Guide to the Secure Configuration of Ubuntu 22.04
Rules, Groups, and Values defined within the XCCDF Benchmark
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Ensure SSH LoginGraceTime is configured
The <code>LoginGraceTime</code> parameter to the SSH server specifies the time allowed for successful authentication to the SSH server. The longer the Grace period is the more open unauthenticated ...Rule Medium Severity -
Set SSH authentication attempt limit
The <code>MaxAuthTries</code> parameter specifies the maximum number of authentication attempts permitted per connection. Once the number of failures reaches half this value, additional failures ar...Rule Medium Severity -
Set SSH MaxSessions limit
The <code>MaxSessions</code> parameter specifies the maximum number of open sessions permitted from a given connection. To set MaxSessions edit <code>/etc/ssh/sshd_config</code> as follows: <pre>Ma...Rule Medium Severity -
Ensure SSH MaxStartups is configured
The MaxStartups parameter specifies the maximum number of concurrent unauthenticated connections to the SSH daemon. Additional connections will be dropped until authentication succeeds or the Login...Rule Medium Severity -
Use Only FIPS 140-2 Validated Ciphers
Limit the ciphers to those algorithms which are FIPS-approved. The following line in <code>/etc/ssh/sshd_config</code> demonstrates use of FIPS-approved ciphers: <pre>Ciphers <xccdf-1.2:sub idref="...Rule Medium 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 -
Use Only Strong Ciphers
Limit the ciphers to strong algorithms. Counter (CTR) mode is also preferred over cipher-block chaining (CBC) mode. The following line in <code>/etc/ssh/sshd_config</code> demonstrates use of those...Rule Medium Severity -
Use Only Strong Key Exchange algorithms
Limit the Key Exchange to strong algorithms. The following line in <code>/etc/ssh/sshd_config</code> demonstrates use of those: <pre>KexAlgorithms <xccdf-1.2:sub idref="xccdf_org.ssgproject.content...Rule Medium Severity -
System Security Services Daemon
The System Security Services Daemon (SSSD) is a system daemon that provides access to different identity and authentication providers such as Red Hat's IdM, Microsoft's AD, openLDAP, MIT Kerberos, ...Group -
Configure SSSD to Expire Offline Credentials
SSSD should be configured to expire offline credentials after 1 day. To configure SSSD to expire offline credentials, set <code>offline_credentials_expiration</code> to <code>1</code> under the <c...Rule Medium Severity -
X Window System
The X Window System implementation included with the system is called X.org.Group -
Disable X Windows
Unless there is a mission-critical reason for the system to run a graphical user interface, ensure X is not set to start automatically at boot and remove the X Windows software packages. There is u...Group -
SSH Strong MACs by FIPS
Specify the FIPS approved MACs (Message Authentication Code) algorithms that are used for data integrity protection by the SSH server.Value -
Enforce Usage of pam_wheel with Group Parameter for su Authentication
To ensure that only users who are members of the group set in the <code>group</code> option of <code>pam_wheel.so</code> module can run commands with altered privileges through the <code>su</code> ...Rule Medium Severity -
Ensure users own their home directories
The user home directory is space defined for the particular user to set local environment variables and to store personal files. Since the user is accountable for files stored in the user home dire...Rule Medium Severity -
Ensure /dev/shm is configured
The <code>/dev/shm</code> is a traditional shared memory concept. One program will create a memory portion, which other processes (if permitted) can access. If <code>/dev/shm</code> is not configur...Rule Low Severity -
Ensure PAM Displays Last Logon/Access Notification
To configure the system to notify users of last logon/access using <code>pam_lastlog</code>, add or correct the <code>pam_lastlog</code> settings in <code>/etc/pam.d/login</code> to include <code>s...Rule Low Severity -
Prevent Login to Accounts With Empty Password
If an account is configured for password authentication but does not have an assigned password, it may be possible to log into the account without authentication. Remove any instances of the <code>...Rule High Severity -
Verify No .forward Files Exist
The.forwardfile specifies an email address to forward the user's mail to.Rule Medium Severity -
Restrict unprivileged access to the kernel syslog
Enforce restrictions on unprivileged users reading the kernel syslog via dmesg(8). The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To check the con...Rule Medium Severity -
Type of hostname to record the audit event
Type of hostname to record the audit eventValue -
Disable mutable hooks
Ensure kernel structures associated with LSMs are always mapped as read-only after system boot. The configuration that was used to build kernel is available at <code>/boot/config-*</code>. To ...Rule Medium Severity -
Ensure nftables Default Deny Firewall Policy
Base chain policy is the default verdict that will be applied to packets reaching the end of the chain. There are two policies: accept (Default) and drop. If the policy is set to accept, the firewa...Rule Medium Severity -
Ensure All Files Are Owned by a User
If any files are not owned by a user, then the cause of their lack of ownership should be investigated. Following this, the files should be deleted or assigned to an appropriate user. Locate the m...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 -
Add nosuid Option to /var
The <code>nosuid</code> mount option can be used to prevent execution of setuid programs in <code>/var</code>. The SUID and SGID permissions should not be required for this directory. Add the <code...Rule Medium Severity -
Set SSH Client Alive Count Max to zero
The SSH server sends at most <code>ClientAliveCountMax</code> messages during a SSH session and waits for a response from the SSH client. The option <code>ClientAliveInterval</code> configures time...Rule Medium 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 Kerberos Authentication
Unless needed, SSH should not permit extraneous or unnecessary authentication mechanisms like Kerberos. <br> The default SSH configuration disallows authentication validation through Kerberos. The ...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 Support for User Known Hosts
SSH can allow system users to connect to systems if a cache of the remote systems public keys is available. This should be disabled. <br> <br> To ensure this behavior is disabled, add or c...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 -
Set LogLevel to INFO
The INFO parameter specifices that record login and logout activity will be logged. <br> The default SSH configuration sets the log level to INFO. The appropriate configuration is used if no value ...Rule Low Severity -
Use Only Strong MACs
Limit the MACs to strong hash algorithms. The following line in <code>/etc/ssh/sshd_config</code> demonstrates use of those MACs: <pre>MACs <xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_...Rule Medium Severity -
Maximum audit log file size for auditd
The setting for max_log_file in /etc/audit/auditd.confValue -
Remote server for audispd to send audit records
The setting for remote_server in /etc/audisp/audisp-remote.confValue -
Account for auditd to send email when actions occurs
The setting for action_mail_acct in /etc/audit/auditd.confValue -
Action for auditd to take when disk space is low
The setting for admin_space_left_action in /etc/audit/auditd.confValue -
Appropriate Action Must be Setup When the Internal Audit Event Queue is Full
The audit system should have an action setup in the event the internal event queue becomes full. To setup an overflow action edit <code>/etc/audit/auditd.conf</code>. Set <code>overflow_action</cod...Rule Medium Severity -
Set type of computer node name logging in audit logs
To configure Audit daemon to use a unique identifier as computer node name in the audit events, set <code>name_format</code> to <code><xccdf-1.2:sub idref="xccdf_org.ssgproject.content_value_var_au...Rule Medium Severity -
Ensure the default plugins for the audit dispatcher are Installed
The audit-audispd-plugins package should be installed.Rule Medium Severity -
Action for auditd to take when log files reach their maximum size
The setting for max_log_file_action in /etc/audit/auditd.conf. The following options are available: <br>ignore - audit daemon does nothing. <br>syslog - audit daemon will issue a warning to syslog....Value -
Number of log files for auditd to retain
The setting for num_logs in /etc/audit/auditd.confValue -
Action for auditd to take when disk space just starts to run low
The setting for space_left_action in /etc/audit/auditd.confValue -
The percentage remaining in disk space before prompting space_left_action
The setting for space_left as a percentage in /etc/audit/auditd.confValue -
Enable Kernel Parameter to Ignore Bogus ICMP Error Responses on IPv4 Interfaces
To set the runtime status of the <code>net.ipv4.icmp_ignore_bogus_error_responses</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w net.ipv4.icmp_ignore_bogus_error_response...Rule Unknown Severity -
Use Only FIPS 140-2 Validated MACs
Limit the MACs to those hash algorithms which are FIPS-approved. The following line in <code>/etc/ssh/sshd_config</code> demonstrates use of FIPS-approved MACs: <pre>MACs <xccdf-1.2:sub idref="xccd...Rule Medium Severity -
Package "prelink" Must not be Installed
Theprelinkpackage can be removed with the following command:$ apt-get remove prelink
Rule Medium Severity -
Configure AIDE To Notify Personnel if Baseline Configurations Are Altered
The operating system file integrity tool must be configured to notify designated personnel of any changes to configurations.Rule Medium Severity -
Set GNOME3 Screensaver Inactivity Timeout
The idle time-out value for inactivity in the GNOME3 desktop is configured via the <code>idle-delay</code> setting must be set under an appropriate configuration file(s) in the <code>/etc/dconf/db/...Rule Medium Severity
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