Class: Brakeman::CheckLinkToHref

Inherits:
CheckLinkTo show all
Defined in:
lib/brakeman/checks/check_link_to_href.rb

Overview

Checks for calls to link_to which pass in potentially hazardous data to the second argument. While this argument must be html_safe to not break the html, it must also be url safe as determined by calling a :url_safe_method. This prevents attacks such as javascript:evil() or data:<encoded XSS> which is html_safe, but not safe as an href Props to Nick Green for the idea.

Constant Summary collapse

CHECK_INSIDE_METHODS = 
[:url_for, :h, :sanitize]

Constants inherited from CheckCrossSiteScripting

Brakeman::CheckCrossSiteScripting::CGI, Brakeman::CheckCrossSiteScripting::FORM_BUILDER, Brakeman::CheckCrossSiteScripting::HAML_HELPERS, Brakeman::CheckCrossSiteScripting::IGNORE_LIKE, Brakeman::CheckCrossSiteScripting::IGNORE_MODEL_METHODS, Brakeman::CheckCrossSiteScripting::MODEL_METHODS, Brakeman::CheckCrossSiteScripting::URI, Brakeman::CheckCrossSiteScripting::XML_HELPER

Constants inherited from BaseCheck

BaseCheck::CONFIDENCE

Constants included from Util

Util::ALL_COOKIES, Util::ALL_PARAMETERS, Util::COOKIES, Util::COOKIES_SEXP, Util::DIR_CONST, Util::LITERALS, Util::PARAMETERS, Util::PARAMS_SEXP, Util::PATH_PARAMETERS, Util::QUERY_PARAMETERS, Util::REQUEST_COOKIES, Util::REQUEST_ENV, Util::REQUEST_PARAMETERS, Util::REQUEST_PARAMS, Util::REQUEST_REQUEST_PARAMETERS, Util::SAFE_LITERAL, Util::SESSION, Util::SESSION_SEXP, Util::SIMPLE_LITERALS

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 CheckLinkTo

#actually_process_call, #check_argument, #check_matched, #check_method, #check_user_input, #process_call, #warn_xss

Methods inherited from CheckCrossSiteScripting

#actually_process_call, #cgi_escaped?, #check_for_immediate_xss, #form_builder_method?, #haml_escaped?, #html_safe_call?, #ignored_model_method?, #initialize, #likely_model_attribute?, #process_call, #process_case, #process_cookies, #process_dstr, #process_escaped_output, #process_format, #process_format_escaped, #process_if, #process_output, #process_params, #process_render, #raw_call?, #safe_input_attribute?, #setup, #xml_escaped?

Methods inherited from BaseCheck

#add_result, inherited, #initialize, #process_array, #process_call, #process_cookies, #process_default, #process_dstr, #process_if, #process_params

Methods included from Messages

#msg, #msg_code, #msg_cve, #msg_file, #msg_input, #msg_lit, #msg_plain, #msg_version

Methods included from Util

#all_literals?, #array?, #block?, #call?, #camelize, #class_name, #constant?, #contains_class?, #cookies?, #dir_glob?, #false?, #hash?, #hash_access, #hash_insert, #hash_iterate, #hash_values, #integer?, #kwsplat?, #literal?, #make_call, #node_type?, #number?, #params?, #pluralize, #rails_version, #recurse_check?, #regexp?, #remove_kwsplat, #request_headers?, #request_value?, #result?, #safe_literal, #safe_literal?, #safe_literal_target?, #set_env_defaults, #sexp?, #simple_literal?, #string?, #string_interp?, #symbol?, #template_path_to_name, #true?, #underscore

Methods included from ProcessorHelper

#current_file, #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::CheckCrossSiteScripting

Instance Method Details

#call_on_params?(exp) ⇒ Boolean

Returns:

  • (Boolean) 


146
147
148
149
150
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 146

def call_on_params? exp
  call? exp and
  params? exp.target and
  exp.method != :[]
end

#check_argument?(url_arg) ⇒ Boolean

Returns:

  • (Boolean) 


81
82
83
84
85
86
87
88
89
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 81

def check_argument? url_arg
  return unless call? url_arg

  target = url_arg.target
  method = url_arg.method

  CHECK_INSIDE_METHODS.include? method or
    cgi_escaped? target, method
end

#decorated_model?(method) ⇒ Boolean

Returns:

  • (Boolean) 


128
129
130
131
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 128

def decorated_model? method
  tracker.config.has_gem? :draper and
    method == :decorate
end

#ignore_call?(target, method) ⇒ Boolean

Returns:

  • (Boolean) 


124
125
126
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 124

def ignore_call? target, method
  decorated_model? method or super
end

#ignore_interpolation?(arg, suspect) ⇒ Boolean

Ignore situations where the href is an interpolated string with something before the user input

Returns:

  • (Boolean) 


108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 108

def ignore_interpolation? arg, suspect
  return unless string_interp? arg
  return true unless arg[1].chomp.empty? # plain string before interpolation

  first_interp = arg.find_nodes(:evstr).first
  return unless first_interp

  first_interp[1].deep_each do |e|
    if suspect == e
      return false
    end
  end

  true
end

#ignore_model_call?(url_arg, exp) ⇒ Boolean

Returns:

  • (Boolean) 


91
92
93
94
95
96
97
98
99
100
101
102
103
104
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 91

def ignore_model_call? url_arg, exp
  return true unless call? exp

  target = exp.target
  method = exp.method

  return true unless model_find_call? target

  return true unless method.to_s =~ /url|uri|link|page|site/

  ignore_call? target, method or
    IGNORE_MODEL_METHODS.include? method or
    ignore_interpolation? url_arg, exp
end

#ignored_method?(target, method) ⇒ Boolean

Returns:

  • (Boolean) 


133
134
135
136
137
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 133

def ignored_method? target, method
  @ignore_methods.include? method or
    method.to_s =~ /_path$/ or
    (target.nil? and method.to_s =~ /_url$/)
end

#model_find_call?(exp) ⇒ Boolean

Returns:

  • (Boolean) 


139
140
141
142
143
144
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 139

def model_find_call? exp
  return unless call? exp

  MODEL_METHODS.include? exp.method or
    exp.method.to_s =~ /^find_by_/
end

#process_result(result) ⇒ Object 



32
33
34
35
36
37
38
39
40
41
42
43
44
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
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 32

def process_result result
  call = result[:call]
  @matched = false

  url_arg = if result[:block]
              process call.first_arg
            else
              process call.second_arg
            end

  if check_argument? url_arg
    url_arg = url_arg.first_arg
  end

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

  if input = has_immediate_user_input?(url_arg)
    message = msg("Unsafe ", msg_input(input), " in ", msg_code("link_to"), " href")

    unless duplicate? result or call_on_params? url_arg or ignore_interpolation? url_arg, input.match
      add_result result
      warn :result => result,
        :warning_type => "Cross-Site Scripting",
        :warning_code => :xss_link_to_href,
        :message => message,
        :user_input => input,
        :confidence => :high,
        :link_path => "link_to_href",
        :cwe_id => [79]
    end
  elsif not tracker.options[:ignore_model_output] and input = has_immediate_model?(url_arg)
    return if ignore_model_call? url_arg, input or duplicate? result
    add_result result

    message = msg("Potentially unsafe model attribute in ", msg_code("link_to"), " href")

    warn :result => result,
      :warning_type => "Cross-Site Scripting",
      :warning_code => :xss_link_to_href,
      :message => message,
      :user_input => input,
      :confidence => :weak,
      :link_path => "link_to_href",
      :cwe_id => [79]
  end
end

#run_check ⇒ Object 



14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 14

def run_check
  @ignore_methods = Set[:button_to, :check_box,
                         :field_field, :fields_for, :hidden_field,
                         :hidden_field, :hidden_field_tag, :image_tag, :label,
                         :mail_to, :polymorphic_url, :radio_button, :select, :slice,
                         :submit_tag, :text_area, :text_field,
                         :text_field_tag, :url_encode, :u,
                         :will_paginate].merge(tracker.options[:url_safe_methods] || [])

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

  methods = tracker.find_call :target => false, :method => :link_to
  methods.each do |call|
    process_result call
  end
end