Class: Immunio::Template

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

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.rb', line 23

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.rb', line 21

def vars
  @vars
end

Class Method Details

.current ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 271

def self.current
  rendering_stack.last
end

.finalize_template(id) ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 17

def self.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.rb', line 241

def self.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 = (#{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.rb', line 283

def self.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.rb', line 288

def self.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.rb', line 116

def self.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 =~ /\{immunio-var:\d+:#{nonce}\}/ then
      # 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.rb', line 275

def self.next_var_id
  rendering_stack.first.next_var_id
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.rb', line 259

def self.render_var(code, rendered, template_id, template_sha, file, line, escape, is_text, handler)
  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

.vars ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 279

def self.vars
  rendering_stack.first.vars
end

Instance Method Details

#==(other) ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 35

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

#compiled? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/immunio/plugins/action_view.rb', line 92

def compiled?
  @template.instance_variable_get :@compiled
end

#get_nonce ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 109

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

#has_source? ⇒ Boolean

Returns:

  • (Boolean) 


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# File 'lib/immunio/plugins/action_view.rb', line 39

def has_source?
  @template.respond_to?(:source) && !@template.source.nil?
end

#id ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 31

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.rb', line 43

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

#load_source(context) ⇒ Object 



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

def load_source(context)
  return if !@template.respond_to?(:source) || !@template.source.nil?

  # @template is a virtual template that doesn't contain the source. We need
  # to try to load the source. But, the virtual template doesn't know the
  # original format of the source template file.
  #
  # First, try to load it using the Rails defaults (usually "html" and
  # "txt"). If that doesn't work, try to use the original format from the
  # virtual template.
  #
  # Though one might think the format from the virtual template would always
  # work, unfortunately the format from the template refers to the "type" of
  # the template, which may or may not be the same as the format of the
  # lookup context, which specifies the file extension of the template. Ugh,
  # naming... For example, the lookup context format may be "txt" while the
  # template format is "text".
  #
  # Astute readers may note that there's the possibility the template
  # extension is not in the Rails default list of lookup formats, and also
  # does not match the template type. We are just going to leave that for
  # another day, and hope that day never comes...
  begin
    refreshed = Immunio::IOHooks.paused { @template.refresh(context) }
  rescue
    begin
      old_formats = context.lookup_context.formats
      context.lookup_context.formats = @template.formats
      refreshed = Immunio::IOHooks.paused { @template.refresh(context) }
    rescue
      Immunio.logger.warn { "Failed to refresh template source from #{@template} using contexts #{old_formats} and #{@template.formats}" }
    ensure
      context.lookup_context.formats = old_formats
    end
  end

  return if refreshed.nil?

  @template.instance_variable_set :@source, refreshed.source
end

#mark_and_defer_fragment_write(key, content, options) ⇒ Object 



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# File 'lib/immunio/plugins/action_view.rb', line 171

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.rb', line 103

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.rb', line 97

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.rb', line 178

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.fetch("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.rb', line 88

def template_sha
  CHECKSUM_CACHE[@template.object_id]
end