False positive dangerous send case when

[ngouy]

Background

Rails Version: 7.0.3.1 Brakeman Version: 5.3.1 ruby version: ruby 2.7.5p203 (2021-11-24 revision f69aeb8314) [x86_64-darwin20]

I'm using a case;when with predefined values to make sure the value is matching a specific finite list of values. Then using a send (tried with public_send and send) but brakeman is not happy with that.

I'm not sure if:

• it's a bug (I think so)
• it's fixable
• or maybe meant to work like that

Issue

False positive dangerous send:

My code:

AVAILABLE_TIME_STEPS = ["week", "day", "year"]

value = params.observation_window.fetch("value")
step = params.observation_window.fetch("step")

case step
when "last_n"
  offset = [scope.count - value, 0].max
  scope.offset(offset).limit(value)
when *AVAILABLE_TIME_STEPS
  time_ago = value.public_send(step).ago(range_end)
  range = (time_ago..range_end)
  scope.where(observed_date: range)
else
  raise "unknown step"
end

Other Error

Run Brakeman with --debug to see the full stack trace.

Stack trace:

trace:

== Warnings ==

Confidence: High
Category: Dangerous Send
Check: Send
Message: User controlled method execution
Code: params.observation_window.fetch("value").public_send(params.observation_window.fetch("step"))
File: app/lib/workflows/matchers/observation.rb
Line: 103