class HomographDetector

Constants

APPROVED_SCRIPT_COMBINATIONS: Certain combinations of Unicode Scripts are okay
CHINESE_SCRIPTS
JAPANESE_SCRIPTS
KOREAN_SCRIPTS
SCRIPT_BOPOMOFO: Unicode Script names returned by the 'unicode-scripts' gem
SCRIPT_COMMON
SCRIPT_CYRILLIC
SCRIPT_GREEK
SCRIPT_HAN
SCRIPT_HANGUL
SCRIPT_HIRAGANA
SCRIPT_INHERITED
SCRIPT_KATAKANA
SCRIPT_LATIN
SPECIAL_SCRIPTS: Groups of Unicode Scripts

Attributes

address[R]

Public Class Methods

homograph_attack?(address) click to toggle source

# File lib/homograph_detector.rb, line 40
def self.homograph_attack?(address)
  new(address).homograph_attack?
end

new(address) click to toggle source

# File lib/homograph_detector.rb, line 36
def initialize(address)
  @address = address
end

Public Instance Methods

homograph_attack?() click to toggle source

# File lib/homograph_detector.rb, line 44
def homograph_attack?
  # If we can't determine the Unicode Scripts for the domain, return false
  return false if domain_scripts.nil?

  # If the combination of Unicode Scripts used in the domain are ones we have
  # whitelisted, return false
  return false if domain_has_approved_combination_of_scripts?

  # If the combination of Unicode Scripts in the domain are problematic,
  # return true
  return true if domain_has_sketchy_combination_of_scripts?

  # If the domain is entirely composed of Cyrillic characters and each
  # character can be confusable with a Latin character, return true
  return true if domain_has_confusable_cyrillic_chars?

  false
end

Private Instance Methods

addressable_uri() click to toggle source

# File lib/homograph_detector.rb, line 119
        def addressable_uri
  @addressable_uri ||= Addressable::URI.parse(address)
end

domain_has_approved_combination_of_scripts?() click to toggle source

# File lib/homograph_detector.rb, line 88
        def domain_has_approved_combination_of_scripts?
  APPROVED_SCRIPT_COMBINATIONS.any? do |approved_script_combination|
    domain_scripts.subset?(approved_script_combination)
  end
end

domain_has_confusable_cyrillic_chars?() click to toggle source

# File lib/homograph_detector.rb, line 81
        def domain_has_confusable_cyrillic_chars?
  domain_without_tld.chars.all? do |char|
    Unicode::Scripts.scripts(char).include?(SCRIPT_CYRILLIC) &&
      Unicode::Confusable.skeleton(char) != char
  end
end

domain_has_sketchy_combination_of_scripts?() click to toggle source

Returns true if one of the following is satisfied:

Two Unicode Scripts are used in the domain, neither are 'Latin'
More than two Unicode Scripts are used in the domain
Two Unicode Scripts are used in the domain, one is 'Latin' and the other is either 'Cyrillic' or 'Greek'

# File lib/homograph_detector.rb, line 69
        def domain_has_sketchy_combination_of_scripts?
  (
    domain_scripts.length == 2 && !domain_scripts.include?(SCRIPT_LATIN) ||
      domain_scripts.length > 2 ||
      (
        domain_scripts.length == 2 &&
          (domain_scripts.include?(SCRIPT_CYRILLIC) ||
          domain_scripts.include?(SCRIPT_GREEK))
      )
  )
end

domain_scripts() click to toggle source

Retrieve the set of Unicode Scripts used in the domain name. If the domain name can't be parsed, return nil

# File lib/homograph_detector.rb, line 96
        def domain_scripts
  if domain_without_tld.nil?
    nil
  else
    @domain_scripts ||=
      Set[*Unicode::Scripts.scripts(domain_without_tld)] - SPECIAL_SCRIPTS
  end
end

domain_without_tld() click to toggle source

Retrieve the domain without the TLD. If there's a parsing error, return nil

# File lib/homograph_detector.rb, line 106
        def domain_without_tld
  @domain_without_tld ||=
    begin
      tld = addressable_uri.tld
    rescue Addressable::URI::InvalidURIError, PublicSuffix::Error
      # The `tld` can raise a couple different errors when called if the URI
      # is invalid.
      nil
    else
      addressable_uri.domain.chomp(tld).chomp('.')
    end
end