Shellshock in Hanami with Api Keys

Shellshock (CVE-2014-6271 and related variants) is a command injection vulnerability in the Bash shell that arises when environment variables contain malicious payloads. In Hanami, a Ruby web framework that emphasizes modular apps and explicit APIs, the combination of environment-based configuration and Api Keys can unintentionally expose this vector. When Hanami applications load external configuration or integrate with services via Api Keys, keys and secrets are often injected into the process environment (e.g., through dotenv, systemd, or container orchestration). If an attacker can control part of the environment and Hanami’s boot or runtime code passes user-influenced data into Bash subprocesses (such as via system, %x, or Open3), a Shellshock injection can occur. The Api Key itself may not be vulnerable, but if it is read into an environment variable and later used in a shell command without sanitization, the crafted payload can execute arbitrary code during key validation, logging, or telemetry collection. This is especially relevant when Hanami services run in environments where environment variables are merged from multiple sources, such as CI pipelines or container images, and where Bash is present to process hook scripts or deployment tasks. Because Hanami does not perform implicit filtering on environment-derived values used in shell execution, an Api Key–driven workflow that invokes Bash becomes a potential path for unauthenticated remote code execution. Shellshock exploits in this context do not target the Api Key format; they target the unsafe use of environment variables in subprocess creation. The risk is not theoretical: real-world deployments have seen CI/CD jobs and web processes execute injected commands via Bash when environment variables contained shell function payloads. middleBrick detects this scenario under its Unsafe Consumption and Input Validation checks, highlighting subprocess usage with environment-derived data. Because the scan runs unauthenticated and analyzes runtime behavior alongside OpenAPI specs, it can flag risky patterns where Api Key handling intersects with shell execution. By correlating findings across the Authentication and Unsafe Consumption checks, middleBrick can surface cases where secrets are exposed to shell contexts. middleBrick’s LLM/AI Security checks further ensure that no prompt or configuration leakage occurs if keys are logged or echoed in debug endpoints. Overall, the combination of Hanami’s flexible integration points and the pervasive nature of Bash in deployment tooling makes the Shellshock vector with Api Keys a practical concern that merits explicit validation and secure coding practices.

To remediate Shellshock risks when using Api Keys in Hanami, ensure that environment variables containing secrets are never passed to Bash subprocesses and that all external data is treated as untrusted. Use Hanami’s built-in configuration isolation and Ruby’s safe process APIs. Below are concrete, working examples.

• Safe Api Key handling with Open3 and explicit argument passing (no shell interpolation):

require 'open3'

# Read key from a secure source, not from user input
api_key = ENV.fetch('HANAMI_API_KEY', nil)
raise 'API key missing' unless api_key

# Safe: pass arguments directly; do not interpolate into a shell string
stdout, stderr, status = Open3.capture3('curl', '-H', "Authorization: Bearer #{api_key}", 'https://api.example.com/health')

if status.success?
  puts "Health check passed"
else
  puts "Failed: #{stderr}"
end

• Avoiding Bash entirely by using pure Ruby HTTP clients:

require 'net/http'
require 'uri'

api_key = ENV.fetch('HANAMI_API_KEY', nil)
uri = URI('https://api.example.com/health')
request = Net::HTTP::Get.new(uri)
request['Authorization'] = "Bearer #{api_key}"

response = Net::HTTP.start(uri.hostname, uri.port, use_ssl: true) do |http|
  http.request(request)
end

puts "Status: #{response.code}" if response.is_a?(Net::HTTPSuccess)

• If shell commands are unavoidable, sanitize and drop dangerous environment variables before spawning:

require 'shellwords'

# Drop Bash-specific functions that could exploit Shellshock
ENV.delete('BASH_FUNC_export_key%%')
ENV.delete('BASH_FUNC_key%%')

# Use shellwords to safely construct commands
command = ['curl', '-H', Shellwords.shelljoin(["Authorization: Bearer #{ENV['HANAMI_API_KEY']}"])]
# Note: In production, prefer the non-shell approaches above

• Configure Hanami to load Api Keys via credentials or encrypted files rather than environment variables when possible, and restrict subprocess usage in initializers:

# config/initializers/security.rb
Hanami.configure do |config|
  # Prefer credentials or vault integration
  config.api_key = ENV['HANAMI_API_KEY'] # ensure ENV is sanitized elsewhere
end

# Guard against risky calls in any custom scripts
module SafeExec
  def self.safe_system(*args)
    raise 'Shell execution disabled' if args.any? { |a| a.to_s.include?('bash') || a.to_s.include?('sh') }
    system(*args)
  end
end

These patterns reduce the attack surface by eliminating implicit shell interpretation and ensuring that Api Keys are handled as data rather than as part of executable strings. They align with OWASP API Top 10 controls around Security Misconfiguration and Injection.