# frozen_string_literal: true
#
# ronin-exploits - A Ruby library for ronin-rb that provides exploitation and
# payload crafting functionality.
#
# Copyright (c) 2007-2023 Hal Brodigan (postmodern.mod3 at gmail.com)
#
# ronin-exploits 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-exploits 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-exploits.  If not, see <https://www.gnu.org/licenses/>.
#

module Ronin
  module Exploits
    module Mixins
      #
      # Generates NOP buffers.
      #
      # ## Examples
      #
      #     include Mixins::NOPS
      #
      #     arch :x86_64
      #
      #     def build
      #       buffer = ('A' * 1024) + nops(100) + payload
      #       # ...
      #     end
      #
      # @api public
      #
      # @since 1.0.0
      #
      module NOPS
        # Nop instructions for various architectures.
        #
        # @api private
        NOPS = {
          x86:    "\x90".b,            # nop
          x86_64: "\x90".b,            # nop
          arm:    "\x05P\xa0\xe1".b,   # mov r5, r5
          arm64:  "\xe5\x03\x05\xaa".b # mov x5, x5
          # TODO: mips
          # TODO: mips64
          # TODO: ppc
          # TODO: ppc64
        }

        #
        # Validates that the exploit defined an `arch` method and that all
        # required params are set.
        #
        # @raise [ValidationError]
        #   The exploit did not define an `arch` method, usually defined by
        #   {Mixins::HasTargets} or {Metadata::Arch}.
        #
        # @raise [Ronin::Core::Params::RequiredParam]
        #   One of the required params was not set.
        #
        # @api semipublic
        #
        def perform_validate
          unless respond_to?(:arch)
            raise(ValidationError,"exploit #{self.class} did not include Ronin::Exploits::Metadata::Arch or Ronin::Exploits::Mixins::HasTargets")
          end

          unless arch
            raise(ValidationError,"exploit #{self.class} did not include define an architecture")
          end

          super()
        end

        #
        # An individual NOP instruction for the target architecture of the
        # exploit.
        #
        # @return [String]
        #   The NOP instruction String.
        #
        # @raise [NotImplementedError]
        #   No NOP string was defined for the exploit's targeted architecture.
        #
        def nop
          NOPS.fetch(arch) do
            raise(NotImplementedError,"no NOP string is currently defined for the architecture: #{arch.inspect}")
          end
        end

        #
        # Creates a buffer of NOPs.
        #
        # @param [Integer] size
        #   The desired size of the nop buffer.
        #
        # @return [String]
        #   The NOPs buffer.
        #
        # @raise [NotImplementedError]
        #   No NOP string was defined for the exploit's targeted architecture.
        #
        # @api public
        #
        def nops(size)
          nop = self.nop

          return nop * (size / nop.bytesize)
        end
      end
    end
  end
end