class Net::SSH::Transport::State

  1. lib/net/ssh/transport/state.rb
Parent: Transport

Encapsulates state information about one end of an SSH connection. Such state includes the packet sequence number, the algorithms in use, how many packets and blocks have been processed since the last reset, and so forth. This class will never be instantiated directly, but is used as part of the internal state of the PacketStream module.

Attributes

block_size [R]

The block size for the cipher
blocks [R]

The number of data blocks processed since the last call to reset!
cipher [R]

The cipher algorithm in use for this socket endpoint.
compression [R]

The compression algorithm in use for this endpoint.
compression_level [R]

The compression level to use when compressing data (or nil, for the default).
hmac [R]

The hmac algorithm in use for this endpoint.
max_blocks [RW]

The maximum number of blocks that this endpoint wants to process before needing a rekey.
max_packets [RW]

The maximum number of packets that this endpoint wants to process before needing a rekey.
packets [R]

The number of packets processed since the last call to reset!
rekey_limit [RW]

The user-specified maximum number of bytes that this endpoint ought to process before needing a rekey.
role [R]

The role that this state plays (either :client or :server)
sequence_number [R]

The next packet sequence number for this socket endpoint.
socket [R]

The socket object that owns this state object.

Public Class methods

new (socket, role)

Creates a new state object, belonging to the given socket. Initializes the algorithms to "none".

[show source] 
# File lib/net/ssh/transport/state.rb, line 57
def initialize(socket, role)
  @socket = socket
  @role = role
  @sequence_number = @packets = @blocks = 0
  @cipher = CipherFactory.get("none")
  @block_size = 8
  @hmac = HMAC.get("none")
  @compression = nil
  @compressor = @decompressor = nil
  @next_iv = ""
end

Public Instance methods

cleanup ()

Closes any the compressor and/or decompressor objects that have been instantiated.

[show source] 
# File lib/net/ssh/transport/state.rb, line 167
def cleanup
  if @compressor
    @compressor.finish if !@compressor.finished?
    @compressor.close
  end

  if @decompressor
    # we call reset here so that we don't get warnings when we try to
    # close the decompressor
    @decompressor.reset
    @decompressor.close
  end

  @compressor = @decompressor = nil
end
compress (data)

Compresses the data. If no compression is in effect, this will just return the data unmodified, otherwise it uses compressor to compress the data.

[show source] 
# File lib/net/ssh/transport/state.rb, line 120
def compress(data)
  data = data.to_s
  return data unless compression?
  compressor.deflate(data, Zlib::SYNC_FLUSH)
end
compression? ()

Returns true if data compression/decompression is enabled. This will return true if :standard compression is selected, or if :delayed compression is selected and the :authenticated hint has been received by the socket.

[show source] 
# File lib/net/ssh/transport/state.rb, line 114
def compression?
  compression == :standard || (compression == :delayed && socket.hints[:authenticated])
end
compressor ()

The compressor object to use when compressing data. This takes into account the desired compression level.

[show source] 
# File lib/net/ssh/transport/state.rb, line 101
def compressor
  @compressor ||= Zlib::Deflate.new(compression_level || Zlib::DEFAULT_COMPRESSION)
end
decompress (data)

Deompresses the data. If no compression is in effect, this will just return the data unmodified, otherwise it uses decompressor to decompress the data.

[show source] 
# File lib/net/ssh/transport/state.rb, line 128
def decompress(data)
  data = data.to_s
  return data unless compression?
  decompressor.inflate(data)
end
decompressor ()

The decompressor object to use when decompressing data.

[show source] 
# File lib/net/ssh/transport/state.rb, line 106
def decompressor
  @decompressor ||= Zlib::Inflate.new(nil)
end
final_cipher ()
[show source] 
# File lib/net/ssh/transport/state.rb, line 84
def final_cipher
  result = cipher.final
  update_next_iv(role == :client ? result : "", true)
  return result
end
increment (packet_length)

Increments the counters. The sequence number is incremented (and remapped so it always fits in a 32-bit integer). The number of packets and blocks are also incremented.

[show source] 
# File lib/net/ssh/transport/state.rb, line 93
def increment(packet_length)
  @sequence_number = (@sequence_number + 1) & 0xFFFFFFFF
  @packets += 1
  @blocks += (packet_length + 4) / @block_size
end
needs_rekey? ()

Returns true if the number of packets processed exceeds the maximum number of packets, or if the number of blocks processed exceeds the maximum number of blocks.

[show source] 
# File lib/net/ssh/transport/state.rb, line 186
def needs_rekey?
  max_packets && packets > max_packets ||
  max_blocks && blocks > max_blocks
end
reset! ()

Resets the counters on the state object, but leaves the sequence_number unchanged. It also sets defaults for and recomputes the max_packets and max_blocks values.

[show source] 
# File lib/net/ssh/transport/state.rb, line 137
def reset!
  @packets = @blocks = 0

  @max_packets ||= 1 << 31

  @block_size = cipher.name == "RC4" ? 8 : cipher.block_size

  if max_blocks.nil?
    # cargo-culted from openssh. the idea is that "the 2^(blocksize*2)
    # limit is too expensive for 3DES, blowfish, etc., so enforce a 1GB
    # limit for small blocksizes."
    if @block_size >= 16
      @max_blocks = 1 << (@block_size * 2)
    else
      @max_blocks = (1 << 30) / @block_size
    end

    # if a limit on the # of bytes has been given, convert that into a
    # minimum number of blocks processed.

    if rekey_limit
      @max_blocks = [@max_blocks, rekey_limit / @block_size].min
    end
  end

  cleanup
end
set (values)

A convenience method for quickly setting multiple values in a single command.

[show source] 
# File lib/net/ssh/transport/state.rb, line 71
def set(values)
  values.each do |key, value|
    instance_variable_set("@#{key}", value)
  end
  reset!
end
update_cipher (data)
[show source] 
# File lib/net/ssh/transport/state.rb, line 78
def update_cipher(data)
  result = cipher.update(data)
  update_next_iv(role == :client ? result : data)
  return result
end