Password Hashing: Do not use MD5

Impact

User passwords are stored in the database using the rather outdated and cryptographically insecure MD5 hash algorithm. Furthermore, the hashes are salted using the username instead of a random salt, causing hashes for users with the same username and password to collide which is problematic especially for popular users like the default admin user.

This essentially means that for an attacker, it might be feasible to reconstruct a user's password given access to these hashes.

Note that attackers needing access to the hashes means that they must gain access to the database in which these are stored first to be able to start cracking the passwords.

Patches

The problem is addressed in Opencast 8.1 which now uses the modern and much stronger bcrypt password hashing algorithm for storing passwords. Note, that old hashes remain MD5 until the password is updated.

For a list of users whose password hashes are stored using MD5, take a look at the /user-utils/users/md5.json REST endpoint.

Workarounds

There is no workaround.

References

• MD5 (Wikipedia)
• bcrypt (Wikipedia)
• How weak is MD5 as a password hashing function?

For more information

If you have any questions or comments about this advisory:

• Open an issue in opencast/opencast
• For security-relevant information, email us at security@opencast.org