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Viewing changes to lib/net/ssh/transport/kex/diffie_hellman_group_exchange_sha1.rb

  • Committer: Bazaar Package Importer
  • Author(s): Lucas Nussbaum
  • Date: 2011-04-16 09:31:22 UTC
  • Revision ID: james.westby@ubuntu.com-20110416093122-rs6psd42v2hr371a
Tags: upstream-2.1.4
Import upstream version 2.1.4

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lib/net/ssh/transport/kex/diffie_hellman_group_exchange_sha1.rb
 
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require 'net/ssh/errors'
 
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require 'net/ssh/transport/constants'
 
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require 'net/ssh/transport/kex/diffie_hellman_group1_sha1'
 
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module Net::SSH::Transport::Kex
 
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  # A key-exchange service implementing the
 
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  # "diffie-hellman-group-exchange-sha1" key-exchange algorithm.
 
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  class DiffieHellmanGroupExchangeSHA1 < DiffieHellmanGroup1SHA1
 
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    MINIMUM_BITS      = 1024
 
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    MAXIMUM_BITS      = 8192
 
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    KEXDH_GEX_GROUP   = 31
 
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    KEXDH_GEX_INIT    = 32
 
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    KEXDH_GEX_REPLY   = 33
 
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    KEXDH_GEX_REQUEST = 34
 
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    private
 
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      # Compute the number of bits needed for the given number of bytes.
 
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      def compute_need_bits
 
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        need_bits = data[:need_bytes] * 8
 
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        if need_bits < MINIMUM_BITS
 
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          need_bits = MINIMUM_BITS
 
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        elsif need_bits > MAXIMUM_BITS
 
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          need_bits = MAXIMUM_BITS
 
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        end
 
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        data[:need_bits ] = need_bits
 
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        data[:need_bytes] = need_bits / 8
 
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      end
 
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      # Returns the DH key parameters for the given session.
 
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      def get_parameters
 
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        compute_need_bits
 
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        # request the DH key parameters for the given number of bits.
 
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        buffer = Net::SSH::Buffer.from(:byte, KEXDH_GEX_REQUEST, :long, MINIMUM_BITS,
 
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          :long, data[:need_bits], :long, MAXIMUM_BITS)
 
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        connection.send_message(buffer)
 
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        buffer = connection.next_message
 
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        unless buffer.type == KEXDH_GEX_GROUP
 
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          raise Net::SSH::Exception, "expected KEXDH_GEX_GROUP, got #{buffer.type}"
 
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        end
 
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        p = buffer.read_bignum
 
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        g = buffer.read_bignum
 
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        [p, g]
 
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      end
 
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      # Returns the INIT/REPLY constants used by this algorithm.
 
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      def get_message_types
 
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        [KEXDH_GEX_INIT, KEXDH_GEX_REPLY]
 
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      end
 
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      # Build the signature buffer to use when verifying a signature from
 
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      # the server.
 
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      def build_signature_buffer(result)
 
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        response = Net::SSH::Buffer.new
 
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        response.write_string data[:client_version_string],
 
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                              data[:server_version_string],
 
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                              data[:client_algorithm_packet],
 
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                              data[:server_algorithm_packet],
 
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                              result[:key_blob]
 
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        response.write_long MINIMUM_BITS,
 
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                            data[:need_bits],
 
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                            MAXIMUM_BITS
 
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        response.write_bignum dh.p, dh.g, dh.pub_key,
 
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                              result[:server_dh_pubkey],
 
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                              result[:shared_secret]
 
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        response
 
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      end
 
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  end
 
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end
 
 
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