akkoma/lib/pleroma/web/plugs/http_signature_plug.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.Plugs.HTTPSignaturePlug do
import Plug.Conn
import Phoenix.Controller, only: [get_format: 1, text: 2]
alias Pleroma.Activity
alias Pleroma.Web.Router
alias Pleroma.Signature
alias Pleroma.Instances
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require Logger
@cachex Pleroma.Config.get([:cachex, :provider], Cachex)
def init(options) do
options
end
def call(%{assigns: %{valid_signature: true}} = conn, _opts) do
conn
end
def call(conn, _opts) do
if get_format(conn) == "activity+json" do
conn
|> maybe_assign_valid_signature()
|> maybe_require_signature()
else
conn
end
end
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def route_aliases(%{path_info: ["objects", id], query_string: query_string}) do
ap_id = Router.Helpers.o_status_url(Pleroma.Web.Endpoint, :object, id)
with %Activity{} = activity <- Activity.get_by_object_ap_id_with_object(ap_id) do
["/notice/#{activity.id}", "/notice/#{activity.id}?#{query_string}"]
else
_ -> []
end
end
def route_aliases(_), do: []
defp assign_valid_signature_on_route_aliases(conn, []), do: conn
defp assign_valid_signature_on_route_aliases(%{assigns: %{valid_signature: true}} = conn, _),
do: conn
defp assign_valid_signature_on_route_aliases(conn, [path | rest]) do
request_target = String.downcase("#{conn.method}") <> " #{path}"
conn =
conn
|> put_req_header("(request-target)", request_target)
|> case do
%{assigns: %{digest: digest}} = conn -> put_req_header(conn, "digest", digest)
conn -> conn
end
conn
|> assign(:valid_signature, HTTPSignatures.validate_conn(conn))
|> assign(:signature_actor_id, signature_host(conn))
|> assign_valid_signature_on_route_aliases(rest)
end
defp maybe_assign_valid_signature(conn) do
if has_signature_header?(conn) do
# set (request-target) header to the appropriate value
# we also replace the digest header with the one we computed
possible_paths =
route_aliases(conn) ++ [conn.request_path, conn.request_path <> "?#{conn.query_string}"]
assign_valid_signature_on_route_aliases(conn, possible_paths)
else
Logger.debug("No signature header!")
conn
end
end
defp has_signature_header?(conn) do
conn |> get_req_header("signature") |> Enum.at(0, false)
end
defp maybe_require_signature(
%{assigns: %{valid_signature: true, signature_actor_id: actor_id}} = conn
) do
# inboxes implicitly need http signatures for authentication
# so we don't really know if the instance will have broken federation after
# we turn on authorized_fetch_mode.
#
# to "check" this is a signed fetch, verify if method is GET
if conn.method == "GET" do
actor_host = URI.parse(actor_id).host
case @cachex.get(:request_signatures_cache, actor_host) do
{:ok, nil} ->
Logger.debug("Successful signature from #{actor_host}")
Instances.set_request_signatures(actor_host)
@cachex.put(:request_signatures_cache, actor_host, true)
{:ok, true} ->
:noop
any ->
Logger.warn(
"expected request signature cache to return a boolean, instead got #{inspect(any)}"
)
end
end
conn
end
defp maybe_require_signature(%{assigns: %{valid_signature: true}} = conn), do: conn
defp maybe_require_signature(conn) do
if Pleroma.Config.get([:activitypub, :authorized_fetch_mode], false) do
conn
|> put_status(:unauthorized)
|> text("Request not signed")
|> halt()
else
conn
end
end
defp signature_host(conn) do
with %{"keyId" => kid} <- HTTPSignatures.signature_for_conn(conn),
{:ok, actor_id} <- Signature.key_id_to_actor_id(kid) do
actor_id
else
e ->
{:error, e}
end
end
end