Add endpoint to get server publishing keys

lib/matrix_server/device.ex

@@ -42,10 +42,7 @@ defmodule MatrixServer.Device do
 
   def generate_device_id(localpart) do
     # TODO: use random string instead
-    time_string =
+    time_string = System.os_time(:millisecond) |> Integer.to_string()
-      DateTime.utc_now()
-      |> DateTime.to_unix()
-      |> Integer.to_string()
 
     "#{localpart}_#{time_string}"
   end

lib/matrix_server/event.ex

@@ -28,7 +28,7 @@ defmodule MatrixServer.Event do
       room_id: room_id,
       sender: MatrixServer.get_mxid(localpart),
       event_id: generate_event_id(),
-      origin_server_ts: DateTime.utc_now() |> DateTime.to_unix(),
+      origin_server_ts: System.os_time(:millisecond),
       prev_events: [],
       auth_events: []
     }
@@ -281,7 +281,7 @@ defmodule MatrixServer.Event do
     event
     |> Map.put(:hashes, %{"sha256" => content_hash})
     |> redact()
-    |> SigningServer.sign_event()
+    |> SigningServer.sign_object()
   end
 
   defp calculate_content_hash(event) do

lib/matrix_server/signing_server.ex

@@ -12,8 +12,12 @@ defmodule MatrixServer.SigningServer do
     GenServer.start_link(__MODULE__, opts, name: __MODULE__)
   end
 
-  def sign_event(event) do
+  def sign_object(object) do
-    GenServer.call(__MODULE__, {:sign_event, event})
+    GenServer.call(__MODULE__, {:sign_object, object})
+  end
+
+  def get_signing_keys do
+    GenServer.call(__MODULE__, :get_signing_keys)
   end
 
   ## Implementation
@@ -27,12 +31,12 @@ defmodule MatrixServer.SigningServer do
   # https://blog.swwomm.com/2020/09/elixir-ed25519-signatures-with-enacl.html
   @impl true
   def handle_call(
-        {:sign_event, event},
+        {:sign_object, object},
         _from,
         %{private_key: private_key} = state
       ) do
     ordered_map =
-      event
+      object
       |> Map.drop([:signatures, :unsigned])
       |> OrderedMap.from_map()
 
@@ -46,18 +50,24 @@ defmodule MatrixServer.SigningServer do
         signature_map = %{@signing_key_id => signature}
         servername = MatrixServer.server_name()
 
-        event =
+        signed_object =
-          Map.update(event, :signatures, %{servername => signature_map}, fn signatures ->
+          Map.update(object, :signatures, %{servername => signature_map}, fn signatures ->
             Map.put(signatures, servername, signature_map)
           end)
 
-        {:reply, event, state}
+        {:reply, {:ok, signed_object}, state}
 
       {:error, _msg} ->
         {:reply, {:error, :json_encode}, state}
     end
   end
 
+  def handle_call(:get_signing_keys, _from, %{public_key: public_key} = state) do
+    encoded_public_key = MatrixServer.encode_unpadded_base64(public_key)
+
+    {:reply, [{@signing_key_id, encoded_public_key}], state}
+  end
+
   # TODO: not sure if there is a better way to do this...
   defp get_keys do
     raw_priv_key =

lib/matrix_server_web/controllers/key_controller.ex

@@ -0,0 +1,34 @@
+defmodule MatrixServerWeb.KeyController do
+  use MatrixServerWeb, :controller
+
+  import MatrixServerWeb.Plug.Error
+
+  alias MatrixServer.SigningServer
+
+  @key_valid_time_ms 1000 * 60 * 24 * 30
+
+  def get_signing_keys(conn, _params) do
+    keys =
+      SigningServer.get_signing_keys()
+      |> Enum.into(%{}, fn {key_id, key} ->
+        {key_id, %{"key" => key}}
+      end)
+
+    data = %{
+      server_name: MatrixServer.server_name(),
+      verify_keys: keys,
+      old_verify_keys: %{},
+      valid_until_ts: System.os_time(:millisecond) + @key_valid_time_ms
+    }
+
+    case SigningServer.sign_object(data) do
+      {:ok, signed_data} ->
+        conn
+        |> put_status(200)
+        |> json(signed_data)
+
+      {:error, _msg} ->
+        put_error(conn, :unknown, "Error signing object.")
+    end
+  end
+end

lib/matrix_server_web/router.ex

@@ -22,6 +22,10 @@ defmodule MatrixServerWeb.Router do
       post "/login", AuthController, :login
     end
 
+    scope "/key/v2" do
+      get "/server", KeyController, :get_signing_keys
+    end
+
     get "/client/versions", InfoController, :versions
   end