refactor: Centralize server forbidden checks into moderation module

This moves all checks related to `forbidden_remote_server_names`,
`forbidden_remote_room_directory_server_names` and
`prevent_media_downloads_from` to a new `moderation` module.
This is useful for implementing more complicated logic globally.
Mostly the changes from #673, but is also relevant for #750

src/service/federation/execute.rs

@@ -64,13 +64,7 @@ where
 		return Err!(Config("allow_federation", "Federation is disabled."));
 	}
 
-	if self
-		.services
-		.server
-		.config
-		.forbidden_remote_server_names
-		.is_match(dest.host())
-	{
+	if self.services.moderation.is_remote_server_forbidden(dest) {
 		return Err!(Request(Forbidden(debug_warn!("Federation with {dest} is not allowed."))));
 	}
 

src/service/federation/mod.rs

@@ -4,7 +4,7 @@ use std::sync::Arc;
 
 use conduwuit::{Result, Server};
 
-use crate::{Dep, client, resolver, server_keys};
+use crate::{Dep, client, moderation, resolver, server_keys};
 
 pub struct Service {
 	services: Services,
@@ -15,6 +15,7 @@ struct Services {
 	client: Dep<client::Service>,
 	resolver: Dep<resolver::Service>,
 	server_keys: Dep<server_keys::Service>,
+	moderation: Dep<moderation::Service>,
 }
 
 impl crate::Service for Service {
@@ -25,6 +26,7 @@ impl crate::Service for Service {
 				client: args.depend::<client::Service>("client"),
 				resolver: args.depend::<resolver::Service>("resolver"),
 				server_keys: args.depend::<server_keys::Service>("server_keys"),
+				moderation: args.depend::<moderation::Service>("moderation"),
 			},
 		}))
 	}

src/service/media/mod.rs

@@ -22,7 +22,7 @@ use tokio::{
 
 use self::data::{Data, Metadata};
 pub use self::thumbnail::Dim;
-use crate::{Dep, client, globals, sending};
+use crate::{Dep, client, globals, moderation, sending};
 
 #[derive(Debug)]
 pub struct FileMeta {
@@ -42,6 +42,7 @@ struct Services {
 	client: Dep<client::Service>,
 	globals: Dep<globals::Service>,
 	sending: Dep<sending::Service>,
+	moderation: Dep<moderation::Service>,
 }
 
 /// generated MXC ID (`media-id`) length
@@ -64,6 +65,7 @@ impl crate::Service for Service {
 				client: args.depend::<client::Service>("client"),
 				globals: args.depend::<globals::Service>("globals"),
 				sending: args.depend::<sending::Service>("sending"),
+				moderation: args.depend::<moderation::Service>("moderation"),
 			},
 		}))
 	}

src/service/media/remote.rs

@@ -423,16 +423,8 @@ pub async fn fetch_remote_content_legacy(
 fn check_fetch_authorized(&self, mxc: &Mxc<'_>) -> Result<()> {
 	if self
 		.services
-		.server
-		.config
-		.prevent_media_downloads_from
-		.is_match(mxc.server_name.host())
-		|| self
-			.services
-			.server
-			.config
-			.forbidden_remote_server_names
-			.is_match(mxc.server_name.host())
+		.moderation
+		.is_remote_server_media_downloads_forbidden(mxc.server_name)
 	{
 		// we'll lie to the client and say the blocked server's media was not found and
 		// log. the client has no way of telling anyways so this is a security bonus.

src/service/mod.rs

@@ -16,6 +16,7 @@ pub mod federation;
 pub mod globals;
 pub mod key_backups;
 pub mod media;
+pub mod moderation;
 pub mod presence;
 pub mod pusher;
 pub mod resolver;

src/service/moderation.rs

@@ -0,0 +1,62 @@
+use std::sync::Arc;
+
+use conduwuit::{Result, Server, implement};
+use ruma::ServerName;
+
+pub struct Service {
+	services: Services,
+}
+
+struct Services {
+	pub server: Arc<Server>,
+}
+
+impl crate::Service for Service {
+	fn build(args: crate::Args<'_>) -> Result<Arc<Self>> {
+		Ok(Arc::new(Self {
+			services: Services { server: args.server.clone() },
+		}))
+	}
+
+	fn name(&self) -> &str { crate::service::make_name(std::module_path!()) }
+}
+
+#[implement(Service)]
+#[must_use]
+pub fn is_remote_server_forbidden(&self, server_name: &ServerName) -> bool {
+	// Forbidden if NOT (allowed is empty OR allowed contains server OR is self)
+	// OR forbidden contains server
+	self.services
+		.server
+		.config
+		.forbidden_remote_server_names
+		.is_match(server_name.host())
+}
+
+#[implement(Service)]
+#[must_use]
+pub fn is_remote_server_room_directory_forbidden(&self, server_name: &ServerName) -> bool {
+	// Forbidden if NOT (allowed is empty OR allowed contains server OR is self)
+	// OR forbidden contains server
+	self.is_remote_server_forbidden(server_name)
+		|| self
+			.services
+			.server
+			.config
+			.forbidden_remote_room_directory_server_names
+			.is_match(server_name.host())
+}
+
+#[implement(Service)]
+#[must_use]
+pub fn is_remote_server_media_downloads_forbidden(&self, server_name: &ServerName) -> bool {
+	// Forbidden if NOT (allowed is empty OR allowed contains server OR is self)
+	// OR forbidden contains server
+	self.is_remote_server_forbidden(server_name)
+		|| self
+			.services
+			.server
+			.config
+			.prevent_media_downloads_from
+			.is_match(server_name.host())
+}

src/service/services.rs

@@ -12,7 +12,7 @@ use tokio::sync::Mutex;
 use crate::{
 	account_data, admin, appservice, client, config, emergency, federation, globals, key_backups,
 	manager::Manager,
-	media, presence, pusher, resolver, rooms, sending, server_keys, service,
+	media, moderation, presence, pusher, resolver, rooms, sending, server_keys, service,
 	service::{Args, Map, Service},
 	sync, transaction_ids, uiaa, updates, users,
 };
@@ -39,6 +39,7 @@ pub struct Services {
 	pub uiaa: Arc<uiaa::Service>,
 	pub updates: Arc<updates::Service>,
 	pub users: Arc<users::Service>,
+	pub moderation: Arc<moderation::Service>,
 
 	manager: Mutex<Option<Arc<Manager>>>,
 	pub(crate) service: Arc<Map>,
@@ -106,6 +107,7 @@ impl Services {
 			uiaa: build!(uiaa::Service),
 			updates: build!(updates::Service),
 			users: build!(users::Service),
+			moderation: build!(moderation::Service),
 
 			manager: Mutex::new(None),
 			service,