From 1781575e7528d64ddbd045a56128297178a8494b Mon Sep 17 00:00:00 2001
From: Pim Kunis <pim@kunis.nl>
Date: Wed, 18 Aug 2021 13:54:18 +0200
Subject: [PATCH] Calculate and set event id using reference hash

---
 lib/matrix_server.ex                          |  12 +-
 .../{ordered_map.ex => encodable_map.ex}      |  11 +-
 lib/matrix_server/key_server.ex               |   2 +
 lib/matrix_server/room_server.ex              | 131 ++++++++++--------
 lib/matrix_server/schema/event.ex             | 123 ++++++++++------
 .../controllers/event_controller.ex           |   6 +-
 6 files changed, 177 insertions(+), 108 deletions(-)
 rename lib/matrix_server/{ordered_map.ex => encodable_map.ex} (59%)

diff --git a/lib/matrix_server.ex b/lib/matrix_server.ex
index d3f085c..676905e 100644
--- a/lib/matrix_server.ex
+++ b/lib/matrix_server.ex
@@ -1,5 +1,5 @@
 defmodule MatrixServer do
-  alias MatrixServer.OrderedMap
+  alias MatrixServer.EncodableMap
 
   def get_mxid(localpart) when is_binary(localpart) do
     "@#{localpart}:#{server_name()}"
@@ -76,8 +76,7 @@ defmodule MatrixServer do
 
   def encode_canonical_json(object) do
     object
-    |> Map.drop([:signatures, :unsigned])
-    |> OrderedMap.from_map()
+    |> EncodableMap.from_map()
     |> Jason.encode()
   end
 
@@ -134,4 +133,11 @@ defmodule MatrixServer do
       datetime1
     end
   end
+
+  def encode_url_safe_base64(data) do
+    data
+    |> encode_unpadded_base64()
+    |> String.replace("+", "-")
+    |> String.replace("/", "_")
+  end
 end
diff --git a/lib/matrix_server/ordered_map.ex b/lib/matrix_server/encodable_map.ex
similarity index 59%
rename from lib/matrix_server/ordered_map.ex
rename to lib/matrix_server/encodable_map.ex
index 088f87d..f3200ae 100644
--- a/lib/matrix_server/ordered_map.ex
+++ b/lib/matrix_server/encodable_map.ex
@@ -1,10 +1,10 @@
 # https://github.com/michalmuskala/jason/issues/69
-defmodule MatrixServer.OrderedMap do
-  alias MatrixServer.OrderedMap
+defmodule MatrixServer.EncodableMap do
+  alias MatrixServer.EncodableMap
 
   defstruct pairs: []
 
-  defimpl Jason.Encoder, for: OrderedMap do
+  defimpl Jason.Encoder, for: EncodableMap do
     def encode(%{pairs: pairs}, opts) do
       Jason.Encode.keyword(pairs, opts)
     end
@@ -14,6 +14,9 @@ defmodule MatrixServer.OrderedMap do
     pairs =
       map
       |> Enum.map(fn
+        {k, v} when is_struct(v, DateTime) ->
+          {k, DateTime.to_unix(v, :millisecond)}
+
         {k, v} when is_map(v) ->
           {k, from_map(v)}
 
@@ -22,6 +25,6 @@ defmodule MatrixServer.OrderedMap do
       end)
       |> Enum.sort()
 
-    %OrderedMap{pairs: pairs}
+    %EncodableMap{pairs: pairs}
   end
 end
diff --git a/lib/matrix_server/key_server.ex b/lib/matrix_server/key_server.ex
index ae44e15..00076bd 100644
--- a/lib/matrix_server/key_server.ex
+++ b/lib/matrix_server/key_server.ex
@@ -42,6 +42,8 @@ defmodule MatrixServer.KeyServer do
 
   # https://blog.swwomm.com/2020/09/elixir-ed25519-signatures-with-enacl.html
   defp sign_object(object, private_key) do
+    object = Map.drop(object, [:signatures, :unsigned])
+
     with {:ok, json} <- MatrixServer.encode_canonical_json(object) do
       signature =
         json
diff --git a/lib/matrix_server/room_server.ex b/lib/matrix_server/room_server.ex
index 78d2ee0..a3a3f81 100644
--- a/lib/matrix_server/room_server.ex
+++ b/lib/matrix_server/room_server.ex
@@ -70,72 +70,85 @@ defmodule MatrixServer.RoomServer do
   end
 
   @impl true
-  def handle_call(
-        {:create_room, account,
-         %CreateRoom{room_version: room_version, name: name, topic: topic, preset: preset}},
-        _from,
-        %{room_id: room_id} = state
-      ) do
-    result =
-      Repo.transaction(fn ->
-        room = Repo.one!(from r in Room, where: r.id == ^room_id)
-        create_room = Event.create_room(room, account, room_version)
-        join_creator = Event.join(room, account, [create_room.event_id])
-        pls = Event.power_levels(room, account, [create_room.event_id, join_creator.event_id])
-        auth_events = [create_room.event_id, join_creator.event_id, pls.event_id]
-        name_event = if name, do: Event.name(room, account, name, auth_events)
-        topic_event = if topic, do: Event.topic(room, account, topic, auth_events)
+  def handle_call({:create_room, account, input}, _from, %{room_id: room_id} = state) do
+    # TODO: power_level_content_override, initial_state, invite, invite_3pid
+    room = Repo.one!(from r in Room, where: r.id == ^room_id)
 
-        # TODO: power_level_content_override, initial_state, invite, invite_3pid
-        events =
-          [create_room, join_creator, pls] ++
-            room_creation_preset(account, preset, room, auth_events) ++
-            [name_event, topic_event]
-
-        result =
-          events
-          |> Enum.reject(&Kernel.is_nil/1)
-          |> Enum.reduce_while({%{}, room}, fn event, {state_set, room} ->
-            case verify_and_insert_event(event, state_set, room) do
-              {:ok, state_set, room} -> {:cont, {state_set, room}}
-              {:error, reason} -> {:halt, {:error, reason}}
-            end
-          end)
-
-        case result do
-          {:error, reason} ->
-            Repo.rollback(reason)
-
-          {state_set, room} ->
-            serialized_state_set =
-              Enum.map(state_set, fn {{type, state_key}, event} ->
-                [type, state_key, event.event_id]
-              end)
-
-            Repo.update!(change(room, state: serialized_state_set))
-            state_set
+    case create_room_events(room, account, input) do
+      events when is_list(events) ->
+        case Repo.transaction(create_room_insert_events(room, events)) do
+          {:ok, state_set} -> {:reply, {:ok, room_id}, %{state | state_set: state_set}}
+          {:error, reason} -> {:reply, {:error, reason}, state}
+          _ -> {:reply, {:error, :unknown}, state}
         end
-      end)
 
-    case result do
-      {:ok, state_set} -> {:reply, {:ok, room_id}, %{state | state_set: state_set}}
-      {:error, reason} -> {:reply, {:error, reason}, state}
-      _ -> {:reply, {:error, :unknown}, state}
+      :error ->
+        {:reply, {:error, :event_creation}, state}
     end
   end
 
   def handle_call({:server_in_room, domain}, _from, %{state_set: state_set} = state) do
-    result = Enum.any?(state_set, fn
-      {{"m.room.member", user_id}, %Event{content: %{"membership" => "join"}}} ->
-        MatrixServer.get_domain(user_id) == domain
+    result =
+      Enum.any?(state_set, fn
+        {{"m.room.member", user_id}, %Event{content: %{"membership" => "join"}}} ->
+          MatrixServer.get_domain(user_id) == domain
 
-      _ ->
-        false
-    end)
+        _ ->
+          false
+      end)
 
     {:reply, result, state}
   end
 
+  defp create_room_events(room, account, %CreateRoom{
+         room_version: room_version,
+         name: name,
+         topic: topic,
+         preset: preset
+       }) do
+    with {:ok, create_room} <- Event.create_room(room, account, room_version),
+         {:ok, join_creator} <- Event.join(room, account, [create_room]),
+         {:ok, pls} <- Event.power_levels(room, account, [create_room, join_creator]),
+         auth_events <- [create_room, join_creator, pls],
+         {:ok, preset_events} <- room_creation_preset(account, preset, room, auth_events),
+         {:ok, name_event} <-
+           if(name, do: Event.name(room, account, name, auth_events), else: {:ok, nil}),
+         {:ok, topic_event} <-
+           if(topic, do: Event.topic(room, account, topic, auth_events), else: {:ok, nil}) do
+      events = [create_room, join_creator, pls] ++ preset_events ++ [name_event, topic_event]
+
+      Enum.reject(events, &Kernel.is_nil/1)
+    else
+      _ -> :error
+    end
+  end
+
+  defp create_room_insert_events(room, events) do
+    fn ->
+      result =
+        Enum.reduce_while(events, {%{}, room}, fn event, {state_set, room} ->
+          case verify_and_insert_event(event, state_set, room) do
+            {:ok, state_set, room} -> {:cont, {state_set, room}}
+            {:error, reason} -> {:halt, {:error, reason}}
+          end
+        end)
+
+      case result do
+        {:error, reason} ->
+          Repo.rollback(reason)
+
+        {state_set, room} ->
+          serialized_state_set =
+            Enum.map(state_set, fn {{type, state_key}, event} ->
+              [type, state_key, event.event_id]
+            end)
+
+          Repo.update!(change(room, state: serialized_state_set))
+          state_set
+      end
+    end
+  end
+
   # TODO: trusted_private_chat:
   # All invitees are given the same power level as the room creator.
   defp room_creation_preset(account, nil, %Room{visibility: visibility} = room, auth_events) do
@@ -156,11 +169,11 @@ defmodule MatrixServer.RoomServer do
         "public_chat" -> {"public", "shared", "forbidden"}
       end
 
-    [
-      Event.join_rules(room, account, join_rule, auth_events),
-      Event.history_visibility(room, account, his_vis, auth_events),
-      Event.guest_access(room, account, guest_access, auth_events)
-    ]
+    with {:ok, join_rules} <- Event.join_rules(room, account, join_rule, auth_events),
+         {:ok, his_vis} <- Event.history_visibility(room, account, his_vis, auth_events),
+         {:ok, guest_access} <- Event.guest_access(room, account, guest_access, auth_events) do
+      {:ok, [join_rules, his_vis, guest_access]}
+    end
   end
 
   defp verify_and_insert_event(
diff --git a/lib/matrix_server/schema/event.ex b/lib/matrix_server/schema/event.ex
index f95349a..20e76da 100644
--- a/lib/matrix_server/schema/event.ex
+++ b/lib/matrix_server/schema/event.ex
@@ -3,7 +3,7 @@ defmodule MatrixServer.Event do
 
   import Ecto.Query
 
-  alias MatrixServer.{Repo, Room, Event, Account, OrderedMap, KeyServer}
+  alias MatrixServer.{Repo, Room, Event, Account, EncodableMap, KeyServer}
 
   @primary_key {:event_id, :string, []}
   schema "events" do
@@ -26,46 +26,58 @@ defmodule MatrixServer.Event do
     %Event{
       room_id: room_id,
       sender: MatrixServer.get_mxid(localpart),
-      event_id: generate_event_id(),
       origin_server_ts: DateTime.utc_now(),
       prev_events: [],
       auth_events: []
     }
   end
 
-  def create_room(room, %Account{localpart: localpart} = creator, room_version, auth_events \\ []) do
+  def create_room(
+        room,
+        %Account{localpart: localpart} = creator,
+        room_version,
+        generate_id \\ true
+      ) do
     mxid = MatrixServer.get_mxid(localpart)
 
-    %Event{
+    event = %Event{
       new(room, creator)
       | type: "m.room.create",
         state_key: "",
         content: %{
           "creator" => mxid,
           "room_version" => room_version || MatrixServer.default_room_version()
-        },
-        auth_events: auth_events
+        }
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def join(room, %Account{localpart: localpart} = sender, auth_events \\ []) do
+  def join(room, %Account{localpart: localpart} = sender, auth_events, generate_id \\ true) do
     mxid = MatrixServer.get_mxid(localpart)
 
-    %Event{
+    event = %Event{
       new(room, sender)
       | type: "m.room.member",
         state_key: mxid,
         content: %{
           "membership" => "join"
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def power_levels(room, %Account{localpart: localpart} = sender, auth_events \\ []) do
+  def power_levels(
+        room,
+        %Account{localpart: localpart} = sender,
+        auth_events,
+        generate_id \\ true
+      ) do
     mxid = MatrixServer.get_mxid(localpart)
 
-    %Event{
+    event = %Event{
       new(room, sender)
       | type: "m.room.power_levels",
         state_key: "",
@@ -85,72 +97,80 @@ defmodule MatrixServer.Event do
             "room" => 50
           }
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def name(room, sender, name, auth_events \\ []) do
-    %Event{
+  def name(room, sender, name, auth_events, generate_id \\ true) do
+    event = %Event{
       new(room, sender)
       | type: "m.room.name",
         state_key: "",
         content: %{
           "name" => name
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def topic(room, sender, topic, auth_events \\ []) do
-    %Event{
+  def topic(room, sender, topic, auth_events, generate_id \\ true) do
+    event = %Event{
       new(room, sender)
       | type: "m.room.topic",
         state_key: "",
         content: %{
           "topic" => topic
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def join_rules(room, sender, join_rule, auth_events \\ []) do
-    %Event{
+  def join_rules(room, sender, join_rule, auth_events, generate_id \\ true) do
+    event = %Event{
       new(room, sender)
       | type: "m.room.join_rules",
         state_key: "",
         content: %{
           "join_rule" => join_rule
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def history_visibility(room, sender, history_visibility, auth_events \\ []) do
-    %Event{
+  def history_visibility(room, sender, history_visibility, auth_events, generate_id \\ true) do
+    event = %Event{
       new(room, sender)
       | type: "m.room.history_visibility",
         state_key: "",
         content: %{
           "history_visibility" => history_visibility
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
+
+    if generate_id, do: set_event_id(event), else: event
   end
 
-  def guest_access(room, sender, guest_access, auth_events \\ []) do
-    %Event{
+  def guest_access(room, sender, guest_access, auth_events, generate_id \\ true) do
+    event = %Event{
       new(room, sender)
       | type: "m.room.guest_access",
         state_key: "",
         content: %{
           "guest_access" => guest_access
         },
-        auth_events: auth_events
+        auth_events: Enum.map(auth_events, & &1.event_id)
     }
-  end
 
-  def generate_event_id do
-    "$" <> MatrixServer.random_string(17) <> ":" <> MatrixServer.server_name()
+    if generate_id, do: set_event_id(event), else: event
   end
 
   def is_control_event(%Event{type: "m.room.power_levels", state_key: ""}), do: true
@@ -275,7 +295,10 @@ defmodule MatrixServer.Event do
   end
 
   def sign(event) do
-    content_hash = calculate_content_hash(event)
+    content_hash =
+      event
+      |> calculate_content_hash()
+      |> MatrixServer.encode_unpadded_base64()
 
     event
     |> Map.put(:hashes, %{"sha256" => content_hash})
@@ -284,20 +307,15 @@ defmodule MatrixServer.Event do
   end
 
   defp calculate_content_hash(event) do
-    result =
+    m =
       event
       |> MatrixServer.to_serializable_map()
       |> Map.drop([:unsigned, :signature, :hashes])
-      |> OrderedMap.from_map()
+      |> EncodableMap.from_map()
       |> Jason.encode()
 
-    case result do
-      {:ok, json} ->
-        :crypto.hash(:sha256, json)
-        |> MatrixServer.encode_unpadded_base64()
-
-      error ->
-        error
+    with {:ok, json} <- Jason.encode(m) do
+      :crypto.hash(:sha256, json)
     end
   end
 
@@ -346,4 +364,29 @@ defmodule MatrixServer.Event do
         "users",
         "users_default"
       ])
+
+  defp redact_content(_, _), do: %{}
+
+  def set_event_id(event) do
+    with {:ok, event_id} <- generate_event_id(event) do
+      {:ok, %Event{event | event_id: event_id}}
+    end
+  end
+
+  defp generate_event_id(event) do
+    with {:ok, hash} <- calculate_reference_hash(event) do
+      {:ok, "$" <> MatrixServer.encode_url_safe_base64(hash)}
+    end
+  end
+
+  defp calculate_reference_hash(event) do
+    redacted_event =
+      event
+      |> redact()
+      |> Map.drop([:unsigned, :signature, :age_ts])
+
+    with {:ok, json} <- MatrixServer.encode_canonical_json(redacted_event) do
+      {:ok, :crypto.hash(:sha256, json)}
+    end
+  end
 end
diff --git a/lib/matrix_server_web/federation/controllers/event_controller.ex b/lib/matrix_server_web/federation/controllers/event_controller.ex
index b3068c7..9721a0d 100644
--- a/lib/matrix_server_web/federation/controllers/event_controller.ex
+++ b/lib/matrix_server_web/federation/controllers/event_controller.ex
@@ -2,7 +2,9 @@ defmodule MatrixServerWeb.Federation.EventController do
   use MatrixServerWeb, :controller
   use MatrixServerWeb.Federation.AuthenticateServer
 
-  def event(conn, %{"event_id" => event_id}) do
-
+  def event(conn, %{"event_id" => _event_id}) do
+    conn
+    |> put_status(200)
+    |> json(%{})
   end
 end