Updated: 11 December 1998

OpenVMS Guide to System Security

This chapter explains how you give users access to a system by assigning user accounts and passwords. Descriptions are based on the security needs of a commercial installation with average security needs, where accounts require protection. Descriptions of above-average security needs are also noted. Refer to Chapter 8 for information on controlling access to system data and resources. See Chapter 6 and Chapter 9 for information on auditing user actions.

The Authorize utility (AUTHORIZE) is the primary tool for establishing accounts and passwords. See the OpenVMS System Management Utilities Reference Manual: A--L for a description of the utility.

7.1 Defining Times and Conditions for System Access

The level of system access a user enjoys depends on your site requirements, that user's role in the organization, and your management of his or her account. A site with low security requirements and plenty of system resources may allow access at any time of day whereas a site with moderate security requirements may limit logins to daytime hours and permit dialup or network connections only to a subset of users.

Using the Authorize utility, you control when and how users can access the system. Table 7-1 identifies the applicable qualifiers.

Table 7-1 Authorize Qualifiers Controlling Login Times and Conditions

Categories	Qaulifier	Description
Time of day	/ACCESS	By default, a user has full access every day. By specifying an access time, you prevent access at all other times. Identify hours on primary days with the keyword PRIMARY; identify hours on secondary days with the keyword SECONDARY.
	/DIALUP	Specifies hours of access permitted for dialup logins.
	/LOCAL	Specifies hours of access for interactive logins from local terminals.
Days of week	/PRIMEDAYS	Defines the primary and secondary days of the week for logging in.
Mode of operation	/BATCH	Specifies the hours of access permitted for batch jobs.
	/INTERACTIVE	Specifies the hours of access for interactive logins.
	/NETWORK	Specifies the hours of access permitted for network batch jobs.
	/REMOTE	Specifies hours during which access is permitted for interactive logins from network remote terminals (with the DCL command SET HOST).
Allocation of resources	/DEVICE	Specifies the name of the user's default device at login.
	/DIRECTORY	Specifies the name of the user's default directory at login.
Validity of account	/EXPIRATION	Specifies the expiration date and time of the account.
	/FLAGS=DISUSER	Disables the account so the user cannot log in.
External authentication	/FLAGS=EXTAUTH	Specifies that the user is externally authenticated.

7.1.1 Restricting Work Times

AUTHORIZE qualifiers let you restrict system use to certain days of the week and certain periods of the day. Restricting work times is useful to better balance the workload on your system. Restricting access to accounts is also an effective way of preventing unauthorized use of the system outside of normal working hours.

Define primary and secondary days of the week with the /PRIMEDAYS qualifier, or conform to the default where primary days are Monday through Friday and secondary days are Saturday and Sunday. For example, to modify the defaults for a user who works Tuesday through Saturday, you would specify the /PRIMEDAYS qualifier as follows:

/PRIMEDAYS=(NOMONDAY,TUESDAY,WEDNESDAY,THURSDAY,FRIDAY,SATURDAY,NOSUNDAY)

Occasionally an operational change occurs that conflicts with the normal day assignments at your site, such as a holiday falling on a primary day. To override the normal day assignment, use the DCL command SET DAY, and specify the day-type interpretation you want for the current day. This requires OPER privilege. Note that this change applies to all logged-in users, as well as those who will log in during the day. If users who are currently logged in are unauthorized for the day-type once it changes, they are logged out of the system at the next hour. (The job controller enforces time restrictions on an hourly basis.)

Decide which types of login access should be restricted to certain hours. The login access qualifiers are: /LOCAL, /REMOTE, /DIALUP, /INTERACTIVE, /BATCH, and /NETWORK. However, if your site applies one set of primary and secondary hours for all types of logins, you can specify the /ACCESS qualifier, which applies to all modes of access.

The following example shows how to apply the /BATCH qualifier to a user's account to disable the user from running batch jobs during normal working hours:

/NOBATCH=(PRIMARY, 9-17)

This specification permits the user to run batch jobs only during the hours of 6:00 p.m. through 8:59 a.m. on primary days but all day on secondary days.

7.1.2 Restricting Modes of Operation

The following concerns might cause you to prohibit network access for some of your users:

• The user has data that should be accessed only through the local node.
• Penetration attempts are more likely to occur over a network because of the increased anonymity of the connection. (This concern is also relevant to dialup connections.)

Use the AUTHORIZE qualifier /NONETWORK to prevent specific users from having network access, as shown in the following example:

UAF> ADD JSMITH /NONETWORK, ...

Any of the AUTHORIZE access mode qualifiers (/LOCAL, /REMOTE, /DIALUP, /INTERACTIVE, /BATCH, or /NETWORK) can be negated in this manner to restrict access to the system.

7.1.3 Restricting Account Duration

It is good practice to set an account expiration time that matches the maximum length of time you expect the user to require access. When the expiration time arrives, the system automatically prohibits access to the account. You must still remove the UAF record and delete the user's files.

Use of the /EXPIRATION qualifier also forces you to periodically review accounts and reauthorize only those that are necessary.

To set the account expiration time, use the AUTHORIZE qualifier /EXPIRATION in the user's UAF record. For example, the following qualifier specifies that the user's account will expire on the 30th of December 1995:

/EXPIRATION=30-DEC-1995

7.1.4 Disabling Accounts

You may want to severely restrict the use of certain accounts. For example, you may want to disable specific accounts used only periodically, such as the SYSTEST and FIELD accounts, to limit possible misuse of these accounts. Disable the accounts with the /FLAGS=DISUSER qualifier. Temporarily enable the accounts with the /FLAGS=NODISUSER qualifier when needed.

7.1.5 Restricting Disk Volumes

Identify the user's default device and directory in the UAF record with the AUTHORIZE qualifiers /DEVICE and /DIRECTORY. You can limit the number of blocks available to the user on that disk (and any other disk) through the disk quota feature of the System Management utility (SYSMAN), as described in the OpenVMS System Management Utilities Reference Manual: A--L.

The volume protection in place on other disks controls how much access a user can obtain to the disks. The user's privileges, which can be extended or limited through the AUTHORIZE qualifier /PRIVILEGES, also influence the access available (see Section 8.7).

7.1.6 Marking Accounts for External Authentication

Mark a user's account in the UAF record with the AUTHORIZE qualifier /FLAGS=EXTAUTH to allow the user to be externally authenticated.

See Section 7.4 for more information.

7.2 Assigning Appropriate Accounts to Users

The type of system access a user holds largely depends on his or her need for system resources and your site's security requirements. This section describes the types of user accounts that are available on OpenVMS systems and explains why one type of account may be preferable to another. For a step-by-step description of adding user accounts, refer to the OpenVMS System Manager's Manual.

7.2.1 Types of System Accounts

There are two major types of accounts:

• Interactive accounts have access to system software. Usually, such an account is considered an individual account.
• Limited-access accounts provide controlled login to the system and, in some cases, controlled access to user software. Limited-access accounts ensure that the system and process login command procedures, as well as any command procedures they call, are executed. There are two types of limited accounts: captive and restricted. Guest, proxy, and automatic login accounts are forms of captive and restricted accounts. DECwindows software does not currently support captive or restricted logins in the traditional sense. Once a user is logged in and creates a DECterm window, however, the traditional environment of a captive or restricted account applies.

Both interactive and limited-access accounts can be privileged accounts, and can be externally authenticated, as Section 7.2.2 describes.

The following table shows the kind of account to create based on the task a user performs:

If User Needs to...	Type of Account to Create
Perform work of a general nature, such as program development or text editing	Interactive
Perform routine computer tasks requiring limited activities	Captive
Run batch operations during unsupervised periods	Captive
Run applications programs with confidential information	Captive
Use network applications like MAIL	Restricted
Access resources on your system from a remote system (in a limited manner)	Captive or restricted
Use network proxy accounts	Restricted
Use authentication systems like smart cards	Restricted
Use accounts created as part of a layered product installation (such as the NOTES$SERVER account created during the installation of DEC Notes)	Restricted
Perform privileged operations	Interactive, restricted, or captive
Access resources from a remote system without a password	Captive
Automatically log in to an application terminal	Captive or restricted
Log in at the OpenVMS login prompt using their external user IDs and passwords	Externally authenticated

You may develop one or more templates that work for many of your users. However, do not oversimplify the process of account creation to the point that you simply apply a template. The danger in relying solely on templates is that you might overlook special considerations that apply to individual users, thereby forfeiting important controls that only you can exercise.

Examine templates regularly to be sure they are valid and reflect the way you want your operations to proceed. Templates become obsolete rapidly.

7.2.1.1 Interactive Account Example

Example 7-1 shows creating an interactive user account with moderate restrictions, typical of an account at a commercial site where security is a concern and the average user has limited access. Notice the following:

1. Only one password is required.
2. The password has a minimum length of 6 characters.
3. The user's password is valid for 90 days, a much longer lifetime than the manager's password shown in Example 6-1.
4. The user is allowed access during the week and on Saturdays.
5. During those six days, the user has access during a 15-hour period.

Example 7-1 Creating a Typical Interactive User Account

$ SET DEFAULT SYS$SYSTEM $ RUN AUTHORIZE UAF> ADD RDOGWOOD /PASSWORD=TRALAYAM/UIC=[231,010] - (1) _UAF> /DEVICE=BOTANYDEV/DIRECTORY=[RDOGWOOD] - _UAF> /OWNER="Robert Dogwood"/ACCOUNT=BOTNYDPT - _UAF> /FLAGS=(GENPWD)/PWDMINIMUM=6 - (2) _UAF> /EXPIRATION=15-JUNE-1994/PWDLIFETIME=90- (3) _UAF> /PRIMEDAYS=(MON,TUES,WED,THURS,FRI,SAT,NOSUN) - (4) _UAF> /NOACCESS=(PRIMARY,23-6,SECONDARY)/NODIALUP (5) identifier for value:[000231,000010] added to RIGHTSLIST.DAT UAF>

7.2.1.2 Limited-Account Example

Example 7-2 shows creating an applications production account where the user is highly restricted. This account is designed to perform two functions: list the grades at State University, and produce mailings to each student's home.

In the example, any value not specified defaults to the value provided by the default record in SYSUAF.DAT.

Notice the following:

1. Account users do not see the normal system welcome message. The account may not receive mail. It is restricted to running under control of its login command procedure and the default command interpreter (DCL).
2. The user who initiates the login must specify the password, GROBWACH. (Most likely only the security administrator will change the password.)
3. When the job is run through a local login, it is restricted to the hours of 8 a.m. through 5:59 p.m., Monday through Friday. (Notice that only batch and local logins are allowed, and batch mode does not have time restrictions.)
4. The job may not be run over dialup lines or as a remote job. The account also denies network access.
5. The process runs under the control of a special login command procedure (GRADES.COM), which presumably provides the operator with a menu of functions.
6. The process is restricted to the commands defined in the CLI table GRADES_TABLES.

Example 7-2 Creating a Limited-Access Account

$ SET DEFAULT SYS$SYSTEM $ RUN AUTHORIZE UAF> ADD REPGRADES /DEVICE=ADMINDEV/DIRECTORY=[REPGRADES] - _UAF> /FLAGS=(CAPTIVE,DISWELCOME,DISNEWMAIL,DISMAIL,DEFCLI) - (1) _UAF> /PASSWORD=GROBWACH/UIC=[777,031] - (2) _UAF> /OWNER="Campus Admin"/ACCOUNT=ADMIN - _UAF> /LOCAL=(PRIMARY,8-17)/PRIMEDAYS=(MON,TUES,WED,THU, - (3) _UAF> FRI,NOSAT,NOSUN) - _UAF> /NONETWORK/NOREMOTE/NODIALUP - (4) _UAF> /LGICMD=GRADES (5) /CLITABLES=GRADES_TABLES - (6) . . . user record successfully added identifier for value:[000777,000031] added to RIGHTSLIST.DAT

7.2.2 Privileged Accounts

Privileges determine what functions users are authorized to perform on the system. Any account with privileges beyond TMPMBX and NETMBX is considered privileged. Such an account can be interactive, restricted, or captive.

Because abuse of privileged accounts can result in serious losses, consider imposing special controls on accounts with the most powerful privileges as follows:

• Limit access to the account. For example, you can prohibit dialup or network access with the /NODIALUP or /NONETWORK qualifier to discourage outsiders from attempting break-ins from remote locations.
• Impose security alarms to detect use of the privileges pertaining to file protection: BYPASS, SYSPRV, READALL, and GRPPRV. For information about setting up and monitoring security alarms, see Chapter 9.

For all but the SYSTEM account, also add the following restrictions:

• Use the /PRIMEDAYS and /NOACCESS qualifiers to restrict the time of day or days of the week that logins can be performed. Select periods of time that can be monitored for appropriate use.
• Disable the account when not in use with the AUTHORIZE qualifier /FLAGS=DISUSER.
• Use a captive login command procedure for additional validation. Captive login command procedures are described in Section 7.2.4.

Naturally, you need to set controls on the SYSTEM account. The most secure practice is to disable it for all but batch access and perform system management through individual privileged user accounts, which provide accountability.

Special-Purpose Privileged Captive Accounts

Because the safety of a captive account depends on the integrity of its command procedures, it is unadvisable to set up privileged captive accounts for untrusted users. However, there are some situations that require privilege, and it is safer to perform specific sensitive functions through captive privileged accounts than through general purpose privileged accounts. For example, users who perform backup operations require the READALL privilege. By making the account that performs backups captive, you can ensure that the procedures are carried out according to your system's backup policy.

See Section 7.2.4 for guidelines for setting up captive accounts.

7.2.3 Interactive Accounts

Interactive accounts are very common in environments with low to moderate security requirements. They are well suited to work of a general nature, such as program development or text editing. The OpenVMS System Manager's Manual explains the procedure for setting up this type of account. Section 7.2.1.1 provides an example.

7.2.4 Captive Accounts

A captive account limits the activities of the user and, when properly administered, denies the user access to the DCL command level. You can set up the account to limit the user to running under the complete control of a specific program or the captive login command procedure.

The primary feature of the captive account is its login command procedure. This type of account ensures that the system login command procedure (SYLOGIN.COM) and the process login command procedure (specified by the /LGICMD qualifier in SYSUAF.DAT), as well as any command procedures they call, are executed. A user cannot specify any of the qualifiers shown in Table 7-2 to modify the captive command procedures when logging in.

Once logged in to a captive account, a user cannot escape to the DCL command level through the Ctrl/Y sequence, the SPAWN command, or the INQUIRE command. Because the DISCTLY flag in the UAF record is turned on, any use of Ctrl/Y fails. If unhandled errors or attempted interrupts occur, a system error message is generated, and the session is logged out. Unless the SPAWN command carries the /TRUSTED qualifier, it is ineffective within a captive account. SPAWN is also disabled from MAIL and the DEC Text Processing Utility (DECTPU) (as a built-in procedure). The INQUIRE command is also disabled to prevent the possible execution of user-specified lexical functions.

Table 7-2 Login Qualifiers Not Allowed by Captive Accounts

Qualifier	Description
/CLI	Specifies the name of an alternate command language interpreter
/COMMAND	Overrides the default login command procedure
/NOCOMMAND	Disables execution of the default login command procedure
/DISK	Requests an alternate default disk
/TABLES	Specifies the name of an alternate CLI table

7.2.4.1 Setting Up Captive Accounts

You define a captive account with AUTHORIZE by including the following qualifier when creating the account:

/FLAGS=(CAPTIVE)

A captive account also requires the qualifiers described in Table 7-3.

Table 7-3 Qualifiers Required to Define Captive Accounts

Qualifier	Action
/LGICMD	Identifies the captive account login command procedure and overrides the default login command procedure (LOGIN.COM in the user's default directory).
/UIC	Assigns a unique UIC group. Use the following form of the AUTHORIZE command SHOW to verify the uniqueness of the UIC group: SHOW [groupuic,*] By keeping the account in a separate group, you can ensure that the captive account users can access only world-accessible files and files owned by the captive account. It ensures that the account is not a member of the system group (that is, has a group value less than or equal to 10 8, unless modified by the system parameter MAXSYSGROUP).
/NOPASSWORD or /FLAGS=LOCKPWD	Sets up the password. With a captive account, either require no password, or lock the password so that only the security administrator can change it. Locked passwords are generally preferable to open captive accounts (those with no password). If you assign a locked password, give that password to all users of the captive account.
/PRCLM	Sets the subprocess limit to 0, thus preventing the user from spawning out of the account. (Verify that the system parameter PQL_MPRCLM---the minimum subprocess limit---is set to 0.)

In addition to the required settings, you may want to specify additional characteristics for the account:

• You may want to disable the welcome announcement and electronic mail for the captive account. This is done by setting the DISWELCOME, DISMAIL, and DISNEWMAIL login flags.
• You may want to allow only interactive use of the account from a local terminal. Include the qualifiers /NODIALUP, /NOREMOTE, /NOBATCH, and /NONETWORK when establishing the account.
• Your application may have special requirements. You may need to impose additional AUTHORIZE qualifiers on the account, such as /NODIALUP, to restrict modes of operation. Consider imposing restrictions for the periods of the day and days of the week when the process can run.
• You can define a special set of DCL tables by using the /CLITABLES qualifier, or you can emulate DCL through the use of a DCL command procedure. It is more efficient to define DCL tables than to resort to a DCL command procedure to emulate DCL. See the description of the Command Definition utility (CDU) in the OpenVMS System Management Utilities Reference Manual: A--L for help when defining the DCL tables. Be aware that the DCL tables defined by the /CLITABLES qualifier are not used in network jobs, such as those using the TASK object.
• You can grant privileges, although you rarely need to grant any privilege other than TMPMBX to a captive account.
• You can limit the disk quota for the captive account to the amount needed.

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