web+ap protocol handler

lib/pleroma/web/protocol_handler/protocol_handler_controller.ex

@@ -0,0 +1,60 @@
+# Pleroma: A lightweight social networking server
+# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
+# SPDX-License-Identifier: AGPL-3.0-only
+
+defmodule Pleroma.Web.AkkomaAPI.ProtocolHandlerController do
+  use Pleroma.Web, :controller
+
+  import Pleroma.Web.ControllerHelper, only: [json_response: 3]
+
+  alias Pleroma.Activity
+  alias Pleroma.User
+  alias Pleroma.Web.Plugs.OAuthScopesPlug
+
+  @oauth_search_actions [:handle]
+
+  # Note: (requires read:search)
+  plug(OAuthScopesPlug, %{scopes: ["read:search"], fallback: :proceed_unauthenticated} when action in @oauth_search_actions)
+
+  # Protocol definition: https://datatracker.ietf.org/doc/draft-soni-protocol-handler-well-known-uri/
+  def reroute(conn, %{"target" => target_param}) do
+    conn |> redirect(to: "/api/v1/akkoma/protocol-handler?#{URI.encode_query([target: target_param])}")
+  end
+
+  def handle(%{assigns: %{user: user}} = conn, %{"target" => "web+ap://" <> identifier}) when is_nil(user) do
+    # Unauthenticated, only local records should be searched
+    cond do
+      String.starts_with?(identifier, Pleroma.Config.get([Pleroma.Web.Endpoint, :url, :host])) -> find_and_redirect(conn, identifier)
+      true -> conn |> json_response(:forbidden, "Invalid credentials.")
+    end
+  end
+
+  def handle(%{assigns: %{user: user}} = conn, %{"target" => "web+ap://" <> identifier}) when not is_nil(user) do
+    # Authenticated User
+    find_and_redirect(conn, identifier)
+  end
+
+  def handle(conn, _), do: conn |> json_response(:bad_request, "Could not handle protocol URL")
+
+  # Should webfinger handles even be accepted? They are not ActivityPub URLs
+  defp find_and_redirect(conn, "@" <> identifier) do
+    redirect_to_target(User.get_or_fetch(identifier), conn)
+      || conn |> json_response(:not_found, "Not Found - @#{identifier}")
+  end
+
+  defp find_and_redirect(%{assigns: %{user: user}} = conn, identifier) do
+    redirect_to_target(User.get_or_fetch("https://" <> identifier), conn)
+      || redirect_to_target(Activity.search(user, "https://" <> identifier, [limit: 1]), conn)
+      || conn |> json_response(:not_found, "Not Found - #{identifier}")
+  end
+
+  defp redirect_to_target({:error, _err}, _conn), do: nil
+  defp redirect_to_target({:ok, found}, conn) do
+    conn |> redirect(to: "/users/#{found.id}")
+  end
+
+  defp redirect_to_target([], _conn), do: nil
+  defp redirect_to_target([%Activity{} = activity], conn) do
+    conn |> redirect(to: "/notice/#{activity.id}")
+  end
+end

lib/pleroma/web/router.ex

@@ -475,6 +475,7 @@ defmodule Pleroma.Web.Router do
 
   scope "/api/v1/akkoma", Pleroma.Web.AkkomaAPI do
     pipe_through(:api)
+    get("/protocol-handler", ProtocolHandlerController, :handle)
 
     get(
       "/preferred_frontend/available",
@@ -852,6 +853,7 @@ defmodule Pleroma.Web.Router do
     get("/host-meta", WebFinger.WebFingerController, :host_meta)
     get("/webfinger", WebFinger.WebFingerController, :webfinger)
     get("/nodeinfo", Nodeinfo.NodeinfoController, :schemas)
+    get("/protocol-handler", AkkomaAPI.ProtocolHandlerController, :reroute)
   end
 
   scope "/nodeinfo", Pleroma.Web do