Module: WebriskHash::Canonicalizer

Extended by:
Canonicalizer
Included in:
WebriskHash, Canonicalizer
Defined in:
lib/webrisk_hash/canonicalizer.rb

Overview

URL Canonicalization for Web Risk API

Implements the canonicalization process described in the Web Risk API documentation: https://cloud.google.com/web-risk/docs/urls-hashing#canonicalization

The canonicalization process includes:

  1. Parse URL according to RFC 2396 (convert IDN to ASCII Punycode if needed)
  2. Remove tab (0x09), CR (0x0d), and LF (0x0a) characters
  3. Remove URL fragments
  4. Repeatedly percent-unescape until no more percent-escapes
  5. Normalize hostname:
    • Remove leading/trailing dots
    • Replace consecutive dots with single dot
    • Parse and normalize IP addresses (handle octal, hex, decimal)
    • Lowercase the entire hostname
  6. Canonicalize path:
    • Resolve /../ and /./ sequences
    • Replace consecutive slashes with single slash
  7. Percent-escape characters <= ASCII 32, >= 127, #, and %
  8. Do NOT apply path canonicalization to query parameters
  9. Remove default ports (80 for HTTP, 443 for HTTPS)

See Also:

Instance Method Summary collapse

Instance Method Details

#canonicalize(url) ⇒ String?

Canonicalize a URL according to Web Risk API specification

Examples:

canonicalize("http://host/%25%32%35")
# => "http://host/%25"

canonicalize("http://www.GOOgle.com/")
# => "http://www.google.com/"

canonicalize("http://3279880203/blah")
# => "http://195.127.0.11/blah"

Parameters:

  • The URL to canonicalize

Returns:

  • The canonicalized URL or nil if invalid



45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 45

def canonicalize(url)
  return nil if url.nil?

  raw = url.dup.force_encoding(Encoding::BINARY)
  raw = raw.gsub(/[\t\r\n]/, '')
  raw = raw.sub(/\A +/n, '').sub(/ +\z/n, '')
  url_with_scheme = raw.include?('://') ? raw : "http://#{raw}"
  url_with_scheme = url_with_scheme.gsub(%r{(?<=://)([^/]*)}) { |auth| auth.gsub(' ', '%20') }

  begin
    a = Addressable::URI.parse(url_with_scheme)
  rescue StandardError
    return nil
  end

  schema = a.scheme
  if a.user
    a.user + (a.password ? ":#{a.password}" : '')
  end
  host = a.host
  after_scheme = url_with_scheme.sub(%r{\A[^:]+://}, '')
  slash_idx = after_scheme.index('/')
  path_and_query = slash_idx ? after_scheme[slash_idx..] : '/'

  path_and_query = path_and_query.split('#', 2)[0]

  if path_and_query.include?('?')
    raw_path, raw_query = path_and_query.split('?', 2)
  else
    raw_path = path_and_query
    raw_query = nil
  end
  path = raw_path && !raw_path.empty? ? raw_path : '/'
  query = raw_query

  return nil if schema.nil? || host.nil? || host.length > 255

  host_decoded = custom_decode_uri_component(normalize_ip_address(host)).gsub(/[\t\x0a\x0d]/, '')

  begin
    host_ascii = if /[^\x00-\x7F]/.match?(host_decoded)
                   Addressable::IDNA.to_ascii(host_decoded)
                 else
                   host_decoded
                 end
  rescue StandardError
    host_ascii = host_decoded
  end

  normalized_host = webrisk_uri_escape(host_ascii)
  normalized_host = normalized_host.squeeze('.').gsub(/\A\.+|\.+\z/, '').downcase

  normalized_path = normalize_component_encoding(normalize_dots_in_paths(path))
  normalized_path = "#{normalized_path}/" if path.end_with?('/') && !normalized_path.end_with?('/')

  normalized_query = query ? "?#{query}" : ''

  "#{schema}://#{normalized_host}#{normalized_path}#{normalized_query}"
end

#custom_decode_uri_component(input) ⇒ Object 



174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 174

def custom_decode_uri_component(input)
  replace_map = { '%FE%FF' => "\uFFFD\uFFFD", '%FF%FE' => "\uFFFD\uFFFD" }
  multi_matcher = /((?:%[a-f0-9]{2})+)/i
  input.scan(multi_matcher).flatten.each do |match|
    replace_map[match] = URI.decode_www_form_component(match)
  rescue StandardError
    decoded = safe_decode(match)
    replace_map[match] = decoded if decoded != match
  end
  replace_map['%C2'] = "\uFFFD"
  replace_map.each do |k, v|
    input = input.gsub(Regexp.new(Regexp.escape(k), Regexp::IGNORECASE), v)
  end
  input
end

#escape_character(code) ⇒ Object 



204
205
206
207
208
209
210
211
212
213
214
215
216
217
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 204

def escape_character(code)
  chr = code.chr(Encoding::UTF_8)
  if code < 256
    if code < 16
      format('%%%02X', code)
    elsif code <= 32 || code > 127 || chr == '%' || chr == '#'
      format('%%%02X', code)
    else
      chr
    end
  else
    escape_character(code >> 8) + escape_character(code % 256)
  end
end

#int2ip(ip_int) ⇒ Object 



105
106
107
108
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 105

def int2ip(ip_int)
  num = ip_int.to_i
  [(num >> 24) & 255, (num >> 16) & 255, (num >> 8) & 255, num & 255].join('.')
end

#normalize_component_encoding(c) ⇒ Object 



146
147
148
149
150
151
152
153
154
155
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 146

def normalize_component_encoding(c)
  value = c
  prev_value = nil
  1000.times do
    prev_value = value
    value = custom_decode_uri_component(prev_value).gsub(/[\t\x0a\x0d]/, '')
    break if value == prev_value
  end
  webrisk_uri_escape(value)
end

#normalize_dots_in_paths(path) ⇒ Object 



157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 157

def normalize_dots_in_paths(path)
  segments = path.split('/')
  new_segments = []
  empty_or_dot = ['', '.'].freeze
  segments.each do |seg|
    next if empty_or_dot.include?(seg)

    if seg == '..'
      new_segments.pop unless new_segments.empty?
    else
      new_segments << seg
    end
  end
  result = "/#{new_segments.join('/')}"
  result == '' ? '/' : result
end

#normalize_ip_address(c) ⇒ Object 



110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 110

def normalize_ip_address(c)
  begin
    parts = c.split('.')
    parse_part = lambda do |p|
      if /^0x/i.match?(p)
        Integer(p)
      elsif p =~ /^0[0-9]+$/ && p.length > 1
        Integer(p, 8)
      else
        Integer(p)
      end
    end

    if parts.length == 1
      n = parse_part.call(parts[0])
      return int2ip(n) if n.between?(0, 0xFFFFFFFF)
    elsif parts.length <= 4 && parts.all? { |p| p =~ /^([0-9]+|0x[0-9a-fA-F]+|0[0-7]*)$/ }
      nums = parts.map { |p| parse_part.call(p) }
      ip_int = case nums.length
               when 1
                 nums[0]
               when 2
                 (nums[0] << 24) | (nums[1] & 0xFFFFFF)
               when 3
                 (nums[0] << 24) | ((nums[1] & 0xFF) << 16) | (nums[2] & 0xFFFF)
               when 4
                 (nums[0] << 24) | ((nums[1] & 0xFF) << 16) | ((nums[2] & 0xFF) << 8) | (nums[3] & 0xFF)
               end
      return int2ip(ip_int) if ip_int.between?(0, 0xFFFFFFFF)
    end
  rescue StandardError
    nil
  end
  c
end

#safe_decode(input) ⇒ Object 



190
191
192
193
194
195
196
197
198
199
200
201
202
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 190

def safe_decode(input)
  tokens = input.scan(/%[a-f0-9]{2}/i).map { |t| t }
  (1..tokens.length).each do |split|
    left = tokens[0, split]
    right = tokens[split..] || []
    begin
      return URI.decode_www_form_component((left + right).join)
    rescue StandardError
      next
    end
  end
  input
end

#webrisk_uri_escape(s) ⇒ Object 



219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
 
# File 'lib/webrisk_hash/canonicalizer.rb', line 219

def webrisk_uri_escape(s)
  out = +''
  i = 0
  while i < s.length
    c = s[i]
    if c == '%' && s[i + 1] && s[i + 2] && s[(i + 1)..(i + 2)] =~ /^[0-9a-fA-F]{2}$/
      out << '%' << s[(i + 1)..(i + 2)].upcase
      i += 3
      next
    end
    out << escape_character(c.ord)
    i += 1
  end
  out
end