add: writeup-ctf

2024-03-02 21:49:07 +01:00
parent ff520654f0
commit 095a13b2c9
1021 changed files with 9299 additions and 0 deletions
@@ -0,0 +1,132 @@
+---
+title: "Writeup - Valentine (HTB)"
+date: 2022-05-05
+slug: "writeup-valentine-htb"
+type: "writeup-ctf"
+--- 
+
+This is a writeup for the [Valentine](https://app.hackthebox.com/machines/Valentine) machine from the HackTheBox site.
+
+## Enumeration
+
+First, let's start with a scan of our target with the following command:
+
+
+```bash
+nmap -sV -T4 -Pn 10.10.10.79
+```
+Three TCP port are discovered:
+
+![](img/image-1.webp)
+
+- 22/tcp : SSH port (OpenSSH 5.9p1)
+- 80/tcp : HTTP (Apache 2.2.22)
+- 443/tcp : HTTPS (Apache 2.2.22)
+
+![](img/image-2.webp)
+
+## Exploit
+
+First, I start by scanning the site's folders.
+
+I quickly find the `/dev` folder where there are 2 files :
+
+
+```bash
+To do:
+
+1) Coffee.
+2) Research.
+3) Fix decoder/encoder before going live.
+4) Make sure encoding/decoding is only done client-side.
+5) Don't use the decoder/encoder until any of this is done.
+6) Find a better way to take notes.
+```
+
+```bash
+-----BEGIN RSA PRIVATE KEY-----
+Proc-Type: 4,ENCRYPTED
+DEK-Info: AES-128-CBC,AEB88C140F69BF2074788DE24AE48D46
+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-----END RSA PRIVATE KEY-----
+```
+This second file is very interesting, it's an RSA key that should allow me to connect in SSH. The only problem is that it is encrypted and requires a password. So I try to brute force the password. For that I start by extracting a hash with the following command:
+
+
+```bash
+ssh2john id_rsa > hash
+```
+Then I launch John with the rockyou dictionary.
+
+![](img/image-3.webp)
+
+Unfortunately without success. Let's look for something else, after performing a vulnerability scan with Nmap, I find that the machine is vulnerable to CVE-2014-0160. After some research I find this github [github](https://github.com/sensepost/heartbleed-poc).
+
+![](img/image-4.webp)
+
+After some executions I find a string in base64:
+
+
+```bash
+┌──(d3vyce㉿kali)-[~/Documents]
+└─$ echo "aGVhcnRibGVlZGJlbGlldmV0aGVoeXBlCg==" | base64 -d
+heartbleedbelievethehype
+```
+It could be a password, so I test to connect with :
+
+![](img/image-5.webp)
+
+I now have SSH access and can retrieve the first flag.
+
+{{< alert >}}
+While trying to connect via SSH I got the following error: `sign_and_send_pubkey: no mutual signature supported`. To solve the problem I had to add to the command: `PubkeyAcceptedKeyTypes=+ssh-rsa`.
+{{< /alert >}}
+
+## Privilege escalation
+
+At first I start by running the [linpeas.sh](https://linpeas.sh) script to find a vulnerability. I quickly find a tmux service executed by root.
+
+![](img/image-6.webp)
+
+After some research I find that it is possible to enter a tmux stream via the `-S` argument which allows to indicate a socket-path.
+
+
+```bash
+tmux -S /.devs/dev_sess
+```
+I now have a root shell and I can get the last flag.
+
+![](img/image-7.webp)
+
+## Recommendations
+
+To patch this host I think it would be necessary to perform a number of actions:
+
+- Do not leave large files accessible directly from a website
+- Update the machine to fix CVE-2014-0160
+- Do not create a tmux session as root