RHEL-10-700660 - RHEL 10 must be configured so that all network connections associated with Secure Shell (SSH) traffic terminate after becoming unresponsive.

Information

Terminating an idle 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. 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 the operating system terminates all sessions or network access; it only ends the inactive session and releases the resources associated with that session.

RHEL 10 uses "/etc/ssh/sshd_config" for configurations of OpenSSH. Within the sshd_config, the product of the values of "ClientAliveInterval" and "ClientAliveCountMax" are used to establish the inactivity threshold. The "ClientAliveInterval" is a timeout interval in seconds after which if no data has been received from the client, sshd will send a message through the encrypted channel to request a response from the client. The "ClientAliveCountMax" is the number of client alive messages that may be sent without sshd receiving any messages back from the client. If this threshold is met, sshd will disconnect the client. For more information on these settings and others, refer to the sshd_config man pages.

OpenSSH uses the first occurrence of a keyword it sees, and drop-in files are read in lexicographical order at the start of the configuration. Red Hat recommends using drop-in files rather than changing base configuration files.

Satisfies: SRG-OS-000163-GPOS-00072, SRG-OS-000279-GPOS-00109

Solution

Configure RHEL 10 to automatically terminate all network connections associated with SSH traffic at the end of a session or after 10 minutes of inactivity.

In "/etc/ssh/sshd_config.d", create a drop file that will lexicographically precede 50-redhat.conf and add the following line:

ClientAliveCountMax 1

Restart the SSH daemon with the following command for the changes to take effect:

$ sudo systemctl restart sshd.service

Item Details

Audit Name: DISA Red Hat Enterprise Linux 10 STIG v1r1

Category: ACCESS CONTROL, SYSTEM AND COMMUNICATIONS PROTECTION

Plugin: Unix

Control ID: 856a62c4c84efc0ce3f7f1a466fc96460002ae5fa9821bbe65fa3a7f65f7eaf6

Detections

Analytics

RHEL-10-700660 - RHEL 10 must be configured so that all network connections associated with Secure Shell (SSH) traffic terminate after becoming unresponsive.

Information

Solution

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Item Details