The Photon operating system must configure sshd to restrict AllowTcpForwarding.

While enabling Transmission Control Protocol (TCP) tunnels is a valuable function of sshd, this feature is not appropriate for use on single-purpose appliances.

At the command line, run the following command:

# sshd -T|&grep -i AllowTcpForwarding

Expected result:

allowtcpforwarding no

If the output does not match the expected result, this is a finding.

Navigate to and open:

/etc/ssh/sshd_config

Ensure the "AllowTcpForwarding" line is uncommented and set to the following:

AllowTcpForwarding no

At the command line, run the following command:

# systemctl restart sshd.service