8 files changed, 148 insertions, 231 deletions

diff --git a/lib/pleroma/web/activity_pub/activity_pub.ex b/lib/pleroma/web/activity_pub/activity_pub.ex
index fcc3ce728..4955243ab 100644
--- a/lib/pleroma/web/activity_pub/activity_pub.ex
+++ b/lib/pleroma/web/activity_pub/activity_pub.ex
@@ -356,56 +356,6 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
-  @spec unreact_with_emoji(User.t(), String.t(), keyword()) ::
-          {:ok, Activity.t(), Object.t()} | {:error, any()}
-  def unreact_with_emoji(user, reaction_id, options \\ []) do
-    with {:ok, result} <-
-           Repo.transaction(fn -> do_unreact_with_emoji(user, reaction_id, options) end) do
-      result
-    end
-  end
-
-  defp do_unreact_with_emoji(user, reaction_id, options) do
-    with local <- Keyword.get(options, :local, true),
-         activity_id <- Keyword.get(options, :activity_id, nil),
-         user_ap_id <- user.ap_id,
-         %Activity{actor: ^user_ap_id} = reaction_activity <- Activity.get_by_ap_id(reaction_id),
-         object <- Object.normalize(reaction_activity),
-         unreact_data <- make_undo_data(user, reaction_activity, activity_id),
-         {:ok, activity} <- insert(unreact_data, local),
-         {:ok, object} <- remove_emoji_reaction_from_object(reaction_activity, object),
-         _ <- notify_and_stream(activity),
-         :ok <- maybe_federate(activity) do
-      {:ok, activity, object}
-    else
-      {:error, error} -> Repo.rollback(error)
-    end
-  end
-
-  @spec unlike(User.t(), Object.t(), String.t() | nil, boolean()) ::
-          {:ok, Activity.t(), Activity.t(), Object.t()} | {:ok, Object.t()} | {:error, any()}
-  def unlike(%User{} = actor, %Object{} = object, activity_id \\ nil, local \\ true) do
-    with {:ok, result} <-
-           Repo.transaction(fn -> do_unlike(actor, object, activity_id, local) end) do
-      result
-    end
-  end
-
-  defp do_unlike(actor, object, activity_id, local) do
-    with %Activity{} = like_activity <- get_existing_like(actor.ap_id, object),
-         unlike_data <- make_unlike_data(actor, like_activity, activity_id),
-         {:ok, unlike_activity} <- insert(unlike_data, local),
-         {:ok, _activity} <- Repo.delete(like_activity),
-         {:ok, object} <- remove_like_from_object(like_activity, object),
-         _ <- notify_and_stream(unlike_activity),
-         :ok <- maybe_federate(unlike_activity) do
-      {:ok, unlike_activity, like_activity, object}
-    else
-      nil -> {:ok, object}
-      {:error, error} -> Repo.rollback(error)
-    end
-  end
-
   @spec announce(User.t(), Object.t(), String.t() | nil, boolean(), boolean()) ::
           {:ok, Activity.t(), Object.t()} | {:error, any()}
   def announce(
@@ -436,35 +386,6 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
-  @spec unannounce(User.t(), Object.t(), String.t() | nil, boolean()) ::
-          {:ok, Activity.t(), Object.t()} | {:ok, Object.t()} | {:error, any()}
-  def unannounce(
-        %User{} = actor,
-        %Object{} = object,
-        activity_id \\ nil,
-        local \\ true
-      ) do
-    with {:ok, result} <-
-           Repo.transaction(fn -> do_unannounce(actor, object, activity_id, local) end) do
-      result
-    end
-  end
-
-  defp do_unannounce(actor, object, activity_id, local) do
-    with %Activity{} = announce_activity <- get_existing_announce(actor.ap_id, object),
-         unannounce_data <- make_unannounce_data(actor, announce_activity, activity_id),
-         {:ok, unannounce_activity} <- insert(unannounce_data, local),
-         _ <- notify_and_stream(unannounce_activity),
-         :ok <- maybe_federate(unannounce_activity),
-         {:ok, _activity} <- Repo.delete(announce_activity),
-         {:ok, object} <- remove_announce_from_object(announce_activity, object) do
-      {:ok, unannounce_activity, object}
-    else
-      nil -> {:ok, object}
-      {:error, error} -> Repo.rollback(error)
-    end
-  end
-
   @spec follow(User.t(), User.t(), String.t() | nil, boolean()) ::
           {:ok, Activity.t()} | {:error, any()}
   def follow(follower, followed, activity_id \\ nil, local \\ true) do
@@ -537,28 +458,6 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
     end
   end
 
-  @spec unblock(User.t(), User.t(), String.t() | nil, boolean()) ::
-          {:ok, Activity.t()} | {:error, any()} | nil
-  def unblock(blocker, blocked, activity_id \\ nil, local \\ true) do
-    with {:ok, result} <-
-           Repo.transaction(fn -> do_unblock(blocker, blocked, activity_id, local) end) do
-      result
-    end
-  end
-
-  defp do_unblock(blocker, blocked, activity_id, local) do
-    with %Activity{} = block_activity <- fetch_latest_block(blocker, blocked),
-         unblock_data <- make_unblock_data(blocker, blocked, block_activity, activity_id),
-         {:ok, activity} <- insert(unblock_data, local),
-         _ <- notify_and_stream(activity),
-         :ok <- maybe_federate(activity) do
-      {:ok, activity}
-    else
-      nil -> nil
-      {:error, error} -> Repo.rollback(error)
-    end
-  end
-
   @spec flag(map()) :: {:ok, Activity.t()} | {:error, any()}
   def flag(
         %{
diff --git a/lib/pleroma/web/activity_pub/builder.ex b/lib/pleroma/web/activity_pub/builder.ex
index d130176cf..f6544d3f5 100644
--- a/lib/pleroma/web/activity_pub/builder.ex
+++ b/lib/pleroma/web/activity_pub/builder.ex
@@ -22,6 +22,19 @@ defmodule Pleroma.Web.ActivityPub.Builder do
     end
   end
 
+  @spec undo(User.t(), Activity.t()) :: {:ok, map(), keyword()}
+  def undo(actor, object) do
+    {:ok,
+     %{
+       "id" => Utils.generate_activity_id(),
+       "actor" => actor.ap_id,
+       "type" => "Undo",
+       "object" => object.data["id"],
+       "to" => object.data["to"] || [],
+       "cc" => object.data["cc"] || []
+     }, []}
+  end
+
   @spec delete(User.t(), String.t()) :: {:ok, map(), keyword()}
   def delete(actor, object_id) do
     object = Object.normalize(object_id, false)
diff --git a/lib/pleroma/web/activity_pub/object_validator.ex b/lib/pleroma/web/activity_pub/object_validator.ex
index e51a8e0a8..549e5e761 100644
--- a/lib/pleroma/web/activity_pub/object_validator.ex
+++ b/lib/pleroma/web/activity_pub/object_validator.ex
@@ -15,10 +15,21 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidator do
   alias Pleroma.Web.ActivityPub.ObjectValidators.EmojiReactValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.LikeValidator
   alias Pleroma.Web.ActivityPub.ObjectValidators.Types
+  alias Pleroma.Web.ActivityPub.ObjectValidators.UndoValidator
 
   @spec validate(map(), keyword()) :: {:ok, map(), keyword()} | {:error, any()}
   def validate(object, meta)
 
+  def validate(%{"type" => "Undo"} = object, meta) do
+    with {:ok, object} <-
+           object
+           |> UndoValidator.cast_and_validate()
+           |> Ecto.Changeset.apply_action(:insert) do
+      object = stringify_keys(object)
+      {:ok, object, meta}
+    end
+  end
+
   def validate(%{"type" => "Delete"} = object, meta) do
     with cng <- DeleteValidator.cast_and_validate(object),
          do_not_federate <- DeleteValidator.do_not_federate?(cng),
diff --git a/lib/pleroma/web/activity_pub/object_validators/common_validations.ex b/lib/pleroma/web/activity_pub/object_validators/common_validations.ex
index 4e6ee2034..aeef31945 100644
--- a/lib/pleroma/web/activity_pub/object_validators/common_validations.ex
+++ b/lib/pleroma/web/activity_pub/object_validators/common_validations.ex
@@ -5,6 +5,7 @@
 defmodule Pleroma.Web.ActivityPub.ObjectValidators.CommonValidations do
   import Ecto.Changeset
 
+  alias Pleroma.Activity
   alias Pleroma.Object
   alias Pleroma.User
 
@@ -47,7 +48,7 @@ defmodule Pleroma.Web.ActivityPub.ObjectValidators.CommonValidations do
 
     cng
     |> validate_change(field_name, fn field_name, object_id ->
-      object = Object.get_cached_by_ap_id(object_id)
+      object = Object.get_cached_by_ap_id(object_id) || Activity.get_by_ap_id(object_id)
 
       cond do
         !object ->
diff --git a/lib/pleroma/web/activity_pub/object_validators/undo_validator.ex b/lib/pleroma/web/activity_pub/object_validators/undo_validator.ex
new file mode 100644
index 000000000..d0ba418e8
--- /dev/null
+++ b/lib/pleroma/web/activity_pub/object_validators/undo_validator.ex
@@ -0,0 +1,62 @@
+# 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.UndoValidator do
+  use Ecto.Schema
+
+  alias Pleroma.Activity
+  alias Pleroma.Web.ActivityPub.ObjectValidators.Types
+
+  import Ecto.Changeset
+  import Pleroma.Web.ActivityPub.ObjectValidators.CommonValidations
+
+  @primary_key false
+
+  embedded_schema do
+    field(:id, Types.ObjectID, primary_key: true)
+    field(:type, :string)
+    field(:object, Types.ObjectID)
+    field(:actor, Types.ObjectID)
+    field(:to, {:array, :string}, default: [])
+    field(:cc, {:array, :string}, default: [])
+  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))
+  end
+
+  def validate_data(data_cng) do
+    data_cng
+    |> validate_inclusion(:type, ["Undo"])
+    |> validate_required([:id, :type, :object, :actor, :to, :cc])
+    |> validate_actor_presence()
+    |> validate_object_presence()
+    |> validate_undo_rights()
+  end
+
+  def validate_undo_rights(cng) do
+    actor = get_field(cng, :actor)
+    object = get_field(cng, :object)
+
+    with %Activity{data: %{"actor" => object_actor}} <- Activity.get_by_ap_id(object),
+         true <- object_actor != actor do
+      cng
+      |> add_error(:actor, "not the same as object actor")
+    else
+      _ -> cng
+    end
+  end
+end
diff --git a/lib/pleroma/web/activity_pub/side_effects.ex b/lib/pleroma/web/activity_pub/side_effects.ex
index 8e5586e88..bfc2ab845 100644
--- a/lib/pleroma/web/activity_pub/side_effects.ex
+++ b/lib/pleroma/web/activity_pub/side_effects.ex
@@ -5,8 +5,10 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
   liked object, a `Follow` activity will add the user to the follower
   collection, and so on.
   """
+  alias Pleroma.Activity
   alias Pleroma.Notification
   alias Pleroma.Object
+  alias Pleroma.Repo
   alias Pleroma.User
   alias Pleroma.Web.ActivityPub.ActivityPub
   alias Pleroma.Web.ActivityPub.Utils
@@ -25,6 +27,13 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
     {:ok, object, meta}
   end
 
+  def handle(%{data: %{"type" => "Undo", "object" => undone_object}} = object, meta) do
+    with undone_object <- Activity.get_by_ap_id(undone_object),
+         :ok <- handle_undoing(undone_object) do
+      {:ok, object, meta}
+    end
+  end
+
   # Tasks this handles:
   # - Add reaction to object
   # - Set up notification
@@ -84,4 +93,41 @@ defmodule Pleroma.Web.ActivityPub.SideEffects do
   def handle(object, meta) do
     {:ok, object, meta}
   end
+
+  def handle_undoing(%{data: %{"type" => "Like"}} = object) do
+    with %Object{} = liked_object <- Object.get_by_ap_id(object.data["object"]),
+         {:ok, _} <- Utils.remove_like_from_object(object, liked_object),
+         {:ok, _} <- Repo.delete(object) do
+      :ok
+    end
+  end
+
+  def handle_undoing(%{data: %{"type" => "EmojiReact"}} = object) do
+    with %Object{} = reacted_object <- Object.get_by_ap_id(object.data["object"]),
+         {:ok, _} <- Utils.remove_emoji_reaction_from_object(object, reacted_object),
+         {:ok, _} <- Repo.delete(object) do
+      :ok
+    end
+  end
+
+  def handle_undoing(%{data: %{"type" => "Announce"}} = object) do
+    with %Object{} = liked_object <- Object.get_by_ap_id(object.data["object"]),
+         {:ok, _} <- Utils.remove_announce_from_object(object, liked_object),
+         {:ok, _} <- Repo.delete(object) do
+      :ok
+    end
+  end
+
+  def handle_undoing(
+        %{data: %{"type" => "Block", "actor" => blocker, "object" => blocked}} = object
+      ) do
+    with %User{} = blocker <- User.get_cached_by_ap_id(blocker),
+         %User{} = blocked <- User.get_cached_by_ap_id(blocked),
+         {:ok, _} <- User.unblock(blocker, blocked),
+         {:ok, _} <- Repo.delete(object) do
+      :ok
+    end
+  end
+
+  def handle_undoing(object), do: {:error, ["don't know how to handle", object]}
 end
diff --git a/lib/pleroma/web/activity_pub/transmogrifier.ex b/lib/pleroma/web/activity_pub/transmogrifier.ex
index ee6fc31ce..be7b57f13 100644
--- a/lib/pleroma/web/activity_pub/transmogrifier.ex
+++ b/lib/pleroma/web/activity_pub/transmogrifier.ex
@@ -726,25 +726,6 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   def handle_incoming(
         %{
           "type" => "Undo",
-          "object" => %{"type" => "Announce", "object" => object_id},
-          "actor" => _actor,
-          "id" => id
-        } = data,
-        _options
-      ) do
-    with actor <- Containment.get_actor(data),
-         {:ok, %User{} = actor} <- User.get_or_fetch_by_ap_id(actor),
-         {:ok, object} <- get_obj_helper(object_id),
-         {:ok, activity, _} <- ActivityPub.unannounce(actor, object, id, false) do
-      {:ok, activity}
-    else
-      _e -> :error
-    end
-  end
-
-  def handle_incoming(
-        %{
-          "type" => "Undo",
           "object" => %{"type" => "Follow", "object" => followed},
           "actor" => follower,
           "id" => id
@@ -764,39 +745,29 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
   def handle_incoming(
         %{
           "type" => "Undo",
-          "object" => %{"type" => "EmojiReact", "id" => reaction_activity_id},
-          "actor" => _actor,
-          "id" => id
+          "object" => %{"type" => type}
         } = data,
         _options
-      ) do
-    with actor <- Containment.get_actor(data),
-         {:ok, %User{} = actor} <- User.get_or_fetch_by_ap_id(actor),
-         {:ok, activity, _} <-
-           ActivityPub.unreact_with_emoji(actor, reaction_activity_id,
-             activity_id: id,
-             local: false
-           ) do
+      )
+      when type in ["Like", "EmojiReact", "Announce", "Block"] do
+    with {:ok, activity, _} <- Pipeline.common_pipeline(data, local: false) do
       {:ok, activity}
-    else
-      _e -> :error
     end
   end
 
+  # For Undos that don't have the complete object attached, try to find it in our database.
   def handle_incoming(
         %{
           "type" => "Undo",
-          "object" => %{"type" => "Block", "object" => blocked},
-          "actor" => blocker,
-          "id" => id
-        } = _data,
-        _options
-      ) do
-    with %User{local: true} = blocked <- User.get_cached_by_ap_id(blocked),
-         {:ok, %User{} = blocker} <- User.get_or_fetch_by_ap_id(blocker),
-         {:ok, activity} <- ActivityPub.unblock(blocker, blocked, id, false) do
-      User.unblock(blocker, blocked)
-      {:ok, activity}
+          "object" => object
+        } = activity,
+        options
+      )
+      when is_binary(object) do
+    with %Activity{data: data} <- Activity.get_by_ap_id(object) do
+      activity
+      |> Map.put("object", data)
+      |> handle_incoming(options)
     else
       _e -> :error
     end
@@ -819,43 +790,6 @@ defmodule Pleroma.Web.ActivityPub.Transmogrifier do
 
   def handle_incoming(
         %{
-          "type" => "Undo",
-          "object" => %{"type" => "Like", "object" => object_id},
-          "actor" => _actor,
-          "id" => id
-        } = data,
-        _options
-      ) do
-    with actor <- Containment.get_actor(data),
-         {:ok, %User{} = actor} <- User.get_or_fetch_by_ap_id(actor),
-         {:ok, object} <- get_obj_helper(object_id),
-         {:ok, activity, _, _} <- ActivityPub.unlike(actor, object, id, false) do
-      {:ok, activity}
-    else
-      _e -> :error
-    end
-  end
-
-  # For Undos that don't have the complete object attached, try to find it in our database.
-  def handle_incoming(
-        %{
-          "type" => "Undo",
-          "object" => object
-        } = activity,
-        options
-      )
-      when is_binary(object) do
-    with %Activity{data: data} <- Activity.get_by_ap_id(object) do
-      activity
-      |> Map.put("object", data)
-      |> handle_incoming(options)
-    else
-      _e -> :error
-    end
-  end
-
-  def handle_incoming(
-        %{
           "type" => "Move",
           "actor" => origin_actor,
           "object" => origin_actor,
diff --git a/lib/pleroma/web/activity_pub/utils.ex b/lib/pleroma/web/activity_pub/utils.ex
index 1a3b0b3c1..09b80fa57 100644
--- a/lib/pleroma/web/activity_pub/utils.ex
+++ b/lib/pleroma/web/activity_pub/utils.ex
@@ -562,45 +562,6 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> maybe_put("id", activity_id)
   end
 
-  @doc """
-  Make unannounce activity data for the given actor and object
-  """
-  def make_unannounce_data(
-        %User{ap_id: ap_id} = user,
-        %Activity{data: %{"context" => context, "object" => object}} = activity,
-        activity_id
-      ) do
-    object = Object.normalize(object)
-
-    %{
-      "type" => "Undo",
-      "actor" => ap_id,
-      "object" => activity.data,
-      "to" => [user.follower_address, object.data["actor"]],
-      "cc" => [Pleroma.Constants.as_public()],
-      "context" => context
-    }
-    |> maybe_put("id", activity_id)
-  end
-
-  def make_unlike_data(
-        %User{ap_id: ap_id} = user,
-        %Activity{data: %{"context" => context, "object" => object}} = activity,
-        activity_id
-      ) do
-    object = Object.normalize(object)
-
-    %{
-      "type" => "Undo",
-      "actor" => ap_id,
-      "object" => activity.data,
-      "to" => [user.follower_address, object.data["actor"]],
-      "cc" => [Pleroma.Constants.as_public()],
-      "context" => context
-    }
-    |> maybe_put("id", activity_id)
-  end
-
   def make_undo_data(
         %User{ap_id: actor, follower_address: follower_address},
         %Activity{
@@ -688,16 +649,6 @@ defmodule Pleroma.Web.ActivityPub.Utils do
     |> maybe_put("id", activity_id)
   end
 
-  def make_unblock_data(blocker, blocked, block_activity, activity_id) do
-    %{
-      "type" => "Undo",
-      "actor" => blocker.ap_id,
-      "to" => [blocked.ap_id],
-      "object" => block_activity.data
-    }
-    |> maybe_put("id", activity_id)
-  end
-
   #### Create-related helpers
 
   def make_create_data(params, additional) do