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Fix Unrestricted Resource Consumption in Grape

Unrestricted resource consumption in Grape APIs is a low-effort DoS vector. If you expose endpoints that perform heavy DB queries without pagination or accept massive payloads without size constraints, you're handing attackers a 'kill switch' for your application. We fix this by enforcing strict parameter limits and middleware-level throttling.

The Vulnerable Pattern

class VulnerableAPI < Grape::API
  resource :logs do
    desc 'Return all logs'
    get do
      # VULNERABLE: No pagination. Attacker can request millions of records,
      # exhausting memory and database connections.
      Log.all
    end

desc 'Upload log data'
post do
  # VULNERABLE: No validation on payload size or content.
  # Attacker can send a multi-gigabyte JSON blob.
  Log.create!(data: params[:data])
end


end
end

The Secure Implementation

To mitigate resource exhaustion, we implement three layers of defense. First, we use Grape's 'params' block to enforce 'values' constraints on pagination (preventing an attacker from requesting per_page=999999). Second, we enforce 'length' validation on input strings to prevent memory bloating from massive payloads. Third, it is critical to pair this with 'Rack::Attack' at the middleware layer to throttle IP addresses making excessive requests, ensuring the Ruby process doesn't spend CPU cycles parsing malicious garbage before the API logic even hits.

class SecureAPI < Grape::API
  # 1. Use Rack::Attack middleware for global rate limiting
  # 2. Enforce strict parameter validation

resource :logs do
desc ‘Return logs with enforced pagination’
params do
optional :page, type: Integer, default: 1
optional :per_page, type: Integer, default: 25, values: 1..100
end
get do
# SECURE: Paginated results with a hard upper limit on per_page
Log.page(params[:page]).per(params[:per_page])
end


desc 'Upload log data with size constraints'
params do
  # SECURE: Validating presence and length of input strings
  requires :data, type: String, length: { maximum: 5000 }
end
post do
  Log.create!(data: params[:data])
end


end
end

System Alert • ID: 7140
Target: Grape API
Potential Vulnerability

Your Grape API might be exposed to Unrestricted Resource Consumption

74% of Grape apps fail this check. Hackers use automated scanners to find this specific flaw. Check your codebase before they do.

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