mobilizon/lib/web/plugs/http_signatures.ex

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# Portions of this file are derived from Pleroma:
# Copyright © 2017-2018 Pleroma Authors <https://pleroma.social>
# SPDX-License-Identifier: AGPL-3.0-only
# Upstream: https://git.pleroma.social/pleroma/pleroma/blob/develop/lib/pleroma/plugs/http_signature.ex
defmodule Mobilizon.Web.Plugs.HTTPSignatures do
@moduledoc """
Plug to check HTTP Signatures on every incoming request
"""
import Plug.Conn, only: [get_req_header: 2, put_req_header: 3, assign: 3]
require Logger
def init(options) do
options
end
@spec call(Plug.Conn.t(), any) :: Plug.Conn.t()
def call(%{assigns: %{valid_signature: true}} = conn, _opts) do
conn
end
def call(conn, _opts) do
signature = conn |> get_req_header("signature") |> List.first()
if is_nil(signature) do
Logger.debug("No signature header!")
conn
else
# set (request-target) header to the appropriate value
# we also replace the digest header with the one we computed
conn =
conn
|> put_req_header(
"(request-target)",
String.downcase("#{conn.method}") <> " #{conn.request_path}"
)
|> maybe_put_digest_header()
signature_valid =
try do
HTTPSignatures.validate_conn(conn)
rescue
# Because if the actor is not found in
# Mobilizon.Federation.HTTPSignatures.Signature.get_public_key_for_url/1
# we return an empty string as key,
# to give an extra-chance of fetching new actor keys
# and :public_key.verify doesn't like this
ArgumentError -> false
end
Logger.debug("Is signature valid ? #{inspect(signature_valid)}")
date_valid = date_valid?(conn)
Logger.debug("Is date valid ? #{inspect(date_valid)}")
assign(conn, :valid_signature, signature_valid && date_valid)
end
end
defp maybe_put_digest_header(%Plug.Conn{assigns: %{digest: digest}} = conn),
do: put_req_header(conn, "digest", digest)
defp maybe_put_digest_header(%Plug.Conn{} = conn), do: conn
@spec date_valid?(Plug.Conn.t()) :: boolean()
defp date_valid?(conn) do
date = conn |> get_req_header("date") |> List.first()
if is_nil(date) do
false
else
case Timex.parse(date, "{WDshort}, {0D} {Mshort} {YYYY} {h24}:{m}:{s} GMT") do
{:ok, %NaiveDateTime{} = date} ->
date
|> DateTime.from_naive!("Etc/UTC")
|> date_diff_ok?()
{:ok, %DateTime{} = date} ->
date_diff_ok?(date)
{:error, _err} ->
false
end
end
end
@spec date_diff_ok?(DateTime.t()) :: boolean()
defp date_diff_ok?(%DateTime{} = date) do
DateTime.diff(date, DateTime.utc_now()) <= 12 * 3600 &&
DateTime.diff(date, DateTime.utc_now()) >= -12 * 3600
end
end