rebug 1

Flag

csawctf{c20ad4d76fe97759aa27a0c99bff6710}

Solution

main decompiled with Ghidra:

undefined8 main(void)
(snip)
  printf("Enter the String: ");
  __isoc99_scanf(&DAT_00102017,local_408);
  for (local_c = 0; local_408[local_c] != '\0'; local_c = local_c + 1) {
  }
  if (local_c == 0xc) {
    puts("that\'s correct!");

It loops over the length of the input value and increments local_c.
If local_c is 0xc (12), output that's correct!.

Thus, I should enter the length of 12 characters.

root@kali:~/ctf/CSAW-CTF-2023-Quals/rev/rebug 1# echo -ne '123456789012' | ./test.out
Enter the String: that's correct!
csawctf{c20ad4d76fe97759aa27a0c99bff6710}