We can see the checkpass() function first converts string to hex and then checks the values by hardcoded flag. We can easily get the flag by formatting the hardcoded values and then converting them to string with python.

_input = [0x63, 0x61, 0x73, 0x74,
          0x6f, 0x72, 0x73, 0x43, 0x54,
          0x46, 0x7b, 0x72, 0x31, 0x78,
          0x54, 0x79, 0x5f,
          0x6d, 0x31, 0x6e,
          0x75, 0x74, 0x33, 0x73, 0x5f, 0x67, 0x74,
          0x5f, 0x73, 0x31, 0x78, 0x74, 0x79, 0x5f, 0x6d,
          0x31, 0x6e, 0x75, 0x74, 0x33,
          0x73, 0x7d]
for i in _input:
    print(chr(i), end="")

Flag: castorsCTF{r1xTy_m1nut3s_gt_s1xty_m1nut3s}