AlmaLinux OS 9 must force a frequent session key renegotiation for SSH connections to the server.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-269120	ALMA-09-003650	SV-269120r1050610_rule		Medium

Description

Without confidentiality protection mechanisms, unauthorized individuals may gain access to sensitive information via a remote access session. Remote access is access to DOD nonpublic information systems by an authorized user (or an information system) communicating through an external, nonorganization-controlled network. Remote access methods include, for example, dial-up, broadband, and wireless. Encryption provides a means to secure the remote connection to prevent unauthorized access to the data traversing the remote access connection (e.g., RDP), thereby providing a degree of confidentiality. The encryption strength of a mechanism is selected based on the security categorization of the information. Session key regeneration limits the chances of a session key becoming compromised.

STIG	Date
CloudLinux AlmaLinux OS 9 Security Technical Implementation Guide	2025-05-22

Details

Check Text (C-73151r1047736_chk)

Verify the SSH server is configured to force frequent session key renegotiation with the following command:

$ sshd -T | grep rekeylimit

rekeylimit 1073741824 3600

If "RekeyLimit" does not have a maximum data amount and maximum time defined, this is a finding.

Fix Text (F-73052r1049131_fix)

Configure AlmaLinux OS 9 to force a frequent session key renegotiation for SSH connections to the server by running the following command:

$ echo "RekeyLimit 1G 1h" > /etc/ssh/sshd_config.d/40-rekeylimit.conf