Class: Contrast::Agent::Assess::Policy::Propagator::Buffer

Inherits:
Base
  • Object
show all
Defined in:
lib/contrast/agent/assess/policy/propagator/buffer.rb

Overview

Propagation that results in all the tags of the source being applied to the target at the point of insertion. The target’s preexisting tags are shifted to account for this insertion.

Class Method Summary collapse

Methods inherited from Base

find_source, propagate, tracked_value?

Class Method Details

.buffer_keep_splat(propagation_node, preshift, ret) ⇒ Object

This method will implement both KEEP and SPLAT actions.

Parameters:



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# File 'lib/contrast/agent/assess/policy/propagator/buffer.rb', line 64

def buffer_keep_splat propagation_node, preshift, ret
  # If IO::Buffer gets duplicated the dup buffer is not allocated,
  # it's empty, So a way of doing it is to use the original object
  # itself. The class is included in the preshift's UNDUPLICABLE_MODULES.
  return unless preshift.object
  # We need the return in both propagation cases. So this propagation is
  # applied in the Contrast::Utils::Patching::PatchUtils.apply_post_patch.
  # we use this for the IO::Buffer#get_value and it requires 2 args always.
  return unless ret || Contrast::Agent::Assess::Tracker.tracked?(preshift.object)

  if preshift.args[1] == 0 # rubocop:disable Style/NumericPredicate
    # KEEP
    Contrast::Agent::Assess::Policy::Propagator::Keep.propagate(propagation_node, preshift, ret)
  else
    # SPLAT
    Contrast::Agent::Assess::Policy::Propagator::Splat.propagate(propagation_node, preshift, ret)
  end
end

.propagate_insert(propagation_node, preshift, target) ⇒ Object

For the source, append its tags to the target. Once the tag is applied, shift it to the location of the insert Unlike additive propagation, this currently only supports one source We assume that insert changes the preshift target



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# File 'lib/contrast/agent/assess/policy/propagator/buffer.rb', line 20

def propagate_insert propagation_node, preshift, target
  return unless (properties = Contrast::Agent::Assess::Tracker.properties!(target))

  source = find_source(propagation_node.sources[0], preshift)

  patcher_target = propagation_node.targets[0]
  preshift_target = case patcher_target
                    when Contrast::Utils::ObjectShare::OBJECT_KEY
                      preshift.object
                    else
                      # this is hardly reached b/c insert supports only one source
                      # changed to second argument: string.insert[idx, string_to_insert]
                      # previously was args[int] => produces exception
                      preshift.args[1]
                    end

  # in case of situations, where buffer is initialized with X size and it's not fully
  preshift_target = preshift_target.get_string
  target = target.get_string
  # Find the first difference between the source to which
  # we inserted and the result. That is the insertion
  # point on which all tags need to be adjusted
  # If the insertion point is the end of the string, preshift length is returned
  # https://stackoverflow.com/questions/31714522/find-the-first-differing-character-between-two-strings-in-ruby
  insert_point = (0...preshift_target.length).find do |i|
    preshift_target[i] != target[i]
  end || preshift_target.length
  # Depending what's inserted, we might be wrong. For instance, inserting 'foo'
  # into 'asdfasdf' could result in 'asdfoofasdf'. we'd be off by one b/c of the 'f'
  insert_point = target.rindex(source, insert_point)
  overflow = insert_point...(insert_point + source.length)

  # handle shifting the inserted range
  properties.shift_tags([overflow])

  properties.copy_from(source, target, insert_point, propagation_node.untags)
  properties.cleanup_tags
end

.propagate_keep_select(propagation_node, preshift, ret, _block) ⇒ Object

This method will implement both SELECT and KEEP actions for IO::Buffer

Parameters:



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# File 'lib/contrast/agent/assess/policy/propagator/buffer.rb', line 90

def propagate_keep_select propagation_node, preshift, ret, _block
  # We need the return in both propagation cases. So this propagation is
  # applied in the Contrast::Utils::Patching::PatchUtils.apply_post_patch.
  # If IO::Buffer gets duplicated the dup buffer is not allocated,
  # it's empty, So a way of doing it is to use the original object
  # itself. The class is handled with no dup in preshift.
  return unless (properties = Contrast::Agent::Assess::Tracker.properties!(ret)) &&
      (source = preshift.object)

  # KEEP means the tags just pass from the source to the target as is.
  # There is a case with IO::Buffer use, when we don't pass any args,
  # and the target (ret) in this case is the whole strings. We should
  # use Keep action. Otherwise the SELECT action covers all other cases.
  if preshift.args.empty?
    # KEEP
    properties.copy_from(source, ret, 0, propagation_node.untags)
    ret
  else
    # SELECT
    Contrast::Agent::Assess::Policy::Propagator::Select.select_tagger(propagation_node, preshift, ret,
                                                                      nil)
  end
end