Net::SSH is a library for interacting, programmatically, with remote processes via the SSH2 protocol. Sessions are always initiated via ::start. From there, a program interacts with the new SSH session via the convenience methods on Net::SSH::Connection::Session, by opening and interacting with new channels (Net::SSH::Connection:Session#open_channel and Net::SSH::Connection::Channel), or by forwarding local and/or remote ports through the connection (Net::SSH::Service::Forward).
The SSH protocol is very event-oriented. Requests are sent from the client to the server, and are answered asynchronously. This gives great flexibility (since clients can have multiple requests pending at a time), but it also adds complexity. Net::SSH tries to manage this complexity by providing some simpler methods of synchronous communication (see Net::SSH::Connection::Session#exec!).
In general, though, and if you want to do anything more complicated than simply executing commands and capturing their output, you'll need to use channels (Net::SSH::Connection::Channel) to build state machines that are executed while the event loop runs (Net::SSH::Connection::Session#loop).
Net::SSH::Connection::Session and Net::SSH::Connection::Channel have more information about this technique.
Net::SSH.start("host", "user", password: "password") do |ssh| result = ssh.exec!("ls -l") puts result end
Net::SSH.start("host", "user", password: "password") do |ssh| ssh.forward.local(1234, "www.google.com", 80) ssh.loop { true } end
Net::SSH.start("host", "user", password: "password") do |ssh| ssh.forward.remote(80, "www.google.com", 1234) ssh.loop { true } end
# File lib/net/ssh.rb, line 273 def self.assign_defaults(options) if !options[:logger] options[:logger] = Logger.new(STDERR) options[:logger].level = Logger::FATAL end options[:password_prompt] ||= Prompt.default(options) [:password, :passphrase].each do |key| options.delete(key) if options.key?(key) && options[key].nil? end end
Returns a hash of the configuration options for the given host, as read
from the SSH configuration file(s). If
use_ssh_config
is true (the default), this will load
configuration from both ~/.ssh/config and /etc/ssh_config. If
use_ssh_config
is nil or false, nothing will be loaded (and an
empty hash returned). Otherwise, use_ssh_config
may be a file
name (or array of file names) of SSH configuration
file(s) to read.
See Net::SSH::Config for the full description of all supported options.
# File lib/net/ssh.rb, line 263 def self.configuration_for(host, use_ssh_config) files = case use_ssh_config when true then Net::SSH::Config.expandable_default_files when false, nil then return {} else Array(use_ssh_config) end Net::SSH::Config.for(host, files) end
The standard means of starting a new SSH connection. When used with a block, the connection will be closed when the block terminates, otherwise the connection will just be returned. The yielded (or returned) value will be an instance of Net::SSH::Connection::Session (q.v.). (See also Net::SSH::Connection::Channel and Net::SSH::Service::Forward.)
Net::SSH.start("host", "user") do |ssh| ssh.exec! "cp /some/file /another/location" hostname = ssh.exec!("hostname") ssh.open_channel do |ch| ch.exec "sudo -p 'sudo password: ' ls" do |ch, success| abort "could not execute sudo ls" unless success ch.on_data do |ch, data| print data if data =~ /sudo password: / ch.send_data("password\n") end end end end ssh.loop end
This method accepts the following options (all are optional):
:auth_methods => an array of authentication methods to try
:bind_address => the IP address on the connecting machine to use in establishing connection. (:bind_address is discarded if :proxy is set.)
:compression => the compression algorithm to use, or true
to use whatever is supported.
:compression_level => the compression level to use when sending data
:config => set to true
to load the default OpenSSH config
files (~/.ssh/config, /etc/ssh_config), or to false
to not
load them, or to a file-name (or array of file-names) to load those
specific configuration files. Defaults to true
.
:encryption => the encryption cipher (or ciphers) to use
:forward_agent => set to true if you want the SSH agent connection to be forwarded
:known_hosts => a custom object holding known hosts records. It must implement search_for and add in a similiar manner as KnownHosts.
:global_known_hosts_file => the location of the global known hosts file. Set to an array if you want to specify multiple global known hosts files. Defaults to %w(/etc/ssh/ssh_known_hosts /etc/ssh/ssh_known_hosts2).
:hmac => the hmac algorithm (or algorithms) to use
:host_key => the host key algorithm (or algorithms) to use
:host_key_alias => the host name to use when looking up or adding a host to a known_hosts dictionary file
:host_name => the real host name or IP to log into. This is used instead
of the host
parameter, and is primarily only useful when
specified in an SSH configuration file. It lets you
specify an “alias”, similarly to adding an entry in /etc/hosts but without
needing to modify /etc/hosts.
:keepalive => set to true
to send a keepalive packet to the
SSH server when there's no traffic between the
SSH server and Net::SSH
client for the keepalive_interval seconds. Defaults to false
.
:keepalive_interval => the interval seconds for keepalive. Defaults to
300
seconds.
:keepalive_maxcount => the maximun number of keepalive packet miss allowed. Defaults to 3
:kex => the key exchange algorithm (or algorithms) to use
:keys => an array of file names of private keys to use for publickey and hostbased authentication
:key_data => an array of strings, with each element of the array being a raw private key in PEM format.
:keys_only => set to true
to use only private keys from
keys
and key_data
parameters, even if ssh-agent
offers more identities. This option is intended for situations where
ssh-agent offers many different identites.
:logger => the logger instance to use when logging
:max_pkt_size => maximum size we tell the other side that is supported per packet. Default is 0x8000 (32768 bytes). Increase to 0x10000 (65536 bytes) for better performance if your SSH server supports it (most do).
:max_win_size => maximum size we tell the other side that is supported for the window.
:non_interactive => set to true if your app is non interactive and prefers authentication failure vs password prompt. Non-interactive applications should set it to true to prefer failing a password/etc auth methods vs. asking for password.
:paranoid => either false, true, :very, or :secure specifying how strict
host-key verification should be (in increasing order here). You can also
provide an own Object which responds to verify
. The argument
given to verify
is a hash consisting of the :key
,
the :key_blob
, the :fingerprint
and the
:session
. Returning true accepts the host key, returning false
declines it and closes the connection.
:passphrase => the passphrase to use when loading a private key (default
is nil
, for no passphrase)
:password => the password to use to login
:port => the port to use when connecting to the remote host
:properties => a hash of key/value pairs to add to the new connection's properties (see Net::SSH::Connection::Session#properties)
:proxy => a proxy instance (see Proxy) to use when connecting
:rekey_blocks_limit => the max number of blocks to process before rekeying
:rekey_limit => the max number of bytes to process before rekeying
:rekey_packet_limit => the max number of packets to process before rekeying
:send_env => an array of local environment variable names to export to the remote environment. Names may be given as String or Regexp.
:timeout => how long to wait for the initial connection to be made
:user => the user name to log in as; this overrides the
user
parameter, and is primarily only useful when provided via
an SSH configuration file.
:remote_user => used for substitution into the '%r' part of a ProxyCommand
:user_known_hosts_file => the location of the user known hosts file. Set to an array to specify multiple user known hosts files. Defaults to %w(~/.ssh/known_hosts ~/.ssh/known_hosts2).
:use_agent => Set false to disable the use of ssh-agent. Defaults to true
:verbose => how verbose to be (Logger verbosity constants, Logger::DEBUG is very verbose, Logger::FATAL is all but silent). Logger::FATAL is the default. The symbols :debug, :info, :warn, :error, and :fatal are also supported and are translated to the corresponding Logger constant.
:append_all_supported_algorithms => set to true
to append
all supported algorithms by net-ssh. Was the default behaviour until 2.10
:number_of_password_prompts => Number of prompts for the password authentication method defaults to 3 set to 0 to disable prompt for password auth method
:password_prompt => a custom prompt object with ask method. See Net::SSH::Prompt
:agent_socket_factory => enables the user to pass a lambda/block that will serve as the socket factory
Net::SSH::start(user,host,agent_socket_factory: ->{ UNIXSocket.open('/foo/bar') }) example: ->{ UNIXSocket.open('/foo/bar')}
If user
parameter is nil it defaults to USER from ssh_config,
or local username
# File lib/net/ssh.rb, line 204 def self.start(host, user=nil, options={}, &block) invalid_options = options.keys - VALID_OPTIONS if invalid_options.any? raise ArgumentError, "invalid option(s): #{invalid_options.join(', ')}" end assign_defaults(options) _sanitize_options(options) options[:user] = user if user options = configuration_for(host, options.fetch(:config, true)).merge(options) host = options.fetch(:host_name, host) if options[:non_interactive] options[:number_of_password_prompts] = 0 end if options[:verbose] options[:logger].level = case options[:verbose] when Integer then options[:verbose] when :debug then Logger::DEBUG when :info then Logger::INFO when :warn then Logger::WARN when :error then Logger::ERROR when :fatal then Logger::FATAL else raise ArgumentError, "can't convert #{options[:verbose].inspect} to any of the Logger level constants" end end transport = Transport::Session.new(host, options) auth = Authentication::Session.new(transport, options) user = options.fetch(:user, user) || Etc.getlogin if auth.authenticate("ssh-connection", user, options[:password]) connection = Connection::Session.new(transport, options) if block_given? begin yield connection ensure connection.close unless connection.closed? end else return connection end else transport.close raise AuthenticationFailed, "Authentication failed for user #{user}@#{host}" end end
# File lib/net/ssh.rb, line 286 def self._sanitize_options(options) invalid_option_values = [nil,[nil]] unless (options.values & invalid_option_values).empty? nil_options = options.select { |_k,v| invalid_option_values.include?(v) }.map(&:first) Kernel.warn "#{caller_locations(2, 1)[0]}: Passing nil, or [nil] to Net::SSH.start is deprecated for keys: #{nil_options.join(', ')}" end end