StealEmojiPolicy: Sanitise emoji names.

lib/pleroma/web/activity_pub/mrf/steal_emoji_policy.ex

@@ -20,6 +20,19 @@ defmodule Pleroma.Web.ActivityPub.MRF.StealEmojiPolicy do
     String.match?(shortcode, pattern)
   end
 
+  defp reject_emoji?({shortcode, _url}, installed_emoji) do
+    valid_shortcode? = String.match?(shortcode, ~r/^[a-zA-Z0-9_-]+$/)
+
+    rejected_shortcode? =
+      [:mrf_steal_emoji, :rejected_shortcodes]
+      |> Config.get([])
+      |> Enum.any?(fn pattern -> shortcode_matches?(shortcode, pattern) end)
+
+    emoji_installed? = Enum.member?(installed_emoji, shortcode)
+
+    !valid_shortcode? or rejected_shortcode? or emoji_installed?
+  end
+
   defp steal_emoji({shortcode, url}, emoji_dir_path) do
     url = Pleroma.Web.MediaProxy.url(url)
 
@@ -78,16 +91,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.StealEmojiPolicy do
 
       new_emojis =
         foreign_emojis
-        |> Enum.reject(fn {shortcode, _url} -> shortcode in installed_emoji end)
-        |> Enum.reject(fn {shortcode, _url} -> String.contains?(shortcode, ["/", "\\"]) end)
-        |> Enum.filter(fn {shortcode, _url} ->
-          reject_emoji? =
-            [:mrf_steal_emoji, :rejected_shortcodes]
-            |> Config.get([])
-            |> Enum.find(false, fn pattern -> shortcode_matches?(shortcode, pattern) end)
-
-          !reject_emoji?
-        end)
+        |> Enum.reject(&reject_emoji?(&1, installed_emoji))
         |> Enum.map(&steal_emoji(&1, emoji_dir_path))
         |> Enum.filter(& &1)
 

test/pleroma/web/activity_pub/mrf/steal_emoji_policy_test.exs

@@ -87,7 +87,7 @@ defmodule Pleroma.Web.ActivityPub.MRF.StealEmojiPolicyTest do
     assert File.exists?(fullpath)
   end
 
-  test "rejects invalid shortcodes", %{path: path} do
+  test "rejects invalid shortcodes with slashes", %{path: path} do
     message = %{
       "type" => "Create",
       "object" => %{
@@ -113,6 +113,58 @@ defmodule Pleroma.Web.ActivityPub.MRF.StealEmojiPolicyTest do
     refute File.exists?(fullpath)
   end
 
+  test "rejects invalid shortcodes with dots", %{path: path} do
+    message = %{
+      "type" => "Create",
+      "object" => %{
+        "emoji" => [{"fired.fox", "https://example.org/emoji/firedfox"}],
+        "actor" => "https://example.org/users/admin"
+      }
+    }
+
+    fullpath = Path.join(path, "fired.fox.png")
+
+    Tesla.Mock.mock(fn %{method: :get, url: "https://example.org/emoji/firedfox"} ->
+      %Tesla.Env{status: 200, body: File.read!("test/fixtures/image.jpg")}
+    end)
+
+    clear_config(:mrf_steal_emoji, hosts: ["example.org"], size_limit: 284_468)
+
+    refute "fired.fox" in installed()
+    refute File.exists?(path)
+
+    assert {:ok, _message} = StealEmojiPolicy.filter(message)
+
+    refute "fired.fox" in installed()
+    refute File.exists?(fullpath)
+  end
+
+  test "rejects invalid shortcodes with special characters", %{path: path} do
+    message = %{
+      "type" => "Create",
+      "object" => %{
+        "emoji" => [{"fired:fox", "https://example.org/emoji/firedfox"}],
+        "actor" => "https://example.org/users/admin"
+      }
+    }
+
+    fullpath = Path.join(path, "fired:fox.png")
+
+    Tesla.Mock.mock(fn %{method: :get, url: "https://example.org/emoji/firedfox"} ->
+      %Tesla.Env{status: 200, body: File.read!("test/fixtures/image.jpg")}
+    end)
+
+    clear_config(:mrf_steal_emoji, hosts: ["example.org"], size_limit: 284_468)
+
+    refute "fired:fox" in installed()
+    refute File.exists?(path)
+
+    assert {:ok, _message} = StealEmojiPolicy.filter(message)
+
+    refute "fired:fox" in installed()
+    refute File.exists?(fullpath)
+  end
+
   test "reject regex shortcode", %{message: message} do
     refute "firedfox" in installed()
 
@@ -171,5 +223,74 @@ defmodule Pleroma.Web.ActivityPub.MRF.StealEmojiPolicyTest do
     refute "firedfox" in installed()
   end
 
+  test "accepts valid alphanum shortcodes", %{path: path} do
+    message = %{
+      "type" => "Create",
+      "object" => %{
+        "emoji" => [{"fire1fox", "https://example.org/emoji/fire1fox.png"}],
+        "actor" => "https://example.org/users/admin"
+      }
+    }
+
+    Tesla.Mock.mock(fn %{method: :get, url: "https://example.org/emoji/fire1fox.png"} ->
+      %Tesla.Env{status: 200, body: File.read!("test/fixtures/image.jpg")}
+    end)
+
+    clear_config(:mrf_steal_emoji, hosts: ["example.org"], size_limit: 284_468)
+
+    refute "fire1fox" in installed()
+    refute File.exists?(path)
+
+    assert {:ok, _message} = StealEmojiPolicy.filter(message)
+
+    assert "fire1fox" in installed()
+  end
+
+  test "accepts valid shortcodes with underscores", %{path: path} do
+    message = %{
+      "type" => "Create",
+      "object" => %{
+        "emoji" => [{"fire_fox", "https://example.org/emoji/fire_fox.png"}],
+        "actor" => "https://example.org/users/admin"
+      }
+    }
+
+    Tesla.Mock.mock(fn %{method: :get, url: "https://example.org/emoji/fire_fox.png"} ->
+      %Tesla.Env{status: 200, body: File.read!("test/fixtures/image.jpg")}
+    end)
+
+    clear_config(:mrf_steal_emoji, hosts: ["example.org"], size_limit: 284_468)
+
+    refute "fire_fox" in installed()
+    refute File.exists?(path)
+
+    assert {:ok, _message} = StealEmojiPolicy.filter(message)
+
+    assert "fire_fox" in installed()
+  end
+
+  test "accepts valid shortcodes with hyphens", %{path: path} do
+    message = %{
+      "type" => "Create",
+      "object" => %{
+        "emoji" => [{"fire-fox", "https://example.org/emoji/fire-fox.png"}],
+        "actor" => "https://example.org/users/admin"
+      }
+    }
+
+    Tesla.Mock.mock(fn %{method: :get, url: "https://example.org/emoji/fire-fox.png"} ->
+      %Tesla.Env{status: 200, body: File.read!("test/fixtures/image.jpg")}
+    end)
+
+    clear_config(:mrf_steal_emoji, hosts: ["example.org"], size_limit: 284_468)
+
+    refute "fire-fox" in installed()
+    refute File.exists?(path)
+
+    assert {:ok, _message} = StealEmojiPolicy.filter(message)
+
+    assert "fire-fox" in installed()
+  end
+
   defp installed, do: Emoji.get_all() |> Enum.map(fn {k, _} -> k end)
 end