Table of Contents

RADIUS PAP Security

Overview

The Password Authentication Protocol (PAP) is a simple authentication protocol commonly used in environments such as VPNs or NAS (Network Access Servers). When credentials are transmitted using PAP, they rely on the underlying security of the network and additional layers of encryption to prevent interception and misuse.

Typically, when PAP is used with VPNs or NAS, a secure tunnel is established first using protocols like SSTP (SSL) or L2TP (IPsec). This ensures that the credentials are protected while being transmitted over the public network. Once the VPN/NAS receives the user credentials, it forwards them to the PhenixID MFA Server. At this stage, the credentials are encrypted using the RADIUS shared secret as the encryption key. For further protection, network administrators often segment this traffic to isolate it from other network components.

While PAP lacks native encryption for credentials, these layered security measures help mitigate its inherent vulnerabilities, making it a viable option in controlled and secure environments.

Best Practices

To maintain the highest level of security when using RADIUS PAP, PhenixID recommends following these best practices:

Use Strong Shared Secrets

  • A strong shared secret is critical to securing the communication between the VPN/NAS and the PhenixID MFA Server.
  • Treat the shared secret like a super-user password—keep it complex, unique, and confidential.
  • Avoid using easily guessable secrets or reusing secrets across multiple systems.

Unique Shared Secrets Per Endpoint

  • Assign a unique shared secret to each VPN/NAS endpoint that connects to the PhenixID MFA Server.
  • This ensures that even if a shared secret is compromised for one endpoint, the others remain secure.
  • It also simplifies troubleshooting and auditing by clearly identifying traffic from specific endpoints.

Network Segmentation

  • Isolate RADIUS traffic from any networks accessible to end users. This prevents potential attackers from intercepting or tampering with the traffic.
  • Use dedicated VLANs or firewalls to restrict access to the network segments handling RADIUS communication.
  • Ensure only trusted devices and systems have access to these segments.

Secure the Tunnel

  • Use strong encryption protocols like SSTP or L2TP with IPsec for the secure tunnel between the client and the VPN/NAS.
  • Ensure that VPN configurations use modern encryption standards, such as AES, to protect the initial communication.

Monitor and Audit Traffic

  • Regularly monitor RADIUS traffic for anomalies, such as unexpected endpoints or failed authentication attempts.
  • Implement logging on both the VPN/NAS and PhenixID MFA Server to track access and troubleshoot issues.
  • Periodically audit the RADIUS configuration, including shared secrets and allowed endpoints.

Restrict Authentication Methods

  • Avoid enabling PAP unless absolutely necessary. Where possible, use more secure authentication methods like CHAP or EAP.
  • If PAP is required, ensure the network infrastructure adheres to the highest security standards outlined above.

Update and Patch Systems

  • Keep the VPN/NAS and PhenixID MFA Server updated with the latest security patches.
  • Regularly review vendor recommendations for securing RADIUS and PAP implementations.

Security Implications of PAP

While PAP is widely used due to its simplicity and compatibility, it has inherent weaknesses:

  • No Native Encryption: PAP transmits credentials in plaintext unless secured by an external encryption mechanism, such as SSTP or IPsec.
  • Vulnerability to Replay Attacks: Without strong network protections, intercepted credentials could be reused.
  • Dependence on External Layers: PAP relies entirely on the security of the underlying transport and the RADIUS shared secret.

Despite these limitations, when combined with strong tunneling protocols, robust shared secrets, and proper network isolation, PAP can be deployed securely in controlled environments.

Summary

By following these best practices, you can mitigate the risks associated with using RADIUS PAP and ensure a secure deployment. While PAP's simplicity makes it a popular choice, its inherent vulnerabilities necessitate strict security measures. Always prioritize strong shared secrets, endpoint isolation, and secure tunneling to protect user credentials and maintain the integrity of your network.

RADIUS Password