php伪随机数

利用工具 php_mt_seed

// php 7.2
 
function white_list() {
 
    return mt_rand();
 
}
 
echo white_list(), "\n";
 
echo white_list(), "\n";
 
echo white_list(), "\n";

输入命令：

./php_mt_seed 1035656029

 
 
mt_srand(1810951568);//手工播种
 
echo mt_rand() . " ";
echo mt_rand() . " ";
echo mt_rand() . " ";

1.

opAvIkKEuk
#这不是抽奖程序的源代码！不许看！
header("Content-Type: text/html;charset=utf-8");
session_start();
if(!isset($_SESSION['seed'])){
$_SESSION['seed']=rand(0,999999999);
}
 
mt_srand($_SESSION['seed']);
$str_long1 = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$str='';
$len1=20;
for ( $i = 0; $i < $len1; $i++ ){
    $str.=substr($str_long1, mt_rand(0, strlen($str_long1) - 1), 1);       
}
$str_show = substr($str, 0, 10);
echo "
".$str_show."
";
 
 
if(isset($_POST['num'])){
    if($_POST['num']===$str){
        echo "
抽奖，就是那么枯燥且无味，给你flag{xxxxxxxxx}
";
    }
    else{
        echo "
没抽中哦，再试试吧
";
    }
}
show_source("check.php"); 

 反向解密出时间序列

$pass_now = "lNWTvHufgV";
$allowable_characters = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
$len = strlen($allowable_characters) - 1;
for($j = 0; $j < strlen($pass_now); $j++)
{
   for ($i = 0; $i < $len; $i++) {
       if($pass_now[$j] == $allowable_characters[$i])
       {
           echo "$i $i 0 61 ";
           break;
       }
   }
?>

.echo "$i $i 0 61 "; 这么构造是因为使用工具的时候若有多个参数，每四个一组， 前两个参数表示mt_rand第一次输出的区间，后两个参数表示mt_rand输出的区间 所以前两个就是都是$i后面两个就是$allowable_characters 的长度有关，这里长度为62，所以是0 61

 再用种子跑