Feature Request: Direct Shared Secret Input For HS Algorithms

by SLV Team 62 views
Feature Request: Direct Shared Secret Input for HS Algorithms

Hey guys! Today, let's dive into a feature request concerning the Traefik JWT plugin and how it handles shared secrets for symmetric algorithms like HS256, HS384, and HS512. Currently, there's a limitation in how the plugin accepts these secrets, and we're going to explore why a direct input method would be a significant improvement. So, buckle up, and let's get started!

The Current Challenge with Symmetric Algorithms

When using the Traefik JWT plugin with symmetric algorithms, you'll quickly notice that it doesn't allow you to directly input the shared secret within the Keys configuration. Instead, the plugin expects either:

  • A PEM certificate or public key
  • A JWKS URL endpoint

Now, this works perfectly fine for asymmetric algorithms, where you have a public key to distribute and a private key to keep secret. But here's the catch: symmetric algorithms don't have a public key. The signing key is the shared secret. This discrepancy creates an unnecessary hurdle when configuring the plugin for HS256, HS384, or HS512.

Why This Matters

Think about it – for HS* algorithms, exposing the shared secret via a JWKS endpoint is like putting a neon sign on your treasure chest. JWKS (JSON Web Key Set) is designed to publish public keys, which are meant to be shared. It's not the right tool for distributing symmetric secrets, which, by definition, should be kept private and secure. Hosting an artificial JWKS server just to expose a static shared secret introduces unnecessary overhead and creates a potential security risk. It's like using a sledgehammer to crack a nut – overkill and potentially damaging!

Furthermore, the system already knows the shared secret. You, as the administrator, have it. So, it makes perfect sense to pass it directly in the configuration rather than jumping through hoops with JWKS endpoints. This direct approach simplifies the setup process and reduces the attack surface.

Proposed Solution: Direct Shared Secret Configuration

To address this, the proposed solution is straightforward and elegant. If the algorithm specified is HS256, HS384, or HS512, the plugin should allow a simple string input for the key. Imagine this in your configuration:

Keys:
  - "my-shared-secret"
Alg: HS256

This should be sufficient for HS-based algorithms. No need for a JWKS server, no unnecessary exposure of the secret. The plugin can directly use the provided string as the shared secret, streamlining the configuration process.

Expected Behavior

The expected behavior is quite simple: when the plugin encounters a configuration like the one above, it should recognize that the provided string is the shared secret and use it for verifying JWT signatures. This eliminates the need for a JWKS server and simplifies the overall setup.

Current Behavior

Currently, if you try to pass the secret directly this way, the plugin throws an error: "Invalid configuration, expecting a certificate, public key or JWK URL." This error message highlights the plugin's current limitation and underscores the need for the proposed feature.

Benefits of the Proposed Change

Implementing this change offers several key benefits:

  • Enhanced Security: By avoiding the need for a JWKS endpoint, you reduce the potential attack surface and keep your shared secret more secure.
  • Simplified Configuration: Passing the secret directly in the config makes the setup process much easier and less cumbersome.
  • Reduced Overhead: Eliminating the need for an artificial JWKS server reduces operational overhead and simplifies your infrastructure.
  • Backward Compatibility: The proposed change is backward compatible. It doesn't break any existing configurations and only adds new functionality.
  • Ease of Implementation: The suggested change is relatively easy to implement. It involves adding support for treating a plain string as the shared secret when the algorithm is HS256, HS384, or HS512 and the string is neither a PEM certificate nor a URL.

Suggested Implementation: Modifying ParseKeys()

The key to implementing this feature lies in the ParseKeys() function within the Traefik JWT plugin. The suggestion is to add a check within this function to determine if the algorithm is HS256, HS384, or HS512. If it is, and if the provided key string is neither a PEM certificate nor a URL, the function should treat the string as the shared secret.

This modification would allow the plugin to seamlessly handle shared secrets for symmetric algorithms, making the configuration process more intuitive and secure.

Diving Deeper: Why JWKS Doesn't Fit Symmetric Algorithms

To truly appreciate the significance of this feature request, let's delve deeper into why using JWKS for symmetric algorithms is not ideal.

JWKS is fundamentally designed for distributing public keys used in asymmetric cryptography. In asymmetric cryptography, you have a key pair: a public key and a private key. The public key can be freely distributed, allowing anyone to verify signatures made with the corresponding private key. This is perfect for scenarios where you want to authenticate messages or verify identities without sharing a secret key.

However, symmetric algorithms operate on a different principle. They use a single, shared secret key for both encryption and decryption, as well as for signing and verification. This means that anyone who has the shared secret can both create and verify signatures. There's no concept of a public key in symmetric cryptography.

The Mismatch

This fundamental difference is where the mismatch occurs. When you use JWKS for symmetric algorithms, you're essentially exposing the shared secret, which defeats the purpose of using a secret key in the first place. It's like posting your password on a public bulletin board – not a great security practice!

While it might seem convenient to use JWKS as a general-purpose key distribution mechanism, it's crucial to understand its intended use case. JWKS is designed for public keys, not for secret keys. For symmetric algorithms, a more direct and secure approach is needed.

Real-World Implications and Use Cases

Now, let's consider some real-world scenarios where this feature would be particularly beneficial. Imagine you're setting up a microservices architecture where several services need to authenticate each other using JWTs. You might choose to use HS256 for its simplicity and performance. With the current plugin behavior, you'd need to set up a JWKS server to distribute the shared secret, even though it's only used internally within your infrastructure.

With the proposed feature, you could simply configure each service with the shared secret directly, eliminating the need for the JWKS server and simplifying your deployment. This not only reduces complexity but also enhances security by keeping the shared secret within the confines of your internal network.

Another use case is in testing and development environments. When setting up a local development environment, you often want a quick and easy way to configure JWT authentication. With direct shared secret input, you can avoid the overhead of setting up a JWKS server and get your services up and running faster.

Addressing Potential Concerns

Of course, with any new feature, it's essential to consider potential concerns and address them proactively. One might argue that storing shared secrets directly in the configuration could pose a security risk if the configuration file is compromised. However, this risk is present regardless of whether you're using a JWKS server or direct input. Configuration files should always be protected and stored securely.

Moreover, best practices for secret management, such as using environment variables or dedicated secret management tools, can be applied regardless of the key input method. The proposed feature simply provides a more convenient and secure way to manage shared secrets for symmetric algorithms, without introducing new security vulnerabilities.

Conclusion: A Step Towards Simpler, More Secure JWT Configuration

In conclusion, allowing direct input of shared secrets for HS256, HS384, and HS512 algorithms in the Traefik JWT plugin is a valuable enhancement that simplifies configuration, reduces overhead, and improves security. By aligning the plugin's behavior with the fundamental principles of symmetric cryptography, this feature makes JWT authentication more accessible and easier to manage. Guys, let's hope this feature request gets some traction – it would be a fantastic addition to the plugin!