Why there is another bytes in stack which not allocated by local variables?

Question

I try to write my first CTF program which should be exploitable to Buffer-Overflow. In order to do that, I did the next simple steps:

1. Created a main function
2. Initialized two local variables - is_authorized(char of size 1) and password(array of size 128)
3. Disabled debug runtime checks - no canaries should be at the stack

So main look like this:

int main()
{
    char is_authorized = 't';
    char password[128] = { 0 };

    return 0;
}

In theory, the variables should be one after another on the stack, but what really happens very strangely, is that I have more three weird bytes between this two local variables.
Here is a snapshot of the memory when I debugged this program

0x0019FE70  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ...........................................
0x0019FE9B  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00  ...........................................
0x0019FEC6  00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 00 fc  ..........................................ü
0x0019FEF1  fe 19 74 14 ff 19 00 63 23 41 00 01 00 00 00 70 4b 94 00 60 4e 94 00 01 00 00 00 70 4b 94 00 60 4e 94 00 70 ff 19 00 b7 21 41 00  þ.t.ÿ..c#A.....pK”.`N”.....pK”.`N”.pÿ..·!A.

As you can see in the snapshot, there are more three bytes - fc fe 19 on the stack between the variable, hence I cant complete the buffer overflow. What are these weird bytes? The only thought I have in mind is the protection mechanism, but I disabled this, then what else it could be?

EDIT: For what it worth, here is the disassembly:

int main()
{
004116D0  push        ebp  
004116D1  mov         ebp,esp  
004116D3  sub         esp,0C4h  
004116D9  push        ebx  
004116DA  push        esi  
004116DB  push        edi  
004116DC  mov         ecx,offset _CC196ACA_main@c (041B000h)  
004116E1  call        @__CheckForDebuggerJustMyCode@4 (04111FEh)  
    char is_authorized = 't';
004116E6  mov         byte ptr [is_authorized],74h  
    char password[128];
    return 0;
004116EA  xor         eax,eax  
}
004116EC  pop         edi  
004116ED  pop         esi  
004116EE  pop         ebx  
}
004116EF  mov         esp,ebp  
004116F1  pop         ebp  
004116F2  ret  

Answer 1

the variables should be one after another on the stack

No, there is no such rule. Compiler should do anything, as long as side effects stay. A good compiler with optimizations should remove both variables from your code.

What are these weird bytes? The only thought I have in mind is the protection mechanism, but I disabled this, then what else it could be?

Padding between variables allocated on stack. Your non-optimizing compiler allocates stack variables aligned to an address divisible by 4. Hence 3 bytes padding between the next char variable. The values of the bytes are most probably left-over garbage left on stack by program initialization routines.