Disallow nil hosts in should_federate

CHANGELOG.md

@@ -4,6 +4,11 @@ All notable changes to this project will be documented in this file.
 
 The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
+## Unreleased
+
+## Fixed
+- Issue where a bad inbox URL could break federation
+
 ## 2023.08
 
 ## Added

lib/pleroma/web/activity_pub/publisher.ex

@@ -115,13 +115,17 @@ defp allowed_instances do
   def should_federate?(url) do
     %{host: host} = URI.parse(url)
 
-    with allowed <- allowed_instances(),
+    with {:nil, false} <- {:nil, is_nil(host)},
+         allowed <- allowed_instances(),
          false <- Enum.empty?(allowed) do
       allowed
       |> Pleroma.Web.ActivityPub.MRF.instance_list_from_tuples()
       |> Pleroma.Web.ActivityPub.MRF.subdomains_regex()
       |> Pleroma.Web.ActivityPub.MRF.subdomain_match?(host)
     else
+      # oi!
+      {:nil, true} ->
+        false
       _ ->
         quarantined_instances =
           blocked_instances()

test/pleroma/web/activity_pub/publisher_test.exs

@@ -487,4 +487,11 @@ test "publish to url with with different ports" do
              )
     end
   end
+
+  describe "should_federate/1" do
+    test "should not obliterate itself if the inbox URL is bad" do
+      url = "/inbox"
+      refute Pleroma.Web.ActivityPub.Publisher.should_federate?(url)
+    end
+  end
 end