Canonical Ubuntu 20.04 LTS Security Technical Implementation Guide (STIG) V1R12
Rules and Groups employed by this XCCDF Profile
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Set SSH Client Alive Count Max
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 -
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 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 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 -
Enable PAM
UsePAM Enables the Pluggable Authentication Module interface. If set to “yes” this will enable PAM authentication using ChallengeResponseAuthentication and PasswordAuthentication in addition to PAM...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 SSH Warning Banner
To enable the warning banner and ensure it is consistent across the system, add or correct the following line in <code>/etc/ssh/sshd_config</code>: <pre>Banner /etc/issue.net</pre> Another sectio...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 -
Use Only FIPS 140-2 Validated Key Exchange Algorithms
Limit the key exchange algorithms to those which are FIPS-approved. Add or modify the following line in <code>/etc/ssh/sshd_config</code> <pre>KexAlgorithms ecdh-sha2-nistp256,ecdh-sha2-ni...Rule Medium 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 -
Prevent remote hosts from connecting to the proxy display
The SSH daemon should prevent remote hosts from connecting to the proxy display. <br> The default SSH configuration for <code>X11UseLocalhost</code> is <code>yes</code>, which prevents remote hosts...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 -
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 -
Lock Accounts After Failed Password Attempts
This rule configures the system to lock out accounts after a number of incorrect login attempts using <code>pam_faillock.so</code>. pam_faillock.so module requires multiple entries in pam files. Th...Rule Medium Severity -
Set Interval For Counting Failed Password Attempts
Utilizing <code>pam_faillock.so</code>, the <code>fail_interval</code> directive configures the system to lock out an account after a number of incorrect login attempts within a specified time peri...Rule Medium Severity -
Do Not Show System Messages When Unsuccessful Logon Attempts Occur
This rule ensures the system prevents informative messages from being presented to the user pertaining to logon information after a number of incorrect login attempts using <code>pam_faillock.so</c...Rule Medium Severity -
Set Lockout Time for Failed Password Attempts
This rule configures the system to lock out accounts during a specified time period after a number of incorrect login attempts using <code>pam_faillock.so</code>. Ensure that the file <code>/etc/s...Rule Medium Severity -
Restrict Access to Kernel Message Buffer
To set the runtime status of the <code>kernel.dmesg_restrict</code> kernel parameter, run the following command: <pre>$ sudo sysctl -w kernel.dmesg_restrict=1</pre> To make sure that the setting is...Rule Low Severity
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