[buuctf.reverse] 109_[FlareOn6]FlareBear,110_[INSHack2018]Tricky-Part1

109_[FlareOn6]FlareBear

java这东西看着也费劲，就没有一种一看就明白的语言吗

题目是一个apk的文件，安装到雷电上是个小游戏，有3个选项，吃、玩、铲屎

再看代码，这个danceWithFlag是结果，通过调用关系找到他的上级setMood这里边用isEcstatic()检查是否成功，检查内容是3个变量为72,30,0

    public final void dance(@NotNull Drawable drawable, @NotNull Drawable drawable2) {
        Intrinsics.checkParameterIsNotNull(drawable, "drawable");
        Intrinsics.checkParameterIsNotNull(drawable2, "drawable2");
        this.handler.removeCallbacksAndMessages(null);
        ((ImageView) _$_findCachedViewById(R.id.flareBearImageView)).setImageDrawable(drawable);
        ((ImageView) _$_findCachedViewById(R.id.flareBearImageView)).setTag("ecstatic");
        Handler handler = new Handler();
        handler.postDelayed(new FlareBearActivity$dance$r$1(this, handler, drawable2, drawable), 500);
    }

    public final void danceWithFlag() {
        InputStream openRawResource = getResources().openRawResource(R.raw.ecstatic);
        Intrinsics.checkExpressionValueIsNotNull(openRawResource, "ecstaticEnc");
        byte[] readBytes = ByteStreamsKt.readBytes(openRawResource);
        InputStream openRawResource2 = getResources().openRawResource(R.raw.ecstatic2);
        Intrinsics.checkExpressionValueIsNotNull(openRawResource2, "ecstaticEnc2");
        byte[] readBytes2 = ByteStreamsKt.readBytes(openRawResource2);
        String password = getPassword();
        try {
            readBytes = decrypt(password, readBytes);
            readBytes2 = decrypt(password, readBytes2);
            dance(new BitmapDrawable(getResources(), BitmapFactory.decodeByteArray(readBytes, 0, readBytes.length)), new BitmapDrawable(getResources(), BitmapFactory.decodeByteArray(readBytes2, 0, readBytes2.length)));
        } catch (Exception unused) {
        }
    }

    public final void setMood() {
        if (isHappy()) {
            ((ImageView) _$_findCachedViewById(R.id.flareBearImageView)).setTag("happy");
            if (isEcstatic()) {
                danceWithFlag();
                return;
            }
            return;
        }
        ((ImageView) _$_findCachedViewById(R.id.flareBearImageView)).setTag("sad");
    }

    public final boolean isEcstatic() {
        int state = getState("mass", 0);
        int state2 = getState("happy", 0);
        int state3 = getState("clean", 0);
        if (state == 72 && state2 == 30 && state3 == 0) {
            return true;
        }
        return false;
    }

再看怎么改变这3项

   public final void feed(@NotNull View view) {
        Intrinsics.checkParameterIsNotNull(view, "view");
        saveActivity("f");
        changeMass(10);
        changeHappy(2);
        changeClean(-1);
        incrementPooCount();
        feedUi();
    }
    public final void play(@NotNull View view) {
        Intrinsics.checkParameterIsNotNull(view, "view");
        saveActivity("p");
        changeMass(-2);
        changeHappy(4);
        changeClean(-1);
        playUi();
    }
    public final void clean(@NotNull View view) {
        Intrinsics.checkParameterIsNotNull(view, "view");
        saveActivity("c");
        removePoo();
        cleanUi();
        changeMass(0);
        changeHappy(-1);
        changeClean(6);
        setMood();
    }

简单列个方程计算一下，结果是吃8次玩4次铲屎2次

from z3 import *
x,y,z = Ints('x y z')
s = Solver()
s.add([10*x - 2*y == 72, 2*x+4*y-z==30, z*6-x-y==0])
s.check()
d = s.model()
print(d)
#[z = 2, y = 4, x = 8]
#flag{[email protected]}

 

110_[INSHack2018]Tricky-Part1

这个比较入门了

直接在main里输入然后就检查

int __cdecl main(int argc, const char **argv, const char **envp)
{
  int v3; // ebx
  char v4; // bl
  __int64 v5; // rax
  char v7[16]; // [rsp+0h] [rbp-30h] BYREF
  char v8[32]; // [rsp+10h] [rbp-20h] BYREF

  if ( ptrace(PTRACE_TRACEME, 0LL, 1LL, 0LL) >= 0 )
  {
    std::string::string((std::string *)v7);
    std::operator<<<std::char_traits<char>>(&std::cout, "Enter your flag : ");
    std::operator>><char>(&std::cin, v7);
    stack_check();
    v4 = std::operator==<char>(v7, v8);
    std::string::~string(v8);
    if ( v4 )
      v5 = std::operator<<<std::char_traits<char>>(
             &std::cout,
             "Correct but this is just the first one\nValidate with the flag");
    else
      v5 = std::operator<<<std::char_traits<char>>(&std::cout, "Sooo bad. Are you trying to trick me ?");
    std::ostream::operator<<(v5, &std::endl<char,std::char_traits<char>>);
    v3 = 0;
    std::string::~string(v7);
  }
  else
  {
    std::operator<<<std::char_traits<char>>(&std::cout, "Oh no, don't debug me plz\n");
    return 42;
  }
  return v3;
}

stack_check()负责将存的数据加密（与GDB异或）

std::string *__fastcall stack_check(std::string *a1)
{
  unsigned __int64 v1; // rbx
  unsigned __int64 v2; // rax
  _BYTE *v3; // rax
  unsigned __int64 v4; // rbx
  char v6; // [rsp+1Bh] [rbp-25h] BYREF
  int i; // [rsp+1Ch] [rbp-24h]
  char v8[32]; // [rsp+20h] [rbp-20h] BYREF

  std::allocator<char>::allocator(&v6);
  std::string::string(v8, &unk_4011D8, &v6);
  std::allocator<char>::~allocator(&v6);
  for ( i = 0; ; ++i )
  {
    v4 = i;
    if ( v4 >= std::string::size((std::string *)&base) )
      break;
    v1 = i;
    v2 = std::string::size((std::string *)v8);
    LOBYTE(v1) = *(_BYTE *)std::string::operator[](v8, v1 % v2);
    v3 = (_BYTE *)std::string::operator[](&base, i);
    *v3 ^= v1;
  }
  std::string::string(a1, (const std::string *)&base);
  std::string::~string(v8);
  return a1;
}

只是这个base的值在哪还不清楚，于是找引用发现变动之处，它是直接复制的unk_401278的值

int __fastcall __static_initialization_and_destruction_0(int a1, int a2)
{
  int result; // eax
  char v3[17]; // [rsp+1Fh] [rbp-11h] BYREF

  if ( a1 == 1 && a2 == 0xFFFF )
  {
    std::ios_base::Init::Init((std::ios_base::Init *)&std::__ioinit);
    __cxa_atexit(std::ios_base::Init::~Init, &std::__ioinit, &_dso_handle);
    std::allocator<char>::allocator(v3);
    std::string::string(&base, &unk_401278, v3);
    std::allocator<char>::~allocator(v3);
    return __cxa_atexit(std::string::~string, &base, &_dso_handle);
  }
  return result;
}

写脚本处理一下

a = bytes.fromhex('0E0A11063F011F1C1D76371D2F7030237730182272351B3133703676271D732A762B75313E371D302C71291B26742637202371351B2473752E3439')
b = b'GDB'
print(bytes([a[i]^b[i%3] for i in range(len(a))]))
#INSA{CXX_1s_h4rd3r_f0r_st4t1c_4n4l1sys_wh3n_d3bugg3r_f41ls}
#flag{CXX_1s_h4rd3r_f0r_st4t1c_4n4l1sys_wh3n_d3bugg3r_f41ls}