HP OpenVMS Guide to System Security > Chapter 12 Security in a Network Environment

Using DECnet Application (Object) Accounts

  Table of Contents

  Glossary

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Network objects are system programs and user-written applications that permit communication among nodes in a DECnet network. You need to identify the set of network objects allowed access to your system, and set up the appropriate access controls for each object. The following mechanisms are available:

  • DECnet object accounts

    These are individual accounts for specific network objects (for example, MAIL) automatically configured on your system. These provide more accountability of remote access to an object than the default DECnet account provides. (For example, an object can have a captive account with a login command procedure that grants or denies access to the object based on the remote node name or user name.)

  • Default DECnet account

    This type of account allows all network objects general access to the system. It is appropriate for systems with low security requirements (for example, a local area network of systems located within a site with no outside connections or dialup lines).

    The default DECnet user name lets users perform certain network operations, such as the exchange of electronic mail between users on different nodes, without having to supply a user name and password. The default DECnet user name is also used for file operations when access control information is not supplied. For example, it lets remote users access local files on which the file protection has been set to allow world access. If you do not want remote users accessing your node, do not create a default DECnet user name. See “Removing Default DECnet Access to the System” for information about removing default DECnet accounts.

Summary of Network Objects

You should understand the function of the network objects supplied with the OpenVMS operating system before you determine the access control to apply to them. This section provides a description of the most common network objects.

FAL

The file access listener (FAL) is the remote file access facility. FAL is an image that receives and processes remote file access requests for files at the local node.

Use of general FAL access is strongly discouraged. Open access allows general network access to any files marked world-accessible. It also allows remote users to create files in any directory with world write access.

Sites with high security requirements, or sites where it is difficult to recognize all the intended users, should not create a FAL account. To control which users gain access, these sites may establish one or more proxy accounts for specific purposes (see “Proxy Access Control”).

MAIL

MAIL is an image that provides personal mail services for OpenVMS systems. In most cases, allow the MAIL object general access to the system.

MIRROR

MIRROR is an image used for particular forms of loopback testing. For example, MIRROR is run during the DECnet phase of the UETP test package.

MOM

MOM is the Maintenance Operations Module. The MOM image downline loads unattended systems, transferring a copy of an operating system file image from an OpenVMS node to a target node. The MOM object is established during a system installation.

NML

NML is the network management listener. Remote users with access to NML can use NCP TELL commands to gather and report network information from your DECnet databases.

PHONE

PHONE is an image that allows online conversations with users on remote OpenVMS systems. Note that if you allow default DECnet access to PHONE, anyone in the network can get a list of users currently logged in to the local system and attempt a login using the list of user names.

TASK

Through the default DECnet account, the TASK object allows arbitrary command procedures (including those that might be used in intrusions) to be executed on your system.

Note that if you do not allow default DECnet access on your system or if you disable default DECnet access to the TASK object, you can allow remote user-written command procedures (tasks) to run on your system through the use of access control strings or proxy access.

VPM

VPM is the Virtual Performance Monitor Server. Access to VPM is required to use the cluster monitoring features of the Monitor utility (MONITOR).

Configuring Network Objects Manually

The command procedure NETCONFIG.COM configures the network objects on your system automatically, and the command procedure NETCONFIG_UPDATE.COM updates the network objects automatically.

If you choose not to use the command procedures, you can perform the following steps to allow network access to specific objects:

  1. Create a top-level directory for each network object, and specify a unique owner UIC and group UIC. For example, the following command sequence creates a top-level directory for the MAIL object on the system disk:

    $ SET DEFAULT SYS$SPECIFIC:[000000]
    $ CREATE/DIRECTORY [MAIL$SERVER]/OWNER_UIC=[376,374]

    Table 12-2 “Network Object Defaults” lists the directory names, user names, and UICs used by the NETCONFIG.COM and NETCONFIG_UPDATE.COM command procedures to create accounts for specific network accounts. For consistency, you should specify the same information when manually creating network object accounts.

    Note that the MOM object is created by the operating system during installation.

  2. Using AUTHORIZE, create an account for the object, and use a generated password. (Note that the user name and password that you specify must match the password defined for the object in the network database [described in step 3].)

    For example, the following command sequence sets up an account for the MAIL object:

    $ RUN SYS$SYSTEM:AUTHORIZE
    UAF> ADD MAIL$SERVER/OWNER=MAIL$SERVER DEFAULT -
    _UAF> /PASSWORD=MDU1294B/UIC=[376,374]/ACCOUNT=DECNET -
    _UAF> /DEVICE=SYS$SPECIFIC: /DIRECTORY=[MAIL$SERVER] -
    _UAF> /PRIVILEGE=(TMPMBX,NETMBX) /DEFPRIVILEGE=(TMPMBX,NETMBX) -
    _UAF> /FLAGS=(RESTRICTED,NODISUSER,NOCAPTIVE) /LGICMD=NL: -
    _UAF> /NOBATCH /NOINTERACTIVE

    The AUTHORIZE command SHOW MAIL$SERVER displays the network account set up for the MAIL object, as shown in Example 12-2 “UAF Record for MAIL$SERVER Account”.

  3. Use the NCP DEFINE command to associate the user name and password of the account with the specified object in the network database, as follows:

    $ RUN SYS$SYSTEM:NCP
    NCP> DEFINE OBJECT MAIL USER MAIL$SERVER PASSWORD MDU1294B
    NCP> EXIT
  4. Repeat steps 1 through 3 for each network object.

  5. When finished, remove default DECnet access from the executor database, and remove the default DECnet account from the SYSUAF (see “Removing Default DECnet Access to the System” ).

  6. Finally, reboot the system to copy changes made to the permanent executor and object databases to the running system.

Table 12-2 “Network Object Defaults” lists the network object defaults.

Table 12-2 Network Object Defaults

Object Name Directory and User (Account) Name UIC

FAL

FAL$SERVER

[376,373]

MAIL

MAIL$SERVER

[376,374]

MIRROR

MIRRO$SERVER[1]

[376,367]

$MOM

VMS$COMMON:[MOM$SYSTEM][2]

[376,375]

NML

NML$SERVER

[376,371]

PHONE

PHONE$SERVER

[376,372]

VPM

VPM$SERVER

[376,370]

[1] Because AUTHORIZE enforces a user name limit of 12 characters, you must truncate the user name (and directory name) of the MIRROR object account to MIRRO$SERVER.

[2] MOM has no associated user name.

 

Example 12-2 UAF Record for MAIL$SERVER Account

Username: MAIL$SERVER            Owner:  MAIL$SERVER
Account: MAIL$SERVER DEFAULT UIC: [376,374] ([DECNET,MAIL$SERVER])
CLI: DCL Tables:
Default: SYS$SPECIFIC:[MAIL$SERVER]
LGICMD:
Login Flags: Restricted
Primary days: Mon Tue Wed Thu Fri Sat Sun
Secondary days:
Primary 000000000011111111112222 Secondary 000000000011111111112222
Day Hours 012345678901234567890123 Day Hours 012345678901234567890123
Network: ##### Full access ###### ##### Full access ######
Batch: ----- No access ------ ----- No access ------
Local: ----- No access ------ ----- No access ------
Dialup: ----- No access ------ ----- No access ------
Remote: ----- No access ------ ----- No access ------
Expiration: (none) Pwdminimum: 6 Login Fails: 0
Pwdlifetime: (none) Pwdchange: (none)
Last Login: (none) (interactive), (none) (non-interactive)
Maxjobs: 0 Fillm: 16 Bytlm: 12480
Maxacctjobs: 0 Shrfillm: 0 Pbytlm: 0
Maxdetach: 0 BIOlm: 12 JTquota: 1024
Prclm: 0 DIOlm: 6 WSdef: 180
Prio: 4 ASTlm: 16 WSquo: 200
Queprio: 0 TQElm: 10 WSextent: 0
CPU: (none) Enqlm: 20 Pgflquo: 25600

Authorized Privileges:
TMPMBX NETMBX
Default Privileges:
TMPMBX NETMBX

Removing Default DECnet Access to the System

The default DECnet account is appropriate for systems with low security requirements (see “Using DECnet Application (Object) Accounts”). If your site has moderate or high security requirements, you should remove default DECnet access to the system once you have set up accounts for individual network objects.

CAUTION: Before deleting your default DECNET account, as described in this section, use the NCP command SHOW KNOWN OBJECTS and the Authorize utility (AUTHORIZE) to verify that all network objects and layered products that use network objects have network accounts set up in the system user authorization file (SYSUAF.DAT). Otherwise, network objects and layered products that use network objects may not work as expected.

To do this, remove access to the DECNET account in the network configuration database, and delete the DECNET account from the SYSUAF.

Removing Default DECnet Access

Execute the following NCP commands to remove the default DECnet access from the network executor database:

NCP> DEFINE EXECUTOR NONPRIVILEGED USER DEFAULT_DECNET
NCP> PURGE EXECUTOR NONPRIVILEGED PASSWORD

The DEFAULT_DECNET user specified in the first command is a nonexistent user account that is specified for auditing purposes only. (A network login failure message is written to the security audit log file each time access to your system is attempted through the [nonexistent] DEFAULT_DECNET account.)

Deleting the DECNET Account

Using AUTHORIZE, remove the DECNET account from SYSUAF, as follows:

$ SET DEFAULT SYS$SYSTEM
$ RUN AUTHORIZE
UAF> REMOVE DECNET
UAF> EXIT

Delete any files in the [DECNET] directory structure.

Modifying the Volatile Configuration Database

To have the change take effect immediately, modify the volatile database with the following NCP commands:

NCP>SET EXECUTOR NONPRIVILEGED USER DEFAULT_DECNET
NCP>CLEAR EXECUTOR NONPRIVILEGED PASSWORD

Setting Privilege Requirements for Remote Object Connections

You can select specific privileges to control the use of DECnet objects that are specified during network configuration. In such instances, it becomes a privileged operation either to connect to a privileged DECnet object or use an outgoing DECnet object.

For example, the following command establishes the requirement that users initiating a DECnet connection to the remote object MAIL must possess the OPER and SYSNAM privileges:

NCP>DEFINE OBJECT MAIL OUTGOING CONNECT PRIVILEGES OPER,SYSNAM

This mechanism is a useful way of limiting access to certain DECnet applications to privileged users or programs. However, to be effective, the privilege requirement must be imposed consistently on all nodes in the network.