Check: AZLX-23-001250
Amazon Linux 2023 STIG:
AZLX-23-001250
(in version v1 r1)
Title
Amazon Linux 2023 must be configured so that all network connections associated with SSH traffic terminate after becoming unresponsive. (Cat II impact)
Discussion
Terminating an idle 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 session will also free up resources committed by the managed network element. Terminating network connections associated with communications sessions includes, for example, de-allocating associated TCP/IP address/port pairs at Amazon Linux 2023 level, and de-allocating networking assignments at the application level if multiple application sessions are using a single operating system-level network connection. This does not mean that Amazon Linux 2023 terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session. Satisfies: SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109
Check Content
Verify Amazon Linux 2023 SSHD has the "ClientAliveCountMax" set to "1" by performing the following command: $ sudo /usr/sbin/sshd -dd 2>&1 | awk '/filename/ {print $4}' | tr -d '\r' | tr '\n' ' ' | xargs sudo grep -iH '^\s*clientalivecountmax' /etc/ssh/sshd_config.d/92-ClientAliveCountMax.conf:ClientAliveCountMax 1 If "ClientAliveCountMax" do not exist, is not set to a value of "1" in "/etc/ssh/sshd_config" or a dropfile in "/etc/ssh/sshd_config.d" , or is commented out, this is a finding.
Fix Text
Configure Amazon Linux 2023 SSHD to terminate a user session automatically after the SSH client has become unresponsive. Note: This setting must be applied in conjunction with AZLX-23-000820 to function correctly. Modify or append the following lines in the "/etc/ssh/sshd_config" file or a dropfile in "/etc/ssh/sshd_config.d": ClientAliveCountMax 1 For the changes to take effect, the SSH daemon must be restarted. $ sudo systemctl restart sshd.service
Additional Identifiers
Rule ID: SV-274051r1120141_rule
Vulnerability ID: V-274051
Group Title: SRG-OS-000163-GPOS-00072
Expert Comments
CCIs
| Number | Definition |
|---|---|
| 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. |