Implement retrieving a single event over federation

Fix url encoding during homeserver signature check

lib/matrix_server_web/federation/authenticate_server.ex

@@ -12,8 +12,18 @@ defmodule MatrixServerWeb.Federation.AuthenticateServer do
         method: method,
         query_string: query_string
       }) do
+    # TODO: This will break if request ends with '?'.
+    uri = URI.decode_www_form(path)
+
+    uri =
+      if String.length(query_string) > 0 do
+        uri <> "?" <> URI.decode_www_form(query_string)
+      else
+        uri
+      end
+
     object_to_sign = %{
-      uri: path <> "?" <> URI.decode_www_form(query_string),
+      uri: uri,
       method: method,
       destination: MatrixServer.server_name()
     }
@@ -39,6 +49,7 @@ defmodule MatrixServerWeb.Federation.AuthenticateServer do
              ServerKeyInfo.with_fresh_signing_keys(origin) do
         Enum.find_value(keys, false, fn %SigningKey{signing_key: signing_key} ->
           with {:ok, decoded_key} <- MatrixServer.decode_base64(signing_key) do
+            IO.puts(encoded_object)
             MatrixServer.sign_verify(raw_sig, encoded_object, decoded_key)
           else
             _ -> false

lib/matrix_server_web/federation/controllers/event_controller.ex

@@ -2,9 +2,44 @@ defmodule MatrixServerWeb.Federation.EventController do
   use MatrixServerWeb, :controller
   use MatrixServerWeb.Federation.AuthenticateServer
 
-  def event(conn, %{"event_id" => _event_id}) do
-    conn
-    |> put_status(200)
-    |> json(%{})
+  import MatrixServerWeb.Error
+  import Ecto.Query
+
+  alias MatrixServer.{Repo, Event, RoomServer}
+  alias MatrixServerWeb.Federation.Transaction
+
+  def event(%Plug.Conn{assigns: %{origin: origin}} = conn, %{"event_id" => event_id}) do
+    query =
+      Event
+      |> where([e], e.event_id == ^event_id)
+      |> preload(:room)
+
+    case Repo.one(query) do
+      %Event{room: room} = event ->
+        case RoomServer.get_room_server(room) do
+          {:ok, pid} ->
+            if RoomServer.server_in_room(pid, origin) do
+              data = Transaction.new([event])
+
+              conn
+              |> put_status(200)
+              |> json(data)
+            else
+              put_error(
+                conn,
+                :unauthorized,
+                "Origin server is not allowed to see requested event."
+              )
+            end
+
+          _ ->
+            put_error(conn, :unknown)
+        end
+
+      nil ->
+        put_error(conn, :not_found, "Event or room not found.")
+    end
   end
+
+  def event(conn, _), do: put_error(conn, :bad_json)
 end

lib/matrix_server_web/federation/controllers/key_controller.ex

@@ -20,7 +20,7 @@ defmodule MatrixServerWeb.Federation.KeyController do
       server_name: MatrixServer.server_name(),
       verify_keys: keys,
       old_verify_keys: %{},
-      valid_until_ts: valid_until
+      valid_until_ts: DateTime.to_unix(valid_until, :millisecond)
     }
 
     case KeyServer.sign_object(data) do

lib/matrix_server_web/federation/http_client.ex

@@ -29,7 +29,9 @@ defmodule MatrixServerWeb.Federation.HTTPClient do
     with {:ok,
           %GetSigningKeys{server_name: server_name, verify_keys: verify_keys, signatures: sigs} =
             response} <- tesla_request(:get, client, path, GetSigningKeys),
-         {:ok, encoded_body} <- MatrixServer.serialize_and_encode(response),
+         serializable_response <- MatrixServer.to_serializable_map(response),
+         serializable_response <- Map.drop(serializable_response, [:signatures]),
+         {:ok, encoded_body} <- MatrixServer.encode_canonical_json(serializable_response),
          server_sigs when not is_nil(server_sigs) <- sigs[server_name] do
       # For each verify key, check if there is a matching signature.
       # If not, invalidate the whole response.
@@ -58,12 +60,20 @@ defmodule MatrixServerWeb.Federation.HTTPClient do
     Tesla.get(client, path)
   end
 
+  def get_event(client, event_id) do
+    path = RouteHelpers.event_path(Endpoint, :event, event_id)
+
+    Tesla.get(client, path)
+  end
+
   defp tesla_request(method, client, path, request_schema) do
     with {:ok, %Tesla.Env{body: body}} <- Tesla.request(client, url: path, method: method),
          %Ecto.Changeset{valid?: true} = cs <- apply(request_schema, :changeset, [body]) do
       {:ok, Ecto.Changeset.apply_changes(cs)}
     else
-      _ -> :error
+      x ->
+        IO.inspect(x)
+        :error
     end
   end
 end

lib/matrix_server_web/federation/transaction.ex

@@ -0,0 +1,36 @@
+defmodule MatrixServerWeb.Federation.Transaction do
+  alias MatrixServer.Event
+  alias MatrixServerWeb.Federation.Transaction
+
+  # TODO
+  @type edu :: any()
+
+  @type t :: %__MODULE__{
+    origin: String.t(),
+    origin_server_ts: integer(),
+    pdus: [Event.t()],
+    edus: [edu()] | nil
+  }
+
+  defstruct [:origin, :origin_server_ts, :pdus, :edus]
+
+  defimpl Jason.Encoder, for: Transaction do
+    @fields [:origin, :origin_server_ts, :pdus, :edus]
+
+    def encode(transaction, opts) do
+      transaction
+      |> Map.take(@fields)
+      |> Jason.Encode.map(opts)
+    end
+  end
+
+  @spec new([Event.t()], [edu()] | nil) :: t()
+  def new(pdu_events, edus \\ nil) do
+    %Transaction{
+      origin: MatrixServer.server_name(),
+      origin_server_ts: System.os_time(:millisecond),
+      pdus: Enum.map(pdu_events, &MatrixServer.to_serializable_map/1),
+      edus: edus
+    }
+  end
+end