alphagov · elenatanasoiu · May 15, 2017 · May 12, 2017 · May 12, 2017
diff --git a/CHANGELOG.md b/CHANGELOG.md
@@ -1,3 +1,7 @@
+# Development
+
+- Adds SRI to js and css assets ([PR #301](https://github.com/alphagov/govuk_template/pull/301)). This requires `sprockets-rails` >= 3.0 in the projects using this gem.
+
 # 0.20.1
 - Fix invalid html from Apple touch icons syntax ([PR #300]https://github.com/alphagov/govuk_template/pull/300) and
 update icon sizes to match Apple specs

diff --git a/build_tools/compiler/template_processor.rb b/build_tools/compiler/template_processor.rb
@@ -1,4 +1,6 @@
 require 'erb'
+require 'active_support/core_ext/hash'
+require 'active_support/core_ext/array'
 
 module Compiler
   class TemplateProcessor
@@ -39,5 +41,53 @@ def asset_path(file, options={})
     def method_missing(name, *args)
       puts "#{name} #{args.inspect}"
     end
+
+    def stylesheet_link_tag(*sources)
+      options = exclude_sri_fields(sources.extract_options!)
+      sources.uniq.map { |source|
+        link_options = {
+            "rel" => "stylesheet",
+            "media" => "screen",
+            "href" => asset_path(source)
+        }.merge!(options)
+        tag(:link, tag_options(link_options))
+      }.join("\n")
+    end
+
+    def javascript_include_tag(*sources)
+      options = exclude_sri_fields(sources.extract_options!)
+      sources.uniq.map { |source|
+        script_options = {
+            "src" => asset_path(source)
+        }.merge!(options)
+        content_tag(:script, tag_options(script_options))
+      }.join("\n")
+    end
+
+    def exclude_sri_fields(options)
+      options.stringify_keys.except("integrity", "crossorigin")
+    end
+
+    def content_tag(name, options = nil)
+      "<#{name}#{options}></#{name}>"
+    end
+
+    def tag(name, options)
+      "<#{name}#{options}/>"
+    end
+
+    def tag_options(options)
+      return if options.empty?
+      output = "".dup
+      sep    = " "
+      options.each_pair do |key, value|
+        if !value.nil?
+          output << sep
+          output << %(#{key}="#{value}")
+        end
+      end
+      output unless output.empty?
+    end
+
   end
 end
diff --git a/docs/using-with-rails.md b/docs/using-with-rails.md
@@ -38,3 +38,20 @@ Or to add content to `<head>`, for stylesheets or similar:
 ```
 
 Check out the [full list of blocks](template-blocks.md) you can use to customise the template.
+
+## SRI 
+
+`govuk_template` >= 20.0.0 can be used together with `sprockets-rails` >= 3.0.0 in order to make use of the SRI 
+
+You can read more about SRI [here](https://developer.mozilla.org/en-US/docs/Web/Security/Subresource_Integrity).
+
+SRI will add an `integrity` attribute on your script tags:
+
+`<script src="https://example.com/example.css" 
+integrity="sha384oqVuAfXRKap7fdgcCY5uykM6+R9GqQ8K/uxy9rx7HNQlGYl1kPzQho1wx4JwY8w" 
+crossorigin="anonymous"></script>`
+
+The example above is generated automatically by sprockets-rails in your project if the integrity option is set to true:
+
+`<%= stylesheet_script_tag 'example', integrity: true %>`
+
diff --git a/source/views/layouts/govuk_template.html.erb b/source/views/layouts/govuk_template.html.erb
@@ -6,15 +6,16 @@
     <meta charset="utf-8" />
     <title><%= content_for?(:page_title) ? yield(:page_title) : "GOV.UK - The best place to find government services and information" %></title>
 
-    <!--[if gt IE 8]><!--><link href="<%= asset_path "govuk-template.css" %>" media="screen" rel="stylesheet" /><!--<![endif]-->
+    <!--[if gt IE 8]><!--><%= stylesheet_link_tag "govuk-template.css", integrity: true, crossorigin: "anonymous" %><!--<![endif]-->
     <!--[if IE 6]><link href="<%= asset_path "govuk-template-ie6.css" %>" media="screen" rel="stylesheet" /><![endif]-->
     <!--[if IE 7]><link href="<%= asset_path "govuk-template-ie7.css" %>" media="screen" rel="stylesheet" /><![endif]-->
     <!--[if IE 8]><link href="<%= asset_path "govuk-template-ie8.css" %>" media="screen" rel="stylesheet" /><![endif]-->
-    <link href="<%= asset_path "govuk-template-print.css" %>" media="print" rel="stylesheet" />
+    <%= stylesheet_link_tag "govuk-template-print.css", media: "print", integrity: true, crossorigin: "anonymous" %>
 
     <!--[if IE 8]><link href="<%= asset_path "fonts-ie8.css" %>" media="all" rel="stylesheet" /><![endif]-->
-    <!--[if gte IE 9]><!--><link href="<%= asset_path "fonts.css" %>" media="all" rel="stylesheet" /><!--<![endif]-->
-    <!--[if lt IE 9]><script src="<%= asset_path "ie.js" %>"></script><![endif]-->
+    <!--[if gte IE 9]><!--><%= stylesheet_link_tag "fonts.css", media: "all", integrity: true, crossorigin: "anonymous" %><!--<![endif]-->
+    <!--[if gte IE 9]><!--><%= stylesheet_link_tag "fonts.css", media: "all", integrity: true, crossorigin: "anonymous" %><!--<![endif]-->
+    <!--[if lt IE 9]><%= javascript_include_tag "ie.js", integrity: true, crossorigin: "anonymous" %><![endif]-->
 
     <link rel="shortcut icon" href="<%= asset_path 'favicon.ico' %>" type="image/x-icon" />
     <%# the colour used for mask-icon is the standard palette $black from

diff --git a/spec/build_tools/compiler/django_processor_spec.rb b/spec/build_tools/compiler/django_processor_spec.rb
@@ -26,6 +26,7 @@ def valid_sections
   let(:file) {"some/file.erb"}
   subject {described_class.new(file)}
 
+  it_behaves_like "a processor"
 
   describe "#handle_yield" do
     valid_sections.each do |key, content|

diff --git a/spec/build_tools/compiler/ejs_processor_spec.rb b/spec/build_tools/compiler/ejs_processor_spec.rb
@@ -23,6 +23,7 @@ def valid_sections
   let(:file) {"some/file.erb"}
   subject {described_class.new(file)}
 
+  it_behaves_like "a processor"
 
   describe "#handle_yield" do
     valid_sections.each do |key, content|

diff --git a/spec/build_tools/compiler/jinja_processor_spec.rb b/spec/build_tools/compiler/jinja_processor_spec.rb
@@ -27,6 +27,7 @@ def valid_sections
   let(:file) {"some/file.erb"}
   subject {described_class.new(file)}
 
+  it_behaves_like "a processor"
 
   describe "#handle_yield" do
     valid_sections.each do |key, content|

diff --git a/spec/build_tools/compiler/liquid_processor_spec.rb b/spec/build_tools/compiler/liquid_processor_spec.rb
@@ -0,0 +1,11 @@
+require 'spec_helper'
+require File.join(PROJECT_ROOT, 'build_tools/compiler/liquid_processor.rb')
+
+describe Compiler::LiquidProcessor do
+
+  let(:file) {"some/file.erb"}
+  subject {described_class.new(file)}
+
+  it_behaves_like "a processor"
+
+end
diff --git a/spec/build_tools/compiler/mustache_inheritance_processor_spec.rb b/spec/build_tools/compiler/mustache_inheritance_processor_spec.rb
@@ -0,0 +1,11 @@
+require 'spec_helper'
+require File.join(PROJECT_ROOT, 'build_tools/compiler/mustache_inheritance_processor.rb')
+
+describe Compiler::MustacheInheritanceProcessor do
+
+  let(:file) {"some/file.erb"}
+  subject {described_class.new(file)}
+
+  it_behaves_like "a processor"
+
+end
diff --git a/spec/build_tools/compiler/mustache_processor_spec.rb b/spec/build_tools/compiler/mustache_processor_spec.rb
@@ -19,10 +19,10 @@ def valid_sections
 end
 
 describe Compiler::MustacheProcessor do
-
   let(:file) {"some/file.erb"}
   subject {described_class.new(file)}
 
+  it_behaves_like "a processor"
 
   describe "#handle_yield" do
     valid_sections.each do |key, content|
@@ -64,5 +64,4 @@ def valid_sections
       end
     end
   end
-
 end
diff --git a/spec/build_tools/compiler/plain_processor_spec.rb b/spec/build_tools/compiler/plain_processor_spec.rb
@@ -0,0 +1,11 @@
+require 'spec_helper'
+require File.join(PROJECT_ROOT, 'build_tools/compiler/plain_processor.rb')
+
+describe Compiler::PlainProcessor do
+
+  let(:file) {"some/file.erb"}
+  subject {described_class.new(file)}
+
+  it_behaves_like "a processor"
+
+end
diff --git a/spec/build_tools/compiler/play_processor_spec.rb b/spec/build_tools/compiler/play_processor_spec.rb
@@ -34,6 +34,8 @@ def expected_parameter_names
 describe Compiler::PlayProcessor do
   subject { described_class.new("dummy filename") }
 
+  it_behaves_like "a processor"
+
   describe "top_of_page" do
     it "declares all of the template parameters" do
       expected_parameter_names.each do |parameter_name|

diff --git a/spec/support/examples/processor.rb b/spec/support/examples/processor.rb
@@ -0,0 +1,80 @@
+require 'spec_helper'
+require 'set'
+
+shared_examples_for "a processor" do
+  let(:html_erb_file) { "a/file.css" }
+  let(:processor) { described_class.new(html_erb_file) }
+
+  describe "convert rails tags into html" do
+
+    let(:css_source)        { "govuk-template.css" }
+    let(:js_source)         { "ie.js" }
+
+    describe "#stylesheet_link_tag" do
+      let(:css_options)     { {"media" => "print"} }
+      let(:sri_attributes)  { {"integrity" => true, "crossorigin" => "anonymous"} }
+
+      it "should parse the stylesheet tag" do
+        expect(processor.stylesheet_link_tag(css_source)).to eql("<link rel=\"stylesheet\" media=\"screen\" href=\"#{processor.asset_path(css_source)}\"/>")
+      end
+
+      context "if css file is for print" do
+        it "should parse the stylesheet tag and extra options" do
+          expect(processor.stylesheet_link_tag(css_source, css_options)).to eql("<link rel=\"stylesheet\" media=\"print\" href=\"#{processor.asset_path(css_source)}\"/>")
+        end
+      end
+
+      context "if sri attributes are present, it should ignore them" do
+        it "should parse the stylesheet tag without the integrity attribute" do
+          expect(processor.stylesheet_link_tag(css_source, sri_attributes)).to eql("<link rel=\"stylesheet\" media=\"screen\" href=\"#{processor.asset_path(css_source)}\"/>")
+        end
+      end
+    end
+
+    describe "#javascript_include_tag" do
+      let(:js_options)      { {"charset" => "UTF-8"} }
+      let(:sri_attributes)  { {"integrity" => true, "crossorigin" => "anonymous"} }
+
+      it "should parse the javascript tag" do
+        expect(processor.javascript_include_tag(js_source)).to eql("<script src=\"#{processor.asset_path(js_source)}\"></script>")
+      end
+
+      it "should parse the javascript tag and extra options" do
+        expect(processor.javascript_include_tag(js_source, js_options)).to eql("<script src=\"#{processor.asset_path(js_source)}\" charset=\"UTF-8\"></script>")
+      end
+
+      it "if sri attributes are present, it should ignore them" do
+        expect(processor.javascript_include_tag(js_source, sri_attributes)).to eql("<script src=\"#{processor.asset_path(js_source)}\"></script>")
+      end
+    end
+
+    describe "#content_tag" do
+      it "should return the correct html script tag" do
+        expect(processor.content_tag(:script, " src=\"#{processor.asset_path(js_source)}\"")).to eql("<script src=\"#{processor.asset_path(js_source)}\"></script>")
+      end
+    end
+
+    describe "#tag" do
+      it "should return the correct html link tag" do
+        expect(processor.tag(:link, " rel=\"stylesheet\" media=\"screen\" href=\"#{processor.asset_path(css_source)}\"")).to eql("<link rel=\"stylesheet\" media=\"screen\" href=\"#{processor.asset_path(css_source)}\"/>")
+      end
+    end
+
+    describe "#tag_options" do
+      let(:options) { {"rel"=>"stylesheet", "media"=>"screen", "href"=>processor.asset_path(css_source) } }
+
+      it "flattens the hash into a string of quoted html attributes" do
+        expect(processor.tag_options(options)).to eql(" rel=\"stylesheet\" media=\"screen\" href=\"#{processor.asset_path(css_source)}\"")
+      end
+    end
+
+    describe "#exclude_sri_fields" do
+      let(:options) { {"rel"=>"stylesheet", "media"=>"screen", "href"=>processor.asset_path(css_source), "integrity" => true, "crossorigin" => "anonymous" } }
+
+      it "should remove the integrity and crossorigin keys from the hash" do
+        expect(processor.exclude_sri_fields(options)).to eql({"href" => processor.asset_path(css_source), "media" => "screen", "rel" => "stylesheet"})
+      end
+    end
+
+  end
+end
diff --git a/spec/support/uses_of_yield.rb b/spec/support/uses_of_yield.rb
@@ -32,6 +32,12 @@ def asset_path(*args)
   def method_missing(name, *args)
     puts "#{name} #{args.inspect}"
   end
+
+  def stylesheet_link_tag(*sources)
+  end
+
+  def javascript_include_tag(*sources)
+  end
 end
 
 # return an array of unique values passed to yield in the templates