Dear LiveJournal, caries

It would appear that you are storing an md5 hash of each user’s password in your database. Although I certainly could be wrong, I have reason to believe this is your method (see below), and it worries me greatly. I am concerned that my password and the passwords of all other LiveJournal users are highly vulnerable to attack. In this day and age, this method is almost no different than simply storing my password in plaintext.

To reiterate what many of you probably know, the original purpose of storing an MD5 hash over plaintext is that the passwords would ideally be unrecoverable even in the event that an attacker was able to obtain a copy of your database. This security is needed because such attacks do happen successfully even to companies that take network security seriously.

With advances in hash-table attacks (eg: “Rainbow Crack“), it is conceivable that any attacker capable of obtaining your database would have no trouble whatsoever converting all of these hashes to their original passwords in a short amount of time with even very basic computing equipment.

I appreciate your efforts to not send passwords in cleartext even on non-encrypted connections. This is above and beyond the usual call of duty, however, the storage method is antiquated and no longer safe.

It would be rude for me to bring up the problem and just leave you hanging, so I will humbly make a recommendation: store the passwords using a salt that is randomly generated (by mt_rand(), not rand()) for each user, and then hashing the salt and password using a more secure method of hashing such as bcrypt. I will include references that explain the reasons for each of these choices.

LiveJournal has always been very proactive in adopting or even creating new technology to take care of serious issues like openness, scalability, and even security. I realize that many other large sites may be guilty of this oversight also, but that doesn’t make your users any safer. Please address this issue as soon as is healthily possible. I – and I’m sure, others – would be more than willing to provide more info if that would help you make the conversion even faster.

If I was wrong about how you are storing passwords, please correct me so that I can clear the air (and apologize profusely).

Thank you for your time,
– Sean Colombo

PS: Thanks for memcached, it makes running my own sites much more cost-effective.

EXTRA INFO:

• Everyone is doing it… but they’re doing it wrong.
• Since LJ uses PHP, please generate the random salts with mt_rand() instead of rand(). I don’t mean to patronize you if you already know about mt_rand, I’m just trying to cover all bases here.
• More info than you’d ever want to know about securely storing passwords
• A really solid implementation of using Rainbow Tables to crack md5 hashes: Ophcrack.
• For the curious: my indication that the passwords are stored as a simple md5-hash comes from the code used to encrypt the password before sending it to the LiveJournal login code. This is extremely nice that they do this, but its aim is to protect against sniffing out packets to find your password. At the same time, a site like LiveJournal has a nice juicy database full of millions of tasty passwords… enough to entice an attacker to steal the whole thing and steal millions of identities instead of victimizing individual users, thus creating a much bigger problem.

  LJ sends out a ‘challenge’ with the login form. This challenge (chal) is combined with your password (pass) as follows before being sent (in ‘res’) to LiveJournal:
  var res = MD5(chal + MD5(pass));
  What this implies is that LJ has an md5 hash of each user’s password, which they then combine with the challenge you send them and compare against your response. This is a good zero-knowledge proof that you know your password (or at least its md5 hash). This “extra security” while well-intentioned, actually means that an attacker could log into your LiveJournal account using your hash even before cracking it… but this is a very small problem since the main reason we care about the way a password is stored is that you probably also use your password for other (possibly sensitive) accounts (such as your online-banking/paypal/etc.).

UPDATE: I thought I’d wait to get some verification that I was right that they store the passwords like this before bugging LJ, but I’d want someone to report things like this to me ASAP if one of my sites had a problem… so I sent this along to them now (as a support ticket on LiveJournal). I’ll update if they get back to me.

UPDATE: Remembered LiveJournal is open source… started browsing the code. Found out it’s perl, not PHP (oops).

UPDATE: This keeps getting worse. It turns out they store the passwords as plaintext! see the comments below for more info.