PHP：如何检测会话是否已自动过期？

When a session expiration time is defined, is it possible to call an event listener when it expires?

定义会话到期时间时,是否可以在事件监听器到期时调用它?

If it is not possible, is it possible to run a cron job to check if a session has expired?

如果不可能,是否可以运行cron作业来检查会话是否已过期?

NOTE: I'm interested in a server solution. I'm talking about the case there is a session expiration time defined, and the session finishes automatically because that period expired.

注意:我对服务器解决方案感兴趣。我在谈论定义了会话到期时间的情况,并且会话因为该期限到期而自动结束。

12 个解决方案

#1

is it possible to call an event listener when it expires?

可以在事件监听器到期时调用它吗?

The short answer is NO

最简洁的答案是不

There are a few oddities people tend to ignore about sessions. With the default handler, the session does not expire when gc_maxlifetime ends - this is just the time at which the data becomes eligible for automatic deletion. There is no action by the owner of the session which triggers the subsequent removal of the session - its a side effect of someone else's session.

人们往往会忽略一些关于会话的奇怪之处。使用默认处理程序时,会话在gc_maxlifetime结束时不会过期 - 这只是数据符合自动删除条件的时间。会话所有者没有动作会触发随后的会话删除 - 这是其他人会话的副作用。

When session_write_close() is called (either explicitly, or implicitly by the code ending), if the random number generator, tweaked by the relevant gc settings throws the right number then PHP will go looking for data past its TTL and remove it. If you want to trigger an action at this point, then you need to break the default handler and apply your own. That means you not only have to provide a mechanism for identifying and removing sessions but also a way of deciding whether your handler should kick in and how many sessions it should delete - you don't want a runaway process killing your server.

当调用session_write_close()时(显式或隐式地通过代码结束),如果随机数生成器(通过相关gc设置调整)会抛出正确的数字,那么PHP将继续寻找超过其TTL的数据并将其删除。如果您想在此时触发操作,则需要中断默认处理程序并应用自己的操作。这意味着您不仅需要提供一种识别和删除会话的机制,还需要一种方法来决定您的处理程序是否应该启动以及它应该删除多少个会话 - 您不希望失控的进程杀死您的服务器。

In Ubuntu, session.gc_probability = 0, and it is a cron job which carries out the function of removing stale data files.

在Ubuntu中,session.gc_probability = 0,它是一个执行删除陈旧数据文件功能的cron作业。

A very important piece of information missing from your question is the reason for deleting the session.

您的问题中缺少的一条非常重要的信息是删除会话的原因。

If you want to prevent sensitive data from persisting on the filesystem, then a better solution is to encrypt the data using a key stored (only) in another client side cookie. That way you completely eliminate the storage of unprotected data on your server. (note that suhosin's encrypted sessions use a key derived from data about the client and a static key stored on the same host - this is significantly less secure than a randomly generated key). Here's one I prepared earlier.

如果要防止敏感数据在文件系统上持久存在,那么更好的解决方案是使用另一个客户端cookie中存储的密钥(仅)来加密数据。这样您就可以完全消除服务器上未受保护数据的存储。 (请注意,suhosin的加密会话使用从客户端数据派生的密钥和存储在同一主机上的静态密钥 - 这比随机生成的密钥安全性低得多)。这是我之前准备的。

If you merely want to prevent access after the gc_maxlifetime has expired, you should consider a custom session handler which treats a stale session as missing. i.e. it doesn't really logout at expiry, but any subsequent requests can no longer be associated with the session. The security layer in the Stackable session handler examples implements such a control.

如果您只想在gc_maxlifetime过期后阻止访问,则应考虑将自定义会话处理程序视为缺失的自定义会话处理程序。即它在到期时并未真正注销,但任何后续请求都不能再与会话相关联。 Stackable会话处理程序示例中的安全层实现了这样的控制。

OTOH if you want to use data from within the session in your event listener, then that's a different story - you certainly won't be able to use either Suhosin's or my encryption for the data. But a further complication is that the (default) format for the data is different from that used elsewhere. You need to use session_encode() and session_decode(). The former will only read data from the $_SESSION array so eavesdropping on sessions requires some careful subversion of session_id() and session_start(). session_decode() however will happily convert anything you throw at it.

OTOH如果你想在事件监听器中使用会话中的数据,那么这是一个不同的故事 - 你肯定无法使用Suhosin或我的加密数据。但更复杂的是,数据的(默认)格式与其他地方使用的格式不同。您需要使用session_encode()和session_decode()。前者只会从$ _SESSION数组中读取数据,因此对会话的窃听需要对session_id()和session_start()进行一些小心的颠覆。然而,session_decode()会愉快地转换你抛出的任何东西。

In recent versions of PHP you can specify a different function pair to use for serialization/deserialization.

在PHP的最新版本中,您可以指定用于序列化/反序列化的不同函数对。

It is vitally important to consider the potential impact of __wakeup() methods when considering a session garbage collector which is going to read the data in the session files. Related to this is a requirement that the process which handles such garbage collection runs under the same uid as the original PHP process which created the session data (otherwise you have a privilege escalation backdoor). But if the session storage substrate is file-based then that would need to be the case anyway.

在考虑将要读取会话文件中的数据的会话垃圾收集器时,考虑__wakeup()方法的潜在影响至关重要。与此相关的是要求处理此类垃圾收集的进程在与创建会话数据的原始PHP进程相同的uid下运行(否则您具有权限提升后门)。但是,如果会话存储基板是基于文件的,那么无论如何都需要这样。

There are implementations of session data deserializer written in languages other than PHP which would provide protection against __wakeup() attacks (try Google) although that might be overkill to solve the problem and they are probably not being actively maintained. If this is a concern then a more appropriate solution might be to use the WDDX (xml) serializer and use a conventional XML parser to read the data back in your GC engine.

会话数据解串器的实现是用PHP以外的语言编写的,可以防止__wakeup()攻击(试试谷歌),虽然这可能有点过头来解决问题并且它们可能没有被主动维护。如果这是一个问题,那么更合适的解决方案可能是使用WDDX(xml)序列化程序并使用传统的XML解析器来读取GC引擎中的数据。

If you are using the native handler for normal reading and writing of the data but want to implement your own garbage collector then you're going to need code to map the session_id to a file path. If you follow the link I gave to the PHP classes above, you'll see pure PHP implementation of several session handlers, including ones which are compatible with the native handler.

如果您使用本机处理程序来正常读取和写入数据但想要实现自己的垃圾收集器,那么您将需要代码将session_id映射到文件路径。如果您按照我给上面的PHP类的链接,您将看到几个会话处理程序的纯PHP实现,包括与本机处理程序兼容的那些。

But I would strongly encourage you to exhaust every other avenue for solving whatever the underlying problem is before choosing to read back session data at the time of deletion.

但是我强烈建议你在选择在删除时回读会话数据之前用尽所有其他途径解决任何潜在问题。

12 个解决方案

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