1 files changed, 105 insertions, 0 deletions
diff --git a/lib/dnsxl_check.rb b/lib/dnsxl_check.rb
new file mode 100644
index 00000000000..1e506b2d9cb
--- /dev/null
+++ b/lib/dnsxl_check.rb
@@ -0,0 +1,105 @@
+require 'resolv'
+
+class DNSXLCheck
+
+  class Resolver
+    def self.search(query)
+      begin
+        Resolv.getaddress(query)
+        true
+      rescue Resolv::ResolvError
+        false
+      end
+    end
+  end
+
+  IP_REGEXP = /\A(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\.){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)\z/
+  DEFAULT_THRESHOLD = 0.33
+
+  def self.create_from_list(list)
+    dnsxl_check = DNSXLCheck.new
+
+    list.each do |entry|
+      dnsxl_check.add_list(entry.domain, entry.weight)
+    end
+
+    dnsxl_check
+  end
+
+  def test(ip)
+    if use_threshold?
+      test_with_threshold(ip)
+    else
+      test_strict(ip)
+    end
+  end
+
+  def test_with_threshold(ip)
+    return false if lists.empty?
+
+    search(ip)
+    final_score >= threshold
+  end
+
+  def test_strict(ip)
+    return false if lists.empty?
+
+    search(ip)
+    @score > 0
+  end
+
+  def use_threshold=(value)
+    @use_threshold = value == true
+  end
+
+  def use_threshold?
+    @use_threshold &&= true
+  end
+
+  def threshold=(threshold)
+    raise ArgumentError, "'threshold' value must be grather than 0 and less than or equal to 1" unless threshold > 0 && threshold <= 1
+    @threshold = threshold
+  end
+
+  def threshold
+    @threshold ||= DEFAULT_THRESHOLD
+  end
+
+  def add_list(domain, weight)
+    @lists ||= []
+    @lists << { domain: domain, weight: weight }
+  end
+
+  def lists
+    @lists ||= []
+  end
+
+  private
+
+  def search(ip)
+    raise ArgumentError, "'ip' value must be in #{IP_REGEXP} format" unless ip.match(IP_REGEXP)
+
+    @score = 0
+
+    reversed = reverse_ip(ip)
+    search_in_rbls(reversed)
+  end
+
+  def reverse_ip(ip)
+    ip.split('.').reverse.join('.')
+  end
+
+  def search_in_rbls(reversed_ip)
+    lists.each do |rbl|
+      query = "#{reversed_ip}.#{rbl[:domain]}"
+      @score += rbl[:weight] if Resolver.search(query)
+    end
+  end
+
+  def final_score
+    weights = lists.map{ |rbl| rbl[:weight] }.reduce(:+).to_i
+    return 0 if weights == 0
+
+    (@score.to_f / weights.to_f).round(2)
+  end
+end