class Net::SSH::Transport::ServerVersion

Negotiates the SSH protocol version and trades information about server and client. This is never used directly–it is always called by the transport layer as part of the initialization process of the transport layer.

Note that this class also encapsulates the negotiated version, and acts as the authoritative reference for any queries regarding the version in effect.

Constants

PROTO_VERSION

The SSH version string as reported by Net::SSH

Attributes

header[R]

Any header text sent by the server prior to sending the version.

version[R]

The version string reported by the server.

Public Class Methods

new(socket, logger, timeout = nil) click to toggle source

Instantiates a new ServerVersion and immediately (and synchronously) negotiates the SSH protocol in effect, using the given socket.

# File lib/net/ssh/transport/server_version.rb, line 29
def initialize(socket, logger, timeout = nil)
  @header = String.new
  @version = nil
  @logger = logger
  negotiate!(socket, timeout)
end

Private Instance Methods

negotiate!(socket, timeout) click to toggle source

Negotiates the SSH protocol to use, via the given socket. If the server reports an incompatible SSH version (e.g., SSH1), this will raise an exception.

# File lib/net/ssh/transport/server_version.rb, line 41
def negotiate!(socket, timeout)
  info { "negotiating protocol version" }

  debug { "local is `#{PROTO_VERSION}'" }
  socket.write "#{PROTO_VERSION}\r\n"
  socket.flush

  raise Net::SSH::ConnectionTimeout, "timeout during server version negotiating" if timeout && !IO.select([socket], nil, nil, timeout)

  loop do
    @version = String.new
    loop do
      begin
        b = socket.readpartial(1)
        raise Net::SSH::Disconnect, "connection closed by remote host" if b.nil?
      rescue EOFError
        raise Net::SSH::Disconnect, "connection closed by remote host"
      end
      @version << b
      break if b == "\n"
    end
    break if @version.match(/^SSH-/)

    @header << @version
  end

  @version.chomp!
  debug { "remote is `#{@version}'" }

  raise Net::SSH::Exception, "incompatible SSH version `#{@version}'" unless @version.match(/^SSH-(1\.99|2\.0)-/)

  raise Net::SSH::ConnectionTimeout, "timeout during client version negotiating" if timeout && !IO.select(nil, [socket], nil, timeout)
end