Buffer Overflow in Hanami

Remediating buffer overflow risks in Hanami applications involves defensive input handling, especially where user data interfaces with native code or influences memory allocation. Since Ruby manages memory safely, the focus is on preventing unsafe data from reaching vulnerable native libraries or causing resource exhaustion.

Key strategies include:

• Strict validation of user-supplied length values before use in read, unpack, or similar methods
• Setting hard limits on upload size and processing duration
• Using safe defaults and whitelisting for file types
• Keeping native dependencies updated

Refactor the earlier unsafe action using Hanami’s strong params and explicit bounds:

# apps/web/controllers/upload_image.rb
module Web::Controllers::UploadImage
  class Create
    include Web::Action

    params do
      required(:file).hash do
        required(:tempfile).filled
        optional(:length).filled(:int?, lteq: 10_485_760) # Max 10MB
      end
    end

    def call(params)
      if params.valid?
        # SAFE: Length is validated and bounded
        max_length = params[:file][:length] || 10_485_760
        data = params[:file][:tempfile].read([max_length, 10_485_760].min)
        ImageProcessor.process(data)
        self.body = { status: 'ok' }.to_json
      else
        self.status = 422
        self.body = { errors: params.error_messages }.to_json
      end
    end
  end
end

This uses Hanami’s built-in params validation to ensure length is an integer not exceeding 10MB. The read call then uses the lesser of the user-supplied value and a hard cap, preventing excessive allocation.

For file uploads, leverage Hanami’s integration with Rack::Attack or middleware to enforce global limits:

# config.ru
use Rack::Attack

Rack::Attack.throttle('uploads/ip', limit: 5, period: 60) do |req|
  if req.path == '/uploads' && req.post?
    req.ip
  end
end

Rack::Attack.maxupload = 10 * 1024 * 1024 # 10MB

Finally, keep native gems updated. Run bundle update mini_magick ruby-vips regularly and monitor RubySec Advisory Database for CVEs affecting dependencies with native extensions. middleBrick’s continuous monitoring (available in Pro and Enterprise tiers) can help detect outdated or vulnerable components in your Hanami API’s attack surface over time.