Automatically Expiring Passwords

Tags: usability, passwords, security

I do a little bit of work for a friend on the side every now and then. He has a small online store set up with a credit card processor to handle processing payments for his credit cards. Every so often if he hasn’t gotten orders in a few days, he gets a bit antsy and asks me to log in and check to be sure no orders have gotten through without him getting an alert. Dutifully, I do this, as it usually only takes me about 30 seconds to make sure everything is working – as it always is.

However, a few months ago I tried to log into his virtual terminal account, I was treated to a ominous warning, informing me that my password had "expired" and asking me to enter my password again, as well as selecting a new password. I had never seen that before, so I checked to make sure I was logging into the right site and had not somehow managed to fall for a phishing attack. Sure enough, my password had "expired."

Hmm. This is lame.

Maybe I’ll try to be smart with it and reenter the same password … nope. It’s smart. Can’t get around it. Because I had other things to do and this is already wasting my time, I concede defeat and create a new password for logging onto this site. Then, I do the unthinkable. Something that would make any security researcher and probably the "designer" of this system cringe in horror: I write the password down in a text file. Now anyone who manages to steal my laptop could potentially have access to this (of course, the file is encryped with the original password, though, so there is that).

Fast forward a few months. Another e-mail, another log into the virtual merchant terminal to check its status, another "password expired" message. Ah hah! Maybe I can set it back to what it used to be. No dice. It remembers all my old passwords.  Every 45 days, I have to make and learn a new password or this website, which is a monumental pain since I only usually look at it about that often. I make another new password, and update my file. More of my time wasted. After 90 days with this processor, I have now had three passwords.

Now, I know how to create an encrypted file. But think about the users. The people using this are not computer experts. They are small businesses. Let’s say Bob at Bob’s Sunglasses has this account. But Bob doesn’t want to spend all day logged into his merchant processor account. Bob has sunglasses to look at! So, he gives the login information to his secretary Susan and tells her to process and fill orders as they come in. After 45 days, Susan gets a warning message one morning about changing her password. After spending an hour on the phone with tech support, she is able to figure out how to change the password.

Then, she does exactly what I did: she writes it down. Only she writes it down on a yellow post-it note along with the user name and account number ("just in case," she says to herself) and sticks it right on the side of the monitor for everyone to see.

Automatically expiring passwords, from a security perspective, is an extremely bad idea because it encourages unsafe behavior with passwords. While theoretically it sounds like a great idea, it perversely encourages users to write passwords down – the last thing you want them to be doing – and just makes it all the more difficult for them to use your product. A better approach is to encourage or require users to have secure passwords in the first place, and to foster proper care for passwords.

Security on Shared Hosts

Tags: php, shared hosting, security, tmp

Shared hosts are a reality for many small businesses or businesses that aren’t oriented around moving massive amounts of data. This is a given – we can’t all afford racks full of dedicated servers. With that in mind, I would urge people to be more careful about what they do on shared hosting accounts. You should assume that anything you do is being watched.

Take, for example, the /tmp directory. I was doing some work for a friend this weekend whose account is housed on the servers of a certain very large hosting company. While tweaking some of his scripts, I noticed via phpinfo() that sessions were file-based and were being stored in /tmp. This made me curious as to whether any of that session data could possibly be available for public viewing.

My first move was to simply try FTP’ing up and CD’ing to /tmp directory. No go – they have the FTP accounts chrooted into a jail, so the obvious door is closed. However, the accounts have PHP installed, so I can do something like this in a PHP script:

<?php

system("ls -al /tmp");

?>

With this little bit of code, I can look into the tmp directory even if my FTP login is chrooted. Fortunately, sessions on this host are 600, so they’re not publically readable -  this was my primary concern and the reason I took some time to check this out. But people are putting lots of things into the tmp directory with the misguided idea that it is their private temporary file dump, including one idiot who put a month’s worth of PayPal transaction data into tmp and left it 644 so that it was publically viewable.

Now, I’m a nice guy and the only thing I’m going to do with this information is laugh at it. But keeping in mind how dirt cheap hosting accounts are, there’s not a high entry barrier for someone with fewer scruples.

The key thing to remember is that, if you need temporary file storage on a shared host, do it someplace less obvious, set the permissions so that only you can read/write to it (600), and clean up by deleting files as soon as you possibly can.