185: def poll_next_packet
186: if @packet.nil?
187: minimum = server.block_size < 4 ? 4 : server.block_size
188: return nil if available < minimum
189: data = read_available(minimum)
190:
191:
192: @packet = Net::SSH::Buffer.new(server.update_cipher(data))
193: @packet_length = @packet.read_long
194: end
195:
196: need = @packet_length + 4 - server.block_size
197: raise Net::SSH::Exception, "padding error, need #{need} block #{server.block_size}" if need % server.block_size != 0
198:
199: return nil if available < need + server.hmac.mac_length
200:
201: if need > 0
202:
203: data = read_available(need)
204: @packet.append(server.update_cipher(data))
205: end
206:
207:
208:
209: real_hmac = read_available(server.hmac.mac_length) || ""
210:
211: @packet.append(server.final_cipher)
212: padding_length = @packet.read_byte
213:
214: payload = @packet.read(@packet_length - padding_length - 1)
215: padding = @packet.read(padding_length) if padding_length > 0
216:
217: my_computed_hmac = server.hmac.digest([server.sequence_number, @packet.content].pack("NA*"))
218: raise Net::SSH::Exception, "corrupted mac detected" if real_hmac != my_computed_hmac
219:
220:
221: payload = server.decompress(payload)
222:
223: debug { "received packet nr #{server.sequence_number} type #{payload.getbyte(0)} len #{@packet_length}" }
224:
225: server.increment(@packet_length)
226: @packet = nil
227:
228: return Packet.new(payload)
229: end