[HFCTF 2021 Final]easyflask

根据指引拿到源码，之前访问网页拿到的源码是无缩进的，我还以为是出题人故意这样，后来才知道view-source一下能看到有缩进的源代码。

#!/usr/bin/python3.6
import os
import pickle

from base64 import b64decode
from flask import Flask, request, render_template, session

app = Flask(__name__)
app.config["SECRET_KEY"] = "*******"

User = type('User', (object,), {
    'uname': 'test',
    'is_admin': 0,
    '__repr__': lambda o: o.uname,
})


@app.route('/', methods=('GET',))
def index_handler():
    if not session.get('u'):
        u = pickle.dumps(User())
        session['u'] = u
    return "/file?file=index.js"


@app.route('/file', methods=('GET',))
def file_handler():
    path = request.args.get('file')
    path = os.path.join('static', path)
    if not os.path.exists(path) or os.path.isdir(path) \
            or '.py' in path or '.sh' in path or '..' in path or "flag" in path:
        return 'disallowed'

    with open(path, 'r') as fp:
        content = fp.read()
    return content


@app.route('/admin', methods=('GET',))
def admin_handler():
    try:
        u = session.get('u')
        if isinstance(u, dict):
            u = b64decode(u.get('b'))
        u = pickle.loads(u)
    except Exception:
        return 'uhh?'

    if u.is_admin == 1:
        return 'welcome, admin'
    else:
        return 'who are you?'


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

首先来看一个东西：https://baijiahao.baidu.com/s?id=1646831894632441854&wfr=spider&for=pc

这里说明了python中所有的类都是type类的一个对象，所以定义类时可以普通定义，也可以使用type类定义，源代码中就是使用type类定义了一个User类，该类中有三个属性

User = type('User', (object,), {
    'uname': 'test',
    'is_admin': 0,
    '__repr__': lambda o: o.uname,
})