How should I store a user's LDAP password in a cookie?

Question

So I have this black box authentication method, handed down to me from the accounts people, which basically amounts to ldap_bind($connection, $username, $password). But of course, I want my users to be able to log in for, say, 30 days at a time.

The naive but insecure way to handle this is to store the username and password in plaintext cookies, then validate these using my black box every time the user visits.

The way that usually works but doesn't because of my black box is to store the user's password in the database (or store it hashed?), and store the hashed version in the cookie, and then compare the values. This doesn't work here since my black box demands the actual password, not a hashed password.

My current thought is some kind of encryption (as opposed to hashing). But since this is obviously a common problem, I thought I'd best ask around first to see if there's a better solution lying around, or if not, what you would suggest for the encryption/decryption method.

Answer 1

This will not really answer your question, but you should NOT store your users passwords, not even encrypted.

If you really really have to do it, and the users understand that you are doing it. then store the password in a database of your application (encrypted, of course) and then send the user a cookie with a hash. When the user wants to login, compare the hash to what you stored and only then send the unencrypted password to the ldap. Never send the password (not even encrypted) to the user's machine.

Again, this is a very bad practice. if the ldap does not allow you store sessions/passwords then there is probably a good reason for this.