HSTS enablement communication and migration for next release

[Adam-D-Lewis]

Context

We've added HSTS (HTTP Strict Transport Security) support to Nebari in #3165, which will be enabled by default for cloud deployments with valid certificates (Let's Encrypt or existing certs).

Tasks Before Next Release

1. User Communication

Explain default behavior:

• Enabled by default: Cloud providers (AWS/GCP/Azure) with lets-encrypt or existing certificates
• Disabled by default: local provider or selfsigned certificates
• User override: Users can explicitly configure ingress.hsts in nebari-config.yaml

2. Configuration Migration

• During upgrade process, prompt users to add HSTS config explicitly to their nebari-config.yaml
• Allow users to decline if they want
• If accepted, add configuration block:

  ingress:
    hsts:
      enabled: true
      max_age: 31536000  # 1 year recommended for production
      include_subdomains: true
      preload: false

3. User Guidance

• Provide guidance on testing HSTS before increasing max_age
• Explain the progression: 300s (initial) → test → 31536000 (production)
• Document browser HSTS clearing procedures if needed

Related Files

• src/_nebari/stages/kubernetes_ingress/__init__.py
• src/_nebari/stages/kubernetes_ingress/template/modules/kubernetes/ingress/hsts-middleware.tf
• src/_nebari/upgrade.py

[viniciusdc]

@Adam-D-Lewis what are we using as the default max_age for HSTS?
I’m thinking about the case where a user deploys a production Nebari instance, browsers cache HSTS, and later they tear it down and redeploy. If the new deployment has any TLS/ingress misconfiguration (or temporary self-signed certs), the long max_age could cause browsers to hard-fail connections for that domain.

Are we starting with a low value (e.g. 300s) by default, or going straight to something like 1 year?

[Adam-D-Lewis]

I thought about having it go for just a short amount of time like 5 minutes, but it's set to a year currently. In the case that they misconfigure something, they can set the max age to zero in order to get the browser to forget the previous hsts configuration

[viniciusdc]

Underfull, I didn't know it was possible. I don't see any issues then with the suggested approach above.