The SUSE operating system must implement DoD-approved encryption to protect the confidentiality of SSH remote connections.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-234816	SLES-15-010160	SV-234816r622137_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, non-organization-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. By specifying a cipher list with the order of ciphers being in a "strongest to weakest" orientation, the system will automatically attempt to use the strongest cipher for securing SSH connections. Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173

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, non-organization-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. By specifying a cipher list with the order of ciphers being in a "strongest to weakest" orientation, the system will automatically attempt to use the strongest cipher for securing SSH connections. Satisfies: SRG-OS-000033-GPOS-00014, SRG-OS-000125-GPOS-00065, SRG-OS-000250-GPOS-00093, SRG-OS-000393-GPOS-00173

STIG	Date
SUSE Linux Enterprise Server 15 Security Technical Implementation Guide	2021-03-04

Details

Check Text ( C-38004r618717_chk )
Verify that the SUSE operating system implements DoD-approved encryption to protect the confidentiality of SSH remote connections. Check the SSH daemon configuration for allowed ciphers with the following command: > sudo grep -i ciphers /etc/ssh/sshd_config \| grep -v '^#' Ciphers aes256-ctr,aes192-ctr,aes128-ctr If any ciphers other than "aes256-ctr", "aes192-ctr", or "aes128-ctr" are listed, the order differs from the example above, or the "Ciphers" keyword is missing, this is a finding.

Check Text ( C-38004r618717_chk )

Verify that the SUSE operating system implements DoD-approved encryption to protect the confidentiality of SSH remote connections.

Check the SSH daemon configuration for allowed ciphers with the following command:

> sudo grep -i ciphers /etc/ssh/sshd_config | grep -v '^#'

Ciphers aes256-ctr,aes192-ctr,aes128-ctr

If any ciphers other than "aes256-ctr", "aes192-ctr", or "aes128-ctr" are listed, the order differs from the example above, or the "Ciphers" keyword is missing, this is a finding.

Fix Text (F-37967r618718_fix)
Edit the SSH daemon configuration (/etc/ssh/sshd_config) and remove any ciphers not starting with "aes" and remove any ciphers ending with "cbc". If necessary, add a "Ciphers" line: Ciphers aes256-ctr,aes192-ctr,aes128-ctr Restart the SSH daemon: > sudo systemctl restart sshd.service