84 lines
		
	
	
		
			3.1 KiB
		
	
	
	
		
			Ruby
		
	
	
	
			
		
		
	
	
			84 lines
		
	
	
		
			3.1 KiB
		
	
	
	
		
			Ruby
		
	
	
	
# frozen_string_literal: true
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class FetchResourceService < BaseService
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  include JsonLdHelper
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  ACCEPT_HEADER = 'application/activity+json, application/ld+json; profile="https://www.w3.org/ns/activitystreams", text/html;q=0.1'
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  ACTIVITY_STREAM_LINK_TYPES = ['application/activity+json', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'].freeze
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  attr_reader :response_code
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  def call(url)
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    return if url.blank?
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    process(url)
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  rescue HTTP::Error, OpenSSL::SSL::SSLError, Addressable::URI::InvalidURIError, Mastodon::HostValidationError, Mastodon::LengthValidationError => e
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    Rails.logger.debug { "Error fetching resource #{@url}: #{e}" }
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    nil
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  end
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  private
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  def process(url, terminal: false)
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    @url = url
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    perform_request { |response| process_response(response, terminal) }
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  end
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  def perform_request(&block)
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    Request.new(:get, @url).tap do |request|
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      request.add_headers('Accept' => ACCEPT_HEADER)
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      # In a real setting we want to sign all outgoing requests,
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      # in case the remote server has secure mode enabled and requires
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      # authentication on all resources. However, during development,
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      # sending request signatures with an inaccessible host is useless
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      # and prevents even public resources from being fetched, so
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      # don't do it
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      request.on_behalf_of(Account.representative) unless Rails.env.development?
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    end.perform(&block)
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  end
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  def process_response(response, terminal = false)
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    @response_code = response.code
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    return nil if response.code != 200
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    if ['application/activity+json', 'application/ld+json'].include?(response.mime_type)
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      body = response.body_with_limit
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      json = body_to_json(body)
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      [json['id'], { prefetched_body: body, id: true }] if supported_context?(json) && (equals_or_includes_any?(json['type'], ActivityPub::FetchRemoteActorService::SUPPORTED_TYPES) || expected_type?(json))
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    elsif !terminal
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      link_header = response['Link'] && parse_link_header(response)
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      if link_header&.find_link(%w(rel alternate))
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        process_link_headers(link_header)
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      elsif response.mime_type == 'text/html'
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        process_html(response)
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      end
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    end
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  end
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  def expected_type?(json)
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    equals_or_includes_any?(json['type'], ActivityPub::Activity::Create::SUPPORTED_TYPES + ActivityPub::Activity::Create::CONVERTED_TYPES)
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  end
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  def process_html(response)
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    page      = Nokogiri::HTML(response.body_with_limit)
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    json_link = page.xpath('//link[@rel="alternate"]').find { |link| ACTIVITY_STREAM_LINK_TYPES.include?(link['type']) }
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    process(json_link['href'], terminal: true) unless json_link.nil?
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  end
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  def process_link_headers(link_header)
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    json_link = link_header.find_link(%w(rel alternate), %w(type application/activity+json)) || link_header.find_link(%w(rel alternate), ['type', 'application/ld+json; profile="https://www.w3.org/ns/activitystreams"'])
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    process(json_link.href, terminal: true) unless json_link.nil?
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  end
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  def parse_link_header(response)
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    LinkHeader.parse(response['Link'].is_a?(Array) ? response['Link'].first : response['Link'])
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  end
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end
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