网鼎杯2020青龙组 web writeup
Posted W4nder
tags:
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上午压根没web,而且签到题有问题,又不能重新下发,愣是看着密码发呆emmm,然后下午才放web,而且一个队只能下发一个docker,就挺拖时间的,搞心态
AreUSerialz
源码
<?php
include("flag.php");
highlight_file(__FILE__);
class FileHandler {
protected $op;
protected $filename;
protected $content;
function __construct() {
$op = "1";
$filename = "/tmp/tmpfile";
$content = "Hello World!";
$this->process();
}
public function process() {
if($this->op == "1") {
$this->write();
} else if($this->op == "2") {
$res = $this->read();
$this->output($res);
} else {
$this->output("Bad Hacker!");
}
}
private function write() {
if(isset($this->filename) && isset($this->content)) {
if(strlen((string)$this->content) > 100) {
$this->output("Too long!");
die();
}
$res = file_put_contents($this->filename, $this->content);
if($res) $this->output("Successful!");
else $this->output("Failed!");
} else {
$this->output("Failed!");
}
}
private function read() {
$res = "";
if(isset($this->filename)) {
$res = file_get_contents($this->filename);
}
return $res;
}
private function output($s) {
echo "[Result]: <br>";
echo $s;
}
function __destruct() {
if($this->op === "2")
$this->op = "1";
$this->content = "";
$this->process();
}
}
function is_valid($s) {
for($i = 0; $i < strlen($s); $i++)
if(!(ord($s[$i]) >= 32 && ord($s[$i]) <= 125))
return false;
return true;
}
if(isset($_GET{‘str‘})) {
$str = (string)$_GET[‘str‘];
if(is_valid($str)) {
$obj = unserialize($str);
}
}
尝试写shell不得行,那就读文件吧
反序列化之前会做逐字判断,ascii必须>=32或<=125
由于这里是protect类型,需要加上%00进行标识
但是%会被过滤,就用十六进制 0和S,然后这里有个弱类型可以用int绕过
首先需要知道路径,可以查看:
/proc/self/cmdline
得到配置文件路径
/web/config/httpd.conf
O:11:"FileHandler":3:{S:5:"