Class: Scryer::Rules::OpenRedirectRule

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

Overview

Flags redirect_to called with params[...] (or plain params) directly as the destination — an attacker can craft a link to your own site that redirects the victim onward to an attacker-controlled domain (a classic phishing enabler), unless the value is validated against an allow-list first.

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/open_redirect_rule.rb', line 14

def scan
  findings = []

  Ast.each_node(sexp) do |node|
    next unless Ast.tagged?(node, :method_add_arg, :command, :command_call)

    inner = Ast.tagged?(node, :method_add_arg) ? node[1] : node
    name_pair = Ast.call_name(inner)
    next unless name_pair && name_pair[1] == "redirect_to"

    args = Ast.call_arguments(node)
    next if args.empty?

    target = args.first
    next unless references_raw_params?(target)

    line = Ast.line_of(target) || Ast.line_of(node)
    findings << finding(
      line: line,
      message: "`redirect_to` receives `params` (or a subscript of it) directly as the " \
                "destination — a crafted link can redirect users from your domain to an " \
                "attacker-controlled site, which is commonly used for phishing.",
      suggested_fix: "Validate the destination against an allow-list before redirecting, " \
                      "e.g. `redirect_to params[:next] if ALLOWED_PATHS.include?(params[:next])`, " \
                      "or only allow relative paths on your own host " \
                      "(`URI.parse(params[:next]).host.nil?`), falling back to a safe default otherwise."
    )
  end

  findings
end