Clean up html on the website.

- Fixes some html validation issues.
- Fixes links on security basics blog post.
- Adds rel=noopener to links with target=_blank and adds a check to
  htmlproofer.
- Add favicon check to htmlproofer.

Fixes #3286
Fixes #3284

PiperOrigin-RevId: 321892602

2 files changed, 37 insertions, 0 deletions

diff --git a/images/jekyll/Dockerfile b/images/jekyll/Dockerfile
index 4860dd750..ba039ba15 100644
--- a/images/jekyll/Dockerfile
+++ b/images/jekyll/Dockerfile
@@ -10,4 +10,5 @@ RUN gem install \
         jekyll-relative-links:0.6.1 \
         jekyll-feed:0.13.0 \
         jekyll-sitemap:1.4.0
+COPY checks.rb /checks.rb
 CMD ["/usr/gem/gems/jekyll-4.0.0/exe/jekyll", "build", "-t", "-s", "/input", "-d", "/output"]
diff --git a/images/jekyll/checks.rb b/images/jekyll/checks.rb
new file mode 100644
index 000000000..fc7e6b5a8
--- /dev/null
+++ b/images/jekyll/checks.rb
@@ -0,0 +1,36 @@
+#!/usr/local/bin/ruby
+#
+# HTMLProofer checks for the gVisor website.
+#
+require 'html-proofer'
+
+# NoOpenerCheck checks to make sure links with target=_blank include the
+# rel=noopener attribute.
+class NoOpenerCheck < ::HTMLProofer::Check
+  def run
+    @html.css('a').each do |node|
+      link = create_element(node)
+      line = node.line
+
+      rel = link.respond_to?(:rel) ? link.rel.split(' ') : []
+
+      if link.respond_to?(:target) && link.target == "_blank" && !rel.include?("noopener")
+        return add_issue("You should set rel=noopener for links with target=_blank", line: line)
+      end
+    end
+  end
+end
+
+def main()
+  options = {
+    :check_html => true,
+    :check_favicon => true,
+    :disable_external => true,
+  }
+
+  HTMLProofer.check_directories(ARGV, options).run
+end
+
+if __FILE__ == $0
+  main
+end