session-basic 문제 풀이

오늘은 seession-basic문제를 풀이했다.

#!/usr/bin/python3
from flask import Flask, request, render_template, make_response, redirect, url_for

app = Flask(__name__)

try:
    FLAG = open('./flag.txt', 'r').read()
except:
    FLAG = '[**FLAG**]'

users = {
    'guest': 'guest',
    'user': 'user1234',
    'admin': FLAG
}


# this is our session storage
session_storage = {
}


@app.route('/')
def index():
    session_id = request.cookies.get('sessionid', None)
    try:
        # get username from session_storage
        username = session_storage[session_id]
    except KeyError:
        return render_template('index.html')

    return render_template('index.html', text=f'Hello {username}, {"flag is " + FLAG if username == "admin" else "you are not admin"}')


@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'GET':
        return render_template('login.html')
    elif request.method == 'POST':
        username = request.form.get('username')
        password = request.form.get('password')
        try:
            # you cannot know admin's pw
            pw = users[username]
        except:
            return '<script>alert("not found user");history.go(-1);</script>'
        if pw == password:
            resp = make_response(redirect(url_for('index')) )
            session_id = os.urandom(32).hex()
            session_storage[session_id] = username
            resp.set_cookie('sessionid', session_id)
            return resp
        return '<script>alert("wrong password");history.go(-1);</script>'


@app.route('/admin')
def admin():
    # developer's note: review below commented code and uncomment it (TODO)

    #session_id = request.cookies.get('sessionid', None)
    #username = session_storage[session_id]
    #if username != 'admin':
    #    return render_template('index.html')

    return session_storage


if __name__ == '__main__':
    import os
    # create admin sessionid and save it to our storage
    # and also you cannot reveal admin's sesseionid by brute forcing!!! haha
    session_storage[os.urandom(32).hex()] = 'admin'
    print(session_storage)
    app.run(host='0.0.0.0', port=8000)

위는 오늘 풀었던 문제의 웹 코드이다.

 

코드를 읽어보면 admin함수 부분에서 URL에 대쉬이후에 admin을 적으면 권한에 상관없이 sessionid의 해시태그가 나오는 문제점이 있어 쿠키를 세션id로 설정해주면(로그인 함수 부분을 보면 pw == password이면 admin로그인 승인으로 되어 있음) 자동으로 admin으로 로그인 되었다.