Class: Brakeman::CheckCrossSiteScripting

Inherits:
BaseCheck show all
Defined in:
lib/brakeman/checks/check_cross_site_scripting.rb

Overview

This check looks for unescaped output in templates which contains parameters or model attributes.

For example:

<%= User.find(:id).name %> <%= params %>

Constant Summary collapse

IGNORE_MODEL_METHODS =

Model methods which are known to be harmless

Set[:average, :count, :maximum, :minimum, :sum, :id]
MODEL_METHODS =
Set[:all, :find, :first, :last, :new]
IGNORE_LIKE =
/^link_to_|(_path|_tag|_url)$/
HAML_HELPERS =
Sexp.new(:colon2, Sexp.new(:const, :Haml), :Helpers)
XML_HELPER =
Sexp.new(:colon2, Sexp.new(:const, :Erubis), :XmlHelper)
URI =
Sexp.new(:const, :URI)
CGI =
Sexp.new(:const, :CGI)
FORM_BUILDER =
Sexp.new(:call, Sexp.new(:const, :FormBuilder), :new)

Constants inherited from BaseCheck

BaseCheck::CONFIDENCE

Constants included from Util

Util::ALL_COOKIES, Util::ALL_PARAMETERS, Util::COOKIES, Util::COOKIES_SEXP, Util::PARAMETERS, Util::PARAMS_SEXP, Util::PATH_PARAMETERS, Util::QUERY_PARAMETERS, Util::REQUEST_COOKIES, Util::REQUEST_ENV, Util::REQUEST_PARAMETERS, Util::REQUEST_PARAMS, Util::SESSION, Util::SESSION_SEXP

Constants inherited from SexpProcessor

SexpProcessor::VERSION

Instance Attribute Summary

Attributes inherited from BaseCheck

#tracker, #warnings

Attributes inherited from SexpProcessor

#context, #env, #expected

Instance Method Summary collapse

Methods inherited from BaseCheck

#add_result, inherited, #initialize, #process_default

Methods included from Util

#array?, #block?, #call?, #camelize, #class_name, #constant?, #contains_class?, #context_for, #cookies?, #false?, #file_by_name, #file_for, #github_url, #hash?, #hash_access, #hash_insert, #hash_iterate, #integer?, #make_call, #node_type?, #number?, #params?, #pluralize, #rails_version, #regexp?, #relative_path, #request_env?, #request_value?, #result?, #set_env_defaults, #sexp?, #string?, #string_interp?, #symbol?, #table_to_csv, #template_path_to_name, #true?, #truncate_table, #underscore

Methods included from ProcessorHelper

#current_file_name, #process_all, #process_all!, #process_call_args, #process_call_defn?, #process_class, #process_module

Methods inherited from SexpProcessor

#in_context, #initialize, #process, processors, #scope

Constructor Details

This class inherits a constructor from Brakeman::BaseCheck

Instance Method Details

#actually_process_call(exp) ⇒ Object



208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 208

def actually_process_call exp
  return if @matched
  target = exp.target
  if sexp? target
    target = process target
  end

  method = exp.method

  #Ignore safe items
  if ignore_call? target, method
    @matched = false
  elsif sexp? target and model_name? target[1] #TODO: use method call?
    @matched = Match.new(:model, exp)
  elsif cookies? exp
    @matched = Match.new(:cookies, exp)
  elsif @inspect_arguments and params? exp
    @matched = Match.new(:params, exp)
  elsif @inspect_arguments
    process_call_args exp
  end
end

#cgi_escaped?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


361
362
363
364
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 361

def cgi_escaped? target, method
  method == :escape and
  (target == URI or target == CGI)
end

#check_for_immediate_xss(exp) ⇒ Object



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
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 55

def check_for_immediate_xss exp
  return :duplicate if duplicate? exp

  if exp.node_type == :output
    out = exp.value
  elsif exp.node_type == :escaped_output
    if raw_call? exp
      out = exp.value.first_arg
    elsif html_safe_call? exp
      out = exp.value.target
    end
  end

  return if call? out and ignore_call? out.target, out.method

  if input = has_immediate_user_input?(out)
    add_result exp

    message = "Unescaped #{friendly_type_of input}"

    warn :template => @current_template,
      :warning_type => "Cross-Site Scripting",
      :warning_code => :cross_site_scripting,
      :message => message,
      :code => input.match,
      :confidence => :high

  elsif not tracker.options[:ignore_model_output] and match = has_immediate_model?(out)
    method = if call? match
               match.method
             else
               nil
             end

    unless IGNORE_MODEL_METHODS.include? method
      add_result exp

      if likely_model_attribute? match
        confidence = :high
      else
        confidence = :medium
      end

      message = "Unescaped model attribute"
      link_path = "cross_site_scripting"
      warning_code = :cross_site_scripting

      if node_type?(out, :call, :safe_call, :attrasgn, :safe_attrasgn) && out.method == :to_json
        message += " in JSON hash"
        link_path += "_to_json"
        warning_code = :xss_to_json
      end

      warn :template => @current_template,
        :warning_type => "Cross-Site Scripting",
        :warning_code => warning_code,
        :message => message,
        :code => match,
        :confidence => confidence,
        :link_path => link_path
    end

  else
    false
  end
end

#form_builder_method?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


374
375
376
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 374

def form_builder_method? target, method
  target == FORM_BUILDER and @ignore_methods.include? method
end

#haml_escaped?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


366
367
368
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 366

def haml_escaped? target, method
  method == :html_escape and target == HAML_HELPERS
end

#html_safe_call?(exp) ⇒ Boolean

Returns:

  • (Boolean)


336
337
338
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 336

def html_safe_call? exp
  call? exp.value and exp.value.method == :html_safe
end

#ignore_call?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


340
341
342
343
344
345
346
347
348
349
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 340

def ignore_call? target, method
  ignored_method?(target, method) or
  safe_input_attribute?(target, method) or
  ignored_model_method?(target, method) or
  form_builder_method?(target, method) or
  haml_escaped?(target, method) or
  boolean_method?(method) or
  cgi_escaped?(target, method) or
  xml_escaped?(target, method)
end

#ignored_method?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


357
358
359
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 357

def ignored_method? target, method
  @ignore_methods.include? method or method.to_s =~ IGNORE_LIKE
end

#ignored_model_method?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


351
352
353
354
355
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 351

def ignored_model_method? target, method
  ((@matched and @matched.type == :model) or
     model_name? target) and
     IGNORE_MODEL_METHODS.include? method
end

#likely_model_attribute?(exp) ⇒ Boolean

Call already involves a model, but might not be acting on a record

Returns:

  • (Boolean)


123
124
125
126
127
128
129
130
131
132
133
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 123

def likely_model_attribute? exp
  return false unless call? exp

  method = exp.method

  if MODEL_METHODS.include? method or method.to_s.start_with? "find_by_"
    true
  else
    likely_model_attribute? exp.target
  end
end

#process_call(exp) ⇒ Object

Check a call for user input

Since we want to report an entire call and not just part of one, use @mark to mark when a call is started. Any dangerous values inside will then report the entire call chain.



161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 161

def process_call exp
  if @mark
    actually_process_call exp
  else
    @mark = true
    actually_process_call exp
    message = nil

    if @matched
      unless @matched.type and tracker.options[:ignore_model_output]
        message = "Unescaped #{friendly_type_of @matched}"
      end

      if message and not duplicate? exp
        add_result exp

        link_path = "cross_site_scripting"
        warning_code = :cross_site_scripting

        if @known_dangerous.include? exp.method
          confidence = :high
          if exp.method == :to_json
            message += " in JSON hash"
            link_path += "_to_json"
            warning_code = :xss_to_json
          end
        else
          confidence = :weak
        end

        warn :template => @current_template,
          :warning_type => "Cross-Site Scripting",
          :warning_code => warning_code,
          :message => message,
          :code => exp,
          :user_input => @matched,
          :confidence => confidence,
          :link_path => link_path
      end
    end

    @mark = @matched = false
  end

  exp
end

#process_case(exp) ⇒ Object



270
271
272
273
274
275
276
277
278
279
280
281
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 270

def process_case exp
  #Ignore user input in case value
  #TODO: also ignore when values

  current = 2
  while current < exp.length
    process exp[current] if exp[current]
    current += 1
  end

  exp
end

#process_cookies(exp) ⇒ Object

Note that cookies have been found



238
239
240
241
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 238

def process_cookies exp
  @matched = Match.new(:cookies, exp)
  exp
end

#process_dstr(exp) ⇒ Object

Process as default



249
250
251
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 249

def process_dstr exp
  process_default exp
end

#process_escaped_output(exp) ⇒ Object

Look for calls to raw() Otherwise, ignore



142
143
144
145
146
147
148
149
150
151
152
153
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 142

def process_escaped_output exp
  unless check_for_immediate_xss exp
    if not duplicate? exp
      if raw_call? exp
        process exp.value.first_arg
      elsif html_safe_call? exp
        process exp.value.target
      end
    end
  end
  exp
end

#process_format(exp) ⇒ Object

Process as default



254
255
256
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 254

def process_format exp
  process_default exp
end

#process_format_escaped(exp) ⇒ Object

Ignore output HTML escaped via HAML



259
260
261
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 259

def process_format_escaped exp
  exp
end

#process_if(exp) ⇒ Object

Ignore condition in if Sexp



264
265
266
267
268
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 264

def process_if exp
  process exp.then_clause if sexp? exp.then_clause
  process exp.else_clause if sexp? exp.else_clause
  exp
end

#process_output(exp) ⇒ Object

Process an output Sexp



136
137
138
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 136

def process_output exp
  process exp.value.dup
end

#process_params(exp) ⇒ Object

Note that params have been found



232
233
234
235
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 232

def process_params exp
  @matched = Match.new(:params, exp)
  exp
end

#process_render(exp) ⇒ Object

Ignore calls to render



244
245
246
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 244

def process_render exp
  exp
end

#raw_call?(exp) ⇒ Boolean

Returns:

  • (Boolean)


332
333
334
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 332

def raw_call? exp
  exp.value.node_type == :call and exp.value.method == :raw
end

#run_checkObject

Run check



37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 37

def run_check
  setup

  tracker.each_template do |name, template|
    Brakeman.debug "Checking #{name} for XSS"

    @current_template = template

    template.each_output do |out|
      unless check_for_immediate_xss out
        @matched = false
        @mark = false
        process out
      end
    end
  end
end

#safe_input_attribute?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


378
379
380
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 378

def safe_input_attribute? target, method
  target and always_safe_method? method
end

#setupObject



283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 283

def setup
  @ignore_methods = Set[:==, :!=, :button_to, :check_box, :content_tag, :escapeHTML, :escape_once,
                         :field_field, :fields_for, :h, :hidden_field,
                         :hidden_field, :hidden_field_tag, :image_tag, :label,
                         :link_to, :mail_to, :radio_button, :select,
                         :submit_tag, :text_area, :text_field,
                         :text_field_tag, :url_encode, :u, :url_for,
                         :will_paginate].merge tracker.options[:safe_methods]

  @models = tracker.models.keys
  @inspect_arguments = tracker.options[:check_arguments]

  @known_dangerous = Set[:truncate, :concat]

  if version_between? "2.0.0", "3.0.5"
    @known_dangerous << :auto_link
  elsif version_between? "3.0.6", "3.0.99"
    @ignore_methods << :auto_link
  end

  if version_between? "2.0.0", "2.3.14" or tracker.config.gem_version(:'rails-html-sanitizer') == '1.0.2'
    @known_dangerous << :strip_tags
  end

  if tracker.config.has_gem? :'rails-html-sanitizer' and
     version_between? "1.0.0", "1.0.2", tracker.config.gem_version(:'rails-html-sanitizer')

    @known_dangerous << :sanitize
  end

  json_escape_on = false
  initializers = tracker.check_initializers :ActiveSupport, :escape_html_entities_in_json=
  initializers.each {|result| json_escape_on = true?(result.call.first_arg) }

  if tracker.config.escape_html_entities_in_json?
      json_escape_on = true
  elsif version_between? "4.0.0", "9.9.9"
    json_escape_on = true
  end

  if !json_escape_on or version_between? "0.0.0", "2.0.99"
    @known_dangerous << :to_json
    Brakeman.debug("Automatic to_json escaping not enabled, consider to_json dangerous")
  else
    @safe_input_attributes << :to_json
    Brakeman.debug("Automatic to_json escaping is enabled.")
  end
end

#xml_escaped?(target, method) ⇒ Boolean

Returns:

  • (Boolean)


370
371
372
# File 'lib/brakeman/checks/check_cross_site_scripting.rb', line 370

def xml_escaped? target, method
  method == :escape_xml and target == XML_HELPER
end