https://github.com/linkerd/linkerd2/pull/2521 introduces an "Identity"
controller, but there is no way to include it in linkerd installation.
This change alters the `install` flow as follows:
- An Identity service is _always_ installed;
- Issuer credentials may be specified via the CLI;
- If no Issuer credentials are provided, they are generated each time `install` is called.
- Proxies are NOT configured to use the identity service.
- It's possible to override the credential generation logic---especially
for tests---via install options that can be configured via the CLI.
This change introduces a new Identity service implementation for the
`io.linkerd.proxy.identity.Identity` gRPC service.
The `pkg/identity` contains a core, abstract implementation of the service
(generic over both the CA and (Kubernetes) Validator interfaces).
`controller/identity` includes a concrete implementation that uses the
Kubernetes TokenReview API to validate serviceaccount tokens when
issuing certificates.
This change does **NOT** alter installation or runtime to include the
identity service. This will be included in a follow-up.
In preparation for creating an Identity service that can chain off of an
existing CA, it's necessary to both (1) be able to create an
intermediate CA that can be used by the identity service and (2) be able
to load a CA from existing key material.
This changes the public API of the `tls` package to deal in actual key
types (rather than opaque blobs) and provides a set of helpers that can
be used to convert these credentials between common formats.
Oliver Gould