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SD-WAN Security Assessment: The First Hours

Introduction

Suppose you need to perform a security assessment of an SD-WAN solution. There are several reasons for this and one of them is selecting an SD-WAN provider or product.

A traditional SD-WAN system involves many planes, technologies, mechanisms, services, protocols and features. It has distributed and multilayered architecture. So where should you start?

This document follows JP Aumasson's approach described in a series of auditing crypto articles ([1], [2]).

The main goal of this document is to list basic sanity checks that can be used when investigating SD-WAN. We will consider general checks that can be applied to any SD-WAN system.

SD-WAN Security Assessment Checklist

Common

  1. What third-party components and libraries are used? How secure are these? Are the components using their latest versions?
  2. Run lynis tool on each node and assess hardening level.
  3. Run a host-based vulnerability scanner (vulners, LibScanner, etc.) and assess patch management level.
  4. Run a web vulnerability scanner (e.g., Burp Suite, Acunetix, etc.) against a web management interface.

Architecture

  1. Is a vendor-controlled cloud management interface used within the architecture?

Zero Touch Provisioning

  1. How does a network device get its initial configuration?
  2. How does a network device discover a controller, orchestrator and other entities?
  3. How do network devices, the controller and the orchestrator authenticate each other?
  4. How trust is provisioned and what mechanisms are used? One-time tokens, X.509 certificates, login and password, pre-shared keys?
  5. How do re-discovering or re-joining mechanisms work?

Cryptography

  1. Which cryptographic protocols and implementations are used on the dataplane?
  2. Which cryptographic protocols and implementations are used on the controlplane?
  3. Are AEAD ciphers supported?
  4. How key management is implemented?
  5. How consistent are the security levels of the various protocols and primitives?
  6. Look for legacy primitives like DES, TripleDES, RC4, MD5, SHA1 or custom primitives.
  7. Is it possible to control cryptographic mechanisms (e.g., enable TLS 1.3 only, disable unwanted ciphers, etc.)?
  8. Run a TLS scanner (e.g., testssl.sh, SSL Labs server scanner, sslyze, etc.) against TLS-enabled interfaces and assess the results.
  9. Run an SSH scanner (e.g., ssh_scan) against SSH-enabled interfaces.
  10. Which type of PKI is used? Public or private?

Secure Communications

  1. Which protocols are used between orchestrator, controller, and edge devices? Are they secured?
  2. How SD-WAN entities do authenticate each other?
  3. Run WireShark on each node (orchestrator, controller, edge router), review traffic and check whether unencrypted sensitive packets are sent.
  4. Do the chosen protocols and primitives provide the security required by your threat model?
  5. Is RSA key exchange used?
  6. Where and how secrets (e.g., private keys, pre-shared keys, tokens) are stored?
  7. Check whether the same hardcoded certificate is used on different deployments.
  8. Is a key renewal mechanism supported on control channels?

Web Management Interface

  1. Check protection mechanisms against CSRF attacks.
  2. Check HTTPS supporting and web hardening mechanisms: secure headers, content-security policy, CORS headers.
  3. Test all HTTP services against Slow HTTP DoS attacks.
  4. Are cryptography secrets accessible via the Web interface?
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