spc-pleroma/lib/pleroma/plugs/http_signature.ex

defmodule Pleroma.Web.Plugs.HTTPSignaturePlug do
  alias Pleroma.Web.HTTPSignatures
  import Plug.Conn
  require Logger

  def init(options) do
    options
  end

  def call(%{assigns: %{valid_signature: true}} = conn, opts) do
    conn
  end

  def call(conn, opts) do
    user = conn.params["actor"]
    Logger.debug("Checking sig for #{user}")

    if get_req_header(conn, "signature") do
      conn =
        conn
        |> put_req_header(
          "(request-target)",
          String.downcase("#{conn.method}") <> " #{conn.request_path}"
        )

      assign(conn, :valid_signature, HTTPSignatures.validate_conn(conn))
    else
      Logger.debug("No signature header!")
      conn
    end
  end
end