Allow loopback address urls as exception to loading from secure contexts

Fixes #486

lib/main.js

@@ -77,7 +77,10 @@ function SockJS(url, protocols, options) {
   var secure = parsedUrl.protocol === 'https:';
   // Step 2 - don't allow secure origin with an insecure protocol
   if (loc.protocol === 'https:' && !secure) {
-    throw new Error('SecurityError: An insecure SockJS connection may not be initiated from a page loaded over HTTPS');
+    // exception is 127.0.0.0/8 and ::1 urls
+    if (!urlUtils.isLoopbackAddr(parsedUrl.host)) {
+      throw new Error('SecurityError: An insecure SockJS connection may not be initiated from a page loaded over HTTPS');
+    }
   }
 
   // Step 3 - check port access - no need here

lib/utils/url.js

@@ -44,4 +44,8 @@ module.exports = {
 , addQuery: function (url, q) {
     return url + (url.indexOf('?') === -1 ? ('?' + q) : ('&' + q));
   }
+
+, isLoopbackAddr: function (addr) {
+    return /^127\.([0-9]{1,3})\.([0-9]{1,3})\.([0-9]{1,3})$/i.test(addr) || /^::1$/.test(addr);
+  }
 };

tests/lib/main-node.js

@@ -22,6 +22,19 @@ describe('SockJS', function() {
         });
       });
 
+      // https://www.w3.org/TR/secure-contexts/#is-origin-trustworthy
+      it('should NOT throw SecurityError for 127.0.0.1/8 url from a secure page', function () {
+        expect(function () {
+          sjs('http://127.0.0.1');
+        }).to.not.throwException();
+      });
+
+      it('should NOT throw SecurityError for ::1 url from a secure page', function () {
+        expect(function () {
+          sjs('http://::1');
+        }).to.not.throwException();
+      });
+
       it('should throw SyntaxError for an invalid url', function () {
         expect(function () {
           sjs('//localhost');