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diff --git a/lib/pleroma/web/activity_pub/object_validators/announce_validator.ex b/lib/pleroma/web/activity_pub/object_validators/announce_validator.ex
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+++ b/lib/pleroma/web/activity_pub/object_validators/announce_validator.ex
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+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.ActivityPub.ObjectValidators.AnnounceValidator do
+  use Ecto.Schema
+
+  alias Pleroma.EctoType.ActivityPub.ObjectValidators
+  alias Pleroma.Object
+  alias Pleroma.User
+  alias Pleroma.Web.ActivityPub.Utils
+  alias Pleroma.Web.ActivityPub.Visibility
+
+  import Ecto.Changeset
+  import Pleroma.Web.ActivityPub.ObjectValidators.CommonValidations
+
+  require Pleroma.Constants
+
+  @primary_key false
+
+  embedded_schema do
+    field(:id, ObjectValidators.ObjectID, primary_key: true)
+    field(:type, :string)
+    field(:object, ObjectValidators.ObjectID)
+    field(:actor, ObjectValidators.ObjectID)
+    field(:context, :string, autogenerate: {Utils, :generate_context_id, []})
+    field(:to, ObjectValidators.Recipients, default: [])
+    field(:cc, ObjectValidators.Recipients, default: [])
+    field(:published, ObjectValidators.DateTime)
+  end
+
+  def cast_and_validate(data) do
+    data
+    |> cast_data()
+    |> validate_data()
+  end
+
+  def cast_data(data) do
+    %__MODULE__{}
+    |> changeset(data)
+  end
+
+  def changeset(struct, data) do
+    struct
+    |> cast(data, __schema__(:fields))
+    |> fix_after_cast()
+  end
+
+  def fix_after_cast(cng) do
+    cng
+  end
+
+  def validate_data(data_cng) do
+    data_cng
+    |> validate_inclusion(:type, ["Announce"])
+    |> validate_required([:id, :type, :object, :actor, :to, :cc])
+    |> validate_actor_presence()
+    |> validate_object_presence()
+    |> validate_existing_announce()
+    |> validate_announcable()
+  end
+
+  def validate_announcable(cng) do
+    with actor when is_binary(actor) <- get_field(cng, :actor),
+         object when is_binary(object) <- get_field(cng, :object),
+         %User{} = actor <- User.get_cached_by_ap_id(actor),
+         %Object{} = object <- Object.get_cached_by_ap_id(object),
+         false <- Visibility.is_public?(object) do
+      same_actor = object.data["actor"] == actor.ap_id
+      is_public = Pleroma.Constants.as_public() in (get_field(cng, :to) ++ get_field(cng, :cc))
+
+      cond do
+        same_actor && is_public ->
+          cng
+          |> add_error(:actor, "can not announce this object publicly")
+
+        !same_actor ->
+          cng
+          |> add_error(:actor, "can not announce this object")
+
+        true ->
+          cng
+      end
+    else
+      _ -> cng
+    end
+  end
+
+  def validate_existing_announce(cng) do
+    actor = get_field(cng, :actor)
+    object = get_field(cng, :object)
+
+    if actor && object && Utils.get_existing_announce(actor, %{data: %{"id" => object}}) do
+      cng
+      |> add_error(:actor, "already announced this object")
+      |> add_error(:object, "already announced by this actor")
+    else
+      cng
+    end
+  end
+end