require 'erb' require 'active_support/core_ext/kernel/singleton_class' class ERB module Util HTML_ESCAPE = { '&' => '&', '>' => '>', '<' => '<', '"' => '"', "'" => ''' } JSON_ESCAPE = { '&' => '\u0026', '>' => '\u003e', '<' => '\u003c', "\u2028" => '\u2028', "\u2029" => '\u2029' } HTML_ESCAPE_REGEXP = /[&"'><]/ HTML_ESCAPE_ONCE_REGEXP = /["><']|&(?!([a-zA-Z]+|(#\d+));)/ JSON_ESCAPE_REGEXP = /[\u2028\u2029&><]/u # A utility method for escaping HTML tag characters. # This method is also aliased as h. # # In your ERB templates, use this method to escape any unsafe content. For example: # <%=h @person.name %> # # puts html_escape('is a > 0 & a < 10?') # # => is a > 0 & a < 10? def html_escape(s) s = s.to_s if s.html_safe? s else s.gsub(HTML_ESCAPE_REGEXP, HTML_ESCAPE).html_safe end end # Aliasing twice issues a warning "discarding old...". Remove first to avoid it. remove_method(:h) alias h html_escape module_function :h singleton_class.send(:remove_method, :html_escape) module_function :html_escape # A utility method for escaping HTML without affecting existing escaped entities. # # html_escape_once('1 < 2 & 3') # # => "1 < 2 & 3" # # html_escape_once('<< Accept & Checkout') # # => "<< Accept & Checkout" def html_escape_once(s) result = s.to_s.gsub(HTML_ESCAPE_ONCE_REGEXP, HTML_ESCAPE) s.html_safe? ? result.html_safe : result end module_function :html_escape_once # A utility method for escaping HTML entities in JSON strings. Specifically, the # &, > and < characters are replaced with their equivalent unicode escaped form - # \u0026, \u003e, and \u003c. The Unicode sequences \u2028 and \u2029 are also # escaped as they are treated as newline characters in some JavaScript engines. # These sequences have identical meaning as the original characters inside the # context of a JSON string, so assuming the input is a valid and well-formed # JSON value, the output will have equivalent meaning when parsed: # # json = JSON.generate({ name: ""}) # # => "{\"name\":\"\"}" # # json_escape(json) # # => "{\"name\":\"\\u003C/script\\u003E\\u003Cscript\\u003Ealert('PWNED!!!')\\u003C/script\\u003E\"}" # # JSON.parse(json) == JSON.parse(json_escape(json)) # # => true # # The intended use case for this method is to escape JSON strings before including # them inside a script tag to avoid XSS vulnerability: # # # # It is necessary to +raw+ the result of +json_escape+, so that quotation marks # don't get converted to " entities. +json_escape+ doesn't # automatically flag the result as HTML safe, since the raw value is unsafe to # use inside HTML attributes. # # If you need to output JSON elsewhere in your HTML, you can just do something # like this, as any unsafe characters (including quotation marks) will be # automatically escaped for you: # #
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# # WARNING: this helper only works with valid JSON. Using this on non-JSON values # will open up serious XSS vulnerabilities. For example, if you replace the # +current_user.to_json+ in the example above with user input instead, the browser # will happily eval() that string as JavaScript. # # The escaping performed in this method is identical to those performed in the # Active Support JSON encoder when +ActiveSupport.escape_html_entities_in_json+ is # set to true. Because this transformation is idempotent, this helper can be # applied even if +ActiveSupport.escape_html_entities_in_json+ is already true. # # Therefore, when you are unsure if +ActiveSupport.escape_html_entities_in_json+ # is enabled, or if you are unsure where your JSON string originated from, it # is recommended that you always apply this helper (other libraries, such as the # JSON gem, do not provide this kind of protection by default; also some gems # might override +to_json+ to bypass Active Support's encoder). def json_escape(s) result = s.to_s.gsub(JSON_ESCAPE_REGEXP, JSON_ESCAPE) s.html_safe? ? result.html_safe : result end module_function :json_escape end end class Object def html_safe? false end end class Numeric def html_safe? true end end module ActiveSupport #:nodoc: class SafeBuffer < String UNSAFE_STRING_METHODS = %w( capitalize chomp chop delete downcase gsub lstrip next reverse rstrip slice squeeze strip sub succ swapcase tr tr_s upcase prepend ) alias_method :original_concat, :concat private :original_concat class SafeConcatError < StandardError def initialize super 'Could not concatenate to the buffer because it is not html safe.' end end def [](*args) if args.size < 2 super else if html_safe? new_safe_buffer = super new_safe_buffer.instance_eval { @html_safe = true } new_safe_buffer else to_str[*args] end end end def safe_concat(value) raise SafeConcatError unless html_safe? original_concat(value) end def initialize(*) @html_safe = true super end def initialize_copy(other) super @html_safe = other.html_safe? end def clone_empty self[0, 0] end def concat(value) if !html_safe? || value.html_safe? super(value) else super(ERB::Util.h(value)) end end alias << concat def +(other) dup.concat(other) end def %(args) case args when Hash escaped_args = Hash[args.map { |k,arg| [k, html_escape_interpolated_argument(arg)] }] else escaped_args = Array(args).map { |arg| html_escape_interpolated_argument(arg) } end self.class.new(super(escaped_args)) end def html_safe? defined?(@html_safe) && @html_safe end def to_s self end def to_param to_str end def encode_with(coder) coder.represent_scalar nil, to_str end UNSAFE_STRING_METHODS.each do |unsafe_method| if unsafe_method.respond_to?(unsafe_method) class_eval <<-EOT, __FILE__, __LINE__ + 1 def #{unsafe_method}(*args, &block) # def capitalize(*args, &block) to_str.#{unsafe_method}(*args, &block) # to_str.capitalize(*args, &block) end # end def #{unsafe_method}!(*args) # def capitalize!(*args) @html_safe = false # @html_safe = false super # super end # end EOT end end private def html_escape_interpolated_argument(arg) (!html_safe? || arg.html_safe?) ? arg : ERB::Util.h(arg) end end end class String def html_safe ActiveSupport::SafeBuffer.new(self) end end