The SSH daemon must not permit Kerberos authentication unless needed.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-22475	GEN005526	SV-37872r2_rule	ECSC-1	Low

Description
Kerberos authentication for SSH is often implemented using GSSAPI. If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementation may then be subject to exploitation. To reduce the attack surface of the system, the Kerberos authentication mechanism within SSH must be disabled for systems not using this capability.

Description

Kerberos authentication for SSH is often implemented using GSSAPI. If Kerberos is enabled through SSH, the SSH daemon provides a means of access to the system's Kerberos implementation. Vulnerabilities in the system's Kerberos implementation may then be subject to exploitation. To reduce the attack surface of the system, the Kerberos authentication mechanism within SSH must be disabled for systems not using this capability.

STIG	Date
Red Hat Enterprise Linux 5 Security Technical Implementation Guide	2015-03-12

Details

Check Text ( C-37088r1_chk )
Ask the SA if Kerberos authentication is used by the system. If it is, this is not applicable. Check the SSH daemon configuration for the KerberosAuthentication setting. # grep -i KerberosAuthentication /etc/ssh/sshd_config \| grep -v '^#' If no lines are returned, or the setting is set to "yes", this is a finding.

Fix Text (F-32363r2_fix)
Edit the SSH daemon configuration and set (add if necessary) the "KerberosAuthentication" directive set to "no". Restart the SSH daemon. # /sbin/service sshd restart