I'd use this technique:

  1. User requests that link be generated
  2. A random string (such as 1234567890abcdef) is generated and stored with its time of creation. A database is the logical tool to use for this storage.
  3. The link is generated using that random string, probably in the query string. e.g. http://example.com/foo.cgi?user=dorward;token=1234567890abcdef
  4. Link is emailed to user

Then, when the link is activated, the CGI script would look up the string (I'd add a WHERE clause in the SQL query to say "where time created is greater then now - 24 hours"). If its the query returns a result, then the link is OK, otherwise the user gets an "invalid or expired link" message that suggests they check they copied it correctly (watch for word wrap) and offers them a chance to generate a new one.

A regular process (probably triggered by cron) would then delete old entries from the database.

This is the type of thing that would be used for mailing list conformation emails. I wrote something along those lines for a "Forgotten your password" section of a website.

The technique generates randomish tokens to identify users, but that is about as similar as it gets to sessions.

In reply to Re: Ideas for implementing download links that expire, via e-mails by dorward
in thread Ideas for implementing download links that expire, via e-mails by ghenry

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