The AIX SSH daemon must be configured to only use FIPS 140-2 approved ciphers.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-91243	AIX7-00-003100	SV-101343r1_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.

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.

STIG	Date
IBM AIX 7.x Security Technical Implementation Guide	2019-04-29

Details

Check Text ( C-90399r1_chk )
Check the SSH daemon configuration for allowed ciphers by running the following command: # grep -i ciphers /etc/ssh/sshd_config \| grep -v '^#' The above command should yield the following output: Ciphers aes128-ctr,aes192-ctr,aes256-ctr If any of the following conditions are true, this is a finding. 1. No line is returned (default ciphers); 2. The returned ciphers list contains any cipher not starting with aes; 3. The returned ciphers list contains any cipher ending with cbc.

Check Text ( C-90399r1_chk )

Check the SSH daemon configuration for allowed ciphers by running the following command:
# grep -i ciphers /etc/ssh/sshd_config | grep -v '^#'

The above command should yield the following output:
Ciphers aes128-ctr,aes192-ctr,aes256-ctr

If any of the following conditions are true, this is a finding.
1. No line is returned (default ciphers);
2. The returned ciphers list contains any cipher not starting with aes;
3. The returned ciphers list contains any cipher ending with cbc.

Fix Text (F-97443r1_fix)
Edit the "/etc/ssh/sshd_config" file and add or edit a "Ciphers" line like this: Ciphers aes128-ctr,aes192-ctr,aes256-ctr Restart the SSH daemon: # stopsrc -s sshd # startsrc -s sshd