From 47013a7126a92e1f2890b68e0fd2e7ba1b77c97c Mon Sep 17 00:00:00 2001
From: Yaroslav Markin <yaroslav@markin.net>
Date: Tue, 17 Apr 2018 18:05:12 +0300
Subject: [PATCH] Add the `nonce: true` option for `javascript_include_tag`
 helper.

---
 actionview/CHANGELOG.md                                | 6 ++++++
 actionview/lib/action_view/helpers/asset_tag_helper.rb | 8 ++++++++
 actionview/test/template/asset_tag_helper_test.rb      | 8 ++++++++
 guides/source/security.md                              | 6 ++++++
 4 files changed, 28 insertions(+)

diff --git a/actionview/CHANGELOG.md b/actionview/CHANGELOG.md
index 6bb1efb0ac..d833f9cd98 100644
--- a/actionview/CHANGELOG.md
+++ b/actionview/CHANGELOG.md
@@ -1,3 +1,9 @@
+*   Add the `nonce: true` option for `javascript_include_tag` helper to
+    support automatic nonce generation for Content Security Policy.
+    Works the same way as `javascript_tag nonce: true` does.
+
+    *Yaroslav Markin*
+
 *   Remove `ActionView::Helpers::RecordTagHelper`.
 
     *Yoshiyuki Hirano*
diff --git a/actionview/lib/action_view/helpers/asset_tag_helper.rb b/actionview/lib/action_view/helpers/asset_tag_helper.rb
index 06fa1875fc..257080d902 100644
--- a/actionview/lib/action_view/helpers/asset_tag_helper.rb
+++ b/actionview/lib/action_view/helpers/asset_tag_helper.rb
@@ -55,6 +55,8 @@ module ActionView
       #   that path.
       # * <tt>:skip_pipeline</tt>  - This option is used to bypass the asset pipeline
       #   when it is set to true.
+      # * <tt>:nonce<tt>  - When set to true, adds an automatic nonce value if
+      #   you have Content Security Policy enabled.
       #
       # ==== Examples
       #
@@ -79,6 +81,9 @@ module ActionView
       #
       #   javascript_include_tag "http://www.example.com/xmlhr.js"
       #   # => <script src="http://www.example.com/xmlhr.js"></script>
+      #
+      #   javascript_include_tag "http://www.example.com/xmlhr.js", nonce: true
+      #   # => <script src="http://www.example.com/xmlhr.js" nonce="..."></script>
       def javascript_include_tag(*sources)
         options = sources.extract_options!.stringify_keys
         path_options = options.extract!("protocol", "extname", "host", "skip_pipeline").symbolize_keys
@@ -90,6 +95,9 @@ module ActionView
           tag_options = {
             "src" => href
           }.merge!(options)
+          if tag_options["nonce"] == true
+            tag_options["nonce"] = content_security_policy_nonce
+          end
           content_tag("script".freeze, "", tag_options)
         }.join("\n").html_safe
 
diff --git a/actionview/test/template/asset_tag_helper_test.rb b/actionview/test/template/asset_tag_helper_test.rb
index 6d98eacfb8..e68f03d1f4 100644
--- a/actionview/test/template/asset_tag_helper_test.rb
+++ b/actionview/test/template/asset_tag_helper_test.rb
@@ -29,6 +29,10 @@ class AssetTagHelperTest < ActionView::TestCase
     "http://www.example.com"
   end
 
+  def content_security_policy_nonce
+    "iyhD0Yc0W+c="
+  end
+
   AssetPathToTag = {
     %(asset_path(""))             => %(),
     %(asset_path("   "))          => %(),
@@ -421,6 +425,10 @@ class AssetTagHelperTest < ActionView::TestCase
     assert_dom_equal %(<script src="//assets.example.com/javascripts/prototype.js"></script>), javascript_include_tag("prototype")
   end
 
+  def test_javascript_include_tag_nonce
+    assert_dom_equal %(<script src="/javascripts/bank.js" nonce="iyhD0Yc0W+c="></script>), javascript_include_tag("bank", nonce: true)
+  end
+
   def test_stylesheet_path
     StylePathToTag.each { |method, tag| assert_dom_equal(tag, eval(method)) }
   end
diff --git a/guides/source/security.md b/guides/source/security.md
index a21526d895..3ac50fb147 100644
--- a/guides/source/security.md
+++ b/guides/source/security.md
@@ -1182,6 +1182,12 @@ as part of `html_options`. Example:
 <% end -%>
 ```
 
+The same works with `javascript_include_tag`:
+
+```html+erb
+<%= javascript_include_tag "script", nonce: true %>
+```
+
 Use [`csp_meta_tag`](http://api.rubyonrails.org/classes/ActionView/Helpers/CspHelper.html#method-i-csp_meta_tag)
 helper to create a meta tag "csp-nonce" with the per-session nonce value
 for allowing inline `<script>` tags.