RHEL 9 SSH daemon must not allow Kerberos authentication.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-258004	RHEL-09-255140	SV-258004r958796_rule		Medium

Description
Kerberos authentication for SSH is often implemented using Generic Security Service Application Program Interface (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 implementations may be subject to exploitation. Satisfies: SRG-OS-000364-GPOS-00151, SRG-OS-000480-GPOS-00227

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

Details

Check Text ( C-61745r952203_chk )
Verify the SSH daemon does not allow Kerberos authentication 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*kerberosauthentication' KerberosAuthentication no If the value is returned as "yes", the returned line is commented out, no output is returned, and the use of Kerberos authentication has not been documented with the information system security officer (ISSO), this is a finding.

Check Text ( C-61745r952203_chk )

Verify the SSH daemon does not allow Kerberos authentication 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*kerberosauthentication'

KerberosAuthentication no

If the value is returned as "yes", the returned line is commented out, no output is returned, and the use of Kerberos authentication has not been documented with the information system security officer (ISSO), this is a finding.

Fix Text (F-61669r925998_fix)
Configure the SSH daemon to not allow Kerberos authentication. Add the following line in "/etc/ssh/sshd_config", or uncomment the line and set the value to "no": KerberosAuthentication no The SSH service must be restarted for changes to take effect: $ sudo systemctl restart sshd.service