class Net::SSH::Transport::Session

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.

Constants

DEFAULT_PORT: 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={}) click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 59
def initialize(host, options={})
  self.logger = options[:logger]

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

  @socket =
    if (factory = options[:proxy])
      debug { "establishing connection to #{@host}:#{@port} through proxy" }
      factory.open(@host, @port, options)
    else
      debug { "establishing connection to #{@host}:#{@port}" }
      Socket.tcp(@host, @port, @bind_address, nil,
                 connect_timeout: options[:timeout])
    end

  @socket.extend(PacketStream)
  @socket.logger = @logger

  debug { "connection established" }

  @queue = []

  @host_key_verifier = select_host_key_verifier(options[:verify_host_key])

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

  @algorithms = Algorithms.new(self, options)
  @algorithms.start
  wait { algorithms.initialized? }
rescue Errno::ETIMEDOUT
  raise Net::SSH::ConnectionTimeout
end

Public Instance Methods

close() click to toggle source

Cleans up (see Net::SSH::Transport::PacketStream#cleanup) and closes the underlying socket.

# File lib/net/ssh/transport/session.rb, line 128
def close
  socket.cleanup
  socket.close
end

closed?() click to toggle source

Returns true if the underlying socket has been closed.

# File lib/net/ssh/transport/session.rb, line 123
def closed?
  socket.closed?
end

configure_client(options={}) click to toggle source

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.

# File lib/net/ssh/transport/session.rb, line 253
def configure_client(options={})
  socket.client.set(options)
end

configure_server(options={}) click to toggle source

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.

# File lib/net/ssh/transport/session.rb, line 260
def configure_server(options={})
  socket.server.set(options)
end

enqueue_message(message) click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 246
def enqueue_message(message)
  socket.enqueue_packet(message)
end

hint(which, value=true) click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 266
def hint(which, value=true)
  socket.hints[which] = value
end

host_as_string() click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 104
def host_as_string
  @host_as_string ||= begin
    string = "#{host}"
    string = "[#{string}]:#{port}" if port != DEFAULT_PORT

    peer_ip = socket.peer_ip

    if peer_ip != Net::SSH::Transport::PacketStream::PROXY_COMMAND_HOST_IP &&
       peer_ip != host
      string2 = peer_ip
      string2 = "[#{string2}]:#{port}" if port != DEFAULT_PORT
      string << "," << string2
    end

    string
  end
end

host_keys() click to toggle source

# File lib/net/ssh/transport/session.rb, line 95
def host_keys
  @host_keys ||= begin
    known_hosts = options.fetch(:known_hosts, KnownHosts)
    known_hosts.search_for(options[:host_key_alias] || host_as_string, options)
  end
end

next_message() click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 174
def next_message
  poll_message(:block)
end

peer() click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 168
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) click to toggle source

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.

# File lib/net/ssh/transport/session.rb, line 189
def poll_message(mode=:nonblock, consume_queue=true)
  loop do
    return @queue.shift if consume_queue && @queue.any? && algorithms.allow?(@queue.first)

    packet = socket.next_packet(mode, options[:timeout])
    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 received: #{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) click to toggle source

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.

# File lib/net/ssh/transport/session.rb, line 234
def push(packet)
  @queue.push(packet)
end

rekey!() click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 151
def rekey!
  if !algorithms.pending?
    algorithms.rekey!
    wait { algorithms.initialized? }
  end
end

rekey_as_needed() click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 161
def rekey_as_needed
  return if algorithms.pending?
  socket.if_needs_rekey? { rekey! }
end

send_message(message) click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 240
def send_message(message)
  socket.send_packet(message)
end

service_request(service) click to toggle source

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

# File lib/net/ssh/transport/session.rb, line 144
def service_request(service)
  Net::SSH::Buffer.from(:byte, SERVICE_REQUEST, :string, service)
end

shutdown!() click to toggle source

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).

# File lib/net/ssh/transport/session.rb, line 137
def shutdown!
  error { "forcing connection closed" }
  socket.close
end

wait() { || ... } click to toggle source

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).

# File lib/net/ssh/transport/session.rb, line 222
def wait
  loop do
    break if block_given? && yield
    message = poll_message(:nonblock, false)
    push(message) if message
    break if !block_given?
  end
end