iOS逆向之Frida Hook绕过人脸识别

摘要

*本文不涉及任何漏洞，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。

0×00前言

解决问题的手段有很多种，也许存在优劣之分，这次选择了其中一种不那么好玩的方法——frida hook。

人脸识别校验状态存储在服务端，因此即使通过该种方法绕过客户端人脸识别，由于并未获得合法session，所以并无任何实际危害，仅做为IOS Hook学习思路。

0×01准备

越狱IOS(12.4.4)

Frida

lxhToolHTTPDecrypt

app一个

登录时存在人脸识别：

0×02 脱壳&安装

CrackerXI+脱壳，ReProvision签名一条龙，有疑问的可以参考上一篇文章。一毛一样的app。

0×03 寻找关键函数

CrackerXI+脱壳后，二进制文件拉出来拖到ida中分析找到关键函数：

XXXXBaseViewController loginSuccessIsNeedBind:WithInfo: 

void __cdecl -[XXXXAPPBaseViewController loginSuccessIsNeedBind:WithInfo:](XXXXAPPBaseViewController *self, SEL a2, bool a3, id a4)
{ BOOL v4; // w22 XXXXAPPBaseViewController *v5; // x21 __int64 v6; // x19 void *v7; // x0 void *v8; // x0 void *v9; // x23 void *v10; // x0 void *v11; // x20 XXXXAPPLoginHelper *v12; // x0 void *v13; // x23 __int64 v14; // x1 __int64 v15; // x1 __int64 v16; // x0 struct objc_object *v17; // x0 void *v18; // x0 void *v19; // x22 void *v20; // x0 void *v21; // x23 int v22; // w24 void *v23; // x0 void *v24; // x0 __int64 v25; // x22 void *v26; // x0 __int64 v27; // x23 const char *v28; // x1 void **v29; // [xsp+0h] [xbp-70h] __int64 v30; // [xsp+8h] [xbp-68h] __int64 (__fastcall *v31)(); // [xsp+10h] [xbp-60h] void *v32; // [xsp+18h] [xbp-58h] XXXXAPPBaseViewController *v33; // [xsp+20h] [xbp-50h] __int64 v34; // [xsp+28h] [xbp-48h] __int64 v35; // [xsp+30h] [xbp-40h] bool v36; // [xsp+38h] [xbp-38h] v4 = a3;//赋值v4 v5 = self;
  v6 = objc_retain(a4, a2);
  v7 = objc_msgSend(&OBJC_CLASS___UIApplication, "sharedApplication");
  v8 = (void *)objc_retainAutoreleasedReturnValue(v7);
  v9 = v8;
  v10 = objc_msgSend(v8, "delegate");
  v11 = (void *)objc_retainAutoreleasedReturnValue(v10);
  objc_release(v9); if ( (unsigned int)-[XXXXAPPBaseViewController needInputIDCardInfomation:](v5, "needInputIDCardInfomation:", v6) )
  {
    +[PCUtil setObject:forKey:](&OBJC_CLASS___PCUtil, "setObject:forKey:", CFSTR("1"), CFSTR("maybeNeedBackLoginGuide"));
    v12 = +[XXXXAPPLoginHelper sharedInstance](&OBJC_CLASS___XXXXAPPLoginHelper, "sharedInstance");
    v13 = (void *)objc_retainAutoreleasedReturnValue(v12);
    v29 = _NSConcreteStackBlock;
    v30 = 3254779904LL;
    v31 = sub_1000B05E4;
    v32 = &unk_10263F2D8;
    v33 = v5;
    v36 = v4;
    v34 = objc_retain(v11, v14);
    v35 = objc_retain(v6, v15);
    objc_msgSend(
      v13, "setCompleteGuideBlock:",
      &v29,
      _NSConcreteStackBlock, 3254779904LL,
      sub_1000B05E4,
      &unk_10263F2D8,
      v5);
    objc_release(v13);
    objc_release(v35);
    v16 = v34;
LABEL_9:
    objc_release(v16); goto LABEL_10;
  } if ( v4 ) //判断v4(bool)值,确定是否进入人脸识别 {
    v17 = +[PNCMBankGlobal sharedData](&OBJC_CLASS___PNCMBankGlobal, "sharedData");
    v18 = (void *)objc_retainAutoreleasedReturnValue(v17);
    v19 = v18;
    v20 = objc_msgSend(v18, "bindType");
    v21 = (void *)objc_retainAutoreleasedReturnValue(v20);
    v22 = (unsigned __int64)objc_msgSend(v21, "isEqualToString:", CFSTR("FACE"));
    objc_release(v21);
    objc_release(v19);
    v23 = objc_msgSend(v11, "rootVC");
    v24 = (void *)objc_retainAutoreleasedReturnValue(v23);
    v25 = (__int64)v24;
    v26 = objc_msgSend(v24, "navigationController");
    v27 = objc_retainAutoreleasedReturnValue(v26); if ( v22 )
      v28 = "goToFaceCheckBindVC:info:"; else v28 = "goSmsOrUKBindInfoVC:info:";
    objc_msgSend(v5, v28, v27, v6);
    objc_release(v27);
    v16 = v25; goto LABEL_9;
  }
  -[XXXXAPPBaseViewController AfterBindSuccess:isNeedBind:](v5, "AfterBindSuccess:isNeedBind:", v6, 0LL);
LABEL_10:
  objc_release(v11);
  objc_release(v6);
}

分析代码发现： 

void __cdecl -[XXXXAPPBaseViewController loginSuccessIsNeedBind:WithInfo:](XXXXAPPBaseViewController *self, SEL a2, bool a3, id a4)
v4 = a3;
//...
if ( v4 ) 
{
//...
//人脸识别函数
//...
}

其中a3是参数传入，只要我们hook -[XXXXAPPBaseViewController loginSuccessIsNeedBind:WithInfo:]使其传入bool参数a3为永假，即可不进入人脸识别判断。

手机中启动frida-server（手机中的frida版本须和PC中的版本一致）:

PC上启动lxhToolHTTPDecrypt（ps：不使用该工具也可以，使用frida脚本能够直接查找类名函数等，但这个工具图形化界面比较直观，也有一些其他功能）

访问http://127.0.0.1:8088选择Identifier

在Hook里选择类名

进入人脸识别时hook到该函数：

0×04 HOOK

编写hook脚本hooking.js： 

var search_class = ['XXXXXXBaseViewController']; var search_method = ['loginSuccessIsNeedBind:WithInfo:']; function search_methods(className) { var methods_found = []; var methods = ObjC.classes[className].$ownMethods; if (Array.isArray(search_method) && search_method.length) { //search_method not empty for (var j = 0; j < search_method.length; j++) { if (methods.join(' ').toLowerCase().includes(search_method[j].toLowerCase())) { for (var i = 0; i < methods.length; i++){ if (methods[i].toLowerCase().includes(search_method[j].toLowerCase())) {
methods_found.push(methods[i]);
}
}
}
}
} else { var methods = ObjC.classes[className].$ownMethods; for (var i = 0; i < methods.length; i++){
methods_found.push(methods[i]);
}
} return methods_found;
} function search_classes(){ var classes_found = []; for (var className in ObjC.classes) { if (Array.isArray(search_class) && search_class.length) { for (var i = 0; i < search_class.length; i++) { if (className.toLowerCase().includes(search_class[i].toLowerCase())) {
classes_found.push(className);
}
}
}
} return classes_found;
} function print_arguments(args) { var n = 100; var last_arg = ''; for (var i = 2; i < n; ++i) { var arg = (new ObjC.Object(args[i])).toString(); if (arg == 'nil' || arg == last_arg) { break;
}
last_arg = arg; console.log('\t[-] arg' + i + ': ' + (new ObjC.Object(args[i])).toString());
}
} if (ObjC.available)
{ console.log('\n[*] Starting Hooking'); var classes_found = search_classes(); for (var i = 0; i < classes_found.length; ++i) { var methods_found = 0;
methods_found = search_methods(classes_found[i]); if (Object.keys(methods_found).length){ console.log(classes_found[i]);
} for (var j = 0; j < methods_found.length; ++j) { var _className = "" + classes_found[i]; var _methodName = "" + methods_found[j]; var hooking = ObjC.classes[_className][_methodName]; console.log('   ' + methods_found[j]);
Interceptor.attach(hooking.implementation, {
onEnter: function (args) { this._className = ObjC.Object(args[0]).toString(); this._methodName = ObjC.selectorAsString(args[1]); console.log('Detected call to:'); console.log('   ' + this._className + ' --> ' + this._methodName); //print_arguments(args); },
onLeave: function(returnValues) {
}
});
}
} console.log('\n[*] Starting Intercepting');
} else { console.log('Objective-C Runtime is not available!');
}

执行

frida -l hooking.js -U “appname”

从图上可见hook成功

编写onEnter Hook传入参数修改成0×0： 

onEnter: function (args) { this._className = ObjC.Object(args[0]).toString(); this._methodName = ObjC.selectorAsString(args[1]); console.log('Detected call to:'); console.log('   ' + this._className + ' --> ' + this._methodName); console.log('[-]原始值：'+ args[2]);
args[2]=ptr("0x0"); console.log('[+]修改值：'+ args[2]); //print_arguments(args); },

运行Hook:

进入app输入密码登录，已不存在人脸识别。

但登录后由于人脸识别验证在服务端，客户端中并无数据，因此无实际危害。

注：此种方式绕不涉及任何实际漏洞，仅作为IOS测试学习使用。

0×05 后记

参考工具地址：https://github.com/trelis24/frida-ios

高清原始文件：

链接: https://pan.baidu.com/s/1kCCW5R_rsCX5ZtPuy_hZPA 提取码: d2pr

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