How to remediate – SSL Root Certification Authority Certificate Information

1. Introduction

The SSL Root Certification Authority Certificate Information vulnerability means a self-signed root certificate is at the top of the SSL certificate chain for a service. This can indicate an internal or test environment certificate being used in production, or a misconfiguration. It presents a risk to confidentiality and integrity as trust validation may not be fully assured. Systems using SSL/TLS certificates are usually affected, including web servers, email servers, and VPN gateways.

2. Technical Explanation

The remote service is configured with an SSL certificate chain that includes a self-signed root Certification Authority (CA) at the top of the hierarchy. This bypasses standard trust validation processes used by clients to verify the authenticity of the server’s certificate. An attacker could potentially perform a man-in-the-middle attack if the client does not properly validate this self-signed root CA, or if the root CA is compromised.

• Root cause: The service is using a self-signed root CA instead of one issued by a trusted public Certificate Authority.
• Exploit mechanism: An attacker could intercept and decrypt SSL traffic if the client trusts the rogue self-signed root certificate, or if no validation occurs. For example, an attacker sets up a proxy server to intercept connections and present their own malicious certificate signed with the same self-signed root CA.
• Scope: Affected platforms include any operating system or application that uses SSL/TLS certificates for secure communication, such as Windows Server, Linux servers running Apache or Nginx, and applications using OpenSSL.

3. Detection and Assessment

You can confirm if a system is vulnerable by examining the certificate chain presented during an SSL handshake. A quick check involves inspecting the certificate details in a web browser. A thorough method uses command-line tools to decode the entire certificate chain.

• Quick checks: In a web browser, view the certificate details for the affected service and look for a root CA that is self-signed or not issued by a trusted public authority.
• Scanning: Nessus plugin ID 10425 can identify SSL certificates with untrusted root CAs as an example only.
• Logs and evidence: Examine server logs for certificate installation events, looking for entries related to the self-signed root CA. Event IDs will vary depending on the operating system and web server software.

openssl s_client -connect yourdomain.com:443 2>/dev/null | openssl x509 -noout -certfile chain.pem

4. Solution / Remediation Steps

To fix this issue, replace the self-signed root CA certificate with one issued by a trusted public Certificate Authority or ensure that use of the self-signed certificate complies with your organization’s security policies.

4.1 Preparation

• Ensure you have a valid Certificate Signing Request (CSR) for your domain. A roll back plan is to restore the original certificate files.
• A change window may be required depending on the criticality of the service, and approval from the security team should be sought.

4.2 Implementation

1. Step 1: Obtain a valid SSL certificate from a trusted public Certificate Authority (CA).
2. Step 2: Install the new certificate on the server, configuring it to use the CA-issued root chain.
3. Step 3: Restart the affected service to load the new certificate.

4.3 Config or Code Example

Before

# Example Apache configuration using self-signed certificate
SSLCertificateFile /etc/ssl/certs/self_signed.crt
SSLCertificateKeyFile /etc/ssl/private/self_signed.key

After

# Example Apache configuration using CA-issued certificate
SSLCertificateFile /etc/ssl/certs/yourdomain.crt
SSLCertificateKeyFile /etc/ssl/private/yourdomain.key
SSLCACertificateFile /etc/ssl/certs/ca_bundle.crt

4.4 Security Practices Relevant to This Vulnerability

Several security practices can help prevent this issue. Least privilege limits the impact if a certificate is compromised. Secure defaults ensure services use trusted certificates by default. A patch cadence ensures timely updates of SSL/TLS libraries and configurations.

• Practice 1: Implement least privilege to restrict access to sensitive certificate files, reducing the potential damage from compromise.
• Practice 2: Enforce secure defaults in server configuration templates to use trusted public CAs for SSL certificates.

4.5 Automation (Optional)

# Example Ansible task to update SSL certificate
- name: Update SSL Certificate
  copy:
    src: /path/to/new_certificate.crt
    dest: /etc/ssl/certs/yourdomain.crt
    owner: root
    group: root
    mode: 0644
  notify: Restart web server

5. Verification / Validation

Confirm the fix by verifying that the SSL certificate chain now uses a trusted public CA. Use command-line tools to decode the certificate and check the issuer information. Perform a service smoke test to ensure functionality is not affected.

• Post-fix check: Run `openssl s_client -connect yourdomain.com:443 2>/dev/null | openssl x509 -noout -issuer` and confirm the output shows a trusted Certificate Authority (e.g., Let’s Encrypt, DigiCert).
• Re-test: Re-run the `openssl s_client` command from step 3 to verify that the self-signed root CA is no longer present in the certificate chain.
• Smoke test: Access the affected service through a web browser and confirm that it loads correctly without any certificate errors.
• Monitoring: Monitor server logs for SSL handshake errors, looking for entries related to certificate validation failures as an example only.

openssl s_client -connect yourdomain.com:443 2>/dev/null | openssl x509 -noout -issuer

6. Preventive Measures and Monitoring

Update security baselines to include requirements for using trusted public CAs for SSL certificates, for example a CIS control or GPO setting. Add checks in CI pipelines to validate certificate authenticity during deployment. Implement a sensible patch review cycle that fits the risk.

• Baselines: Update your organization’s security baseline to require the use of trusted public CAs for SSL certificates.
• Asset and patch process: Review SSL/TLS certificates regularly as part of a vulnerability management program, with a cadence appropriate to the risk profile.

7. Risks, Side Effects, and Roll Back

Potential risks include service downtime during certificate replacement or compatibility issues with older clients. A roll back plan involves restoring the original certificate files and configuration settings.

• Risk or side effect 2: Older clients may not trust the new CA, leading to connectivity issues. Mitigation: Ensure compatibility with older