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

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

#array?, #block?, #call?, #camelize, #class_name, #constant?, #contains_class?, #cookies?, #dir_glob?, #false?, #hash?, #hash_access, #hash_insert, #hash_iterate, #integer?, #kwsplat?, #literal?, #make_call, #node_type?, #number?, #params?, #pluralize, #rails_version, #regexp?, #remove_kwsplat, #request_env?, #request_value?, #result?, #safe_literal, #safe_literal?, #safe_literal_target?, #set_env_defaults, #sexp?, #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)

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# File 'lib/brakeman/checks/check_link_to_href.rb', line 144

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

#check_argument?(url_arg) ⇒ Boolean

Returns:

  • (Boolean)

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# File 'lib/brakeman/checks/check_link_to_href.rb', line 79

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)

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

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

#ignore_call?(target, method) ⇒ Boolean

Returns:

  • (Boolean)

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# File 'lib/brakeman/checks/check_link_to_href.rb', line 122

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)

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# File 'lib/brakeman/checks/check_link_to_href.rb', line 106

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)

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# File 'lib/brakeman/checks/check_link_to_href.rb', line 89

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)

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

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)

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# File 'lib/brakeman/checks/check_link_to_href.rb', line 137

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


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# 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"
    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"
  end
end

#run_checkObject


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# 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