Class: Scryer::Rules::CsrfProtectionRule

Inherits:
Scryer::Rule show all
Defined in:
lib/scryer/rules/csrf_protection_rule.rb

Overview

Flags a controller class named *Controller that calls skip_before_action :verify_authenticity_token without that same file (or, best-effort, without any protect_from_forgery call visible in it) — skipping CSRF verification on a controller that isn't clearly API-only (no < ActionController::API / ActionController::Base used alongside explicit null_session) is a common way to accidentally disable CSRF protection app-wide for that controller's actions.

Instance Attribute Summary

Attributes inherited from Scryer::Rule

#file, #sexp, #source

Instance Method Summary collapse

Methods inherited from Scryer::Rule

inherited, #initialize

Constructor Details

This class inherits a constructor from Scryer::Rule

Instance Method Details

#scan ⇒ Object 



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# File 'lib/scryer/rules/csrf_protection_rule.rb', line 16

def scan
  findings = []

  Ast.each_node(sexp) do |node|
    next unless Ast.tagged?(node, :class)

    class_name = Ast.ident_text(node[1].is_a?(Array) ? node[1][1] : nil)
    next unless class_name.to_s.end_with?("Controller")

    body = node[3]
    skip_node = find_skip_verify(body)
    next unless skip_node

    has_null_session_pattern = each_descendant_call_names(body).any? do |name|
      name == "protect_from_forgery"
    end
    next if has_null_session_pattern # they've explicitly configured an alternative

    line = Ast.line_of(skip_node)
    findings << finding(
      line: line,
      message: "`#{class_name}` skips CSRF token verification (`skip_before_action " \
                ":verify_authenticity_token`) without declaring its own " \
                "`protect_from_forgery` policy — if this controller renders any HTML forms " \
                "or is reachable with a browser session cookie, this leaves it open to " \
                "cross-site request forgery.",
      suggested_fix: "If this is a true JSON/API-only controller, make that explicit with " \
                      "`protect_from_forgery with: :null_session` (or inherit from a base " \
                      "class that does) rather than bypassing verification silently. If it's " \
                      "not API-only, remove the `skip_before_action` and let the app's normal " \
                      "CSRF handling apply."
    )
  end

  findings
end