# Copyright (c) 2020 Contrast Security, Inc. See https://www.contrastsecurity.com/enduser-terms-0317a for more details.
# frozen_string_literal: true
cs__scoped_require 'contrast/utils/object_share'
cs__scoped_require 'contrast/utils/sha256_builder'
cs__scoped_require 'contrast/agent/assess/events/event_factory'
cs__scoped_require 'contrast/agent/assess/policy/trigger_validation/trigger_validation'
cs__scoped_require 'contrast/components/interface'
module Contrast
module Agent
module Assess
module Policy
# A trigger method is one which can perform a dangerous action, as
# described by the Contrast::Agent::Assess::Policy::TriggerNode class.
# Each such method will call to this module just after invocation in
# order to determine if the call was done safely. In those cases where
# it was not, a Finding report is issued to the Service
module TriggerMethod
include Contrast::Components::Interface
access_component :analysis, :logging
# The level of TeamServer compliance our traces meet
CURRENT_FINDING_VERSION = 2
class << self
# This is called from within our woven proc. It will be called as if it
# were inline in the Rack application.
#
# @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode]
# the node that applies to the method being called
# @param object [Object] the Object on which the method was invoked
# @param ret [Object] the Return of the invoked method
# @param args [Array<Object>] the Arguments with which the method
# was invoked
def apply_trigger_rule trigger_node, object, ret, args
return if trigger_node.nil?
current_context = Contrast::Agent::REQUEST_TRACKER.current
return unless current_context&.analyze_request? && ASSESS.enabled?
if trigger_node.sources&.any?
trigger_node.sources.each do |marker|
source = determine_source(marker, object, ret, args)
apply_trigger(current_context,
trigger_node,
source,
object,
ret,
*args)
end
else
apply_trigger(current_context,
trigger_node,
nil,
object,
ret,
*args)
end
end
def apply_eval_trigger context, trigger_node, source, object, ret, *args
apply_trigger(context, trigger_node, source, object, ret, *args)
end
# This converts the source of the finding, and the events leading
# up to it into a Finding
#
# @param context [Contrast::Utils::ThreadTracker] the current request
# context
# @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode]
# the node to direct applying this trigger event
# @param source [Object] the source of the Trigger Event
# @param object [Object] the Object on which the method was invoked
# @param ret [Object] the Return of the invoked method
# @param args [Array<Object>] the Arguments with which the method
# was invoked
# @return [Contrast::Api::Dtm::Finding, nil] the
# Contrast::Api::Dtm::Finding to send to TeamServer or nil if
# conditions were not met
def build_finding context, trigger_node, source, object, ret, *args
return unless Contrast::Agent::Assess::Policy::TriggerValidation.valid?(trigger_node, object, ret, args)
request = context.request
env = request.env
return if defined?(ActionController::Live) &&
env &&
env['action_controller.instance'].cs__class.included_modules.include?(ActionController::Live)
finding = Contrast::Api::Dtm::Finding.new
finding.rule_id = Contrast::Utils::StringUtils.protobuf_safe_string(trigger_node.rule_id)
finding.version = CURRENT_FINDING_VERSION
build_from_source(finding, source)
trigger_event = Contrast::Agent::Assess::Events::EventFactory.build(trigger_node, source, object, ret, args).to_dtm_event
finding.events << trigger_event
build_hash(finding, source)
finding.routes << context.route if context.route
context.activity.findings << finding
logger.trace('Finding created',
node_id: trigger_node.id,
source_id: source.__id__,
rule: trigger_node.rule_id)
rescue StandardError => e
logger.error('Unable to build a finding', e, rule: trigger_node.rule_id, node_id: trigger_node.id)
end
private
# This is our method that actually checks the taint on the object
# our trigger_node targets.
#
# @param context [Contrast::Utils::ThreadTracker] the current request
# context
# @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode]
# the node to direct applying this trigger event
# @param source [Object] the source of the Trigger Event
# @param object [Object] the Object on which the method was invoked
# @param ret [Object] the Return of the invoked method
# @param args [Array<Object>] the Arguments with which the method
# was invoked
def apply_trigger context, trigger_node, source, object, ret, *args
return unless context && trigger_node
return if trigger_node.rule_disabled?
return if trigger_node.dataflow? && source.nil?
if trigger_node.regexp_rule?
apply_regexp_rule(context, trigger_node, source, object, ret, *args)
elsif trigger_node.custom_trigger?
trigger_node.apply_custom_trigger(context, trigger_node, source, object, ret, *args)
elsif trigger_node.dataflow?
apply_dataflow_rule(context, trigger_node, source, object, ret, *args)
else # trigger rule - just calling the method is dangerous
build_finding(context, trigger_node, source, object, ret, *args)
end
rescue StandardError => e
logger.warn('Unable to apply trigger', e, node_id: trigger_node.id)
end
# Given the marker from the trigger_node (the pointer indicating
# the entity from which the taint originated), return the entity on
# which this trigger needs to operate.
#
# In an effort to speed up this lookup, we've changed the marker
# for parameters to be implicit - if it is not a return or an
# object, it must be a parameter, which we can reference either by
# index or by name.
#
# @param marker [String] the source marker that indicates which
# Object
# @param object [Object] the Object on which the method was invoked
# @param ret [Object] the Return of the invoked method
# @param args [Array<Object>] the Arguments with which the method
# was invoked
# @return [Object] the literal object that this Trigger Event
# verifies
def determine_source marker, object, ret, args
case marker
when Contrast::Utils::ObjectShare::RETURN_KEY
ret
when Contrast::Utils::ObjectShare::OBJECT_KEY
object
else # 'P'
if marker.is_a?(Integer)
args[marker]
else
arg = nil
args.each do |search|
next unless search.is_a?(Hash)
arg = search[marker]
break if arg
end
arg
end
end
end
# This is our method that actually checks the taint on the object
# our trigger_node targets for our Regexp based rules.
#
# @param context [Contrast::Utils::ThreadTracker] the current request
# context
# @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode]
# the node to direct applying this trigger event
# @param source [Object] the source of the Trigger Event
# @param object [Object] the Object on which the method was invoked
# @param ret [Object] the Return of the invoked method
# @param args [Array<Object>] the Arguments with which the method
# was invoked
def apply_regexp_rule context, trigger_node, source, object, ret, *args
return unless source.is_a?(String)
return if trigger_node.good_value && source.match?(trigger_node.good_value)
return if trigger_node.bad_value && source !~ trigger_node.bad_value
build_finding(context, trigger_node, source, object, ret, *args)
end
# This is our method that actually checks the taint on the object
# our trigger_node targets for our Dataflow based rules.
#
# @param context [Contrast::Utils::ThreadTracker] the current request
# context
# @param trigger_node [Contrast::Agent::Assess::Policy::TriggerNode]
# the node to direct applying this trigger event
# @param source [Object] the source of the Trigger Event
# @param object [Object] the Object on which the method was invoked
# @param ret [Object] the Return of the invoked method
# @param args [Array<Object>] the Arguments with which the method
# was invoked
def apply_dataflow_rule context, trigger_node, source, object, ret, *args
return unless source
if Contrast::Utils::DuckUtils.quacks_to?(source, :cs__properties)
return unless source.cs__tracked?
return unless trigger_node.violated?(source)
build_finding(context, trigger_node, source, object, ret, *args)
elsif Contrast::Utils::DuckUtils.iterable_hash?(source)
source.each_pair do |key, value|
apply_dataflow_rule(context, trigger_node, key, object, ret, *args)
apply_dataflow_rule(context, trigger_node, value, object, ret, *args)
end
elsif Contrast::Utils::DuckUtils.iterable_enumerable?(source)
source.each do |value|
apply_dataflow_rule(context, trigger_node, value, object, ret, *args)
end
else
logger.warn('Trigger source is of unknown type. Unable to inspect.',
node_id: trigger_node.id,
source_id: source.__id__,
source_type: source.cs__class.to_s)
logger.trace(source.to_s[0..99])
end
end
def build_from_source finding, source
return unless source
return unless Contrast::Utils::DuckUtils.quacks_to?(
source,
:cs__properties)
return unless source.cs__properties
# events could technically be nil, but we would have failed
# the rule check before getting here. not worth the nil check
source.cs__properties.events.each do |event|
finding.events << event.to_dtm_event
end
# Google::Protobuf::Map doesn't support merge!, so we have to do this
# long form
source_props = source.cs__properties.properties
return unless source_props
source_props.each_pair do |key, value|
key = Contrast::Utils::StringUtils.force_utf8(key)
finding.properties[key] = Contrast::Utils::StringUtils.force_utf8(value)
end
end
def build_hash finding, source
hash_code = Contrast::Utils::HashDigest.generate_event_hash(finding, source)
finding.hash_code = Contrast::Utils::StringUtils.force_utf8(hash_code)
finding.preflight = Contrast::Utils::PreflightUtil.create_preflight(finding)
end
end
end
end
end
end
end