I got it to work, but the solution is a bit complex, so bear with me.
What's happening
As it is, Internet Explorer gives lower level of trust to IFRAME pages (IE calls this "third-party" content). If the page inside the IFRAME doesn't have a Privacy Policy, its cookies are blocked (which is indicated by the eye icon in status bar, when you click on it, it shows you a list of blocked URLs).
(source: piskvor.org)
In this case, when cookies are blocked, session identifier is not sent, and the target script throws a 'session not found' error.
(I've tried setting the session identifier into the form and loading it from POST variables. This would have worked, but for political reasons I couldn't do that.)
It is possible to make the page inside the IFRAME more trusted: if the inner page sends a P3P header with a privacy policy that is acceptable to IE, the cookies will be accepted.
How to solve it
Create a p3p policy
A good starting point is the W3C tutorial. I've gone through it, downloaded the IBM Privacy Policy Editor and there I created a representation of the privacy policy and gave it a name to reference it by (here it was policy1
).
NOTE: at this point, you actually need to find out if your site has a privacy policy, and if not, create it - whether it collects user data, what kind of data, what it does with it, who has access to it, etc. You need to find this information and think about it. Just slapping together a few tags will not cut it. This step cannot be done purely in software, and may be highly political (e.g. "should we sell our click statistics?").
(e.g. "the site is operated by ACME Ltd., it uses anonymous per-session identifiers for its operation, collects user data only if explicitly permitted and only for the following purposes, the data is stored only as long as necessary, only our company has access to it, etc. etc.").
(When editing with this tool, it's possible to view errors/omissions in the policy. Also very useful is the tab "HTML Policy": at the bottom, it has a "Policy Evaluation" - a quick check if the policy will be blocked by IE's default settings)
The Editor exports to a .p3p file, which is an XML representation of the above policy. Also, it can export a "compact version" of this policy.
Link to the policy
Then a Policy Reference file (http://example.com/w3c/p3p.xml
) was needed (an index of privacy policies the site uses):
<META>
<POLICY-REFERENCES>
<POLICY-REF about="/w3c/example-com.p3p#policy1">
<INCLUDE>/</INCLUDE>
<COOKIE-INCLUDE/>
</POLICY-REF>
</POLICY-REFERENCES>
</META>
The <INCLUDE>
shows all URIs that will use this policy (in my case, the whole site). The policy file I've exported from the Editor was uploaded to http://example.com/w3c/example-com.p3p
Send the compact header with responses
I've set the webserver at example.com to send the compact header with responses, like this:
HTTP/1.1 200 OK
P3P: policyref="/w3c/p3p.xml", CP="IDC DSP COR IVAi IVDi OUR TST"
// ... other headers and content
policyref
is a relative URI to the Policy Reference file (which in turn references the privacy policies), CP
is the compact policy representation. Note that the combination of P3P headers in the example may not be applicable on your specific website; your P3P headers MUST truthfully represent your own privacy policy!
Profit!
In this configuration, the Evil Eye does not appear, the cookies are saved even in the IFRAME, and the application works.
Edit: What NOT to do, unless you like defending from lawsuits
Several people have suggested "just slap some tags into your P3P header, until the Evil Eye gives up".
The tags are not only a bunch of bits, they have real world meanings, and their use gives you real world responsibilities!
For example, pretending that you never collect user data might make the browser happy, but if you actually collect user data, the P3P is conflicting with reality. Plain and simple, you are purposefully lying to your users, and that might be criminal behavior in some countries. As in, "go to jail, do not collect $200".
A few examples (see p3pwriter for the full set of tags):
- NOI : "Web Site does not collected identified data." (as soon as there's any customization, a login, or any data collection (***** Analytics, anyone?), you must acknowledge it in your P3P)
- STP: Information is retained to meet the stated purpose. This requires information to be discarded at the earliest time possible. Sites MUST have a retention policy that establishes a destruction time table. The retention policy MUST be included in or linked from the site's human-readable privacy policy." (so if you send
STP
but don't have a retention policy, you may be committing fraud. How cool is that? Not at all.)
I'm not a lawyer, but I'm not willing to go to court to see if the P3P header is really legally binding or if you can promise your users anything without actually willing to honor your promises.
You should implement a session timeout of your own. Both options mentioned by others (session.gc_maxlifetime and session.cookie_lifetime) are not reliable. I'll explain the reasons for that.
First:
session.gc_maxlifetime
session.gc_maxlifetime specifies the number of seconds after which data will be seen as 'garbage' and cleaned up. Garbage collection occurs during session start.
But the garbage collector is only started with a probability of session.gc_probability divided by session.gc_divisor. And using the default values for those options (1 and 100 respectively), the chance is only at 1%.
Well, you could simply adjust these values so that the garbage collector is started more often. But when the garbage collector is started, it will check the validity for every registered session. And that is cost-intensive.
Furthermore, when using PHP's default session.save_handler files, the session data is stored in files in a path specified in session.save_path. With that session handler, the age of the session data is calculated on the file's last modification date and not the last access date:
Note: If you are using the default file-based session handler, your filesystem must keep track of access times (atime). Windows FAT does not so you will have to come up with another way to handle garbage collecting your session if you are stuck with a FAT filesystem or any other filesystem where atime tracking is not available. Since PHP 4.2.3 it has used mtime (modified date) instead of atime. So, you won't have problems with filesystems where atime tracking is not available.
So it additionally might occur that a session data file is deleted while the session itself is still considered as valid because the session data was not updated recently.
And second:
session.cookie_lifetime
session.cookie_lifetime specifies the lifetime of the cookie in seconds which is sent to the browser. […]
Yes, that's right. This only affects the cookie lifetime and the session itself may still be valid. But it's the server's task to invalidate a session, not the client. So this doesn't help anything. In fact, having session.cookie_lifetime set to 0
would make the session’s cookie a real session cookie that is only valid until the browser is closed.
Conclusion / best solution:
The best solution is to implement a session timeout of your own. Use a simple time stamp that denotes the time of the last activity (i.e. request) and update it with every request:
if (isset($_SESSION['LAST_ACTIVITY']) && (time() - $_SESSION['LAST_ACTIVITY'] > 1800)) {
// last request was more than 30 minutes ago
session_unset(); // unset $_SESSION variable for the run-time
session_destroy(); // destroy session data in storage
}
$_SESSION['LAST_ACTIVITY'] = time(); // update last activity time stamp
Updating the session data with every request also changes the session file's modification date so that the session is not removed by the garbage collector prematurely.
You can also use an additional time stamp to regenerate the session ID periodically to avoid attacks on sessions like session fixation:
if (!isset($_SESSION['CREATED'])) {
$_SESSION['CREATED'] = time();
} else if (time() - $_SESSION['CREATED'] > 1800) {
// session started more than 30 minutes ago
session_regenerate_id(true); // change session ID for the current session and invalidate old session ID
$_SESSION['CREATED'] = time(); // update creation time
}
Notes:
session.gc_maxlifetime
should be at least equal to the lifetime of this custom expiration handler (1800 in this example);
- if you want to expire the session after 30 minutes of activity instead of after 30 minutes since start, you'll also need to use
setcookie
with an expire of time()+60*30
to keep the session cookie active.
Best Answer
State management is a critical thing to master when coming to Web world from a desktop application perspective.
Session
is used to store per-user information for the current Web session on the server. It supports using a database server as the back-end store.Cookie
should be used to store per-user information for the current Web session or persistent information on the client, therefore client has control over the contents of a cookie.Cache
object is shared between users in a single application. Its primary purpose is to cache data from a data store and should not be used as a primary storage. It supports automatic invalidation features.Application
object is shared between users to store application-wide state and should be used accordingly.If your application is used by a number of unauthenticated users, I suggest you store the data in a cookie. If it requires authentication, you can either store the data in the DB manually or use ASP.NET profile management features.