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require 'net/ssh'
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module Net
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  module SSH
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    class PubkeyVerifier
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      include Net::SSH::Transport::Constants
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      include Net::SSH::Authentication::Constants
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      attr_accessor :connection, :host, :key, :options, :user
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      def initialize(host,user, opts)
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        @host = host
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        # Parse public key data out into a PKey object
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        pubkey_data = opts.fetch(:key_data)
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        @key = Net::SSH::KeyFactory.load_data_public_key(pubkey_data)
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        @user = user
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        # Always set auth methods to ONLY publickey regardless
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        # of what the user sends
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        opts[:auth_methods] = ['publickey']
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        @options = Net::SSH.configuration_for(host, opts.fetch(:config, true)).merge(opts)
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      end
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      def auth_session(transport)
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        Net::SSH::Authentication::Session.new(transport,options)
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      end
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      def ssh_transport
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        Net::SSH::Transport::Session.new(host,options)
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      end
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      def verify
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        transport = ssh_transport
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        auth      = auth_session(transport)
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        transport.send_message(transport.service_request("ssh-userauth"))
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        auth.expect_message(SERVICE_ACCEPT)
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        # The initial public key exchange
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        pubkey_method = Net::SSH::Authentication::Methods::Publickey.new(auth)
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        pubkey_method.send(:send_request, key, user, "ssh-connection", key.ssh_type)
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        # Check the response to see if the public key is good
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        response_message = auth.next_message
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        case response_message.type
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          when USERAUTH_PK_OK
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            @connection = Net::SSH::Connection::Session.new(transport, options)
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            true
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          when USERAUTH_FAILURE
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            false
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          else
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            raise Net::SSH::Exception, "unexpected reply to USERAUTH_REQUEST: #{response_message.type} (#{response_message.inspect})"
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        end
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      end
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    end
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  end
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end
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