System Administration Guide: Security Services

Device Protection (Reference)

Devices in the Solaris OS are protected by device policy. Peripheral devices can be protected by device allocation. Device policy is enforced by the kernel. Device allocation is optionally enabled, and is enforced at the user level.

Device Policy Commands

Device management commands administer the device policy on local files. Device policy can include privilege requirements. Only superuser or a role of equivalent capabilities can manage devices.

The following table lists the device management commands.

Table 4–1 Device Management Commands


Command	Purpose	Man Page
`devfsadm`	Administers devices and device drivers on a running system. Also loads device policy. The `devfsadm` command enables the cleanup of dangling `/dev` links to disk, tape, port, audio, and pseudo devices. Devices for a named driver can also be reconfigured.	devfsadm(1M)
`getdevpolicy`	Displays the policy associated with one or more devices. This command can be run by any user.	getdevpolicy(1M)
`add_drv`	Adds a new device driver to a running system. Contains options to add device policy to the new device. Typically, this command is called in a script when a device driver is being installed.	add_drv(1M)
`update_drv`	Updates the attributes of an existing device driver. Contains options to update the device policy for the device. Typically, this command is called in a script when a device driver is being installed.	update_drv(1M)
`rem_drv`	Removes a device or device driver.	rem_drv(1M)

Device Allocation

Device allocation can protect your site from loss of data, computer viruses, and other security breaches. Unlike device policy, device allocation is optional. Devices are not allocatable until the bsmconv script is run. Device allocation uses authorizations to limit access to allocatable devices.

Components of Device Allocation

The components of the device allocation mechanism are as follows:

The allocate, deallocate, dminfo, and list_devices commands. For more information, see Device Allocation Commands.
Device-clean scripts for each allocatable device.

These commands and scripts use the following local files to implement device allocation:

The /etc/security/device_allocate file. For more information, see the device_allocate(4) man page.
The /etc/security/device_maps file. For more information, see the device_maps(4) man page.
A lock file, in the /etc/security/dev directory, for each allocatable device.
The changed attributes of the lock files that are associated with each allocatable device.

Note –

The /etc/security/dev directory might not be supported in future releases of the Solaris OS.

Device Allocation Commands

With uppercase options, the allocate, deallocate, and list_devices commands are administrative commands. Otherwise, these commands are user commands. The following table lists the device allocation commands.

Table 4–2 Device Allocation Commands


Command	Purpose	Man Page
`bsmconv`	Creates databases to handle device allocation. Also enables the auditing service. You must be superuser or in the Primary Administrator role.	bsmconv(1M)
`dminfo`	Searches for an allocatable device by device type, by device name, and by full path name.	dminfo(1M)
`list_devices`	Lists the status of allocatable devices. Lists all the device-special files that are associated with any device that is listed in the `device_maps` file.	list_devices(1)
`list_devices -U`	Lists the devices that are allocatable or allocated to the specified user ID. This option allows you to check which devices are allocatable or allocated to another user. You must have the `solaris.device.revoke` authorization.
`allocate`	Reserves an allocatable device for use by one user. By default, a user must have the `solaris.device.allocate` authorization to allocate a device. You can modify the `device_allocate` file to not require user authorization. Then, any user on the system can request the device to be allocated for use.	allocate(1)
`deallocate`	Removes the allocation reservation from a device.	deallocate(1)

Authorizations for the Allocation Commands

By default, users must have the solaris.device.allocate authorization to reserve an allocatable device. To create a rights profile to include the solaris.device.allocate authorization, see How to Authorize Users to Allocate a Device.

Administrators must have the solaris.device.revoke authorization to change the allocation state of any device. For example, the -U option to the allocate and list_devices commands, and the -F option to the deallocate command require the solaris.device.revoke authorization.

For more information, see Commands That Require Authorizations.

Allocate Error State

A device is put in an allocate error state when the deallocate command fails to deallocate, or when the allocate command fails to allocate. When an allocatable device is in an allocate error state, then the device must be forcibly deallocated. Only superuser or a role with the Device Management rights profile or the Device Security rights profile can handle an allocate error state.

The deallocate command with the -F option forces deallocation. Or, you can use allocate -U to assign the device to a user. Once the device is allocated, you can investigate any error messages that appear. After any problems with the device are corrected, you can forcibly deallocate it.

`device_maps` File

Device maps are created when you set up device allocation. A default /etc/security/device_maps file is created by the bsmconv command when the auditing service is enabled. This initial device_maps file can be customized for your site. The device_maps file includes the device names, device types, and device-special files that are associated with each allocatable device.

The device_maps file defines the device-special file mappings for each device, which in many cases is not intuitive. This file allows programs to discover which device-special files map to which devices. You can use the dminfo command, for example, to retrieve the device name, the device type, and the device-special files to specify when you set up an allocatable device. The dminfo command uses the device_maps file to report this information.

Each device is represented by a one-line entry of the form:

device-name:device-type:device-list

Example 4–14 Sample `device_maps` Entry

The following is an example of an entry in a device_maps file for a diskette drive, fd0:

fd0:\
        fd:\
        /dev/diskette /dev/rdiskette /dev/fd0a /dev/rfd0a \
/dev/fd0b /dev/rfd0b /dev/fd0c /dev/fd0 /dev/rfd0c /dev/rfd0:\

Lines in the device_maps file can end with a backslash (\) to continue an entry on the next line. Comments can also be included. A pound sign (#) comments all subsequent text until the next newline that is not immediately preceded by a backslash. Leading and trailing blanks are allowed in any field. The fields are defined as follows:

device-name: Specifies the name of the device. For a list of current device names, see How to View Allocation Information About a Device.
device-type: Specifies the generic device type. The generic name is the name for the class of devices, such as st, fd, or audio. The device-type field logically groups related devices.
device-list: Lists the device-special files that are associated with the physical device. The device-list must contain all of the special files that allow access to a particular device. If the list is incomplete, a malevolent user can still obtain or modify private information. Valid entries for the device-list field reflect the device files that are located in the /dev directory.

`device_allocate` File

An initial /etc/security/device_allocate file is created by the bsmconv command when the auditing service is enabled. This initial device_allocate file can be used as a starting point. You can modify the device_allocate file to change devices from allocatable to nonallocatable, or to add new devices. A sample device_allocate file follows.

st0;st;;;;/etc/security/lib/st_clean
fd0;fd;;;;/etc/security/lib/fd_clean
sr0;sr;;;;/etc/security/lib/sr_clean
audio;audio;;;*;/etc/security/lib/audio_clean

An entry in the device_allocate file does not mean that the device is allocatable, unless the entry specifically states that the device is allocatable. In the sample device_allocate file, note the asterisk (*) in the fifth field of the audio device entry. An asterisk in the fifth field indicates to the system that the device is not allocatable. Therefore, the device cannot be used. Other values or no value in this field indicates that the device can be used.

In the device_allocate file, each device is represented by a one-line entry of the form:

device-name;device-type;reserved;reserved;auths;device-exec

Lines in the device_allocate file can end with a backslash (\) to continue an entry on the next line. Comments can also be included. A pound sign (#) comments all subsequent text until the next newline that is not immediately preceded by a backslash. Leading and trailing blanks are allowed in any field. The fields are defined as follows:

device-name: Specifies the name of the device. For a list of current device names, see How to View Allocation Information About a Device.
device-type: Specifies the generic device type. The generic name is the name for the class of devices, such as st, fd, and sr. The device-type field logically groups related devices. When you make a device allocatable, retrieve the device name from the device-type field in the device_maps file.
reserved: Sun reserves the two fields that are marked reserved for future use.
auths: Specifies whether the device is allocatable. An asterisk (*) in this field indicates that the device is not allocatable. An authorization string, or an empty field, indicates that the device is allocatable. For example, the string solaris.device.allocate in the auths field indicates that the solaris.device.allocate authorization is required to allocate the device. An at sign (@) in this file indicates that the device is allocatable by any user.
device-exec: Supplies the path name of a script to be invoked for special handling, such as cleanup and object-reuse protection during the allocation process. The device-exec script is run any time that the device is acted on by the deallocate command.

For example, the following entry for the sr0 device indicates that the CD-ROM drive is allocatable by a user with the solaris.device.allocate authorization:

sr0;sr;reserved;reserved;solaris.device.allocate;/etc/security/lib/sr_clean

You can decide to accept the default devices and their defined characteristics. After you install a new device, you can modify the entries. Any device that needs to be allocated before use must be defined in the device_allocate and device_maps files for that device's system. Currently, cartridge tape drives, diskette drives, CD-ROM drives, and audio chips are considered allocatable. These device types have device-clean scripts.

Note –

Xylogics tape drives or Archive tape drives also use the st_clean script that is supplied for SCSI devices. You need to create your own device-clean scripts for other devices, such as modems, terminals, graphics tablets, and other allocatable devices. The script must fulfill object-reuse requirements for that type of device.

Device-Clean Scripts

Device allocation satisfies part of what is called the object reuse requirement. The device-clean scripts address the security requirement that all usable data be purged from a physical device before reuse. The data is cleared before the device is allocatable by another user. By default, cartridge tape drives, diskette drives, CD-ROM drives, and audio devices require device-clean scripts. The Solaris OS provides the scripts. This section describes what device-clean scripts do.

Device-Clean Script for Tapes

The st_clean device-clean script supports three tape devices:

SCSI ¼-inch tape
Archive ¼-inch tape
Open-reel ½-inch tape

The st_clean script uses the rewoffl option to the mt command to clean up the device. For more information, see the mt(1) man page. If the script runs during system boot, the script queries the device to determine if the device is online. If the device is online, the script determines if the device has media in it. The ¼-inch tape devices that have media in them are placed in the allocate error state. The allocate error state forces the administrator to manually clean up the device.

During normal system operation, when the deallocate command is executed in interactive mode, the user is prompted to remove the media. Deallocation is delayed until the media is removed from the device.

Device-Clean Scripts for Diskettes and CD-ROM Drives

The following device-clean scripts are provided for diskettes and CD-ROM drives:

fd_clean script – Is a device-clean script for diskettes.
sr_clean script – Is a device-clean script for CD-ROM drives.

The scripts use the eject command to remove the media from the drive. If the eject command fails, the device is placed in the allocate error state. For more information, see the eject(1) man page.

Device-Clean Script for Audio

Audio devices are cleaned up with an audio_clean script. The script performs an AUDIO_GETINFO ioctl system call to read the device. The script then performs an AUDIO_SETINFO ioctl system call to reset the device configuration to the default.

Writing New Device-Clean Scripts

If you add more allocatable devices to the system, you might need to create your own device-clean scripts. The deallocate command passes a parameter to the device-clean scripts. The parameter, which is shown here, is a string that contains the device name. For more information, see the device_allocate(4) man page.

clean-script -[I|i|f|S] device-name

Device-clean scripts must return “0” for success and greater than “0” for failure. The options -I, -f, and -S determine the running mode of the script:

-I: Is needed during system boot only. All output must go to the system console. Failure or inability to forcibly eject the media must put the device in the allocate error state.
-i: Similar to the -I option, except that output is suppressed.
-f: Is for forced cleanup. The option is interactive and assumes that the user is available to respond to prompts. A script with this option must attempt to complete the cleanup if one part of the cleanup fails.
-S: Is for standard cleanup. The option is interactive and assumes that the user is available to respond to prompts.