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Unified Diff: lib/content/snippets.js

Issue 29886700: Issue 6969 - Implement abort-on-property-read snippet (Closed) Base URL: https://hg.adblockplus.org/adblockpluscore/
Patch Set: More changes from review Created Oct. 25, 2018, 2:32 p.m.
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Index: lib/content/snippets.js
===================================================================
--- a/lib/content/snippets.js
+++ b/lib/content/snippets.js
@@ -486,8 +486,73 @@
{
event.preventDefault();
}
},
true);
}
exports["prevent-inline-scripts"] = preventInlineScripts;
+
+/**
+ * Generates a random alphanumeric ID consisting of 6 chars base-36 digits
Manish Jethani 2018/10/25 16:12:16 s/chars//
hub 2018/10/25 20:26:10 Done.
+ * from the range 100000..zzzzzz (both inclusive).
+ *
+ * @returns {string} The random ID.
+ */
+function randomId()
+{
+ // 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 currentDescriptor = Object.getOwnPropertyDescriptor(object, property);
+ if (!currentDescriptor)
+ currentDescriptor = {};
+ if (typeof descriptor.get != "undefined")
+ currentDescriptor.get = descriptor.get;
+ if (typeof descriptor.set != "undefined")
+ currentDescriptor.set = descriptor.set;
+ Object.defineProperty(object, property, currentDescriptor);
+}
+
+/**
+ * Will patch a property on the window object to abort when read.
+ * It will intercept the onerror callback and block it if tagged.
+ * The idea originates from
+ * https://github.com/uBlockOrigin/uAssets/blob/80b195436f8f8d78ba713237bfc268ecfc9d9d2b/filters/resources.txt#L1703
+ *
+ * @todo handle properties of properties.
+ *
+ * @param {string} property the name of the property.
+ */
+function abortOnPropertyRead(property)
+{
+ if (!property)
+ return;
+
+ let rid = randomId();
+
+ function abort()
+ {
+ throw new ReferenceError(rid);
+ }
+
+ let {onerror} = window;
+ window.onerror = (message, ...rest) =>
+ {
+ if (typeof message == "string" && message.includes(rid))
+ return true;
+ if (typeof onerror == "function")
+ return onerror(message, ...rest);
+ };
+
+ wrapPropertyAccess(window, property, {get: abort, set() {}});
+}
+
+exports["abort-on-property-read"] = makeInjector(abortOnPropertyRead,
+ wrapPropertyAccess,
+ randomId);
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