Cache Poisoning in Sinatra with Cockroachdb

Cache poisoning in a Sinatra application that uses CockroachDB typically occurs when an application caches responses that include user-specific or tenant-specific data without sufficient key isolation. Because CockroachDB is often used in distributed environments where the same schema may serve multiple clients or organizations, missing tenant or context differentiation in cache keys can cause one user’s data to be served to another user. Sinatra’s lightweight routing and middleware stack can inadvertently expose this risk when developers rely on request path or simple query parameters as the sole cache key, omitting identifiers such as account_id or tenant_id.

The risk is compounded when responses include sensitive headers, authentication tokens, or personalized content that should never be shared across users. An attacker who can influence any part of the cache key—such as a query parameter used to select a database tenant or an object identifier—may be able to inject or overwrite cached entries. Since CockroachDB preserves strong consistency, a poisoned cache entry can be reliably retrieved and reflected to other users, effectively turning a transient cache issue into a cross-user data exposure issue.

In a typical workflow, Sinatra routes issue SQL queries to CockroachDB using interpolated values or ORM parameters. If the application caches at the application layer (e.g., with Redis or Memcached) and the cache key does not incorporate the full request context—including tenant, user role, and exact query parameters—an attacker can manipulate inputs to retrieve or modify cached data. For example, changing an account identifier in a URL path or query parameter might not change the cache key if the developer hashes only the route and static parameters. This mismatch between logical cache scope and implementation enables one user’s data to appear as another’s, which may map to OWASP API Top 10 A01:2023 broken object level authorization (BOLA) or excessive data exposure.

middleBrick scans such endpoints during unauthenticated testing and can surface these risks by correlating OpenAPI/Swagger specs (with full $ref resolution) against runtime behavior. Because Sinatra applications often define routes with minimal syntactic overhead, it is easier to miss contextual parameters that should influence caching. The scanner checks for missing authorization in cache-influencing inputs, improper key construction, and data exposure across tenants, aligning findings with compliance frameworks such as PCI-DSS and SOC2.

To remediate cache poisoning when using CockroachDB with Sinatra, ensure cache keys are deterministic, scoped, and include all context that affects the response. This includes tenant or account identifiers, user roles, and the full set of query parameters that meaningfully change the data. Avoid using raw user input directly in cache keys; instead, normalize and validate inputs before incorporating them.

require 'sinatra'
require 'pg' # CockroachDB wire-compatible PostgreSQL driver
require 'digest'

# Establish connection (in production, use a connection pool)
def db
  @db ||= PG.connect(
    host: ENV['COCKROACH_HOST'],
    port: ENV['COCKROACH_PORT'] || 26257,
    dbname: ENV['COCKROACH_DB'],
    user: ENV['COCKROACH_USER'],
    password: ENV['COCKROACH_PASSWORD']
  )
end

# Secure cache key builder that includes tenant and full query context
def cache_key_for(path, params, tenant_id, user_role)
  # Normalize and sort params to ensure consistency
  filtered = params.select { |k, _| %w[sort order limit offset].include?(k) }
  digest = Digest::SHA256.hexdigest(
    [path, tenant_id, user_role, filtered.to_json].join('|')
  )
  "v1:#{digest}"
end

get '/api/accounts/:account_id/users' do
  tenant_id = params['tenant_id'] || headers['x-tenant-id']
  user_role = current_user_role # implement your auth logic
  account_id = params['account_id']

  cache_key = cache_key_for(request.path_info, request.GET, tenant_id, user_role)
  cached = $redis.get(cache_key)
  return cached if cached

  # Parameterized query to CockroachDB to avoid SQL injection
  results = db.exec_params(
    'SELECT id, name, email FROM users WHERE account_id = $1 ORDER BY name LIMIT $2',
    [account_id, 50]
  )

  response = results.map(&:to_hash)
  $redis.setex(cache_key, 300, response.to_json) # 5-minute TTL
  response.to_json
end

In this example, the cache key incorporates the request path, tenant context, user role, and normalized query parameters. This prevents attackers from swapping tenant identifiers without changing the effective cache key. CockroachDB’s wire protocol is compatible with standard PostgreSQL clients, so using parameterized queries with pg ensures that SQL injection is not introduced through dynamic values.

For broader protection, apply the same scoping logic to all endpoints that interact with CockroachDB, and ensure that cache invalidation respects tenant boundaries. When integrating with CI/CD, the middleBrick GitHub Action can be configured to fail builds if risk scores exceed your threshold, providing automated checks that cache-related data exposure risks are not introduced during development.

Additionally, the middleBrick CLI can be used locally to scan Sinatra endpoints and validate that cache keys and authorization checks align with expected behavior. Its LLM/AI Security checks are especially useful when endpoints expose generated text or summaries that could inadvertently leak CockroachDB schema details through cached outputs.