Class: EventMachine::Ssh::PacketStream

Inherits:
Object
  • Object
show all
Includes:
Log, Net::SSH::BufferedIo
Defined in:
lib/em-ssh/packet-stream.rb

Instance Attribute Summary collapse

Instance Method Summary collapse

Methods included from Log

#debug, #error, #fatal, #info, #log, #warn

Constructor Details

#initialize(connection) ⇒ PacketStream

Returns a new instance of PacketStream.



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# File 'lib/em-ssh/packet-stream.rb', line 27

def initialize(connection)
  @connection = connection
  @input      = Net::SSH::Buffer.new
  @output     = Net::SSH::Buffer.new
  @hints      = {}
  @server     = Net::SSH::Transport::State.new(self, :server)
  @client     = Net::SSH::Transport::State.new(self, :client)
  @packet     = nil
end

Instance Attribute Details

#client ⇒ Object (readonly)

The client state object, which encapsulates the algorithms used to build packets to send to the server.



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# File 'lib/em-ssh/packet-stream.rb', line 20

def client
  @client
end

#hints ⇒ Object (readonly)

The map of “hints” that can be used to modify the behavior of the packet stream. For instance, when authentication succeeds, an “authenticated” hint is set, which is used to determine whether or not to compress the data when using the “delayed” compression algorithm.



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# File 'lib/em-ssh/packet-stream.rb', line 12

def hints
  @hints
end

#input ⇒ Object (readonly)

The input stream



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# File 'lib/em-ssh/packet-stream.rb', line 23

def input
  @input
end

#output ⇒ Object (readonly)

The output stream



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# File 'lib/em-ssh/packet-stream.rb', line 25

def output
  @output
end

#server ⇒ Object (readonly)

The server state object, which encapsulates the algorithms used to interpret packets coming from the server.



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# File 'lib/em-ssh/packet-stream.rb', line 16

def server
  @server
end

Instance Method Details

#cleanup ⇒ Object

Performs any pending cleanup necessary on the IO and its associated state objects. (See State#cleanup).



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# File 'lib/em-ssh/packet-stream.rb', line 146

def cleanup
  client.cleanup
  server.cleanup
end

#close ⇒ Object

initialize(content=“”)



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# File 'lib/em-ssh/packet-stream.rb', line 37

def close
  # remove reference to the connection to facilitate Garbage Collection
  return super.tap { @connection = nil } if respond_to?(:super)
  @connection = nil
end

#consume!(*args) ⇒ Object

Consumes n bytes from the buffer, where n is the current position unless otherwise specified. This is useful for removing data from the buffer that has previously been read, when you are expecting more data to be appended. It helps to keep the size of buffers down when they would otherwise tend to grow without bound.

Returns the buffer object itself.



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# File 'lib/em-ssh/packet-stream.rb', line 50

def consume!(*args)
  input.consume!(*args)
end

#if_needs_rekey? ⇒ Boolean

If the IO object requires a rekey operation (as indicated by either its client or server state objects, see State#needs_rekey?), this will yield. Otherwise, this does nothing. Copyright © 2008 Jamis Buck

Returns:

  • (Boolean) 


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# File 'lib/em-ssh/packet-stream.rb', line 155

def if_needs_rekey?
  if client.needs_rekey? || server.needs_rekey?
    yield
    client.reset! if client.needs_rekey?
    server.reset! if server.needs_rekey?
  end
end

#poll_next_packet ⇒ Object

Tries to read the next packet. If there is insufficient data to read an entire packet, this returns immediately, otherwise the packet is read, post-processed according to the cipher, hmac, and compression algorithms specified in the server state object, and returned as a new Packet object. Copyright © 2008 Jamis Buck



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# File 'lib/em-ssh/packet-stream.rb', line 60

def poll_next_packet
  if @packet.nil?
    minimum = server.block_size < 4 ? 4 : server.block_size
    return nil if available < minimum
    data = read_available(minimum)
    # decipher it
    @packet = Net::SSH::Buffer.new(server.update_cipher(data))
    @packet_length = @packet.read_long
  end
  need = @packet_length + 4 - server.block_size
  if need % server.block_size != 0
    @connection.fire(:error, SshError.new("padding error, need #{need} block #{server.block_size}"))
  end

  return nil if available < need + server.hmac.mac_length

  if need > 0
    # read the remainder of the packet and decrypt it.
    data = read_available(need)
    @packet.append(server.update_cipher(data))
  end

  # get the hmac from the tail of the packet (if one exists), and
  # then validate it.
  real_hmac = read_available(server.hmac.mac_length) || ""

  @packet.append(server.final_cipher)
  padding_length = @packet.read_byte

  payload = @packet.read(@packet_length - padding_length - 1)
  padding = @packet.read(padding_length) if padding_length > 0

  my_computed_hmac = server.hmac.digest([server.sequence_number, @packet.content].pack("NA*"))
  if real_hmac != my_computed_hmac
    @connection.fire(:error, Net::SSH::Exception.new("corrupted mac detected"))
    return
  end

  # try to decompress the payload, in case compression is active
  payload = server.decompress(payload)

  log.debug("received packet nr #{server.sequence_number} type #{payload.getbyte(0)} len #{@packet_length}")

  server.increment(@packet_length)
  @packet = nil

  return Net::SSH::Packet.new(payload)
end

#send_packet(payload) ⇒ Object

Copyright © 2008 Jamis Buck



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# File 'lib/em-ssh/packet-stream.rb', line 110

def send_packet(payload)
  # try to compress the packet
  payload = client.compress(payload)

  # the length of the packet, minus the padding
  actual_length = 4 + payload.length + 1

  # compute the padding length
  padding_length = client.block_size - (actual_length % client.block_size)
  padding_length += client.block_size if padding_length < 4

  # compute the packet length (sans the length field itself)
  packet_length = payload.length + padding_length + 1
  if packet_length < 16
    padding_length += client.block_size
    packet_length = payload.length + padding_length + 1
  end

  padding = Array.new(padding_length) { rand(256) }.pack("C*")

  unencrypted_data = [packet_length, padding_length, payload, padding].pack("NCA*A*")
  mac = client.hmac.digest([client.sequence_number, unencrypted_data].pack("NA*"))

  encrypted_data = client.update_cipher(unencrypted_data) << client.final_cipher
  message = encrypted_data + mac

  log.debug("queueing packet nr #{client.sequence_number} type #{payload.getbyte(0)} len #{packet_length}")
  @connection.send_data(message)
  log.debug("sent #{message.length} bytes")
  client.increment(packet_length)

  self
end