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Net::SSH::Transport::State

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

socket[R]

The socket object that owns this state object.

sequence_number[R]

The next packet sequence number for this socket endpoint.

hmac[R]

The hmac algorithm in use for this 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).

packets[R]

The number of packets processed since the last call to #

blocks[R]

The number of data blocks processed since the last call to #

cipher[R]

The cipher algorithm in use for this socket endpoint.

block_size[R]

The block size for the cipher

role[R]

The role that this state plays (either :client or :server)

max_packets[RW]

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

max_blocks[RW]

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

rekey_limit[RW]

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

Public Class Methods

new(socket, role) click to toggle source

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

    # File lib/net/ssh/transport/state.rb, line 57
57:     def initialize(socket, role)
58:       @socket = socket
59:       @role = role
60:       @sequence_number = @packets = @blocks = 0
61:       @cipher = CipherFactory.get("none")
62:       @block_size = 8
63:       @hmac = HMAC.get("none")
64:       @compression = nil
65:       @compressor = @decompressor = nil
66:       @next_iv = ""
67:     end

Public Instance Methods

cleanup() click to toggle source

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

     # File lib/net/ssh/transport/state.rb, line 167
167:     def cleanup
168:       if @compressor
169:         @compressor.finish if !@compressor.finished?
170:         @compressor.close
171:       end
172: 
173:       if @decompressor
174:         # we call reset here so that we don't get warnings when we try to
175:         # close the decompressor
176:         @decompressor.reset
177:         @decompressor.close
178:       end
179: 
180:       @compressor = @decompressor = nil
181:     end
compress(data) click to toggle source

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

     # File lib/net/ssh/transport/state.rb, line 120
120:     def compress(data)
121:       data = data.to_s
122:       return data unless compression?
123:       compressor.deflate(data, Zlib::SYNC_FLUSH)
124:     end
compression?() click to toggle source

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.

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

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

     # File lib/net/ssh/transport/state.rb, line 101
101:     def compressor
102:       @compressor ||= Zlib::Deflate.new(compression_level || Zlib::DEFAULT_COMPRESSION)
103:     end
decompress(data) click to toggle source

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

     # File lib/net/ssh/transport/state.rb, line 128
128:     def decompress(data)
129:       data = data.to_s
130:       return data unless compression?
131:       decompressor.inflate(data)
132:     end
decompressor() click to toggle source

The decompressor object to use when decompressing data.

     # File lib/net/ssh/transport/state.rb, line 106
106:     def decompressor
107:       @decompressor ||= Zlib::Inflate.new(nil)
108:     end
final_cipher() click to toggle source
    # File lib/net/ssh/transport/state.rb, line 84
84:     def final_cipher
85:       result = cipher.final
86:       update_next_iv(role == :client ? result : "", true)
87:       return result
88:     end
increment(packet_length) click to toggle source

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.

    # File lib/net/ssh/transport/state.rb, line 93
93:     def increment(packet_length)
94:       @sequence_number = (@sequence_number + 1) & 0xFFFFFFFF
95:       @packets += 1
96:       @blocks += (packet_length + 4) / @block_size
97:     end
needs_rekey?() click to toggle source

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.

     # File lib/net/ssh/transport/state.rb, line 186
186:     def needs_rekey?
187:       max_packets && packets > max_packets ||
188:       max_blocks && blocks > max_blocks
189:     end
reset!() click to toggle source

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.

     # File lib/net/ssh/transport/state.rb, line 137
137:     def reset!
138:       @packets = @blocks = 0
139: 
140:       @max_packets ||= 1 << 31
141: 
142:       @block_size = cipher.name == "RC4" ? 8 : cipher.block_size
143: 
144:       if max_blocks.nil?
145:         # cargo-culted from openssh. the idea is that "the 2^(blocksize*2)
146:         # limit is too expensive for 3DES, blowfish, etc., so enforce a 1GB
147:         # limit for small blocksizes."
148:         if @block_size >= 16
149:           @max_blocks = 1 << (@block_size * 2)
150:         else
151:           @max_blocks = (1 << 30) / @block_size
152:         end
153: 
154:         # if a limit on the # of bytes has been given, convert that into a
155:         # minimum number of blocks processed.
156: 
157:         if rekey_limit
158:           @max_blocks = [@max_blocks, rekey_limit / @block_size].min
159:         end
160:       end
161: 
162:       cleanup
163:     end
set(values) click to toggle source

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

    # File lib/net/ssh/transport/state.rb, line 71
71:     def set(values)
72:       values.each do |key, value|
73:         instance_variable_set("@#{key}", value)
74:       end
75:       reset!
76:     end
update_cipher(data) click to toggle source
    # File lib/net/ssh/transport/state.rb, line 78
78:     def update_cipher(data)
79:       result = cipher.update(data)
80:       update_next_iv(role == :client ? result : data)
81:       return result
82:     end

Private Instance Methods

update_next_iv(data, reset=false) click to toggle source
     # File lib/net/ssh/transport/state.rb, line 193
193:       def update_next_iv(data, reset=false)
194:         @next_iv << data
195:         @next_iv = @next_iv[-cipher.iv_len..1]
196: 
197:         if reset
198:           cipher.reset
199:           cipher.iv = @next_iv
200:         end
201: 
202:         return data
203:       end

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