From 77d57c974ad83fcea77e424d53dc16a27e5d88b6 Mon Sep 17 00:00:00 2001
From: FloatingGhost <hannah@coffee-and-dreams.uk>
Date: Fri, 4 Aug 2023 22:24:32 +0100
Subject: [PATCH] Add unit test for external entity loading

---
 test/fixtures/xml_external_entities.xml |  3 +++
 test/pleroma/web/web_finger_test.exs    | 23 +++++++++++++++++++++++
 test/pleroma/web/xml_test.exs           | 10 ++++++++++
 3 files changed, 36 insertions(+)
 create mode 100644 test/fixtures/xml_external_entities.xml
 create mode 100644 test/pleroma/web/xml_test.exs

diff --git a/test/fixtures/xml_external_entities.xml b/test/fixtures/xml_external_entities.xml
new file mode 100644
index 000000000..d5ff87134
--- /dev/null
+++ b/test/fixtures/xml_external_entities.xml
@@ -0,0 +1,3 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<!DOCTYPE foo [ <!ENTITY xxe SYSTEM "file:///etc/passwd"> ]>
+<stockCheck><productId>&xxe;</productId></stockCheck>
diff --git a/test/pleroma/web/web_finger_test.exs b/test/pleroma/web/web_finger_test.exs
index fafef54fe..be5e08776 100644
--- a/test/pleroma/web/web_finger_test.exs
+++ b/test/pleroma/web/web_finger_test.exs
@@ -180,5 +180,28 @@ test "respects xml content-type" do
 
       {:ok, _data} = WebFinger.finger("pekorino@pawoo.net")
     end
+
+    test "refuses to process XML remote entities" do
+      Tesla.Mock.mock(fn
+        %{
+          url: "https://pawoo.net/.well-known/webfinger?resource=acct:pekorino@pawoo.net"
+        } ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/xml_external_entities.xml"),
+             headers: [{"content-type", "application/xrd+xml"}]
+           }}
+
+        %{url: "https://pawoo.net/.well-known/host-meta"} ->
+          {:ok,
+           %Tesla.Env{
+             status: 200,
+             body: File.read!("test/fixtures/tesla_mock/pawoo.net_host_meta")
+           }}
+      end)
+
+      assert :error = WebFinger.finger("pekorino@pawoo.net")
+    end
   end
 end
diff --git a/test/pleroma/web/xml_test.exs b/test/pleroma/web/xml_test.exs
new file mode 100644
index 000000000..89d4709b6
--- /dev/null
+++ b/test/pleroma/web/xml_test.exs
@@ -0,0 +1,10 @@
+defmodule Pleroma.Web.XMLTest do
+  use Pleroma.DataCase, async: true
+
+  alias Pleroma.Web.XML
+
+  test "refuses to load external entities from XML" do
+    data = File.read!("test/fixtures/xml_external_entities.xml")
+    assert(:error == XML.parse_document(data))
+  end
+end