308 lines
10 KiB
Ruby
308 lines
10 KiB
Ruby
# -*- coding: binary -*-
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require 'rex/socket'
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require 'timeout'
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require 'net/ssh/errors'
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require 'net/ssh/loggable'
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require 'net/ssh/version'
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require 'net/ssh/transport/algorithms'
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require 'net/ssh/transport/constants'
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require 'net/ssh/transport/packet_stream'
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require 'net/ssh/transport/server_version'
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require 'net/ssh/verifiers/null'
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require 'net/ssh/verifiers/strict'
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require 'net/ssh/verifiers/lenient'
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module Net; module SSH; module Transport
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# The transport layer represents the lowest level of the SSH protocol, and
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# implements basic message exchanging and protocol initialization. It will
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# never be instantiated directly (unless you really know what you're about),
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# but will instead be created for you automatically when you create a new
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# SSH session via Net::SSH.start.
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class Session
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include Constants, Loggable
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# The standard port for the SSH protocol.
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DEFAULT_PORT = 22
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# The host to connect to, as given to the constructor.
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attr_reader :host
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# The port number to connect to, as given in the options to the constructor.
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# If no port number was given, this will default to DEFAULT_PORT.
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attr_reader :port
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# The underlying socket object being used to communicate with the remote
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# host.
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attr_reader :socket
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# The ServerVersion instance that encapsulates the negotiated protocol
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# version.
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attr_reader :server_version
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# Internal compatibility flags (hacks/tweaks/etc)
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attr_reader :compat_flags
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# The Algorithms instance used to perform key exchanges.
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attr_reader :algorithms
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# The host-key verifier object used to verify host keys, to ensure that
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# the connection is not being spoofed.
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attr_reader :host_key_verifier
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# The hash of options that were given to the object at initialization.
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attr_reader :options
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# Instantiates a new transport layer abstraction. This will block until
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# the initial key exchange completes, leaving you with a ready-to-use
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# transport session.
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def initialize(host, options={})
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self.logger = options[:logger]
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@host = host
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@port = options[:port] || DEFAULT_PORT
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@options = options
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debug { "establishing connection to #{@host}:#{@port}" }
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factory = options[:proxy]
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if (factory)
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@socket = timeout(options[:timeout] || 0) { factory.open(@host, @port) }
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else
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@socket = timeout(options[:timeout] || 0) {
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Rex::Socket::Tcp.create(
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'PeerHost' => @host,
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'PeerPort' => @port,
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'Proxies' => options[:proxies],
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'Context' => {
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'Msf' => options[:msframework],
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'MsfExploit' => options[:msfmodule]
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}
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)
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}
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# Tell MSF to automatically close this socket on error or completion...
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# This prevents resource leaks.
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options[:msfmodule].add_socket(@socket) if options[:msfmodule]
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end
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@socket.extend(PacketStream)
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@socket.logger = @logger
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debug { "connection established" }
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@queue = []
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@host_key_verifier = select_host_key_verifier(options[:paranoid])
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@server_version = ServerVersion.new(socket, logger)
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# Compatibility settings
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ver = @server_version.version
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@compat_flags = 0
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if ver =~ /OpenSSH_2\.[0-3]/ or ver =~ /OpenSSH_2\.5\.[0-2]/
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@compat_flags |= COMPAT_OLD_DHGEX
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end
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@algorithms = Algorithms.new(self, options)
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wait { algorithms.initialized? }
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end
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# Returns the host (and possibly IP address) in a format compatible with
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# SSH known-host files.
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def host_as_string
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@host_as_string ||= begin
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string = "#{host}"
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string = "[#{string}]:#{port}" if port != DEFAULT_PORT
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if socket.peer_ip != host
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string2 = socket.peer_ip
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string2 = "[#{string2}]:#{port}" if port != DEFAULT_PORT
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string << "," << string2
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end
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string
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end
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end
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# Returns true if the underlying socket has been closed.
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def closed?
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socket.closed?
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end
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# Cleans up (see PacketStream#cleanup) and closes the underlying socket.
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def close
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socket.cleanup
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socket.close
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end
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# Performs a "hard" shutdown of the connection. In general, this should
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# never be done, but it might be necessary (in a rescue clause, for instance,
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# when the connection needs to close but you don't know the status of the
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# underlying protocol's state).
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def shutdown!
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error { "forcing connection closed" }
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socket.close
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end
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# Returns a new service_request packet for the given service name, ready
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# for sending to the server.
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def service_request(service)
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Net::SSH::Buffer.from(:byte, SERVICE_REQUEST, :string, service)
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end
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# Requests a rekey operation, and blocks until the operation completes.
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# If a rekey is already pending, this returns immediately, having no
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# effect.
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def rekey!
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if !algorithms.pending?
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algorithms.rekey!
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wait { algorithms.initialized? }
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end
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end
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# Returns immediately if a rekey is already in process. Otherwise, if a
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# rekey is needed (as indicated by the socket, see PacketStream#if_needs_rekey?)
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# one is performed, causing this method to block until it completes.
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def rekey_as_needed
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return if algorithms.pending?
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socket.if_needs_rekey? { rekey! }
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end
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# Returns a hash of information about the peer (remote) side of the socket,
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# including :ip, :port, :host, and :canonized (see #host_as_string).
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def peer
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@peer ||= { :ip => socket.peer_ip, :port => @port.to_i, :host => @host, :canonized => host_as_string }
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end
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# Blocks until a new packet is available to be read, and returns that
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# packet. See #poll_message.
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def next_message
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poll_message(:block)
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end
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# Tries to read the next packet from the socket. If mode is :nonblock (the
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# default), this will not block and will return nil if there are no packets
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# waiting to be read. Otherwise, this will block until a packet is
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# available. Note that some packet types (DISCONNECT, IGNORE, UNIMPLEMENTED,
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# DEBUG, and KEXINIT) are handled silently by this method, and will never
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# be returned.
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#
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# If a key-exchange is in process and a disallowed packet type is
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# received, it will be enqueued and otherwise ignored. When a key-exchange
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# is not in process, and consume_queue is true, packets will be first
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# read from the queue before the socket is queried.
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def poll_message(mode=:nonblock, consume_queue=true)
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loop do
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if consume_queue && @queue.any? && algorithms.allow?(@queue.first)
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return @queue.shift
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end
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packet = socket.next_packet(mode)
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return nil if packet.nil?
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case packet.type
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when DISCONNECT
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raise Net::SSH::Disconnect, "disconnected: #{packet[:description]} (#{packet[:reason_code]})"
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when IGNORE
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debug { "IGNORE packet recieved: #{packet[:data].inspect}" }
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when UNIMPLEMENTED
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lwarn { "UNIMPLEMENTED: #{packet[:number]}" }
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when DEBUG
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send(packet[:always_display] ? :fatal : :debug) { packet[:message] }
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when KEXINIT
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algorithms.accept_kexinit(packet)
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else
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return packet if algorithms.allow?(packet)
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push(packet)
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end
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end
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end
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# Waits (blocks) until the given block returns true. If no block is given,
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# this just waits long enough to see if there are any pending packets. Any
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# packets read are enqueued (see #push).
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def wait
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loop do
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break if block_given? && yield
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message = poll_message(:nonblock, false)
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push(message) if message
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break if !block_given?
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end
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end
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# Adds the given packet to the packet queue. If the queue is non-empty,
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# #poll_message will return packets from the queue in the order they
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# were received.
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def push(packet)
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@queue.push(packet)
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end
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# Sends the given message via the packet stream, blocking until the
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# entire message has been sent.
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def send_message(message)
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socket.send_packet(message)
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end
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# Enqueues the given message, such that it will be sent at the earliest
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# opportunity. This does not block, but returns immediately.
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def enqueue_message(message)
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socket.enqueue_packet(message)
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end
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# Configure's the packet stream's client state with the given set of
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# options. This is typically used to define the cipher, compression, and
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# hmac algorithms to use when sending packets to the server.
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def configure_client(options={})
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socket.client.set(options)
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end
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# Configure's the packet stream's server state with the given set of
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# options. This is typically used to define the cipher, compression, and
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# hmac algorithms to use when reading packets from the server.
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def configure_server(options={})
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socket.server.set(options)
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end
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# Sets a new hint for the packet stream, which the packet stream may use
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# to change its behavior. (See PacketStream#hints).
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def hint(which, value=true)
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socket.hints[which] = value
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end
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public
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# this method is primarily for use in tests
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attr_reader :queue #:nodoc:
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private
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# Instantiates a new host-key verification class, based on the value of
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# the parameter. When true or nil, the default Lenient verifier is
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# returned. If it is false, the Null verifier is returned, and if it is
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# :very, the Strict verifier is returned. If the argument happens to
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# respond to :verify, it is returned directly. Otherwise, an exception
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# is raised.
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def select_host_key_verifier(paranoid)
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case paranoid
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when true, nil then
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Net::SSH::Verifiers::Lenient.new
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when false then
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Net::SSH::Verifiers::Null.new
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when :very then
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Net::SSH::Verifiers::Strict.new
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else
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if paranoid.respond_to?(:verify)
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paranoid
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else
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raise ArgumentError, "argument to :paranoid is not valid: #{paranoid.inspect}"
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end
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end
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end
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end
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end; end; end
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