Class: Capistrano::SSH

Inherits:
Object
  • Object
show all
Defined in:
lib/capistrano/ssh.rb

Overview

A helper class for dealing with SSH connections.

Defined Under Namespace

Modules: Server

Class Method Summary collapse

Class Method Details

.connect(server, options = {}) ⇒ Object

An abstraction to make it possible to connect to the server via public key without prompting for the password. If the public key authentication fails this will fall back to password authentication.

server must be an instance of ServerDefinition.

If a block is given, the new session is yielded to it, otherwise the new session is returned.

If an :ssh_options key exists in options, it is passed to the Net::SSH constructor. Values in options are then merged into it, and any connection information in server is added last, so that server info takes precedence over options, which takes precendence over ssh_options.


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# File 'lib/capistrano/ssh.rb', line 39

def self.connect(server, options={})
  connection_strategy(server, options) do |host, user, connection_options|
    connection = Net::SSH.start(host, user, connection_options)
    Server.apply_to(connection, server)
  end
end

.connection_strategy(server, options = {}, &block) ⇒ Object

Abstracts the logic for establishing an SSH connection (which includes testing for connection failures and retrying with a password, and so forth, mostly made complicated because of the fact that some of these variables might be lazily evaluated and try to do something like prompt the user, which should only happen when absolutely necessary.

This will yield the hostname, username, and a hash of connection options to the given block, which should return a new connection.


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# File 'lib/capistrano/ssh.rb', line 54

def self.connection_strategy(server, options={}, &block)
  methods = [ %w(publickey hostbased), %w(password keyboard-interactive) ]
  password_value = nil

  # construct the hash of ssh options that should be passed more-or-less
  # directly to Net::SSH. This will be the general ssh options, merged with
  # the server-specific ssh-options.
  ssh_options = (options[:ssh_options] || {}).merge(server.options[:ssh_options] || {})

  # load any SSH configuration files that were specified in the SSH options. This
  # will load from ~/.ssh/config and /etc/ssh_config by default (see Net::SSH
  # for details). Merge the explicitly given ssh_options over the top of the info
  # from the config file.
  ssh_options = Net::SSH.configuration_for(server.host, ssh_options.fetch(:config, true)).merge(ssh_options)

  # Once we've loaded the config, we don't need Net::SSH to do it again.
  ssh_options[:config] = false

  user = server.user || options[:user] || ssh_options[:username] ||
         ssh_options[:user] || ServerDefinition.default_user
  port = server.port || options[:port] || ssh_options[:port]

  # the .ssh/config file might have changed the host-name on us
  host = ssh_options.fetch(:host_name, server.host) 

  ssh_options[:port] = port if port

  # delete these, since we've determined which username to use by this point
  ssh_options.delete(:username)
  ssh_options.delete(:user)

  begin
    connection_options = ssh_options.merge(
      :password => password_value,
      :auth_methods => ssh_options[:auth_methods] || methods.shift
    )

    yield host, user, connection_options
  rescue Net::SSH::AuthenticationFailed
    raise if methods.empty? || ssh_options[:auth_methods]
    password_value = options[:password]
    retry
  end
end