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

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_PARAMETERS, Util::COOKIES, Util::COOKIES_SEXP, Util::PARAMETERS, Util::PARAMS_SEXP, Util::PATH_PARAMETERS, Util::QUERY_PARAMETERS, 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 CheckLinkTo

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

Methods inherited from CheckCrossSiteScripting

#actually_process_call, #boolean_method?, #cgi_escaped?, #check_for_immediate_xss, #form_builder_method?, #haml_escaped?, #html_safe_call?, #ignored_model_method?, #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_call, #process_cookies, #process_default, #process_dstr, #process_if, #process_params

Methods included from Util

#array?, #block?, #call?, #camelize, #class_name, #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

#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

#decorated_model?(method) ⇒ Boolean

Returns:

  • (Boolean) 


98
99
100
101
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 98

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

#ignore_call?(target, method) ⇒ Boolean

Returns:

  • (Boolean) 


94
95
96
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 94

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

#ignored_method?(target, method) ⇒ Boolean

Returns:

  • (Boolean) 


103
104
105
106
107
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 103

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) 


109
110
111
112
113
114
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 109

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
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
 
# File 'lib/brakeman/checks/check_link_to_href.rb', line 32

def process_result result
  #Have to make a copy of this, otherwise it will be changed to
  #an ignored method call by the code above.
  call = result[:call] = result[:call].dup
  @matched = false
  url_arg = process call.second_arg

  #Ignore situations where the href is an interpolated string
  #with something before the user input
  return if string_interp?(url_arg) && !url_arg[1].chomp.empty?

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

  if input = has_immediate_user_input?(url_arg)
    message = "Unsafe #{friendly_type_of input} in link_to href"

    unless duplicate? result
      add_result result
      warn :result => result,
        :warning_type => "Cross Site Scripting", 
        :warning_code => :xss_link_to_href,
        :message => message,
        :user_input => input,
        :confidence => CONFIDENCE[:high],
        :link_path => "link_to_href"
    end
  elsif has_immediate_model? url_arg or model_find_call? url_arg

    # Decided NOT warn on models.  polymorphic_path is called it a model is 
    # passed to link_to (which passes it to url_for)

  elsif array? url_arg
    # Just like models, polymorphic path/url is called if the argument is 
    # an array      

  elsif hash? url_arg

    # url_for uses the key/values pretty carefully and I don't see a risk.
    # IF you have default routes AND you accept user input for :controller
    # and :only_path, then MAYBE you could trigger a javascript:/data: 
    # attack. 

  elsif @matched
    if @matched.type == :model and not tracker.options[:ignore_model_output]
      message = "Unsafe model attribute in link_to href"
    elsif @matched.type == :params
      message = "Unsafe parameter value in link_to href"
    end

    if message and not duplicate? result
      add_result result
      warn :result => result, 
        :warning_type => "Cross Site Scripting", 
        :warning_code => :xss_link_to_href,
        :message => message,
        :user_input => @matched,
        :confidence => CONFIDENCE[:med],
        :link_path => "link_to_href"
    end
  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,
                         :submit_tag, :text_area, :text_field,
                         :text_field_tag, :url_encode, :url_for,
                         :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