Operating System Security Hardening Guide for SAP HANA for SUSE Linux Enterprise Server 15 SP2 and later #

IT security is an essential topic for any organization. Newspapers report frequently about new IT security incidents such as hacked websites, successful Denial-of-Service attacks, or stolen user data like passwords, bank account numbers and other sensitive data.

In addition to the publicly reported attacks, there are also a large number of incidents that are not reported to the public. In particular, these cases are often related to espionage, where the affected party has no interest to report an incident. Security experts agree that, for protecting sensitive data, an organization must have a comprehensive security concept in place, taking all eventualities into account that can potentially lead into security risks. This starts with proper setup policies, like password and data protection policies for users and system administrators. It continues with a protected IT environment using for example firewalls, VPNs, and SSL in communication protocols. And it ends with hardened servers, intrusion detection systems, data encrypting and automated security reporting. Additionally, many organizations perform security audits on a regular basis to ensure a maximum of security in their IT environment.

Figure 1: Elements of a corporate IT security #

 

Comprehensive security concepts usually pay high attention to database systems, since databases belong to the most critical components in any IT environment. Database systems that potentially store sensitive data are by nature very popular targets for hackers and must therefore be protected. SAP HANA systems typically store business related information and are considered as being business critical. This is especially the case for ERP systems using SAP HANA. In addition, many other SAP applications using SAP HANA, like BW systems, may store sensitive data.

1.2 Security for SUSE Linux Enterprise Server #

 

The security of the underlying operating system is at least as important as the security of the SAP HANA database. Many hacker attacks target the operating system to gain access and sufficient privileges to attack the running database application. SUSE Linux Enterprise Server is the recommended and supported operating system for SAP HANA. SUSE has a long-running history in IT security for Linux operating systems. The company offers a comprehensive security package for SUSE Linux Enterprise Server to protect systems from all kind of security incidents. This package consists of the following components:

Security certifications

Both SUSE Linux Enterprise Server 12 and SUSE Linux Enterprise Server 15 have been awarded many important security certifications, such as the FIPS (Federal Information Processing Standard) 140-2 validation, or the Common Criteria EAL4+ certificate. For details visit https://www.suse.com/support/security/certifications/.

Security updates and patches

SUSE constantly provides security updates and patches for their SUSE Linux Enterprise operating systems and guarantees highest security standards during the entire product life cycle.

Documentation

SUSE has published a Hardening Guide and a Security Guide that describe the security concepts and features of SUSE Linux Enterprise Server 15. These guides provide generic security and hardening information valid for all workloads, not just for SAP HANA. For more details visit:

• https://documentation.suse.com/sles/15-SP2/html/SLES-all/book-hardening.html

• https://documentation.suse.com/sles/15-SP2/html/SLES-all/book-security.html

Figure 2: Security components of SUSE Linux Enterprise Server #

 

1.3 About this document #

 

To further improve the security level specifically for SAP HANA, SUSE provides the document at hand. It focuses on the security hardening of SUSE Linux Enterprise Server 15 running SAP HANA databases to fill the gap between the Security Guide for SUSE Linux Enterprise Server, the Hardening Guide for SUSE Linux Enterprise Server, and the SAP HANA Security Guide. The Hardening Guide for SUSE Linux Enterprise Server contains some of the recommendations found here, but also additional recommendations. Most of the recommendations can be applied to an SAP HANA installation after careful review and testing. SUSE collaborated with a large pilot customer to identify all relevant security settings and to avoid problems in real world scenarios. Also, SUSE and SAP are constantly cooperating in the SAP Linux Lab to provide the best compatibility with SAP HANA.

Figure 3: The five main topics of the OS Security Hardening for HANA #

 

The guide at hand provides detailed descriptions on the following topics:

Security hardening settings for SAP HANA systems

The Linux operating system provides many tweaks and settings to further improve the operating system security and the security for the hosted applications. To be able to fit for certain application workloads, the default settings are not tuned for maximum security. This guide describes how to tune the operating system for maximum security when running SAP HANA specifically. In addition, it describes possible impacts, for example on system administration, and gives a prioritization of each setting.

Local firewall for SAP HANA

SUSE has developed a dedicated local firewall for SAP HANA systems to improve the network security of SAP HANA. This is done by only selectively opening network ports on external network interfaces that are really needed either by SAP HANA or other services. All remaining network ports are closed. The firewall has a broad range of features and is easy to configure. It is available as RPM package and can be downloaded from SUSE.

Remote Disk Encryption

Starting with SUSE Linux Enterprise Server for SAP Applications 12 SP2, SUSE introduced a new feature called Remote Disk Encryption. Classical Disk Encryption - available for years – always required a passphrase being entered during boot. That prevented its use in many setups because each boot needed a manual step. Remote Disk Encryption removes this manual step as it allows the encryption keys to be stored safely on a remote key server and to be automatically used during system boot.

Minimal package selection

The fewer operating system packages an SAP HANA system has installed, the less possible security holes it should have. Following that principle, this guide describes which packages are absolutely necessary and which packages can be safely discarded. As a positive side effect, a minimized number of packages also reduces the number of updates and patches that have to be applied to a system.

Security updates & patches

Open source software is frequently reviewed and tested for security vulnerabilities by open source developers, security engineers from the open source community, security companies and, of course, by the hackers. When a vulnerability has been found and reported, it is published in security advisories and usually gets fixed very quickly. SUSE constantly provides security updates and patches for all supported packages on SUSE Linux Enterprise Server. This chapter explains which update and patch strategies are the best. It also details how to configure SUSE Linux Enterprise Server to frequently receive all relevant security updates.

In short, this guide covers all important topics in detail that are relevant for the operating system hardening of an SAP HANA system. Combining them with the other security features of SUSE Linux Enterprise Server 15, like the security certifications and the constantly provided security updates and patches, SAP HANA can run in a highly secure environment. This ensures that the implementation meets the security standards and corporate security concepts required by organizations of all sizes.

Figure 4: SAP HANA and Operating System Security #

 

All data processed by SAP HANA can contain sensitive information that need to be protected. Depending on the version the data volume, redoing log files or database backups can be encrypted by the SAP HANA itself. For details consult the SAP HANA Security Guide at https://help.sap.com.

If the internal encryption of SAP HANA should not or cannot be used, you can encrypt directories containing sensitive data via Remote Disk Encrypting available in SUSE Linux Enterprise Server for SAP Applications. When using the internal encryption, the various encryption keys are stored on disk in the SSFS which is located by default in <home-of-sidadm>/.hdb/<host-identity>/SSFS_HDB.DAT. The SSFS itself is encrypted with the SSFS master key, normally located in $DIR_GLOBAL/hdb/security/ssfs/, which is protected only by file permissions. To protect this key or the SSFS Remote Disk Encrypting can help to reach higher security. It will not store any key of SAP HANA directly, but can encrypt the part of the file system where the keys are located.

SUSE Remote Disk Encryption uses block devices as an encrypted container for arbitrary directories. It allows to store the encryption keys safely on a remote key server. To mount the device, the host contacts the key server on a TLS secured connection to retrieve the necessary keys automatically to unlock the data. Clearly the key server should be a dedicated, security-hardened, and protected system, since anyone with access to this system can retrieve the keys and decrypt the data.

The setup of client and server is described in more detail in the SUSE Linux Enterprise Server for SAP Applications guide, section 10 Encrypting Directories Using cryptctl at https://www.suse.com/documentation/sles-for-sap-15/.

Even though this guide already covers most security hardening topics, we are planning to provide further improvements. Also, later versions of SAP HANA might have changed, or new requirements regarding the hardening settings, the firewall or the minimal package selection might apply in future. It is planned to incorporate these new requirements as soon as they occur.

We recommend to check for updated versions of this document from time to time at the SUSE documentation pages at https://documentation.suse.com.

This document has been developed by Markus Guertler (Architect & Technical Manager, SAP Linux Lab), Soeren Schmidt (Solutions Architect, SAP Linux Lab) and Alexander Bergmann (Software Security Engineer, SUSE Maintenance & Security team).

The following table provides an overview of sources for further information regarding the discussed topics in this guide.

If you have any questions, comments or feedback on this document, do not hesitate to contact us under the email address saphana@suse.de.

This chapter lists content changes for this document since its first release.

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