Cross-domain validation in PHP

Question

I am currently working on a project that revolves around the following:

Page 1 ( domain1 ) redirecting to Page 2 ( domain2 ) redirecting to Page 3 ( domain2 )

I wanna make sure that the Page 2 contents is NOT shown unless the user is confirmed to have visited Page 1 first. For obvious reasons, I cannot use sessions and cookies, since domain1 and domain2 are two separate domains.

$_SERVER['HTTP_REFERER'] is a possible solution, but it can be modified or even stripped from the browser requests, so I have no guarantee I won't inadvertently block legitimate users by using it.

How would I go about doing it?

Answer 1

Yes. You cannot set cookie without direct request from browser.

You can pass a token while redirecting from http://page1 to http://page2/?token=hash_function ($salt,$user_ip).

More complex way is to generate token on domain with page1 and recheck it with direct request from page2 server to page1 server. This allows you to create "one-time" tokens and even user changed his ip during session (really rare case) - this redirect still be valid.