2015-07-23

Capistrano 3: Change SSH port from default for the first time

dev

We usually change SSH port to different one for some security. Like when provisioning server from official Ubuntu AMI, connecting to a server fails using same ssh_config without specifying port 22 explicitly.

the following quick hack task adds Port line on /etc/ssh/sshd_config then restart sshd. This works on Ubuntu 14.04 trusty. Change ensure_cmd for your system. Note that this adds listening port, not replacing port. More modification on sshd_config will be done via provisioning tool which run after this simple task, so this task only does simple one.

I recommend to make this task runs before deploy task.

task :ensure_ssh_port do
  on roles(:app) do |srv|
    user = srv.ssh_options[:user]
    port = srv.ssh_options[:port] || Net::SSH::Config.for(srv.to_s)[:port]
    unless port
      puts "ensure_ssh_port(#{srv}, #{port}): skip"
      next
    end

    puts "ensure_ssh_port(#{srv}, #{port}): start"

    user_opt = user ? "#{user}@" : ""

    if system(*%W(ssh -T -p #{port} #{user_opt}#{srv} true), err: File::NULL, out: File::NULL)
      puts "ensure_ssh_port(#{srv}, #{port}): ok"
      execute "echo '#{srv} port ensured'"
      next
    end

    unless system(*%W(ssh -T -p 22 #{user_opt}#{srv} true), err: File::NULL, out: File::NULL)
      abort "Couldn't connect #{user_opt}#{srv} with both port 22 and #{port}"
    end

    puts "ensure_ssh_port(#{srv}, #{port}): port 22 ok, changing sshd"

    ensure_cmd = "ssh -T -p 22 #{user_opt}#{srv} \"sudo sh -c 'echo Port #{port} >> /etc/ssh/sshd_config && service ssh restart'\""
    puts "ensure_ssh_port(#{srv}, #{port}): $ #{ensure_cmd}"
    system(ensure_cmd) or raise 'failed to ensure'

    execute "echo '#{srv} port ensured'"
  end
end
Published at 2015-07-23 03:23:04 +0900 | Permalink