漏洞描述

开发中文件上传功能很常见,作为开发者,在完成功能的基础上我们一般也要做好安全防护。
文件处理一般包含两项功能,用户上传和展示文件,如上传头像。

文件上传攻击示例

upload.php

<"File is valid, and was successfully uploaded.\n";
} 
else {
 echo "File uploading failed.\n";
}
"htmlcode">
<form name="upload" action="upload1.php" method="POST" ENCTYPE="multipart/formdata">
Select the file to upload: <input type="file" name="userfile">
<input type="submit" name="upload" value="upload">
</form>

上述代码未经过任何验证,恶意用户可以上传php文件,代码如下

<"htmlcode">

<"image/gif") {//获取Http请求头信息中ContentType
 echo "Sorry, we only allow uploading GIF images";
 exit;
}
$uploaddir = 'uploads/';
$uploadfile = $uploaddir.basename($_FILES['userfile']['name']);
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)){
 echo "File is valid, and was successfully uploaded.\n";
} else {
 echo "File uploading failed.\n";
}
"userfile"; filename="shell.php"
Content-Type: image/gif

图片类型验证

该方法通过读取文件头中文件类型信息,获取文件类型

备注:如JPEG/JPG文件头标识为FFD8

你不知道的文件上传漏洞php代码分析

upload.php

<"Sorry, we only accept GIF and JPEG images\n";
 exit;
}
$uploaddir = 'uploads/';
$uploadfile = $uploaddir . basename($_FILES['userfile']['name']);
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)){
 echo "File is valid, and was successfully uploaded.\n";
} else {
 echo "File uploading failed.\n";
}
"text-align: center">你不知道的文件上传漏洞php代码分析

文件扩展名验证

 通过黑名单或白名单对文件扩展名进行过滤,如下代码

upload.php

<".php", ".phtml", ".php3", ".php4");
foreach ($blacklist as $item) {
if(preg_match("/$item\$/i", $_FILES['userfile']['name'])) {
 echo "We do not allow uploading PHP files\n";
 exit;
}
}
$uploaddir = 'uploads/';
$uploadfile = $uploaddir . basename($_FILES['userfile']['name']);
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)){
 echo "File is valid, and was successfully uploaded.\n";
} else {
 echo "File uploading failed.\n";
}
"htmlcode">
<"File is valid, and was successfully uploaded.\n";
} else {
  echo "File uploading failed.\n";
}
"htmlcode">
<"htmlcode">
<"upload_");
if (move_uploaded_file($_FILES['userfile']['tmp_name'], $uploadfile)) {
  $db =& DB::connect("mysql://username:password@localhost/database");
  if(PEAR::isError($db)) {
    unlink($uploadfile);
    die "Error connecting to the database";
  }
  $res = $db->query("INSERT INTO uploads SET name=",
      array(basename($uploadfile,basename($_FILES['userfile']['name']),$_FILES['userfile']['type']));
  if(PEAR::isError($res)) {
    unlink($uploadfile);
    die "Error saving data to the database. The file was not uploaded";
  }
  $id = $db->getOne('SELECT LAST_INSERT_ID() FROM uploads');
  echo "File is valid, and was successfully uploaded. You can view it <a href=\"view.php">here</a>\n";
} else {
  echo "File uploading failed.\n";
}
"htmlcode">
<"File id must be numeric");
}
$db =& DB::connect("mysql://root@localhost/db");
if(PEAR::isError($db)) {
  die("Error connecting to the database");
}
$file = $db->getRow('SELECT name, mime_type FROM uploads WHERE id="Error fetching data from the database");
}
if(is_null($file) || count($file)==0) {
  die("File not found");
}
header("Content-Type: " . $file['mime_type']);
readfile($uploaddir.$file['name']);
?>

上述代码文件名随机更改,文件被存储在web root之外,用户通过id在数据库中查询文件名,读取文件,可以有效的阻止上述漏洞发生

总结

通过以上示例分析,可总结一下几点

1.文件名修改,不使用用户上传的文件名

2.用户不可以通过上传路径直接访问文件

3.文件查看采用数据库获取文件名,从而在相应文件服务器读取文件

4.文件上传限制文件大小,个人上传数量等

 以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持。

风云阁资源网 Design By www.bgabc.com
广告合作:本站广告合作请联系QQ:858582 申请时备注:广告合作(否则不回)
免责声明:本站资源来自互联网收集,仅供用于学习和交流,请遵循相关法律法规,本站一切资源不代表本站立场,如有侵权、后门、不妥请联系本站删除!
风云阁资源网 Design By www.bgabc.com

稳了!魔兽国服回归的3条重磅消息!官宣时间再确认!

昨天有一位朋友在大神群里分享,自己亚服账号被封号之后居然弹出了国服的封号信息对话框。

这里面让他访问的是一个国服的战网网址,com.cn和后面的zh都非常明白地表明这就是国服战网。

而他在复制这个网址并且进行登录之后,确实是网易的网址,也就是我们熟悉的停服之后国服发布的暴雪游戏产品运营到期开放退款的说明。这是一件比较奇怪的事情,因为以前都没有出现这样的情况,现在突然提示跳转到国服战网的网址,是不是说明了简体中文客户端已经开始进行更新了呢?