Class: ESSH::Transport::Session

Inherits:
Object
  • Object
show all
Includes:
Net::SSH::Loggable, Net::SSH::Transport::Constants
Defined in:
lib/evented-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: ServerVersion

Constant Summary collapse

DEFAULT_PORT =

The standard port for the SSH protocol.

22

Instance Attribute Summary collapse

Instance Method Summary collapse

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/evented-ssh/transport/session.rb', line 63

def initialize(host, **options)
    self.logger = options[:logger]

    @reactor = ::Libuv.reactor

    @host = host
    @port = options[:port] || DEFAULT_PORT
    @bind_address = options[:bind_address] || '0.0.0.0'
    @options = options

    debug { "establishing connection to #{@host}:#{@port}" }

    actual_host = if IPAddress.valid?(@host)
        @host
    else
        @reactor.lookup(@host)[0][0]
    end

    @socket = PacketStream.new(self, **options)
    @socket.connect(actual_host, @port)

    debug { "connection established" }

    @host_key_verifier = select_host_key_verifier(options[:paranoid])
    @algorithms = Algorithms.new(self, options)
    @server_version = ServerVersion.new
    @socket.algorithms = @algorithms

    socket.direct_write "#{::Net::SSH::Transport::ServerVersion::PROTO_VERSION}\r\n"
    socket.start_read

    @algorithms.ready # Wait for this to complete
end

Instance Attribute Details

#algorithms ⇒ Object (readonly)

The Algorithms instance used to perform key exchanges.



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# File 'lib/evented-ssh/transport/session.rb', line 48

def algorithms
  @algorithms
end

#host ⇒ Object (readonly)

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



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# File 'lib/evented-ssh/transport/session.rb', line 33

def host
  @host
end

#host_key_verifier ⇒ Object (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/evented-ssh/transport/session.rb', line 52

def host_key_verifier
  @host_key_verifier
end

#options ⇒ Object (readonly)

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



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# File 'lib/evented-ssh/transport/session.rb', line 55

def options
  @options
end

#port ⇒ Object (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/evented-ssh/transport/session.rb', line 37

def port
  @port
end

#reactor ⇒ Object (readonly)

The event loop that this SSH session is running on



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

def reactor
  @reactor
end

#server_version ⇒ Object (readonly)

The ServerVersion instance that encapsulates the negotiated protocol version.



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# File 'lib/evented-ssh/transport/session.rb', line 45

def server_version
  @server_version
end

#socket ⇒ Object (readonly)

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



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# File 'lib/evented-ssh/transport/session.rb', line 41

def socket
  @socket
end

Instance Method Details

#close ⇒ Object

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



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# File 'lib/evented-ssh/transport/session.rb', line 129

def close
    info { "closing connection" }
    socket.shutdown
end

#closed? ⇒ Boolean

Returns true if the underlying socket has been closed.

Returns:

  • (Boolean) 


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# File 'lib/evented-ssh/transport/session.rb', line 124

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/evented-ssh/transport/session.rb', line 206

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/evented-ssh/transport/session.rb', line 213

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/evented-ssh/transport/session.rb', line 199

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/evented-ssh/transport/session.rb', line 219

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

#host_as_string ⇒ Object

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



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# File 'lib/evented-ssh/transport/session.rb', line 106

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 != host
            string2 = peer_ip
            string2 = "[#{string2}]:#{port}" if port != DEFAULT_PORT
            string << "," << string2
        end

        string
    end
end

#host_keys ⇒ Object 



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# File 'lib/evented-ssh/transport/session.rb', line 97

def host_keys
    @host_keys ||= begin
        known_hosts = options.fetch(:known_hosts, ::Net::SSH::KnownHosts)
        known_hosts.search_for(options[:host_key_alias] || host_as_string, options)
    end
end

#next_message ⇒ Object

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



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# File 'lib/evented-ssh/transport/session.rb', line 175

def next_message
    socket.get_packet
end

#peer ⇒ Object

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/evented-ssh/transport/session.rb', line 169

def peer
    @peer ||= { ip: socket.peer_ip, port: @port.to_i, host: @host, canonized: host_as_string }
end

#poll_message ⇒ Object 



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# File 'lib/evented-ssh/transport/session.rb', line 179

def poll_message
    socket.get_packet
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/evented-ssh/transport/session.rb', line 186

def push(packet)
    socket.queue_packet(packet)
    process_waiting
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/evented-ssh/transport/session.rb', line 152

def rekey!
    if !algorithms.pending?
        algorithms.rekey!
        @algorithms.pending?&.promise&.value # Wait for this to complete
    end
end

#rekey_as_needed ⇒ Object

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/evented-ssh/transport/session.rb', line 162

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/evented-ssh/transport/session.rb', line 193

def send_message(message)
    socket.enqueue_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/evented-ssh/transport/session.rb', line 145

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/evented-ssh/transport/session.rb', line 138

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