Guide to the Secure Configuration of Kylin Server 10
Rules, Groups, and Values defined within the XCCDF Benchmark
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Disable Host-Based Authentication
SSH's cryptographic host-based authentication is more secure than <code>.rhosts</code> authentication. However, it is not recommended that hosts unilaterally trust one another, even within an organ...Rule Medium Severity -
Allow Only SSH Protocol 2
Only SSH protocol version 2 connections should be permitted. The default setting in <code>/etc/ssh/sshd_config</code> is correct, and can be verified by ensuring that the following line appears: <p...Rule High Severity -
Disable SSH Access via Empty Passwords
Disallow SSH login with empty passwords. The default SSH configuration disables logins with empty passwords. The appropriate configuration is used if no value is set for <code>PermitEmptyPasswords<...Rule High Severity -
Disable PubkeyAuthentication Authentication
Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms. To disable PubkeyAuthentication authentication, add or correct the following line in <code>/etc/ssh/sshd_...Rule Medium Severity -
Disable SSH Support for .rhosts Files
SSH can emulate the behavior of the obsolete rsh command in allowing users to enable insecure access to their accounts via <code>.rhosts</code> files. <br> The default SSH configuration disables su...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 -
Do Not Allow SSH Environment Options
Ensure that users are not able to override environment variables of the SSH daemon. <br> The default SSH configuration disables environment processing. The appropriate configuration is used if no v...Rule Medium Severity -
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 -
Disable DHCP Server
The DHCP server <code>dhcpd</code> is not installed or activated by default. If the software was installed and activated, but the system does not need to act as a DHCP server, it should be disabled...Group -
Disable DHCP Service
The <code>dhcpd</code> service should be disabled on any system that does not need to act as a DHCP server. The <code>dhcpd</code> service can be disabled with the following command: <pre>$ sudo s...Rule Medium Severity -
Remove tftp Daemon
Trivial File Transfer Protocol (TFTP) is a simple file transfer protocol, typically used to automatically transfer configuration or boot files between systems. TFTP does not support authentication ...Rule Low Severity -
SNMP Server
The Simple Network Management Protocol allows administrators to monitor the state of network devices, including computers. Older versions of SNMP were well-known for weak security, such as plaintex...Group -
Disable SNMP Server if Possible
The system includes an SNMP daemon that allows for its remote monitoring, though it not installed by default. If it was installed and activated but is not needed, the software should be disabled an...Group -
Uninstall net-snmp Package
Thenet-snmp
package provides the snmpd service. Thenet-snmp
package can be removed with the following command:$ sudo dnf remove net-snmp
Rule Unknown Severity -
SSH Server
The SSH protocol is recommended for remote login and remote file transfer. SSH provides confidentiality and integrity for data exchanged between two systems, as well as server authentication, throu...Group -
SSH Max authentication attempts
Specify the maximum number of authentication attempts per connection.Value -
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
Theopenssh-server
package should be installed. Theopenssh-server
package can be installed with the following command:$ sudo dnf install openssh-server
Rule Medium Severity -
Verify User Who Owns shadow File
To properly set the owner of/etc/shadow
, run the command:$ sudo chown root /etc/shadow
Rule Medium Severity -
Verify Permissions on group File
To properly set the permissions of/etc/group
, run the command:$ sudo chmod 0644 /etc/group
Rule Medium Severity -
Verify Permissions on passwd File
To properly set the permissions of/etc/passwd
, run the command:$ sudo chmod 0644 /etc/passwd
Rule Medium Severity -
Verify Permissions on shadow File
To properly set the permissions of/etc/shadow
, run the command:$ sudo chmod 0000 /etc/shadow
Rule Medium Severity -
Restrict Dynamic Mounting and Unmounting of Filesystems
Linux includes a number of facilities for the automated addition and removal of filesystems on a running system. These facilities may be necessary in many environments, but this capability also ca...Group -
Disable the Automounter
The <code>autofs</code> daemon mounts and unmounts filesystems, such as user home directories shared via NFS, on demand. In addition, autofs can be used to handle removable media, and the default c...Rule Medium Severity -
Restrict Programs from Dangerous Execution Patterns
The recommendations in this section are designed to ensure that the system's features to protect against potentially dangerous program execution are activated. These protections are applied at the ...Group -
Disable Core Dumps
A core dump file is the memory image of an executable program when it was terminated by the operating system due to errant behavior. In most cases, only software developers legitimately need to acc...Group -
Disable Core Dumps for All Users
To disable core dumps for all users, add the following line to <code>/etc/security/limits.conf</code>, or to a file within the <code>/etc/security/limits.d/</code> directory: <pre>* hard core...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 Private *_key Key Files
SSH server private keys - files that match the <code>/etc/ssh/*_key</code> glob, have to have restricted permissions. If those files are owned by the <code>root</code> user and the <code>root</code...Rule Medium Severity -
Configure OpenSSH Server if Necessary
If the system needs to act as an SSH server, then certain changes should be made to the OpenSSH daemon configuration file <code>/etc/ssh/sshd_config</code>. The following recommendations can be app...Group -
System Settings
Contains rules that check correct system settings.Group -
Installing and Maintaining Software
The following sections contain information on security-relevant choices during the initial operating system installation process and the setup of software updates.Group -
System and Software Integrity
System and software integrity can be gained by installing antivirus, increasing system encryption strength with FIPS, verifying installed software, enabling SELinux, installing an Intrusion Prevent...Group -
Software Integrity Checking
Both the AIDE (Advanced Intrusion Detection Environment) software and the RPM package management system provide mechanisms for verifying the integrity of installed software. AIDE uses snapshots of ...Group -
Verify Integrity with AIDE
AIDE conducts integrity checks by comparing information about files with previously-gathered information. Ideally, the AIDE database is created immediately after initial system configuration, and t...Group -
Install AIDE
Theaide
package can be installed with the following command:$ sudo dnf install aide
Rule Medium Severity -
Sudo
<code>Sudo</code>, which stands for "su 'do'", provides the ability to delegate authority to certain users, groups of users, or system administrators. When configured for system users and/or groups...Group -
Sudo - logfile value
Specify the sudo logfile to use. The default value used here matches the example location from CIS, which uses /var/log/sudo.log.Value -
Ensure Only Users Logged In To Real tty Can Execute Sudo - sudo use_pty
The sudo <code>use_pty</code> tag, when specified, will only execute sudo commands from users logged in to a real tty. This should be enabled by making sure that the <code>use_pty</code> tag exists...Rule Medium Severity -
Ensure Sudo Logfile Exists - sudo logfile
A custom log sudo file can be configured with the 'logfile' tag. This rule configures a sudo custom logfile at the default location suggested by CIS, which uses /var/log/sudo.log.Rule Low Severity -
The operating system must restrict privilege elevation to authorized personnel
The sudo command allows a user to execute programs with elevated (administrator) privileges. It prompts the user for their password and confirms your request to execute a command by checking a file...Rule Medium Severity -
Don't target root user in the sudoers file
The targeted users of a user specification should be, as much as possible, non privileged users (i.e.: non-root). User specifications have to explicitly list the runas spec (i.e. the list of targe...Rule Medium Severity -
Protect Accounts by Restricting Password-Based Login
Conventionally, Unix shell accounts are accessed by providing a username and password to a login program, which tests these values for correctness using the <code>/etc/passwd</code> and <code>/etc/...Group -
Ensure All Accounts on the System Have Unique User IDs
Change user IDs (UIDs), or delete accounts, so each has a unique name.Rule Medium Severity -
Ensure There Are No Accounts With Blank or Null Passwords
Check the "/etc/shadow" file for blank passwords with the following command: <pre>$ sudo awk -F: '!$2 {print $1}' /etc/shadow</pre> If the command returns any results, this is a finding. Configure ...Rule High Severity -
Verify No netrc Files Exist
The <code>.netrc</code> files contain login information used to auto-login into FTP servers and reside in the user's home directory. These files may contain unencrypted passwords to remote FTP serv...Rule Medium Severity -
Ensure cron Is Logging To Rsyslog
Cron logging must be implemented to spot intrusions or trace cron job status. If <code>cron</code> is not logging to <code>rsyslog</code>, it can be implemented by adding the following to the <i>RU...Rule Medium Severity -
Configure Periodic Execution of AIDE
At a minimum, AIDE should be configured to run a weekly scan. To implement a daily execution of AIDE at 4:05am using cron, add the following line to <code>/etc/crontab</code>: <pre>05 4 * * * root ...Rule Medium Severity -
GNOME Desktop Environment
GNOME is a graphical desktop environment bundled with many Linux distributions that allow users to easily interact with the operating system graphically rather than textually. The GNOME Graphical D...Group
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