Significantly tighten HTTP CSP

CHANGELOG.md

@@ -29,6 +29,7 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 - Quote posts are now considered as part of the same thread as the post they are quoting
 - Simplified HTTP signature processing
 - Rich media will now hard-exit after 5 seconds, to prevent timeline hangs
+- HTTP Content Security Policy is now far more strict to prevent any potential XSS/CSS leakages
 
 ### Fixed 
 - /api/v1/accounts/lookup will now respect restrict\_unauthenticated

lib/pleroma/web/plugs/http_security_plug.ex

@@ -106,20 +106,15 @@ defp csp_string(conn) do
     connect_src =
       if Config.get([:media_proxy, :enabled]) do
         sources = build_csp_multimedia_source_list()
-        ["connect-src 'self' blob: ", static_url, ?\s, websocket_url, ?\s, sources]
+        ["connect-src 'self' ", static_url, ?\s, websocket_url, ?\s, sources]
       else
-        ["connect-src 'self' blob: ", static_url, ?\s, websocket_url]
+        ["connect-src 'self' ", static_url, ?\s, websocket_url]
       end
 
-    style_src = "style-src 'self' 'unsafe-inline'"
-    font_src = "font-src 'self' data:"
+    style_src = "style-src 'self' '#{nonce_tag}'"
+    font_src = "font-src 'self'"
 
-    script_src =
-      if Config.get(:env) == :dev do
-        "script-src 'self' 'unsafe-eval' '#{nonce_tag}'"
-      else
-        "script-src 'self' '#{nonce_tag}'"
-      end
+    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"

test/pleroma/web/plugs/http_security_plug_test.exs

@@ -140,7 +140,7 @@ defp assert_media_img_src(conn, url) do
   defp assert_connect_src(conn, url) do
     conn = get(conn, "/api/v1/instance")
     [csp] = Conn.get_resp_header(conn, "content-security-policy")
-    assert csp =~ ~r/connect-src 'self' blob: [^;]+ #{url}/
+    assert csp =~ ~r/connect-src 'self' [^;]+ #{url}/
   end
 
   test "it does not send CSP headers when disabled", %{conn: conn} do