1. SimpleJs

题目链接：https://adworld.xctf.org.cn/challenges/details?hash=2e4acf37-f5e9-4c09-8842-9cbb4ce81a50_2

题解

一个找密码的问题，用Chrome打开题目页面直接右键查看源代码

function dechiffre(pass_enc){
        var pass = "70,65,85,88,32,80,65,83,83,87,79,82,68,32,72,65,72,65";
        var tab  = pass_enc.split(',');
                var tab2 = pass.split(',');var i,j,k,l=0,m,n,o,p = "";i = 0;j = tab.length;
                        k = j + (l) + (n=0);
                        n = tab2.length;
                        for(i = (o=0); i < (k = j = n); i++ ){o = tab[i-l];p += String.fromCharCode((o = tab2[i]));
                                if(i == 5)break;}
                        for(i = (o=0); i < (k = j = n); i++ ){
                        o = tab[i-l];
                                if(i > 5 && i < k-1)
                                        p += String.fromCharCode((o = tab2[i]));
                        }
        p += String.fromCharCode(tab2[17]);
        pass = p;return pass;
    }
    String["fromCharCode"](dechiffre("\x35\x35\x2c\x35\x36\x2c\x35\x34\x2c\x37\x39\x2c\x31\x31\x35\x2c\x36\x39\x2c\x31\x31\x34\x2c\x31\x31\x36\x2c\x31\x30\x37\x2c\x34\x39\x2c\x35\x30"));

    h = window.prompt('Enter password');
    alert( dechiffre(h) );

代码做了一些简单的混淆，简化下为

function dechiffre(pass_enc){
            var pass = "70,65,85,88,32,80,65,83,83,87,79,82,68,32,72,65,72,65";
            var tab2 = pass.split(',');
            var p = "";
            for(i = 0; i < tab2.length; i++ ){
                p += String.fromCharCode(tab2[i]);
                if(i == 5)break;
            }
            for(i = 0; i < tab2.length; i++ ){
                if(i > 5 && i < tab2.length-1)
                    p += String.fromCharCode( tab2[i]);
            }
            p += String.fromCharCode(tab2[17]);
            pass = p;
            return pass;
        }
        // 无用代码
        String["fromCharCode"](dechiffre("\x35\x35\x2c\x35\x36\x2c\x35\x34\x2c\x37\x39\x2c\x31\x31\x35\x2c\x36\x39\x2c\x31\x31\x34\x2c\x31\x31\x36\x2c\x31\x30\x37\x2c\x34\x39\x2c\x35\x30"));

        h = window.prompt('Enter password');
        alert( dechiffre(h) );

其实就是将"70,65,85,88,32,80,65,83,83,87,79,82,68,32,72,65,72,65"转换字符输出，所以不管你输入什么alert提示永远为FAUX PASSWORD HAHA。根据dechiffre逻辑这个函数功能大概是将密文转化为密码，根据源文件密文为：

\x35\x35\x2c\x35\x36\x2c\x35\x34\x2c\x37\x39\x2c\x31\x31\x35\x2c\x36\x39\x2c\x31\x31\x34\x2c\x31\x31\x36\x2c\x31\x30\x37\x2c\x34\x39\x2c\x35\x30

这是一个Base16编码的字符串，解开后为：786OsErtk12

Ps：Base16编码介绍：https://blog.csdn.net/z_Fuck/article/details/109702625