Class: Immunio::Template

Inherits:
Object
  • Object
show all
Defined in:
lib/immunio/plugins/action_view/template.rb

Overview

Renders templates by filtering them through Immunio’s hook handlers.

Constant Summary collapse

CHECKSUM_CACHE = 
Hash.new do |cache, template_id|
  template = ObjectSpace._id2ref(template_id)

  if template.respond_to?(:source) && !template.source.nil?
    finalizer = Immunio::Template.finalize_template(template_id)
    ObjectSpace.define_finalizer(template, finalizer)
    cache[template_id] = Digest::SHA1.hexdigest(template.source).freeze
  end
end
ENCODED_IMMUNIO_TOKENS_RE = 
Regexp.compile(/(?:{|%7b)immunio-(var|fragment)(?::|%3a)(\d+)(?::|%3a)([0-9a-f]{1,4})(?:}|%7d)(.*?)(?:{|%7b)(?:\/|%2f)immunio-\1(?::|%3a)\2(?::|%3a)\3(?:}|%7d)/i)

Instance Attribute Summary collapse

Class Method Summary collapse

Instance Method Summary collapse

Constructor Details

#initialize(template) ⇒ Template

Returns a new instance of Template.



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# File 'lib/immunio/plugins/action_view/template.rb', line 21

def initialize(template)
  @template = template
  @next_var_id = 0
  @next_template_id = 0
  @vars = {}
  @scheduled_fragments_writes = []
end

Instance Attribute Details

#vars ⇒ Object

Returns the value of attribute vars.



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# File 'lib/immunio/plugins/action_view/template.rb', line 19

def vars
  @vars
end

Class Method Details

.current ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 144

def current
  rendering_stack.last
end

.decode_immunio_tokens(rendered) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 195

def decode_immunio_tokens(rendered)
  # Look for URI or JS encoded immunio tokens in the rendering and decode them
  # WebConsole incompatibility: `rendered` can be of type `Mime::Type` Which
  # doesn't respond to `gsub!`.
  if rendered.respond_to?(:gsub!)
    was_html_safe = rendered.html_safe?
    was_frozen = rendered.frozen?

    if was_frozen
      # This is not an airtight solution. Object#dup does not copy methods
      # defined on the instance, and may be overridden by subclasses to do
      # things that would cause problems for us. But most likely there is no
      # problem with using dup. We can't use Object#clone because the clone
      # retains the frozen status of the original, preventing us from
      # modifying the string contents.
      rendered = rendered.dup
    end

    rendered.gsub! ENCODED_IMMUNIO_TOKENS_RE, "{immunio-\\1:\\2:\\3}\\4{/immunio-\\1:\\2:\\3}"

    rendered.instance_variable_set(:@html_safe, true) if was_html_safe
    rendered.freeze if was_frozen
  end

  rendered
end

.finalize_template(id) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 140

def finalize_template(id)
  proc { CHECKSUM_CACHE.delete(id) if CHECKSUM_CACHE.has_key?(id) }
end

.generate_render_var_code(code, escape) ⇒ Object

Generate code injected in templates to wrap everything inside ‘<%= … %>`.



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# File 'lib/immunio/plugins/action_view/template.rb', line 305

def generate_render_var_code(code, escape)
  template = Template.current
  if template
    template_id = template.next_template_id

    handler = template.instance_variable_get(:@template).handler
    handler_name = if handler.is_a? Class
                     handler.name
                   else
                     handler.class.name
                   end

    "(__immunio_result = (#{remove_comment(code)}); Immunio::Template.render_var(#{code.strip.inspect}, __immunio_result, #{template_id}, '#{template.template_sha}', __FILE__, __LINE__, #{!!escape}, #{template.is_text?}, '#{handler_name}'))"
  else
    code
  end
end

.get_nonce ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 156

def get_nonce
  rendering_stack.first.get_nonce
end

.mark_and_defer_fragment_write(*args) ⇒ Object

Save fragment info to the root template only



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# File 'lib/immunio/plugins/action_view/template.rb', line 161

def mark_and_defer_fragment_write(*args)
  rendering_stack.first.mark_and_defer_fragment_write(*args)
end

.mark_var(content, code, template_id, template_sha, file, line, escape, is_text, handler) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 222

def mark_var(content, code, template_id, template_sha, file, line, escape, is_text, handler)
  id = Template.next_var_id
  nonce = Template.get_nonce

  # NOTE: What happens here is pretty funky to preserve the html_safe SafeBuffer behaviour in ruby.
  # If escaped is true we directly concatenate the content between two SafeBuffers. This will cause
  # escaping if content is not itself a SafeBuffer.
  # Otherwise we explicitly convert to a string, and convert that to a SafeBuffer to ensure that
  # for instance no escaping is performed on the contents of a <%== %> Erubis interpolation.
  rendering =
    if escape && !is_text
      # explicitly convert (w/ escapes) and mark safe things that aren't String (SafeBuffer is_a String also)
      # `to_s` is used to render any object passed to a template.
      # It is called internally when appending to ActionView::OutputBuffer.
      # We force rendering to get the actual string.
      # This has no impact if `rendered` is already a string.
      content = content.to_s.html_safe unless content.is_a? String

      # As a failsafe, just return the content if it already contains our markers. This can occur when
      # a helper calls render partial to generate a component of a page. Both render calls are root level
      # templates from our perspective.
      if content =~ /\{immunio-var:\d+:#{nonce}\}/ then
        # don't add markers.
        Immunio.logger.debug {"WARNING: ActionView not marking interpolation which already contains markers: \"#{content}\""}
        return content
      end

      "{immunio-var:#{id}:#{nonce}}".html_safe + content + "{/immunio-var:#{id}:#{nonce}}".html_safe
    else
      content = "" if content.nil?

      # See comment above
      if (content.respond_to? :=~) &&
         (content =~ /\{immunio-var:\d+:#{nonce}\}/)
        # don't add markers.
        Immunio.logger.debug {"WARNING: ActionView not marking interpolation which already contains markers: \"#{content}\""}
        return content.html_safe
      end

      "{immunio-var:#{id}:#{nonce}}".html_safe + content.to_s.html_safe + "{/immunio-var:#{id}:#{nonce}}".html_safe
    end

  # If we got here, the interpolation has been wrapped in our markers and we
  # need to record send data about it to the hook
  Template.vars[id.to_s] = {
    template_sha: template_sha,
    template_id: template_id.to_s,
    nonce: nonce,
    code: wrap_code(code, handler, escape: escape),
    file: file,
    line: line
  }

  rendering
end

.next_var_id ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 148

def next_var_id
  rendering_stack.first.next_var_id
end

.remove_all_markers!(input) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 323

def remove_all_markers!(input)
  input.gsub!(/\{\/?immunio-(fragment|var):\d+:[a-zA-Z0-9]+\}/, "")
end

.remove_comment(code) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 292

def remove_comment(code)
  *, last_line = code.rpartition("\n")

  comment = Ripper.slice(last_line, "comment")

  if comment
    code = code.sub(Regexp.new(Regexp.escape(comment) + "\\Z"), "")
  end

  code
end

.render_var(code, rendered, template_id, template_sha, file, line, escape, is_text, handler) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 278

def render_var(code, rendered, template_id, template_sha, file, line, escape, is_text, handler)
  rendered = decode_immunio_tokens rendered

  if rendered.instance_variable_get("@__immunio_processed") then
    # Ignore buffers marked as __immunio_processed in render as these are full templates or partials
    return rendered
  elsif code =~ /yield( .*)?/
    # Ignore yielded blocks inside layouts
    return rendered
  end
  rendered = mark_var rendered, code, template_id, template_sha, file, line, escape, is_text, handler
  rendered.html_safe
end

.rendering_stack ⇒ Object

Stack of the templates currently being rendered.



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# File 'lib/immunio/plugins/action_view/template.rb', line 166

def rendering_stack
  Thread.current["immunio.rendering_stack"] ||= []
end

.vars ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 152

def vars
  rendering_stack.first.vars
end

.wrap_code(code, handler, options = {}) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 170

def wrap_code(code, handler, options = {})
  wrap_method = {
    'ActionView::Template::Handlers::ERB' => :wrap_code_for_erb,
    'Haml::Plugin' => :wrap_code_for_haml,
    'Slim::RailsTemplate' => :wrap_code_for_slim
  }[handler]

  send wrap_method, code, options
end

.wrap_code_for_erb(code, options) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 180

def wrap_code_for_erb(code, options)
  modifier = options[:escape] ? '=' : '=='
  "<%#{modifier} #{code} %>"
end

.wrap_code_for_haml(code, options) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 185

def wrap_code_for_haml(code, options)
  modifier = options[:escape] ? '=' : '!='
  "#{modifier} #{code}"
end

.wrap_code_for_slim(code, options) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 190

def wrap_code_for_slim(code, options)
  modifier = options[:escape] ? '=' : '=='
  "#{modifier} #{code}"
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 34

def ==(other)
  self.class === other && id == other.id
end

#get_nonce ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 59

def get_nonce
  # Generate a two byte CSRNG nonce to make our substitutions unpreictable
  # Why only 2 bytes? The nonce is per render, so the odds of guessing it are very low
  # and entropy is finite so we don't want to drain the random pool unnecessarily
  @nonce ||= SecureRandom.hex(2)
end

#id ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 29

def id
  (@template.respond_to?(:virtual_path) && @template.virtual_path) ||
    (@template.respond_to?(:source) && @template.source)
end

#is_text? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/immunio/plugins/action_view/template.rb', line 38

def is_text?
  @template.formats.first == :text
end

#mark_and_defer_fragment_write(key, content, options) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 66

def mark_and_defer_fragment_write(key, content, options)
  id = @scheduled_fragments_writes.size
  nonce = Template.get_nonce
  @scheduled_fragments_writes << [key, content, options]
  "{immunio-fragment:#{id}:#{nonce}}#{content}{/immunio-fragment:#{id}:#{nonce}}"
end

#next_template_id ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 53

def next_template_id
  id = @next_template_id
  @next_template_id += 1
  id
end

#next_var_id ⇒ Object

Generate the next var unique ID to be used in a template.



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# File 'lib/immunio/plugins/action_view/template.rb', line 47

def next_var_id
  id = @next_var_id
  @next_var_id += 1
  id
end

#render(context) ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 73

def render(context)
  load_source context
  # Don't handle templates with no source (inline text templates).
  unless has_source?
    rendered = yield
    rendered.instance_variable_set("@__immunio_processed", true) unless rendered.frozen?
    return rendered
  end

  begin
    root = true if rendering_stack.length == 0

    rendering_stack.push self
    # Calculate SHA1 of this template.
    template_sha
    Immunio.logger.debug {"ActionView rendering template with sha #{@template_sha}, root: #{root}"}
    rendered = yield
    rendered.instance_variable_set("@__immunio_processed", true) unless rendered.frozen?

    if root
      # This is the root template. Let ActionView render it, and then look
      # for XSS.

      # If the rendered result isn't a string, or a string-like, then let's
      # skip it for safety sake.
      unless rendered.respond_to? :to_str
        unless $__immunio_av_rendered_non_string
          Immunio.logger.warn { "ActionView rendered #{@template.inspect} to a non-string-like value: #{rendered.inspect}. This rendering will not be analyzed for XSS. Further warnings will be suppressed." }
          $__immunio_av_rendered_non_string = true
        end
        return rendered
      end

      rendered = rendered.to_str

      result = run_hook!("template_render_done", {
        content_type: Mime::Type.lookup_by_extension(@template.formats.first).to_s,
        rendered: rendered,
        vars: @vars
      })

      # We use the return value from the hook handler if present.
      rendered = result["rendered"] || rendered.dup

      remove_var_markers! rendered

      # If some fragments were marked to be cached, commit their content to cache.
      write_and_remove_fragments! context, rendered

      rendered.html_safe
    else
      # This is a partial template. Just render it.
      rendered
    end
  ensure
    top_template = rendering_stack.pop
    unless top_template == self
      raise Error, "Unexpected Immunio::Template on rendering stack. Expected #{id}, got #{top_template.try :id}."
    end
  end
end

#template_sha ⇒ Object 



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# File 'lib/immunio/plugins/action_view/template.rb', line 42

def template_sha
  CHECKSUM_CACHE[@template.object_id]
end