某车联网APP加固分析

汽车安全 2年前 (2022) admin

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某车联网APP加固分析

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看雪论坛作者ID：侬本多情

一

分析前准备

目标App：比亚迪汽车 6.1.0

工具：Cydia、Frida、Objection、Storm Sniffer(抓包)

二

抓包

首先打开Storm Sniffer，该AppStore可下载。（使用fiddler也可以）
目标App开启了SSLPinning，导致无法抓包。

通过objection绕过SSLPinning

objection -g 比亚迪汽车 exploreios sslpinning disable --quiet

接下来可以看到抓包内容了。

软件提示：账号密码错误

https://dilinkappserver.byd.com/app/auth/loginUser-Agent: bi ya di qi che/6.0.1 (iPhone; iOS 14.0; Scale/3.00)Content-Type: application/jsonHost: dilinkappserver.byd.com {"request":"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"} {"response":"Fel63A3fJsBnqDNoqrf3sNRYntlgl2bMzWrA56aEQZRggnMBao9z1ds1G/TqV2TMwrRu1wovdv5AwWkDlpdqO0A=="}

三

砸壳

使用 frida-ios-dump进行砸壳dump出ipa文件，找到包内二进制文件，拖入IDA中分析。

四

加密点

4.1 思路：Frida hook -[NSURLRequest initWithURL:] 打印其调用堆栈

    try {         var className = "NSURLRequest";        var funcName = "- initWithURL:";         var hook = eval('ObjC.classes.' + className + '["' + funcName + '"]');        Interceptor.attach(hook.implementation, {             onEnter: function(args) {                console.log(colors.green,"NSURLRequest with URL: ",colors.resetColor + ObjC.Object(args[2]));                console.log("nBacktrace:n" + Thread.backtrace(this.context, Backtracer.ACCURATE).map(DebugSymbol.fromAddress).join("n"));            },         });     } catch (error) {        console.log(colors.red,"[!] Exception: ",colors.resetColor + error.message);    }

输出如下：

[iPhone::比亚迪汽车 ]->  NSURLRequest with URL:  https://dilinkappserver.byd.com/app/auth/loginBacktrace:0x1057d943c /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!-[AFHTTPRequestSerializer requestWithMethod:URLString:parameters:error:]0x1057d106c /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!-[AFHTTPSessionManager dataTaskWithHTTPMethod:URLString:parameters:headers:uploadProgress:downloadProgress:success:failure:]0x1057d0780 /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!-[AFHTTPSessionManager POST:parameters:headers:progress:success:failure:]0x1049e1e24 /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!+[AFNRequestUtls postRequestWithInfo:successBlock:failedBlock:]0x104b4d270 /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!+[BYDHttpsRequestUtils httpsPostRequestWithRequestRequestInfo:successBlock:failedBlock:]0x1048f48fc /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!-[BYDUserModel doLoginSuccess:failed:]0x104a4c4f8 /private/var/containers/Bundle/Application/48133A5D-90E1-494C-8472-79C2B5DE912B/比亚迪汽车.app/比亚迪汽车!-[BYDLoginVC doLogin]...

根据AFHTTPRequestSerializer可以判断出该App使用了 AFNetwoking库（https://github.com/AFNetworking/AFNetworking）。

继续hook -[AFHTTPRequestSerializer requestWithMethod:URLString:parameters:error:] 获取parameters参数，内容为加密后参数。

可以判断出加密点在+ [BYDHttpsRequestUtils httpsPostRequestWithRequestRequestInfo:successBlock:failedBlock:] 方法内。

4.2 ida 查看+ [BYDHttpsRequestUtils httpsPostRequestWithRequestRequestInfo:successBlock:failedBlock:]

这里使用Hopper反编译出现了一些问题（这里不知道Hopper如何更改函数范围，有大佬知道可以留言）。

看一眼CFG图。控制流混淆，稳住，问题不大，先看伪代码试试。

这里创建了网络请求 requestInfo实例，找一下设置参数的函数调用。

这里找到了，+[BYDDataManager entryRequestInfo:]这个方法返回加密内容，传入的v6是明文消息字典的aes加密，密钥为$key+$value拼接sha1（先挖个坑，这里讲起来太复杂），再跟进一下康康。

离谱了。再继续看看伪代码：

看到request字符串了，上面有个BangSafeSDK可以确定是梆梆企业的加密了，再继续深入看看+[BangSafeSDK checkcode:dataStyle:]，结果utf8 编码、获取当前时间，最终调用了sub_1023BE0D4。

这里本来想看看sub_1023BE0D4的CFG,IDA直接给报错了，节点太多。

怎么办呢？盲猜一手控制流混淆（已经习惯了），上trace！

Frida Stalker trace一下调用地址，感谢misskings大佬。

/// <reference path="frida-gum.d.ts" />  //+[BYDHttpsRequestUtils httpsPostRequestWithRequestRequestInfo:successBlock:failedBlock:]var target = ObjC.classes['BYDHttpsRequestUtils']['+ httpsPostRequestWithRequestRequestInfo:successBlock:failedBlock:']console.log(target.implementation) var m = Process.getModuleByAddress(target.implementation)var vm = m.base.add(0x23BE0D4)//注意ida加载二进制文件的基地址var baseAddr = m.baseconsole.log(vm);Interceptor.attach(vm, {    onEnter: function (args) {        console.log("enter")        this.tid = Process.getCurrentThreadId()        console.log(this.tid);        Stalker.follow(this.tid, {            events: {                // 暂时不需要这些 events                call: false,                ret: false,                exec: false,                 block: false,                compile: false            },             transform: function (iterator) {                 var instruction = iterator.next();                const startAddress = instruction.address;                                    // 从ida里面 找到 sub_1023BE0D4 函数的地址范围，alt+p                var is = startAddress.compare(baseAddr.add(0x23CBB6C))<0 && startAddress.compare(baseAddr.add(0x23BE0D4))>=0;                do{                        if(is){                            console.log(instruction.address.sub(baseAddr).add(0x100000000) + ":" + instruction);                        }                     iterator.keep();                } while ((instruction = iterator.next()) !== null);              }        })     },    onLeave: function (ret) {        Stalker.unfollow(this.tid)    }})

trace 的指令如下：

0x1023be0e4:stp x20, x19, [sp, #0x40]0x1023be0e8:stp x29, x30, [sp, #0x50]0x1023be0ec:add x29, sp, #0x500x1023be0f0:sub sp, sp, #0x2200x1023be0f4:sub x9, x29, #0x980x1023be0f8:adrp x8, #0x106f3d0000x1023be0fc:ldr x8, [x8, #0xd70]0x1023be100:ldr x8, [x8]0x1023be104:str x8, [x9, #0x40]0x1023be108:mov w8, #0x12c0x1023be10c:cmp x0, #00x1023be110:str w8, [sp, #0x130]0x1023be114:mov w8, #0x2e0x1023be118:mov w9, #0x4c0x1023be11c:csel w8, w9, w8, eq0x1023be120:stp w8, w2, [sp, #0xb0]0x1023be124:cmp w2, #40x1023be128:mov w8, #0x530x1023be12c:csel w8, w9, w8, eq0x1023be130:str w8, [sp, #0xac]0x1023be134:mov w8, #0x120x1023be138:mov w9, #0x340x1023be13c:csel w8, w9, w8, eq......

配合ida python脚本，去除无用分支：

import sarkimport idcimport sysdef patch_code(addr,code):    for i in range(len(code)):        idc.patch_byte(addr+i,code[i]) #将指定地址的字节修改成nopdef nop(addr):    nop_code=[0x1f,0x20,0x03,0xd5]    patch_code(addr,nop_code) def main():    logfilename="./log.txt"    #定义要处理函数的起始和终止范围    start=0x1023BE0D4    end=0x1023CBB6C    addrs=[]    #将所有执行的汇编地址读取进来    with open(logfilename,"r") as logfile:        lines=logfile.readlines()        for line in lines:            addrs.append(int(line.replace("n","").split(':')[0],16))    #所有执行过的汇编地址修改一下颜色。高亮起来便于查看    for addr in addrs:        line=sark.line.Line(addr)        line.color=0x00ffff     #获取到目标函数内的所有汇编地址    funcLines=sark.lines(start,end)    for line in funcLines:        #如果该行是code则判断颜色是否被我们标注成有效代码。        if line.type=="code":            if line.color!=0x00ffff:                nop(line.ea)  if __name__=="__main__":    main()