Document revision date: 15 July 2002

You can protect data on disk and magnetic tape media at the following levels:

Level of Protection	Description
Device level	For information about setting device protection characteristics, see the descriptions of the DCL commands INITIALIZE, MOUNT, SET DEVICES, SET SECURITY/PROTECTION, and SET VOLUME in Chapter 9 and in the OpenVMS DCL Dictionary. Refer to Chapter 8 for additional information about peripheral devices.
Volume level	The system provides protection for disk and tape volumes. For more information, see the following sections: Disk volume protection Section 9.4.1 Tape volume protection Section 9.4.2
File level	The system provides protection for disk files and directory files. For more information, see the following sections: Individual disk files Section 10.7.3 Directory files that reside on disk volumes Section 10.7.4

You can protect data residing on disk and tape volumes by using one or more of the following methods:

Type of Protection	For More Information
UIC-based protection codes	Chapter 12
Access control lists (ACLs)	Chapter 12
ISO 9660-formatted media protection	Section 9.4.2
ANSI-standard accessibility protection (magnetic tape only)	Section 9.4.2

For the most part, file protection is transparent. Tools exist, however, to adjust the protection of a file. You can set the protection or modify the ACL of a file if at least one of these statements is true:

• You own the file.
• You have control access to the file.
• You have SYSPRV privilege.
• The group part of your UIC is less than or equal to MAXSYSGROUP.
• You have GRPPRV and you have the same group UIC as the file.

You can display ownership and protection information with the commands and qualifiers shown in Table 10-2.

Table 10-2 DCL Commands to Display Ownership and Protection

Command	Use to Display
DIRECTORY/ACL filespec	ACL of file
DIRECTORY/OWNER_UIC filespec	UIC of owner of file
DIRECTORY/PROTECTION filespec	UIC-based protection of file
DIRECTORY/SECURITY	All of the above
DIRECTORY/FULL filespec	All of the above and other, nonsecurity information
SHOW DEVICES/FULL device-name	Device UIC and protection
SHOW PROCESS	Process UIC
SHOW PROTECTION	Default file protection
SHOW SECURITY	All of the above

Directory structures do not apply to tape volumes. However, you can use the DIRECTORY command to search for files on tape volumes. Section 10.9 describes how to access tape files for read and write operations and also explains the use of the DIRECTORY command for tapes.

The DCL command SHOW PROTECTION displays the current process default protection. This protection is applied to files created during your terminal session or to batch jobs, where defaults from directories or previously existing versions are not available.

The next example illustrates how you can use the SHOW PROTECTION command to display the default protection characteristics for disk files.

Example

$ SHOW PROTECTION SYSTEM=RWED, OWNER=RWED, GROUP=RE, WORLD=NO ACCESS

In this example, the SHOW PROTECTION command requests a display of the current protection defaults.

10.7.3 Protecting Disk Files

Each file on a disk has its own protection code, which is distinct from the protection that applies to the disk volume itself. Files residing on disk volumes have the access types shown in Table 10-3.

Table 10-3 Access Types with Disk File Protection

Access Type	Gives you the right to...
Read	Read, print, or copy a disk file. Read access automatically includes execute access to a specified file or group of files on disk.
Write	Write to or change the contents of a file, but not delete it. Write access allows modification of the file characteristics that describe the contents of the file.
Execute	Execute a file that contains an executable program image or DCL command procedure.
Delete	Delete the file. To delete a file, you must have delete access to the file and write access to the directory that contains the file.
Control	Change file characteristics, including the protection code and ACL. Special restrictions apply to changing the owner of a file.

If you do not define a protection code for a file when you create it, the system applies default protection. If a version of the file already exists, protection is taken from the previous version.

For a new file, the system determines protection in two major ways:

• If the directory where the file is to be cataloged has an associated access control entry (ACE) that specifies the default protection, the system uses the specified protection.
• If the directory does not have the default protection ACE, the system uses the default process protection. You establish the default process protection explicitly with the SET PROTECTION/DEFAULT command, or by default when you log in.

For disk volumes, each file on the volume can have a different protection associated with it. The SET SECURITY/PROTECTION command and other file-manipulating commands allow you to define the protection for individual files.

The following sections explain how to perform these tasks:

Task	Section
Set default disk file protection	Section 10.7.3.1
Set explicit disk file protection	Section 10.7.3.2
Modify disk file protection characteristics	Section 10.7.3.3

10.7.3.1 Setting Default Disk File Protection

A new file receives default UIC-based protection and the default access control entries (ACEs), if any, of its parent directory. A new version of an existing file receives the UIC-based protection and ACL of the previous version.

The protection of a renamed file is unchanged unless you use the RENAME/INHERIT command.

How to Change Default UIC Protection

The operating system provides each process with a default UIC-based protection of (S:RWED,O:RWED,G:RE,W). To change the default protection that is applied to files created by that process, enter the SET PROTECTION/DEFAULT command using the following format:

SET PROTECTION[=(code)]/DEFAULT

where:

code	Defines the protection to be applied to the specified files. If you omit the code, the access is set to the current default protection.

For example, if you place the following command in your login command procedure, you grant all processes read and execute access to any files that you subsequently create:

$ SET PROTECTION = (S:RWED,O:RWED,G:RE,W:RE)/DEFAULT

(Remember that you must execute the login command procedure for this command to take effect.)

10.7.3.2 Setting Explicit Disk File Protection

You can explicitly specify UIC-based protection for a new file with the /PROTECTION qualifier (valid with the BACKUP, COPY, RENAME, and CREATE commands), as shown in the following command line:

$ CREATE MAST12.TXT/PROTECTION=(S:RWED,O:RWED,G,W)

After a file is created and you have created an ACL for the file, you can modify the ACL and add as many ACEs to the ACL as you want. The protection specified by the ACL overrides the UIC protection of the file.

The following examples show how to check and specify protection codes.

Examples

1. $ SHOW PROTECTION SYSTEM=RWED, OWNER=RWED, GROUP=RE, WORLD=NO ACCESS

   
   The SHOW PROTECTION command displays the current default protection. In this example, the response shows the system default protection, which indicates that the system and owner have all types of access, group users have read and execute access, and world users have no access.

2. $ SHOW SECURITY IMAGES.DIR DBA1:[SADAMS]IMAGES.DIR;1 object of class FILE Owner: [SAM,SADAMS] Protection: (System: RWE, Owner: RWE, Group: RE, World: E) Access Control List: (IDENTIFIER=[SAM,SADAMS],ACCESS=READ+WRITE+EXECUTE+DELETE+CONTROL)

   
   In this example, the SHOW SECURITY command displays the current protection associated with the file IMAGES.DIR.

3. $ DIRECTORY/SECURITY IMAGES.DIR Directory DBA1:[SADAMS] IMAGES.DIR;1 [VMS,SADAMS] (RWE,RWE,RE,E) (IDENTIFIER=[VMS,SADAMS],ACCESS=READ+WRITE+EXECUTE+DELETE+CONTROL) Total of 1 file.

   
   In this example, the /SECURITY qualifier with the DIRECTORY command displays the current protection associated with the IMAGES.DIR file.

4. $ COPY/PROTECTION=(SYSTEM:RW,OWNER:RWED,GROUP:RW,WORLD) ABC.DAT XYZ.DAT

   
   In this example, the /PROTECTION qualifier specifies a protection code when the ABC.DAT file is copied to XYZ.DAT.

5. $ SET SECURITY/PROTECTION=(SYSTEM:RWE,OWNER:RWED,GROUP:RE,WORLD) ABC.DAT

   
   In this example, the SET SECURITY/PROTECTION command changes the protection for an existing file. The command gives the following instructions regarding the file ABC.DAT: system users have read, write, and execute access; the owner has read, write, execute, and delete access; group users have only read and execute access; world users have no access.
   Control access is implied and unchangeable for system and owner categories but not for group and world.

Table 10-4 shows the DCL commands that you can use to establish and modify the protection characteristics of files.

Table 10-4 DCL Commands to Modify File Protection Characteristics

Command	Description	For More Information
SET DIRECTORY	Modifies the characteristics of one or more directories. The directory protection can override the protection of individual files within the directory.	See Section 10.7.4.
SET FILE	Modifies the characteristics of one or more files, including the version limits on files.	See Section 10.7.3.3.2.
SET PROTECTION/DEFAULT	Sets the default UIC protection on files.	Refer to the OpenVMS Guide to System Security.
SET SECURITY	Modifies the security profile of an object. Such a profile contains the following characteristics: An access control list (ACL). A protection code, which defines access to objects based on the categories of system, owner, group, and world. An owner. The system uses the owner characteristic to interpret the protection code.	Refer to the OpenVMS Guide to System Security and the OpenVMS DCL Dictionary.
SET VOLUME	Changes the characteristics of one or more mounted Files-11 volumes. The /FILE_PROTECTION qualifier sets the default protection to be applied to all files on the specified disk volume.	See Section 9.4.1.2.

For a complete list of the command qualifiers and parameters applicable to each of these DCL commands, refer to the OpenVMS DCL Dictionary.

10.7.3.3.1 Changing File Protection Characteristics

To change or reset the protection characteristics of one or more files, use the following format:

SET SECURITY/PROTECTION = code file-spec[,...]

where:

code	Defines the protection to be applied to the specified files. You cannot omit the code.
file-spec	Specifies one or more files for which the protection is to be changed. A file name and file type are required. If you omit a version number, the protection is changed only for the highest existing version of the file. Wildcard characters are allowed.

The following examples show ways to change file protection.

Examples

1. $ DELETE INCOME.DAT;3 %DELETE-W-FILNOTDEL, error deleting DISK1:[SMITH]INCOME.DAT;3 -RMS-E-PRV, insufficient privilege or file protection violation $ SET SECURITY/PROTECTION=OWNER:D INCOME.DAT;3 $ DELETE INCOME.DAT;3

   
   In this example, the file INCOME.DAT;3 is protected against deletion. The SET SECURITY/PROTECTION command changes only the owner's delete access for the file INCOME.DAT;3. Now the owner can delete the file.

2. $ SET SECURITY/PROTECTION=(SYSTEM:R,OWNER:RWED,GROUP:RW) PAYROLL.LIS

   
   In this example, the SET SECURITY/PROTECTION command changes the protection codes applied to the PAYROLL.LIS file. To the file, the command gives the system read access; the owner has read, write, execute, and delete access; and users in the owner's group have read and write access.

You can use the DCL command SET FILE to modify the characteristics of one or more files or to assign an additional name, or alias, to a file. The following examples illustrate ways you can use the SET FILE command.

Examples

1. $ SET FILE/EXPIRATION_DATE=15-APR-2000:11:00 BATCH.COM;3

   
   This SET FILE command requests that the expiration date of the file BATCH.COM;3 be set to 11:00 a.m., April 15, 2000.

2. $ SET FILE/BEFORE=15-APR-00/ERASE_ON_DELETE PERSONNEL*.SAL

   
   This SET FILE command erases disk locations for files that are deleted with commands such as DELETE or PURGE when applied to all files that match the file specification PERSONNEL*.SAL and are dated before April 15, 2000.

3. $ SET FILE/OWNER_UIC=[DOCUMENTATION,GRAY]/VERSION_LIMIT=100 MYFILE.DAT

   
   This SET FILE command modifies the characteristics of the file MYFILE.DAT, changing the owner UIC and assigning a file version limit of 100. Note that the /OWNER_UIC qualifier requires SYSPRV or GRPPRV privilege for changing the ownership at the system or group level.

4. $ SET FILE OLD_FILENAME.DAT/ENTER=NEW_FILENAME.DAT

   
   This SET FILE command assigns an additional name, or alias (NEW_FILENAME.DAT), to the file OLD_FILENAME.DAT. Both the original name and the alias refer to the same file. For this reason, be careful when you delete files with aliases. To keep the file, but to remove one of its names, use the /REMOVE qualifier with the SET FILE command. You cannot use wildcards in the file name. (Refer to the OpenVMS DCL Dictionary for details.)

Each directory has a protection associated with it. Directory protection can override the protection of individual files within the directory. For example, if a directory denies world access, world users cannot look up files in that directory even though the files permit world access.

For directory protection, you can use the access types shown in Table 10-5.

Table 10-5 Access Types for Directory Protection

Access Type	Gives you the right to...
Read	Examine, print, or copy a file. If you have read access to a directory, you can display the contents of the directory with the DIRECTORY command. For example, if you have read access to the directory [JONES], you can enter the following command: $ DIRECTORY [JONES] This command displays the files contained in the [JONES] directory. With read access, you can access any file listed in the directory, unless the protection on that file denies you access. If the protection applied to the whole directory denies you read access, then you cannot access even those files in the directory that permit access to users in your group.
Write	Modify or write to a directory. However, you must have both read and write access to a directory to create files in the directory, to rename files in the directory, or to perform any file operation that involves changes to the directory file.
Execute	Access files by name but not list all the entries in a directory (that is, to use specific or implied wildcards) when applied to directories. For example, assume that you have execute access to the [JONES] directory, and you enter the following command: $ DIRECTORY [JONES] The system responds with an error message of "insufficient privilege or file protection violation" and does not list the files in the [JONES] directory. However, if you know that the file DATAFILE.DAT resides in the [JONES] directory, you can enter the following command: $ TYPE [JONES]DATAFILE.DAT The system displays the contents of the file. Thus, with execute access, you can perform some, but not all, of the operations that you can with read access. (Access to individual files is still controlled by their file protection.) As another example, to display the contents of the EXPENSES.DAT file, you must have read or execute access to each directory in the directory tree, that is, to the JONES, REPORTS, and JUNE directories: $ TYPE [JONES.REPORTS.JUNE]EXPENSES.DAT
Delete	Delete a directory file. You must remove all entries from a directory before you can delete the directory file. When you create a directory with the CREATE/DIRECTORY command, you do not, by default, get delete access. If you want to be able to delete a directory file, you must use the DCL command SET SECURITY/PROTECTION to explicitly assign delete access to the owner category.
Control	Change the characteristics of a directory.

Using UIC Directory Protection

You cannot completely protect a file without applying at least the same protection to the directory in which the file resides. For example, if you deny a user all access to a file but allow that user read access to the file's directory, the user cannot access the contents of the file but can see that it exists. Conversely, a user allowed access to a file and denied access to the file's directory (or one of the parent directories) cannot see that the file exists.

By default, top-level directories receive UIC-based protection (S:RWE,O:RWE,G:RE,W:E) and no ACL. A newly created subdirectory receives the same protection as its parent directory, but delete access is removed from all categories.

Guidelines for specifying UIC-based protection on a directory follow.

• To specify UIC-based protection explicitly when creating a directory, use the /PROTECTION qualifier with the CREATE/DIRECTORY command. You cannot specify an ACL for the directory before you create the directory.
• To change the UIC-based protection of an existing directory, use the SET SECURITY/PROTECTION command for the directory file.
• You can limit but not prohibit directory access by specifying execute access but not read access. Execute access on a directory permits you to examine and read files that you know are in the directory (that is, you know the file specifications) but prevents you from displaying a list of the files in the directory.

The following sections explain how to change directory protection characteristics and default ACL protection.

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