akkoma/lib/pleroma/web/activity_pub/mrf/simple_policy.ex

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# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.ActivityPub.MRF.SimplePolicy do
@moduledoc "Filter activities depending on their origin instance"
@behaviour Pleroma.Web.ActivityPub.MRF.Policy
alias Pleroma.Config
alias Pleroma.FollowingRelationship
alias Pleroma.User
alias Pleroma.Web.ActivityPub.MRF
require Pleroma.Constants
def check_accept(%{host: actor_host} = _actor_info) do
accepts =
instance_list(:accept)
|> MRF.subdomains_regex()
cond do
accepts == [] -> {:ok, nil}
actor_host == Config.get([Pleroma.Web.Endpoint, :url, :host]) -> {:ok, nil}
MRF.subdomain_match?(accepts, actor_host) -> {:ok, nil}
true -> {:reject, "[SimplePolicy] host not in accept list"}
end
end
def check_reject(%{host: actor_host} = _actor_info) do
rejects =
instance_list(:reject)
|> MRF.subdomains_regex()
if MRF.subdomain_match?(rejects, actor_host) do
{:reject, "[SimplePolicy] host in reject list"}
else
{:ok, nil}
end
end
defp check_media_removal(
%{host: actor_host} = _actor_info,
%{"type" => type, "object" => %{"attachment" => child_attachment}} = object
)
when type in ["Create", "Update"] and length(child_attachment) > 0 do
media_removal =
instance_list(:media_removal)
|> MRF.subdomains_regex()
object =
if MRF.subdomain_match?(media_removal, actor_host) do
child_object = Map.delete(object["object"], "attachment")
Map.put(object, "object", child_object)
else
object
end
{:ok, object}
end
defp check_media_removal(_actor_info, object), do: {:ok, object}
defp check_media_nsfw(
%{host: actor_host} = _actor_info,
%{
"type" => type,
"object" => %{} = _child_object
} = object
)
when type in ["Create", "Update"] do
media_nsfw =
instance_list(:media_nsfw)
|> MRF.subdomains_regex()
object =
if MRF.subdomain_match?(media_nsfw, actor_host) do
Kernel.put_in(object, ["object", "sensitive"], true)
else
object
end
{:ok, object}
end
defp check_media_nsfw(_actor_info, object), do: {:ok, object}
defp check_ftl_removal(%{host: actor_host} = _actor_info, object) do
timeline_removal =
instance_list(:federated_timeline_removal)
|> MRF.subdomains_regex()
object =
with true <- MRF.subdomain_match?(timeline_removal, actor_host),
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user <- User.get_cached_by_ap_id(object["actor"]),
true <- Pleroma.Constants.as_public() in object["to"] do
to = List.delete(object["to"], Pleroma.Constants.as_public()) ++ [user.follower_address]
cc = List.delete(object["cc"], user.follower_address) ++ [Pleroma.Constants.as_public()]
object
|> Map.put("to", to)
|> Map.put("cc", cc)
else
_ -> object
end
{:ok, object}
end
defp intersection(list1, list2) do
list1 -- list1 -- list2
end
defp check_followers_only(%{host: actor_host} = _actor_info, object) do
followers_only =
instance_list(:followers_only)
|> MRF.subdomains_regex()
object =
with true <- MRF.subdomain_match?(followers_only, actor_host),
user <- User.get_cached_by_ap_id(object["actor"]) do
# Don't use Map.get/3 intentionally, these must not be nil
fixed_to = object["to"] || []
fixed_cc = object["cc"] || []
to = FollowingRelationship.followers_ap_ids(user, fixed_to)
cc = FollowingRelationship.followers_ap_ids(user, fixed_cc)
object
|> Map.put("to", intersection([user.follower_address | to], fixed_to))
|> Map.put("cc", intersection([user.follower_address | cc], fixed_cc))
else
_ -> object
end
{:ok, object}
end
defp check_report_removal(%{host: actor_host} = _actor_info, %{"type" => "Flag"} = object) do
report_removal =
instance_list(:report_removal)
|> MRF.subdomains_regex()
if MRF.subdomain_match?(report_removal, actor_host) do
{:reject, "[SimplePolicy] host in report_removal list"}
else
{:ok, object}
end
end
defp check_report_removal(_actor_info, object), do: {:ok, object}
defp check_avatar_removal(%{host: actor_host} = _actor_info, %{"icon" => _icon} = object) do
avatar_removal =
instance_list(:avatar_removal)
|> MRF.subdomains_regex()
if MRF.subdomain_match?(avatar_removal, actor_host) do
{:ok, Map.delete(object, "icon")}
else
{:ok, object}
end
end
defp check_avatar_removal(_actor_info, object), do: {:ok, object}
defp check_banner_removal(%{host: actor_host} = _actor_info, %{"image" => _image} = object) do
banner_removal =
instance_list(:banner_removal)
|> MRF.subdomains_regex()
if MRF.subdomain_match?(banner_removal, actor_host) do
{:ok, Map.delete(object, "image")}
else
{:ok, object}
end
end
defp check_banner_removal(_actor_info, object), do: {:ok, object}
defp check_background_removal(
%{host: actor_host} = _actor_info,
%{"backgroundUrl" => _bg} = object
) do
background_removal =
instance_list(:background_removal)
|> MRF.subdomains_regex()
if MRF.subdomain_match?(background_removal, actor_host) do
{:ok, Map.delete(object, "backgroundUrl")}
else
{:ok, object}
end
end
defp check_background_removal(_actor_info, object), do: {:ok, object}
defp extract_context_uri(%{"conversation" => "tag:" <> rest}) do
rest
|> String.split(",", parts: 2, trim: true)
|> hd()
|> case do
nil -> nil
hostname -> URI.parse("//" <> hostname)
end
end
defp extract_context_uri(%{"context" => "http" <> _ = context}), do: URI.parse(context)
defp extract_context_uri(_), do: nil
defp check_context(activity) do
uri = extract_context_uri(activity)
with {:uri, true} <- {:uri, Kernel.match?(%URI{}, uri)},
{:ok, _} <- check_accept(uri),
{:ok, _} <- check_reject(uri) do
{:ok, activity}
else
# Can't check.
{:uri, false} -> {:ok, activity}
{:reject, nil} -> {:reject, "[SimplePolicy]"}
{:reject, _} = e -> e
_ -> {:reject, "[SimplePolicy]"}
end
end
defp check_reply_to(%{"object" => %{"inReplyTo" => in_reply_to}} = activity) do
with {:ok, _} <- filter(in_reply_to) do
{:ok, activity}
end
end
defp check_reply_to(activity), do: {:ok, activity}
defp maybe_check_thread(activity) do
if Config.get([:mrf_simple, :handle_threads], true) do
with {:ok, _} <- check_context(activity),
{:ok, _} <- check_reply_to(activity) do
{:ok, activity}
end
else
{:ok, activity}
end
end
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defp check_object(%{"object" => object} = activity) do
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with {:ok, _object} <- filter(object) do
{:ok, activity}
end
end
defp check_object(object), do: {:ok, object}
defp instance_list(config_key) do
Config.get([:mrf_simple, config_key])
|> MRF.instance_list_from_tuples()
end
@impl true
def filter(%{"type" => "Delete", "actor" => actor} = object) do
%{host: actor_host} = URI.parse(actor)
reject_deletes =
instance_list(:reject_deletes)
|> MRF.subdomains_regex()
if MRF.subdomain_match?(reject_deletes, actor_host) do
{:reject, "[SimplePolicy] host in reject_deletes list"}
else
{:ok, object}
end
end
@impl true
def filter(%{"actor" => actor} = object) do
actor_info = URI.parse(actor)
with {:ok, _} <- check_accept(actor_info),
{:ok, _} <- check_reject(actor_info),
{:ok, object} <- check_media_removal(actor_info, object),
{:ok, object} <- check_media_nsfw(actor_info, object),
{:ok, object} <- check_ftl_removal(actor_info, object),
{:ok, object} <- check_followers_only(actor_info, object),
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{:ok, object} <- check_report_removal(actor_info, object),
{:ok, object} <- maybe_check_thread(object),
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{:ok, object} <- check_object(object) do
{:ok, object}
else
{:reject, nil} -> {:reject, "[SimplePolicy]"}
{:reject, _} = e -> e
_ -> {:reject, "[SimplePolicy]"}
end
end
def filter(%{"id" => actor, "type" => obj_type} = object)
when obj_type in ["Application", "Group", "Organization", "Person", "Service"] do
actor_info = URI.parse(actor)
with {:ok, _} <- check_accept(actor_info),
{:ok, _} <- check_reject(actor_info),
{:ok, object} <- check_avatar_removal(actor_info, object),
{:ok, object} <- check_banner_removal(actor_info, object),
{:ok, object} <- check_background_removal(actor_info, object) do
{:ok, object}
else
{:reject, nil} -> {:reject, "[SimplePolicy]"}
{:reject, _} = e -> e
_ -> {:reject, "[SimplePolicy]"}
end
end
def filter(%{"id" => id} = object) do
with {:ok, _} <- filter(id) do
{:ok, object}
end
end
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def filter(object) when is_binary(object) do
uri = URI.parse(object)
with {:ok, _} <- check_accept(uri),
{:ok, _} <- check_reject(uri) do
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{:ok, object}
else
{:reject, nil} -> {:reject, "[SimplePolicy]"}
{:reject, _} = e -> e
_ -> {:reject, "[SimplePolicy]"}
end
end
def filter(object), do: {:ok, object}
defp obfuscate(string) when is_binary(string) do
# Want to strip at least two neighbouring chars
# to ensure at least one non-dot char is in the obfuscation area
stripped = String.length(string) - 6
{keepstart, keepend} =
if stripped > 1 do
{3, 3}
else
{
2 - div(1 - stripped, 2),
2 + div(stripped, 2)
}
end
string
|> to_charlist()
|> Enum.with_index()
|> Enum.map(fn
{?., _index} ->
?.
{char, index} ->
if keepstart <= index && index < String.length(string) - keepend, do: ?*, else: char
end)
|> to_string()
end
defp maybe_obfuscate(host, obfuscations) do
if MRF.subdomain_match?(obfuscations, host) do
obfuscate(host)
else
host
end
end
@impl true
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def describe do
exclusions = Config.get([:mrf, :transparency_exclusions]) |> MRF.instance_list_from_tuples()
obfuscations =
Config.get([:mrf, :transparency_obfuscate_domains], []) |> MRF.subdomains_regex()
mrf_simple_excluded =
Config.get(:mrf_simple)
|> Enum.filter(fn {_, v} -> is_list(v) end)
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|> Enum.map(fn {rule, instances} ->
{rule, Enum.reject(instances, fn {host, _} -> host in exclusions end)}
end)
mrf_simple =
mrf_simple_excluded
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|> Enum.map(fn {rule, instances} ->
{rule, Enum.map(instances, fn {host, _} -> maybe_obfuscate(host, obfuscations) end)}
end)
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|> Map.new()
# This is for backwards compatibility. We originally didn't sent
# extra info like a reason why an instance was rejected/quarantined/etc.
# Because we didn't want to break backwards compatibility it was decided
# to add an extra "info" key.
mrf_simple_info =
mrf_simple_excluded
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|> Enum.map(fn {rule, instances} ->
{rule, Enum.reject(instances, fn {_, reason} -> reason == "" end)}
end)
|> Enum.reject(fn {_, instances} -> instances == [] end)
|> Enum.map(fn {rule, instances} ->
instances =
instances
|> Enum.map(fn {host, reason} ->
{maybe_obfuscate(host, obfuscations), %{"reason" => reason}}
end)
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|> Map.new()
{rule, instances}
end)
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|> Map.new()
{:ok, %{mrf_simple: mrf_simple, mrf_simple_info: mrf_simple_info}}
end
@impl true
def config_description do
%{
key: :mrf_simple,
related_policy: "Pleroma.Web.ActivityPub.MRF.SimplePolicy",
label: "MRF Simple",
description: "Simple ingress policies",
children:
([
%{
key: :media_removal,
description:
"List of instances to strip media attachments from and the reason for doing so"
},
%{
key: :media_nsfw,
label: "Media NSFW",
description:
"List of instances to tag all media as NSFW (sensitive) from and the reason for doing so"
},
%{
key: :federated_timeline_removal,
description:
"List of instances to remove from the Federated (aka The Whole Known Network) Timeline and the reason for doing so"
},
%{
key: :reject,
description:
"List of instances to reject activities from (except deletes) and the reason for doing so"
},
%{
key: :accept,
description:
"List of instances to only accept activities from (except deletes) and the reason for doing so"
},
%{
key: :followers_only,
description:
"Force posts from the given instances to be visible by followers only and the reason for doing so"
},
%{
key: :report_removal,
description: "List of instances to reject reports from and the reason for doing so"
},
%{
key: :avatar_removal,
description: "List of instances to strip avatars from and the reason for doing so"
},
%{
key: :banner_removal,
description: "List of instances to strip banners from and the reason for doing so"
},
%{
key: :background_removal,
description:
"List of instances to strip user backgrounds from and the reason for doing so"
},
%{
key: :reject_deletes,
description: "List of instances to reject deletions from and the reason for doing so"
}
]
|> Enum.map(fn setting ->
Map.merge(
setting,
%{
type: {:list, :tuple},
key_placeholder: "instance",
value_placeholder: "reason",
suggestions: [
{"example.com", "Some reason"},
{"*.example.com", "Another reason"}
]
}
)
end)) ++
[
%{
key: :handle_threads,
label: "Apply to entire threads",
type: :boolean,
description:
"Enable to filter replies to threads based from their originating instance, using the reject and accept rules"
}
]
}
end
end