7.4.1 How to React to odd Application Behavior?

If you notice odd application behavior or any other type of application problem, you should first check the reject messages in the log files to see if AppArmor is too closely constricting your application. To check reject messages, start YaST > Novell AppArmor and go to AppArmor Reports. Select View Archive and App Aud for the application audit report. You can filter dates and times to narrow down the specific periods when the unexpected application behavior occurred.

If you detect reject messages that indicate that your application or service is too closely restricted by AppArmor, update your profile to properly handle your use case of the application. Do this with the Update Profile Profile Wizard in YaST, as described in Section 3.5, Updating Profiles from Log Entries.

If you decide to run your application or service without AppArmor protection, remove the application's profile from /etc/apparmor.d or move it to another location.

7.4.2 My Profiles do not Seem to Work Anymore …

If you have been using previous versions of AppArmor and have updated your system, but kept your old set of profiles, you might notice some applications behaving strangely or not working at all which seemed to work perfectly before you updated.

This version of AppArmor introduces a set of new features to the profile syntax and the AppArmor tools that might cause trouble with older versions of the AppArmor profiles. The features concerned are:

The current version of AppArmor mediates file locking and introduces a new permission mode (k) for this. Applications requesting file locking permission might misbehave or fail altogether if confined by older profiles which do not explicitly contain permissions to lock files. If you suspect this being the case, check the log file under /var/log/audit/audit.log for entries like the following:

type=APPARMOR_DENIED msg=audit(1188913493.299:9304): operation="file_lock" requested_mask="k" denied_mask="k" name="/home/tux/.qt/.qtrc.lock" pid=25736 profile="/usr/bin/opera"

Update the profile using the YaST Update Profile Wizard or the aa-logprof command as outlined below.

The new network access control syntax based on the network family and type specification, described in Section 2.1.1, Network Access Control, might cause application misbehavior or even stop applications from working. If you notice a network-related application behaving strangely, check the log file under /var/log/audit/audit.log for entries like the following:

type=APPARMOR_DENIED msg=audit(1188894313.206:9123): operation="socket_create" family="inet" sock_type="raw" protocol=1 pid=23810 profile="/bin/ping"

This log entry means that our example application, /bin/ping in this case, failed to get AppArmor's permission to open a network connection. This permission has to be explicitly stated to make sure that an application has network access. To update the profile to the new syntax, use the YaST Update Profile Wizard or the aa-logprof command as outlined below.

The current kernel requires the SYS_PTRACE capability, if a process tries to access files in /proc/pid/fd/*. New profiles need an entry for the file and the capability where old profiles only needed the file entry. For example:

/proc/*/fd/**  rw,

in the old syntax would translate to the following rules in the new syntax:

capability SYS_PTRACE,
/proc/*/fd/**  rw,

To update the profile to the new syntax, use the YaST Update Profile Wizard or the aa-logprof command as outlined below.

With this version of AppArmor, a few changes have been made to the profile rule syntax to better distinguish directory from file access. Therefore, some rules matching both file and directory paths in the previous version might now just match a file path. This could lead to AppArmor not being able to access a crucial directory at all and thus trigger misbehavior of your application and various log messages. The following examples highlight the most important changes to the path syntax.

Using the old syntax, the following rule would allow access to files and directories in /proc/net. It would allow directory access only to read the entries in the directory, but not give access to files or directories under the directory, e.g. /proc/net/dir/foo would be matched by the asterisk (*), but as foo is a file or directory under dir, it cannot be accessed.

/proc/net/*  r, 

To get the same behavior using the new syntax, you need two rules instead of one. The first allows access to file under /proc/net and the second allows access to directories under /proc/net. Directory access can only be used for listing the contents, not to actually access files or directories underneath the directory.

/proc/net/*  r,  
/proc/net/*/  r,    

The following rule works similarly both under the old and the new syntax and allows access to both files and directories under /proc/net:

/proc/net/**  r,   

To distinguish file from directory access using the above expression in the new syntax, use the following two rules. The first one only allows to recursively access directories under /proc/net while the second one explicitly allows for recursive file access only.

/proc/net/**/  r,  
/proc/net/**[^/]  r,

The following rule works similarly both under the old and the new syntax and allows access to both files and directories beginning with foo under /proc/net:

/proc/net/foo**  r,

To distinguish file from directory access in the new syntax and use the ** globbing pattern, use the following two rules. The first one would have matched both files and directories in the old syntax, but only matches files in the new syntax due to the missing trailing slash. The second rule matched neither file nor directory in the old syntax, but matches directories only in the new syntax:

/proc/net/**foo  r,
/proc/net/**foo/  r, 

The following rules illustrate how the use of the ? globbing pattern has changed. In the old syntax, the first rule would have matched both files and directories (four characters, last character could be any but a slash). In the new syntax, it matches only files (trailing slash is missing). The second rule would match nothing in the old profile syntax, but matches directories only in the new syntax. The last rule matches explicitly matches a file called bar under /proc/net/foo?. Using the old syntax, this rule would have applied to both files and directories:

/proc/net/foo?  r,    
/proc/net/foo?/  r, 
/proc/net/foo?/bar  r,

To find and resolve issues related to syntax changes, take some time after the update to check the profiles you want to keep and proceed as follows for each application you kept the profile for:

Using the AppArmor command line tools, you would proceed as follows:

7.4.3 How to Confine KDE Applications with AppArmor?

Currently, it is not possible to confine KDE applications to the same extent as any other application due to the way KDE manages its processes.

If you want to confine KDE applications, choose one of the following approaches, but note that none of them is really suited for a standard setup:

Create a Single Profile for the Entire KDE Desktop

As all KDE processes are children of one parent process and AppArmor cannot distinguish an individual application's process from the rest, create one huge profile to confine the entire desktop all at once. This approach is only feasible if your setup is a very limited (kiosk-type) one. Maintaining such a profile for a standard KDE desktop including all of its applications would be close to impossible.

Modify KDE's process handling

Use KDE_EXEC_SLAVES=1 and KDE_IS_PRELINKED=1 variables force KDE to manage its processes in a way that AppArmor can distinguish individual applications from each other and apply profiles to them. This approach might slow down your desktop considerably, as it turns off a crucial optimization for speed. Note that the above mentioned environment variables have to be set before KDM/XDM/GDM or startx are started. One way to achieve this would be to add them to /etc/security/pam_env.conf.

7.4.4 How to Resolve Issues with Apache?

Apache is not starting properly or it is not serving Web pages and you just installed a new module or made a configuration change. When you install additional Apache modules (like apache2-mod_apparmor) or make configuration changes to Apache, you should profile Apache again to catch any additional rules that need to be added to the profile.

7.4.5 Why are the Reports not Sent by E-Mail?

When the reporting feature generates an HTML or CSV file that exceeds the default size, the file is not sent. Mail servers have a default, hard limit for e-mail size. This limitation can impede AppArmor's ability to send e-mails that are generated for reporting purposes. If your mail is not arriving, this could be why. Consider the mail size limits and check the archives if e-mails have not been received.

7.4.6 How to Exclude Certain Profiles from the List of Profiles Used?

AppArmor always loads and applies all profiles that are available in its profile directory (/etc/apparmor.d/). If you decide not to apply a profile to a certain application, delete the appropriate profile or move it to another location where AppArmor would not check for it.

7.4.7 Can I Manage Profiles for Applications not Installed on my System?

Managing profiles with AppArmor requires you to have access to a the system's log the application is running on. So you do not need to run the application on your profile build host as long as you have access to the machine that runs the application. You can run the application on one system, transfer the logs (/var/log/audit.log or, if audit is not installed, /var/log/messages) to your profile build host and run aa-logprof -f path_to_logfile.

7.4.8 How to Spot and fix AppArmor Syntax Errors?

Manually editing Novell AppArmor profiles can introduce syntax errors. If you attempt to start or restart AppArmor with syntax errors in your profiles, error results are shown. This example shows the syntax of the entire parser error.

localhost:~ # rcapparmor start
Loading AppArmor profiles
AppArmor parser error, line 2: Found unexpected character: ’h’
Profile /etc/apparmor.d/usr.sbin.squid failed to load
failed

Using the AppArmor YaST tools, a graphical error message indicates which profile contained the error and requests you to fix it.

To fix a syntax error, log in to a terminal window as root, open the profile, and correct the syntax. Reload the profile set with rcapparmor reload.