Title

TOSS must be configured to prevent unrestricted mail relaying. (Cat II impact)

Discussion

If unrestricted mail relaying is permitted, unauthorized senders could use this host as a mail relay for the purpose of sending spam or other unauthorized activity.

Check Content

Verify the system is configured to prevent unrestricted mail relaying. Determine if "postfix" is installed with the following commands: $ sudo yum list installed postfix postfix.x86_64 2:3.5.8-2.el8 If postfix is not installed, this is Not Applicable. If postfix is installed, determine if it is configured to reject connections from unknown or untrusted networks with the following command: $ sudo postconf -n smtpd_client_restrictions smtpd_client_restrictions = permit_mynetworks, reject If the "smtpd_client_restrictions" parameter contains any entries other than "permit_mynetworks" and "reject", this is a finding.

Fix Text

If "postfix" is installed, modify the "/etc/postfix/main.cf" file to restrict client connections to the local network with the following command: $ sudo postconf -e 'smtpd_client_restrictions = permit_mynetworks,reject'

Additional Identifiers

Rule ID: SV-253111r991589_rule

Vulnerability ID: V-253111

Group Title: SRG-OS-000480-GPOS-00227

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.