Security-Enhanced Linux secures the system_cronjob processes via flexible mandatory access control.
The system_cronjob processes execute with the system_cronjob_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.
ps -eZ | grep system_cronjob_t
The system_cronjob_t SELinux type can be entered via the usr_t, shell_exec_t, anacron_exec_t, bin_t, system_cron_spool_t, fusefs_t, nfs_t, cifs_t file types.
The default entrypoint paths for the system_cronjob_t domain are the following:
All executables with the default executable label, usually stored in /usr/bin and /usr/sbin. /opt/.*, /usr/.*, /emul/.*, /export(/.*)?, /ostree(/.*)?, /usr/doc(/.*)?/lib(/.*)?, /usr/inclu.e(/.*)?, /usr/share/rpm(/.*)?, /usr/share/doc(/.*)?/README.*, /usr/lib/modules(/.*)/vmlinuz, /usr/lib/modules(/.*)/initramfs.img, /usr/lib/sysimage(/.*)?, /usr/lib/ostree-boot(/.*)?, /opt, /usr, /emul, /bin/d?ash, /bin/ksh.*, /bin/zsh.*, /usr/bin/d?ash, /usr/bin/ksh.*, /usr/bin/zsh.*, /bin/esh, /bin/bash, /bin/fish, /bin/mksh, /bin/sash, /bin/tcsh, /bin/yash, /bin/bash2, /usr/bin/esh, /sbin/nologin, /usr/bin/bash, /usr/bin/fish, /usr/bin/mksh, /usr/bin/sash, /usr/bin/tcsh, /usr/bin/yash, /usr/bin/bash2, /usr/sbin/sesh, /usr/sbin/smrsh, /usr/bin/scponly, /usr/libexec/sesh, /usr/sbin/nologin, /usr/bin/git-shell, /usr/sbin/scponlyc, /usr/libexec/sudo/sesh, /usr/bin/cockpit-bridge, /usr/libexec/cockpit-agent, /usr/libexec/git-core/git-shell, /usr/sbin/anacron, /etc/cron.d(/.*)?, /var/spool/anacron(/.*)?, /etc/crontab, /var/spool/fcron/systab, /var/spool/fcron/new.systab, /var/spool/fcron/systab.orig, /var/run/user/[0-9]+/gvfs
SELinux defines process types (domains) for each process running on the system
You can see the context of a process using the -Z option to psbP
Policy governs the access confined processes have to files. SELinux system_cronjob policy is very flexible allowing users to setup their system_cronjob processes in as secure a method as possible.
The following process types are defined for system_cronjob:
Note: semanage permissive -a system_cronjob_t can be used to make the process type system_cronjob_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated.
SELinux policy is customizable based on least access required. system_cronjob policy is extremely flexible and has several booleans that allow you to manipulate the policy and run system_cronjob with the tightest access possible.
If you want to allow system cron jobs to relabel filesystem for restoring file contexts, you must turn on the cron_can_relabel boolean. Disabled by default.
setsebool -P cron_can_relabel 1
If you want to allow system cronjob to be executed on on NFS, CIFS or FUSE filesystem, you must turn on the cron_system_cronjob_use_shares boolean. Disabled by default.
setsebool -P cron_system_cronjob_use_shares 1
If you want to deny user domains applications to map a memory region as both executable and writable, this is dangerous and the executable should be reported in bugzilla, you must turn on the deny_execmem boolean. Enabled by default.
setsebool -P deny_execmem 1
If you want to control the ability to mmap a low area of the address space, as configured by /proc/sys/vm/mmap_min_addr, you must turn on the mmap_low_allowed boolean. Disabled by default.
setsebool -P mmap_low_allowed 1
If you want to disable kernel module loading, you must turn on the secure_mode_insmod boolean. Enabled by default.
setsebool -P secure_mode_insmod 1
If you want to allow unconfined executables to make their heap memory executable. Doing this is a really bad idea. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla, you must turn on the selinuxuser_execheap boolean. Disabled by default.
setsebool -P selinuxuser_execheap 1
If you want to allow unconfined executables to make their stack executable. This should never, ever be necessary. Probably indicates a badly coded executable, but could indicate an attack. This executable should be reported in bugzilla, you must turn on the selinuxuser_execstack boolean. Enabled by default.
setsebool -P selinuxuser_execstack 1
The SELinux process type system_cronjob_t can manage files labeled with the following file types. The paths listed are the default paths for these file types. Note the processes UID still need to have DAC permissions.
all files on the system
semanage fcontext can also be used to manipulate default file context mappings.
semanage permissive can also be used to manipulate whether or not a process type is permissive.
semanage module can also be used to enable/disable/install/remove policy modules.
semanage boolean can also be used to manipulate the booleans
system-config-selinux is a GUI tool available to customize SELinux policy settings.
This manual page was auto-generated using sepolicy manpage .
selinux(8), system_cronjob(8), semanage(8), restorecon(8), chcon(1), sepolicy(8), setsebool(8)