The kolide_keyinfo table can return misleading data about public key pem files

[RebeccaMahany]

A pem file only containing a public key can show up in the kolide_keyinfo table as an unencrypted SSH key, which is misleading.

We may want to:

• Update keyidentifier to return an error if it's given a public key
• Update keyidentifier to return an error if it cannot definitively identify the pem
• Update how this table is consumed (outside the scope of this repo), if the current behavior is desired

See:

• https://github.com/kolide/launcher/blob/main/pkg/keyidentifier/keyidentifier.go#L181
• https://github.com/kolide/launcher/blob/main/pkg/osquery/table/keyinfo.go#L60

Steps to reproduce:

Run the following in your SSH keys directory:

openssl genrsa -out test.pem 1024
openssl rsa -in test.pem -pubout > test-pub.pem

Observe that both keys show up as unencrypted SSH keys.

[directionless]

Thinking a bit, I think that we should probably not return data if we can't identify it.