• 进去什么也不给
• 搜索目录
• 发现index.php
• 最后输入了半天
• 发现/Challenges/index.php 返回头有一个Location: ./test.php
• 访问发现返回头有hint: ip,Large internal network，猜测是192.168.0.0 127.16.0.0 10.0.0.0
• 测试发现是X-Forwoared-For: 10.0.0.0
• 返回头得到一个./m4nage.php
• 输入，返回一个show me your key。 在请求头里面加入key或在post里面加入key
• 测试为post里面key=1得到一个key 的计算要求

key is not right,md5(key)==="1b4167610ba3f2ac426a68488dbd89be",and the key is ichunqiu***,the * is in [a-z0-9]

用下面代码计算

import hashlib
test = '1b4167610ba3f2ac426a68488dbd89be'
chars = "abcdefghijklmnopqrstuvwxyz0123456789"
def md5(s):
    return hashlib.md5(s).hexdigest()
    

for i in chars:
    for j in chars:
        for k in chars:
            key = 'ichunqiu'+i+j+k
            if(test==md5(key)):
                print key
                print md5(key)

• 得到key=ichunqiu105
• 传输过去。得到一个目录xx00xxoo.php
• 访问返回

source code is in the x0.txt.Can you guess the key
the authcode(flag) is a475hhEdVlz4CJidKqp/Jm+de15hbsgh9UcBuE8YKskZInZ77paXB0cC8srA1kudQngJMo/OAuWOalFKh+TD8rk9aDuy+h0

-接着访问得到一个代码

function authcode($string, $operation = 'DECODE', $key = '', $expiry = 0) {
    $ckey_length = 4;

    $key = md5($key ? $key : UC_KEY);
    $keya = md5(substr($key, 0, 16));
    $keyb = md5(substr($key, 16, 16));
    $keyc = $ckey_length ? ($operation == 'DECODE' ? substr($string, 0, $ckey_length) : substr(md5(microtime()), -$ckey_length)) : '';

    $cryptkey = $keya . md5($keya . $keyc);
    $key_length = strlen($cryptkey);

    $string = $operation == 'DECODE' ? base64_decode(substr($string, $ckey_length)) : sprintf('%010d', $expiry ? $expiry + time() : 0) . substr(md5($string . $keyb), 0, 16) . $string;
    $string_length = strlen($string);

    $result = '';
    $box = range(0, 255);

    $rndkey = array();
    for ($i = 0; $i <= 255; $i++) {
        $rndkey[$i] = ord($cryptkey[$i % $key_length]);
    }

    for ($j = $i = 0; $i < 256; $i++) {
        $j = ($j + $box[$i] + $rndkey[$i]) % 256;
        $tmp = $box[$i];
        $box[$i] = $box[$j];
        $box[$j] = $tmp;
    }

    for ($a = $j = $i = 0; $i < $string_length; $i++) {
        $a = ($a + 1) % 256;
        $j = ($j + $box[$a]) % 256;
        $tmp = $box[$a];
        $box[$a] = $box[$j];
        $box[$j] = $tmp;
        $result .= chr(ord($string[$i]) ^ ($box[($box[$a] + $box[$j]) % 256]));
    }

    if ($operation == 'DECODE') {
        if ((substr($result, 0, 10) == 0 || substr($result, 0, 10) - time() > 0) && substr($result, 10, 16) == substr(md5(substr($result, 26) . $keyb), 0, 16)) {
            return substr($result, 26);
        } else {
            return '';
        }
    } else {
        return $keyc . str_replace('=', '', base64_encode($result));
    }

}

• 看似复杂，其实直接echo authcode('a475hhEdVlz4CJidKqp/Jm+de15hbsgh9UcBuE8YKskZInZ77paXB0cC8srA1kudQngJMo/OAuWOalFKh+TD8rk9aDuy+h0',$operation = 'DECODE', $key = 'ichunqiu105', $expiry = 0)就行。