Fix `ActivityPubController.read_inbox/2`

lib/pleroma/web/activity_pub/activity_pub_controller.ex

@@ -251,22 +251,36 @@ def whoami(%{assigns: %{user: %User{} = user}} = conn, _params) do
 
   def whoami(_conn, _params), do: {:error, :not_found}
 
-  def read_inbox(%{assigns: %{user: user}} = conn, %{"nickname" => nickname} = params) do
-    if nickname == user.nickname do
+  def read_inbox(
+        %{assigns: %{user: %{nickname: nickname} = user}} = conn,
+        %{"nickname" => nickname} = params
+      ) do
     conn
     |> put_resp_content_type("application/activity+json")
-      |> json(UserView.render("inbox.json", %{user: user, max_id: params["max_id"]}))
-    else
-      err =
-        dgettext("errors", "can't read inbox of %{nickname} as %{as_nickname}",
-          nickname: nickname,
-          as_nickname: user.nickname
-        )
+    |> put_view(UserView)
+    |> render("inbox.json", user: user, max_id: params["max_id"])
+  end
+
+  def read_inbox(%{assigns: %{user: nil}} = conn, %{"nickname" => nickname}) do
+    err = dgettext("errors", "can't read inbox of %{nickname}", nickname: nickname)
 
     conn
     |> put_status(:forbidden)
     |> json(err)
   end
+
+  def read_inbox(%{assigns: %{user: %{nickname: as_nickname}}} = conn, %{
+        "nickname" => nickname
+      }) do
+    err =
+      dgettext("errors", "can't read inbox of %{nickname} as %{as_nickname}",
+        nickname: nickname,
+        as_nickname: as_nickname
+      )
+
+    conn
+    |> put_status(:forbidden)
+    |> json(err)
   end
 
   def handle_user_activity(user, %{"type" => "Create"} = params) do

test/web/activity_pub/activity_pub_controller_test.exs

@@ -365,6 +365,17 @@ test "it rejects reads from other users", %{conn: conn} do
       assert json_response(conn, 403)
     end
 
+    test "it doesn't crash without an authenticated user", %{conn: conn} do
+      user = insert(:user)
+
+      conn =
+        conn
+        |> put_req_header("accept", "application/activity+json")
+        |> get("/users/#{user.nickname}/inbox")
+
+      assert json_response(conn, 403)
+    end
+
     test "it returns a note activity in a collection", %{conn: conn} do
       note_activity = insert(:direct_note_activity)
       note_object = Object.normalize(note_activity)