2019SCTF 部分WP

姚小宝

题目可在xctf社区获取

strange apk
一道安卓题，直接APKIDE打开。

通过阅读代码发现

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public class c   extends Application {   private String apkFileName;   private String libPath;   protected AssetManager mAssetManager;   protected Resources mResources;   protected Resources.Theme mTheme;   private String odexPath;       private void _(byte[] paramArrayOfByte)     throws IOException   {     paramArrayOfByte = _0_(paramArrayOfByte);     Object localObject = new File(this.apkFileName);     try     {       localObject = new FileOutputStream((File)localObject);       ((FileOutputStream)localObject).write(paramArrayOfByte);       ((FileOutputStream)localObject).close();       return;     }     catch (IOException paramArrayOfByte)     {       throw new RuntimeException(paramArrayOfByte);     }   }       private byte[] _0_(byte[] paramArrayOfByte)   {     int i = 0;     while (i < paramArrayOfByte.length)     {       paramArrayOfByte[i] = ((byte)("syclover".charAt(i % "syclover".length()) ^ paramArrayOfByte[i]));       i += 1;     }     return paramArrayOfByte;   }       public byte[] __(String paramString)     throws IOException   {     paramString = getResources().getAssets().open(paramString);     byte[] arrayOfByte = new byte[paramString.available()];     paramString.read(arrayOfByte);     return arrayOfByte;   }       protected void attachBaseContext(Context paramContext)   {     super.attachBaseContext(paramContext);     try     {       paramContext = getDir("sctf_odex", 0);       localObject = getDir("sctf_lib", 0);       this.odexPath = paramContext.getAbsolutePath();       this.libPath = ((File)localObject).getAbsolutePath();       localObject = new StringBuilder();       ((StringBuilder)localObject).append(paramContext.getAbsolutePath());       ((StringBuilder)localObject).append("/sctf.apk");       this.apkFileName = ((StringBuilder)localObject).toString();       paramContext = new File(this.apkFileName);       localObject = new StringBuilder();       ((StringBuilder)localObject).append("apk size:");       ((StringBuilder)localObject).append(paramContext.length());       Log.i("demo", ((StringBuilder)localObject).toString());       if (!paramContext.exists())       {         paramContext.createNewFile();         _(__("data"));       }       paramContext = s.invokeStaticMethod("android.app.ActivityThread", "currentActivityThread", new Class[0], new Object[0]);       localObject = getPackageName();       if (Build.VERSION.SDK_INT < 19) {         paramContext = (WeakReference)((HashMap)s.getFieldOjbect("android.app.ActivityThread", paramContext, "mPackages")).get(localObject);       } else {         paramContext = (WeakReference)((ArrayMap)s.getFieldOjbect("android.app.ActivityThread", paramContext, "mPackages")).get(localObject);       }       localObject = new DexClassLoader(this.apkFileName, this.odexPath, this.libPath, (ClassLoader)s.getFieldOjbect("android.app.LoadedApk", paramContext.get(), "mClassLoader"));       s.setFieldOjbect("android.app.LoadedApk", "mClassLoader", paramContext.get(), localObject);       paramContext = new StringBuilder();       paramContext.append("classloader:");       paramContext.append(localObject);       Log.i("demo", paramContext.toString());       return;     }     catch (Exception paramContext)     {       Object localObject = new StringBuilder();       ((StringBuilder)localObject).append("error:");       ((StringBuilder)localObject).append(Log.getStackTraceString(paramContext));       Log.i("demo", ((StringBuilder)localObject).toString());       paramContext.printStackTrace();     }   }

该APK中隐藏着一个data文件，直接修改后缀为zip打开，data解密之后就是一个APK。
上脚本解密

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i = "syclover"   f = open("data", "rb") q = open("datas","wb")   couts = 0 c = f.read(1) qq = 0 while (1):     uq = ord(c)^ord(i[qq%8])     if (uq<=15):         q.write(("0x0"+hex(uq)[2:])[2:])     else:         q.write((hex(uq))[2:])     couts += 1     qq += 1     if (couts%2==0 and couts%16!=0):         q.write(' ')       if (couts%16==0):         q.write('\n')     c = f.read(1)     if c==None:         break       q.close() f.close()

可以把datas里边的数据用winhex以二进制方式存入一个新文件，原来手动存的时候一直显示未预料到文件尾，还以为要手动修复zip，原来是自己的问题，可能是文件尾部多了一些数据，导致CRC校验出错。

最终得到一个新APK。
阅读代码。

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protected void onCreate(Bundle paramBundle)   {     super.onCreate(paramBundle);     setContentView(2131296285);     paramBundle = (Button)findViewById(2131165218);     findViewById(2131165322);     paramBundle.setOnClickListener(new View.OnClickListener()     {       public void onClick(View paramAnonymousView)       {         paramAnonymousView = "";         Object localObject1 = "";         int i = 0;         String str = this.val$ed.getText().toString();         if (str.length() == 30)         {           while (i < 12)           {             localObject2 = new StringBuilder();             ((StringBuilder)localObject2).append(paramAnonymousView);             ((StringBuilder)localObject2).append(str.charAt(i));             paramAnonymousView = ((StringBuilder)localObject2).toString();             i += 1;           }           Object localObject2 = f.sctf(paramAnonymousView);           paramAnonymousView = (View)localObject1;           while (i < 30)           {             localObject1 = new StringBuilder();             ((StringBuilder)localObject1).append(paramAnonymousView);             ((StringBuilder)localObject1).append(str.charAt(i));             paramAnonymousView = ((StringBuilder)localObject1).toString();             i += 1;           }           if (((String)localObject2).equals("c2N0ZntXM2xjMG1l"))           {             localObject1 = new Intent();             ((Intent)localObject1).putExtra("data_return", paramAnonymousView);             s.this.setResult(-1, (Intent)localObject1);             s.this.finish();             return;           }           Toast.makeText(s.this.getApplicationContext(), "something wrong", 1).show();           return;         }         Toast.makeText(s.this.getApplicationContext(), "something wrong", 1).show();       }     });   }

c2N0ZntXM2xjMG1l base64解密得到前半flag sctf{W3lc0me

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protected void onActivityResult(int paramInt1, int paramInt2, Intent paramIntent)  {    TextView localTextView = (TextView)findViewById(2131165323);    Button localButton = (Button)findViewById(2131165219);    if (paramInt1 != 1) {      return;    }    if (paramInt2 == -1)    {      Object localObject1 = "";      try      {        Object localObject2 = MessageDigest.getInstance("MD5");        ((MessageDigest)localObject2).update("syclover".getBytes());        localObject2 = new BigInteger(1, ((MessageDigest)localObject2).digest()).toString(16);        localObject1 = localObject2;      }      catch (Exception localException)      {        localException.printStackTrace();      }      if (f.encode(paramIntent.getStringExtra("data_return"), (String)localObject1).equals("~8t808_8A8n848r808i8d8-8w808r8l8d8}8"))      {        localTextView.setVisibility(0);        localButton.setVisibility(4);      }      else      {        Toast.makeText(getApplicationContext(), "one more step", 1).show();      }    }}

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public static String encode(String paramString1, String paramString2) {   int j = paramString1.length();   int k = paramString2.length();   StringBuilder localStringBuilder = new StringBuilder();   int i = 0;   while (i < j)   {     localStringBuilder.append(paramString1.charAt(i));     localStringBuilder.append(paramString2.charAt(i / k));     i += 1;   }   return localStringBuilder.toString(); }

~8t808_8A8n848r808i8d8-8w808r8l8d8}8  取奇数得到后半flag。
最终  sctf{W3lc0me~t0_An4r0id-w0rld}


creakme

IDA阅读代码

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int sub_402540() {   HMODULE v0; // eax   int v1; // eax   _DWORD *v2; // eax   unsigned int ser_len; // edx   _DWORD *string; // ecx   unsigned int string_len; // ebx   char *ascc; // edi   unsigned int v7; // esi   unsigned int v8; // esi   bool v9; // cf   unsigned __int8 v10; // al   unsigned __int8 v11; // al   unsigned __int8 v12; // al   signed int v13; // esi   _BYTE *v14; // ecx   _BYTE *v15; // ecx   const char *v16; // edx   int v17; // eax   void *Memory; // [esp+10h] [ebp-70h]   int v20; // [esp+20h] [ebp-60h]   unsigned int v21; // [esp+24h] [ebp-5Ch]   void *Dst; // [esp+28h] [ebp-58h]   int v23; // [esp+38h] [ebp-48h]   unsigned int v24; // [esp+3Ch] [ebp-44h]   char Src; // [esp+40h] [ebp-40h]   int v26; // [esp+7Ch] [ebp-4h]     v0 = GetModuleHandleW(0);   sub_402320(v0);   sub_4024A0();   v1 = sub_402870(std::cout, "welcome to 2019 sctf");   std::basic_ostream<char,std::char_traits<char>>::operator<<(v1, sub_402AC0);   sub_402870(std::cout, "please input your ticket:");   sub_402AF0(std::cin, &Src);   v23 = 0;   v24 = 15;   LOBYTE(Dst) = 0;   sub_401D30(&Dst, &Src, strlen(&Src));   v26 = 0;   v2 = aes(&Memory, (int)&Dst);   ser_len = strlen(aPvfqyc4ttc2uxr);   string = v2;   if ( v2[5] >= 16u )     string = (_DWORD *)*v2;   string_len = v2[4];   ascc = aPvfqyc4ttc2uxr;   v7 = v2[4];   if ( ser_len < string_len )     v7 = ser_len;   v9 = v7 < 4;                                  // len - 4   v8 = v7 - 4;   if ( v9 )   { LABEL_8:     if ( v8 == -4 )       goto LABEL_17;   }   else   {     while ( *string == *(_DWORD *)ascc )     {       ++string;                                 // +=4       ascc += 4;       v9 = v8 < 4;       v8 -= 4;       if ( v9 )         goto LABEL_8;     }   }   v9 = *(_BYTE *)string < (unsigned __int8)*ascc;   if ( *(_BYTE *)string != *ascc     || v8 != -3     && ((v10 = *((_BYTE *)string + 1), v9 = v10 < (unsigned __int8)ascc[1], v10 != ascc[1])      || v8 != -2      && ((v11 = *((_BYTE *)string + 2), v9 = v11 < (unsigned __int8)ascc[2], v11 != ascc[2])       || v8 != -1 && (v12 = *((_BYTE *)string + 3), v9 = v12 < (unsigned __int8)ascc[3], v12 != ascc[3]))) )   {     v13 = -v9 | 1;     goto LABEL_18;   } LABEL_17:   v13 = 0; LABEL_18:   if ( !v13 )                                   // v13要为0   {     if ( ser_len <= string_len )       v13 = ser_len < string_len;     else       v13 = -1;   }   if ( v21 >= 0x10 )   {     v14 = Memory;     if ( v21 + 1 >= 0x1000 )     {       v14 = (_BYTE *)*((_DWORD *)Memory - 1);       if ( (unsigned int)((_BYTE *)Memory - v14 - 4) > 0x1F )         invalid_parameter_noinfo_noreturn(v14, v21 + 36);     }     frees(v14);   }   v26 = -1;   v20 = 0;   v21 = 15;   LOBYTE(Memory) = 0;   if ( v24 >= 0x10 )   {     v15 = Dst;     if ( v24 + 1 >= 0x1000 )     {       v15 = (_BYTE *)*((_DWORD *)Dst - 1);       if ( (unsigned int)((_BYTE *)Dst - v15 - 4) > 0x1F )         invalid_parameter_noinfo_noreturn(v15, v24 + 36);     }     frees(v15);   }   v16 = "Have fun!";   if ( v13 )     v16 = "A forged ticket!!";   v17 = sub_402870(std::cout, v16);   std::basic_ostream<char,std::char_traits<char>>::operator<<(v17, sub_402AC0);   system("pause");   return 0; }

查看sub_402320函数的代码发现

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void __thiscall sub_402320(_DWORD *this) {   int v1; // eax   __int16 v2; // bx   const char *v3; // esi   signed int i; // edi   int v5; // eax     v1 = this[15];   v2 = *(_WORD *)((char *)this + v1 + 6);   v3 = (char *)this + v1 + 248;   for ( i = 0; i < v2; ++i )                    // 判断区段   {     v5 = strcmp(v3, ".SCTF");     if ( v5 )       v5 = -(v5 < 0) | 1;     if ( !v5 )     {       DebugBreak();       return;     }     v3 += 40;   } }

读取区段，判断区段是否是.SCTF区段。
如果是，就会跳到loc_4023EF并在里边调用函数解密区段。

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.text:004023EF loc_4023EF:                            ; DATA XREF: .rdata:stru_407B58↓o .text:004023EF                 mov     esp, [ebp+ms_exc.old_esp] .text:004023F2                 lea     eax, [ebp+pbDebuggerPresent] .text:004023F5                 push    eax            ; pbDebuggerPresent .text:004023F6                 call    ds:GetCurrentProcess .text:004023FC                 push    eax            ; hProcess .text:004023FD                 call    ds:CheckRemoteDebuggerPresent .text:00402403                 call    ds:IsDebuggerPresent .text:00402409                 test    eax, eax .text:0040240B                 jnz     short loc_4023B9 .text:0040240D                 cmp     [ebp+pbDebuggerPresent], eax .text:00402410                 jnz     short loc_4023B9 .text:00402412                 mov     eax, [ebp+var_24] .text:00402415                 mov     edx, [eax+10h] .text:00402418                 mov     ecx, [eax+0Ch] .text:0040241B                 add     ecx, [ebp+var_28] .text:0040241E                 mov     esi, [ebp+var_2C] .text:00402421                 lea     edi, [esi+1] .text:00402424 .text:00402424 loc_402424:                            ; CODE XREF: sub_402320+109↓j .text:00402424                 mov     al, [esi]      ; sycloversyclover .text:00402426                 inc     esi .text:00402427                 test    al, al .text:00402429                 jnz     short loc_402424 ; sycloversyclover .text:0040242B                 sub     esi, edi .text:0040242D                 push    esi .text:0040242E                 push    ecx .text:0040242F                 call    sub_402450 .text:00402434                 add     esp, 8 .text:00402437                 jmp     short loc_4023B9 .text:00402439 ; --------------------------------------------------------------------------- .text:00402439 .text:00402439 loc_402439:                            ; CODE XREF: sub_402320+8A↑j .text:00402439                 add     esi, 28h .text:0040243C                 inc     edi .text:0040243D                 jmp     loc_402372 .text:0040243D sub_402320      endp

在sub_4024A0函数中，会进入.SCTF区段。
主要是解密>pvfqYc,4tTc2UxRmlJ,sB{Fh4Ck2:CFOb4ErhtIcoLo
解密成nKnbHsgqD3aNEB91jB3gEzAr+IklQwT1bSs3+bXpeuo=

sub_4020D0函数其实就是AES加密。

CBC模式，密码为sycloversyclover，偏移量为sctfsctfsctfsctf。

最终得到




Bybare

一道游戏题，总共有三关。
第一关，

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.text:00005593B1D94798 main:                                  ; DATA XREF: start+1D↑o .text:00005593B1D94798 ; __unwind { .text:00005593B1D94798                 push    rbp .text:00005593B1D94799                 mov     rbp, rsp .text:00005593B1D9479C                 sub     rsp, 160h .text:00005593B1D947A3                 mov     rax, fs:28h .text:00005593B1D947AC                 mov     [rbp-8], rax .text:00005593B1D947B0                 xor     eax, eax .text:00005593B1D947B2                 mov     dword ptr [rbp-150h], 0 .text:00005593B1D947BC                 mov     qword ptr [rbp-110h], 0 .text:00005593B1D947C7                 mov     qword ptr [rbp-108h], 0 .text:00005593B1D947D2                 mov     qword ptr [rbp-100h], 0 .text:00005593B1D947DD                 mov     byte ptr [rbp-0F8h], 0 .text:00005593B1D947E4                 mov     qword ptr [rbp-0F0h], 0 .text:00005593B1D947EF                 mov     qword ptr [rbp-0E8h], 0 .text:00005593B1D947FA                 mov     qword ptr [rbp-0E0h], 0 .text:00005593B1D94805                 mov     byte ptr [rbp-0D8h], 0 .text:00005593B1D9480C                 mov     qword ptr [rbp-0D0h], 0 .text:00005593B1D94817                 mov     qword ptr [rbp-0C8h], 0 .text:00005593B1D94822                 mov     qword ptr [rbp-0C0h], 0 .text:00005593B1D9482D                 mov     qword ptr [rbp-0B8h], 0 .text:00005593B1D94838                 mov     qword ptr [rbp-0B0h], 0 .text:00005593B1D94843                 mov     qword ptr [rbp-0A8h], 0 .text:00005593B1D9484E                 mov     word ptr [rbp-0A0h], 0 .text:00005593B1D94857                 mov     rax, '********' .text:00005593B1D94861                 mov     rdx, '*.******' .text:00005593B1D9486B                 mov     [rbp-90h], rax .text:00005593B1D94872                 mov     [rbp-88h], rdx .text:00005593B1D94879                 mov     rax, '.s**.***' .text:00005593B1D94883                 mov     rdx, '****..*.' .text:00005593B1D9488D                 mov     [rbp-80h], rax .text:00005593B1D94891                 mov     [rbp-78h], rdx .text:00005593B1D94895                 mov     rax, '.****.**' .text:00005593B1D9489F                 mov     rdx, '********' .text:00005593B1D948A9                 mov     [rbp-70h], rax .text:00005593B1D948AD                 mov     [rbp-68h], rdx .text:00005593B1D948B1                 mov     rax, '***..***' .text:00005593B1D948BB                 mov     rdx, '*#..**..' .text:00005593B1D948C5                 mov     [rbp-60h], rax .text:00005593B1D948C9                 mov     [rbp-58h], rdx .text:00005593B1D948CD                 mov     rax, '*..***..' .text:00005593B1D948D7                 mov     rdx, '*****.**' .text:00005593B1D948E1                 mov     [rbp-50h], rax .text:00005593B1D948E5                 mov     [rbp-48h], rdx .text:00005593B1D948E9                 mov     rax, '********' .text:00005593B1D948F3                 mov     rdx, '.*******' .text:00005593B1D948FD                 mov     [rbp-40h], rax .text:00005593B1D94901                 mov     [rbp-38h], rdx .text:00005593B1D94905                 mov     rax, '****..**' .text:00005593B1D9490F                 mov     rdx, '.**..***' .text:00005593B1D94919                 mov     [rbp-30h], rax .text:00005593B1D9491D                 mov     [rbp-28h], rdx .text:00005593B1D94921                 mov     rax, '*.*..*..' .text:00005593B1D9492B                 mov     [rbp-20h], rax .text:00005593B1D9492F                 mov     dword ptr [rbp-18h], '.**.' .text:00005593B1D94936                 mov     word ptr [rbp-14h], 2Ah ; '*' .text:00005593B1D9493C                 mov     qword ptr [rbp-130h], 0 .text:00005593B1D94947                 mov     qword ptr [rbp-128h], 0 .text:00005593B1D94952                 mov     dword ptr [rbp-120h], 0 .text:00005593B1D9495C                 lea     rax, [rbp-90h] .text:00005593B1D94963                 add     rax, 16h .text:00005593B1D94967                 mov     [rbp-148h], rax .text:00005593B1D9496E                 mov     rax, '019_ftcs' ; sctf_019 .text:00005593B1D94978                 mov     [rbp-13Ah], rax .text:00005593B1D9497F                 mov     word ptr [rbp-132h], 32h ; '2' ; sctf_2019 .text:00005593B1D94988                 xor     rax, rax .text:00005593B1D9498B                 jb      short loc_5593B1D94990 .text:00005593B1D9498D                 jnb     short loc_5593B1D94990 .text:00005593B1D9498D ; --------------------------------------------------------------------------- .text:00005593B1D9498F                 db 0E1h .text:00005593B1D94990 ; --------------------------------------------------------------------------- .text:00005593B1D94990 .text:00005593B1D94990 loc_5593B1D94990:                      ; CODE XREF: .text:00005593B1D9498B↑j .text:00005593B1D94990                                        ; .text:00005593B1D9498D↑j .text:00005593B1D94990                 lea     rdi, aPlzTellMeTheSh ; "plz tell me the shortest password1:" .text:00005593B1D94997                 call    _puts .text:00005593B1D9499C                 lea     rax, [rbp-0D0h] .text:00005593B1D949A3                 mov     rsi, rax .text:00005593B1D949A6                 lea     rdi, aS        ; "%s" .text:00005593B1D949AD                 mov     eax, 0 .text:00005593B1D949B2                 call    _scanf .text:00005593B1D949B7                 mov     dword ptr [rbp-14Ch], 1 .text:00005593B1D949C1 .text:00005593B1D949C1 loc_5593B1D949C1:                      ; CODE XREF: .text:00005593B1D94A9F↓j .text:00005593B1D949C1                 cmp     dword ptr [rbp-14Ch], 0 .text:00005593B1D949C8                 jz      loc_5593B1D94AB1 .text:00005593B1D949CE                 mov     eax, [rbp-150h] .text:00005593B1D949D4                 cdqe .text:00005593B1D949D6 .text:00005593B1D949D6 loc_5593B1D949D6: .text:00005593B1D949D6                 lea     rdx, [rbp-0D0h] .text:00005593B1D949DD                 add     rax, rdx .text:00005593B1D949E0                 movzx   eax, byte ptr [rax] .text:00005593B1D949E3                 mov     [rbp-151h], al .text:00005593B1D949E9                 cmp     byte ptr [rbp-151h], 77h ; 'w' .text:00005593B1D949F0                 jnz     short loc_5593B1D949FC .text:00005593B1D949F2                 sub     qword ptr [rbp-148h], 5 .text:00005593B1D949FA                 jmp     short loc_5593B1D94A66 .text:00005593B1D949FC ; --------------------------------------------------------------------------- .text:00005593B1D949FC .text:00005593B1D949FC loc_5593B1D949FC:                      ; CODE XREF: .text:00005593B1D949F0↑j .text:00005593B1D949FC                 cmp     byte ptr [rbp-151h], 73h ; 's' .text:00005593B1D94A03                 jnz     short loc_5593B1D94A0F .text:00005593B1D94A05                 add     qword ptr [rbp-148h], 5 .text:00005593B1D94A0D                 jmp     short loc_5593B1D94A66 .text:00005593B1D94A0F ; --------------------------------------------------------------------------- .text:00005593B1D94A0F .text:00005593B1D94A0F loc_5593B1D94A0F:                      ; CODE XREF: .text:00005593B1D94A03↑j .text:00005593B1D94A0F                 cmp     byte ptr [rbp-151h], 64h ; 'd' .text:00005593B1D94A16                 jnz     short loc_5593B1D94A22 .text:00005593B1D94A18                 add     qword ptr [rbp-148h], 1 .text:00005593B1D94A20                 jmp     short loc_5593B1D94A66 .text:00005593B1D94A22 ; --------------------------------------------------------------------------- .text:00005593B1D94A22 .text:00005593B1D94A22 loc_5593B1D94A22:                      ; CODE XREF: .text:00005593B1D94A16↑j .text:00005593B1D94A22                 cmp     byte ptr [rbp-151h], 61h ; 'a' .text:00005593B1D94A29                 jnz     short loc_5593B1D94A35 .text:00005593B1D94A2B                 sub     qword ptr [rbp-148h], 1 .text:00005593B1D94A33                 jmp     short loc_5593B1D94A66 .text:00005593B1D94A35 ; --------------------------------------------------------------------------- .text:00005593B1D94A35 .text:00005593B1D94A35 loc_5593B1D94A35:                      ; CODE XREF: .text:00005593B1D94A29↑j .text:00005593B1D94A35                 cmp     byte ptr [rbp-151h], 78h ; 'x' .text:00005593B1D94A3C                 jnz     short loc_5593B1D94A48 .text:00005593B1D94A3E                 add     qword ptr [rbp-148h], 19h .text:00005593B1D94A46                 jmp     short loc_5593B1D94A66 .text:00005593B1D94A48 ; --------------------------------------------------------------------------- .text:00005593B1D94A48 .text:00005593B1D94A48 loc_5593B1D94A48:                      ; CODE XREF: .text:00005593B1D94A3C↑j .text:00005593B1D94A48                 cmp     byte ptr [rbp-151h], 79h ; 'y' .text:00005593B1D94A4F                 jnz     short loc_5593B1D94A5B .text:00005593B1D94A51                 sub     qword ptr [rbp-148h], 19h .text:00005593B1D94A59                 jmp     short loc_5593B1D94A66 .text:00005593B1D94A5B ; --------------------------------------------------------------------------- .text:00005593B1D94A5B .text:00005593B1D94A5B loc_5593B1D94A5B:                      ; CODE XREF: .text:00005593B1D94A4F↑j .text:00005593B1D94A5B                 mov     dword ptr [rbp-14Ch], 0 .text:00005593B1D94A65                 nop .text:00005593B1D94A66 .text:00005593B1D94A66 loc_5593B1D94A66:                      ; CODE XREF: .text:00005593B1D949FA↑j .text:00005593B1D94A66                                        ; .text:00005593B1D94A0D↑j ... .text:00005593B1D94A66                 add     dword ptr [rbp-150h], 1 .text:00005593B1D94A6D                 mov     rax, [rbp-148h] .text:00005593B1D94A74                 movzx   eax, byte ptr [rax] .text:00005593B1D94A77                 cmp     al, 2Eh ; '.' .text:00005593B1D94A79                 jz      short loc_5593B1D94A93 .text:00005593B1D94A7B                 mov     rax, [rbp-148h] .text:00005593B1D94A82                 movzx   eax, byte ptr [rax] .text:00005593B1D94A85                 cmp     al, 23h ; '#' .text:00005593B1D94A87                 jz      short loc_5593B1D94A93 .text:00005593B1D94A89                 mov     dword ptr [rbp-14Ch], 0 .text:00005593B1D94A93 .text:00005593B1D94A93 loc_5593B1D94A93:                      ; CODE XREF: .text:00005593B1D94A79↑j .text:00005593B1D94A93                                        ; .text:00005593B1D94A87↑j .text:00005593B1D94A93                 mov     rax, [rbp-148h] .text:00005593B1D94A9A                 movzx   eax, byte ptr [rax] .text:00005593B1D94A9D                 cmp     al, 23h ; '#' .text:00005593B1D94A9F                 jnz     loc_5593B1D949C1 .text:00005593B1D94AA5                 lea     rdi, aGoodYouFindThe ; "good!you find the right way!\nBut there"... .text:00005593B1D94AAC                 call    _puts .text:00005593B1D94AB1 .text:00005593B1D94AB1 loc_5593B1D94AB1:                      ; CODE XREF: .text:00005593B1D949C8↑j .text:00005593B1D94AB1                 cmp     dword ptr [rbp-14Ch], 0 .text:00005593B1D94AB8                 jnz     short loc_5593B1D94AD5 .text:00005593B1D94ABA                 lea     rdi, aSorryIsTNotARi ; "sorry,is't not a right way..." .text:00005593B1D94AC1                 mov     eax, 0 .text:00005593B1D94AC6                 call    _printf .text:00005593B1D94ACB                 mov     eax, 0 .text:00005593B1D94AD0                 jmp     loc_5593B1D94C0C

先赋值迷宫，总共六个控制键，好像是三维的，但是可以化成一维。

w/s分别为后退/前进五格，a/d分别为后退/前进一格，y/x分别为后退/前进25格。

把迷宫换成一维，最终要使s和#相遇。

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1	**************.****.**s..*..******.****.***********..***..**..#*..***..***.*****

得到sxss

第二关。
输入字符进入进入函数，最终和sctf_9102对比。
汇编看起来比较麻烦，不能f5的原因是中间多了一个0XE4字节，可以手动nop掉。

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.text:0000000000000E11                 jnb     short loc_E14 .text:0000000000000E11 ; --------------------------------------------------------------------------- .text:0000000000000E13                 db 0E4h .text:0000000000000E14 ; --------------------------------------------------------------------------- .text:0000000000000E14 .text:0000000000000E14 loc_E14:                               ; CODE XREF: .text:0000000000000E0F↑j .text:0000000000000E14                                        ; .text:0000000000000E11↑j .text:0000000000000E14                 mov     dword ptr [rbp-244h], 0 .text:0000000000000E1E .text:0000000000000E1E loc_E1E:                               ; CODE XREF: .text:0000000000000F4B↓j .text:0000000000000E1E                 cmp     dword ptr [rbp-238h], 0

nop之后

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01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82

unsigned __int64 __fastcall sub_C22(const char *a1, __int64 a2) {   bool v2; // al   int v3; // eax   int v4; // eax   int v5; // eax   int v7; // [rsp+14h] [rbp-24Ch]   signed int v8; // [rsp+18h] [rbp-248h]   int v9; // [rsp+1Ch] [rbp-244h]   int v10; // [rsp+20h] [rbp-240h]   int v11; // [rsp+24h] [rbp-23Ch]   int v12; // [rsp+28h] [rbp-238h]   int v13; // [rsp+2Ch] [rbp-234h]   char *v14; // [rsp+48h] [rbp-218h]   int v15[130]; // [rsp+50h] [rbp-210h]   unsigned __int64 v16; // [rsp+258h] [rbp-8h]     v16 = __readfsqword(0x28u);   qmemcpy(v15, &off_1740, 0x200uLL);   v8 = 3;   v7 = 0;   v10 = 0;   v11 = 0;   v12 = strlen(a1);   v14 = (char *)a1;   while ( 1 )   {     v13 = 0;     if ( v10 < v12 )       break; LABEL_13:     if ( v10 >= v12 )       goto LABEL_14;   }   do   {     if ( a1[v10] != 25 )       break;     ++v10;     ++v13;   }   while ( v10 < v12 );   if ( v10 != v12 )   {     if ( v12 - v10 > 1 )     {       v2 = v10 == 19 && a1[20] == 16;       a1[v2];     }     ++v10;     goto LABEL_13;   } LABEL_14:   v9 = 0;   while ( v12 > 0 )   {     v8 -= v15[*v14] == 64;     v7 = v15[*v14] & 0x3F | (v7 << 6);     if ( ++v9 == 4 )     {       v9 = 0;       if ( v8 )       {         v3 = v11++;         *(_BYTE *)(v3 + a2) = BYTE2(v7);       }       if ( v8 > 1 )       {         v4 = v11++;         *(_BYTE *)(v4 + a2) = BYTE1(v7);       }       if ( v8 > 2 )       {         v5 = v11++;         *(_BYTE *)(v5 + a2) = v7;       }     }     ++v14;     --v12;   }   return __readfsqword(0x28u) ^ v16; }

其实这代码的原理就是，输入字符分成四个一组，每次取8位二进制索引字符，取字符低6位，一组可以得到4个6位二进制，最终一组得到3个字符。

可以逆推得到password2:c2N0Zl85MTAy

第三关。

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01 02 03 04 05 06 07 08 09 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70

signed __int64 __fastcall sub_5593B1D94FFA(char *a1) {   int v1; // ST24_4   int v2; // ST28_4   int v3; // ST2C_4   signed int v5; // [rsp+18h] [rbp-158h]   signed int i; // [rsp+18h] [rbp-158h]   int cout; // [rsp+1Ch] [rbp-154h]   int v8[16]; // [rsp+30h] [rbp-140h]   int v9[16]; // [rsp+70h] [rbp-100h]   int v10[29]; // [rsp+B0h] [rbp-C0h]   unsigned int v11; // [rsp+124h] [rbp-4Ch]   unsigned __int64 v12; // [rsp+168h] [rbp-8h]     v12 = __readfsqword(0x28u);   v8[0] = 0xBE;   v8[1] = '\x04';   v8[2] = '\x06';   v8[3] = 0x80;   v8[4] = 0xC5;   v8[5] = 0xAF;   v8[6] = 0x76;   v8[7] = 0x47;   v8[8] = 0x9F;   v8[9] = 0xCC;   v8[10] = 0x40;   v8[11] = 0x1F;   v8[12] = 0xD8;   v8[13] = 0xBF;   v8[14] = 0x92;   v8[15] = 0xEF;   v1 = (a1[6] << 8) | (a1[5] << 16) | (a1[4] << 24) | a1[7];   v2 = (a1[10] << 8) | (a1[9] << 16) | (a1[8] << 24) | a1[11];   v3 = (a1[14] << 8) | (a1[13] << 16) | (a1[12] << 24) | a1[15];// 16位   cout = 0;   v5 = 4;   v10[0] = byteswap_ulong((a1[2] << 8) | (a1[1] << 16) | (*a1 << 24) | (unsigned int)a1[3]);// 颠倒过来排列   v10[1] = byteswap_ulong(v1);   v10[2] = byteswap_ulong(v2);   v10[3] = byteswap_ulong(v3);   do   {     v10[v5] = sub_5593B1D9543B(v10[cout], v10[cout + 1], v10[cout + 2], v10[cout + 3]);     ++cout;     ++v5;   }   while ( v5 <= 29 );   v9[0] = (unsigned int)v10[26] >> 24;   v9[1] = BYTE2(v10[26]);   v9[2] = BYTE1(v10[26]);   v9[3] = LOBYTE(v10[26]);   v9[4] = (unsigned int)v10[27] >> 24;   v9[5] = BYTE2(v10[27]);   v9[6] = BYTE1(v10[27]);   v9[7] = LOBYTE(v10[27]);   v9[8] = (unsigned int)v10[28] >> 24;   v9[9] = BYTE2(v10[28]);   v9[10] = BYTE1(v10[28]);   v9[11] = LOBYTE(v10[28]);   v9[12] = v11 >> 24;   v9[13] = BYTE2(v11);   v9[14] = BYTE1(v11);   v9[15] = (unsigned __int8)v11;   for ( i = 0; i <= 15; ++i )   {     if ( v9[i] != v8[i] )       return 0xFFFFFFFFLL;   }   return 1LL; }

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__int64 __fastcall sub_5593B1D9543B(int a1, int a2, int a3, unsigned int a4) {   return a1 ^ (unsigned int)sub_5593B1D95464(a2 ^ a3 ^ a4); } __int64 __fastcall sub_5593B1D95464(unsigned int a1) {   int v1; // ST18_4   int v3[290]; // [rsp+20h] [rbp-490h]   unsigned __int64 v4; // [rsp+4A8h] [rbp-8h]     v4 = __readfsqword(0x28u);   qmemcpy(v3, &byte_5593B1D95940, 1152uLL);   v1 = (v3[BYTE2(a1)] << 16) | v3[(unsigned __int8)a1] | (v3[BYTE1(a1)] << 8) | (v3[a1 >> 24] << 24);   return __ROL4__(v1, 12) ^ (unsigned int)(__ROL4__(v1, 8) ^ __ROR4__(v1, 2)) ^ __ROR4__(v1, 6); }

输入字符，长度为16,分为四位一组，组成4个int元素，再大小端颠倒。然后第2,3,4元素异或进入函数索引字符再循环异或再跟第一个元素异或得到第五个元素，再用2,3,4,5重复相同步骤得到第六个元素，以此类推。
循环26次，取最高四个元素跟程序的值对比，可以写脚本逆推。

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i  = [0xd8bf92ef,0x9fcc401f,0xc5af7647,0xbe040680]   asc = [0xD6,0x90,0xE9,0xFE,0xCC,0xE1,0x3D,0xB7,0x16,0xB6,0x14,0xC2,0x28,0xFB,0x2C,0x05,0x2B,0x67,0x9A,0x76,0x2A,0xBE,0x04,0xC3,0xAA,0x44,0x13,0x26,0x49,0x86,0x06,0x99,0x9C,0x42,0x50,0xF4,0x91,0xEF,0x98,0x7A,0x33,0x54,0x0B,0x43,0xED,0xCF,0xAC,0x62,0xE4,0xB3,0x1C,0xA9,0xC9,0x08,0xE8,0x95,0x80,0xDF,0x94,0xFA,0x75,0x8F,0x3F,0xA6,0x47,0x07,0xA7,0xFC,0xF3,0x73,0x17,0xBA,0x83,0x59,0x3C,0x19,0xE6,0x85,0x4F,0xA8,0x68,0x6B,0x81,0xB2,0x71,0x64,0xDA,0x8B,0xF8,0xEB,0x0F,0x4B,0x70,0x56,0x9D,0x35,0x1E,0x24,0x0E,0x5E,0x63,0x58,0xD1,0xA2,0x25,0x22,0x7C,0x3B,0x01,0x21,0x78,0x87,0xD4,0x00,0x46,0x57,0x9F,0xD3,0x27,0x52,0x4C,0x36,0x02,0xE7,0xA0,0xC4,0xC8,0x9E,0xEA,0xBF,0x8A,0xD2,0x40,0xC7,0x38,0xB5,0xA3,0xF7,0xF2,0xCE,0xF9,0x61,0x15,0xA1,0xE0,0xAE,0x5D,0xA4,0x9B,0x34,0x1A,0x55,0xAD,0x93,0x32,0x30,0xF5,0x8C,0xB1,0xE3,0x1D,0xF6,0xE2,0x2E,0x82,0x66,0xCA,0x60,0xC0,0x29,0x23,0xAB,0x0D,0x53,0x4E,0x6F,0xD5,0xDB,0x37,0x45,0xDE,0xFD,0x8E,0x2F,0x03,0xFF,0x6A,0x72,0x6D,0x6C,0x5B,0x51,0x8D,0x1B,0xAF,0x92,0xBB,0xDD,0xBC,0x7F,0x11,0xD9,0x5C,0x41,0x1F,0x10,0x5A,0xD8,0x0A,0xC1,0x31,0x88,0xA5,0xCD,0x7B,0xBD,0x2D,0x74,0xD0,0x12,0xB8,0xE5,0xB4,0xB0,0x89,0x69,0x97,0x4A,0x0C,0x96,0x77,0x7E,0x65,0xB9,0xF1,0x09,0xC5,0x6E,0xC6,0x84,0x18,0xF0,0x7D,0xEC,0x3A,0xDC,0x4D,0x20,0x79,0xEE,0x5F,0x3E,0xD7,0xCB,0x39,0x48,0xC6,0xBA,0xB1,0xA3,0x50,0x33,0xAA,0x56,0x97,0x91,0x7D,0x67,0xDC,0x22,0x70,0xB2]   def xors(xor_mix):     temp1 = (xor_mix >> 24)&0xff     temp2 = (xor_mix >> 16)&0xff     temp3 = (xor_mix >> 8)&0xff     temp = (xor_mix)&0xff       temp_q = asc[temp] | (asc[temp1]<<24)|(asc[temp2]<<16)|(asc[temp3]<<8)     print ("%x"%(temp_q))     temp_i = ((temp_q <<12|temp_q>>20)&0xffffffff) ^ ((temp_q <<8|temp_q>>24)&0xffffffff) ^ ((temp_q>>2|temp_q<<30)&0xffffffff)^((temp_q>>6|temp_q<<26)&0xffffffff)     return temp_i   print ("%x"%(xors(0x6011F432))) print (len(asc))   for q in range(26):     i.append(i[q]^xors(i[q+1]^i[q+2]^i[q+3]))   print (i) print ("%x"%(i[-1])) print ("%x"%(i[-2])) print ("%x"%(i[-3])) print ("%x"%(i[-4])) # fl4g_is_s0_ug1y!

得到fl4g_is_s0_ug1y!




music

app打开需要联网，不懂为啥。
查看代码

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package com.example.music;   import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase;   public class q {   private h h;   private Context mycontext;       public q(Context paramContext)   {     this.mycontext = paramContext;   }       public String get()   {     String str1 = null;     this.h = new h(this.mycontext, "sctf.db", null, 1);     Cursor localCursor = this.h.getWritableDatabase().query("SYC", null, null, null, null, null, null);     if (localCursor.moveToFirst()) {       do       {         str1 = localCursor.getString(localCursor.getColumnIndex("S1"));         String str2 = localCursor.getString(localCursor.getColumnIndex("S2"));         StringBuilder localStringBuilder = new StringBuilder();         localStringBuilder.append(str1);         localStringBuilder.append(str2);         str1 = localStringBuilder.toString();       } while (localCursor.moveToNext());     }     localCursor.close();     return str1;   } }

发现程序里边有.db文件，用SQLiteSpy打开。


得到hellosctf

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package com.example.music;   import java.security.MessageDigest;   public class a {   public String a(String paramString)   {     return b(paramString);   }       public String b(String paramString)   {     new p();     if (paramString != null) {       try       {         paramString = p.a(MessageDigest.getInstance("MD5").digest(paramString.getBytes()));         return paramString;       }       catch (Exception paramString)       {         paramString.printStackTrace();       }     }     return null;   } }

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package com.example.music;   public class p {   public static String a(byte[] paramArrayOfByte)   {     StringBuffer localStringBuffer = new StringBuffer();     int i = 0;     while (i < paramArrayOfByte.length)     {       String str = Integer.toHexString(paramArrayOfByte[i] & 0xFF);       Object localObject = str;       if (str.length() == 1)       {         localObject = new StringBuilder();         ((StringBuilder)localObject).append('0');         ((StringBuilder)localObject).append(str);         localObject = ((StringBuilder)localObject).toString();       }       localStringBuffer.append(((String)localObject).toUpperCase());       i += 1;     }     return localStringBuffer.toString();   } }

字母变大写，得到E7E64BF658BAB14A25C9D67A054CEBE5
然后和输入字符进入加密。

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package com.example.music;   public class c {   private static int m = 256;       public String a(String paramString1, String paramString2)   {     int i = m;     int[] arrayOfInt = new int[i];     byte[] arrayOfByte = new byte[i];     i = 0;     while (i < m)     {       arrayOfInt[i] = i;       arrayOfByte[i] = ((byte)paramString2.charAt(i % paramString2.length()));       i += 1;     }     i = 0;     int j = 0;     for (;;)     {       k = m;       if (i >= k - 1) {         break;       }       j = (arrayOfInt[i] + j + arrayOfByte[i]) % k;       k = arrayOfInt[i];       arrayOfInt[i] = arrayOfInt[j];       arrayOfInt[j] = k;       i += 1;     }     paramString2 = paramString1.toCharArray();     paramString1 = new char[paramString1.length()];     int k = 0;     j = 0;     i = 0;     while (i < paramString2.length)     {       int n = m;       k = (k + 1) % n;       j = (arrayOfInt[k] + j) % n;       int i1 = arrayOfInt[k];       arrayOfInt[k] = arrayOfInt[j];       arrayOfInt[j] = i1;       i1 = arrayOfInt[k];       int i2 = arrayOfInt[k];       paramString1[i] = ((char)(paramString2[i] - k ^ (char)arrayOfInt[((i1 + i2 % n) % n)]));       i += 1;     }     new p();     return p.a(new String(paramString1).getBytes());   } }

看起来是变种RC4

最终对比

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public boolean g(String paramString) {   return paramString.equals(s.this.getApplicationContext().getResources().getString(2131492904)); }

没动态调试环境，一直调试不了，后来发现应该是储存在Strings.xml文件里边。

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<string name="cipher">C28BC39DC3A6C283C2B3C39DC293C289C2B8C3BAC29EC3A0C3A7C29A1654C3AF28C3A1C2B1215B53</string> <string name="local">/data/data/com.example.music/databases/</string> <string name="no">wrong!</string> <string name="search_menu_title">Search</string> <string name="song">[audio]http://www.ytmp3.cn/down/44093.mp3[/audio]</string>

得到密文，看到一个网址，应该是需要联网的原因，程序开始需要听一段音乐，音乐应该就是这个网址里边的。

密文是经过大写变换的，变成小写可以得到c28bc39dc3a6c283c2b3c39dc293c289c2b8c3bac29ec3a0c3a7c29a1654c3af28c3a1c2b1215b53

但是即使这样，用python写脚本一直写不通.

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import base64 flag = "c28bc39dc3a6c283c2b3c39dc293c289c2b8c3bac29ec3a0c3a7c29a1654c3af28c3a1c2b1215b53" flagh = [] for q in range(0,len(flag),2):         flagh.append(int(flag[q:q+2],16))   print flagh   S = [] T = [] key = "E7E64BF658BAB14A25C9D67A054CEBE5"   # C28BC39DC3A6C283C2B3C39DC293C289C2B8C3BAC29EC3A0C3A7C29A1654C3AF28C3A1C2B1215B53 # c28bc39dc3a6c283c2b3c39dc293c289c2b8c3bac29ec3a0c3a7c29a1654c3af28c3a1c2b1215b53 for i in range(256):     S.append(i)     T.append(key[i%len(key)])   #print S #print T   j = 0 for i in range(256):     j = (j+S[i]+ord(T[i]))%256       S[i],S[j]=S[j],S[i]   i = 0 j = 0 k = [] # for r in range(len(flag)): #         i = (i+1)%256 #         j = (j+S[i])%256 #         S[i],S[j] = S[j],S[i] #         t = (S[i]+S[j])%256 #         k.append(S[t]) #         flags = [] for r in range(len(flagh)):         i = (i+1)%256         j = (j+S[i])%256         S[i],S[j] = S[j],S[i]         t = (S[i]+S[j])%256         k.append(S[t])         flags.append((flagh[r] ^ S[(S[i] + S[i] % 256) % 256]) + i)   print flags

后来发现先知社区有大佬写wp了。
引用他们的脚本

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1	https://xz.aliyun.com/t/5478#toc-21

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public class Notepad {     public static void main(String[] args)     {         byte[] enctob = new byte[]{-62, -117, -61, -99, -61, -90, -62, -125, -62, -77, -61, -99, -62, -109, -62, -119, -62, -72, -61, -70, -62, -98, -61, -96, -61, -89, -62, -102, 22, 84, -61, -81, 40, -61, -95, -62, -79, 33, 91, 83};               String bs = new String(enctob);         char[] flagenc = bs.toCharArray();         char[] out = new char[bs.length()];         int[] S = new int[256];         byte[] wtf = new byte[256];         int i,j,k;         String key = "E7E64BF658BAB14A25C9D67A054CEBE5";         for (i = 0; i < 256; i++ )         {             S[i] = i;             wtf[i] = (byte)(key.charAt(i % 32));         }         i = 0;         j = 0;         for(i = 0,j = 0;i < 256; i++ )         {             j = (S[i] + j + wtf[i]) % 256;             k = S[i];             S[i] = S[j];             S[j] = k;         }         for (i = 0,j = 0,k = 0; i < bs.length(); i++ )         {             k = (k + 1) % 256;             j = (S[k] + j) % 256;             int temp = S[k];             S[k] = S[j];             S[j] = temp;             out[i] = (char)((flagenc[i] ^ S[(S[k] + S[k] % 256) % 256]) + k);             System.out.println(out);         }       } }

得到flag

他们中出现了两句
String bs = new String(enctob);
        char[] flagenc = bs.toCharArray();
可能是编码问题,这个问题有待解决

0xEASONs

编码问题是因为一个字符getByte是两个

瑟瑟发抖小菜虾

大佬写的博客太好了。。。。。 想前排请问一下大佬 第一个题的脚本有没有 别的方法（感觉这个有点麻烦鸭）

姚小宝

瑟瑟发抖小菜虾 发表于 2019-6-24 21:25
大佬写的博客太好了。。。。。 想前排请问一下大佬 第一个题的脚本有没有 别的方法（感觉这个有点麻烦鸭）

应该有吧，只不过我对安卓平台接触不多不知道。

0xEASONs

Hotspur

膜拜大佬，当时babyre那题卡在最后一步半天没做出来。。。
第二步其实是个base64解密。。不过要多输入一个‘=’。。当时把最后一位是’=‘推出来后直接想到base，一解密还真成了。

姚小宝

Hotspur 发表于 2019-6-26 17:22
膜拜大佬，当时babyre那题卡在最后一步半天没做出来。。。
第二步其实是个base64解密。。不过要多输入一个 ...

嗯，就是base64解密，还原之后才反映过来