Security-Enhanced Linux secures the prelink processes via flexible mandatory access control.
The prelink processes execute with the prelink_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.
For example:
ps -eZ | grep prelink_t
The prelink_t SELinux type can be entered via the prelink_exec_t file type.
The default entrypoint paths for the prelink_t domain are the following:
You can see the context of a process using the -Z option to psP Policy governs the access confined processes have to files. SELinux prelink policy is very flexible allowing users to setup their prelink processes in as secure a method as possible.
The following process types are defined for prelink:
prelink_t, prelink_cron_system_t
Note: semanage permissive -a prelink_t can be used to make the process type prelink_t permissive. SELinux does not deny access to permissive process types, but the AVC (SELinux denials) messages are still generated.
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. Disabled by default.
setsebool -P deny_execmem 1
If you want to allow all domains to execute in fips_mode, you must turn on the fips_mode boolean. Enabled by default.
setsebool -P fips_mode 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. Disabled 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 prelink_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.
file_type
all files on the system
You can see the context of a file using the -Z option to lsP Policy governs the access confined processes have to these files. SELinux prelink policy is very flexible allowing users to setup their prelink processes in as secure a method as possible.
EQUIVALENCE DIRECTORIES
prelink policy stores data with multiple different file context types under the /var/log/prelink directory. If you would like to store the data in a different directory you can use the semanage command to create an equivalence mapping. If you wanted to store this data under the /srv dirctory you would execute the following command:
semanage fcontext -a -e /var/log/prelink /srv/prelink
restorecon -R -v /srv/prelink
STANDARD FILE CONTEXT
SELinux defines the file context types for the prelink, if you wanted to store files with these types in a diffent paths, you need to execute the semanage command to sepecify alternate labeling and then use restorecon to put the labels on disk.
semanage fcontext -a -t prelink_var_lib_t '/srv/myprelink_content(/.*)?'
restorecon -R -v /srv/myprelink_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for prelink:
prelink_cache_t
- Set files with the prelink_cache_t type, if you want to store the files under the /var/cache directory.
prelink_cron_system_exec_t
- Set files with the prelink_cron_system_exec_t type, if you want to transition an executable to the prelink_cron_system_t domain.
prelink_exec_t
- Set files with the prelink_exec_t type, if you want to transition an executable to the prelink_t domain.
prelink_log_t
- Set files with the prelink_log_t type, if you want to treat the data as prelink log data, usually stored under the /var/log directory.
prelink_tmp_t
- Set files with the prelink_tmp_t type, if you want to store prelink temporary files in the /tmp directories.
prelink_tmpfs_t
- Set files with the prelink_tmpfs_t type, if you want to store prelink files on a tmpfs file system.
prelink_var_lib_t
- Set files with the prelink_var_lib_t type, if you want to store the prelink files under the /var/lib directory.
Note: File context can be temporarily modified with the chcon command. If you want to permanently change the file context you need to use the semanage fcontext command. This will modify the SELinux labeling database. You will need to use restorecon to apply the labels.
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.