Installing OTRS in Fedora 18 with SELinux enabled

I’ve read somewhere in an OTRS installation howto that if you want to install OTRS, you will have to disable SELinux. Well, I won’t.

During the last few months, I have been using Fedora 18 with SELinux on all of my desktop machines and on my notebook, and I had no problems at all. Meanwhile I got familiar with SELinux itself, and got used to solving problems caused by it. So I started tail -f /var/log/httpd/error_log in one terminal (to see if something Apache related thing appears), tail -f /var/log/audit/audit.log in another (to see errors caused by SELinux), opened the admin manual at the installation chapter, took a deep breath, and went on.

Throughout this article, I will refer to OTRS 3.2.6 as OTRS and Fedora 18 (with only “stock” repositories) as Fedora. I assume that you have already installed OTRS in a non-SELinux environment before, and that you have at least some basic knowledge about SELinux, MAC, RBAC, and all the like. I’m installing OTRS in /opt/otrs, so if you install it somewhere else, you will have to modify the paths below. Also, if you happen to install under /var/www (I wouldn’t recommend it), that directory already has the httpd_sys_content_t type, so you won’t have to set it explicitly.

As the first step I have unpacked the archive to /opt/otrs. This directory is the OTRS default, many config files have it hardcoded, and changing it is no easy task.

Running gave me a list of missing perl modules. Red Hat and Fedora makes it easy to install these, as you don’t have to know the RPM package name, just the perl module name:

yum install 'perl(Crypt::SSLeay)' \
            'perl(DBD::Pg)' \
            'perl(GD)' \
            'perl(JSON::XS)' \
            'perl(GD::Text)' \
            'perl(GD::Graph)' \
            'perl(Mail::IMAPClient)' \
            'perl(Net::DNS)' \
            'perl(PDF::API2)' \
            'perl(Text::CSV_XS)' \

I also needed to install mod_perl. Although didn’t mention it, the default settings use syslog as the logging module, so unless you change it in, you will also need to install 'perl(Unix::Syslog)', either.

The default SELinux policy doesn’t permit any network connection to be initiated by Apache httpd. As OTRS needs to connect to its database, you need to enable it explicitly. In older distributions, the httpd_can_network_connect was the SELinux boolean for this, but recent installations also have a httpd_can_network_connect_db flag. As far as I know, this enables all network connections to the well-known database servers’ default port, but I will have to check for it. For me, with a MySQL listening on its standard port, the setsebool httpd_can_network_connect_db=1 command just did it.

With SELinux enabled, Apache won’t be able to read anything that’s not marked with the httpd_sys_content_t type, nor write anywhere without the httpd_sys_rw_content_t type. The trivial, quick and dirty solution is to label all the files as httpd_sys_rw_content_t, and let everything go. However, the goal of SELinux is just the opposite of this: grant access only to what is really needed. After many trial-and-error steps, it finally turned out that for OTRS to work correctly, you must set

  • httpd_sys_content_t
    • on /opt/otrs/var/httpd/htdocs
  • httpd_script_exec_t
    • on /opt/otrs/bin/cgi-bin
  • httpd_sys_rw_content_t
    • on /opt/otrs/Kernel
    • on /opt/otrs/var/sessions
    • on /opt/otrs/var/log (unless you use syslog for logging)
    • on /opt/otrs/var/packages (this is used only when you download an .opm package)
    • on /opt/otrs/var/stats
    • on /opt/otrs/var/tmp
    • on /opt/otrs/bin (I wonder why this is required, though)

To do this, use the following command:

semanage fcontext -a -t <context> <directory regex>

Where <directory regex> is something like /opt/otrs/Kernel(/.*)?. When this is done, all you have to do is running restorecon -vR /opt/otrs so it will relabel everything with the correct types (you can omit -v, I just like to see what my software do).

The last thing I faced is that Fedora is more restrictive on reading directories other than /var/www. It has a Require all denied on <Directory />, and a Require all granted on <Directory /var/www>, so /opt/otrs/var/httpd/htdocs will throw a 403 Forbidden (client denied by server configuration) error. To get rid of this, I had to modify scripts/apache2-httpd.include.conf and add Require all granted to both the cgi-bin and htdocs directories.

As I will have to use OTRS in a production environment soon with SELinux enabled, it is more than sure that this list will change in the near future. As there are no official documentation on this (I haven’t find one yet), I have to do it with the trial-and-error way, so be patient!

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