Access to NFS Mounted Directories in Trusted Extensions

By default, NFS-mounted file systems are visible at the label of the exported file system. If the file system is exported with read/write permissions, users at that label can write to the files. NFS mounts that are at a lower label than the user's current session are visible to the user, but cannot be written to. Even if a file system is shared with read/write permissions, the mounting system can write to it only at the label of the mount.

To make lower-level directories that are NFS-mounted visible to users in a higher-level zone, the administrator of the global zone on the NFS server must export the parent directory. The parent directory is exported at its label. On the client side, each zone must have the net_mac_aware privilege. By default, labeled zones include the net_mac_aware privilege in their limitpriv set.

• Server configuration – On the NFS server, you export the parent directory in a dfstab file. If the parent directory is in a labeled zone, the dfstab file must be modified in the labeled zone of the parent directory. The dfstab file for a labeled zone is visible only from the global zone. For the procedure, see How to Share Directories From a Labeled Zone.

• Client configuration – The net_mac_aware privilege must be specified in the zone configuration file that is used during initial zone configuration. So, a user who is permitted to view all lower-level home directories must have the net_mac_aware privilege in every zone, except the lowest zone. For an example, see How to NFS Mount Files in a Labeled Zone.

Example 17-1 Providing Access to Lower-Level Home Directories

On the home directory server, the administrator creates and modifies the /zone/labeled-zone/etc/dfs/dfstab file in every labeled zone. The dfstab file exports the /export/home directory with read/write permissions. Thus, when the directory is mounted at the same label, the home directory is writable. To export the /export/home directory of PUBLIC, the administrator creates a workspace at the PUBLIC label on the home directory server, and from the global zone, modifies the /zone/public/etc/dfs/dfstab file.

On the client, the administrator of the global zone checks that every labeled zone, except the lowest label, has the net_mac_aware privilege. This privilege permits the mount. This privilege can be specified by using the zonecfg command during zone configuration. The lower-level home directory can only be viewed. MAC protects the files in the directory from modification.

Home Directory Creation in Trusted Extensions

Home directories are a special case in Trusted Extensions. You need to make sure that the home directories are created in every zone that a user can use. Also, the home directory mount points must be created in the zones on the user's system. For NFS-mounted home directories to work correctly, the conventional location for directories, /export/home, must be used. In Trusted Extensions, the automounter has been modified to handle home directories in every zone, that is, at every label. For details, see Changes to the Automounter in Trusted Extensions.

Home directories are created when users are created. In Trusted Extensions, the Solaris Management Console (Console) is used to create users, so the Console creates the home directories. However, the Console creates the home directories in the global zone of the home directory server. On that server, the directories are mounted by LOFS. Home directories are automatically created by the automounter if they are specified as LOFS mounts.

However, the automounter cannot automatically create home directories on remote NFS servers. Either the user must first log in to the NFS server or administrative intervention is required. To create home directories for users, see Enable Users to Access Their Home Directories in Trusted Extensions.

Changes to the Automounter in Trusted Extensions

In Trusted Extensions, each label requires a separate home directory mount. The automount command has been modified to handle these labeled automounts. For each zone, the automounter, autofs, mounts an auto_home_zone-name file. For example, the following is the entry for the global zone in the auto_home_global file:

+auto_home_global
*       -fstype=lofs    :/export/home/&

When a zone that permits lower-level zones to be mounted is booted, the following occurs. The home directories of lower-level zones are mounted read only under /zone/<zone-name>/export/home. The auto_home_<zone-name> map specifies the /zone path as the source directory for an lofs remount onto /zone/<zone-name>/home/<username>.

For example, the following is an auto_home_public entry in an auto_home_zone-at-higher-label map that is generated from a higher-level zone:

+auto_home_public
*       -fstype=lofs    :/zone/public/export/home/&

The following is the corresponding entry in the public zone:

auto_home_public
*       -fstype=lofs    :/export/home/&

When a home directory is referenced and the name does not match any entries in the auto_home_<zone-name> map, the map tries to match this loopback mount specification. The software creates the home directory when the following two conditions are met:

1. The map finds the match of the loopback mount specification

2. The home directory name matches a valid user whose home directory does not yet exist in zone-name

For details on changes to the automounter, see the automount(1M) man page.