Purpose

This example is a controlled SSH lab. It contains OpenSSH configurations, test data, a small analysis script and a run.sh that creates local keys, fingerprints, certificates and evidence.

Local Check

./run.sh

Learning Goals

• trace host-key trust
• distinguish client and server options
• generate test keys safely and locally
• inspect evidence files
• derive review rules

Files

• bin/sshd_hardening_baseline.sh
• client/ssh_config
• server/sshd_config.sample
• data/auth.log.sample
• scenario.json

Review Checklist for SSHD Hardening Baseline

• 01. document host-key trust: Record the affected host, user, key, configuration and risk.
• 02. exclude private keys from the repository: Record the affected host, user, key, configuration and risk.
• 03. check permissions for keys and .ssh: Record the affected host, user, key, configuration and risk.
• 04. justify or disable password login and root login: Record the affected host, user, key, configuration and risk.
• 05. allow agent forwarding only with risk acceptance: Record the affected host, user, key, configuration and risk.
• 06. prefer ProxyJump over copying keys onto bastions: Record the affected host, user, key, configuration and risk.
• 07. limit port forwarding to need and bind address: Record the affected host, user, key, configuration and risk.
• 08. use authorized_keys options for special access: Record the affected host, user, key, configuration and risk.
• 09. keep certificate validity short: Record the affected host, user, key, configuration and risk.
• 10. plan KRL or rotation for revocation: Record the affected host, user, key, configuration and risk.
• 11. store logs and fingerprints as evidence: Record the affected host, user, key, configuration and risk.
• 12. test changes with a test configuration first: Record the affected host, user, key, configuration and risk.
• 13. document host-key trust: Record the affected host, user, key, configuration and risk.
• 14. exclude private keys from the repository: Record the affected host, user, key, configuration and risk.
• 15. check permissions for keys and .ssh: Record the affected host, user, key, configuration and risk.
• 16. justify or disable password login and root login: Record the affected host, user, key, configuration and risk.
• 17. allow agent forwarding only with risk acceptance: Record the affected host, user, key, configuration and risk.
• 18. prefer ProxyJump over copying keys onto bastions: Record the affected host, user, key, configuration and risk.
• 19. limit port forwarding to need and bind address: Record the affected host, user, key, configuration and risk.
• 20. use authorized_keys options for special access: Record the affected host, user, key, configuration and risk.
• 21. keep certificate validity short: Record the affected host, user, key, configuration and risk.
• 22. plan KRL or rotation for revocation: Record the affected host, user, key, configuration and risk.
• 23. store logs and fingerprints as evidence: Record the affected host, user, key, configuration and risk.
• 24. test changes with a test configuration first: Record the affected host, user, key, configuration and risk.
• 25. document host-key trust: Record the affected host, user, key, configuration and risk.
• 26. exclude private keys from the repository: Record the affected host, user, key, configuration and risk.
• 27. check permissions for keys and .ssh: Record the affected host, user, key, configuration and risk.
• 28. justify or disable password login and root login: Record the affected host, user, key, configuration and risk.
• 29. allow agent forwarding only with risk acceptance: Record the affected host, user, key, configuration and risk.
• 30. prefer ProxyJump over copying keys onto bastions: Record the affected host, user, key, configuration and risk.
• 31. limit port forwarding to need and bind address: Record the affected host, user, key, configuration and risk.
• 32. use authorized_keys options for special access: Record the affected host, user, key, configuration and risk.
• 33. keep certificate validity short: Record the affected host, user, key, configuration and risk.
• 34. plan KRL or rotation for revocation: Record the affected host, user, key, configuration and risk.
• 35. store logs and fingerprints as evidence: Record the affected host, user, key, configuration and risk.
• 36. test changes with a test configuration first: Record the affected host, user, key, configuration and risk.
• 37. document host-key trust: Record the affected host, user, key, configuration and risk.
• 38. exclude private keys from the repository: Record the affected host, user, key, configuration and risk.
• 39. check permissions for keys and .ssh: Record the affected host, user, key, configuration and risk.
• 40. justify or disable password login and root login: Record the affected host, user, key, configuration and risk.
• 41. allow agent forwarding only with risk acceptance: Record the affected host, user, key, configuration and risk.
• 42. prefer ProxyJump over copying keys onto bastions: Record the affected host, user, key, configuration and risk.
• 43. limit port forwarding to need and bind address: Record the affected host, user, key, configuration and risk.
• 44. use authorized_keys options for special access: Record the affected host, user, key, configuration and risk.

Practice Appendix: SSHD Hardening Baseline

This appendix is a working backlog for longer trainings, reviews and repetitions. Each task can be checked locally with OpenSSH client tools, test keys and sample configurations.

A001. sshd_config-Härtung und Review

• Task: verify fingerprint and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A002. OpenSSH

• Task: evaluate configuration and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A003. Trust

• Task: justify risk and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A004. Security

• Task: explain error path and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A005. sshd_config-Härtung und Review

• Task: classify log line and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A006. OpenSSH

• Task: document trust model and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A007. Trust

• Task: plan rotation and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A008. Security

• Task: restrict access and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A009. sshd_config-Härtung und Review

• Task: review forwarding and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A010. OpenSSH

• Task: describe recovery path and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A011. Trust

• Task: verify fingerprint and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A012. Security

• Task: evaluate configuration and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A013. sshd_config-Härtung und Review

• Task: justify risk and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A014. OpenSSH

• Task: explain error path and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A015. Trust

• Task: classify log line and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A016. Security

• Task: document trust model and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A017. sshd_config-Härtung und Review

• Task: plan rotation and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A018. OpenSSH

• Task: restrict access and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A019. Trust

• Task: review forwarding and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A020. Security

• Task: describe recovery path and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A021. sshd_config-Härtung und Review

• Task: verify fingerprint and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A022. OpenSSH

• Task: evaluate configuration and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A023. Trust

• Task: justify risk and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A024. Security

• Task: explain error path and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A025. sshd_config-Härtung und Review

• Task: classify log line and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A026. OpenSSH

• Task: document trust model and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A027. Trust

• Task: plan rotation and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A028. Security

• Task: restrict access and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A029. sshd_config-Härtung und Review

• Task: review forwarding and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A030. OpenSSH

• Task: describe recovery path and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A031. Trust

• Task: verify fingerprint and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A032. Security

• Task: evaluate configuration and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A033. sshd_config-Härtung und Review

• Task: justify risk and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A034. OpenSSH

• Task: explain error path and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A035. Trust

• Task: classify log line and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A036. Security

• Task: document trust model and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A037. sshd_config-Härtung und Review

• Task: plan rotation and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A038. OpenSSH

• Task: restrict access and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A039. Trust

• Task: review forwarding and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A040. Security

• Task: describe recovery path and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A041. sshd_config-Härtung und Review

• Task: verify fingerprint and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A042. OpenSSH

• Task: evaluate configuration and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A043. Trust

• Task: justify risk and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A044. Security

• Task: explain error path and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A045. sshd_config-Härtung und Review

• Task: classify log line and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A046. OpenSSH

• Task: document trust model and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A047. Trust

• Task: plan rotation and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A048. Security

• Task: restrict access and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A049. sshd_config-Härtung und Review

• Task: review forwarding and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A050. OpenSSH

• Task: describe recovery path and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A051. Trust

• Task: verify fingerprint and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A052. Security

• Task: evaluate configuration and connect the observation explicitly to Security.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A053. sshd_config-Härtung und Review

• Task: justify risk and connect the observation explicitly to sshd_config-Härtung und Review.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A054. OpenSSH

• Task: explain error path and connect the observation explicitly to OpenSSH.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.

A055. Trust

• Task: classify log line and connect the observation explicitly to Trust.
• Evidence: Record command, expected output, actual output, fingerprint or configuration line.
• Operations question: What happens on host-key change, wrong user, missing key or non-interactive CI execution?
• Security question: Can a private key, agent socket, tunnel, password login or bastion path be abused?
• Recovery: Describe revocation, rotation, known-hosts repair, key removal, CA change or log analysis.