Mac Geekery

If you can drop to SUM then you can, with some effort, reset passwords and do bad, bad, evil things. If you trust that the one file that will never go bad on your disk is your /etc/passwd file, then you can tell the system to require the root password to enter SUM.

This does not work in Tiger or later. We talk about that in another article.

Even if you have set the password for root before, you need to set the password for root using the below method before doing this.

Set the root password in /etc/passwd

By default, all password changes affect the NetInfo database and not the system flat files. When booting to SUM the NetInfo database is inaccessible, so the system looks for the data it needs in the flat files. We need to change the password there. Fortunately, the Mac OS X version of passwd has handlers for changing the password on all kinds of directory systems (manpage is the second one listed). Using this, we can change the version in the /etc/passwd file so that SUM can use it.

$ sudo passwd -i file root
Password:
Changing password for root.
New password:
Retype new password:

You cannot use an /etc/shadow file with this method. That leaves the password at a maximum of 8 characters and opens it to attack. The good news is this is separate from the “real” root account; as long as you don’t have “BSD” checked in Directory Access as an authentication source then this password will not grant you anything within the OS itself once it enters multi-user mode.

Update /etc/ttys

On or about line 16 of /etc/ttys you will find the following line:

console "/System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow" vt100 on secure onoption="/usr/libexec/getty std.9600"

Change the word secure to insecure so that you have:

console "/System/Library/CoreServices/loginwindow.app/Contents/MacOS/loginwindow" vt100 on insecure onoption="/usr/libexec/getty std.9600"

You absolutely must ensure this remains one line.

Reboot into SUM and observe:

Root device is mounted read-only
If you want to make modifications to files
run '/sbin/fsck -y' first and then '/sbin/mount -uw /'
Enter root password or ^D to go multi-user
Password:

Mac OS X Tiger for Unix Geeks author: Brian Jepson,Ernest Rothman asin: 0596009127