Document that Endpoint does not support Elliptic Curve keys for SSL

[ferullo]

What can we change to make the docs better?

Endpoint does not support Elliptic Curve keys for SSL certificates. It silently discards them (since it can't use them) which makes debugging hard. We should document that it doesn't support them, especially because Agent and Beats do.

Doc URL

This page might be a good place to mention it? https://www.elastic.co/guide/en/security/current/elastic-endpoint-deploy-reqs.html Or start a new page?

Which documentation set needs improvement?

ESS and serverless

Software version

This affects all Endpoint versions.

[ferullo]

cc @nfritts @intxgo @111andre111 @roxana-gheorghe

[intxgo]

Agree, we should document it until we add such support. Just a minor remark: since v8.16.0 it's no longer silent, policy response indicates failure "Unsupported or invalid PEM format".

[111andre111]

However that message is in my opinion still a little too vague, if we could make that message more clear, that would help a lot.

[intxgo]

However that message is in my opinion still a little too vague, if we could make that message more clear, that would help a lot.

the problem is that until endpoint can handle EC keys, it doesn't know if it's an EC key, to make the message more specific. Furthermore, we support PEM injected directly as the node value, or a path to it pointing somewhere in a local FS, that adds additional complexity with trying to give more specific messages. With the policy response UI in Kibana as it is, we don't want to inject the whole text value because PEM content is quite big and multiline