From 57fac3734753aa77c18f8d486c82511cac35ddfe Mon Sep 17 00:00:00 2001
From: Thomas Citharel <tcit@tcit.fr>
Date: Fri, 4 Nov 2022 10:55:26 +0100
Subject: [PATCH] Support CSP report_uri, report_to and the Report-To and
 Reporting-Endpoints headers

Signed-off-by: Thomas Citharel <tcit@tcit.fr>
---
 config/test.exs                            |  2 ++
 lib/web/plugs/http_security_plug.ex        | 31 +++++++++++++++++++---
 test/web/plugs/http_security_plug_test.exs | 22 ++++++++++++++-
 3 files changed, 50 insertions(+), 5 deletions(-)

diff --git a/config/test.exs b/config/test.exs
index 452c5e061..62901358f 100644
--- a/config/test.exs
+++ b/config/test.exs
@@ -88,6 +88,8 @@ config :mobilizon, Mobilizon.Web.Gettext, allowed_locales: ["fr", "en", "es", "r
 
 config :junit_formatter, report_dir: "."
 
+config :mobilizon, :http_security, report_uri: "https://endpoint.com"
+
 if System.get_env("DOCKER", "false") == "false" && File.exists?("./config/test.secret.exs") do
   import_config "test.secret.exs"
 end
diff --git a/lib/web/plugs/http_security_plug.ex b/lib/web/plugs/http_security_plug.ex
index 693b64220..3af248bde 100644
--- a/lib/web/plugs/http_security_plug.ex
+++ b/lib/web/plugs/http_security_plug.ex
@@ -10,6 +10,7 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
 
   alias Mobilizon.Config
   alias Mobilizon.Service.{FrontEndAnalytics, GlobalSearch, Pictures}
+  alias Mobilizon.Web.Endpoint
   import Plug.Conn
 
   require Logger
@@ -33,13 +34,32 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
     referrer_policy =
       Keyword.get(options, :referrer_policy, Config.get([:http_security, :referrer_policy]))
 
-    [
+    report_uri = Config.get([:http_security, :report_uri])
+
+    headers = [
       {"x-xss-protection", "0"},
       {"x-frame-options", "DENY"},
       {"x-content-type-options", "nosniff"},
       {"referrer-policy", referrer_policy},
       {"content-security-policy", csp_string(options)}
     ]
+
+    if report_uri do
+      report_group = %{
+        "group" => "csp-endpoint",
+        "max-age" => 10_886_400,
+        "endpoints" => [
+          %{"url" => report_uri}
+        ]
+      }
+
+      [
+        {"report-to", Jason.encode!(report_group)},
+        {"reporting-endpoints", "csp-endpoint=\"#{report_uri}\""} | headers
+      ]
+    else
+      headers
+    end
   end
 
   @static_csp_rules [
@@ -61,9 +81,10 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
 
   @spec csp_string(Keyword.t()) :: String.t()
   defp csp_string(options) do
-    scheme = Keyword.get(options, :scheme, Config.get([Pleroma.Web.Endpoint, :url])[:scheme])
-    static_url = Mobilizon.Web.Endpoint.static_url()
-    websocket_url = Mobilizon.Web.Endpoint.websocket_url()
+    scheme = Keyword.get(options, :scheme, Config.get([Endpoint, :url])[:scheme])
+    static_url = Endpoint.static_url()
+    websocket_url = Endpoint.websocket_url()
+    report_uri = Config.get([:http_security, :report_uri])
 
     img_src = [@img_src] ++ [get_csp_config(:img_src, options)]
 
@@ -106,6 +127,7 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
 
     frame_ancestors = [frame_ancestors] ++ [get_csp_config(:frame_ancestors, options)]
 
+    report = if report_uri, do: ["report-uri ", report_uri, " ; report-to csp-endpoint"]
     insecure = if scheme == "https", do: "upgrade-insecure-requests"
 
     @csp_start
@@ -118,6 +140,7 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlug do
     |> add_csp_param(frame_src)
     |> add_csp_param(frame_ancestors)
     |> add_csp_param(insecure)
+    |> add_csp_param(report)
     |> to_string()
   end
 
diff --git a/test/web/plugs/http_security_plug_test.exs b/test/web/plugs/http_security_plug_test.exs
index 43be1dec4..e36921fec 100644
--- a/test/web/plugs/http_security_plug_test.exs
+++ b/test/web/plugs/http_security_plug_test.exs
@@ -49,6 +49,26 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlugTest do
       assert Conn.get_resp_header(resp, "referrer-policy") == ["no-referrer"]
     end
 
+    test "it sends `report-to`, `reporting-endpoints` & `report-uri` CSP response headers", %{
+      conn: conn
+    } do
+      conn = post(conn, "/api")
+
+      [csp] = Conn.get_resp_header(conn, "content-security-policy")
+
+      assert csp =~ ~r|report-uri https://endpoint.com ; report-to csp-endpoint;|
+
+      [report_to] = Conn.get_resp_header(conn, "report-to")
+
+      assert report_to ==
+               "{\"endpoints\":[{\"url\":\"https://endpoint.com\"}],\"group\":\"csp-endpoint\",\"max-age\":10886400}"
+
+      [reporting_endpoints] = Conn.get_resp_header(conn, "reporting-endpoints")
+
+      assert reporting_endpoints ==
+               "csp-endpoint=\"https://endpoint.com\""
+    end
+
     test "default values for content-security-policy are always included", %{conn: conn} do
       conn = post(conn, "/api")
 
@@ -73,7 +93,7 @@ defmodule Mobilizon.Web.Plugs.HTTPSecurityPlugTest do
       [csp] = Conn.get_resp_header(conn, "content-security-policy")
 
       assert csp =~
-               ~r/script-src 'self' 'unsafe-eval' 'sha256-[\w+\/=]*' 'sha256-[\w+\/=]*' example.com matomo.example.com  ;/
+               ~r/script-src 'self' 'unsafe-eval' 'sha256-[\w+\/=]*' 'sha256-[\w+\/=]*' example.com matomo.example.com\s+;/
     end
   end