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1.6.10 Ensure access to sshd warning banner is configured

Information

The sshd warning banner must be sent to the remote user before authentication is permitted.

If the sshd warning banner file does not have correct access permissions, it could be modified by unauthorized users to present incorrect or misleading content. An attacker who can write to the banner file could remove legal warning language required for compliance, or inject content designed to mislead users. The file should be owned by root:root and not writable by group or others.

Solution

Run the following commands to set the correct owner and permissions on the configured banner file. Replace </path/to/sshd_banner> with the actual path returned by sshd -T | grep banner :

# chown root:root </path/to/sshd_banner>
# chmod u-x,go-wx </path/to/sshd_banner>

Example using the default banner path:

# chown root:root /etc/issue.net
# chmod 644 /etc/issue.net

Impact:

No operational impact. Tightening permissions on the banner file to root:root 644 does not affect SSH connectivity or authentication.

See Also

https://workbench.cisecurity.org/benchmarks/26893

Item Details

Category: ACCESS CONTROL, CONFIGURATION MANAGEMENT, MEDIA PROTECTION

References: 800-53|AC-3, 800-53|AC-5, 800-53|AC-6, 800-53|CM-6, 800-53|MP-2, CSCv7|14.6

Plugin: Unix

Control ID: 50e670a83c5d7c9a303c4c586dda1c038e5317becd1f958758eb63c5ab1ecb24