From 591c82620eeb74a012d4614b9f16db74a7fd84f9 Mon Sep 17 00:00:00 2001
From: William Pitcock <nenolod@dereferenced.org>
Date: Mon, 18 Jun 2018 04:33:41 +0000
Subject: [PATCH] activitypub: filter destination list for announce activities
 differently than normal (closes #164)

---
 lib/pleroma/user.ex                          | 28 +++++++++++++++-----
 lib/pleroma/web/activity_pub/activity_pub.ex | 18 +++++++++++++
 2 files changed, 40 insertions(+), 6 deletions(-)

diff --git a/lib/pleroma/user.ex b/lib/pleroma/user.ex
index b27397e13..856f27e10 100644
--- a/lib/pleroma/user.ex
+++ b/lib/pleroma/user.ex
@@ -449,13 +449,29 @@ def update_follower_count(%User{} = user) do
     update_and_set_cache(cs)
   end
 
+  def get_notified_from_activity_query(to) do
+    from(
+      u in User,
+      where: u.ap_id in ^to,
+      where: u.local == true
+    )
+  end
+
+  def get_notified_from_activity(%Activity{recipients: to, data: %{"type" => "Announce"} = data}) do
+    object = Object.get_by_ap_id(data["object"])
+
+    # ensure that the actor who published the announced object appears only once
+    to =
+      (to ++ [object.data["actor"]])
+      |> Enum.uniq()
+
+    query = get_notified_from_activity_query(to)
+
+    Repo.all(query)
+  end
+
   def get_notified_from_activity(%Activity{recipients: to}) do
-    query =
-      from(
-        u in User,
-        where: u.ap_id in ^to,
-        where: u.local == true
-      )
+    query = get_notified_from_activity_query(to)
 
     Repo.all(query)
   end
diff --git a/lib/pleroma/web/activity_pub/activity_pub.ex b/lib/pleroma/web/activity_pub/activity_pub.ex
index 267427a23..a4b49e73c 100644
--- a/lib/pleroma/web/activity_pub/activity_pub.ex
+++ b/lib/pleroma/web/activity_pub/activity_pub.ex
@@ -12,6 +12,24 @@ defmodule Pleroma.Web.ActivityPub.ActivityPub do
 
   @instance Application.get_env(:pleroma, :instance)
 
+  # For Announce activities, we filter the recipients based on following status for any actors
+  # that match actual users.  See issue #164 for more information about why this is necessary.
+  def get_recipients(%{"type" => "Announce"} = data) do
+    recipients = (data["to"] || []) ++ (data["cc"] || [])
+    actor = User.get_cached_by_ap_id(data["actor"])
+
+    recipients
+    |> Enum.filter(fn recipient ->
+      case User.get_cached_by_ap_id(recipient) do
+        nil ->
+          true
+
+        user ->
+          User.following?(user, actor)
+      end
+    end)
+  end
+
   def get_recipients(data) do
     (data["to"] || []) ++ (data["cc"] || [])
   end