PHP可预测的伪随机数 ：[GWCTF 2019]枯燥的抽奖

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<?php
$allowable_characters = 'abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ';
$len = strlen($allowable_characters) - 1;
$pass = "rz51neG83x";
for ($i = 0; $i < strlen($pass); $i++) {
    $number = strpos($allowable_characters, $pass[$i]);
    echo "$number $number 0 $len  ";
}
echo "n";
?>

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str1='abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ'
str2='c3wBAyqpZM'
str3 = str1[::-1]
length = len(str2)
res=''
for i in range(len(str2)):  
    for j in range(len(str1)):
        if str2[i] == str1[j]:
            res+=str(j)+' '+str(j)+' '+'0'+' '+str(len(str1)-1)+' '
            break
print(res)

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17 17 0 61 25 25 0 61 31 31 0 61 27 27 0 61 13 13 0 61 4 4 0 61 42 42 0 61 34 34 0 61 29 29 0 61 23 23 0 61 

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/php_mt_seed-main/php_mt_seed 17 17 0 61 25 25 0 61 31 31 0 61 27 27 0 61 13 13 0 61 4 4 0 61 42 42 0 61 34 34 0 61 29 29 0 61 23 23 0 61

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<?php
mt_srand(811224182);
$str_long1 = "abcdefghijklmnopqrstuvwxyz0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZ";
$str='';
$len1=20;
for ( $i = 0; $i < $len1; $i++ ){
    $str.=substr($str_long1, mt_rand(0, strlen($str_long1) - 1), 1);       
}
echo "<p id='p1'>".$str."</p>";
?> 

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<p id='p1'>rz51neG83xWSFre0enNc</p>