#
# Copyright (c) 2006-2021 Hal Brodigan (postmodern.mod3 at gmail.com)
#
# This file is part of ronin-support.
#
# ronin-support is free software: you can redistribute it and/or modify
# it under the terms of the GNU Lesser General Public License as published
# by the Free Software Foundation, either version 3 of the License, or
# (at your option) any later version.
#
# ronin-support is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU Lesser General Public License for more details.
#
# You should have received a copy of the GNU Lesser General Public License
# along with ronin-support.  If not, see <https://www.gnu.org/licenses/>.
#

require 'socket'
require 'timeout'

module Ronin
  module Network
    #
    # Provides helper methods for using the TCP protocol.
    #
    module TCP
      #
      # Tests whether a remote TCP port is open.
      #
      # @param [String] host
      #   The host to connect to.
      #
      # @param [Integer] port
      #   The port to connect to.
      #
      # @param [String] local_host (nil)
      #   The local host to bind to.
      #
      # @param [Integer] local_port (nil)
      #   The local port to bind to.
      #
      # @param [Integer] timeout (5)
      #   The maximum time to attempt connecting.
      #
      # @return [Boolean, nil]
      #   Specifies whether the remote TCP port is open.
      #   If the connection was not accepted, `nil` will be returned.
      #
      # @example
      #   tcp_open?('example.com',80)
      #   # => true
      #
      # @example Using a timeout:
      #   tcp_open?('example.com',1111,nil,nil,5)
      #   # => nil
      #
      # @api public
      #
      # @since 0.5.0
      #
      def tcp_open?(host,port,local_host=nil,local_port=nil,timeout=nil)
        timeout ||= 5

        begin
          Timeout.timeout(timeout) do
            tcp_session(host,port,local_host,local_port)
          end

          return true
        rescue Timeout::Error
          return nil
        rescue SocketError, SystemCallError
          return false
        end
      end

      #
      # Creates a new TCPSocket object connected to a given host and port.
      #
      # @param [String] host
      #   The host to connect to.
      #
      # @param [Integer] port
      #   The port to connect to.
      #
      # @param [String] local_host (nil)
      #   The local host to bind to.
      #
      # @param [Integer] local_port (nil)
      #   The local port to bind to.
      #
      # @yield [socket]
      #   If a block is given, it will be passed the newly created socket.
      #
      # @yieldparam [TCPsocket] socket
      #   The newly created TCPSocket object.
      #
      # @return [TCPSocket]
      #   The newly created TCPSocket object.
      #
      # @example
      #   tcp_connect('www.hackety.org',80) # => TCPSocket
      #
      # @example
      #   tcp_connect('www.wired.com',80) do |socket|
      #     socket.write("GET /\n\n")
      #
      #     puts socket.readlines
      #     socket.close
      #   end
      #
      # @see https://rubydoc.info/stdlib/socket/TCPSocket
      #
      # @api public
      #
      def tcp_connect(host,port,local_host=nil,local_port=nil)
        host = host.to_s
        port = port.to_i

        socket = if local_host || local_port
                   local_host = local_host.to_s
                   local_port = local_port.to_i

                   TCPSocket.new(host,port,local_host,local_port)
                 else
                   TCPSocket.new(host,port)
                 end

        yield socket if block_given?
        return socket
      end

      #
      # Creates a new TCPSocket object, connected to a given host and port.
      # The given data will then be written to the newly created TCPSocket.
      #
      # @param [String] data
      #   The data to send through the connection.
      #
      # @param [String] host
      #   The host to connect to.
      #
      # @param [Integer] port
      #   The port to connect to.
      #
      # @param [String] local_host (nil)
      #   The local host to bind to.
      #
      # @param [Integer] local_port (nil)
      #   The local port to bind to.
      #
      # @yield [socket]
      #   If a block is given, it will be passed the newly created socket.
      #
      # @yieldparam [TCPSocket] socket
      #   The newly created TCPSocket object.
      #
      # @api public
      #
      def tcp_connect_and_send(data,host,port,local_host=nil,local_port=nil)
        socket = tcp_connect(host,port,local_host,local_port)
        socket.write(data)

        yield socket if block_given?
        return socket
      end

      #
      # Creates a new temporary TCPSocket object, connected to the given host
      # and port.
      #
      # @param [String] host
      #   The host to connect to.
      #
      # @param [Integer] port
      #   The port to connect to.
      #
      # @param [String] local_host (nil)
      #   The local host to bind to.
      #
      # @param [Integer] local_port (nil)
      #   The local port to bind to.
      #
      # @yield [socket]
      #   If a block is given, it will be passed the newly created socket.
      #   After the block has returned, the socket will then be closed.
      #
      # @yieldparam [TCPsocket] socket
      #   The newly created TCPSocket object.
      #
      # @return [nil]
      #
      # @api public
      #
      def tcp_session(host,port,local_host=nil,local_port=nil)
        socket = tcp_connect(host,port,local_host,local_port)

        yield socket if block_given?
        socket.close
        return nil
      end

      #
      # Reads the banner from the service running on the given host and port.
      #
      # @param [String] host
      #   The host to connect to.
      #
      # @param [Integer] port
      #   The port to connect to.
      #
      # @param [String] local_host (nil)
      #   The local host to bind to.
      #
      # @param [Integer] local_port (nil)
      #   The local port to bind to.
      #
      # @yield [banner]
      #   If a block is given, it will be passed the grabbed banner.
      #
      # @yieldparam [String] banner
      #   The grabbed banner.
      #
      # @return [String]
      #   The grabbed banner.
      #
      # @example
      #   tcp_banner('pop.gmail.com',25)
      #   # => "220 mx.google.com ESMTP c20sm3096959rvf.1"
      #
      # @api public
      #
      def tcp_banner(host,port,local_host=nil,local_port=nil)
        banner = nil

        tcp_session(host,port,local_host,local_port) do |socket|
          banner = socket.readline.strip
        end

        yield banner if block_given?
        return banner
      end

      #
      # Connects to a specified host and port, sends the given data and then
      # closes the connection.
      #
      # @param [String] data
      #   The data to send through the connection.
      #
      # @param [String] host
      #   The host to connect to.
      #
      # @param [Integer] port
      #   The port to connect to.
      #
      # @param [String] local_host (nil)
      #   The local host to bind to.
      #
      # @param [Integer] local_port (nil)
      #   The local port to bind to.
      #
      # @return [true]
      #   The data was successfully sent.
      #
      # @example
      #   buffer = "GET /" + ('A' * 4096) + "\n\r"
      #   tcp_send(buffer,'victim.com',80)
      #   # => true
      #
      # @api public
      #
      def tcp_send(data,host,port,local_host=nil,local_port=nil)
        tcp_session(host,port,local_host,local_port) do |socket|
          socket.write(data)
        end

        return true
      end

      #
      # Creates a new TCPServer listening on a given host and port.
      #
      # @param [Integer] port (nil)
      #   The local port to listen on.
      #
      # @param [String] host (nil)
      #   The host to bind to.
      #
      # @param [Integer] backlog (5)
      #   The maximum backlog of pending connections.
      #
      # @yield [server]
      #   The block which will be called after the server has been created.
      #
      # @yieldparam [TCPServer] server
      #   The newly created TCP server.
      #
      # @return [TCPServer]
      #   The new TCP server.
      #
      # @example
      #   tcp_server(1337)
      #
      # @see https://rubydoc.info/stdlib/socket/TCPServer
      #
      # @api public
      #
      def tcp_server(port=nil,host=nil,backlog=5)
        port = port.to_i

        server = if host
                   host = host.to_s
                   TCPServer.new(host,port)
                 else
                   TCPServer.new(port)
                 end
        server.listen(backlog)

        yield server if block_given?
        return server
      end

      #
      # Creates a new temporary TCPServer listening on a host and port.
      #
      # @param [Integer] port (nil)
      #   The local port to bind to.
      #
      # @param [String] host (nil)
      #   The host to bind to.
      #
      # @param [Integer] backlog (5)
      #   The maximum backlog of pending connections.
      #
      # @yield [server]
      #   The block which will be called after the server has been created.
      #   After the block has finished, the server will be closed.
      #
      # @yieldparam [TCPServer] server
      #   The newly created TCP server.
      #
      # @return [nil]
      #
      # @example
      #   tcp_server_session(1337) do |server|
      #     client1 = server.accept
      #     client2 = server.accept
      #
      #     client2.write(server.read_line)
      #
      #     client1.close
      #     client2.close
      #   end
      #
      # @api public
      #
      def tcp_server_session(port=nil,host=nil,backlog=5,&block)
        server = tcp_server(port,host,backlog,&block)
        server.close()
        return nil
      end

      #
      # Creates a new TCPServer listening on a given host and port,
      # accepting clients in a loop.
      #
      # @param [Integer] port (nil)
      #   The local port to bind to.
      #
      # @param [String] host (nil)
      #   The host to bind to.
      #
      # @yield [client]
      #   The given block will be passed the newly connected client.
      #   After the block has finished, the client will be closed.
      #
      # @yieldparam [TCPSocket] client
      #   A newly connected client.
      #
      # @return [nil]
      #
      # @example
      #   tcp_server_loop(1337) do |client|
      #     client.puts 'lol'
      #   end
      #
      # @api public
      #
      # @since 0.5.0
      #
      def tcp_server_loop(port=nil,host=nil)
        tcp_server_session(port,host) do |server|
          loop do
            client = server.accept

            yield client if block_given?
            client.close
          end
        end
      end

      #
      # Creates a new TCPServer listening on a given host and port,
      # accepts only one client and then stops listening.
      #
      # @param [Integer] port (nil)
      #   The local port to bind to.
      #
      # @param [String] host (nil
      #   The host to bind to.
      #
      # @yield [client]
      #   The given block will be passed the newly connected client.
      #   After the block has finished, both the client and the server will be
      #   closed.
      #
      # @yieldparam [TCPSocket] client
      #   The newly connected client.
      #
      # @return [nil]
      #
      # @example
      #   tcp_accept(1337) do |client|
      #     client.puts 'lol'
      #   end
      #
      # @api public
      #
      # @since 0.5.0
      #
      def tcp_accept(port=nil,host=nil)
        tcp_server_session(port,host,1) do |server|
          client = server.accept

          yield client if block_given?
          client.close
        end
      end

      #
      # @deprecated
      #   Deprecated as of 0.5.0. Use {#tcp_accept} instead.
      #
      def tcp_single_server(port=nil,host=nil)
        tcp_accept(port,host)
      end
    end
  end
end