I have a bunch of virtual machines each one doing a dedicated task: one is hosting a database, another one is a web server using a specific technology, another one is a web server using a different stack, etc.
I thought about SELinux as a mean to prevent a propagation of an intrusion from one of those machines; if a hacker finds an exploit in the web server, I don't want him to be able to read
/etc/shadow file or connect to NFS, or... whatever.
Unfortunately, I'm using Debian, which doesn't seem to have a very good support of SELinux. I tried it for half an hour, encountered lots of problems at installation, including the missing selinux-policy-default, and found half a dozen resources telling that Debian and SELinux don't play well together.
Technically, nothing prevents me from moving to CentOS, so my question is not what should I do to solve the problems I've encountered.
My question is rather this. Since Debian is one of the most popular distributions for the servers and, I suppose, is used in environments which are much more sensitive than mine, and since nobody seemed to have an incentive to “fix” SELinux to work flawlessly, doesn't this indicate that SELinux is not that popular in the first place?
If it's actually unpopular, what are the more popular alternatives?
Or am I overestimating the importance of SELinux, and correctly configured firewall and file permissions are all that's needed?