Bola Idor in Grape with Cockroachdb

BOLA (Broken Object Level Authorization) / IDOR occurs when an API exposes internal object identifiers without verifying that the requesting user is authorized to access the specific resource. The combination of the Grape web framework and CockroachDB as the backend datastore can unintentionally create this condition when route parameters are used directly as database keys without an authorization check per request.

In a Grape API, developers often define member routes like /users/:id/profile or /accounts/:account_id/transactions/:transaction_id. If the handler retrieves a record from CockroachDB using $1 placeholders bound to these parameters, but does not confirm that the authenticated subject (e.g., a user or service token) has permission to view or modify that specific row, the endpoint becomes IDOR-prone. For example, an attacker can increment or guess numeric IDs to enumerate other users’ profiles or sensitive financial records. CockroachDB, being a distributed SQL database, does not enforce application-level permissions; it executes queries exactly as issued. Therefore, if the authorization logic is omitted in Grape, the database will faithfully return data the attacker should not see or allow them to update data they should not touch.

Consider an endpoint that fetches a transaction by ID. A developer might write a simple query like SELECT * FROM transactions WHERE id = $1 and return the result. Without cross-referencing the authenticated user’s tenant or ownership column, any valid transaction ID in the table becomes accessible. This is especially risky in distributed schemas where Cockroachdb’s global, consistent visibility means rows are reachable across nodes once the query is formed. The vulnerability is not in CockroachDB itself but in how the Grape service uses it: treating the database row ID as an authorization boundary rather than a data identifier.

Moreover, if the API uses composite keys or UUIDs exposed in URLs, the risk increases. An attacker might manipulate :account_id in a path like /accounts/:account_id/users/:user_id to pivot across accounts if the Grape handler does not validate that the authenticated context matches the provided :account_id. Because Cockroachdb supports complex schemas and secondary indexes, it can efficiently serve these unauthorized lookups, making the exposure more impactful. Proper BOLA/IDOR mitigation requires integrating a policy check—such as comparing the resource’s owner or allowed scopes with the authenticated subject—before issuing any CockroachDB query in Grape routes.

Remediation focuses on ensuring every data access in Grape includes an explicit authorization check tied to the authenticated context. Instead of relying on route-level IDs as implicit permissions, compare the requested resource’s attributes (such as owner_id, tenant_id, or account_id) against the subject’s claims before querying CockroachDB.

Example secure handler using the pg gem with parameterized queries and ownership validation:

require 'grape'
require 'pg'

class MyAPI < Grape::API
  format :json

  helpers do
    def current_user
      @current_user ||= User.find_by(token: env['HTTP_AUTH_TOKEN'])
    end

    def require_ownership(resource_type, resource_id)
      owner_id = current_user.id
      client = PG.connect(ENV['COCKROACHDB_URL'])

      case resource_type
      when 'transaction'
        row = client.exec_params('SELECT id, account_id FROM transactions WHERE id = $1', [resource_id]).first
        unless row&['account_id'] == owner_id
          fail Grape::Exceptions::Forbidden, 'Not authorized'
        end
      when 'profile'
        row = client.exec_params('SELECT id, user_id FROM profiles WHERE id = $1', [resource_id]).first
        unless row&['user_id'] == owner_id
          fail Grape::Exceptions::Forbidden, 'Not authorized'
        end
      end
    ensure
      client.close if client
    end
  end

  resource :transactions do
    desc 'Get transaction details with ownership check'
    params do
      requires :id, type: Integer, desc: 'Transaction ID'
    end
    get ':id' do
      require_ownership('transaction', params[:id])
      client = PG.connect(ENV['COCKROACHDB_URL'])
      result = client.exec_params('SELECT id, account_id, amount, currency FROM transactions WHERE id = $1', [params[:id]])
      result.first
    end
  end
end

This pattern ensures that even when using Cockroachdb’s efficient distributed SQL layer, the application enforces BOLA checks by validating ownership (e.g., account_id) against the authenticated user before returning or modifying data. For nested resources, extend the check to include hierarchical ownership, such as confirming that the requested :account_id matches the user’s account.

Additionally, prefer parameterized queries with exec_params to avoid SQL injection and ensure consistent performance in Cockroachdb. Avoid constructing SQL by string interpolation, even if IDs are integers. Combine this with role-based access control if your schema uses shared tenants or service accounts, and consider row-level security (RLS) in Cockroachdb as an additional layer, though application-level checks in Grape remain essential.