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ENDEFRES

sshconfig-lint / classroom

SSH config classroom worksheet

A printable 20-minute exercise for learning how OpenSSH chooses settings and how to spot unsafe configuration.

Find and explain five mistakes

  1. Determine which User applies to school-server.
  2. Find the setting that disables host-key protection.
  3. Explain why the ControlPath can collide.
  4. Identify the obsolete cipher.
  5. Consolidate the duplicate Host block.
~/.ssh/config
Host *
  StrictHostKeyChecking no
  User deploy
  ControlMaster auto
  ControlPath ~/.ssh/control-%h

Host school-server
  HostName 203.0.113.42
  User student
  Ciphers aes256-gcm@openssh.com,3des-cbc

Host school-server
  IdentityFile ~/.ssh/id_ed25519
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