Allow overriding certificate hash algorithm

[bagasme]

Currently hash algorithm used to create and sign certificates is determined by hash algorithm in the CA certificate. For example, a certificate signed by default P-256 curve CA certificate uses SHA-256 and SHA-384 for certificates signed by P-384 CA.

step ca and step certificate should have an option to select desired hash algorithm (--hash). The valid values for the option shall be
SHA-256, SHA-384, SHA-512, and default (CA-dependent as before).

[tashian]

Hi @bagasme, I've created an issue from this discussion.

[maraino]

@bagasme @tashian For step certificate you should be able to create a certificate adding your preferred signatureAlgorithm for example:

{
  "subject": {{ toJson .Subject }},
  "issuer": {{ toJson .Subject }},
  "keyUsage": ["certSign", "crlSign"],
  "basicConstraints": {
    "isCA": true,
    "maxPathLen": 1
  },
  "signatureAlgorithm": "ECDSA-SHA512"
}

And in step ca you can always define a provisioner template like that:

{
  "subject": {{ toJson .Subject }},
  "sans": {{ toJson .SANs }},
{{- if typeIs "*rsa.PublicKey" .Insecure.CR.PublicKey }}
  "keyUsage": ["keyEncipherment", "digitalSignature"],
{{- else }}
  "keyUsage": ["digitalSignature"],
{{- end }}
  "extKeyUsage": ["serverAuth", "clientAuth"],
  "signatureAlgorithm": "ECDSA-SHA384"
}

I would not recommend it, but you can even define the signature algorithm from the command line if you change it to "signatureAlgorithm": {{ toJson .Insecure.User.signatureAlgorithm }}, and then just:

step ca certificate --set "signatureAlgorithm=ECDSA-SHA512" localhost localhost.crt localhost.key

Of course, it will fail if your intermediate key doesn't support it, for example, you won't be able to sign using SHA256-RSAPSS if your intermediate key is an EC key.