*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。
0x00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。
0x01准备
越狱IOS(12.4.4)
app一个
登录时存在人脸识别：
0x02 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。
0x03 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：
0x04 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0x0：
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
*本文作者：LDrakura，转载请注明来自FreeBuf.COM
来源：freebuf.com 2020-06-30 08:00:40 by: LDrakura
© 版权声明
文章版权归作者所有，未经允许请勿转载。
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