[Bug]: Root and intermediate certificates are not available at the HTTP endpoint

[ZeroClover]

Steps to Reproduce

curl http://<step ca url>/roots.pem
404 page not found

curl https://<step ca url>/roots.pem
-----BEGIN CERTIFICATE-----
...
-----END CERTIFICATE-----

Your Environment

step-ca -v
Smallstep CA/0.28.3 (linux/amd64)
Release Date: 2025-03-18T15:56:22Z

Expected Behavior

Accessing /roots.pem / /intermediates.pem via the HTTP endpoint correctly returns the corresponding certificate.

Actual Behavior

Requesting /roots.pem / /intermediates.pem on the HTTP endpoint returns 404

Additional Context

The intermediate certificates provided by the Step CA Endpoint can be used for the Certificate Authority Information Access (OID 1.3.6.1.5.5.7.1.1) CAIssuer (OID 1.3.6.1.5.5.7.48.2) field, but currently, the root and intermediate certificates are only available on HTTPS endpoints.

This does not quite align with the intended use of CAIssuer (which allows clients to download the correct intermediate certificate even if the server is not properly configured with it), nor does it conform to current industry practices: based on observations, Let's Encrypt / Google / DigiCert all provide intermediate certificates on HTTP endpoints.

Contributing

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