EasyCrackMe:)

This is our first crackme in the crackme series, downloading the file and unzipping it we have:

runnig the file with wine emulator we could see that it prompts us for a password

let’s run strings on the file and see what we got:

we could see the part that asks us for the password and also a 5 digit number, now this could possibly be the password let’s try it out,

yeah it worked but what’s really going on here ?????

let’s plug it in binja and see what it decompiles to :

we could see that the password is read from memory and loaded into rdx with the assembly lea, then the user is asked for input which is then stored into a register, a while loop then iterates through the user input and compares it with the loaded password in memeory which for every character if there’s a mismatch it breaks and returns incorrect password.

let’s plut it into IDAPro for more psuedoCode info

---

int __cdecl main(int argc, const char **argv, const char **envp)
{
  __int64 v3; // r8
  __int64 v4; // r8
  __int64 v5; // r8
  void **v6; // rdx
  char *v7; // rbx
  unsigned __int64 v8; // rdi
  __int64 v9; // rax
  unsigned __int8 v10; // cl
  int v11; // eax
  __int64 v12; // r8
  __int64 v13; // r8
  __int64 v14; // r8
  char *v15; // rax
  void *Block[2]; // [rsp+20h] [rbp-38h] BYREF
  __int64 v18; // [rsp+30h] [rbp-28h]
  unsigned __int64 v19; // [rsp+38h] [rbp-20h]

  *(_OWORD *)Block = 0i64;
  v18 = 0i64;
  v19 = 15i64;
  LOBYTE(Block[0]) = 0;
  sub_7FF77B8615A0(std::cout, "Welcome to EasyCrackMe!!!\n", envp);
  sub_7FF77B8615A0(std::cout, "\n", v3);
  while ( 1 )
  {
    sub_7FF77B8615A0(std::cout, "Password: ", v4);
    sub_7FF77B861770(std::cin, Block);
    v6 = Block;
    v7 = (char *)Block[0];
    v8 = v19;
    if ( v19 >= 16 )
      v6 = (void **)Block[0];
    if ( v18 == 5 )
    {
      v9 = 0i64;
      while ( 1 )
      {
        v10 = *((_BYTE *)v6 + v9++);
        if ( v10 != a12345[v9 - 1] )
          break;
        if ( v9 == 5 )
        {
          v11 = 0;
          goto LABEL_10;
        }
      }
      v11 = v10 < (unsigned __int8)a12345[v9 - 1] ? -1 : 1;
LABEL_10:
      if ( !v11 )
        break;
    }
    sub_7FF77B8615A0(std::cout, "Incorrect :(\n", v5);
    sub_7FF77B8615A0(std::cout, "\n", v12);
    sub_7FF77B8615A0(std::cout, "\n", v13);
    sub_7FF77B8615A0(std::cout, "\n", v14);
  }
  sub_7FF77B8615A0(std::cout, "Correct :)", v5);
  if ( v8 >= 0x10 )
  {
    v15 = v7;
    if ( v8 + 1 >= 0x1000 )
    {
      v7 = (char *)*((_QWORD *)v7 - 1);
      if ( (unsigned __int64)(v15 - v7 - 8) > 0x1F )
        invalid_parameter_noinfo_noreturn();
    }
    j_j_free(v7);
  }
  return 0;
}

---

Here is a brief explanation of its functionality:

-The program starts with the main function, which takes command-line arguments argc, argv, and environment variables envp.

-Some variables (v3, v4, v5, v6, v7, v8, v9, v10, v11, v12, v13, v14, v15, Block, v18, v19) are declared.

-The program initializes Block as an array of 2 elements and sets other variables to specific initial values.

-The program prints “Welcome to EasyCrackMe!!!” to the standard output.

-The program enters a continuous loop where it prompts the user for a password and reads the input.

-The program compares the entered password with a predefined string “a12345”. If the password matches, the loop is exited; otherwise, an “Incorrect :(“ message is printed, and the loop continues.

-Once the correct password is entered, the program prints “Correct :)”.

-If the length of the entered password is greater than or equal to 16, the program frees memory allocated for the password string.

-The program returns 0, indicating successful execution.

Overall, this program is a simple password verification system where the user needs to enter the correct password to proceed.

what an easy challenge that’s all for now!!!!!!!!