# Pleroma: A lightweight social networking server # Copyright © 2017-2019 Pleroma Authors <https://pleroma.social/> # SPDX-License-Identifier: AGPL-3.0-only # https://tools.ietf.org/html/draft-cavage-http-signatures-08 defmodule Pleroma.Web.HTTPSignatures do alias Pleroma.User alias Pleroma.Web.ActivityPub.ActivityPub alias Pleroma.Web.ActivityPub.Utils require Logger def split_signature(sig) do default = %{"headers" => "date"} sig = sig |> String.trim() |> String.split(",") |> Enum.reduce(default, fn part, acc -> [key | rest] = String.split(part, "=") value = Enum.join(rest, "=") Map.put(acc, key, String.trim(value, "\"")) end) Map.put(sig, "headers", String.split(sig["headers"], ~r/\s/)) end def validate(headers, signature, public_key) do sigstring = build_signing_string(headers, signature["headers"]) Logger.debug("Signature: #{signature["signature"]}") Logger.debug("Sigstring: #{sigstring}") {:ok, sig} = Base.decode64(signature["signature"]) :public_key.verify(sigstring, :sha256, sig, public_key) end def validate_conn(conn) do # TODO: How to get the right key and see if it is actually valid for that request. # For now, fetch the key for the actor. with actor_id <- Utils.get_ap_id(conn.params["actor"]), {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do if validate_conn(conn, public_key) do true else Logger.debug("Could not validate, re-fetching user and trying one more time") # Fetch user anew and try one more time with actor_id <- Utils.get_ap_id(conn.params["actor"]), {:ok, _user} <- ActivityPub.make_user_from_ap_id(actor_id), {:ok, public_key} <- User.get_public_key_for_ap_id(actor_id) do validate_conn(conn, public_key) end end else _e -> Logger.debug("Could not public key!") false end end def validate_conn(conn, public_key) do headers = Enum.into(conn.req_headers, %{}) signature = split_signature(headers["signature"]) validate(headers, signature, public_key) end def build_signing_string(headers, used_headers) do used_headers |> Enum.map(fn header -> "#{header}: #{headers[header]}" end) |> Enum.join("\n") end def sign(user, headers) do with {:ok, %{info: %{keys: keys}}} <- Pleroma.Web.WebFinger.ensure_keys_present(user), {:ok, private_key, _} = Pleroma.Web.Salmon.keys_from_pem(keys) do sigstring = build_signing_string(headers, Map.keys(headers)) signature = :public_key.sign(sigstring, :sha256, private_key) |> Base.encode64() [ keyId: user.ap_id <> "#main-key", algorithm: "rsa-sha256", headers: Map.keys(headers) |> Enum.join(" "), signature: signature ] |> Enum.map(fn {k, v} -> "#{k}=\"#{v}\"" end) |> Enum.join(",") end end end