Operating System Security Hardening Guide for SAP HANA for SUSE Linux Enterprise Server 12 #

IT security is an essential topic for any organization. Newspapers report frequently about new IT security incidents like hacked websites, successful Denial-of-Service attacks, 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, 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 pieces 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 considered as being business critical. This is especially the case for ERP systems using SAP HANA. Also many other SAP applications using SAP HANA, like BW systems, may also 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 on 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 the SUSE Linux Enterprise Server to protect systems from all kind of security incidents. This package consists of the following components:

Security certifications

SUSE Linux Enterprise Server 12 has been awarded many important security certifications, such as the FIPS (Federal Information Processing Standard) 140-2 validation or the Common Criteria Security EAL4+ certificate. For details please 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 over the whole product life cycle.

Documentation

SUSE has published a security guide that describes the security concepts and features of SUSE Linux Enterprise Server 12. This security guide provides generic security information valid for all workloads, not just for SAP HANA. For more detailed information, see https://www.suse.com/documentation/sles-12/singlehtml/book_hardening/book_hardening.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 12 running SAP HANA databases to fill the gap between the generic SUSE Linux Enterprise Server Security Guide, the SUSE Linux Enterprise Server Hardening Guide and the SAP HANA security guide. The SUSE Linux Enterprise Server Security Guide and Hardening Guide contain some of the recommendations found here, but also additional recommendations. Most of the recommendations can be applied to a 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 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 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 anb 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 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 12, like the security certifications and the constantly provided security updates and patches, SAP HANA can run in a very 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 #

 

Introduction to Linux security hardening _{~~~~~~~~~~~~~~~}~ SUSE Linux Enterprise Server already provides a high level of security with the standard installation. However, the standard security settings are generic, because they have to fit to all possible Linux server workloads. Also, many security settings have impacts on the comfort of the system administration and possibly also for the users of the system. Therefore, the SUSE Linux Enterprise Server 12 standard security settings provide a good tradeoff between compatibility to all workloads, administrative comfort and a secure operatingsSystem.

SAP HANA is a very special workload with clearly defined requirements. For such a workload, it is possible to have a more restrictive security configuration compared to the standard configuration. The goal of this guide is to strengthen the security without affecting the compatibility with SAP HANA.

While security hardening results in more security, it usually comes with the drawback of less administrative comfort and system functionality. This is a fact that every System Administrator should be aware off. However, a more restrictive configured system also provides a better level of protection and a lower risk of successful attacks. In many cases company security policies, guidelines or security audits force very high security standards, which automatically result in more restrictive configured systems. The Linux Operating System has many tweaks and settings that can improve the overall security of the Operating System and its applications. These settings can be summarized in the following categories:

2.1 Hardening settings for SAP HANA systems #

 

Important

The measures in this chapter are described for the x86 architecture (x86 and AMD64/Intel 64), but apply for the POWER architecture as well. Because of the differences in the hardware, it might be necessary to adapt them (different device names, etc.)
Also, the graphical user interface is not covered. Running a GUI on a secure server should be avoided.

The following hardening settings improve the security of SUSE Linux Enterprise Server systems running SAP HANA database. These settings are based on the recommendations of a security audit, which was performed on a SUSE Linux Enterprise Server standard installation, running SAP HANA database.

Note

Read the SUSE Linux Enterprise Server Security Guide and the SUSE Linux Enterprise Server Hardening Guide for additional measures (see https://documentation.suse.com/).
(Choose "SUSE Linux Enterprise Server" instead of "SUSE Linux Enterprise Server for SAP Applications".

For each setting the following details are provided:

• Description: Details of the setting

• Procedure: How to apply the setting

• Impacts: Possible impacts for system administrators or users

• Priority: High, Medium, Low

Based on the impact of a particular setting, a system administrator or a security engineer can decide if the lost of administrative comfort is worth the gain in security.

The prioritization can be used to help decide which settings should be applied to meet security requirements. High priority settings should be applied when possible, whereas low priority settings can be treated as optional.

IMPORTANT: Disclaimer: We strongly recommend to execute all described hardening settings on a non-productive (such as a DEV or QA) system first. We also recommend to backup the system before doing any changes. If btrfs/snapper is being used, creating a snapshot of the root file system is advised. Furthermore, we recommend to test the functionality of SAP HANA and all related applications and services after applying the settings. Since SAP HANA installations, use cases, hardware and installed services are likely to be different from the test audit. it cannot be guaranteed that all settings work correctly. It even cannot be completely excluded that they potentially have a negative impact on the functionality of the system.

If it is not possible to test the settings on a non-productive system, the changes should only be made within a maintenance window. The maintenance window should provide enough time for a proper system functionality test, or for restoring the system if necessary.

2.1.1 Installing SUSE security checker #

 

Description

The SUSE security checker (seccheck) performs certain security checks, executed via cron jobs, on a regular basis, and generates reports. These records are usually forwarded via email to root. More details about seccheck can be found in /usr/share/doc/packages/seccheck/README or at https://www.suse.com/documentation/sles-12/singlehtml/book_hardening/book_hardening.html#sec.sec_prot.general.seccheck.

Important

The password check is not done because the password-cracking software tool john is not available on SUSE Linux Enterprise Server. The check would fail silently.

Procedure

Install package seccheck:

zypper in seccheck

Impact

• Daily and weekly reports via email to the root user.

• Requires a properly setup email forwarding.

Priority

Medium

2.1.2 Configuring mail forwarding for root user #

 

Description

To receive information about the security relevant changes and incidents, it is strongly recommended to enable mail forwarding for the user root to a dedicated email account for the collection of system mails.

Procedure

1. Install 'Yast2-mail':

   zypper in yast2-mail

2. Start the 'YaST' mail module:

   yast mail

3. Choose 'Permanent' as connection type

4. Enter address of internal mail gateway and configure authentication if required

5. Do NOT enable 'accept external SMTP connections'

6. Enter email address to forward root emails (typically a dedicated system mail collection account)

7. Save settings

8. Test settings with

   mail root
   
   subject: test
   test
   .

9. Verify with the command mailq if the email has been delivered.

Impact

• Requires an accessible SMTP server.

• Requires somebody that regularly checks the mails of the 'root' user.

Priority

High

2.1.3 Configuring hosts.allow and hosts.deny according to local network setup #

 

Description

The files hosts.allow and hosts.deny allow or respectively deny access for certain services and applications. We recommend not to set access control in these files and to use the local SAP HANA firewall instead. The SAP HANA firewall, based on iptables, allows a much more fine-grained access control, higher security and better logging mechanisms.

Only few applications still support these files. To verify if a binary does so, check if 'libwrap' is used:

 ldd <path_to_binary> | grep libwrap

2.1.4 Forwarding syslog files to a central syslog server #

 

Description

Log files should be forwarded from an SAP HANA node to a central syslog server. This prevents syslog files from being manipulated by an attacker. In addition, it allows administrators to have a central view on the syslog files.

Procedure

This procedure explains a basic syslog forwarding setup. For a more sophisticated setup, consult the RSyslog manual at https://www.rsyslog.com/doc/master/index.html#manual.

On the target syslog server (running SUSE Linux Enterprise Server 12)

1. Edit /etc/rsyslog.d/remote.conf

2. Uncomment the following lines in the 'UDP Syslog server' or 'TCP Syslog Server' block of the configuration file and enter the IP address and port of the interface 'rsyslogd' shall listen:

   TCP example

   $ModLoad imtcp.so
   $UDPServerAddress <ip>
   $InputTCPServerRun <port>

   UDP example

   $ModLoad imudp.so
   $UDPServerAddress <ip>
   $UDPServerRun <port>

3. Restart rsyslog:

   systemctl restart rsyslog.service

On the SAP HANA node

1. Edit /etc/rsyslog.d/remote.conf

2. Uncomment the appropriate line (TCP or UDP) and replace 'remote-host' with the address of the central log server:

   TCP example

   # Remote Logging using TCP for reliable delivery
   # remote host is: name/ip:port, e.g. 192.168.0.1:514, port optional
   *.* @@remote-host

   UDP example

   # Remote Logging using UDP
   # remote host is: name/ip:port, e.g. 192.168.0.1:514, port optional
   *.* @remote-host

3. Restart rsyslog:

   systemctl restart rsyslog.service

4. Verify the proper function of the syslog forwarding using the command:

   logger "hello world"

   The log message “hello world” should now appear on the central syslog server.

Impact

• Requires a central syslog server.

Priority

Medium

2.1.5 Disabling ctrl-alt-del #

 

Description

Prevent reboot of a system via serial console and/or external keyboard

Procedure

Create the following symlink:

ln -s /dev/null /etc/systemd/system/ctrl-alt-del.target

Impact

• A system reboot can not be performed via a local keyboard or a remote-management session anymore.

• This can be irritating for system administrators, but it also helps to prevent accidental reboots.

Priority

Medium

2.1.6 Implementing cron.allow #

 

Description: The cron.allow file specifies a whitelist of users that are allowed to execute jobs via the cron system. The file does not exist by default. This means every user (except those listed in cron.deny ) can create cron jobs.

Procedure

Create an empty file /etc/cron.allow to prevent a user from creating cron jobs:

touch /etc/cron.allow

Info

Location of user crontabs: /var/spool/cron/tabs

Impact

• SAP HANA users ('<sid>adm') and other users are not allowed anymore to create their own cronjobs.

Priority

Low

2.1.7 Implementing at.allow #

 

Description

The at.allow file specifies a whitelist of users that are allowed to execute scheduled one-time running jobs, so-called 'at' jobs, via the 'at' job execution system. This file does not exist by default. This means that every user (except those listed in at.deny) can create 'at' jobs.

Procedure

Create an empty file /etc/at.allow to prevent a user from creating 'at' jobs:

touch /etc/at.allow

Impact

• The functionality of one-time 'at' jobs gets disabled.

Priority

Medium

Restricting sudo for general users ^{^^^^^^^^^^^} Description:: The sudo command allows users to execute commands in the context of another user, typically the root user. The sudo configuration consists of a ruleset that defines the mappings between commands to execute, their allowed source and target users and groups. The configuration is stored in the file /etc/sudoers. Like the command su, sudo asks for the root password by default. However, unlike su, sudo remembers the password and allows further commands to be executed as root without asking again for the password for five minutes. Therefore, sudo should only be enabled for selected users, such as admin users.

Procedure

1. Edit file /etc/sudoers, for example by executing visudo

2. Comment out the line to:

   #ALL ALL=(ALL) ALL # WARNING! Only use this together with 'Defaults targetpw'!

3. Uncomment this line to:

   %wheel ALL=(ALL) ALL

4. Add all system administrator users to the group wheel:

   usermod -aG wheel <admin_user>

   

   Important

   The user added to the wheel group has to log out and log in again to get the new group membership applied.

Tip

If sudo asks for the password of the target user instead of the user invoking sudo, uncomment (default) the line Defaults targetpw # ask for the password of the target user i.e. root. For more details, read the man page of sudoers.

Impact

• Prohibits sudo command functionality for all users, other than the ones that are members of the group 'wheel'.

• Note that the su command is still available for other users.

Priority

High

Adjusting default umask ^{^^^^^^^}^^ Description:: The command umask specifies the default XOR-masking for access rights for newly created files. We recommend to change this value to 077. This will force newly created files and directories to be not read/write/execute enabled for groups and other users.

Procedure

Edit file /etc/login.defs and change the umask value:

UMASK 077

Tip

The PAM module pam_umask.so (in /etc/pam.d/common-session) applies the UMASK setting made in /etc/login.defs. Refer to the respective man page for alternatives.

Impact

• Newly created files and directories are not read-, write- and executable by users other than the creating user.

Remarks

To take changes into effect, a logout / re-login of all user sessions is required.

Priority

High

2.1.8 Modifying login definitions according to corporate security policies #

 

Description

The file /etc/login.defs describes the login settings for users, such as password expiration times password aging), number of allowed login retries, umask settings, etc. It does not provide options to set the password policy. All changes apply only to newly created accounts! To change existing accounts, use the passwd and chage commands. Adjust the settings according to your corporate security policies.

Procedure

Edit file /etc/login.defs and make changes according to your policies.

PASS_MAX_DAYS   90
PASS_MIN_DAYS   7
PASS_WARN_AGE   14

This example sets default password expiration values for all newly created users:

• Password expires after 90 days

• Warns 14 days before the password expires

• Allows a user to change the password only every seven days

  The chage command prints information about the current password expiration state for a particular user.

  chage -l <user name>

Remark

It is also to possible to specify password expiration times and similar settings on a per-user basis using the useradd command. More information about password aging can be found in the SUSE Linux Enterprise Server 15 Hardening Guide, section 2.27 Enabling Password Aging.

Impact

• Some login.defs settings, like the password expiration time, reject users to login after their passwords have expired. These settings require system administrators to inform their users about the password expiration times.

• Users are required to actively change their passwords from time to time.

Priority

Medium

2.1.9 Setting up password failure counts for users #

 

Description

Password failure counts prevent users from logging in after a defined number of failed login attempts. SUSE Linux Enterprise Server provides this mechanism via the PAM system. We do not recommend to use password failure counts, as they can be misused for denial-of-service attacks of certain user accounts. If your corporate policy requires to setup password failure counts for users, refer to the SUSE Linux Enterprise Server 12 Hardening Guide, section 2.29.3 Locking User Accounts After Too Many Login Failures.

2.1.10 Setting up password strengthening for user accounts according to corporate policies #

 

Description

The default password policy for user accounts on a default SUSE Linux Enterprise Server system is already quite strong. For example, a password cracking library is used to prevent too simple and too short passwords. In some cases, it is required to configure the password strengthening exactly according to a corporate password policy. This is possible by changing the PAM password authentication settings in the file /etc/pam.d/common-password.

Use the pam-config utility to modify the PAM password strengthening settings. The changes are reflected in the file /etc/pam.d/common-password. Change the settings according to your requirements.

pam-config --add \
--cracklib-retry=3 \
--cracklib-minlen=8 \
--cracklib-lcredit=-1 \
--cracklib-ucredit=-1 \
--cracklib-dcredit=-1 \
--cracklib-ocredit=0 \
--cracklib-difok=5

This example configures the password strengthening according to the following rules:

• Ask user up to a maximum number of three times to enter a new valid password

• Minimum of eight characters

• At least one uppercase alpha character

• At least one lowercase alpha character

• At least one number

• An unlimited amount of special characters, such as _, !, %

  A new password must differ by at least five characters from the old password. More information on password strengthening options can be found in the man page man pam_cracklib.

Impact

• The passwords for system users have to be set according to the defined policies.

• The root user is allowed to overrule the password policy.

• When setting password expiration times, users can not login anymore after their passwords have expired.

Priority

Medium

2.1.11 Configuring user remote login restriction #

 

Description

Utilize access.conf to control remote access to the system for the root and any other user accounts. The configured accounts are restricted to log in from a certain IP subnet via SSH.

Procedure

1. Edit file /etc/pam.d/sshd and append:

   auth required pam_access.so

   See man access.conf for configuration details.

2. Edit file /etc/security/access.conf (see man access.conf for configuration details):

   + : <sid>adm : <network/netmask>
   + : sapadm : <network/netmask>
   + : <admin user> : <network/netmask>
   - : ALL : ALL

   

   Warning

   Do not use the pam-config utility here. It only supports pam_access as global module. The configuration above is not suitable to be used globally for all services and can cause a denial of access for the entire system!

Impact

• Only whitelisted users coming from the specified IP subnet are allowed to login via SSH.

• Remote root login is prohibited.

Priority

Medium

2.1.12 Setting up password for rescue mode #

 

Description

The root password is needed in rescue mode (rescue.target) to access the system. On SUSE Linux Enterprise operating systems no change has to be made.

2.1.13 Adjusting sysctl variables to improve network security #

 

Note

This section only covers settings for IPv4. There are similar IPv6 parameters available if required.

Description

sysctl (system control) variables change certain kernel parameters that influence the behavior of different parts of the operating system, such as the Linux network stack. These kernel parameters can be looked up in the proc file system, in /proc/sys/. Many kernel parameters can be directly changed by echo’ing a value into a parameter file. However, these changes are not persisted and are lost after a system reboot. Therefore we recommend to make all changes in the sysctl configuration file.

Procedure

Edit the /etc/sysctl.conf file and set or change the following variables:

net.ipv4.conf.default.rp_filter = 1
net.ipv4.conf.all.rp_filter = 1

This setting enables the reverse path filter in strict mode. The setting ensures that the answers to incoming IP packets are always sent out via the interface where the packet has been received. If the system would direct the answer packet to a different outgoing interface according to the routing table, this packet would be discarded. The setting prevents certain kind of IP spoofing attacks, such as those used for DDoS attacks.

net.ipv4.conf.default.accept_source_route = 0
net.ipv4.conf.all.accept_source_route = 0

This setting disables the acceptance of packets with the SRR option set in the IPv4 packet header. Packets that use “Source Routing” are rejected. This prevents IP packet redirection, such as a redirection to a host behind a firewall, that is not directly reachable.

net.ipv4.tcp_syncookies = 1

The TCP SYN Cookie Protection is enabled by default. A 'SYN Attack' is a denial of service attack that consumes all the resources on a machine. Any server that is connected to a network is potentially subject to this attack.

net.ipv4.icmp_echo_ignore_broadcasts = 1

ICMP echo requests (ping) can be sent to a broadcast address to scan a network for existing hosts / IPs or to perform a ICMP flood within a network segment. This setting ignores icmp echo packets, sent to a broadcast address.

net.ipv4.icmp_ignore_bogus_error_responses = 1

This setting avoids filling up log files with unnecessary error messages coming from invalid responses to broadcast frames. See RFC 1122 'Requirements for Internal Hosts - Communication Layers' for more information.

net.ipv4.conf.default.secure_redirects = 0
net.ipv4.conf.all.secure_redirects = 0

Accepting "secure" ICMP redirects (from those gateways listed as default gateways) has few legitimate uses. It should be disabled unless it is absolutely required.

net.ipv4.conf.default.accept_redirects = 0
net.ipv4.conf.all.accept_redirects = 0

This disables the acceptance of ICMP redirect messages. These messages are usually sent by gateways to inform a host about a better route to an outside network. These redirects can be misused, for example for man-in-the-middle attacks.

net.ipv4.tcp_max_syn_backlog = 4096

The TCP SYN backlog defines the number of SYN packets that are queued for further processing. When the queue limit is exceeded, all new incoming syn-packets are dropped. This improves the protection against TCP SYN flood attacks.

net.ipv4.ip_forward = 0

IP forwarding is the IP routing functionality of a Linux system. SAP HANA systems should never act as routers. Therefore IP forwarding is disabled.

net.ipv4.conf.default.send_redirects = 0
net.ipv4.conf.all.send_redirects = 0

IP redirects should only be sent by routers / gateways. As SAP HANA systems do not act as gateways, redirects are disabled.

Impact

• This changes the behavior of the IP network stack, which might cause some network problems or performance issues with certain network setups and devices (such as firewalls) in some rare cases.

Priority

High

2.1.14 Changing home directory permissions from 755 to 700 #

 

Description

By default, home directories of users are accessible (read, execute) by all other users on the system. As this is a potential information leak, home directories should only be accessible by their owners. SAP HANA system users ('<sid>adm') have their home directories in the directories /usr/sap/<sid>/home/. As this directory structure is in the domain of SAP, we do not describe any changes here.

Procedure

The following commands will set the permissions to 700 (directory only accessible for the user) for all home directories in /home:

chmod 755 /home
for a in /home/*; do echo "Changing rights for directory $a"; chmod 700 ”$a”; done

Impact

• System users are not allowed anymore to access other users home directories.

• An exception is made to '<sid>adm' users with their home directories in /usr/sap/<sid>/home.

Priority

Medium

2.1.15 Modifying permissions on certain system files #

 

Description

Many system files are group- or world-readable by default. For those files that carry sensitive information, this can be a security risk. Changing the file permissions of these files to more restrictive values increases the security. SUSE provides the tool chkstat to check and set file permissions of certain files that are defined in one of the following configuration files:

permissions.local
permissions.easy
permissions.paranoid
permissions.secure

The permissions.local file is dedicated for user-defined file permissions.

Procedure

For SAP HANA systems we recommend to use the permissions.easy pattern plus some additional file permissions that will be stored in the permissions.local pattern.

First set the permissions in the correct order in /etc/sysconfig/security:

...
PERMISSION_SECURITY="easy local"
...

Then add the following permission settings to the file /etc/permissions.local:

#
# HANA Security Hardening
#
/etc/at.allow                   root:root       0400
/etc/bash.bashrc                root:root       0444
/etc/csh.cshrc                  root:root       0444
/etc/csh.login                  root:root       0444
/etc/shadow                     root:shadow     0440
/etc/rsyslog.conf               root:root       0400
/etc/crontab                    root:root       0400
/etc/cron.d                     root:root       0700
/etc/cron.hourly                root:root       0700
/etc/cron.daily                 root:root       0700
/etc/cron.weekly                root:root       0700
/etc/cron.monthly               root:root       0700
/etc/login.defs                 root:root       0400
/etc/security/access.conf       root:root       0400
/etc/sysctl.conf                root:root       0400
/etc/X11/xdm/Xservers           root:root       0444
/root                           root:root       0700
/root/.cshrc                    root:root       0400
/var/log/boot.log               root:root       0640
/var/log/sa                     root:root       0770
#
# Changing permissions of utmp files would cause the commands
# w, who and last not to work anymore for non-root users
#
# Uncomment these lines, if you are really sure about that
/var/run/utmp                   root:utmp       0600
/var/log/wtmp                   root:utmp       0600

Now apply the permissions:

chkstat --system --set

Impact

• Some system administration tasks that require access to files mentioned above and that are usually performed as normal system user have to be performed as root user.

Priority

Medium

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 SAP HANA itself. For details consult the SAP HANA Security Guide (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. 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. From there, it retrieves the necessary keys automatically to unlock the data. The key server should by any means be a dedicated security-hardened and protected system, since anyone with access to this system can retrieve the keys and decrypt the data.

The SUSE Linux Enterprise Server for SAP Applications guide describes the setup of client and server in section 10 Encrypting Directories Using cryptctl.

Even though, this guide already covers most security hardening topics, we are planning to do further improvements. Also, later versions of SAP HANA might have changed or new requirements on the hardening settings, the firewall or the minimal package selection. 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 in the resource library on the SUSE website.

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, please 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.

v1.3

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