truncate fields for remote users instead

lib/pleroma/user/info.ex

@@ -242,6 +242,7 @@ def set_keys(info, keys) do
   end
 
   def remote_user_creation(info, params) do
+    params = Map.put(params, "fields", Enum.map(params["fields"], &truncate_field/1))
     info
     |> cast(params, [
       :ap_enabled,
@@ -326,6 +327,12 @@ defp valid_field?(%{"name" => name, "value" => value}) do
 
   defp valid_field?(_), do: false
 
+  defp truncate_field(%{"name" => name, "value" => value}) do
+    {name, _chopped} = String.split_at(name, Pleroma.Config.get([:instance, :account_field_name_length], 255))
+    {value, _chopped} = String.split_at(value, Pleroma.Config.get([:instance, :account_field_value_length], 255))
+    %{"name" => name, "value" => value}
+  end
+
   @spec confirmation_changeset(Info.t(), keyword()) :: Changeset.t()
   def confirmation_changeset(info, opts) do
     need_confirmation? = Keyword.get(opts, :need_confirmation)

test/user_test.exs

@@ -1117,13 +1117,22 @@ test "get_public_key_for_ap_id fetches a user that's not in the db" do
     assert {:ok, _key} = User.get_public_key_for_ap_id("http://mastodon.example.org/users/admin")
   end
 
-  test "insert or update a user from given data" do
+  describe "insert or update a user from given data" do
+    test "with normal data" do
         user = insert(:user, %{nickname: "nick@name.de"})
         data = %{ap_id: user.ap_id <> "xxx", name: user.name, nickname: user.nickname}
 
         assert {:ok, %User{}} = User.insert_or_update_user(data)
     end
 
+    test "with overly long fields" do
+        current_max_length = Pleroma.Config.get([:instance, :account_field_value_length], 255)
+        user = insert(:user, nickname: "nickname@supergood.domain")
+        data = %{ap_id: user.ap_id, info: %{ fields: [%{"name" => "myfield", "value" => String.duplicate("h", current_max_length + 1)}] }}
+        assert {:ok, %User{}} = User.insert_or_update_user(data)
+    end
+  end
+
   describe "per-user rich-text filtering" do
     test "html_filter_policy returns default policies, when rich-text is enabled" do
       user = insert(:user)