akkoma/lib/pleroma/web/plugs/http_security_plug.ex
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Significantly tighten HTTP CSP
2023-01-02 15:21:19 +00:00

246 lines
7.9 KiB
Elixir

# Pleroma: A lightweight social networking server
# Copyright © 2017-2021 Pleroma Authors <https://pleroma.social/>
# SPDX-License-Identifier: AGPL-3.0-only
defmodule Pleroma.Web.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(conn))
|> maybe_send_sts_header(Config.get([:http_security, :sts]))
else
conn
end
end
def primary_frontend do
with %{"name" => frontend} <- Config.get([:frontends, :primary]),
available <- Config.get([:frontends, :available]),
%{} = primary_frontend <- Map.get(available, frontend) do
{:ok, primary_frontend}
end
end
def custom_http_frontend_headers do
with {:ok, %{"custom-http-headers" => custom_headers}} <- primary_frontend() do
custom_headers
else
_ -> []
end
end
@spec headers(Plug.Conn.t()) :: [{String.t(), String.t()}]
def headers(conn) do
referrer_policy = Config.get([:http_security, :referrer_policy])
report_uri = Config.get([:http_security, :report_uri])
custom_http_frontend_headers = custom_http_frontend_headers()
headers = [
{"x-xss-protection", "0"},
{"x-permitted-cross-domain-policies", "none"},
{"x-frame-options", "DENY"},
{"x-content-type-options", "nosniff"},
{"referrer-policy", referrer_policy},
{"content-security-policy", csp_string(conn)},
{"permissions-policy", "interest-cohort=()"}
]
headers =
if custom_http_frontend_headers do
custom_http_frontend_headers ++ headers
else
headers
end
if report_uri do
report_group = %{
"group" => "csp-endpoint",
"max-age" => 10_886_400,
"endpoints" => [
%{"url" => report_uri}
]
}
[{"report-to", Jason.encode!(report_group)} | headers]
else
headers
end
end
static_csp_rules = [
"default-src 'none'",
"base-uri 'none'",
"frame-ancestors 'none'",
"manifest-src 'self'"
]
@csp_start [Enum.join(static_csp_rules, ";") <> ";"]
defp csp_string(conn) 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])
%{assigns: %{csp_nonce: nonce}} = conn
nonce_tag = "nonce-" <> nonce
img_src = "img-src 'self' data: blob:"
media_src = "media-src 'self'"
# Strict multimedia CSP enforcement only when MediaProxy is enabled
{img_src, media_src} =
if Config.get([:media_proxy, :enabled]) &&
!Config.get([:media_proxy, :proxy_opts, :redirect_on_failure]) do
sources = build_csp_multimedia_source_list()
{[img_src, sources], [media_src, sources]}
else
{[img_src, " https:"], [media_src, " https:"]}
end
connect_src =
if Config.get([:media_proxy, :enabled]) do
sources = build_csp_multimedia_source_list()
["connect-src 'self' ", static_url, ?\s, websocket_url, ?\s, sources]
else
["connect-src 'self' ", static_url, ?\s, websocket_url]
end
style_src = "style-src 'self' '#{nonce_tag}'"
font_src = "font-src 'self'"
script_src = "script-src 'self' '#{nonce_tag}'"
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)
|> add_csp_param(media_src)
|> add_csp_param(connect_src)
|> add_csp_param(script_src)
|> add_csp_param(font_src)
|> add_csp_param(style_src)
|> add_csp_param(insecure)
|> add_csp_param(report)
|> :erlang.iolist_to_binary()
end
defp build_csp_from_whitelist([], acc), do: acc
defp build_csp_from_whitelist([last], acc) do
[build_csp_param_from_whitelist(last) | acc]
end
defp build_csp_from_whitelist([head | tail], acc) do
build_csp_from_whitelist(tail, [[?\s, build_csp_param_from_whitelist(head)] | acc])
end
# TODO: use `build_csp_param/1` after removing support bare domains for media proxy whitelist
defp build_csp_param_from_whitelist("http" <> _ = url) do
build_csp_param(url)
end
defp build_csp_param_from_whitelist(url), do: url
defp build_csp_multimedia_source_list do
media_proxy_whitelist =
[:media_proxy, :whitelist]
|> Config.get()
|> build_csp_from_whitelist([])
captcha_method = Config.get([Pleroma.Captcha, :method])
captcha_endpoint = Config.get([captcha_method, :endpoint])
base_endpoints =
[
[:media_proxy, :base_url],
[Pleroma.Upload, :base_url],
[Pleroma.Uploaders.S3, :public_endpoint]
]
|> Enum.map(&Config.get/1)
[captcha_endpoint | base_endpoints]
|> Enum.map(&build_csp_param/1)
|> Enum.reduce([], &add_source(&2, &1))
|> add_source(media_proxy_whitelist)
end
defp add_source(iodata, nil), do: iodata
defp add_source(iodata, []), do: iodata
defp add_source(iodata, source), do: [[?\s, source] | iodata]
defp add_csp_param(csp_iodata, nil), do: csp_iodata
defp add_csp_param(csp_iodata, param), do: [[param, ?;] | csp_iodata]
defp build_csp_param(nil), do: nil
defp build_csp_param(url) when is_binary(url) do
%{host: host, scheme: scheme} = URI.parse(url)
if scheme do
[scheme, "://", host]
end
end
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
7C...::::::::::::,,,,.. .................... vSi.
;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])
merge_resp_headers(conn, [
{"strict-transport-security", "max-age=#{max_age_sts}; includeSubDomains; preload"}
])
end
defp maybe_send_sts_header(conn, _), do: conn
end