Webgl hook refactored on nscl/content/patchWindow.js and made Chromium-compatibile.

Author: hackademix

src/content/webglHook.js

@@ -1,91 +1,41 @@
-if (typeof exportFunction === "function") ns.on("capabilities", event => {
+// depends on nscl/content/patchWindow.js
+"use strict";
+ns.on("capabilities", event => {
   debug("WebGL Hook", document.URL, document.documentElement && document.documentElement.innerHTML, ns.capabilities); // DEV_ONLY
   if (ns.allows("webgl")) return;
-
-  // win: window object to modify.
-  // modifyTarget: callback to function that modifies the desired properties
-  //                or methods. Callback must take target window as argument.
-  function modifyWindow(win, modifyTarget) {
+  let env = {eventName: `nsWebgl:${uuid()}`};
+  window.addEventListener(env.eventName, e => {
+    let canvas = e.target;
+    if (!(canvas instanceof HTMLCanvasElement)) return;
+    let request = {
+      id: "noscript-webgl",
+      type: "webgl",
+      url: document.URL,
+      documentUrl: document.URL,
+      embeddingDocument: true,
+    };
+    seen.record({policyType: "webgl", request, allowed: false});
     try {
-      modifyTarget(win);
-      modifyWindowOpenMethod(win, modifyTarget);
-      modifyFramingElements(win, modifyTarget);
+      let ph = PlaceHolder.create("webgl", request);
+      ph.replace(canvas);
+      PlaceHolder.listen();
     } catch (e) {
-      if (e instanceof DOMException && e.name === "SecurityError") {
-        // In case someone tries to access SOP restricted window.
-        // We can just ignore this.
-      } else throw e;
+      error(e);
     }
-  }
-
-  function modifyWindowOpenMethod(win, modifyTarget) {
-    let windowOpen = win.wrappedJSObject ? win.wrappedJSObject.open : win.open;
-    exportFunction(function(...args) {
-      let newWin = windowOpen.call(this, ...args);
-      if (newWin) modifyWindow(newWin, modifyTarget);
-      return newWin;
-    }, win, {defineAs: "open"});
-  }
-
-  function modifyFramingElements(win, modifyTarget) {
-    for (let property of ["contentWindow", "contentDocument"]) {
-      for (let interface of ["Frame", "IFrame", "Object"]) {
-        let proto = win[`HTML${interface}Element`].prototype;
-        modifyContentProperties(proto, property, modifyTarget)
-      }
-    }
-  }
+    notifyPage();
+  }, true);
 
-  function modifyContentProperties(proto, property, modifyTarget) {
-    let descriptor = Object.getOwnPropertyDescriptor(proto, property);
-    let origGetter = descriptor.get;
-    let replacementFn;
-
-    if (property === "contentWindow") { replacementFn = function() {
-      let win = origGetter.call(this);
-      if (win) modifyWindow(win, modifyTarget);
-      return win;
-    }}
-    if (property === "contentDocument") { replacementFn = function() {
-      let document = origGetter.call(this);
-      if (document && document.defaultView) modifyWindow(document.defaultView, modifyTarget);
-      return document;
-    }}
-
-    descriptor.get = exportFunction(replacementFn, proto, {defineAs: `get $property`});
-    let wrappedProto = proto.wrappedJSObject || proto;
-    Object.defineProperty(wrappedProto, property, descriptor);
-  }
-
-  //
-
-  function modifyGetContext(win) {
+  function modifyGetContext(win, env) {
       let proto = win.HTMLCanvasElement.prototype;
       let getContext = proto.getContext;
       exportFunction(function(type, ...rest) {
         if (type && type.toLowerCase().includes("webgl")) {
-          let request = {
-            id: "noscript-webgl",
-            type: "webgl",
-            url: document.URL,
-            documentUrl: document.URL,
-            embeddingDocument: true,
-          };
-          seen.record({policyType: "webgl", request, allowed: false});
-          try {
-            let ph = PlaceHolder.create("webgl", request);
-            ph.replace(this);
-            PlaceHolder.listen();
-          } catch (e) {
-            error(e);
-          }
-          notifyPage();
+          this.dispatchEvent(new Event(env.eventName));
           return null;
         }
         return getContext.call(this, type, ...rest);
       }, proto, {defineAs: "getContext"});
   }
 
-  modifyWindow(window, modifyGetContext);
-
+  patchWindow(modifyGetContext, env);
 });

src/nscl/content/patchWindow.js

@@ -1,6 +1,6 @@
 "use strict";
 
-function patchWindow(patchingCallback, targetWindow = window) {
+function patchWindow(patchingCallback, env = {}) {
   let nativeExport = this && this.exportFunction || typeof exportFunction == "function";
   if (!nativeExport) {
     // Chromium
@@ -26,7 +26,7 @@ function patchWindow(patchingCallback, targetWindow = window) {
         patchWindow,
         exportFunction,
         cloneInto,
-      }).patchWindow(${patchingCallback});
+      }).patchWindow(${patchingCallback}, ${JSON.stringify(env)});
     })();
     `;
     document.documentElement.insertBefore(script, document.documentElement.firstChild);
@@ -39,7 +39,7 @@ function patchWindow(patchingCallback, targetWindow = window) {
   //                or methods. Callback must take target window as argument.
   function modifyWindow(win, modifyTarget) {
     try {
-      modifyTarget(win.wrappedJSObject || win);
+      modifyTarget(win.wrappedJSObject || win, env);
       modifyWindowOpenMethod(win, modifyTarget);
       modifyFramingElements(win, modifyTarget);
     } catch (e) {
@@ -88,6 +88,6 @@ function patchWindow(patchingCallback, targetWindow = window) {
     let wrappedProto = proto.wrappedJSObject || proto;
     Object.defineProperty(wrappedProto, property, descriptor);
   }
-  
-  return modifyWindow(targetWindow, patchingCallback);
+
+  return modifyWindow(window, patchingCallback);
 }