NAME
selinux - NSA Security-Enhanced Linux (SELinux)
DESCRIPTION
NSA Security-Enhanced Linux (SELinux) is an implementation of a
flexible mandatory access control architecture in the Linux operating
system. The SELinux architecture provides general support for the
enforcement of many kinds of mandatory access control policies,
including those based on the concepts of Type Enforcement®, Role- Based
Access Control, and Multi-Level Security. Background information and
technical documentation about SELinux can be found at
http://www.nsa.gov/selinux.
The /etc/selinux/config configuration file controls whether SELinux is
enabled or disabled, and if enabled, whether SELinux operates in
permissive mode or enforcing mode. The SELINUX variable may be set to
any one of disabled, permissive, or enforcing to select one of these
options. The disabled option completely disables the SELinux kernel
and application code, leaving the system running without any SELinux
protection. The permissive option enables the SELinux code, but causes
it to operate in a mode where accesses that would be denied by policy
are permitted but audited. The enforcing option enables the SELinux
code and causes it to enforce access denials as well as auditing them.
Permissive mode may yield a different set of denials than enforcing
mode, both because enforcing mode will prevent an operation from
proceeding past the first denial and because some application code will
fall back to a less privileged mode of operation if denied access.
The /etc/selinux/config configuration file also controls what policy is
active on the system. SELinux allows for multiple policies to be
installed on the system, but only one policy may be active at any given
time. At present, two kinds of SELinux policy exist: targeted and
strict. The targeted policy is designed as a policy where most
processes operate without restrictions, and only specific services are
placed into distinct security domains that are confined by the policy.
For example, the user would run in a completely unconfined domain while
the named daemon or apache daemon would run in a specific domain
tailored to its operation. The strict policy is designed as a policy
where all processes are partitioned into fine-grained security domains
and confined by policy. It is anticipated in the future that other
policies will be created (Multi-Level Security for example). You can
define which policy you will run by setting the SELINUXTYPE environment
variable within /etc/selinux/config. The corresponding policy
configuration for each such policy must be installed in the
/etc/selinux/SELINUXTYPE/ directories.
A given SELinux policy can be customized further based on a set of
compile-time tunable options and a set of runtime policy booleans.
system-config-securitylevel allows customization of these booleans and
tunables.
Many domains that are protected by SELinux also include selinux man
pages explainging how to customize their policy.
FILE LABELING
All files, directories, devices ... have a security context/label
associated with them. These context are stored in the extended
attributes of the file system. Problems with SELinux often arise from
the file system being mislabeled. This can be caused by booting the
machine with a non selinux kernel. If you see an error message
containing file_t, that is usually a good indicator that you have a
serious problem with file system labeling.
The best way to relabel the file system is to create the flag file
/.autorelabel and reboot. system-config-securitylevel, also has this
capability. The restorcon/fixfiles commands are also available for
relabeling files.
AUTHOR
This manual page was written by Dan Walsh <dwalsh@redhat.com>.
SEE ALSO
booleans(8), setsebool(8), selinuxenabled(8), togglesebool(8),
restorecon(8), setfiles(8), ftpd_selinux(8), named_selinux(8),
rsync_selinux(8), httpd_selinux(8), nfs_selinux(8), samba_selinux(8),
kerberos_selinux(8), nis_selinux(8), ypbind_selinux(8)
FILES
/etc/selinux/config