As part of this change, we ensure that the SAN extensions are marked as
critical when the subject is empty so that AWS PCA tolerates the loss of
common names well and continues to function as a Connect CA provider.
Parts of this currently hack around a bug in crypto/x509 and can be
removed after https://go-review.googlesource.com/c/go/+/329129 lands in
a Go release.
Note: the AWS PCA tests do not run automatically, but the following
passed locally for me:
ENABLE_AWS_PCA_TESTS=1 go test ./agent/connect/ca -run TestAWS
The fallback method would still work but it would get into a state where it would let the certificate expire for 10s before getting a new one. And the new one used the less secure RPC endpoint.
This is also a pretty large refactoring of the auto encrypt code. I was going to write some tests around the certificate monitoring but it was going to be impossible to get a TestAgent configured in such a way that I could write a test that ran in less than an hour or two to exercise the functionality.
Moving the certificate monitoring into its own package will allow for dependency injection and in particular mocking the cache types to control how it hands back certificates and how long those certificates should live. This will allow for exercising the main loop more than would be possible with it coupled so tightly with the Agent.
