secret.py

import sys

def _getflag():
  orig_file = sys._getframe(1).f_code.co_filename
  if orig_file != __file__:
    print('who are you...?')
    exit(1)
  print("0nepts{fakeflag}")

def getflag():
  _getflag()

server.py

import sys
import secret
from secret import getflag

def trace(frame, op, args):
  if "secret" in frame.f_code.co_filename:
    print("DO NOT TOUCH MY PRECIOUS")
    exit(1)

sys.settrace(trace)

def audit(name, args):
  if name in ["builtins.id", "open", "sys.settrace", "object.__getattr__"] or name.startswith("gc."):
    exit(1)

sys.addaudithook(audit)

while True:
  print(eval(input(), {"getflag": getflag}, {}))