网上看到一些前辈对某SDK做过一些分析,自己也来实践操作一下,对自己平时分析的过程做一个简单记录
一.获取样本
样本来源为某waf2.0:
0002_84288D08C9374C3BD0201E3A8581A637A4F10635D6C1AD364FF9AD35A3073D4AAD68B431ACBEB332ABC3AC3CA8CB7A3B8815EA47C900QufkJeD6QRw50f/FZmE56tVVB3+Xf7tsOWNwpGmRtV9c+9XVaEGi91mRse0WDGYDqSKE/Fi4XTybRySzpSqrj1b5OkdVEbBlAX1Y0laawyer+eMW3IR7qcVnEbup+zYaNy0rR4i8OSKMf/DrpghjUfkyybAhFBTgzjK5+dvGugTLWxfHU2gnYdnn79x3D/jz/EJEpBrN3O/FdanEn8S5wb0VbqzQ/iRbmMZxwq6hUJzCy7CvSH5gjDPX+8BpJUwaxVAy2VR5EhvhDFqPvm/YAuY6ZcfATB2Zh5x5kVkDUFWZGWtNp3OfWodBY6oT34iNKl7/DJl0v97g4JYEcUlXkVAUNTIb1+hAhRZb6stIR3DJoIO9LVAVTYBN5QzURu017Ob6/NjHUOwAd38REY5M6VLITharAN30Z61J0cYAp/xio4RBhojNqWl2FwPRnKbr
0002应该是该风控的版本号
我们这次来的目的就是为了把 wtoken 给完全解开
二.开始分析
根据官网的说明文档
if(![[AliTigerTally sharedInstance]initialize:@"****OpKLvM6zliu6KopyHIhmneb_****u4ekci2W8i6F9vrgpEezqAzEzj2ANrVUhvAXMwYzgY_****vc51aEQlRovkRoUhRlVsf4IzO9dZp6nN_****Wz8pk2TDLuMo4pVIQvGaxH3vrsnSQiK****"])
{
NSLog(@"初始化失败");
return;
}
NSString *signBody =@"hello";
NSString *wToken= [[AliTigerTally sharedInstance] vmpSign:[signBody dataUsingEncoding:NSUTF8StringEncoding]];
NSLog(@"wToken== %@",wToken);
1.固定随机数
首先是hook initialize 方法,拿到其中的appkey
然后hook vmpSign,固定入参,想办法把输出结果固定下来
首先拦截发送的网络请求,将返回值固定下来.
然后发现生成的结果还是在变,分析其中的导入函数,hook其中可以产生随机值的地方
在hook arc4random 和 gettimeofday 终于将生成的结果固定唯一
2.分析结构组成
wtoken基本由四部分组成
版本号
0002_
时间戳
84288D08C9
整体的签名(前两位37为随机值,确定签名所使用的方法)
374C3BD0201E3A8581A637A4F10635D6C1AD364FF9AD35A3073D4AAD68B431ACBEB332ABC3AC3CA8CB7A3B8815EA47C900
设备信息
QufkJeD6QRw50f/FZmE56tVVB3+Xf7tsOWNwpGmRtV9c+9XVaEGi91mRse0WDGYDqSKE/Fi4XTybRySzpSqrj1b5OkdVEbBlAX1Y0laawyer+eMW3IR7qcVnEbup+zYaNy0rR4i8OSKMf/DrpghjUfkyybAhFBTgzjK5+dvGugTLWxfHU2gnYdnn79x3D/jz/EJEpBrN3O/FdanEn8S5wb0VbqzQ/iRbmMZxwq6hUJzCy7CvSH5gjDPX+8BpJUwaxVAy2VR5EhvhDFqPvm/YAuY6ZcfATB2Zh5x5kVkDUFWZGWtNp3OfWodBY6oT34iNKl7/DJl0v97g4JYEcUlXkVAUNTIb1+hAhRZb6stIR3DJoIO9LVAVTYBN5QzURu017Ob6/NjHUOwAd38REY5M6VLITharAN30Z61J0cYAp/xio4RBhojNqWl2FwPRnKbr
3.加密过程分析
整个SDK混淆的比较严重,插入了大量花指令来阻止IDA的分析
首先,找到的VMP调用外部函数的调用点
通过x8寄存器跳转到不同的函数里,通过打印x8的流转,然后用Frida来辅助分析.基本可以得到整个加密过程的基本逻辑
其中的加解密就是一些移位异或加减之类的,最后再进行一次AES加密生成的
比如通过字节码的补位来判断采取的加密方式
在这里,可以在lldb中采用手动给w9赋值的方式还原所有的加密方法
p w9 = 0
比如当 w9 为 0 时,采取的偏移跳转第一个加密块 loc_100038188
从图上可以清楚的看出来,这个一个比特位互换的操作 例如 0xAB => 0xBA
还原成C的话就是
new_byte = ((orig_byte << 4) | (orig_byte >> 4)) & 0xff
其他的加密也大同小异,剩下的15种加密方式就不一一列举了.
还有一部分就是对传进来的body进行签名操作
1.首先body 拼接 &14b8_ 和之前采集的设备信息做一次sha256,当然这个sha256不是标准算法
2.然后再生成的结果中取 [0x4:0x18] 位做 hmac 运算
3.拼接 14b8 + d330 之后,根据生成的随机值37做加密运算,还是异或之类的操作
4.生成sign
最后解密出来的数据基本如下
num:[0x00] data:[b'com.xxxxxx.cn']
num:[0x01] data:[b'xxxxxx']
num:[0x02] data:[b'5.1.0']
num:[0x03] data:[b'2.1.5']
num:[0x05] data:[b'apple']
num:[0x06] data:[b'iPhone13,1']
num:[0x0a] data:[b'375x812']
num:[0x0c] data:[b'19A346']
num:[0x0d] data:[b'15.0']
num:[0x12] data:[b'\xe4\xb8\xad\xe5\x9b\xbd\xe7\xa7\xbb\xe5\x8a\xa8']
num:[0x14] data:[b',46002']
num:[0x24] data:[b'0852D236-E454-44DD-A3C2-5797E8DA7979']
num:[0x25] data:[b'none']
num:[0x26] data:[b'57256ED654C6E9FE41DC0D5DBEE2EB18']
num:[0x64] data:[b'|']
num:[0x0b] data:[b'Darwin Kernel Version 21.0.0: Sun Aug 15 20:55:58 PDT 2021; root:xnu-8019.12.5~1/RELEASE_ARM64_T8101']
num:[0x1d] data:[b',fd8d:d307:fcd9:d373:1821:4efe:5d02:b134']
num:[0x1e] data:[b'192.168.2.1']
num:[0x27] data:[b'AC0A2433-93DB-4296-82661-F7D2E047C3a']
num:[0x2e] data:[b'10.42.23.8,fe80::ec8e:52ff:feb4:6ab7']
num:[0x31] data:[b'/private/var/containers/Bundle/Application/C2D127FB-54E5-436E-BD56-468DDEBE8CD8/xxxx.app/xxxx']
num:[0x33] data:[b'403373.19.420688398']
num:[0x34] data:[b'31fbddade56c6ab0277263c3eb55dda3']
num:[0x35] data:[b'1fbabaa42b305297f1c5421a3d89b8c6']
num:[0x39] data:[b'1198000']
num:[0x3b] data:[b'zh-Hans-CN|en-CN']
num:[0x3c] data:[b'ARM64']
num:[0x6d] data:[b'0']
num:[0x6e] data:[b'0']
num:[0x70] data:[b'0']
num:[0x71] data:[b'0']
num:[0x72] data:[b'TMPDIR=/private/var/mobile/Containers/Data/Application/B62336DD-18D6-4A17-9FE1-A38B36B25045/tmp/|']
num:[0xc9] data:[b'42|42']
数据有一部分进行了加密或者脱密处理,使我们不能直接看到原始信息
但是在分析过程中,SDK获取的信息基本为:
越狱文件检测
/Applications/Cydia.app
/Library/MobileSubstrate/MobileSubstrate.dylib
/bin/bash
/usr/sbin/sshd
/etc/apt
/usr/bin/cycript
/usr/bin/gdbhd
dladdr检测列表
x0 = 0x00000001a42cefa0 libsystem_c.dylib`sysctl
x0 = 0x00000001a42dd990 libsystem_c.dylib`fopen
x0 = 0x00000001a42f7c08 libsystem_c.dylib`getenv
x0 = 0x00000001a44ad760 libsystem_kernel.dylib`stat
x0 = 0x00000001a44b9608 libdyld.dylib`_dyld_get_image_name
x0 = 0x00000001a44b9710 libdyld.dylib`dladdr
x0 = 0x00000001a4597598 CoreFoundation`-[NSArray containsObject:]
x0 = 0x00000001a459ceb8 CoreFoundation`+[NSLocale preferredLanguages]
x0 = 0x00000001a45b1a74 CoreFoundation`+[NSLocale currentLocale]
x0 = 0x00000001a45b9600 CoreFoundation`+[NSTimeZone localTimeZone]
x0 = 0x00000001a495b73c SystemConfiguration`CNCopyCurrentNetworkInfo
x0 = 0x00000001a4979a84 Foundation`+[NSBundle mainBundle]
x0 = 0x00000001a497d624 Foundation`+[NSProcessInfo processInfo]
x0 = 0x00000001a497e030 Foundation`-[NSBundle bundleIdentifier]
x0 = 0x00000001a4980f90 Foundation`-[NSString rangeOfString:]
x0 = 0x00000001a498690c Foundation`-[NSFileManager fileExistsAtPath:]
x0 = 0x00000001a4996978 Foundation`-[NSString initWithUTF8String:]
x0 = 0x00000001a49a1db0 Foundation`+[NSDictionary(NSDictionary) dictionaryWithContentsOfFile:]
x0 = 0x00000001a49b69e4 Foundation`-[NSFileManager attributesOfFileSystemForPath:error:]
x0 = 0x00000001a49b6c6c Foundation`-[NSFileManager contentsOfDirectoryAtPath:error:]
x0 = 0x00000001a49b7124 Foundation`-[NSFileManager attributesOfItemAtPath:error:]
x0 = 0x00000001a49ff65c Foundation`-[NSBundle executablePath]
x0 = 0x00000001a79082cc CFNetwork`CFNetworkCopySystemProxySettings
x0 = 0x00000001a83d8194 UIKitCore`-[UIDevice name]
x0 = 0x00000001a83d81f0 UIKitCore`-[UIDevice model]
x0 = 0x00000001a83d83b0 UIKitCore`-[UIDevice systemVersion]
x0 = 0x00000001a83d8468 UIKitCore`-[UIDevice identifierForVendor]
x0 = 0x00000001a83d8cac UIKitCore`-[UIDevice batteryState]
x0 = 0x00000001a83d8cb8 UIKitCore`-[UIDevice batteryLevel]
x0 = 0x00000001a83e4198 UIKitCore`-[UIScreen brightness]
x0 = 0x00000001a8eaab3c CoreTelephony`-[CTCarrier carrierName]
x0 = 0x00000001a8eaab4c CoreTelephony`-[CTCarrier mobileCountryCode]
x0 = 0x00000001a8eaab5c CoreTelephony`-[CTCarrier mobileNetworkCode]
x0 = 0x00000001a8eaab6c CoreTelephony`-[CTCarrier isoCountryCode]
x0 = 0x00000001a8eade3c CoreTelephony`-[CTTelephonyNetworkInfo currentRadioAccessTechnology]
x0 = 0x00000001a8eae2c4 CoreTelephony`-[CTTelephonyNetworkInfo subscriberCellularProvider]
x0 = 0x00000001bd6b5cc4 AdSupport`-[ASIdentifierManager isAdvertisingTrackingEnabled]
x0 = 0x00000001bd6b5d28 AdSupport`-[ASIdentifierManager advertisingIdentifier]
三.总结
时间过去的有点久,很多入口函数忘记在哪里了,从技术角度来讲确实逆向的难度比较大,主要是掺杂了大量的自定义算法,比如在拼接设备信息之后,按照字节的补位数一共有16种加密算法,还有魔改的sha256,hash算法,大部分时间都花在还原这一部分算法上面了.整体难度很大
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发表于 2022-12-29 22:59
