Paranoid Penguin - Introduction to SELinux, Part II
The comprehensive “deny-by-default” policy originally developed for Fedora Core 2, called strict, is still maintained for RHEL, Fedora and CentOS, and it can be installed instead of targeted. However, strict is not officially (commercially) supported in RHEL due to its complexity. On most systems, this policy takes a lot of manual tweaking, both by editing the files in /etc/selinux and by using the standard SELinux commands chcon, checkpolicy, getenforce, newrole, run_init, setenforce and setfiles.
Note that Tresys (www.tresys.com) maintains a suite of free, mainly GUI-based, SELinux tools that are a bit easier to use, including SePCuT, SeUser, Apol and SeAudit. These are provided by RHEL's setools RPM package. Note also that on non-Red-Hat-derived Linux distributions, SELinux policies usually reside in /etc/security/selinux.
To customize and use the strict policy on RHEL 4, see Russell Coker's tutorial “Introduction to SELinux on Red Hat Enterprise Linux 4” (see Resources). You need to install the package selinux-policy-strict, available in Fedora's rawhide repository (the selinux-policy-strict package in Fedora Core 5 or 6 may also work in RHEL 4).
It's also possible, of course, to develop and enable your own SELinux policies from scratch, though doing that is well beyond the scope of this article. In fact, entire books have been written on this topic. See Resources for information on SELinux policy creation and customization.
And with that, I hope you're off to a good start with SELinux. Be safe!
Faye and Russell Coker's article “Taking advantage of SELinux in Red Hat Enterprise Linux”: www.redhat.com/magazine/006apr05/features/selinux
McCarty, Bill. SELinux: NSA's Open Source Security Enhanced Linux. Sebastopol, CA: O'Reilly Media, 2005. Definitive resource, but predates Red Hat and Fedora's implementation of targeted and strict policies.
Mayer, Frank, Karl MacMillan and David Caplan. SELinux by Example: Using Security Enhanced Linux. Upper Saddle River, NJ: Prentice Hall, 2007. Brand-new book, by several SELinux contributors.
Chad Hanson's paper “SELinux and MLS: Putting the Pieces Together”: selinux-symposium.org/2006/papers/03-SELinux-and-MLS.pdf
“Red Hat Enterprise Linux 4: Red Hat SELinux Guide”: www.redhat.com/docs/manuals/enterprise/RHEL-4-Manual/selinux-guide/index.html
Russell Coker's tutorial “Introduction to SELinux on Red Hat Enterprise Linux 4”: www.coker.com.au/selinux/talks/rh-2005/rhel4-tut.html
Mick Bauer (email@example.com) is Network Security Architect for one of the US's largest banks. He is the author of the O'Reilly book Linux Server Security, 2nd edition (formerly called Building Secure Servers With Linux), an occasional presenter at information security conferences and composer of the “Network Engineering Polka”.
Practical Task Scheduling Deployment
July 20, 2016 12:00 pm CDT
One of the best things about the UNIX environment (aside from being stable and efficient) is the vast array of software tools available to help you do your job. Traditionally, a UNIX tool does only one thing, but does that one thing very well. For example, grep is very easy to use and can search vast amounts of data quickly. The find tool can find a particular file or files based on all kinds of criteria. It's pretty easy to string these tools together to build even more powerful tools, such as a tool that finds all of the .log files in the /home directory and searches each one for a particular entry. This erector-set mentality allows UNIX system administrators to seem to always have the right tool for the job.
Cron traditionally has been considered another such a tool for job scheduling, but is it enough? This webinar considers that very question. The first part builds on a previous Geek Guide, Beyond Cron, and briefly describes how to know when it might be time to consider upgrading your job scheduling infrastructure. The second part presents an actual planning and implementation framework.
Join Linux Journal's Mike Diehl and Pat Cameron of Help Systems.
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