Novell AppArmor provides a mod_change_hat module
for the Apache program. The mod_change_hat module works
on your SUSE Linux to make the Apache web server become
ChangeHat aware.
It is installed if Apache is on your
system.
When Apache is ChangeHat-aware, it checks for the following customized Novell AppArmor security profiles in the order given for every URI request that it receives.
URI-specific hat (for example, ^phpsysinfo-dev/templates/classic/images/bar_left.gif)
DEFAULT_URI
HANDLING_UNTRUSTED_INPUT
If you have the required Apache 2 on your system, the mod_change_hat module is automatically installed with Novell AppArmor as well as added to the Apache configuration. Apache 1.3 is not supported.
NOTE: If you install mod_change_hat without Novell AppArmor, you need to make sure the Apache load module has a command in the config file that loads the mod_change_hat module by adding the following line to your Apache configuration file:
LoadModule change_hat_module modules/mod_change_hat.so
As with most of the Novell AppArmor tools, you can use two methods for managing ChangeHat, YaST or the command line interface. Manage ChangeHat-aware applications much more flexibly at the command line, but the process is also more complicated. Both methods allow you to manage the hats for your application and populate them with profile entries.
In the following steps, we walk you through a demo that adds hats to an Apache profile using YaST. In the
, the Novell AppArmor profiling utilities prompt you to create new hats for distinct URI requests. Choosing to create a new hat allows you to create individual profiles for each URI. This allows you to create very tight rules for each request.If the URI that is processed does not represent significant processing or otherwise does not represent a significant security risk, you may safely select
to process this URI in the default hat, which is the default security profile.In the demo, we create a new hat for the URI phpsysinfo-dev and its subsequent accesses. Using the profiling utilities, we delegate what is added to this new hat. The resulting hat becomes a tight-security container that encompasses all the processing on the server that occurs when the phpsysinfo-dev URI is passed to the Apache Web server.
In this demo, we generate a profile for the application phpsysinfo (refer to http://phpsysinfo.sourceforge.net for more information). The phpsysinfo-dev package is assumed to be installed under /srv/www/htdocs/phpsysinfo-dev/ in a clean (new) install of Novell AppArmor.
Once phpsysinfo-dev is installed, you are ready to add hats to the Apache profile. From the Novell AppArmor GUI, select
.In
, enter httpd2-prefork.Click
. The window opens.Restart Apache by entering rcapache2 restart in a terminal window.
NOTE: Restart any program you are profiling at this point.
Open http://localhost/phpsysinfo-dev/ in a Web browser window. The browser window should display network usage and system information.
NOTE: To ensure that this request is processed by the server and you do not review cached data in your browser, you should refresh the page. To do this, click the browser
button to make sure that Apache processes the request for the phpsysinfo-dev URI.Click
. Novell AppArmor launches the logprof tool, which scans the all the information learned in the previous step. It begins to prompt you with profile questions.In our demo, logprof first prompts us with
or because it noticed that a URI was accessed phpsysinfo-dev. Select .Click
.Choosing
in the previous step creates a new hat in the profile and specifies that subsequent questions about the script's actions are added to the newly created hat rather than the default hat for this application.In the next screen, Novell AppArmor displays an external program that the script executed. You can specify that the program should run confined by the phpsysinfo-dev hat (choose
), confined by a separate profile (choose ), or that it should run unconfined or without any security profile (choose ). For the case of the option, a new profile is created for the program if one does not already exist.NOTE: Selecting
can create a significant security hole and should be done with caution.Select /bin/bash path. This adds /bin/bash/ (accessed by Apache) to the phpsysinfo-dev hat profile with the necessary permissions.
for theClick
.The remaining questions prompt you to generate new hats and add entries to your profile and its hats. The process of adding entries to profiles is covered in detail in the section Section 3.3.1, Adding a Profile Using the Wizard.
When all profiling questions are answered, click
to save your changes and exit the wizard.The following is an example of what a phpsyinfo-dev hat might resemble.
Example number="5-1"
^phpsysinfo { #include <program-chunks/base-files> /bin/df ix, /bin/bash ix, /dev/tty rw, /etc/SuSE-release r, /etc/fstab r, /etc/hosts r, /etc/mtab r, /proc/** r, /sbin/lspci ix, /srv/www/htdocs/sysinfo/** r, /sys/bus/pci/devices r, /sys/devices/** r, /usr/bin/who ix, /usr/share/pci.ids r, /var/log/apache2/{access,error}_log w, /var/run/utmp r, }
NOTE: The profile, ^phpsysinfo-dev, is only valid in the context of a process running under the parent profile httpd2-prefork.
When you use the Section 3.3.3, Editing a Profile) or when you add a new profile using (for instructions, refer to Section 3.3.2, Manually Adding a Profile), you are given the option of adding hats (subprofiles) to your Novell AppArmor profiles.
dialog (for instructions, refer toYou can add a ChangeHat subprofile from the
window.From the
window, click then select .The dialog box opens:Enter the name of the hat to add to the Novell AppArmor profile. The name is the URI that, when accessed, receives the permissions set in the hat.
Click
. You are returned to the screen.After adding the new hat, click
.NOTE: For an example of an Novell AppArmor profile, refer to Section 5-1, Example phpsysinfo-dev Hat.