防止下载URL共享 [英] Prevent download URLs from being shared

问题描述

当我向用户提供下载内容时，我不希望他们能够复制URL并与他人共享.更进一步:我只愿放弃一次下载.如果他们第二次访问该URL，我想抛出404.

When I offer a download to a user, I don't want them to be able to copy the URL and share it with others. To go even further: I would like to give out the download only once. If they access the URL a second time, I'd like to throw a 404.

如何防止用户第二次访问下载URL，并且此方法是充分的证据.

How can I prevent a user from accessing the download URL a second time and is this method full proof.

我目前按以下方式提供文件:

I currently serve my file as follows:

header("Content-type: application/pdf");

// Set the name of the downloaded file here:
header("Content-Disposition: attachment;filename='example.pdf'"); 

 // Get the contents of the original file:
echo file_get_contents('example.pdf');

我还向我的mysql数据库添加了一个表

I've also added a table to my mysql database

+----+------+-------+------+
| downloads                |
+----+------+-------+------+
| id | file | token | flag |
+----+------+-------+------+

推荐答案

您将需要使用重定向到文件的下载脚本.在重定向到文件之前，脚本将需要通过唯一令牌(存储在数据库中)来验证url.该脚本可以记录已进行的下载并在数据库中设置一个标志.检查该标志以防止将来下载.

You would need to use a download script which redirects to the file. The script would need to verify the url via a unique token (stored in a database) before redirecting to the file. The script could record a download has been made and set a flag in the database. Check the flag to prevent future downloads.

编辑:这是一个示例(带有伪代码):

EDIT: Here's an Example (with pseudocode):

if( isset($_GET["token"]) && !empty($_GET["token"]) )
{
    //verify $_GET["token"] matches a token in the db

    //verify that the download flag has not been set

    header("Content-type: application/pdf");

    // Set the name of the downloaded file here:
    header("Content-Disposition: attachment;filename='example.pdf'"); 

    //set the downloaded flag in the database so that this file can't be downloaded again

     // Get the contents of the original file:
    echo file_get_contents('example.pdf');
}
else
    header("HTTP/1.0 404 Not Found");

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