discourse/lib/crawler_detection.rb

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# frozen_string_literal: true
module CrawlerDetection
WAYBACK_MACHINE_URL = "web.archive.org"
def self.to_matcher(string, type: nil)
escaped = string.split('|').map { |agent| Regexp.escape(agent) }.join('|')
if type == :real && Rails.env == "test"
# we need this bypass so we properly render views
escaped << "|Rails Testing"
end
Regexp.new(escaped, Regexp::IGNORECASE)
end
def self.crawler?(user_agent, via_header = nil)
return true if user_agent.nil? || via_header&.include?(WAYBACK_MACHINE_URL)
# this is done to avoid regenerating regexes
@non_crawler_matchers ||= {}
@matchers ||= {}
possibly_real = (@non_crawler_matchers[SiteSetting.non_crawler_user_agents] ||= to_matcher(SiteSetting.non_crawler_user_agents, type: :real))
if user_agent.match?(possibly_real)
known_bots = (@matchers[SiteSetting.crawler_user_agents] ||= to_matcher(SiteSetting.crawler_user_agents))
if user_agent.match?(known_bots)
bypass = (@matchers[SiteSetting.crawler_check_bypass_agents] ||= to_matcher(SiteSetting.crawler_check_bypass_agents))
!user_agent.match?(bypass)
else
false
end
else
true
end
end
# Given a user_agent that returns true from crawler?, should its request be allowed?
def self.allow_crawler?(user_agent)
return true if SiteSetting.whitelisted_crawler_user_agents.blank? &&
SiteSetting.blacklisted_crawler_user_agents.blank?
@whitelisted_matchers ||= {}
@blacklisted_matchers ||= {}
if SiteSetting.whitelisted_crawler_user_agents.present?
whitelisted = @whitelisted_matchers[SiteSetting.whitelisted_crawler_user_agents] ||= to_matcher(SiteSetting.whitelisted_crawler_user_agents)
!user_agent.nil? && user_agent.match?(whitelisted)
else
blacklisted = @blacklisted_matchers[SiteSetting.blacklisted_crawler_user_agents] ||= to_matcher(SiteSetting.blacklisted_crawler_user_agents)
user_agent.nil? || !user_agent.match?(blacklisted)
end
end
def self.is_blocked_crawler?(user_agent)
crawler?(user_agent) && !allow_crawler?(user_agent)
end
end