Test Day:2009-10-20 SELinux Confined Users

Confined Users Test Day

• Devel contact: dwalsh, mgrepl
• QE contact: mmalik, ebenes
• IRC channel: #fedora-test-day on irc.freenode.net

What to Test?

Today's Fedora Test Day will focus on SELinux Confined Users - users which are assigned to a SELinux role and where the SELinux policy controls what the user can do/access on the system. Current confined user types with their purpose of use are:

• guest_u – Terminal login, nosetuid, nonetwork, noxwindows, noexec in home directory.
• xguest_u – X Windows login and terminal login, nosetuid, nonetwork, noexec in home directory.
• user_u – X Windows login and terminal login, nosetuid, noexec in home directory.
• staff_u – X Windows login and terminal login, nosetuid except sudo.
• kiosk user - X Windows login and terminal login, nosetuid, nonetwork, noexec in home directory. NO password required. Home directory and /tmp get destroyed on logout.
• confined administrator - able to manage only a predefined set of services

The purpose of test day is to test these SELinux users on your desktop and in specific cases. So for example like xguest_u, user_u or staff_u try to login to X Windows.

What's Needed to Be Able to Test

You will need a fully updated Fedora 12 / Rawhide machine. Check if any of your repository files contains following lines or create a new repository file located in /etc/yum.repos.d/ with following content:

[rawhide]
name=Fedora - Rawhide - Developmental packages for the next Fedora release
failovermethod=priority
#baseurl=http://download.fedoraproject.org/pub/fedora/linux/development/$basearch/os/
mirrorlist=https://mirrors.fedoraproject.org/metalink?repo=rawhide&arch=$basearch
enabled=1
gpgcheck=0
gpgkey=file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-test-$basearch
file:///etc/pki/rpm-gpg/RPM-GPG-KEY-fedora-$basearch

You will need following packages installed on the machine. Please run yum install PACKAGE as root to install them and check that their versions match:

• selinux-policy-targeted-3.6.32-24.fc12
• policycoreutils-gui-2.0.74-4.fc12
• setroubleshoot-2.2.37-1.fc12
• audit-2.0.1-1.fc12
• xguest-1.0.7-7.fc12

As root run following commands to be able to record and see possible AVCs:

service auditd start
service messagebus start
service restorecond start
setenforce 1
tail -f /var/log/audit/audit.log

How to Test

The main goal is to test whether chosen confined user is able to do things which are allowed considering his/her SELinux role. And whether chosen confined user is not able to do things which are not allowed considering his/her role. For example if you log in as xguest_u and try to run ping or sudo in your favourite terminal you won't be able to run it. But if you won't be able to run Firefox then probably this is a bug.

How to Report Problems

Following steps in problem reporting are encouraged:

• If you encounter problems (e.g. appl. A did not start, appl. B failed to do what you wanted, appl. C works only partially) switch to permissive mode (setenforce 0) and repeat your action. Do not forget to switch back to enforcing mode (setenforce 1) before next testing. Root shell is needed.
• Look at the end of /var/log/audit/audit.log and check if new AVC messages appeared. These messages should start with type=AVC. The tail command which is mentioned above provides this information. Root shell is needed.
• Paste the AVC message to IRC channel with a short description what you did and what happened or did not happen.
• Communicate with others on IRC channel to find out if they encountered the same problem.
• Look at the end of /var/log/messages and search for messages containing sealert. Run sealert with parameters as advised. Root shell is needed.
• File a bug in Red Hat Bugzilla (Classification: Fedora, Product: Fedora, Version: rawhide, Component: selinux-policy). Do not forget to supply the description of actions you did, the AVC message and the full output of sealert.

Test Cases

Here you can find a few test cases. Please run as many of them as possible. Below each test case you can see a table, where you should write your results. Please add a line with your username and list of tests you ran/skipped into the table. The table could look this way:

User	Passed	Failed	Skipped	References
User:mmalik	G.1 G.2	B.1 B.2 B.3	G.3 G.4

guest_u

User capabilities
Terminal login, nosetuid, nonetwork, noxwindows, noexec in home directory

As root set up a server only machine, with Apache service (yum install httpd). Configure Apache in such a way that user home directories are accessible. Make sure Apache service is running (service httpd start). Add an user which can log in as guest_u (useradd -Z guest_u USERNAME). Create a directory named /secrets. Install MySQL (yum install mysql-server). Make sure MySQL service is running (service mysqld start) and the database is world readable.

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory.
  2. scp files to home directory and public_html directory.
  3. Copy files to public_html directory.
  4. Verify that the content is viewable via Apache.

• Bad Test - try to do evil
  1. Try to ping off the machine.
  2. Try any network protocol, try to get off the machine (ssh, sendmail, rsh, telnet etc.)
  3. Copy an executable into home directory and try to execute it.
  4. Try to read a file in the /secrets directory.
  5. Try to read the MySQL database (mysqlshow).

User	Passed	Failed	Skipped	References

xguest_u

User capabilities
X Windows login and terminal login, nosetuid, nonetwork, noexec in home directory

As root set up a client machine, with network access. Add an user which can log in as xguest_u (useradd -Z xguest_u USERNAME). Create a directory named /secrets. Install MySQL (yum install mysql-server). Make sure MySQL service is running (service mysqld start) and the database is world readable.

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory.
  2. Verify Firefox works and can access the network. Try to load several sites like http://www.ford.com to verify that flash works.
  3. Plug in USB disk and make sure xguest_u user can read/write the disk.
  4. Plug in USB camera and make sure it works.
  5. Plug in other USB devices.
  6. Verify Network Manager works.
  7. Verify printing from Firefox and from the desktop works.

• Bad Test - try to do evil
  1. Try to ping off the machine.
  2. Try any network protocol, try to get off the machine (ssh, sendmail, rsh, telnet etc.)
  3. Copy an executable into home directory and try to execute it.
  4. Try to read a file in the /secrets directory.
  5. Try to read the MySQL database (mysqlshow).

User	Passed	Failed	Skipped	References

user_u

User capabilities
X Windows login and terminal login, nosetuid, noexec in home directory

As root set up a client machine, with network access. Add an user which can log in as user_u (useradd -Z user_u USERNAME). Create a directory named /secrets. Install MySQL (yum install mysql-server). Make sure MySQL service is running (service mysqld start) and the database is world readable.

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory
  2. Verify Firefox works and can access the network. Try to load several sites like http://www.ford.com to verify flash works.
  3. Verify other network protocols work (aol, ssh, mail etc.)
  4. Plug in USB disk and make sure user_u user can read/write disk.
  5. Plug in USB camera and make sure it works.
  6. Plug in other USB devices.
  7. Verify Network Manager works.
  8. Verify printing from Firefox and from the desktop works.

• Bad Test - try to do evil
  1. Try to ping off the machine.
  2. Try to break into the root account via su, sudo.
  3. Copy an executable into home directory and try to execute it.
  4. Try to read a file in the /secrets directory.
  5. Try to read the MySQL database (mysqlshow).

User	Passed	Failed	Skipped	References

staff_u

User capabilities
X Windows login and terminal login, nosetuid except sudo

As root set up a client machine, with network access. Add an user which can log in as staff_u (useradd -Z staff_u USERNAME). Create a directory named /secrets. Install MySQL (yum install mysql-server). Make sure MySQL service is running (service mysqld start) and the database is world readable.

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory.
  2. Verify Firefox works and can access the network. Try to load several sites like http://www.ford.com to verify flash works.
  3. Verify other network protocols work (aol, ssh, mail etc.)
  4. Plug in USB disk and make sure staff_u user can read/write disk.
  5. Plug in USB camera and make sure it works.
  6. Plug in other USB devices.
  7. Verify Network Manager works.
  8. Verify printing from Firefox and from the desktop works.
  9. Try to ping off the machine.
  10. Copy an executable into home directory and try to execute it.
  11. Set up sudo and SELinux to allow staff_t to become unconfined_t via sudo.

• Bad Test - try to do evil
  1. Try to break into the root account via sudo.
  2. Try to read a file in the /secrets directory.
  3. Try to read the MySQL database (mysqlshow).

User	Passed	Failed	Skipped	References

Kiosk user

User capabilities
X Windows login and terminal login, nosetuid, nonetwork, noexec in home directory. NO password required. Home directory and /tmp get destroyed on logout.

As root set up a client machine, with network access. Make sure xguest package is installed (yum install xguest).

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory.
  2. Verify Firefox works and can access the network. Try to load several sites like http://www.ford.com to verify flash works.
  3. Plug in USB disk and make sure the kiosk user can read/write the disk.
  4. Plug in USB camera and make sure it works.
  5. Plug in other USB devices.
  6. Verify that Network Manager works.
  7. Verify printing from Firefox and from the desktop works.
  8. Logout and login to verify that home directory disappeared.
  9. Verify that password is not required.

• Bad Test - try to do evil
  1. Try to ping off the machine.
  2. Try any network protocol, try to get off the machine (ssh, sendmail, telnet, rsh etc.)
  3. Copy an executable into home directory and try to execute it.
  4. Try to read a file in the /secrets directory.
  5. Try to read the MySQL database (mysqlshow).
  6. Verify that you can not ssh into the machine as xguest_u.

User	Passed	Failed	Skipped	References

Confined administrator

User capabilities
Administrator that can manage MySQL and Apache

As root set up a client machine, with network access. Build policy for web_db_admin_t. Add an user which can log in as staff_u (useradd -Z staff_u USERNAME). Set up a transition from staff_t to web_db_admin_t. Set up sudo to make this happen automatically. Create a directory named /secrets and install MySQL (yum install mysql-server). Make sure MySQL is running (service mysqld start) and the database is world readable.

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory.
  2. Verify Firefox works and can access the network. Try to load several sites like http://www.ford.com to verify flash works.
  3. Verify other network protocols work (aol, ssh, mail etc.)
  4. Plug in USB disk and make sure the confined administrator can read/write the disk.
  5. Plug in USB camera and make sure it works.
  6. Plug in other USB devices.
  7. Verify Network Manager works.
  8. Verify printing from Firefox and from the desktop works.
  9. Try to ping off the machine.
  10. Copy an executable into home directory and try to execute it.
  11. Set up sudo and SELinux to allow staff_t to become unconfined_t via sudo.
  12. Execute sudo sh and make sure you end up as web_db_adm_t.
  13. Try to edit /var/www/html directory and some of the MySQL directories.
  14. Try to start/stop MySQL and Apache.

• Bad Test - try to do evil
  1. Try to break into the root account via su.
  2. Try to read a file in the /secrets directory.
  3. Try to read the MySQL database (mysqlshow).
  4. As web_db_adm_t try to add an user, modify files in /usr/share.

User	Passed	Failed	Skipped	References

Guest user that can send an email

As root set up a server machine, with network access. Build policy for sendmail_user_t. Add an user which can log in as sendmail_user_u (useradd -Z sendmail_user_u USERNAME).

Log in to the machine and try the following:

• Good Test - try to behave correctly
  1. Edit files in home directory.
  2. Verify you can send a mail as this user.

• Bad Test - try to do evil
  1. Try to break into the root account via sudo.
  2. Try to read a file in the /secrets directory.
  3. Try to read the MySQL database (mysqlshow).

User	Passed	Failed	Skipped	References

Links

1. http://docs.fedoraproject.org/selinux-user-guide/f10/en-US/sect-Security-Enhanced_Linux-Targeted_Policy-Confined_and_Unconfined_Users.html
2. http://magazine.redhat.com/2008/07/02/writing-policy-for-confined-selinux-users/
3. http://www.linuxtopia.org/online_books/fedora_selinux_guides/fedora_10_selinux_user_guide/fedora_10_selinux_sect-Security-Enhanced_Linux-Targeted_Policy-Confined_and_Unconfined_Users.html
4. http://selinux-mac.blogspot.com/2009/06/selinux-lockdown-part-one-confined.html