feat: add check for trustworthy/non-trustworthy urls

lib/fetch/util.js

@@ -343,20 +343,44 @@ function determineRequestsReferrer (request) {
     ? referrerOrigin = stripURLForReferrer(referrerSource, true)
     : temp
   const areSameOrigin = sameOrigin(request, referrerUrl)
+  const isNonPotentiallyTrustWorthy = isURLPotentiallyTrustworthy(referrerUrl) &&
+    !isURLPotentiallyTrustworthy(request.url)
 
   // NOTE: How to treat step 7?
   // 8. Execute the switch statements corresponding to the value of policy:
   switch (policy) {
     case 'origin': return referrerOrigin
     case 'unsafe-url': return referrerUrl
-    // TODO: assess if trustworthy or not
-    case 'strict-origin': return referrerOrigin
+    case 'strict-origin':
+      /**
+       * 1. If referrerURL is a potentially trustworthy URL and
+       * request’s current URL is not a potentially trustworthy URL,
+       * then return no referrer.
+       * 2. Return referrerOrigin
+       */
+      return isNonPotentiallyTrustWorthy ? 'no-referrer' : referrerOrigin
     case 'strict-origin-when-cross-origin':
+      /**
+       * 1. If the origin of referrerURL and the origin of request’s current URL are the same,
+       * then return referrerURL.
+       * 2. If referrerURL is a potentially trustworthy URL and request’s current URL is not a
+       * potentially trustworthy URL, then return no referrer.
+       * 3. Return referrerOrigin
+      */
+      if (areSameOrigin) return referrerOrigin
+      else return isNonPotentiallyTrustWorthy ? 'no-referrer' : referrerOrigin
+    case 'same-origin':
       return areSameOrigin ? referrerOrigin : 'no-referrer'
     case 'origin-when-cross-origin':
       return areSameOrigin ? referrerUrl : referrerOrigin
     case 'no-referrer-when-downgrade':
-      return referrerUrl
+      /**
+       * 1. If referrerURL is a potentially trustworthy URL and
+       * request’s current URL is not a potentially trustworthy URL,
+       * then return no referrer.
+       * 2. Return referrerOrigin
+      */
+      return isNonPotentiallyTrustWorthy ? 'no-referrer' : referrerOrigin
   }
 
   function stripURLForReferrer (url, originOnly = false) {
@@ -372,8 +396,42 @@ function determineRequestsReferrer (request) {
 
     return urlObject.href
   }
+}
+
+function isURLPotentiallyTrustworthy (url) {
+  if (!(url instanceof URL)) {
+    return false
+  }
+
+  if (url.href === 'about:blank' || url.href === 'about:srcdoc') {
+    return true
+  }
+
+  if (url.protocol === 'data:') return true
+
+  return isOriginPotentiallyTrustworthy(url.origin)
+
+  function isOriginPotentiallyTrustworthy(origin) {
+    if (origin == null || origin === 'null') return false
 
-  return 'no-referrer'
+    let originAsURL
+
+    try { originAsURL = new URL(origin) } catch (e) { return false }
+
+    if (originAsURL.protocol === 'https:' || originAsURL.protocol === 'wss:') {
+      return true
+    }
+
+    if (/^127(?:\.[0-9]+){0,2}\.[0-9]+$|^(?:0*:)*?:?0*1$/.test(originAsURL.hostname) ||
+     (originAsURL.hostname === 'localhost' || originAsURL.hostname.includes('localhost.')) ||
+     (originAsURL.hostname.endsWith('.localhost'))) {
+      return true
+    }
+
+    if (originAsURL.protocol === 'file:') return true
+
+    return false
+  }
 }
 
 function matchRequestIntegrity (request, bytes) {