chore: Add news fragment

changelog.d/1271.feature

@@ -0,0 +1 @@
+Added admin command to forcefully log out all of a user's existing sessions. Contributed by @nex.

src/admin/user/commands.rs

@@ -1017,3 +1017,29 @@ pub(super) async fn unlock(&self, user_id: String) -> Result {
 	self.write_str(&format!("User {user_id} has been unlocked."))
 		.await
 }
+
+#[admin_command]
+pub(super) async fn logout(&self, user_id: String) -> Result {
+	self.bail_restricted()?;
+	let user_id = parse_local_user_id(self.services, &user_id)?;
+	assert!(
+		self.services.globals.user_is_local(&user_id),
+		"Parsed user_id must be a local user"
+	);
+	if user_id == self.services.globals.server_user {
+		return Err!("Not allowed to log out the server service account.",);
+	}
+
+	if !self.services.users.exists(&user_id).await {
+		return Err!("User {user_id} does not exist.");
+	}
+	if self.services.users.is_admin(&user_id).await {
+		return Err!("You cannot forcefully log out admin users.");
+	}
+	self.services
+		.users
+		.all_device_ids(&user_id)
+		.for_each(|device_id| self.services.users.remove_device(&user_id, device_id))
+		.await;
+	self.write_str(&format!("User {user_id} has been logged out from all devices."))
+}

src/admin/user/mod.rs

@@ -59,6 +59,18 @@ pub enum UserCommand {
 		force: bool,
 	},
 
+	/// - Forcefully log a user out of all of their devices.
+	///
+	/// This will invalidate all access tokens for the specified user,
+	/// effectively logging them out from all sessions.
+	/// Note that this is destructive and may result in data loss for the user,
+	/// such as encryption keys. Use with caution. Can only be used in the admin
+	/// room.
+	Logout {
+		/// Username of the user to log out
+		user_id: String,
+	},
+
 	/// - Suspend a user
 	///
 	/// Suspended users are able to log in, sync, and read messages, but are not

src/api/client/membership/leave.rs

@@ -178,7 +178,20 @@ pub async fn leave_room(
 					.rooms
 					.state_cache
 					.left_state(user_id, room_id)
-					.await?
+					.await
+					.inspect_err(|err| {
+						// `left_state` may return an Err if the user _is_ in the room they're
+						// trying to leave, but the membership cache is incorrect and
+						// they're cached as being joined. In this situation
+						// we save a `None` to the `roomuserid_leftcount` table, which generates
+						// and sends a dummy leave to the client.
+						warn!(
+							?err,
+							"Trying to leave room not cached as leave, sending dummy leave \
+							 event to client"
+						);
+					})
+					.unwrap_or_default()
 			},
 		}
 	};