FollowValidator: Add basic validation.

lib/pleroma/web/activity_pub/builder.ex

@@ -14,6 +14,19 @@ defmodule Pleroma.Web.ActivityPub.Builder do
 
   require Pleroma.Constants
 
+  @spec follow(User.t(), User.t()) :: {:ok, map(), keyword()}
+  def follow(follower, followed) do
+    data = %{
+      "id" => Utils.generate_activity_id(),
+      "actor" => follower.ap_id,
+      "type" => "Follow",
+      "object" => followed.ap_id,
+      "to" => [followed.ap_id]
+    }
+
+    {:ok, data, []}
+  end
+
   @spec emoji_react(User.t(), Object.t(), String.t()) :: {:ok, map(), keyword()}
   def emoji_react(actor, object, emoji) do
     with {:ok, data, meta} <- object_action(actor, object) do

lib/pleroma/web/activity_pub/object_validator.ex

@@ -18,6 +18,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
   alias Pleroma.Web.ActivityPub.ObjectValidators.CreateChatMessageValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.DeleteValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.EmojiReactValidator
+  alias Pleroma.Web.ActivityPub.ObjectValidators.FollowValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.LikeValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.UndoValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.UpdateValidator
@@ -25,6 +26,16 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
   @spec validate(map(), keyword()) :: {:ok, map(), keyword()} | {:error, any()}
   def validate(object, meta)
 
+  def validate(%{"type" => "Follow"} = object, meta) do
+    with {:ok, object} <-
+           object
+           |> FollowValidator.cast_and_validate()
+           |> Ecto.Changeset.apply_action(:insert) do
+      object = stringify_keys(object)
+      {:ok, object, meta}
+    end
+  end
+
   def validate(%{"type" => "Block"} = block_activity, meta) do
     with {:ok, block_activity} <-
            block_activity

lib/pleroma/web/activity_pub/object_validators/follow_validator.ex

@@ -0,0 +1,42 @@
+# 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.FollowValidator do
+  use Ecto.Schema
+
+  alias Pleroma.EctoType.ActivityPub.ObjectValidators
+
+  import Ecto.Changeset
+  import Pleroma.Web.ActivityPub.ObjectValidators.CommonValidations
+
+  @primary_key false
+
+  embedded_schema do
+    field(:id, ObjectValidators.ObjectID, primary_key: true)
+    field(:type, :string)
+    field(:actor, ObjectValidators.ObjectID)
+    field(:to, ObjectValidators.Recipients, default: [])
+    field(:cc, ObjectValidators.Recipients, default: [])
+    field(:object, ObjectValidators.ObjectID)
+  end
+
+  def cast_data(data) do
+    %__MODULE__{}
+    |> cast(data, __schema__(:fields))
+  end
+
+  def validate_data(cng) do
+    cng
+    |> validate_required([:id, :type, :actor, :to, :cc, :object])
+    |> validate_inclusion(:type, ["Follow"])
+    |> validate_actor_presence()
+    |> validate_actor_presence(field_name: :object)
+  end
+
+  def cast_and_validate(data) do
+    data
+    |> cast_data
+    |> validate_data
+  end
+end

test/web/activity_pub/object_validators/follow_validation_test.exs

@@ -0,0 +1,26 @@
+# 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.FollowValidationTest do
+  use Pleroma.DataCase
+
+  alias Pleroma.Web.ActivityPub.Builder
+  alias Pleroma.Web.ActivityPub.ObjectValidator
+
+  import Pleroma.Factory
+
+  describe "Follows" do
+    setup do
+      follower = insert(:user)
+      followed = insert(:user)
+
+      {:ok, valid_follow, []} = Builder.follow(follower, followed)
+      %{follower: follower, followed: followed, valid_follow: valid_follow}
+    end
+
+    test "validates a basic follow object", %{valid_follow: valid_follow} do
+      assert {:ok, _follow, []} = ObjectValidator.validate(valid_follow, [])
+    end
+  end
+end