The Red Hat Enterprise Linux operating system must be configured so that the SSH private host key files have mode 0640 or less permissive.

Overview

Finding ID	Version	Rule ID	IA Controls	Severity
V-72257	RHEL-07-040420	SV-86881r3_rule		Medium

Description
If an unauthorized user obtains the private SSH host key file, the host could be impersonated.

STIG	Date
Red Hat Enterprise Linux 7 Security Technical Implementation Guide	2018-11-28

Details

Check Text ( C-72491r4_chk )
Verify the SSH private host key files have mode "0640" or less permissive. The following command will find all SSH private key files on the system and list their modes: # find / -name 'ssh_hostkey' \| xargs ls -lL -rw-r----- 1 root ssh_keys 668 Nov 28 06:43 ssh_host_dsa_key -rw-r----- 1 root ssh_keys 582 Nov 28 06:43 ssh_host_key -rw-r----- 1 root ssh_keys 887 Nov 28 06:43 ssh_host_rsa_key If any file has a mode more permissive than "0640", this is a finding.

Check Text ( C-72491r4_chk )

Verify the SSH private host key files have mode "0640" or less permissive.

The following command will find all SSH private key files on the system and list their modes:

# find / -name '*ssh_host*key' | xargs ls -lL

-rw-r----- 1 root ssh_keys 668 Nov 28 06:43 ssh_host_dsa_key
-rw-r----- 1 root ssh_keys 582 Nov 28 06:43 ssh_host_key
-rw-r----- 1 root ssh_keys 887 Nov 28 06:43 ssh_host_rsa_key

If any file has a mode more permissive than "0640", this is a finding.

Fix Text (F-78611r5_fix)
Configure the mode of SSH private host key files under "/etc/ssh" to "0640" with the following command: # chmod 0640 /path/to/file/ssh_host*key