Respect DNT header

Do Not Track (DNT) is an old web standard in order to notify pages that
the user doesn't want to be tracked. Even while a lot of pages either
ignore this header or even worse, use it for tracking purposes, the
orignal intention of this header is good and should be adopted.

This patch implements a respect of the DNT header by no longer including
the optional Google Analytics and disqus integrations when sending a DNT
header. This should reduce outside resource usage and help to stay more
private.

This should later-on extended towards other document content (i.e.
iframe based content).

The reason to not change the CDN handling is that CDNs will be
deprecated with next release and removed in long term.

Signed-off-by: Sheogorath <sheogorath@shivering-isles.com>

4 files changed, 7 insertions, 5 deletions

diff --git a/lib/response.js b/lib/response.js
index dd33e42b..1313f9f4 100644
--- a/lib/response.js
+++ b/lib/response.js
@@ -226,7 +226,8 @@ function showPublishNote (req, res, next) {
         robots: meta.robots || false, // default allow robots
         GA: meta.GA,
         disqus: meta.disqus,
-        cspNonce: res.locals.nonce
+        cspNonce: res.locals.nonce,
+        dnt: req.headers.dnt
       }
       return renderPublish(data, res)
     }).catch(function (err) {
@@ -608,7 +609,8 @@ function showPublishSlide (req, res, next) {
         robots: meta.robots || false, // default allow robots
         GA: meta.GA,
         disqus: meta.disqus,
-        cspNonce: res.locals.nonce
+        cspNonce: res.locals.nonce,
+        dnt: req.headers.dnt
       }
       return renderPublishSlide(data, res)
     }).catch(function (err) {
diff --git a/public/views/pretty.ejs b/public/views/pretty.ejs
index 9604d422..1970ab2f 100644
--- a/public/views/pretty.ejs
+++ b/public/views/pretty.ejs
@@ -63,7 +63,7 @@
         </div>
     </div>
     <div id="ui-toc-affix" class="ui-affix-toc ui-toc-dropdown unselectable hidden-print" data-spy="affix" style="display:none;"></div>
-    <% if(typeof disqus !== 'undefined' && disqus) { %>
+    <% if(typeof disqus !== 'undefined' && disqus && !dnt) { %>
     <div class="container-fluid" style="max-width: 758px; margin-bottom: 40px;">
         <%- include shared/disqus %>
     </div>
diff --git a/public/views/shared/ga.ejs b/public/views/shared/ga.ejs
index 27abb742..f6b807fb 100644
--- a/public/views/shared/ga.ejs
+++ b/public/views/shared/ga.ejs
@@ -1,4 +1,4 @@
-<% if(typeof GA !== 'undefined' && GA) { %>
+<% if(typeof GA !== 'undefined' && GA && !dnt) { %>
 <script nonce="<%= cspNonce %>">
 (function (i, s, o, g, r, a, m) {
     i['GoogleAnalyticsObject'] = r;
diff --git a/public/views/slide.ejs b/public/views/slide.ejs
index ff4be9e9..3331b85d 100644
--- a/public/views/slide.ejs
+++ b/public/views/slide.ejs
@@ -78,7 +78,7 @@
                         <% } %>
                     </small>
                 </div>
-                <% if(typeof disqus !== 'undefined' && disqus) { %>
+                <% if(typeof disqus !== 'undefined' && disqus && !dnt) { %>
                 <div class="slides-disqus">
                     <%- include shared/disqus %>
                 </div>