Devices

A device is a peripheral, physically connected or logically known to a processor and capable of receiving, storing, or transmitting data. A device can be physical, like a disk or terminal, or it can be virtual, like a mailbox or pseudoterminal. Virtual devices are implemented entirely in software. Virtual terminals are considered LOCAL devices. They can be created over the network or on the local system.

Naming Rules

You can use physical, logical, or generic names to refer to devices. In addition, if your system is part of a clustered system, certain devices are accessible to all members of the cluster. They have the following formats:

Most physical device names consist of three parts:
- A device code (dd), which represents the hardware device type.
- A controller designator (c), which identifies the hardware controller to which the device is attached.
- The unit number (U), which uniquely identifies a device on a particular controller.
The maximum length of the device name field, including the controller and the unit number, is 15 characters.
Logical device names equate the somewhat cryptic physical device name to a short, meaningful name. You can use these logical device names, rather than the physical device names, to refer to devices.
A generic device name consists of the device code and omits the specific controller or unit number.
A cluster device name includes the name of the node to which the device is attached and the physical device name, separated by a dollar sign ($).

See the HP OpenVMS System Manager's Manual and the HP OpenVMS User's Manual for a full description of device names.

Types of Access

Devices can be shared and thus have concurrent users or be unshared and have a single user.

Shared devices support the following types of access:

Read	Gives you the right to read data from the device
Write	Gives you the right to write data to the device
Physical	Gives you the right to perform physical I/O operations to the device
Logical	Gives you the right to perform logical I/O operations to the device
Control	Gives you the right to change the protection elements and owner of the device

Unshared devices support only read, write, and control access. The device driver rather than the operating system's security policy defines the access requirements for other types of operations.

Access Requirements for I/O Operations

Access requirements for I/O operations on devices can be quite complex. The following list explains access requirements for typical operations:

Assigning a channel with $ASSIGN
Assigning a channel to a nonspooled, nonshareable device requires read access, write access, control access, or any combination. Assigning a channel to a shareable device has no access requirement.
Allocating a device with $ALLOC
Allocating any device with $ALLOC requires read, write, or control access.
$QIO to spooled devices
Access is handled as described for OpenVMS mounted volumes. See the next list item, $QIO to file-oriented devices.
$QIO to file-oriented devices: disks and tapes
With file-oriented devices, logical I/O and physical I/O functions have common elements. Any logical I/O function requires physical or logical access plus read access to read a block (READLBLK) or write access to write a block (WRITELBLK). Any physical I/O function requires physical access plus either read access to read a block (READPBLK) or write access to write a block (WRITEPBLK). Logical and physical I/O also require LOG_IO and PHY_IO privileges, respectively.
Beyond this, access requirements depend on how the volume is mounted:
- OpenVMS supported volumes
  Any virtual I/O to the volume has the same access requirements as the File or Volume class (see “Files” and “Volumes”).
- Volumes mounted foreign (/FOREIGN)
  Virtual read and write functions are converted to logical I/O. All other functions are not processed by the operating system and are sent to the device driver for processing. Physical I/O functions also require PHY_IO privilege.
- Devices without a mounted volume
  Access to devices without mounted volumes requires privilege.
$QIO to devices that are not file oriented
With non-file-oriented devices, OpenVMS converts virtual read and write I/O requests to logical I/O before processing them. Other kinds of access requests are not processed by OpenVMS; instead, the request is passed to the device driver for processing.
In general, access requirements for devices that are not file oriented depend on whether the device is shareable or nonshareable:
- Shareable devices
  With shareable devices, such as mailboxes, any virtual I/O function other than READVBLK/WRITEVBLK is handled by the system I/O driver program. Any logical I/O function requires privilege or logical access to the device. Any physical I/O function requires privilege or physical access to the device.
- Unshareable devices
  With unshareable devices, such as terminals or printers, the operating system checks only for read or write access to perform virtual and logical I/O functions. Any physical I/O function requires privilege.

Template Profile

The device class provides the following template profiles:

Template Name	Device Type	Owner UIC	Protection Code
BUS	DC$_BUS	[SYSTEM]	S:RWPL,O:RWPL,G,W
CARDREADER	DC$_CARD	[SYSTEM]	S:RWPL,O:RWPL,G,W
COMMUNICATION	DC$_SCOM	[SYSTEM]	S:RWPL,O:RWPL,G,W
DEFAULT		[SYSTEM]	S:RWPL,O:RWPL,G:RWPL,W:RWPL
DISK	DC$_DISK	[SYSTEM]	S:RWPL,O:RWPL,G:R,W
MAILBOX	DC$_MAILBOX	[SYSTEM]	S:RWPL,O:RWPL,G:RWPL,W:RWPL
PRINTER	DC$_LP	[SYSTEM]	S:RWPL,O:RWPL,G,W
REALTIME	DC$_REALTIME	[SYSTEM]	S:RWPL,O:RWPL,G:RWPL,W:RWPL
TAPE	DC$_TAPE	[SYSTEM]	S:RWPL,O:RWPL,G:R,W
TERMINAL	DC$_TERM	[SYSTEM]	S:RWPL,O:RWPL,G,W
WORKSTATION	DC$_WORKSTATION	[SYSTEM]	S:RWPL,O:RWPL,G:RWPL,W:RWPL

Setting Up Profiles for New Devices

A device usually derives its security profile from the template profile associated with its device type; however, the template is often modified. The following list describes how the operating system assigns a profile to different types of devices:

Devices created during system configuration
Devices introduced during system configuration with the system commands CONNECT and LOAD (for example, pseudodevices and workstations) take their profiles from the template appropriate for the device type.
Disks and tapes
Disk or tape devices take their profile from the DISK or TAPE template profile, respectively. Once the device is visible within a cluster, its profile, with any modifications, is retained across system restarts. Changes to the DISK or TAPE template profile after a device has its security profile do not apply to that device; therefore, it is necessary to reset the specific object profile by using the DCL command SET SECURITY (see “Modifying a Security Profile”).
Devices cloned from template devices
Devices cloned from template devices (for example, Ethernet devices) assume the security profile of the template device from which they are cloned. Template devices are loaded during the autoconfiguration process; at this time, their profile is taken from the profile template appropriate for the device.
Mailboxes
Mailbox devices assume a modified version of the MAILBOX template profile. The system modifies the template so the UIC of the creating process becomes the owner and the protection code is set to the value of the promsk argument to the Create Mailbox ($CREMBX) system service (provided the value is nonzero).
To maintain compatibility with earlier versions of the operating system, the MAILBOX template has a protection code of 0 (allowing all access). Some applications may need a more restrictive default than the template provides. If you do choose to restrict mailbox access, be aware that the more restrictive access can cause applications to fail in ways that are difficult to diagnose.

Terminals

Terminal devices assume a modified version of the TERMINAL template profile.

NOTE: In OpenVMS Version 7.2-1 and earlier, all pseudo-terminal (FT) device protection codes were set by the driver to (S:RWLP,O:RWLP,G,W). In OpenVMS Version 7.3 and later, only device FTA0 is set to this forced protection. This allows the system manager the option of modifying the FTA0 device protection later in the boot process. This new protection is inherited from FTA0 by any new FT devices created thereafter (as well as other settings originating from the SECURITY class DEVICE TERMINAL template profile, such as ACLs).

A system manager can modify FTA0 manually, or change the SYSTARTUP_VMS.COM command procedure. For example:

$ SET SECURITY/CLASS=DEVICE -
_$ /PROTECTION=(S:RWLP,O:RWLP,G:RW,W:R) FTA0:

If the device protection for FTA0 is left unmodified, the behavior is unchanged from versions of OpenVMS prior to Version 7.3. That behavior is that all terminals except FT pseudo-terminal devices inherit their device protection and other security characteristics from the TERMINAL template profile. All FTA pseudo-terminal devices inherit their protection from FTA0, which by default is set to (S:RWLP,O:RWLP,G,W). Other settings, such as ACLs, are inherited from the TERMINAL template profile. This ensures compatibility with existing applications.

When a user logs in on a terminal, the operating system modifies the profile so the owner becomes the UIC of the process logging in to the terminal. The original security profile for the terminal is restored when the user logs out.

Privilege Requirements

All logical or physical I/O to a spooled device requires privilege.

The LOG_IO privilege allows the user's process to execute the Queue I/O Request ($QIO) system service to perform logical-level I/O operations. LOG_IO privilege is also required for certain device-control functions, such as setting permanent terminal elements.

The PHY_IO privilege allows the user's process to execute the Queue I/O Request ($QIO) system service to perform physical-level I/O operations. The PHY_IO privilege also grants LOG_IO privilege.

To create a permanent mailbox or mark it for deletion requires PRMMBX privilege.

Kinds of Auditing Performed

The following types of events can be audited, provided the security administrator enables auditing for the appropriate event class:

Event Audited	When Audit Occurs
Access	For nonshareable devices, when the process calls $ASSIGN; for a shareable device, when the process calls $QIO
Creation	When a process creates a virtual device like a mailbox
Deletion	When a process deletes a virtual device like a mailbox

Permanence of the Object

The profile of clusterwide disks and tapes is stored in the object database VMS$OBJECTS.DAT, but other object profiles have to be reset each time the system starts up.