Heartbleed in Hanami with Mutual Tls

Heartbleed (CVE-2014-0160) is a vulnerability in OpenSSL’s TLS heartbeat extension that allows an attacker to read memory from a server or client without leaving a detectable trace. When Hanami applications are deployed with Mutual Tls, the server requests and validates client certificates, but the underlying transport and OpenSSL implementation remain the primary security boundary. If the server uses a vulnerable OpenSSL version and has heartbeat enabled, memory disclosure can occur regardless of certificate validation logic.

In a Hanami setup with Mutual Tls, the application typically terminates TLS at a reverse proxy or load balancer that enforces client certificate verification. However, if the TLS termination endpoint itself runs a vulnerable OpenSSL build, Heartbleed can be triggered through crafted heartbeat requests. Hanami’s Ruby/Rack stack does not directly process TLS records; the risk is introduced by the C-based OpenSSL library used by the web server (e.g., Puma in cluster mode with SSL, or a proxy like Nginx or HAProxy) in front of the app. The combination therefore exposes the vulnerability when:

• OpenSSL versions prior to 1.0.1g are in use.
• Heartbeat extension is enabled (default in many configurations).
• Mutual Tls is configured for client authentication but the server does not strictly limit heartbeat payload sizes relative to the declared length, permitting oversized requests to elicit memory contents.

Operational scanning with middleBrick against an endpoint using Mutual Tls and a vulnerable OpenSSL footprint can surface findings aligned with Data Exposure and Encryption checks. The scanner tests the unauthenticated attack surface and can detect indicators such as unexpected memory echoes in heartbeat responses, while the OpenAPI/Swagger spec analysis cross-references spec definitions with runtime behavior to highlight anomalies. Note that middleBrick surfaces findings and provides remediation guidance but does not fix or block the issue.

Remediation focuses on eliminating the vulnerable OpenSSL behavior and ensuring Mutual Tls configuration does not inadvertently relax heartbeat validation. Upgrade OpenSSL to 1.0.1g or later and disable the heartbeat extension where possible. For Hanami deployments behind proxies or load balancers, enforce strong cipher suites and explicitly configure heartbeat settings at the proxy layer.

Example Nginx configuration for Mutual Tls with heartbeat mitigation:

server {
    listen 443 ssl;
    ssl_protocols TLSv1.2 TLSv1.3;
    ssl_certificate /etc/ssl/certs/server.crt;
    ssl_certificate_key /etc/ssl/private/server.key;
    ssl_client_certificate /etc/ssl/certs/ca.pem;
    ssl_verify_client on;
    # Disable heartbeat to mitigate Heartbleed
    ssl_options no_heartbeat;
    # Strong ciphersuites
    ssl_ciphers 'ECDHE-ECDSA-AES256-GCM-SHA384:ECDHE-RSA-AES256-GCM-SHA384';
    location / {
        proxy_pass http://localhost:23000;
        proxy_set_header X-Forwarded-Proto $scheme;
        proxy_set_header X-Client-Verify SUCCESS;
    }
}

Example Puma SSL configuration in a Hanami project (config/puma.rb) when terminating TLS at the app level (not recommended for production at scale, but useful for illustration):

ssl_bind '0.0.0.0', '6443', {
  key: '/etc/ssl/private/server.key',
  cert: '/etc/ssl/certs/server.crt',
  ca_file: '/etc/ssl/certs/ca.pem',
  verify_mode: 'verify_peer',
  # Ensure OpenSSL is built without heartbeat support or disable via options
  ssl_options: {
    no_heartbeat: true
  }
}

For CI/CD integration, the middleBrick GitHub Action can be added to fail builds if the security score drops below your defined threshold, ensuring that regressions in TLS configuration are caught before deployment. The CLI tool allows quick local verification: middlebrick scan <url> returns categorized findings, including Encryption and Data Exposure checks relevant to Heartbleed indicators.