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Updated: 11 December 1998

OpenVMS Guide to System Security


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11.9 Using DECnet Between Cluster Nodes

The cluster environment provides such a rich resource-sharing model (which includes files and volumes, disk and tape devices, and batch and print queues) that it is usually unnecessary to directly access another cluster node through DECnet software. Nonetheless, there are situations where resources may not be uniformly shared across the cluster. This is particularly true in mixed interconnect or local area cluster configurations, where you may choose to limit cluster access to a satellite's disk or tape volumes. In such cases, users need to use the DCL command SET HOST or some form of network access to access a satellite's resources from other cluster members. See Section 12.3 for more information on network access through proxy logins.


Chapter 12
Security in a Network Environment

Security in a network environment is even more sensitive than security in a single-system environment. Security is also harder to achieve because of operational complexities and the decentralization of control that commonly exist in networks. The larger the network, the more difficult the problem of establishing control and communication between security administrators of the numerous nodes.

There are limitations in the degree of security any networking site can expect to achieve due to limitations currently present in networking technology. Being sensitive to potential problems can help you avoid operations that could increase the security exposure in your network. This chapter helps you recognize these problem areas and adjust your operations accordingly.

This chapter assumes you are familiar with the information in the DECnet for OpenVMS Networking Manual for DECnet Phase IV or DECnet/OSI Network Management for DECnet Phase V. For information on the Authorize utility, refer to the OpenVMS System Management Utilities Reference Manual.

12.1 Managing Network Security

DECnet for OpenVMS regulates access to the network on various levels:

12.1.1 Requirements for Achieving Security

There are three critical requirements for achieving security in a network environment:

Figure 12-1 The Reference Monitor in a Network


12.1.2 Auditing in the Network

Security administrators can audit network activity by enabling specific event classes with the SET AUDIT command. Possible audits include:

12.2 Hierarchy of Access Controls

Whenever a DECnet node attempts to connect to a remote DECnet node, it sends access control information to the remote node. Access control information can come from a number of sources. The following list shows the hierarchy of access control from highest to lowest priority:

  1. The network user on the local node can explicitly supply access control information. If this is the case, the remote node uses the access control information. See Section 12.2.1 for information about explicit access control.
  2. The local node checks to see if outgoing proxy access is enabled for a local node or an application. If proxy is enabled, the local node sends the initiating user name in the connect request. If proxy is also enabled on the remote node, the DECnet software determines if the initiating user has proxy access. See Section 12.2.2 and Section 12.3 for information about proxy access control.
  3. When the remote node sees that no access control has been specified and that no proxy is applicable, it checks the configuration database. If the database contains an application user name, it uses that name. See Section 12.2.3 and Section 12.4 for information about default application accounts.
  4. If there is no default application user name in its configuration database, the remote node checks the configuration database for default nonprivileged DECnet user name information. If the information is there, the remote node uses the default nonprivileged DECnet user name. See Section 12.4 for information about the default DECnet account.

Finally, if none of these sources supply the information, the connection fails.

12.2.1 Using Explicit Access Control

Users can execute a DCL or an NCP command on a remote node by supplying explicit access control information. The access control information contains a user name and password and provides access to a specific account on the remote system. To supply explicit access control information, you can use either a standard OpenVMS node specification or an NCP command:

12.2.2 Using Proxy Logins

A proxy login enables a user logged in at a remote node to be logged in automatically to a specific account at the local node, without having to supply any access control information. Note that a proxy login is not the same as an interactive login. A proxy login means that specific network access operations can be executed, such as a copy operation. By contrast, an interactive login requires a user to supply a user name and password before the user can perform any interactive operations.

To establish a proxy login on the local node, the remote user must have a default proxy account on the local node that maps to a local user name. The remote user assumes the same file access, rights, and privileges as the local user name. You can use the proxy login capability to increase security because it minimizes the need to specify explicit access control information in node specifications passed over the network or stored in command procedures.

Note that network applications can also be assigned proxy login access.

The use of access control strings in not permitted in an evaluated configuration. Proxy login accounts should be used in the evaluated configuration.

12.2.3 Using Default Application Accounts

Another form of access control specific to network applications is default account information used by inbound connects from remote nodes that send no access control information. Because the remote node supplies no access control information, the local node uses the default information you specify for the application to make the connection.

You can use the following command to store default access control information about the application in the network configuration database:


NCP> SET OBJECT FAL USER JILL

12.3 Proxy Access Control

Section 12.2.2 defines the concept of proxy logins. You can authorize proxy access when you encounter situations where users on different nodes or in different groups want to share files on your system and you are reluctant to give out passwords or to set the directory and file protection to W:RWE. With proxy logins, there is no need to embed passwords in commands to copy a file across the network. There is also no need to allow world read access to a file for file transfers. The user enters the following form of the DCL command COPY to a default proxy account:

COPY remotenode::file-spec file-spec 

To copy a file over the network using proxy access from an account other than the default, the user includes the name of the proxy account in the access control string of the DCL command, as follows:

COPY remotenode"proxyacct"::file-spec file-spec 

12.3.1 Special Security Measures with Proxy Access

Proxy access is a selective merging of the authorization databases of the affected systems. Therefore, the security is only as good as the security of the least secure node.

Although proxy access eliminates passwords going over the network, it is possible for a personal computer to bypass the proxy login mechanism by impersonating one of the authorized nodes. For this reason, implement the following procedures:

12.3.2 Setting Up a Proxy Database

If a remote user's connection request does not contain access control information, the following conditions must be met for proxy access to be approved:

You can control the use of proxy logins at the local node. Use AUTHORIZE to create and modify the permanent proxy database.

The default network proxy authorization file is NET$PROXY.DAT. However, AUTHORIZE maintains the file NETPROXY.DAT for compatibility, for support of many layered products, and for translation of DECnet for OpenVMS (Phase IV) node names.

Each network proxy entry can map a single remote user to multiple proxy user names on the local node (one default proxy user name and up to fifteen additional proxy user names). If you are going to have access to more than one proxy account from the same node and login name, indicate which proxy account should be the default. The proxy database entry identifies the user in the form of nodename::username or nodename::[group,member].

For example, to create a proxy file at a local node and add a default proxy entry mapping user Martin on remote node Boston to user Allen at the local node, enter the following commands:


$ SET DEFAULT SYS$SYSTEM
$ RUN AUTHORIZE
UAF> CREATE/PROXY
UAF> ADD/PROXY BOSTON::MARTIN ALLEN/DEFAULT
UAF> EXIT

Similarly, the system manager at a remote node can create and maintain a proxy database of network users having proxy access to specific accounts on that node. Table 12-1 summarizes AUTHORIZE commands used to manage the proxy database.

Table 12-1 AUTHORIZE Commands for Managing Network Proxy Access
Command Argument Description
ADD/PROXY node::remoteuser
localuser[,...]
Adds proxy access for the specified user.
CREATE/PROXY   Creates a network proxy authorization file.
LIST/PROXY   Creates a listing file of all proxy accounts and all remote users with proxy access to the accounts.
MODIFY/PROXY node::remoteuser Modifies proxy access for the specified user.
REMOVE/PROXY   Deletes proxy access for the specified user.
SHOW/PROXY *
node::remoteuser
Displays proxy access allowed for the specified user.

12.3.2.1 Enabling and Disabling Incoming Proxy Access

You can control proxy access to your node and to particular applications.

Controlling Proxy Access to a Node

To accept proxy connections to your node, set the incoming proxy attribute in the executor database in the following way:


NCP> SET EXECUTOR INCOMING PROXY ENABLE

To deny proxy connections to your node, set the outgoing proxy attribute in the following way:


NCP> SET EXECUTOR INCOMING PROXY DISABLE

If proxy access to the node is disabled, the system ignores any proxy connection request.

A comparable set of steps is necessary on the originating node so that proxy data is transmitted in the connect request message. Set proxy attributes for both the node and for all applications that expect to use proxy, for example:


NCP> SET EXECUTOR OUTGOING PROXY ENABLE
NCP> SET OBJECT MAIL PROXY BOTH
NCP> SET OBJECT MAIL PROXY INCOMING
NCP> SET OBJECT MAIL PROXY OUTGOING

In general, enabling outgoing proxy is a good idea, even if the target node does not enable proxy for the object, because enabling outgoing proxy puts the originating user name in the connect message. Thus the user name is available for accounting and audit logs on the target node. Be aware that a small number of DECnet applications depend on the nonproxy form of the connect message (for example, some use the connect message space for application information rather than user names) and do not function if outgoing proxy is enabled.

Controlling Proxy Access to an Application

To allow proxy access to a particular application, you must enable the proxy access for both the node and the application. In addition, specify the name of the application in the SET OBJECT command. For example, the following enables proxy access to the application NML:


NCP> SET EXECUTOR INCOMING PROXY ENABLE
NCP> SET OBJECT NML INCOMING PROXY ENABLE

To disable proxy access to an application, identify the application in the SET OBJECT command, and set the incoming proxy attribute to disable. For example, the following disables proxy access to the application FAL:


NCP> SET OBJECT FAL INCOMING PROXY DISABLE

If incoming proxy is enabled for the application but the proxy access for the node is disabled, the system in effect ignores any proxy access request to the application.

12.3.2.2 Removing Proxy Access

Remove proxy access to the system when it is no longer needed. Invoke AUTHORIZE, and enter the following command to remove proxy access:


UAF> REMOVE/PROXY BOSTON::MARTIN

12.3.2.3 Procedure for Creating a Proxy Account

When you want to set up a proxy account on your node for use by one or more users at other nodes, you must perform the following steps. Refer to the security guidelines listed in Section 12.3.1 as you create the account.

  1. Define the purpose of the account, its name, and which network users will be admitted.
  2. Create the local account, if necessary, with AUTHORIZE; if the account already exists, make sure it is restricted and defined as /NOINTERACTIVE, /NOBATCH, /NETWORK.
  3. Review the privileges on the account. Generally avoid granting privileges to proxy login accounts.
  4. Create the network proxy authorization file, if necessary, with the AUTHORIZE command CREATE/PROXY. (The system usually creates it automatically.)
  5. Allow as many remote users as necessary access to the proxy account with the AUTHORIZE command ADD/PROXY.
  6. Check the default protection on the directory, and customize it as necessary.
  7. Examine any login command procedure specified by the /LGICMD qualifier to the ADD command. In captive accounts, make certain that the login command procedure follows the recommendations in Section 7.2.4.2. It should reside in a well-protected directory owned by a user other than the owner of the proxy account. It should prohibit write access for those who use the account.
  8. Notify the security administrator at the remote node about which users from that node have been authorized for access to your node.


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