Brute Force Attack in Hanami (Ruby)

A brute force attack targets authentication endpoints by systematically trying many combinations of credentials until the correct one is found. In Hanami, a lightweight web framework for Ruby, authentication is often implemented via session-based cookies or token-based mechanisms exposed through dedicated endpoints. When these endpoints lack proper rate limiting or account lockout policies, they become susceptible to brute force attempts. Because Hanami applications typically run on Ruby's Rack stack without built-in throttling, an attacker can script rapid requests against /auth/login or similar endpoints using common username lists and password dictionaries. The framework itself does not provide security controls, so developers must explicitly configure protections such as Rack::Attack or external middleware. Without these, each request is processed at full speed, enabling attackers to exhaust password space within minutes if weak passwords are used.

Real-world exposure occurs when Hanami apps expose authentication APIs directly to the internet without network-level restrictions. For example, a public API endpoint that accepts POST requests with username and password fields and returns 200 OK on success or 401 Unauthorized on failure allows attackers to automate credential testing. Tools like curl or Python's requests library can loop through thousands of password guesses per minute. Each failed attempt leaks no additional information beyond the HTTP status code, but successful authentication grants immediate access. This pattern is common in microservices where service-to-service authentication uses bearer tokens, but if token endpoints are unauthenticated or poorly scoped, brute force becomes feasible. The lack of exponential backoff or CAPTCHA mechanisms further lowers the barrier to entry.

Mitigation requires deliberate design choices. Developers should enforce strong password policies and integrate rate limiting at the application level. Hanami supports Rack middleware, so adding Rack::Attack to throttle login attempts by IP address is straightforward. Example configuration:

require 'rack/attack'
Rack::Attack.new do |attacker|
  attacker.throttle 
    <= 5, <= 1.second, <= 'logins per minute'
    <= 'login_brute_force'
end
use Rack::Attack
This limits each IP to five login attempts per minute, dramatically reducing brute force throughput. Additionally, responses should not distinguish between 'invalid username' and 'incorrect password' to prevent user enumeration. Instead, always return a generic 401 Unauthorized message. Logging failed attempts with timestamps and source IPs helps detect attack patterns. Monitoring tools can alert when login failure rates spike, triggering temporary IP blocks. These practices close the attack surface that brute force exploits.

Remediation in Hanami focuses on hardening authentication flows using Ruby-native constructs. Developers should avoid storing passwords in plaintext and instead use secure hashing via bcrypt or argon2 gems. When validating credentials, compare password hashes using constant-time comparison to prevent timing attacks. Example of secure password verification:

require 'bcrypt'
def verify_credentials(username, password)
  user = UserRepository.new.find_by(username: username)
  return false unless user
  BCrypt::Password.new(user.password_hash) == password
end
This ensures that hash verification takes consistent time regardless of input, reducing side-channel leakage. Furthermore, implement account lockout logic after a configurable number of failed attempts. Example using a simple in-memory store (replace with Redis in production):
FAILED_ATTEMPTS = {}
MAX_ATTEMPTS = 5
def record_failed_attempt(ip)
  FAILED_ATTEMPTS[ip] ||= 0
  FAILED_ATTEMPTS[ip] += 1
  return false if FAILED_ATTEMPTS[ip] < MAX_ATTEMPTS
  # Lock out after MAX_ATTEMPTS
  true
end
Integrate this logic into the login action before password verification. Return a generic error message regardless of whether the username exists, preventing enumeration. Finally, enforce HTTPS at the web server level (e.g., via Nginx) to prevent credential leakage over the network. These steps close the brute force vector by combining cryptographic hygiene, rate control, and response standardization.