Security-Enhanced Linux secures the snmpd processes via flexible mandatory access control.
The snmpd processes execute with the snmpd_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.
ps -eZ | grep snmpd_t
The snmpd_t SELinux type can be entered via the snmpd_exec_t file type.
The default entrypoint paths for the snmpd_t domain are the following:
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 snmpd policy is very flexible allowing users to setup their snmpd processes in as secure a method as possible.
The following process types are defined for snmpd:
Note: semanage permissive -a snmpd_t can be used to make the process type snmpd_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. snmpd policy is extremely flexible and has several booleans that allow you to manipulate the policy and run snmpd with the tightest access possible.
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
SELinux defines port types to represent TCP and UDP ports.
You can see the types associated with a port by using the following command:
semanage port -l
Policy governs the access confined processes have to these ports. SELinux snmpd policy is very flexible allowing users to setup their snmpd processes in as secure a method as possible.
The following port types are defined for snmpd:
Default Defined Ports: tcp 199,1161,161-162 udp 161-162
The SELinux process type snmpd_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.
SELinux requires files to have an extended attribute to define the file type.
You can see the context of a file using the -Z option to lsbP
Policy governs the access confined processes have to these files. SELinux snmpd policy is very flexible allowing users to setup their snmpd processes in as secure a method as possible.
snmpd policy stores data with multiple different file context types under the /var/run/snmpd 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 directory you would execute the following command:
semanage fcontext -a -e /var/run/snmpd /srv/snmpd
restorecon -R -v /srv/snmpd
STANDARD FILE CONTEXT
SELinux defines the file context types for the snmpd, 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 snmpd_var_lib_t '/srv/mysnmpd_content(/.*)?'
restorecon -R -v /srv/mysnmpd_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for snmpd:
- Set files with the snmpd_exec_t type, if you want to transition an executable to the snmpd_t domain.
- Set files with the snmpd_initrc_exec_t type, if you want to transition an executable to the snmpd_initrc_t domain.
- Set files with the snmpd_log_t type, if you want to treat the data as snmpd log data, usually stored under the /var/log directory.
- Set files with the snmpd_var_lib_t type, if you want to store the snmpd files under the /var/lib directory.
/var/agentx(/.*)?, /var/net-snmp(/.*), /var/lib/snmp(/.*)?, /var/net-snmp(/.*)?, /var/lib/net-snmp(/.*)?, /var/spool/snmptt(/.*)?, /usr/share/snmp/mibs/.index
- Set files with the snmpd_var_run_t type, if you want to store the snmpd files under the /run or /var/run directory.
/var/run/snmpd(/.*)?, /var/run/net-snmp(/.*)?, /var/run/snmpd.pid
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 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 port can also be used to manipulate the port definitions
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), snmpd(8), semanage(8), restorecon(8), chcon(1), sepolicy(8), setsebool(8)