Class: Net::SSH::Transport::Session

Inherits:
Object
  • Object
show all
Includes:
Loggable, Constants
Defined in:
lib/net/ssh/transport/session.rb

Overview

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.

Defined Under Namespace

Classes: CompatibleVerifier

Constant Summary collapse

DEFAULT_PORT =

The standard port for the SSH protocol.

22

Constants included from Constants

Constants::DEBUG, Constants::DISCONNECT, Constants::IGNORE, Constants::KEXDH_GEX_GROUP, Constants::KEXDH_GEX_INIT, Constants::KEXDH_GEX_REPLY, Constants::KEXDH_GEX_REQUEST, Constants::KEXDH_INIT, Constants::KEXDH_REPLY, Constants::KEXECDH_INIT, Constants::KEXECDH_REPLY, Constants::KEXINIT, Constants::NEWKEYS, Constants::SERVICE_ACCEPT, Constants::SERVICE_REQUEST, Constants::UNIMPLEMENTED

Instance Attribute Summary collapse

Attributes included from Loggable

#logger

Instance Method Summary collapse

Methods included from Loggable

#debug, #error, #fatal, #info, #lwarn

Constructor Details

#initialize(host, options = {}) ⇒ Session

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


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# File 'lib/net/ssh/transport/session.rb', line 58

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

Instance Attribute Details

#algorithmsObject (readonly)

The Algorithms instance used to perform key exchanges.


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# File 'lib/net/ssh/transport/session.rb', line 46

def algorithms
  @algorithms
end

#hostObject (readonly)

The host to connect to, as given to the constructor.


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# File 'lib/net/ssh/transport/session.rb', line 31

def host
  @host
end

#host_key_verifierObject (readonly)

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


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# File 'lib/net/ssh/transport/session.rb', line 50

def host_key_verifier
  @host_key_verifier
end

#optionsObject (readonly)

The hash of options that were given to the object at initialization.


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# File 'lib/net/ssh/transport/session.rb', line 53

def options
  @options
end

#portObject (readonly)

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.


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# File 'lib/net/ssh/transport/session.rb', line 35

def port
  @port
end

#queueObject (readonly)

this method is primarily for use in tests


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# File 'lib/net/ssh/transport/session.rb', line 275

def queue
  @queue
end

#server_versionObject (readonly)

The ServerVersion instance that encapsulates the negotiated protocol version.


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# File 'lib/net/ssh/transport/session.rb', line 43

def server_version
  @server_version
end

#socketObject (readonly)

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


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# File 'lib/net/ssh/transport/session.rb', line 39

def socket
  @socket
end

Instance Method Details

#closeObject

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


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# File 'lib/net/ssh/transport/session.rb', line 127

def close
  socket.cleanup
  socket.close
end

#closed?Boolean

Returns true if the underlying socket has been closed.

Returns:

  • (Boolean)

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# File 'lib/net/ssh/transport/session.rb', line 122

def closed?
  socket.closed?
end

#configure_client(options = {}) ⇒ Object

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.


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# File 'lib/net/ssh/transport/session.rb', line 255

def configure_client(options = {})
  socket.client.set(options)
end

#configure_server(options = {}) ⇒ Object

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.


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# File 'lib/net/ssh/transport/session.rb', line 262

def configure_server(options = {})
  socket.server.set(options)
end

#enqueue_message(message) ⇒ Object

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


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# File 'lib/net/ssh/transport/session.rb', line 248

def enqueue_message(message)
  socket.enqueue_packet(message)
end

#hint(which, value = true) ⇒ Object

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


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# File 'lib/net/ssh/transport/session.rb', line 268

def hint(which, value = true)
  socket.hints[which] = value
end

#host_as_stringObject

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


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# File 'lib/net/ssh/transport/session.rb', line 103

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_keysObject


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# File 'lib/net/ssh/transport/session.rb', line 94

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_messageObject

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


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# File 'lib/net/ssh/transport/session.rb', line 174

def next_message
  poll_message(:block)
end

#peerObject

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


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# 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) ⇒ Object

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.


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# 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) ⇒ Object

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.


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# File 'lib/net/ssh/transport/session.rb', line 236

def push(packet)
  @queue.push(packet)
end

#rekey!Object

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


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# File 'lib/net/ssh/transport/session.rb', line 150

def rekey!
  if !algorithms.pending?
    algorithms.rekey!
    wait { algorithms.initialized? }
  end
end

#rekey_as_neededObject

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.


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# File 'lib/net/ssh/transport/session.rb', line 160

def rekey_as_needed
  return if algorithms.pending?

  socket.if_needs_rekey? { rekey! }
end

#send_message(message) ⇒ Object

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


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# File 'lib/net/ssh/transport/session.rb', line 242

def send_message(message)
  socket.send_packet(message)
end

#service_request(service) ⇒ Object

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


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# File 'lib/net/ssh/transport/session.rb', line 143

def service_request(service)
  Net::SSH::Buffer.from(:byte, SERVICE_REQUEST, :string, service)
end

#shutdown!Object

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).


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# File 'lib/net/ssh/transport/session.rb', line 136

def shutdown!
  error { "forcing connection closed" }
  socket.close
end

#waitObject

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).


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# File 'lib/net/ssh/transport/session.rb', line 223

def wait
  loop do
    break if block_given? && yield

    message = poll_message(:nonblock, false)
    push(message) if message
    break if !block_given?
  end
end