Windows95 OEM key check code.

95oemCheck.c

// Credits and Thanks to Thomas Roth (https://github.com/nezza)
undefined2 __stdcall16far check_oem_key(char *key,int len)

{
  int key_length;
  int is_oem;
  int first_3_digits_int;
  int second_2_digits_int;
  undefined2 check_result;
  int i;
  int i_;
  char first_three_digits [4];
  char second_two_digits [3];
  char kc;
  
  key_length = LSTRLEN(key);
  if ((((key_length == 0x17) && (key[5] == '-')) && (key[9] == '-')) &&
     ((key[0x11] == '-' && (is_oem = check_oem_str(3,0x11704f9d,key + 6,len), is_oem == 0)))) {
                    /* Check first 5 digits, must be numeric */
    i = 0;
    do {
      kc = key[i];
      if (kc < '0') {
        return 0;
      }
      if ('9' < kc) {
        return 0;
      }
      i = i + 1;
    } while (i < 5);
                    /*  */
    copy_partial(3,key,len,first_three_digits);
    first_three_digits[3] = '\0';
    first_3_digits_int = atoi(first_three_digits);
    if ((first_3_digits_int != 0) &&
       (first_3_digits_int < 367
                    /* check if between 1 and 366 */)) {
      copy_partial(2,key + 3,len,second_two_digits);
      second_two_digits[2] = '\0';
      second_2_digits_int = atoi(second_two_digits);
      if (((second_2_digits_int < 3) || (94 < second_2_digits_int)) &&
         (((key[10] == '0' && ('0' < key[0x10])) && (key[0x10] < '8')))) {
        i_ = 0x12;
        while ((kc = key[i_], '/' < kc && (kc < ':'))) {
          i_ = i_ + 1;
          if (0x16 < i_) {
                    /* jump to part after oem- */
            check_result = mod7_check(key + 10,len);
            return check_result;
          }
        }
      }
    }
  }
  return 0;
}