Module: Net::SSH::Transport::PacketStream

Includes:
BufferedIo
Defined in:
lib/net/ssh/transport/packet_stream.rb

Overview

A module that builds additional functionality onto the Net::SSH::BufferedIo module. It adds SSH encryption, compression, and packet validation, as per the SSH2 protocol. It also adds an abstraction for polling packets, to allow for both blocking and non-blocking reads.

Instance Attribute Summary collapse

Attributes included from Loggable

#logger

Class Method Summary collapse

Instance Method Summary collapse

Methods included from BufferedIo

#available, #enqueue, #fill, #pending_write?, #read_available, #read_buffer, #send_pending, #wait_for_pending_sends, #write_buffer

Methods included from Loggable

#debug, #error, #fatal, #info, #lwarn

Instance Attribute Details

#client ⇒ Object (readonly)

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



33
34
35
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 33

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.



25
26
27
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 25

def hints
  @hints
end

#server ⇒ Object (readonly)

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



29
30
31
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 29

def server
  @server
end

Class Method Details

.extended(object) ⇒ Object 



17
18
19
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 17

def self.extended(object)
  object.__send__(:initialize_ssh)
end

Instance Method Details

#available_for_read? ⇒ Boolean

Returns true if the IO is available for reading, and false otherwise.

Returns:

  • (Boolean) 


67
68
69
70
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 67

def available_for_read?
  result = IO.select([self], nil, nil, 0)
  result && result.first.any?
end

#cleanup ⇒ Object

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



150
151
152
153
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 150

def cleanup
  client.cleanup
  server.cleanup
end

#client_name ⇒ Object

The name of the client (local) end of the socket, as reported by the socket.



37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 37

def client_name
  @client_name ||= begin
    sockaddr = getsockname
    begin
      Socket.getnameinfo(sockaddr, Socket::NI_NAMEREQD).first
    rescue
      begin
        Socket.getnameinfo(sockaddr).first
      rescue
        begin
          Socket.gethostbyname(Socket.gethostname).first
        rescue
          lwarn { "the client ipaddr/name could not be determined" }
          "unknown"
        end
      end
    end
  end
end

#enqueue_packet(payload) ⇒ Object

Enqueues a packet to be sent, but does not immediately send the packet. The given payload is pre-processed according to the algorithms specified in the client state (compression, cipher, and hmac).



113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 113

def enqueue_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

  debug { "queueing packet nr #{client.sequence_number} type #{payload.getbyte(0)} len #{packet_length}" }
  enqueue(message)

  client.increment(packet_length)

  self
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.

Returns:

  • (Boolean) 


158
159
160
161
162
163
164
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 158

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

#next_packet(mode = :nonblock) ⇒ Object

Returns the next full packet. If the mode parameter is :nonblock (the default), then this will return immediately, whether a packet is available or not, and will return nil if there is no packet ready to be returned. If the mode parameter is :block, then this method will block until a packet is available.



77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 77

def next_packet(mode=:nonblock)
  case mode
  when :nonblock then
    fill if available_for_read?
    poll_next_packet

  when :block then
    loop do
      packet = poll_next_packet
      return packet if packet

      loop do
        result = IO.select([self]) or next
        break if result.first.any?
      end

      if fill <= 0
        raise Net::SSH::Disconnect, "connection closed by remote host"
      end
    end

  else
    raise ArgumentError, "expected :block or :nonblock, got #{mode.inspect}"
  end
end

#peer_ip ⇒ Object

The IP address of the peer (remote) end of the socket, as reported by the socket.



59
60
61
62
63
64
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 59

def peer_ip
  @peer_ip ||= begin
    addr = getpeername
    Socket.getnameinfo(addr, Socket::NI_NUMERICHOST | Socket::NI_NUMERICSERV).first
  end
end

#send_packet(payload) ⇒ Object

Enqueues a packet to be sent, and blocks until the entire packet is sent.



105
106
107
108
 
# File 'lib/net/ssh/transport/packet_stream.rb', line 105

def send_packet(payload)
  enqueue_packet(payload)
  wait_for_pending_sends
end