Check: SLEM-05-255035
SUSE Linux Enterprise Micro (SLEM) 5 STIG:
SLEM-05-255035
(in version v1 r1)
Title
SLEM 5 must be configured so that all network connections associated with SSH traffic are terminated after 10 minutes of becoming unresponsive. (Cat II impact)
Discussion
Terminating an unresponsive SSH session within a short time period reduces the window of opportunity for unauthorized personnel to take control of a management session enabled on the console or console port that has been left unattended. In addition, quickly terminating an idle SSH session will also free up resources committed by the managed network element. Terminating network connections associated with communications sessions includes, for example, deallocating associated TCP/IP address/port pairs at the operating system level and deallocating networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. This does not mean that the operating system terminates all sessions or network access; it only ends the unresponsive session and releases the resources associated with that session.
Check Content
Verify the SSH server automatically terminates a user session after the SSH client has been unresponsive for 10 minutes by using the following command: > sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*clientaliveinterval' /etc/ssh/sshd_config:ClientAliveInterval 600 If "ClientAliveInterval" is not set to "600" or less, is commented out, missing, or conflicting results are returned, this is a finding.
Fix Text
Configure the SSH server to terminate a user session automatically after the SSH client has been unresponsive for 10 minutes. Add or modify the following line in the "/etc/ssh/sshd_config" file: ClientAliveInterval 600 The SSH daemon must be restarted for any changes to take effect: > systemctl restart sshd.service
Additional Identifiers
Rule ID: SV-261332r996462_rule
Vulnerability ID: V-261332
Group Title: SRG-OS-000126-GPOS-00066
Expert Comments
CCIs
| Number | Definition |
|---|---|
| CCI-000879 |
The organization terminates sessions and network connections when nonlocal maintenance is completed. |
| CCI-001133 |
Terminate the network connection associated with a communications session at the end of the session or after an organization-defined time period of inactivity. |
| CCI-002361 |
Automatically terminate a user session after organization-defined conditions or trigger events requiring session disconnect. |