Guide to the Secure Configuration of SUSE Linux Enterprise 15
Rules, Groups, and Values defined within the XCCDF Benchmark
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Verify Group Who Owns /etc/sestatus.conf File
To properly set the group owner of/etc/sestatus.conf
, run the command:$ sudo chgrp root /etc/sestatus.conf
Rule Medium Severity -
Verify User Who Owns /etc/sestatus.conf File
To properly set the owner of/etc/sestatus.conf
, run the command:$ sudo chown root /etc/sestatus.conf
Rule Medium Severity -
Verify Permissions On /etc/sestatus.conf File
To properly set the permissions of/etc/sestatus.conf
, run the command:$ sudo chmod 0644 /etc/sestatus.conf
Rule Medium Severity -
Ensure No Daemons are Unconfined by SELinux
Daemons for which the SELinux policy does not contain rules will inherit the context of the parent process. Because daemons are launched during startup and descend from the <code>init</code> proces...Rule Medium Severity -
Restrict at and cron to Authorized Users if Necessary
The <code>/etc/cron.allow</code> and <code>/etc/at.allow</code> files contain lists of users who are allowed to use <code>cron</code> and at to delay execution of processes. If these files exist an...Group -
DHCP
The Dynamic Host Configuration Protocol (DHCP) allows systems to request and obtain an IP address and other configuration parameters from a server. <br> <br> This guide recommends configuring...Group -
Minimize the DHCP-Configured Options
Create the file <code>/etc/dhcp/dhclient.conf</code>, and add an appropriate setting for each of the ten configuration settings which can be obtained via DHCP. For each setting, do one of the follo...Rule Unknown Severity -
Uninstall bind Package
Thenamed
service is provided by thebind
package. Thebind
package can be removed with the following command:$ sudo zypper remove bind
Rule Low Severity -
Disable vsftpd Service
Thevsftpd
service can be disabled with the following command:$ sudo systemctl mask --now vsftpd.service
Rule Medium Severity -
Configure Firewalls to Protect the FTP Server
By default, <code>iptables</code> blocks access to the ports used by the web server. To configure <code>iptables</code> to allow port 21 traffic, one must edit <code>/etc/sysconfig/iptables</code>...Rule Unknown Severity -
Uninstall dovecot Package
Thedovecot
package can be removed with the following command:$ sudo zypper remove dovecot
Rule Unknown Severity -
Mail Server Software
Mail servers are used to send and receive email over the network. Mail is a very common service, and Mail Transfer Agents (MTAs) are obvious targets of network attack. Ensure that systems are not r...Group -
Configure System to Forward All Mail For The Root Account
Make sure that mails delivered to root user are forwarded to a monitored email address. Make sure that the address <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_postfix_root_mail_ali...Rule Medium Severity -
Uninstall nfs-utils Package
Thenfs-utils
package can be removed with the following command:$ sudo zypper remove nfs-utils
Rule Low Severity -
Disable rpcbind Service
The rpcbind utility maps RPC services to the ports on which they listen. RPC processes notify rpcbind when they start, registering the ports they are listening on and the RPC program numbers they e...Rule Low Severity -
Mount Remote Filesystems with Restrictive Options
Edit the file <code>/etc/fstab</code>. For each filesystem whose type (column 3) is <code>nfs</code> or <code>nfs4</code>, add the text <code>,nodev,nosuid</code> to the list of mount options in co...Group -
Network Time Protocol
The Network Time Protocol is used to manage the system clock over a network. Computer clocks are not very accurate, so time will drift unpredictably on unmanaged systems. Central time protocols can...Group -
The Chrony package is installed
System time should be synchronized between all systems in an environment. This is typically done by establishing an authoritative time server or set of servers and having all systems synchronize th...Rule Medium Severity -
Enable the NTP Daemon
Run the following command to determine the current status of the <code>chronyd</code> service: <pre>$ sudo systemctl is-active chronyd</pre> If the service is running, it should return the follo...Rule Medium Severity -
Enable the NTP Daemon
Thentp
service can be enabled with the following command:$ sudo systemctl enable ntp.service
Rule High Severity -
Enable Use of Privilege Separation
When enabled, SSH will create an unprivileged child process that has the privilege of the authenticated user. To enable privilege separation in SSH, add or correct the following line in the <code>/...Rule Medium Severity -
A remote time server for Chrony is configured
<code>Chrony</code> is a daemon which implements the Network Time Protocol (NTP). It is designed to synchronize system clocks across a variety of systems and use a source that is highly accurate. M...Rule Medium Severity -
Configure Time Service Maxpoll Interval
The <code>maxpoll</code> should be configured to <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_time_service_set_maxpoll" use="legacy"></xccdf-1.2:sub> in <code>/etc/ntp.conf</code> o...Rule Medium Severity -
Verify Group Who Owns /etc/chrony.keys File
To properly set the group owner of/etc/chrony.keys
, run the command:$ sudo chgrp chrony /etc/chrony.keys
Rule Medium Severity -
Verify User Who Owns /etc/chrony.keys File
To properly set the owner of/etc/chrony.keys
, run the command:$ sudo chown root /etc/chrony.keys
Rule Medium Severity -
Verify Permissions On /etc/chrony.keys File
To properly set the permissions of/etc/chrony.keys
, run the command:$ sudo chmod 0640 /etc/chrony.keys
Rule Medium Severity -
Obsolete Services
This section discusses a number of network-visible services which have historically caused problems for system security, and for which disabling or severely limiting the service has been the best a...Group -
Uninstall ypserv Package
Theypserv
package can be removed with the following command:$ sudo zypper remove ypserv
Rule High Severity -
Uninstall rsh-server Package
Thersh-server
package can be removed with the following command:$ sudo zypper remove rsh-server
Rule High Severity -
Remove Rsh Trust Files
The files <code>/etc/hosts.equiv</code> and <code>~/.rhosts</code> (in each user's home directory) list remote hosts and users that are trusted by the local system when using the rshd daemon. To re...Rule High Severity -
Remove User Host-Based Authentication Files
The <code>~/.shosts</code> (in each user's home directory) files list remote hosts and users that are trusted by the local system. To remove these files, run the following command to delete them fr...Rule High Severity -
Uninstall telnet-server Package
Thetelnet-server
package can be removed with the following command:$ sudo zypper remove telnet-server
Rule High Severity -
Disable Quagga Service
Thezebra
service can be disabled with the following command:$ sudo systemctl mask --now zebra.service
Rule Medium Severity -
Uninstall Samba Package
Thesamba
package can be removed with the following command:$ sudo zypper remove samba
Rule Unknown Severity -
SSH is required to be installed
Specify if the Policy requires SSH to be installed. Used by SSH Rules to determine if SSH should be uninstalled or configured.<br> A value of 0 means that the policy doesn't care if OpenSSH server ...Value -
Install the OpenSSH Server Package
The <code>openssh-server</code> package should be installed. The <code>openssh-server</code> package can be installed with the following command: <pre> $ sudo zypper install openssh-server</pre> ...Rule Medium Severity -
Install the OpenSSH Client and Server Package
Theopenssh
package should be installed. Theopenssh
package can be installed with the following command:$ sudo zypper install openssh
Rule Medium Severity -
Remove the OpenSSH Server Package
Theopenssh-server
package should be removed. Theopenssh-server
package can be removed with the following command:$ sudo zypper remove openssh-server
Rule Medium Severity -
Remove the OpenSSH Client and Server Package
Theopenssh
package should be removed. Theopenssh
package can be removed with the following command:$ sudo zypper remove openssh
Rule Medium Severity -
Enable the OpenSSH Service
The SSH server service, sshd, is commonly needed. Thesshd
service can be enabled with the following command:$ sudo systemctl enable sshd.service
Rule Medium Severity -
Verify Permissions on SSH Server config file
To properly set the permissions of/etc/ssh/sshd_config
, run the command:$ sudo chmod 0600 /etc/ssh/sshd_config
Rule Medium Severity -
Remove SSH Server iptables Firewall exception (Unusual)
By default, inbound connections to SSH's port are allowed. If the SSH server is not being used, this exception should be removed from the firewall configuration. <br> <br> Edit the files <co...Rule Unknown Severity -
Set SSH Client Alive Interval
SSH allows administrators to set a network responsiveness timeout interval. After this interval has passed, the unresponsive client will be automatically logged out. <br> <br> To set this t...Rule Medium Severity -
Disable SSH Root Login
The root user should never be allowed to login to a system directly over a network. To disable root login via SSH, add or correct the following line in <code>/etc/ssh/sshd_config</code>: <pre>Pe...Rule Medium Severity -
Disable X11 Forwarding
The X11Forwarding parameter provides the ability to tunnel X11 traffic through the connection to enable remote graphic connections. SSH has the capability to encrypt remote X11 connections when SSH...Rule Medium Severity -
Enable Public Key Authentication
Enable SSH login with public keys. <br> The default SSH configuration enables authentication based on public keys. The appropriate configuration is used if no value is set for <code>PubkeyAuthentic...Rule Medium Severity -
Enable Encrypted X11 Forwarding
By default, remote X11 connections are not encrypted when initiated by users. SSH has the capability to encrypt remote X11 connections when SSH's <code>X11Forwarding</code> option is enabled. <br> ...Rule High Severity -
Enable SSH Print Last Log
Ensure that SSH will display the date and time of the last successful account logon. <br> The default SSH configuration enables print of the date and time of the last login. The appropriate configu...Rule Medium Severity -
Set SSH Daemon LogLevel to VERBOSE
The <code>VERBOSE</code> parameter configures the SSH daemon to record login and logout activity. To specify the log level in SSH, add or correct the following line in <code>/etc/ssh/sshd_config<...Rule Medium Severity -
Audit failure mode
This variable is the setting for the -f option in Audit configuration which sets the failure mode of audit. This option lets you determine how you want the kernel to handle critical errors. Possibl...Value
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