Auth Bypass in Sinatra with Cockroachdb

An authentication bypass in a Sinatra application using CockroachDB typically arises from improper session handling, weak parameter validation, or misconfigured query logic that fails to enforce identity checks on every request. Sinatra’s lightweight nature means developers often manage sessions and database access directly, which increases the risk when security controls are inconsistent.

One common pattern is constructing SQL queries by string interpolation or naive concatenation, which can lead to authentication-relevant logic being subverted through injection or parameter manipulation. For example, a login route might build a WHERE clause without strict type checks or prepared statements, allowing an attacker to manipulate the query to return a valid session or admin flag without satisfying intended credentials.

CockroachDB, while PostgreSQL-wire compatible, does not intrinsically protect against application-layer logic errors. If Sinatra code uses string-based query building and treats user-supplied identifiers as trusted, an attacker can supply crafted input that changes the effective WHERE clause, effectively bypassing intended authentication checks. This is often seen in IDOR or BOLA scenarios where object-level authorization is not re-evaluated against the authenticated subject after initial login.

Another vector involves session token handling. If tokens or session identifiers are stored in URLs or weakly protected cookies, and the Sinatra app uses CockroachDB to look up sessions without verifying scope and binding, an attacker can reuse or predict identifiers. The database may return data even when the session context does not match the expected user or permissions, because the application neglects to re-validate ownership on each request.

Consider a route that retrieves a user profile using an ID taken directly from parameters without ensuring it matches the authenticated subject. Because Sinatra does not enforce middleware-level ownership checks, and CockroachDB returns rows based solely on the provided SQL, the combination can unintentionally expose data or allow privilege escalation when the query omits the subject filter.

These risks are compounded when OpenAPI specs are not rigorously aligned with runtime behavior. An API defined with endpoints that appear to require authentication might, under certain parameter conditions, skip checks in Sinatra code paths that incorrectly assume CockroachDB will enforce row-level security. Because middleBrick tests unauthenticated attack surfaces and maps findings to frameworks like OWASP API Top 10, such misalignments are surfaced as authentication-related findings with remediation guidance.

To mitigate authentication bypass when using CockroachDB with Sinatra, adopt strict parameterization, explicit subject scoping, and defensive query construction. Always use prepared statements or an ORM that enforces type safety, and ensure every database read includes the authenticated subject as part of the WHERE clause.

require 'sinatra'
require 'pg'

# Establish connection to CockroachDB
DB = PG.connect(
  host: ENV['COCKROACH_HOST'],
  port: ENV['COCKROACH_PORT'],
  dbname: ENV['COCKROACH_DB'],
  sslmode: 'require'
)

helpers do
  def current_user
    @current_user ||= begin
      token = request.cookies['session_token']
      # Validate and fetch session from CockroachDB with subject binding
      result = DB.exec_params('SELECT user_id, expires_at FROM sessions WHERE token = $1 AND expires_at > NOW()', [token])
      result.first['user_id'] if result.ntuples == 1
    end
  end

  def ensure_authenticated!
    halt 401, { error: 'Unauthorized' }.to_json unless current_user
  end

  def ensure_owns_resource!(resource_id)
    halt 403, { error: 'Forbidden' }.to_json unless resource_belongs_to_user?(resource_id, current_user)
  end

  def resource_belongs_to_user?(resource_id, user_id)
    res = DB.exec_params(
      'SELECT 1 FROM widgets WHERE id = $1 AND user_id = $2',
      [resource_id, user_id]
    )
    res.ntuples == 1
  end
end

# Login route with strict parameter usage
post '/login' do
  username = params[:username].to_s.strip
  password = params[:password].to_s.strip

  # Use parameterized query to prevent injection
  result = DB.exec_params(
    'SELECT id, password_hash FROM users WHERE username = $1',
    [username]
  )

  user = result.first
  if user && BCrypt::Password.new(user['password_hash']) == password
    token = SecureRandom.uuid
    DB.exec_params(
      'INSERT INTO sessions (token, user_id, expires_at) VALUES ($1, $2, NOW() + INTERVAL \'1 hour\')',
      [token, user['id']]
    )
    set_cookie 'session_token', { value: token, httponly: true, secure: true }
    { status: 'ok' }.to_json
  else
    halt 401, { error: 'Invalid credentials' }.to_json
  end
end

# Protected route with subject-bound query
get '/widgets/:id' do
  ensure_authenticated!
  widget_id = params[:id]
  ensure_owns_resource!(widget_id)

  result = DB.exec_params(
    'SELECT id, name, description FROM widgets WHERE id = $1 AND user_id = $2',
    [widget_id, current_user]
  )

  if result.ntuples == 1
    result.first.to_hash.to_json
  else
    halt 404, { error: 'Not found' }.to_json
  end
end

# Admin route with role check from authenticated subject
get '/admin/users' do
  ensure_authenticated!
  user = current_user
  result = DB.exec_params('SELECT role FROM users WHERE id = $1', [user])
  halt 403, { error: 'Insufficient permissions' }.to_json unless result.first['role'] == 'admin'

  result = DB.exec_params('SELECT id, username, role FROM users')
  result.to_a.to_json
end

Key practices:

• Use exec_params with positional placeholders ($1, $2) to enforce type separation and avoid injection that could strip WHERE conditions.
• Include the authenticated subject (e.g., user_id) in every query that accesses user-owned resources, rather than relying on application-level filters alone.
• Validate and bound sessions server-side, and bind them to the subject when checking permissions.
• Return 403 for mismatched ownership even when the record exists, preventing information leakage via timing or existence differences.
• In CI/CD, use the middleBrick GitHub Action to fail builds if risk scores degrade, ensuring that changes to authentication or database interaction do not introduce regressions.

For teams managing many APIs, the middleBrick Pro plan provides continuous monitoring and can integrate with GitHub Actions to gate deployments based on risk thresholds, helping maintain secure configurations as code evolves.