The SSH daemon must restrict login ability to specific users and/or groups.

From Oracle Linux 5 Security Technical Implementation Guide

Associated with: CCI-000225

SV-63727r1_rule The SSH daemon must restrict login ability to specific users and/or groups.

Vulnerability discussion

Restricting SSH logins to a limited group of users, such as system administrators, prevents password-guessing and other SSH attacks from reaching system accounts and other accounts not authorized for SSH access.

Check content

There are two ways in which access to SSH may restrict users or groups. Check if /etc/pam.d/sshd is configured to require daemon style login control. # grep pam_access.so /etc/pam.d/sshd|grep "required"|grep "account"| grep -v '^#' If no lines are returned, sshd is not configured to use pam_access. Check the SSH daemon configuration for the AllowGroups setting. # egrep -i "AllowGroups|AllowUsers" /etc/ssh/sshd_config | grep -v '^#' If no lines are returned, sshd is not configured to limit access to users/groups. If sshd is not configured to limit access either through pam_access or the use "AllowUsers" or "AllowGroups", this is a finding.

Fix text

Edit the SSH daemon configuration and add an "AllowGroups" or "AllowUsers" directive specifying the groups and users allowed to have access. Restart the SSH daemon. # /sbin/service sshd restart Alternatively, modify the /etc/pam.d/sshd file to include the line account required pam_access.so accessfile= If the "accessfile" option is not specified the default "access.conf" file will be used. The "access.conf" file must contain the user restriction definitions.

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