SELinux Labeled NFS Support
The Linux Kernel has grown support for passing SELinux labels between a client and server using NFS.
- Email: <firstname.lastname@example.org>
- Targeted release: [Fedora 20]
- Last updated: Jul 15 2013
- Percentage of completion: 90%
- selinux-policy fixes are in Fedora 20.
- Labeled NFS Support is in 3.11.0-0.rc0.git7.1.fc20.x86_64 kernel
- nfs-utils support
- mount support
We have always needed to treat NFS mounts with a single label usually something like nfs_t. Or at best allow an administrator to override the default with a label using the mount --context option. With this change we have lots of different Labels supported on an NFS share.
Benefit to Fedora
There are two huge benefits for Fedora, in that currently we can not differentiate different labels on a single NFS mount point. Applications like Secure Virtualization as launched by libvirt, can not set the label of an image file on an NFS share, so sVirt separation is severely weakened. Similarly if you setup home directories on an NFS share, then any confined application that needs to write a file in a home directory now can write any file on an NFS Share.
With labeled NFS this vulnerability goes away.
Turn on Labeled NFS in the Fedora Kernel, Fix any policy issues that arise because of this. I believe this is mainly a testing issue, and that the functionality is comeplet.
How To Test
Do to a bug in nfs-utils:
- Server Side
Start/Stop nfs server.
systemctl start nfs systemctl stop nfs
Set the version
echo "+4.2" > /proc/fs/nfsd/versions
Start Server Again
systemctl start nfs
- Client Side
mount -o v4.2 server:mntpoint localmountpoint
There are many different scenarios that have to be tested with this new functionality.
Basically with Labeled NFS we need to test with client and servers supporting LNFS and SELinux
- SELinux Client LNFS - SELinux Server LNFS
- SELinux Client LNFS - SELinux Server No LNFS
- SELinux CLient LNFS - Server LNFS
- SELinux CLient LNFS - Server No LNFS
- Client LNFS - SELinux Server LNFS
- Client LNFS - SELInux Server No LNFS
- Client LNFS - Server LNFS
- Client LNFS - Server no LNFS
- Client no LNFS - SELinux Server LNFS
- Client no LNFS - SELInux Server No LNFS
- Client no LNFS - Server LNFS
- Client no LNFS - Server no LNFS
Also need testing on three way. IE You need two clients that support SELinux CLient NFS and change the label on one client, and make sure the other client sees the change.
We can continue using what we always did, all clients labeled the same