快手,快影 iOS App反调试 - 哈喽比特

1998次阅读 | 发布于3年以前

作者 | 倒影cc 来源 | 掘金，点击阅读原文查看作者更多文章

快手，快影的App保护用的是同一套代码，反调试也很容易，下面请看过程。

1.快手App去反调试

直接frida砸壳，然后创建MonkeyDev工程，并在antiAntiDebug.m文件的相关函数下断点，然后运行。

App运行起来后，将在my_dlsym函数断下来，然后bt打印调用栈：

然后在栈1地址处下断，即: b 0x00000001054c3430，按C运行。

在0x00000001054c3430 处断下来之后，修改返回值 x0 = 0 ,即：

register write $x0  0

在汇编55行：

nop该行指令，然后运行即可，命令如下：

memory write -s 4 0x1028c09f4  0xd503201f

2.快影App去反调试

砸壳快影，然后创建MonkeyDev工程，运行，闪退。看下日志，打印如下：

[AntiAntiDebug] - dlsym get ptrace symbol
[AntiAntiDebug] - ptrace request is PT_DENY_ATTACH

在antiAntiDebug的my_ptrace和my_dlsym处下断点。去反调试

函数1：0x000000010265c920，

汇编55行: nop掉改行汇编指令即可正常运行，命令如下：

memory write -s 4  0x102e089f4  0xd503201f

2.1 快影App sign的计算逻辑

首先通过IDA静态分析，我们得到如下关键方法：

id __cdecl +[KSMWPassportSecurityTools hmac:withKeyData:](KSMWPassportSecurityTools_meta *self, SEL a2, id a3, id a4)
{
  id v4; // x19
  id v5; // x20
  __int64 v6; // x21
  __int64 v7; // x1
  __int64 v8; // x22
  void *v9; // x0
  const char *v10; // x20
  void *v11; // x19
  void *v12; // x21
  void *v13; // x19
  size_t v14; // x0
  char v16; // [xsp+8h] [xbp-48h]
  v4 = a4;
  v5 = a3;
  v6 = objc_retain(a3, a2);
  v8 = objc_retain(v4, v7);
  v9 = (void *)objc_retainAutorelease(v5);
  v10 = (const char *)objc_msgSend(v9, "cStringUsingEncoding:", 4LL);
  objc_release(v6);
  v11 = (void *)objc_retainAutorelease(v4);
  v12 = objc_msgSend(v11, "bytes");
  v13 = objc_msgSend(v11, "length");
  objc_release(v8);
  v14 = strlen(v10);
  CCHmac(2LL, v12, v13, v10, v14, &v16);   // 2 = kCCHmacAlgSHA256
  return (id)objc_msgSend(&OBJC_CLASS___NSData, "dataWithBytes:length:", &v16, 32LL);
}

其完整的sign计算逻辑为：

[KSMWPassportSecurityTools createSignWithStringNonce:ssecurity:longValue: value]
    |
    +[KSMWPassportSecurityTools hmac:withKeyData:] = resultData
        |
        CCHmac(2LL, 0, 0, x3, 101, resultBuf); 
    |
    data = bswap32(value)
    |
    [data appendData: resultData]
    |
    [KSMWPassportSecurityTools base64Encode:]

于是对[KSMWPassportSecurityTools createSignWithStringNonce:ssecurity:longValue: value]方法下断，然后点击获取验证码，其调用栈如下：

thread #1, queue = 'com.apple.main-thread', stop reason = breakpoint 18.1
frame #0: 0x0000000101856fb0 KwaiYDelux`+[KSMWPassportSecurityTools createSignWithStringNonce:ssecurity:longValue:]
frame #1: 0x0000000101856c30 KwaiYDelux`+[KSMWPassportSecurityTools signOnURLPath:method:requestParams:] + 364
frame #2: 0x0000000101855910 KwaiYDelux`-[KSMWNetworkOperation url:method:parameters:cookies:completionHandler:] + 212
frame #3: 0x0000000101863a14 KwaiYDelux`-[KWPassportAPI POST:bodyParams:completionHandler:] + 280
frame #4: 0x00000001018607f8 KwaiYDelux`-[KWPassportAPI requestSMSCode:countryCode:type:completion:] + 412
frame #5: 0x000000010185f25c KwaiYDelux`-[KWPassport requestSMSCode:countryCode:type:completion:] + 132
frame #6: 0x00000001026799dc KwaiYDelux`-[KWAccountChannelService_Imp sendSMSWithRequest:handler:] + 264
frame #7: 0x000000018deea800 CoreFoundation`__invoking___ + 144
frame #8: 0x000000018ddcc3c0 CoreFoundation`-[NSInvocation invoke] + 292
frame #9: 0x000000010259659c KwaiYDelux`___lldb_unnamed_symbol58737?KwaiYDelux + 1180
frame #10: 0x000000010817e7fc Flutter`__45-[FlutterMethodChannel setMethodCallHandler:]_block_invoke + 116
frame #11: 0x000000010811d6d0 Flutter`flutter::PlatformViewIOS::HandlePlatformMessage(fml::RefPtr<flutter::PlatformMessage>) + 680
frame #12: 0x0000000108170048 Flutter`std::__1::__function::__func<flutter::Shell::OnEngineHandlePlatformMessage(fml::RefPtr<flutter::PlatformMessage>)::$_32, std::__1::allocator<flutter::Shell::OnEngineHandlePlatformMessage(fml::RefPtr<flutter::PlatformMessage>)::$_32>, void ()>::operator()() + 80
frame #13: 0x000000010812a988 Flutter`fml::MessageLoopImpl::FlushTasks(fml::FlushType) + 96
frame #14: 0x000000010812ef0c Flutter`fml::MessageLoopDarwin::OnTimerFire(__CFRunLoopTimer*, fml::MessageLoopDarwin*) + 32
frame #15: 0x000000018de75554 CoreFoundation`__CFRUNLOOP_IS_CALLING_OUT_TO_A_TIMER_CALLBACK_FUNCTION__ + 28
frame #16: 0x000000018de75284 CoreFoundation`__CFRunLoopDoTimer + 864
frame #17: 0x000000018de74ab8 CoreFoundation`__CFRunLoopDoTimers + 248
frame #18: 0x000000018de6fa08 CoreFoundation`__CFRunLoopRun + 1844
frame #19: 0x000000018de6efb4 CoreFoundation`CFRunLoopRunSpecific + 436
frame #20: 0x000000019007079c GraphicsServices`GSEventRunModal + 104
frame #21: 0x00000001ba6d0c38 UIKitCore`UIApplicationMain + 212
frame #22: 0x0000000100e0c028 KwaiYDelux`___lldb_unnamed_symbol1343?KwaiYDelux + 100
frame #23: 0x000000018d9328e0 libdyld.dylib`start + 4

调用+[KSMWPassportSecurityTools hmac:withKeyData:]

其中

hmac=POST&/pass/ky/sms/code&countryCode=+86&phone=ZTSP__R2oN18L5Ilx8weM__ZTSP&type=395&8951850021377611294
data = 空

汇编50行，调用 CCHmac(2LL, 0, 0, x3, 101, resultBuf); // 2 = kCCHmacAlgSHA256， CC_SHA256_DIGEST_LENGTH = 32，即加密返回长度=32

(lldb) x/50xg $x3,  长度=101, 即=POST&/pass/ky/sms/code&countryCode=+86&phone=ZTSP__R2oN18L5Ilx8weM__ZTSP&type=395&8951850021377611294

内存数据如下：

0x2823ace91: 0x61702f2654534f50 0x6d732f796b2f7373      
0x2823acea1: 0x632665646f632f73 0x6f437972746e756f      
0x2823aceb1: 0x702636382b3d6564 0x53545a3d656e6f68      
0x2823acec1: 0x314e6f32525f5f50 0x7738786c49354c38
0x2823aced1: 0x5053545a5f5f4d65 0x39333d6570797426
0x2823acee1: 0x3538313539382635 0x3637373331323030
0x2823acef1: 0x0000003439323131 0x0000000000000000
0x2823acf01: 0x0000000000000000 0x0000000000000000

(lldb) x/50xg $x5 -> 加密结果

0x16f1290c8: 0x35da8aa020e5bd2f 0xf6fc50b2b2c85841
0x16f1290d8: 0x2e00c9df95a02ada 0x17325b620c1cd33f

将data<7c3b5c2a 5ec9161e> append 加密结果，得到：

<7c3b5c2a 5ec9161e 2fbde520 a08ada35 4158c8b2 b250fcf6 da2aa095 dfc9002e 3fd31c0c 625b3217>

然后调用 [KSMWPassportSecurityTools base64Encode:], 传入上面的data。得到：

fDtcKl7JFh4vveUgoIraNUFYyLKyUPz22iqgld/JAC4/0xwMYlsyFw==

这就是最终的sign，可以通过抓包进行对比。

由于快影App 大部分业务界面都是flutter开发的，目前还没有能力进行逆向，flutter页面的接口请求也没有走Native，没办法进行抓包。 wireshark只能抓到https加密包，它的本质就是把经过网卡的数据包复制一份，而不是像charles在手机系统上起一个代理服务器，对App的网络请求进行代理请求。

据网上说，可以通过代理(fan qiang)工具进行代理，然后再使用charles进行抓包。