class Net::SSH::Transport::Session

  1. lib/net/ssh/transport/session.rb
Parent: Transport

The transport layer represents the lowest level of the SSH protocol, and implements basic message exchanging and protocol initialization. It will never be instantiated directly (unless you really know what you're about), but will instead be created for you automatically when you create a new SSH session via Net::SSH.start.

Included modules

  1. Constants
  2. Loggable

Constants

DEFAULT_PORT = 22  

The standard port for the SSH protocol.

Attributes

algorithms [R]

The Algorithms instance used to perform key exchanges.
host [R]

The host to connect to, as given to the constructor.
host_key_verifier [R]

The host-key verifier object used to verify host keys, to ensure that the connection is not being spoofed.
options [R]

The hash of options that were given to the object at initialization.
port [R]

The port number to connect to, as given in the options to the constructor. If no port number was given, this will default to DEFAULT_PORT.
server_version [R]

The ServerVersion instance that encapsulates the negotiated protocol version.
socket [R]

The underlying socket object being used to communicate with the remote host.

Public Class methods

new (host, options={})

Instantiates a new transport layer abstraction. This will block until the initial key exchange completes, leaving you with a ready-to-use transport session.

[show source] 
# File lib/net/ssh/transport/session.rb, line 57
def initialize(host, options={})
  self.logger = options[:logger]

  @host = host
  @port = options[:port] || DEFAULT_PORT
  @bind_address = options[:bind_address] || nil
  @options = options

  debug { "establishing connection to #{@host}:#{@port}" }
  factory = options[:proxy] || TCPSocket
  @socket = timeout(options[:timeout] || 0) {
    case
    when options[:proxy] then factory.open(@host, @port, options)
    when @bind_address.nil? then factory.open(@host, @port)
    else factory.open(@host, @port, @bind_address)
    end
  }
  @socket.extend(PacketStream)
  @socket.logger = @logger

  debug { "connection established" }

  @queue = []

  @host_key_verifier = select_host_key_verifier(options[:paranoid])


  @server_version = timeout(options[:timeout] || 0) { ServerVersion.new(socket, logger) }

  @algorithms = Algorithms.new(self, options)
  wait { algorithms.initialized? }
end

Public Instance methods

close ()

Cleans up (see PacketStream#cleanup) and closes the underlying socket.

[show source] 
# File lib/net/ssh/transport/session.rb, line 111
def close
  socket.cleanup
  socket.close
end
closed? ()

Returns true if the underlying socket has been closed.

[show source] 
# File lib/net/ssh/transport/session.rb, line 106
def closed?
  socket.closed?
end
configure_client (options={})

Configure's the packet stream's client state with the given set of options. This is typically used to define the cipher, compression, and hmac algorithms to use when sending packets to the server.

[show source] 
# File lib/net/ssh/transport/session.rb, line 238
def configure_client(options={})
  socket.client.set(options)
end
configure_server (options={})

Configure's the packet stream's server state with the given set of options. This is typically used to define the cipher, compression, and hmac algorithms to use when reading packets from the server.

[show source] 
# File lib/net/ssh/transport/session.rb, line 245
def configure_server(options={})
  socket.server.set(options)
end
enqueue_message (message)

Enqueues the given message, such that it will be sent at the earliest opportunity. This does not block, but returns immediately.

[show source] 
# File lib/net/ssh/transport/session.rb, line 231
def enqueue_message(message)
  socket.enqueue_packet(message)
end
hint (which, value=true)

Sets a new hint for the packet stream, which the packet stream may use to change its behavior. (See PacketStream#hints).

[show source] 
# File lib/net/ssh/transport/session.rb, line 251
def hint(which, value=true)
  socket.hints[which] = value
end
host_as_string ()

Returns the host (and possibly IP address) in a format compatible with SSH known-host files.

[show source] 
# File lib/net/ssh/transport/session.rb, line 92
def host_as_string
  @host_as_string ||= begin
    string = "#{host}"
    string = "[#{string}]:#{port}" if port != DEFAULT_PORT
    if socket.peer_ip != host
      string2 = socket.peer_ip
      string2 = "[#{string2}]:#{port}" if port != DEFAULT_PORT
      string << "," << string2
    end
    string
  end
end
next_message ()

Blocks until a new packet is available to be read, and returns that packet. See poll_message.

[show source] 
# File lib/net/ssh/transport/session.rb, line 157
def next_message
  poll_message(:block)
end
peer ()

Returns a hash of information about the peer (remote) side of the socket, including :ip, :port, :host, and :canonized (see host_as_string).

[show source] 
# File lib/net/ssh/transport/session.rb, line 151
def peer
  @peer ||= { :ip => socket.peer_ip, :port => @port.to_i, :host => @host, :canonized => host_as_string }
end
poll_message (mode=:nonblock, consume_queue=true)

Tries to read the next packet from the socket. If mode is :nonblock (the default), this will not block and will return nil if there are no packets waiting to be read. Otherwise, this will block until a packet is available. Note that some packet types (DISCONNECT, IGNORE, UNIMPLEMENTED, DEBUG, and KEXINIT) are handled silently by this method, and will never be returned.

If a key-exchange is in process and a disallowed packet type is received, it will be enqueued and otherwise ignored. When a key-exchange is not in process, and consume_queue is true, packets will be first read from the queue before the socket is queried.

[show source] 
# File lib/net/ssh/transport/session.rb, line 172
def poll_message(mode=:nonblock, consume_queue=true)
  loop do
    if consume_queue && @queue.any? && algorithms.allow?(@queue.first)
      return @queue.shift
    end

    packet = socket.next_packet(mode)
    return nil if packet.nil?

    case packet.type
    when DISCONNECT
      raise Net::SSH::Disconnect, "disconnected: #{packet[:description]} (#{packet[:reason_code]})"

    when IGNORE
      debug { "IGNORE packet recieved: #{packet[:data].inspect}" }

    when UNIMPLEMENTED
      lwarn { "UNIMPLEMENTED: #{packet[:number]}" }

    when DEBUG
      send(packet[:always_display] ? :fatal : :debug) { packet[:message] }

    when KEXINIT
      algorithms.accept_kexinit(packet)

    else
      return packet if algorithms.allow?(packet)
      push(packet)
    end
  end
end
push (packet)

Adds the given packet to the packet queue. If the queue is non-empty, poll_message will return packets from the queue in the order they were received.

[show source] 
# File lib/net/ssh/transport/session.rb, line 219
def push(packet)
  @queue.push(packet)
end
rekey! ()

Requests a rekey operation, and blocks until the operation completes. If a rekey is already pending, this returns immediately, having no effect.

[show source] 
# File lib/net/ssh/transport/session.rb, line 134
def rekey!
  if !algorithms.pending?
    algorithms.rekey!
    wait { algorithms.initialized? }
  end
end
rekey_as_needed ()

Returns immediately if a rekey is already in process. Otherwise, if a rekey is needed (as indicated by the socket, see PacketStream#if_needs_rekey?) one is performed, causing this method to block until it completes.

[show source] 
# File lib/net/ssh/transport/session.rb, line 144
def rekey_as_needed
  return if algorithms.pending?
  socket.if_needs_rekey? { rekey! }
end
send_message (message)

Sends the given message via the packet stream, blocking until the entire message has been sent.

[show source] 
# File lib/net/ssh/transport/session.rb, line 225
def send_message(message)
  socket.send_packet(message)
end
service_request (service)

Returns a new service_request packet for the given service name, ready for sending to the server.

[show source] 
# File lib/net/ssh/transport/session.rb, line 127
def service_request(service)
  Net::SSH::Buffer.from(:byte, SERVICE_REQUEST, :string, service)
end
shutdown! ()

Performs a "hard" shutdown of the connection. In general, this should never be done, but it might be necessary (in a rescue clause, for instance, when the connection needs to close but you don't know the status of the underlying protocol's state).

[show source] 
# File lib/net/ssh/transport/session.rb, line 120
def shutdown!
  error { "forcing connection closed" }
  socket.close
end
wait ()

Waits (blocks) until the given block returns true. If no block is given, this just waits long enough to see if there are any pending packets. Any packets read are enqueued (see push).

[show source] 
# File lib/net/ssh/transport/session.rb, line 207
def wait
  loop do
    break if block_given? && yield
    message = poll_message(:nonblock, false)
    push(message) if message
    break if !block_given?
  end
end