akkoma/lib/pleroma/plugs/http_security_plug.ex

# Pleroma: A lightweight social networking server
# Copyright © 2017-2020 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only

defmodule Pleroma.Plugs.HTTPSecurityPlug do
  alias Pleroma.Config
  import Plug.Conn

  require Logger

  def init(opts), do: opts

  def call(conn, _options) do
    if Config.get([:http_security, :enabled]) do
      conn
      |> merge_resp_headers(headers())
      |> maybe_send_sts_header(Config.get([:http_security, :sts]))
    else
      conn
    end
  end

  defp headers do
    referrer_policy = Config.get([:http_security, :referrer_policy])
    report_uri = Config.get([:http_security, :report_uri])

    headers = [
      {"x-xss-protection", "1; mode=block"},
      {"x-permitted-cross-domain-policies", "none"},
      {"x-frame-options", "DENY"},
      {"x-content-type-options", "nosniff"},
      {"referrer-policy", referrer_policy},
      {"x-download-options", "noopen"},
      {"content-security-policy", csp_string()}
    ]

    if report_uri do
      report_group = %{
        "group" => "csp-endpoint",
        "max-age" => 10_886_400,
        "endpoints" => [
          %{"url" => report_uri}
        ]
      }

      [{"reply-to", Jason.encode!(report_group)} | headers]
    else
      headers
    end
  end

  @csp_start [
               "default-src 'none'",
               "base-uri 'self'",
               "frame-ancestors 'none'",
               "style-src 'self' 'unsafe-inline'",
               "font-src 'self'",
               "manifest-src 'self'"
             ]
             |> Enum.join(";")
             |> Kernel.<>(";")
             |> List.wrap()

  defp csp_string do
    scheme = Config.get([Pleroma.Web.Endpoint, :url])[:scheme]
    static_url = Pleroma.Web.Endpoint.static_url()
    websocket_url = Pleroma.Web.Endpoint.websocket_url()
    report_uri = Config.get([:http_security, :report_uri])

    connect_src = ["connect-src 'self' ", static_url, ?\s, websocket_url]

    connect_src =
      if Pleroma.Config.get(:env) == :dev do
        [connect_src," http://localhost:3035/"]
      else
        connect_src
      end

    script_src =
      if Pleroma.Config.get(:env) == :dev do
        "script-src 'self' 'unsafe-eval'"
      else
        "script-src 'self'"
      end

    report = if report_uri, do: ["report-uri ", report_uri, ";report-to csp-endpoint"]
    insecure = if scheme == "https", do: "upgrade-insecure-requests"

    @csp_start
    |> add_csp_param("img-src 'self' data: blob: https:")
    |> add_csp_param("media-src 'self' https:")
    |> add_csp_param(connect_src)
    |> add_csp_param(script_src)
    |> add_csp_param(insecure)
    |> add_csp_param(report)
    |> :erlang.iolist_to_binary()
  end

  defp add_csp_param(csp_iodata, nil), do: csp_iodata

  defp add_csp_param(csp_iodata, param), do: [[param, ?;] | csp_iodata]

  def warn_if_disabled do
    unless Config.get([:http_security, :enabled]) do
      Logger.warn("
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             .z9;  ......:i::::,.. .i:...................zWX.
             vbv  ......,i::::,,.      ................. :AQY
            c6Y.  .,...,::::,,..:t0@@QY. ................ :8bi
           :6S. ..,,...,:::,,,..EMMMMMMI. ............... .;bZ,
          :6o,  .,,,,..:::,,,..i#MMMMMM#v.................  YW2.
         .n8i ..,,,,,,,::,,,,.. tMMMMM@C:.................. .1Wn
         7Uc. .:::,,,,,::,,,,..   i1t;,..................... .UEi
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         ;1;...,,::::::,.........       ..................    Yz:
          v97,.........                                     .voC.
           izAotX7777777777777777777777777777777777777777Y7n92:
             .;CoIIIIIUAA666666699999ZZZZZZZZZZZZZZZZZZZZ6ov.

HTTP Security is disabled. Please re-enable it to prevent users from attacking
your instance and your users via malicious posts:

      config :pleroma, :http_security, enabled: true
      ")
    end
  end

  defp maybe_send_sts_header(conn, true) do
    max_age_sts = Config.get([:http_security, :sts_max_age])
    max_age_ct = Config.get([:http_security, :ct_max_age])

    merge_resp_headers(conn, [
      {"strict-transport-security", "max-age=#{max_age_sts}; includeSubDomains"},
      {"expect-ct", "enforce, max-age=#{max_age_ct}"}
    ])
  end

  defp maybe_send_sts_header(conn, _), do: conn
end