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diff --git a/changelog.d/refetch-containment.security b/changelog.d/refetch-containment.security
new file mode 100644
index 000000000..bfd118ab1
--- /dev/null
+++ b/changelog.d/refetch-containment.security
@@ -0,0 +1 @@
+Do not let a refetched object (such as a poll) change its id or author
diff --git a/lib/pleroma/object/fetcher.ex b/lib/pleroma/object/fetcher.ex
index 8a6f5561f..706ee317c 100644
--- a/lib/pleroma/object/fetcher.ex
+++ b/lib/pleroma/object/fetcher.ex
@@ -11,6 +11,7 @@ defmodule Pleroma.Object.Fetcher do
alias Pleroma.Web.ActivityPub.InternalFetchActor
alias Pleroma.Web.ActivityPub.MRF
alias Pleroma.Web.ActivityPub.ObjectValidator
+ alias Pleroma.Web.ActivityPub.ObjectValidators.CommonFixes
alias Pleroma.Web.ActivityPub.Pipeline
alias Pleroma.Web.ActivityPub.Transmogrifier
alias Pleroma.Web.Federator
@@ -46,9 +47,14 @@ defmodule Pleroma.Object.Fetcher do
end
end
- def refetch_object(%Object{data: %{"id" => id}} = object) do
+ # The stored id is canonical, so the refetch must not redirect, and the
+ # remote must not swap in another object or author.
+ # Based on Akkoma 9061d148b and fee57eb37.
+ def refetch_object(%Object{data: %{"id" => id} = data} = object) do
with {:local, false} <- {:local, Object.local?(object)},
- {:ok, new_data} <- fetch_and_contain_remote_object_from_id(id),
+ {:ok, new_data} <- fetch_and_contain(id, true),
+ {:id, true} <- {:id, new_data["id"] == id},
+ {:actor, true} <- {:actor, actor_of(new_data) == actor_of(data)},
{:ok, object} <- reinject_object(object, new_data) do
{:ok, object}
else
@@ -57,6 +63,8 @@ defmodule Pleroma.Object.Fetcher do
end
end
+ defp actor_of(data), do: CommonFixes.fix_actor(data)["actor"]
+
@typep fetcher_errors ::
:error | :reject | :allowed_depth | :fetch | :containment | :transmogrifier
diff --git a/test/pleroma/object/fetcher_test.exs b/test/pleroma/object/fetcher_test.exs
index 411f69bea..c9c4890cd 100644
--- a/test/pleroma/object/fetcher_test.exs
+++ b/test/pleroma/object/fetcher_test.exs
@@ -465,6 +465,60 @@ defmodule Pleroma.Object.FetcherTest do
%{object1: local_object1, object2: local_object2}
end
+ test "it rejects a refetched object whose actor changed", %{object1: object1} do
+ insert(:user, ap_id: "https://mastodon.social/users/someone_else")
+ {:ok, o} = Object.create(object1)
+
+ mock(fn %{method: :get, url: "https://mastodon.social/1"} ->
+ %Tesla.Env{
+ status: 200,
+ headers: [{"content-type", "application/activity+json"}],
+ body:
+ object1
+ |> Map.merge(%{
+ "actor" => "https://mastodon.social/users/someone_else",
+ "attributedTo" => "https://mastodon.social/users/someone_else",
+ "content" => "hijacked"
+ })
+ |> Jason.encode!()
+ }
+ end)
+
+ assert {:error, _} = Fetcher.refetch_object(o)
+ assert Object.get_by_ap_id("https://mastodon.social/1").data["content"] == "test 1"
+ end
+
+ test "it rejects a refetched object whose id changed", %{object1: object1} do
+ {:ok, o} = Object.create(object1)
+
+ mock(fn %{method: :get, url: "https://mastodon.social/1"} ->
+ %Tesla.Env{
+ status: 200,
+ url: "https://mastodon.social/2",
+ headers: [{"content-type", "application/activity+json"}],
+ body: object1 |> Map.put("id", "https://mastodon.social/2") |> Jason.encode!()
+ }
+ end)
+
+ assert {:error, _} = Fetcher.refetch_object(o)
+ end
+
+ test "it rejects a refetched object whose id differs only by a trailing slash", %{
+ object1: object1
+ } do
+ {:ok, o} = Object.create(object1)
+
+ mock(fn %{method: :get, url: "https://mastodon.social/1"} ->
+ %Tesla.Env{
+ status: 200,
+ headers: [{"content-type", "application/activity+json"}],
+ body: object1 |> Map.put("id", "https://mastodon.social/1/") |> Jason.encode!()
+ }
+ end)
+
+ assert {:error, _} = Fetcher.refetch_object(o)
+ end
+
test "it keeps formerRepresentations if remote does not have this attr", %{object1: object1} do
full_object1 =
object1

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