From 2c795094535537a8607cc0d3b7f076a609636f40 Mon Sep 17 00:00:00 2001
From: Mark Felder <feld@feld.me>
Date: Thu, 3 Aug 2023 13:08:37 -0400
Subject: [PATCH] Resolve information disclosure vulnerability through emoji
 pack archive download endpoint

The pack name has been sanitized so an attacker cannot upload a media
file called pack.json with their own handcrafted list of emoji files as
arbitrary files on the filesystem and then call the emoji pack archive
download endpoint with a pack name crafted to the location of the media
file they uploaded which tricks Pleroma into generating a zip file of
the target files the attacker wants to download.

The attack only works if the Pleroma instance does not have the
AnonymizeFilename upload filter enabled, which is currently the default.

Reported by: graf@poast.org
---
 changelog.d/emoji-pack-sanitization.security | 1 +
 lib/pleroma/emoji/pack.ex                    | 1 +
 test/pleroma/emoji/pack_test.exs             | 4 ++++
 3 files changed, 6 insertions(+)
 create mode 100644 changelog.d/emoji-pack-sanitization.security

diff --git a/changelog.d/emoji-pack-sanitization.security b/changelog.d/emoji-pack-sanitization.security
new file mode 100644
index 000000000..f3218abd4
--- /dev/null
+++ b/changelog.d/emoji-pack-sanitization.security
@@ -0,0 +1 @@
+Emoji pack loader sanitizes pack names
diff --git a/lib/pleroma/emoji/pack.ex b/lib/pleroma/emoji/pack.ex
index a361ea200..6e58f8898 100644
--- a/lib/pleroma/emoji/pack.ex
+++ b/lib/pleroma/emoji/pack.ex
@@ -285,6 +285,7 @@ defmodule Pleroma.Emoji.Pack do
 
   @spec load_pack(String.t()) :: {:ok, t()} | {:error, :file.posix()}
   def load_pack(name) do
+    name = Path.basename(name)
     pack_file = Path.join([emoji_path(), name, "pack.json"])
 
     with {:ok, _} <- File.stat(pack_file),
diff --git a/test/pleroma/emoji/pack_test.exs b/test/pleroma/emoji/pack_test.exs
index 18b99da75..00001abfc 100644
--- a/test/pleroma/emoji/pack_test.exs
+++ b/test/pleroma/emoji/pack_test.exs
@@ -90,4 +90,8 @@ defmodule Pleroma.Emoji.PackTest do
 
     assert updated_pack.files_count == 1
   end
+
+  test "load_pack/1 ignores path traversal in a forged pack name", %{pack: pack} do
+    assert {:ok, ^pack} = Pack.load_pack("../../../../../dump_pack")
+  end
 end