Security-Enhanced Linux secures the tftpd processes via flexible mandatory access control.
The tftpd processes execute with the tftpd_t SELinux type. You can check if you have these processes running by executing the ps command with the -Z qualifier.
ps -eZ | grep tftpd_t
The tftpd_t SELinux type can be entered via the tftpd_exec_t file type.
The default entrypoint paths for the tftpd_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 tftpd policy is very flexible allowing users to setup their tftpd processes in as secure a method as possible.
The following process types are defined for tftpd:
Note: semanage permissive -a tftpd_t can be used to make the process type tftpd_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. tftpd policy is extremely flexible and has several booleans that allow you to manipulate the policy and run tftpd with the tightest access possible.
If you want to allow tftp to read and write files in the user home directories, you must turn on the tftp_home_dir boolean. Disabled by default.
setsebool -P tftp_home_dir 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
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 tftpd policy is very flexible allowing users to setup their tftpd processes in as secure a method as possible.
The following port types are defined for tftpd:
Default Defined Ports: udp 69
The SELinux process type tftpd_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 tftpd policy is very flexible allowing users to setup their tftpd processes in as secure a method as possible.
STANDARD FILE CONTEXT
SELinux defines the file context types for the tftpd, if you wanted to store files with these types in a diffent paths, you need to execute the semanage command to specify alternate labeling and then use restorecon to put the labels on disk.
semanage fcontext -a -t tftpd_etc_t '/srv/mytftpd_content(/.*)?'
restorecon -R -v /srv/mytftpd_content
Note: SELinux often uses regular expressions to specify labels that match multiple files.
The following file types are defined for tftpd:
- Set files with the tftpd_etc_t type, if you want to store tftpd files in the /etc directories.
- Set files with the tftpd_exec_t type, if you want to transition an executable to the tftpd_t domain.
- Set files with the tftpd_var_run_t type, if you want to store the tftpd files under the /run or /var/run directory.
- Set files with the tftpdir_rw_t type, if you want to treat the files as tftpdir read/write content.
- Set files with the tftpdir_t type, if you want to treat the files as tftpdir data.
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.
If you want to share files with multiple domains (Apache, FTP, rsync, Samba), you can set a file context of public_content_t and public_content_rw_t. These context allow any of the above domains to read the content. If you want a particular domain to write to the public_content_rw_t domain, you must set the appropriate boolean.
Allow tftpd servers to read the /var/tftpd directory by adding the public_content_t file type to the directory and by restoring the file type.
semanage fcontext -a -t public_content_t "/var/tftpd(/.*)?"
restorecon -F -R -v /var/tftpd
Allow tftpd servers to read and write /var/tftpd/incoming by adding the public_content_rw_t type to the directory and by restoring the file type. You also need to turn on the tftpd_anon_write boolean.
semanage fcontext -a -t public_content_rw_t "/var/tftpd/incoming(/.*)?"
restorecon -F -R -v /var/tftpd/incoming
setsebool -P tftpd_anon_write 1
If you want to allow tftp to modify public files used for public file transfer services., you must turn on the tftp_anon_write boolean.
setsebool -P tftp_anon_write 1
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), tftpd(8), semanage(8), restorecon(8), chcon(1), sepolicy(8), setsebool(8)