svelte/1: Add CSP nonce parameters

Author: xtian

lib/live_svelte.ex

@@ -45,6 +45,18 @@ defmodule LiveSvelte do
     doc: "Class to apply to the Svelte component",
     examples: ["my-class", "my-class another-class"]
 
+  attr :csp_nonce, :string,
+    default: nil,
+    doc: "A Content-Security-Policy nonce for the generated <script> and <style> tags"
+
+  attr :csp_script_nonce, :string,
+    default: nil,
+    doc: "A Content-Security-Policy nonce for the generated <script> tag"
+
+  attr :csp_style_nonce, :string,
+    default: nil,
+    doc: "A Content-Security-Policy nonce for the generated <style> tag"
+
   attr :ssr, :boolean,
     default: true,
     doc: "Whether to render the component via NodeJS on the server",
@@ -124,6 +136,8 @@ defmodule LiveSvelte do
 
     streams_diff = calculate_streams_diff(assigns, init or dead)
 
+    csp_attrs = if nonce = assigns.csp_nonce, do: [nonce: nonce]
+
     assigns =
       assigns
       |> assign(:init, init)
@@ -134,9 +148,17 @@ defmodule LiveSvelte do
       |> assign(:use_diff, use_diff)
       |> assign(:props_diff, props_diff)
       |> assign(:streams_diff, streams_diff)
+      |> assign(
+        :csp_script_attrs,
+        csp_attrs || if(nonce = assigns.csp_script_nonce, do: [nonce: nonce], else: [])
+      )
+      |> assign(
+        :csp_style_attrs,
+        csp_attrs || if(nonce = assigns.csp_style_nonce, do: [nonce: nonce], else: [])
+      )
 
     ~H"""
-    <script>
+    <script {@csp_script_attrs}>
       <%= raw(@ssr_render["head"]) %>
     </script>
     <div
@@ -154,7 +176,7 @@ defmodule LiveSvelte do
     >
       <div id={"#{@svelte_id}-target"} data-svelte-target>
         {raw(@ssr_render["head"])}
-        <style>
+        <style {@csp_style_attrs}>
           <%= raw(@ssr_render["css"]["code"]) %>
         </style>
         {raw(@ssr_render["html"])}

test/csp_nonce_test.exs

@@ -0,0 +1,60 @@
+defmodule LiveSvelte.CspNonceTest do
+  use ExUnit.Case, async: true
+
+  defp render_html(opts) do
+    %{
+      __changed__: nil,
+      socket: nil,
+      name: "TestComponent",
+      id: "test-csp",
+      key: nil,
+      props: %{},
+      ssr: false,
+      class: nil,
+      loading: [],
+      inner_block: [],
+      csp_nonce: opts[:csp_nonce],
+      csp_script_nonce: opts[:csp_script_nonce],
+      csp_style_nonce: opts[:csp_style_nonce]
+    }
+    |> LiveSvelte.svelte()
+    |> Phoenix.HTML.Safe.to_iodata()
+    |> IO.iodata_to_binary()
+  end
+
+  setup do
+    %{nonce: System.unique_integer([:positive])}
+  end
+
+  test "no nonce attributes when none specified" do
+    refute render_html(%{}) =~ "nonce="
+  end
+
+  test "csp_nonce applies to both script and style", %{nonce: nonce} do
+    html = render_html(%{csp_nonce: nonce})
+
+    assert html =~ ~r/<script nonce="#{nonce}">/
+    assert html =~ ~r/<style nonce="#{nonce}">/
+  end
+
+  test "csp_script_nonce applies only to script", %{nonce: nonce} do
+    html = render_html(%{csp_script_nonce: nonce})
+
+    assert html =~ ~r/<script nonce="#{nonce}">/
+    refute html =~ ~r/<style nonce=/
+  end
+
+  test "csp_style_nonce applies only to style", %{nonce: nonce} do
+    html = render_html(%{csp_style_nonce: nonce})
+
+    assert html =~ ~r/<style nonce="#{nonce}">/
+    refute html =~ ~r/<script nonce=/
+  end
+
+  test "separate script and style nonces", %{nonce: nonce} do
+    html = render_html(%{csp_script_nonce: nonce, csp_style_nonce: nonce * 2})
+
+    assert html =~ ~r/<script nonce="#{nonce}">/
+    assert html =~ ~r/<style nonce="#{nonce * 2}">/
+  end
+end