danwalsh


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I need Guinea pigs...
danwalsh
REPOSTING WITH SOME FIXES

One  of the problems I face, is trying to convince people to use new security products.   They say, "Sure just don't break anything".  The problem is I need Guinea pigs to find out what I break.  In the case of confining the user, I have a problem.  I believe this can be a big security step forward, but how do I get people to use it, if it is not fully tested out?  How do I test it out without getting people to use it?

Now I have taken some involuntary test subjects like my wife, and set her up with a confined user account and worked with her to fix problems in xguest.  I have also taken the Jonas Salk approach and tested on my self.  I have been running as the staff_u user for the entire run of Rawhide since Fedora 8.

So I am now beginning to Beg co-workers to try it out.  As people start to install Fedora 9, I want them to try out confined users.  The simplest user for an engineer to try is staff_u with a transition to unconfined_t when you become root.

This is how I set this up.

First you need to modify the SELinux user record to allow it to reach the unconfined_r.  You also want to allow it to reach the system_r since you might be restarting services which need to run as system_r.  The command is a little ugly but follow along

# semanage user -m -R"staff_r unconfined_r system_r" staff_u
This tells the system to modify the staff_u user and allow it to reach the staff_r, unconfined_r and system_r roles.

Now we need to modify the login account to login as the staff_u SELinux user.

We can either change the default, so all users by default will login as the staff_u user.

# semanage login -m -s staff_u __default__

Or we can add a record just for my Linux user "dwalsh"

# semanage login -a -s staff_u -r s0-s0:c0.c1023 dwalsh

Finally I want to setup a sudo to allow me to transition from staff_t to unconfined_t when running commands using sudo.

Add a record like to following using visudo

dwalsh  ALL=(ALL) TYPE=unconfined_t ROLE=unconfined_r   ALL

Now logout and log back in and you should be running as staff_u:staff_r:staff_t,

Execute "sudo sh" and you should be running as staff_u:unconfined_r:unconfined_t.

One caveat for this environment is currently userhelper apps will not work (system-config-*) when executed from staff_t,  But you can run them from the sudo root account.

What does this buy you?  While running in staff_t you will not be allowed to run any setuid application that is not confined.  So if somehow you were tricked into running a setuid app on your machine to become root, it will fail.  You will automatically transition to nsplugin so  your firefox will have confinement.  The ONLY way to become root/unconfined_t is through sudo, which is a well studied application.  If you run attempt to run su, you will be denied.

So do I have any volunteers????

I am fixing a typo in the command above sorry about reposting.

Also if you want to reverse the changes listed above

You could execute

semanage login -d dwalsh

Will remove the record and put dwalsh back to the default.


# semanage login -m -s unconfined_u __default__


Would set the default logins to be unconfined_u (the default)

Will I be able to login as root from SSH?? Fedora by default doesn't come with "sudo" and "su" is denied so how do I get my root permissions?

I'll be more than happy to learn a little about SE-Linux :)

Fedora comes with sudoe

jds2001

2008-04-26 08:04 pm (UTC)

the default installation of Fedora *does* ship with sudo. However, it's not configured. Dan gave fairly specific instructions on how to configure it to work in this setup.

As someone who tests Fedora and lives on the bleeding edge, and really doesn't care if my machine works or not (very few folks can say that - obviously not my primary machine!) I'll probably set this up, even having no knowledge of SELinux to date (except how to turn it off :P). It will be a fun learning experience for me, and expect tons of questions at the Summit, Dan! :)

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