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

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-257994	RHEL-09-255090	SV-257994r958908_rule		Medium

Description
Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered. This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification. Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa. Session key regeneration limits the chances of a session key becoming compromised. Satisfies: SRG-OS-000423-GPOS-00187, SRG-OS-000033-GPOS-00014, SRG-OS-000424-GPOS-00188

Description

Without protection of the transmitted information, confidentiality and integrity may be compromised because unprotected communications can be intercepted and either read or altered. This requirement applies to both internal and external networks and all types of information system components from which information can be transmitted (e.g., servers, mobile devices, notebook computers, printers, copiers, scanners, and facsimile machines). Communication paths outside the physical protection of a controlled boundary are exposed to the possibility of interception and modification. Protecting the confidentiality and integrity of organizational information can be accomplished by physical means (e.g., employing physical distribution systems) or by logical means (e.g., employing cryptographic techniques). If physical means of protection are employed, then logical means (cryptography) do not have to be employed, and vice versa. Session key regeneration limits the chances of a session key becoming compromised. Satisfies: SRG-OS-000423-GPOS-00187, SRG-OS-000033-GPOS-00014, SRG-OS-000424-GPOS-00188

STIG	Date
Red Hat Enterprise Linux 9 Security Technical Implementation Guide	2024-06-04

Details

Check Text ( C-61735r952193_chk )
Verify the SSH server is configured to force frequent session key renegotiation with the following command: $ sudo /usr/sbin/sshd -dd 2>&1 \| awk '/filename/ {print $4}' \| tr -d '\r' \| tr '\n' ' ' \| xargs sudo grep -iH '^\s*rekeylimit' RekeyLimit 1G 1h If "RekeyLimit" does not have a maximum data amount and maximum time defined, is missing, or is commented out, this is a finding.

Fix Text (F-61659r925968_fix)
Configure RHEL 9 to force a frequent session key renegotiation for SSH connections to the server by adding or modifying the following line in the "/etc/ssh/sshd_config" file: RekeyLimit 1G 1h Restart the SSH daemon for the settings to take effect. $ sudo systemctl restart sshd.service