Tuesday 19 January 2010

Disabling password expiry for specific accounts in msec

These notes are written specifically for Mandrake 10.1, however they can apply equally well to many other releases and distributions that use the msec security package.

The msec package is a powerful tool for establishing tight security controls on your linux machine. It is highly customisable and comes with six pre-defined security settings that can be further customised to your requirements. However, there is a catch. The most useful setting is the higher level of security. With this level, though, comes a vicious password expiry regime that includes the root password. Worse still, there is a bug that sets password expiry to be immediate under certain conditions. This affects all user account in addition to the root account.

The result is that your computer can be locked out to all users needing a reboot into stand-alone mode (failsafe) in order to unlock it. Not exactly the best scenario especially if your machine happens to be a server in a remote location!

There is a solution to this problem though. The file /etc/security/msec/level.local allows you to fine tune the security settings in the msec package. You can add


to /etc/security/msec/level.local to disable password expiry. In fact, you can call this multiple times
to add any number of accounts, so for example


will disable password expiry for the sales login. However, there is another gotcha. The chances are that if you found this page you already have a problem with password expiry. Setting the above will not unset an expiry that is permanently expiring an account. For that you need to log into the machine and su – to root. Then you meet your new best friend, the chage command. This changes the password aging setting for an existing entry. So, to make sales never expire, you simply run:
chage -M 99999 'sales'

This sets sales to expire in 99999 days' time. And with the no_password_aging_for('sales') setting above, this will not be reset next time msec runs.

Of course, you need to take careful note of which accounts you turn off password expiry and ensure that these passwords are changed at regular intervals when it suits you, otherwise you may be compromising the security on your machine, especially if it is online.

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