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Capistrano::SSH

A helper class for dealing with SSH connections.

Public Class Methods

connect(server, options={}) click to toggle source

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.

    # File lib/capistrano/ssh.rb, line 33
33:     def self.connect(server, options={})
34:       connection_strategy(server, options) do |host, user, connection_options|
35:         connection = Net::SSH.start(host, user, connection_options)
36:         Server.apply_to(connection, server)
37:       end
38:     end
connection_strategy(server, options={}, &block) click to toggle source

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.

    # File lib/capistrano/ssh.rb, line 48
48:     def self.connection_strategy(server, options={}, &block)
49:       methods = [ %(publickey hostbased), %(password keyboard-interactive) ]
50:       password_value = nil
51: 
52:       # construct the hash of ssh options that should be passed more-or-less
53:       # directly to Net::SSH. This will be the general ssh options, merged with
54:       # the server-specific ssh-options.
55:       ssh_options = (options[:ssh_options] || {}).merge(server.options[:ssh_options] || {})
56: 
57:       # load any SSH configuration files that were specified in the SSH options. This
58:       # will load from ~/.ssh/config and /etc/ssh_config by default (see Net::SSH
59:       # for details). Merge the explicitly given ssh_options over the top of the info
60:       # from the config file.
61:       ssh_options = Net::SSH.configuration_for(server.host, ssh_options.fetch(:config, true)).merge(ssh_options)
62: 
63:       # Once we've loaded the config, we don't need Net::SSH to do it again.
64:       ssh_options[:config] = false
65: 
66:       ssh_options[:verbose] = :debug if options[:verbose] && options[:verbose] > 0
67: 
68:       user = server.user || options[:user] || ssh_options[:username] ||
69:              ssh_options[:user] || ServerDefinition.default_user
70:       port = server.port || options[:port] || ssh_options[:port]
71: 
72:       # the .ssh/config file might have changed the host-name on us
73:       host = ssh_options.fetch(:host_name, server.host) 
74: 
75:       ssh_options[:port] = port if port
76: 
77:       # delete these, since we've determined which username to use by this point
78:       ssh_options.delete(:username)
79:       ssh_options.delete(:user)
80: 
81:       begin
82:         connection_options = ssh_options.merge(
83:           :password => password_value,
84:           :auth_methods => ssh_options[:auth_methods] || methods.shift
85:         )
86: 
87:         yield host, user, connection_options
88:       rescue Net::SSH::AuthenticationFailed
89:         raise if methods.empty? || ssh_options[:auth_methods]
90:         password_value = options[:password]
91:         retry
92:       end
93:     end

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