SELinux

• https://en.wikipedia.org/wiki/Security-Enhanced_Linux
• https://people.redhat.com/duffy/selinux/selinux-coloring-book_A4-Stapled.pdf
• http://www.freekb.net/Article?id=1418 – SELinux - Change context of a file or directory (chcon restorecon semanage) !!!!!
• http://www.freekb.net/Article?id=1169 – SELinux - Determine context of a file or directory

• https://www.man7.org/linux/man-pages/man8/semanage.8.html
• https://www.man7.org/linux/man-pages/man8/semanage-fcontext.8.html
• https://www.man7.org/linux/man-pages/man8/restorecon.8.html

learning.oreilly.com :

• https://learning.oreilly.com/topics/selinux/
• https://learning.oreilly.com/library/view/selinux-system-administration/9781800201477/
• https://learning.oreilly.com/library/view/selinux-cookbook/9781783989669/

access.redhat.com :

• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/using_selinux/
• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html/using_selinux/changing-selinux-states-and-modes_using-selinux
• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/using_selinux/index
• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/using_selinux/index#selinux-states-and-modes_getting-started-with-selinux
• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/8/html-single/using_selinux/index#changing-selinux-states-and-modes_using-selinux

setenforce / getenforce

• https://www.man7.org/linux/man-pages/man8/setenforce.8.html
• https://www.man7.org/linux/man-pages/man8/getenforce.8.html

root@… $ setenforce [Enforcing|Permissive|1|0]
root@… $ getenforce

context of a file

• https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/security-enhanced_linux/sect-security-enhanced_linux-working_with_selinux-selinux_contexts_labeling_files
• https://www.man7.org/linux/man-pages/man8/semanage.8.html
• https://www.man7.org/linux/man-pages/man8/semanage-fcontext.8.html
• http://www.freekb.net/Article?id=1418 !!!!!
• https://www.gnu.org/software/coreutils/manual/html_node/chcon-invocation.html – Change SELinux context of file

So far my usual approach for getting the SELinux context of a file right is:

# find a file with the right context! ("FILE_WITH_RIGHT_CONTEXT")
$ ll --context FILE_WITH_RIGHT_CONTEXT
# rename the file, whose context isn't right, to FILE- or so!
$ mv FILE FILE-
# …
$ cp --arch FILE_WITH_RIGHT_CONTEXT FILE
# …
cat FILE- > FILE
# …
$ rm FILE-
…

What "ll -Z" (resp. "ll --context") in addition to what "ll" usually displays, is called:

• a SELinux_USER_CONTEXT (unconfined_u) -> "semanage fcontext --modify --seuser"
• a ROLE (object_r)
• a TYPE_CONTEXT (user_home_t) -> "semanage fcontext --modify --type"
• a level AKA RANGE (s0) -> "semanage fcontext "

CAVEAT: chcon does not work well with restorecon. restorecon effectively restores the old context.

root@… $ semanage fcontext --add/--modify --seuser SELinux_USER_CONTEXT --role ROLE --type TYPE_CONTEXT /usr/local/foo.txt
root@… $ chcon --no-dereference --user SELinux_USER_CONTEXT --role ROLE --type TYPE_CONTEXT --range RANGE /usr/local/foo.txt

root@… $ restorecon -vF /usr/local/foo.txt     # -v for ''verbose'', -F for ''force reset''

So usually for a systemd service file you would execute these 2 resp.3 command lines:

root@… $ semanage fcontext --add/--modify --seuser system_u --role object_ --type systemd_unit_file_t /usr/lib/systemd/system/tomcat.service
root@… $ chcon --no-dereference --user system_u --role object_r --type systemd_unit_file_t --range s0 /usr/lib/systemd/system/tomcat.service

root@… $ restorecon -vF /usr/lib/systemd/system/tomcat.service

More examples:

…