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SUSE Linux Enterprise Desktop Deployment Guide
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42.3 Getting Started with Profiling Applications

Prepare a successful deployment of Novell AppArmor on your system by carefully considering the following items:

  1. Determine the applications to profile. Read more on this in Section 42.3.1, Choosing the Applications to Profile.

  2. Build the needed profiles as roughly outlined in Section 42.3.2, Building and Modifying Profiles. Check the results and adjust the profiles when necessary.

  3. Keep track of what is happening on your system by running AppArmor reports and dealing with security events. Refer to Section 42.3.3, Configuring Novell AppArmor Event Notification and Reports.

  4. Update your profiles whenever your environment changes or you need to react to security events logged by AppArmor's reporting tool. Refer to Section 42.3.4, Updating Your Profiles.

42.3.1 Choosing the Applications to Profile

You only need to protect the programs that are exposed to attacks in your particular setup, so only use profiles for those applications you really run. Use the following list to determine the most likely candidates:

Network Agents

Programs (servers and clients) have open network ports and network agents are server programs that respond to those network ports. User clients, such as mail clients and Web browsers, also have open network ports and mediate privilege. Any attack on a user's Web browser or e-mail client allows the attacker to steal private data from the user. In addition to that, the attacker might use the access gained through that attack as leverage to get more privileges on the system.

Web Applications

CGI Perl scripts, PHP pages, and more complex Web applications can be started through a Web browser.

Cron Jobs

Programs that the cron daemon periodically run read input from a variety of sources.

To find out which processes are currently running with open network ports and might need a profile to confine them, run aa-unconfined as root.

Example 42-1 Output of aa-unconfined

19848 /usr/sbin/cupsd not confined
19887 /usr/sbin/sshd not confined
19947 /usr/lib/postfix/master not confined
29205 /usr/sbin/sshd confined by '/usr/sbin/sshd (enforce)'

Each of the processes in the above example labeled not confined might need a custom profile to confine it. Those labeled confined by are already protected by AppArmor.

HINT: For More Information

For more information about choosing the the right applications to profile, refer to “Selecting Programs to Immunize” (↑Novell AppArmor 2.0 Administration Guide).

42.3.2 Building and Modifying Profiles

Novell AppArmor on SUSE Linux Enterprise ships with a preconfigured set of profiles for the most important applications. In addition to that, you can use AppArmor to create your own profiles for any application you want.

There are two ways of managing profiles. One is to use the graphical front-end provided by the YaST Novell AppArmor modules and the other is to use the command line tools provided by the AppArmor suite itself. Both methods basically work the same way.

Running aa-unconfined as described in Section 42.3.1, Choosing the Applications to Profile identifies a list of applications that may need a profile to run in a safe mode.

For each application, perform the following steps to create a profile:

  1. As root, let AppArmor create a rough outline of the application's profile by running aa-genprof programname

    or

    Outline the basic profile by running YaST Novell AppArmor Add Profile Wizard and specifying the complete path of the application to profile.

    A basic profile is outlined and AppArmor is put into learning mode, which means that it logs any activity of the program you are executing but does not yet restrict it.

  2. Run the full range of the application's actions to let AppArmor get a very specific picture of its activities.

  3. Let AppArmor analyze the log files generated in Step 2 by running typing S in aa-genprof.

    or

    Analyze the logs by clicking Scan system log for AppArmor events in the Add Profile Wizard and following the instructions given in the wizard until the profile is completed.

    AppArmor scans the logs it recorded during the application's run and asks you to set the access rights for each event that was logged. Either set them for each file or use globbing.

  4. Once all access permissions are set, your profile is set to enforce mode. The profile is applied and AppArmor restricts the application according to the profile just created.

    If you started aa-genprof on an application that had an existing profile that was in complain mode, this profile remains in learning mode upon exit of this learning cycle. For more information about changing the mode of a profile, refer to “aa-complain—Entering Complain or Learning Mode” (Chapter “Building Novell AppArmor Profiles”, ↑Novell AppArmor 2.0 Administration Guide) and “aa-enforce—Entering Enforce Mode” (Chapter “Building Novell AppArmor Profiles”, ↑Novell AppArmor 2.0 Administration Guide).

Test your profile settings by performing every task you need with the application you just confined. Normally, the confined program runs smoothly and you do not notice AppArmor activities at all. However, if you notice certain misbehavior with your application, check the system logs and see if AppArmor is too closely constricting your application. Depending on the log mechanism used on your system, there are several places to look for AppArmor log entries:

/var/log/audit.log

If the audit package is installed and auditd is running, AppArmor events are logged as follows:

type=APPARMOR msg=audit(1140325305.502:1407): REJECTING w access to
/usr/lib/firefox/update.test (firefox-bin(9469) profile
/usr/lib/firefox/firefox-bin active /usr/lib/firefox/firefox-bin)
/var/log/messages

If auditd is not used, AppArmor events are logged in the standard system log under /var/log/messages. An example entry would look like the following:

Feb 22 18:29:14 dhcp-81 klogd: audit(1140661749.146:3): REJECTING w access
to /dev/console (mdnsd(3239) profile /usr/sbin/mdnsd active /usr/sbin/mdnsd)
dmesg

If auditd is not running, AppArmor events can also be checked using the dmesg command:

audit(1140661749.146:3): REJECTING w access to /dev/console (mdnsd(3239)
profile /usr/sbin/mdnsd active /usr/sbin/mdnsd)

To adjust the profile, analyze the log messages relating this application again as described in Step 3. Determine the access rights or restrictions when prompted.

HINT: For More Information

For more information about profile building and modification, refer to “Building Novell AppArmor Profiles” (↑Novell AppArmor 2.0 Administration Guide).

42.3.3 Configuring Novell AppArmor Event Notification and Reports

Set up event notification in Novell AppArmor so you can review security events. Event Notification is an Novell AppArmor feature that informs a specified e-mail recipient when systemic Novell AppArmor activity occurs under the chosen severity level. This feature is currently available in the YaST interface.

To set up event notification in YaST, proceed as follows:

  1. Make sure that a mail server is running on your system to deliver the event notifications.

  2. Log in as root and start YaST. Then select Novell AppArmor AppArmor Control Panel ).

  3. In Enable Security Event Notification, select Configure.

  4. For each record type (Terse, Summary, and Verbose), set a report frequency, enter the e-mail address that should receive the reports, and determine the severity of events to log. To include unknown events in the event reports, check Include Unknown Severity Events.

    NOTE: Selecting Events to Log

    Unless you are familiar with AppArmor's event categorization, choose to be notified about events for all security levels.

  5. Leave this dialog with OK Finish to apply your settings.

Using Novell AppArmor reports, you can read important Novell AppArmor security events reported in the log files without manually sifting through the cumbersome messages only useful to the aa-logprof tool. You can decrease the size of the report by filtering by date range or program name.

To configure the AppArmor reports, proceed as follows:

  1. Log in as root and start YaST. Select Novell AppArmor AppArmor Reports .

  2. Select the type of report to examine or configure from Executive Security Summary, Applications Audit, and Security Incident Report.

  3. Edit the report generation frequency, e-mail address, export format, and location of the reports by selecting Edit and providing the requested data.

  4. To run a report of the selected type, click Run Now.

  5. Browse through the archived reports of a given type by selecting View Archive and specifying the report type.

    or

    Delete unneeded reports or add new ones.

HINT: For More Information

For more information about configuring event notification in Novell AppArmor, refer to “Setting Up Event Notification” (Chapter “Managing Profiled Applications”, ↑Novell AppArmor 2.0 Administration Guide). Find more information about report configuration in “Reports” (Chapter “Managing Profiled Applications”, ↑Novell AppArmor 2.0 Administration Guide).

42.3.4 Updating Your Profiles

Software and system configurations change over time. As a result of that, your profile setup for AppArmor might need some fine-tuning from time to time. AppArmor checks your system log for policy violations or other AppArmor events and lets you adjust your profile set accordingly. Any application behavior that is outside of any profile definition can also be addressed using the Update Profile Wizard.

To update your profile set, proceed as follows:

  1. Log in as root and start YaST.

  2. Start Novell AppArmor Update Profile Wizard .

  3. Adjust access or execute rights to any resource or for any executable that has been logged when prompted.

  4. Leave YaST after you answer all questions. Your changes are applied to the respective profiles.

HINT: For More Information

For more information about updating your profiles from the system logs, refer to “Updating Profiles from Log Entries” (Chapter “Building Novell AppArmor Profiles”, ↑Novell AppArmor 2.0 Administration Guide).

SUSE Linux Enterprise Desktop Deployment Guide
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