permanent;
+        }
+
+        # The rest of our nginx config ...
+    }
+}
+```
+
+The above configuration [rewrites](https://www.nginx.com/blog/creating-nginx-rewrite-rules/) queries to `example.org/.well-known/webfinger` and `example.org/.well-known/nodeinfo` to their `fedi.example.org` counterparts, which means that query information is preserved, making it easier to follow the redirect.
+
+### Step 3: What now?
+
+Once you've done steps 1 and 2, proceed as normal with the rest of your GoToSocial installation.
+
+### Supplemental: how does this work?
+
+With the configuration we put in place in the steps above, when someone from another instance looks up `@user@example.org`, their instance will perform a webfinger request to `example.org/.well-known/webfinger?resource:acct=user@example.org` in order to discover a link to an ActivityPub representation of that user's account. They will then be redirected to  `https://fedi.example.org/.well-known/webfinger?resource:acct=user@example.org`, and their query will be resolved.
+
+The webfinger response returned by GoToSocial (and indeed Mastodon, and other ActivityPub implementations) contains the desired account domain in the `subject` part of the response, and provides links to aliases that should be used to query the account.
+
+Here's an example of this working for the `superseriousbusiness.org` GoToSocial instance, which is hosted at `gts.superseriousbusiness.org`.
+
+Curl query:
+
+```bash
+curl -v 'https://superseriousbusiness.org/.well-known/webfinger?resource=acct:@gotosocial@superseriousbusiness.org'
+```
+
+Response:
+
+```text
+> GET /.well-known/webfinger?resource=acct:@gotosocial@superseriousbusiness.org HTTP/2
+> Host: superseriousbusiness.org
+> user-agent: curl/7.68.0
+> accept: */*
+> 
+< HTTP/2 301 
+< content-type: text/html
+< date: Thu, 17 Nov 2022 11:10:39 GMT
+< location: https://gts.superseriousbusiness.org/.well-known/webfinger?resource=acct:@gotosocial@superseriousbusiness.org
+< server: nginx/1.20.1
+< content-length: 169
+< 
+<html>
+<head><title>301 Moved Permanently</title></head>
+<body>
+<center><h1>301 Moved Permanently</h1></center>
+<hr><center>nginx/1.20.1</center>
+</body>
+</html>
+
+```
+
+If we follow the redirect and make a query to the specified `location` as follows:
+
+```bash
+curl -v 'https://gts.superseriousbusiness.org/.well-known/webfinger?resource=acct:@gotosocial@superseriousbusiness.org'
+```
+
+Then we get the following response:
+
+```json
+{
+  "subject": "acct:gotosocial@superseriousbusiness.org",
+  "aliases": [
+    "https://gts.superseriousbusiness.org/users/gotosocial",
+    "https://gts.superseriousbusiness.org/@gotosocial"
+  ],
+  "links": [
+    {
+      "rel": "http://webfinger.net/rel/profile-page",
+      "type": "text/html",
+      "href": "https://gts.superseriousbusiness.org/@gotosocial"
+    },
+    {
+      "rel": "self",
+      "type": "application/activity+json",
+      "href": "https://gts.superseriousbusiness.org/users/gotosocial"
+    }
+  ]
+}
+```
+
+In the above response, note that the `subject` of the response contains the desired account-domain of `superseriousbusiness.org`, whereas the links contain the actual host value of `gts.superseriousbusiness.org`.

docs/installation_guide/index.md

@@ -29,3 +29,5 @@ If you can't leave `443` and `80` open on the machine, don't worry! You can conf
 To run a GoToSocial server, you also need a domain name, and it needs to be pointed towards your VPS or homeserver.
 
 [Namecheap](https://www.namecheap.com/) is a good place to do this, but you can use any domain name registrar that lets you manage your own DNS.
+
+IMPORTANT: If you want to host GoToSocial at a different host from your desired account domain (eg., you want to host GtS at `fedi.example.org` but you want your account to show up at `example.org`), please read the [advanced configuration](./advanced.md) carefully, before proceeding with installation!

example/config.yaml

@@ -50,11 +50,18 @@ host: "localhost"
 # String. Domain to use when federating profiles. This is useful when you want your server to be at
 # eg., "gts.example.org", but you want the domain on accounts to be "example.org" because it looks better
 # or is just shorter/easier to remember.
+#
 # To make this setting work properly, you need to redirect requests at "example.org/.well-known/webfinger"
 # to "gts.example.org/.well-known/webfinger" so that GtS can handle them properly.
+#
 # You should also redirect requests at "example.org/.well-known/nodeinfo" in the same way.
 # An empty string (ie., not set) means that the same value as 'host' will be used.
+#
 # DO NOT change this after your server has already run once, or you will break things!
+#
+# Please read the appropriate section of the installation guide before you go messing around with this setting:
+# https://docs.gotosocial.org/installation_guide/advanced/#can-i-host-my-instance-at-fediexampleorg-but-have-just-exampleorg-in-my-username
+#
 # Examples: ["example.org","server.com"]
 # Default: ""
 account-domain: ""

mkdocs.yml

@@ -28,6 +28,7 @@ nav:
     - "installation_guide/caddy.md"
     - "installation_guide/third_party.md"
     - "installation_guide/websocket.md"
+    - "installation_guide/advanced.md"
   - "Configuration":
     - "configuration/index.md"
     - "configuration/general.md"