Issue 7236 - Handle sub properties in abort-on-property snippets

lib/content/snippets.js

 /*
  * This file is part of Adblock Plus <https://adblockplus.org/>,
  * Copyright (C) 2006-present eyeo GmbH
  *
  * Adblock Plus is free software: you can redistribute it and/or modify
  * it under the terms of the GNU General Public License version 3 as
  * published by the Free Software Foundation.
  *
  * Adblock Plus is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
@@ skipping 682 matching lines @@
   // 2176782336 is 36^6 which mean 6 chars [a-z0-9]
   // 60466176 is 36^5
   // 2176782336 - 60466176 = 2116316160. This ensure to always have 6
   // chars even if Math.random() returns its minimum value 0.0
   //
   return Math.floor(Math.random() * 2116316160 + 60466176).toString(36);
 }
 
 function wrapPropertyAccess(object, property, descriptor)
 {
-  let dot = property.indexOf(".");
-  if (dot == -1)
+  let dotIndex = property.indexOf(".");
+  if (dotIndex == -1)
   {
     // simple property case.
     let currentDescriptor = Object.getOwnPropertyDescriptor(object, property);
     if (currentDescriptor && !currentDescriptor.configurable)
-      return false;
+      return;
 
     Object.defineProperty(object, property, descriptor);
-    return true;
+    return;
   }
-  let result = true;
-  let name = property.slice(0, dot);
-  property = property.slice(dot + 1);
+
+  let name = property.slice(0, dotIndex);
+  property = property.slice(dotIndex + 1);
   let value = object[name];
   if (value && typeof value == "object")
-    result = wrapPropertyAccess(value, property, descriptor);
+    wrapPropertyAccess(value, property, descriptor);
 
   let currentDescriptor = Object.getOwnPropertyDescriptor(object, name);
   if (currentDescriptor && !currentDescriptor.configurable)
-    return result;

[Manish Jethani, 2019/03/04 13:28:49]

If I understand this correctly, we return the result of the leaf property. i.e.
in `foo.bar.lambda`, if `foo.bar = {}`, we return whether we wrapped `lambda`.
However if `foo.bar` is not an object, then we basically always return `true` -
even if the descriptor for `foo.bar` is non-configurable.

For example:

 window.foo = {};
 Object.defineProperty(window.foo, "bar", {value: "fixed value"});

Now wrapping `foo.bar.lambda` will return `true`. Right?

This is another inconsistency. I'm wondering if we really need a return value?
We could always just override the `onerror` handler in the calling code, it
shouldn't matter if it is wrapped multiple times.

[hub, 2019/03/05 13:49:13]

I should have set `result` to `false` (line 714). Fixing this.

[Manish Jethani, 2019/03/06 19:07:12]

This has the opposite problem though. If we're trying to wrap `foo.bar.lambda`
and `foo` exists but `foo.bar` does not exist, it will return `false`; but later
when `foo.bar` is set, and then `foo.bar.lambda` is set, then `foo.bar.lambda`
will be wrapped. But because we returned `false` initially there will be no
`onerror` handler.

It's hard to do this right. How about we just always add an `onerror` handler
and return neither `true` nor `false` from this function?

[hub, 2019/03/06 21:22:03]

Silly me, I should just return true at then end since we did define the
property.

I'm ok to make the creation of the onerror handler unconditional.

-
-  let setter = a =>

[Manish Jethani, 2019/03/04 13:28:49]

Nit: Instead of `a` this would seem better as `newValue`.

[hub, 2019/03/05 13:49:13]

Done.

-  {
-    value = a;
-    if (a && typeof a == "object")
-      wrapPropertyAccess(a, property, descriptor);
+    return;
+
+  let setter = newValue =>
+  {
+    value = newValue;
+    if (newValue && typeof newValue == "object")
+      wrapPropertyAccess(newValue, property, descriptor);
   };
+
   Object.defineProperty(object, name, {get: () => value, set: setter});
-  return result;
 }
 
 /**
  * Overrides the <code>onerror</code> handler to discard tagged error messages
  * from our property wrapping.
  *
  * @param {string} magic The magic string that tags the error message.
  */
 function overrideOnError(magic)
 {
@@ skipping 23 matching lines @@
   if (!property)
     return;
 
   let rid = randomId();
 
   function abort()
   {
     throw new ReferenceError(rid);
   }
 
-  if (wrapPropertyAccess(window, property, {get: abort, set() {}}))
-    overrideOnError(rid);
+  wrapPropertyAccess(window, property, {get: abort, set() {}});
+  overrideOnError(rid);
 }
 
 exports["abort-on-property-read"] = makeInjector(abortOnPropertyRead,
                                                  wrapPropertyAccess,
                                                  overrideOnError,
                                                  randomId);
 
 /**
  * Patches a property on the window object to abort execution when the
  * property is written.
@@ skipping 10 matching lines @@
   if (!property)
     return;
 
   let rid = randomId();
 
   function abort()
   {
     throw new ReferenceError(rid);
   }
 
-  if (wrapPropertyAccess(window, property, {set: abort}))
-    overrideOnError(rid);
+  wrapPropertyAccess(window, property, {set: abort});
+  overrideOnError(rid);
 }
 
 exports["abort-on-property-write"] = makeInjector(abortOnPropertyWrite,
                                                   wrapPropertyAccess,
                                                   overrideOnError,
                                                   randomId);
 
 /**
  * Aborts the execution of an inline script.
  *
@@ skipping 12 matching lines @@
 
 
   let object = window;
   let path = api.split(".");
   let name = path.pop();
 
   for (let node of path)
   {
     object = object[node];
 
-    if (!object || typeof object != "object")
+    if (!object || !(typeof object == "object" || typeof object == "function"))
       return;
   }
 
   let currentValue = object[name];
 
   let abort = () =>
   {
     let element = document.currentScript;
     if (element instanceof HTMLScriptElement && element.src == "" &&
         element != us && (!re || re.test(element.textContent)))
     {
       throw new ReferenceError(rid);
     }
   };
 
   let descriptor = {
     get()
     {
       abort();
       return currentValue;
     },
     set(value)
     {
       abort();
       currentValue = value;
     }
   };
 
-  if (wrapPropertyAccess(object, name, descriptor))
-    overrideOnError(rid);
+  wrapPropertyAccess(object, name, descriptor);
+  overrideOnError(rid);
 }
 
 exports["abort-current-inline-script"] =
   makeInjector(abortCurrentInlineScript, wrapPropertyAccess, toRegExp,
                overrideOnError, regexEscape, randomId);
 
 /**
  * Strips a query string parameter from <code>fetch()</code> calls.
  *
  * @param {string} name The name of the parameter.
@@ skipping 15 matching lines @@
       let url = new URL(source);
       url.searchParams.delete(name);
       args[0] = url.href;
     }
     return fetch_.apply(this, args);
   };
 }
 
 exports["strip-fetch-query-parameter"] = makeInjector(stripFetchQueryParameter,
                                                       toRegExp, regexEscape);