Security on z/OS

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Security has always been one of the strong propositions and differentiators of the mainframe and the z/OS operating system. In this post I will highlight a few of the differentiating factors of the mainframe hardware and the z/OS operating system.

The mainframe provides a number of distinguishing security features in its hardware. In z/OS a centralized security facility is a mandatory and built-in part of the operating system. Also, z/OS exploits the security features that the mainframe hardware provides. This chapter will highlight what the central security facility in z/OS is, and how z/OS exploit unique hardware features of the mainframes.

Centralized security management

The central security management built into z/OS provides a standardized interface for security operations. A few software vendors have implemented this interface in commercial products, thus providing a security management solution for z/OS.

The SAF interface

The main security component of z/OS is the centralized security function called System Authorization Facility or SAF. This component provides authentication and authorisation functions.

The z/OS operating system itself and the middleware installed on z/OS make use of this central facility. With the SAF functions, z/OS and middleware tools can validate access to the resources that the middleware products need to protect.

A protected resource can be a dataset, a message queue, a database table, but also a special function or command that is part of the middleware software. By building in API calls to the SAF interface, the middleware product controls access to sensitive functions and resources.

Security products

The SAF interface of z/OS operating system is just that: a standardized interface. The implementation of the interface is left to software vendors. The SAF interface does not prescribe how security definitions should be stored or administrated.

There are three commercial solutions in the market that have implemented the SAF interface: IBM with its security product RACF, and CA/Broadcom with two different tools: ACF2 and Top Secret. All three software products provide additional services related to security management such as administration, auditing and reporting services. All three products define a special role in the organisation that is appointed to have the restricted ability to define and change the security rules. The security administrator has these special authorizations. The security administrator defines which users and/or groups of users are allowed to access certain resources.

The SAF interface and security products

IBM Enterprise Key Management Foundation

The z/OS operating system in equipped with a tool that IBM calls the IBM Enterprise Key Management Foundation (EKMF). This is a tool that manages cryptographic keys. EKMF is a full-fledged solution for centralized management of cryptographic keys that can be used on the mainframe, but also on other platforms.

Many organizations have dedicated key management infrastructure for different platforms. The EKMF solution allows organization to instead build a key management solution that can be used for all platforms.

Cryptographic facilities on the mainframe

EKMF and other cryptographic features in z/OS make use of the extensive cryptographic functions built into the mainframe hardware. Traditional encryption facilities have since long been a core part of the mainframe hardware. Recently IBM has added innovative features such as pervasive encryption and Data Privacy Passports, now called Hyper Protect data Controller.

Traditional encryption

The mainframe hardware and software are equipped with the latest encryption facilities, that allow for encryption of data and communications in the traditional manner.

What differentiates the mainframe from other platforms is that it is equipped with special processors that accelerate encryption and decryption operations and can enable encryption of high volumes of data.

Pervasive encryption

Pervasive encryption is a new general feature facilitated in the mainframe hardware. With pervasive encryption data is always encrypted: data is encrypted when stored on disk, but also during the communication over the networks end internal connections between systems. This encrypted data can only be used by users that are authorized to the right decryption keys.

Pervasive encryption gives an additional level of security. Even when a hacker has gained access to the system and gained access to the files or datasets, she still cannot use the data because it is encrypted. Similarly, even if you could “snif” the communications between systems and over the network, this is not sufficient because also the data flowing over communications networks is always encrypted.

IBM Hyper Protect Data Controller

Another problem occurs when data that is replicated from the source in the mainframe to other environments, typically for analysis, or aggregation with other data sources. The data that was so well protected on the mainframe, but now has become available in potentially less controlled environments. For this issue IBM has developed the IBM Hyper Protect Data Controller solution.

With this IBM Hyper Protect Data Controller solution, when a copy of the data is needed, the copy is encrypted and in this copy a piece of information is included that administers who is authorized to access that copy. This access scheme can be as detailed as describing who can use which fields in the data, who can see the content of certain fields, and who can see only masked values. A new component on z/OS, the Trust Authority maintains a registry of all data access definitions.

When the data copy is accessed, the so-called passport controller checks the identity of the person requesting the data access, and authorizations of that person for this copy of the data.

Doing so, a copy of the data can be centrally protected, while still it can be made copied to different environments.

Multifactor Authentication

Traditional authentication on z/OS relies on a userID / password combination, that is validated against the central security registry, as we have seen in RACF, ACF2 or Top-Secret.

However, the userID / password authentication is nowadays not considered sufficiently safe anymore. To address this safety issue multifactor authentication in broadly adopted. For the z/OS platform, IBM has developed the product called Multifactor Authentication for z/OS. Instead of using the normal password to logon to z/OS, a user must supply a token that is generated by a special authorized device. This special device can be a SecurID token device, a smartphone with a special app, or otherwise. The key thing is that next to a userID and password, pin code or fingerprint, there is a second thing – the second factor – needed for the user to prove his identity: the special device or authorized app on your phone.

Multifactor authentication on z/OS