Max media attachment count

Signed-off-by: marcin mikołajczak <git@mkljczk.pl>

config/config.exs

@@ -259,7 +259,8 @@
   privileged_staff: false,
   max_endorsed_users: 20,
   birthday_required: false,
-  birthday_min_age: 0
+  birthday_min_age: 0,
+  max_media_attachments: 1_000
 
 config :pleroma, :welcome,
   direct_message: [

config/description.exs

@@ -552,6 +552,14 @@
           100_000
         ]
       },
+      %{
+        key: :max_media_attachments,
+        type: :integer,
+        description: "Maximum number of post media attachments",
+        suggestions: [
+          1_000_000
+        ]
+      },
       %{
         key: :upload_limit,
         type: :integer,

lib/pleroma/web/common_api/activity_draft.ex

@@ -112,7 +112,12 @@ defp full_payload(%{status: status, summary: summary} = draft) do
 
   defp attachments(%{params: params} = draft) do
     attachments = Utils.attachments_from_ids(params)
-    %__MODULE__{draft | attachments: attachments}
+    draft = %__MODULE__{draft | attachments: attachments}
+
+    case Utils.validate_attachments_count(attachments) do
+      :ok -> draft
+      {:error, message} -> add_error(draft, message)
+    end
   end
 
   defp in_reply_to(%{params: %{in_reply_to_status_id: ""}} = draft), do: draft

lib/pleroma/web/common_api/utils.ex

@@ -492,4 +492,19 @@ def validate_character_limit(full_payload, _attachments) do
       {:error, dgettext("errors", "The status is over the character limit")}
     end
   end
+
+  def validate_attachments_count([] = _attachments) do
+    :ok
+  end
+
+  def validate_attachments_count(attachments) do
+    limit = Config.get([:instance, :max_media_attachments])
+    count = length(attachments)
+
+    if count <= limit do
+      :ok
+    else
+      {:error, dgettext("errors", "Too many attachments")}
+    end
+  end
 end

lib/pleroma/web/mastodon_api/views/instance_view.ex

@@ -31,6 +31,7 @@ def render("show.json", _) do
       approval_required: Keyword.get(instance, :account_approval_required),
       # Extra (not present in Mastodon):
       max_toot_chars: Keyword.get(instance, :limit),
+      max_media_attachments: Keyword.get(instance, :max_media_attachments),
       poll_limits: Keyword.get(instance, :poll_limits),
       upload_limit: Keyword.get(instance, :upload_limit),
       avatar_upload_limit: Keyword.get(instance, :avatar_upload_limit),

test/pleroma/web/common_api_test.exs

@@ -683,6 +683,32 @@ test "it validates character limits are correctly enforced" do
       assert {:ok, _activity} = CommonAPI.post(user, %{status: "12345"})
     end
 
+    test "it validates media attachment limits are correctly enforced" do
+      clear_config([:instance, :max_media_attachments], 4)
+
+      user = insert(:user)
+
+      file = %Plug.Upload{
+        content_type: "image/jpeg",
+        path: Path.absname("test/fixtures/image.jpg"),
+        filename: "an_image.jpg"
+      }
+
+      {:ok, upload} = ActivityPub.upload(file, actor: user.ap_id)
+
+      assert {:error, "Too many attachments"} =
+               CommonAPI.post(user, %{
+                 status: "",
+                 media_ids: List.duplicate(upload.id, 5)
+               })
+
+      assert {:ok, _activity} =
+               CommonAPI.post(user, %{
+                 status: "",
+                 media_ids: [upload.id]
+               })
+    end
+
     test "it can handle activities that expire" do
       user = insert(:user)