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Red Hat Boosts SELinux With RHEL 5
E. Stride writes "Many IT managers find Security Enhanced Linux, or SELinux, to be wildly complex. The mandatory access controls originally developed by the NSA have developed a reputation for being too complicated to deal with, and many IT shops simply turn the feature off. However, Red Hat's Dan Walsh says it's the only way to ensure 100% protection in the data center."
There will never be a 100% protection. A good GUI with a wizard, like with SUSE's AppArmor, will help a lot of people from falling between the "naah, it broke something on my webserver, turning it off" and "I'll dedicate the two next months of my life to learn SELinux" chairs.
I shall go and tell the indestructible man that someone plans to murder him.
It can save a system from being compromised due to other services which are either weaker, or poorly configured. Taking some time to get SELinux working properly in ones production environment (if that system is important) is more than worth the time it takes to read up on it. Being a lazy sys admin rarely pays off in the long run.
"Thanks for all the money you paid to us. We've used it to buy off ISO among other things" -Microsoft
Ignoring for now that nowhere in the article does he claim that SELinux provides or is required for "100% security", there's no such damn thing. Unless you pull out the power cord, of course.
Yes, we disable SELinux at our shop. As the article mentions, it's a pain in the ass, and the tools to manage it are not mature enough. If all you have is RHEL, and you have nothing else to do, you can look at configuring it. If you have a bunch of corporate mucky-mucks breathing down your neck, and you have to get the latest version of GnuWhatever compiled for 5 different OSs, there's no time to deal with this nonsense.
SELinux probably works just great for what it was designed for - NSA top-secret systems. There's always a tradeoff between security and usability, and right now, SELinux is just above yanking the power cord.
Too late to be known as Bush the First, he's sure to be known as Bush the Worst.
The short version: it's very good. But a huge pain in the ass.
The slightly longer version: IPtables is about network access, firewalls, et cetera. SELinux is about ensuring the integrity and access rights of software on your system. It's designed to prevent, say, one process on your machine from overwriting a file it should be able to. There's a pretty good explanation of exactly what it buys you here. (Warning: government site. They're watching youuuuuu!)
The problem with SELinux is that up until recently it has been a royal pain in the ass to configure. You'd go, "Sure, this sounds like a good idea", turn it on, and then curse it roundly when you tried updating MySQL from the version that ships with RHEL to the most recent supported release from MySQL. As a result, most folks just turned it off - they figured it wasn't worth the hassle.
RHEL 5 apparently includes tools (see the article) for figuring out what's wrong with your SELinux configuration. Definitely worth looking into. But if you're not concerned with validating application integrity on your home box... and let's face it, it's a home box... probably not worth it for you until it becomes dead simple.
For those who may not fully understand what SELinux actually does, let me give you an example.
With SELinux enabled, by detault Apache will be prevented from accessing files other than those of very basic web apps, it cannot open sockets to other hosts, etc.
For IntErnet applications this is quite reasonable and with the machine on the most hostile network around you really should use SELinux. It won't stop a break in but it can seriously curtail the effects of one.
For an IntrAnet application that is trying to write to custom log files and talk to LDAP servers and such, SELinux is not going to let you do that. At this point you have two choices - 1) tweek SELinux properties to allow only the specific functionality required by the application or 2) disable SELinux for that entire application. Considering an IntrAnet affords some physical protection, SELinux is less important in that environment and therefore, in this scenario, if you're really not savvy with SELinux and you don't have the time to get into it, I recommend just disabling it for entire application using it.
For example, to disable SELinux just for Apache you do:
# setsebool -P httpd_disable_trans 1
# service httpd restart
Note that SELinux uses db files that remember these changes so they will persist across reboots and there are no config files to edit. It's a nice system because it's easy to add these commands to install scripts and such.
So don't get bent about SELinux. Learn enough to disable it for specific apps and then turn it on all over. Keep an eye on the log files. If SELinux is stopping access to things by apps it will report it in the log file. Then determine if the app should be doing that and if so disable SELinux just for that app.
saying that you can't install things while selinux is running is a flaw of selinux is like complaining about needing to be root to install things. its job is to keep shit from changing, changes like installing mysql could be done while it was running it wouldn't be doing its job. disabling it long enough to make changes is just like su or sudo to get temporary root access inside your normal user environment.
disclaimer -- I may be completely off base because I don't use it in a production environment, I disable it during install whenever putting a fedora box up for use.
thats right, I rarely use capitals. deal with it. but don't mistake my laziness for stupidity
Whatever Redhat says, the fact remains that SELinux is an incredibly complex, and incredibly undocumented (or under-documented) piece of software. It took me two months to really understand how it worked and what exactly to configure when I needed to fine-tune access rights and permissions on our servers. That is a nightmare I wouldn't wish on anyone.
Redhat is not going to get much traction from this unless there is a very easy to use tool (preferably with GUI) to configure and customize SELinux, out of the box. The default tools on RHEL allow a few options during install time, but it is truly primitive.
There really doesn't need to be this huge love/hate relationship with SELinux, in fact why not just throw it out and use something far simpler and neater? There are several options out there. Off the top of my head I can think of GRSEC : http://www.grsecurity.net/
We've been using this on two of our server farms and it's been doing a superb job, and it is very very easy to customize compared to the SElinux nightmare.
Very off topic, but I was just thinking...
windows with it's constant prompts to do stuff while performing the same task gets very annoying and will quickly train the user to just click the allow, rendering it practically pointless.
Clearly, in order to make users think about this, a 5 second delay has to be introduced before the Allow/Deny buttons are active...
It's designed to prevent, say, one process on your machine from overwriting a file it should be able to.
Yeah, that pretty much sums up my experience too.
I have found there are just two ways to go.
It all comes down to livin' fast or dyin' slow. -REK, Jr.
Common problem: you built a library (a *.so file) without compiling all the object files (the *.o things) with gcc's -fpic or -fPIC option, and/or you forgot to specify -shared when linking.
When you make this kind of screw-up, you cause something called "text relocations". These don't even work on non-x86 and Debian bans them anyway for reasons related to memory usage. A text relocation means that the loader patches the code itself, rather slowly, when loading the shared library. This requires memory to be both writable and executable, which is a no-no for security against buffer overflows. SE Linux is usually set up to prohibit this by default.
If your broken shit runs as a server or gets loaded into a web browser, you greatly decrease security. You suck. Fix your shit.
I'm a developer too. I've upped my standards. Up yours!
AppArmor's main approach is somewhat less broad. It is more like putting certain applications into a MAC container to limit what an application can do, no matter who the user using the application is. A great example of this that most Slashdot readers should look into is putting the browser into a safety container.
Some time ago, I wrote a review of AppArmor, finding that it solves problems that don't exist. Looking at your browser example, the functionality provided by AppArmor can be implemented completely by setting up a different user and setting appropriate file ACLs.
For the real problems AppArmor provides little help. Can you confine network usage of a program, meaning your internal network cannot be accessed once your browser has been hacked? No. Can you limit the syscalls a program may use, reducing the risk of successful kernel exploits? No.
As long as it stays this way, I recommend to everyone to use SELinux, even though it is much more difficult to setup and configure.
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Why's there a "however" inbetween. It's both right. SELinux is complex and hard to understand. Heck, I should know I've given speeches at half a dozen conferences about it. And at the same time, it is the most secure option Linux has at this time.
Yes, there are alternatives.
Yes, some of them are easier to understand.
No, none of them give you the level and sophistication of SELinux, not even close.
No, that's not likely to change very much. Security is hard to do.
Assorted stuff I do sometimes: Lemuria.org