By Glenn Faden on Dec 28, 2012
As 2012 comes to a close, I thought it would be a good time to look back at some of the changes that have been made to the Trusted Extensions features in Oracle Solaris.
A Brief History
Oracle Solaris was one of the first systems to provide multilevel security, including the first multilevel desktops and thin clients. Security labels first became a bundled feature in Oracle Solaris 10 update 3. This label-based security policy is referred to as Trusted Extensions. Previously that technology was only available via a separate version of the Solaris 8 operating system, called Trusted Solaris. But the Trusted Extensions technology is not simply a port of Trusted Solaris. Instead, it is based on a new architecture, in which labeled zones provide a transparent implementation of multilevel security. The virtualization provided by zones simplifies the deployment of multiple instances of applications at each label, without having to customize their configurations. However, the initial release lacked some of the flexibility and scalability inherent in Trusted Solaris 8.
Oracle Solaris 11.0
Zones and Networking
In Oracle Solaris 11.0, a new virtualized network stack provided greater isolation for the management of labeled networks. For example, each zone could be configured with its own DHCP server, IP routers, and name servers. A new labeled zone brand was introduced to distinguish the label-specific characteristics from the default solaris brand. A new administrative command, tncfg(1M), was provided to simplify the management of labeled zones and networks, including the option to maintain the network labeling policy in an LDAP directory. The txzonemgr GUI was enhanced to provide point and click interfaces for all common administrative functions.
Another major enhancement in Oracle Solaris 11.0 was labeled support for ZFS filesystems. To improve the robustness of the mandatory policy, each ZFS filesystem is now automatically and persistently labeled when it is initially mounted into a labeled zone. Once labeled, the system prevents subsequent attempts to mount the filesystem read-write by a zone with a different label. Read-only mounts require that the zone's label dominates the filesystem's label. The label attributes are preserved by the ZFS send and clone operations.
In addition, each labeled zone can now be configured as an NFS server. Previously, only the global zone could share filesystems, including those belonging to labeled zones. By default, a labeled zone NFS server can only serve clients whose label matches that of the zone. However, each zone can be configured by the global zone administrator to accept read-only requests from clients which dominate the zone's label. This is done by assigning the multilevel port attribute to the NFS service port for the zone.
The multilevel desktop was also enhanced in Oracle Solaris 11.0. The CDE login manager was replaced by the GNOME session manager, including several GNOME dialogs related to labeling. The Device Manager was enhanced to work the Nautilus file manager and the Hardware Abstraction Layer, HAL. As a result, additional media such as DVDs, and filesystems such as UDFS can be mounted via the Trusted Path, and their contents are automatically displayed in labeled instances of Nautilus.
Oracle Solaris 11.1
The first update to Oracle Solaris 11 was delivered last autumn. It provides even greater flexibility in the configuration and application of labels.
Zones and Networking
Previously each labeled zone was required to have a unique label, but this restriction prevented isolating related service tiers, like databases and web services into separate zones. Now such services can be distributed among multiple zones which can share the same label, providing that such zones are configured with the exclusive IP stack option. The multilevel desktop only exposes a single zone for each label, which is referred to as the primary labeled zone. Thus, the end-user need not be aware of these secondary labeled zones.
The policy for associating labels with network clients has been extended, as well. Previously, labels were associated with unlabeled hosts based on the IP address of the client. Since labeled systems are often connected to multiple networks, the previous policy required that all the hosts on these various networks had unique IP addresses. The new extended policy provides the option to derive client labels based on the network interface on which their packets arrive. Therefore, the IP addresses only have to be unique for each network interface. The policy applies to both physical and virtual interfaces, and supports the use of VLAN tags to isolate network traffic on a single wire.
For communication between two labeled systems, labels can be transmitted using the IP option header. For IPv4 packets the labels are transmitted using the Commercial IP Security Option (CIPSO). For IPv6 packets, Trusted Extensions has been using a non-standard variant of CIPSO, which was disabled by default. Now, IPv6 labels are transmitted using a new standard protocol, Common Architecture Label IPv6 Security Option (CALIPSO), which is enabled by default.
Previously all ZFS datasets were treated as single-level filesystems. A new ZFS option, multilevel, can now be specified when creating new filesystems. When this option is specified, each file and directory in the filesystem can be individually and persistently labeled. A mandatory labeling policy is enforced to ensure that users cannot observe portions of the filesystem for which they are not cleared. For example, the label of each directory must not dominate any of its children. Similarly, only empty directories can be relabeled, and their new labels must dominate their parent directory.
Since the labels are maintained as ZFS attributes, upgrading and downgrading of files and directories is instantaneous. However, the system prevents the relabeling of files that are currently in use. In addition, mandatory polices apply to both users and their processes associated with labeled zones. Only processes asserting the appropriate upgrade or downgrade privileges may relabel files or directories, and the specified labels must not conflict with the non-decreasing policy for pathname traversal.
Users must be cleared for both the existing and specified label, and their associated zone must have been configured with the required upgrade and/or downgrade privilege. This can be managed using usermod(1M), by assigning the Object Label Management rights profile to the user and setting the user's clearance.
Multilevel ZFS filesystems must be created and mounted within the global zone, by a user who has assumed the root role. However, such filesystems can be made available to labeled zones via loopback mounts, specified via zonecfg(1M). By default, such mounts are read-write. Additionally the required labeling privileges can also be assigned to zones via zonecfg(1M).
Multilevel filesystems can also be shared via NFS. Multilevel shares must be configured from within the global zone, and the multilevel attribute must be associated with the NFS port in the global zone. Clients connecting to this NFS service can only observe and open files that are dominated by their network label. NFS clients are not permitted to relabel files or directories.
The Common UNIX Printing System (CUPS), has been enhanced to display file labels on printed output. These labels appear as headers and footers on each body page. In addition, special banner and trailer pages are generated for each print job to facilitate proper dissemination of labeled material. The format of these pages is identical to what was generated by the LP print system in Oracle Solaris 10.
Multilevel printer servers can be configured in the global zone, and single-level printer servers can be configured in labeled zones. Cascade printing, in which a labeled zone proxies print requests from a remote client to the global zone print service, is also supported.
A new release of the Sun Ray Software will support Oracle Solaris 11.1, and the multilevel desktop features of Trusted Extensions.
Oracle Solaris 11 is in official In Evaluation status under the Canadian Common Criteria Scheme at Evaluation Assurance Level (EAL) 4 Augmented by Flaw Remediation. The evaluation is being conducted against the Operating System Protection Profile (OS PP) and includes the following four extended packages. (1) Advanced Management (AM), (2) Extended Identification and Authentication (EIA), (3) Labeled Security (LS), and (4) Virtualization (VIRT).