CNF-19031: RAN Hardening (SSHD) - High Severity

[sebrandon1]

Based on reviews of #439

We'll have a single MachineConfig per path, per severity. Future high level severity flags will be added to this file and rebuilt with new comment and source key/values.

Security hardening for SSHD:

• Added 75-sshd_config-high.yaml to disable direct root SSH access, disable password-based authentication (including empty passwords), implement a 5-minute session timeout, and enforce public key authentication for SSH access on worker nodes.

[openshift-ci]

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[openshift-ci-robot]

@sebrandon1: This pull request references CNF-19031 which is a valid jira issue.

Warning: The referenced jira issue has an invalid target version for the target branch this PR targets: expected the epic to target the "4.21.0" version, but no target version was set.

In response to this:

Based on reviews of #439

We'll have a single MachineConfig per path, per severity. Future high level severity flags will be added to this file and rebuilt with new comment and source key/values.

Security hardening for SSHD:

• Added 75-sshd_config-high.yaml to disable direct root SSH access, disable password-based authentication (including empty passwords), implement a 5-minute session timeout, and enforce public key authentication for SSH access on worker nodes.

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