* Change CA Configure struct to pass Datacenter through
* Remove connect/ca/plugin as we don't have immediate plans to use it.
We still intend to one day but there are likely to be several changes to the CA provider interface before we do so it's better to rebuild from history when we do that work properly.
* Rename PrimaryDC; fix endpoint in secondary DCs
* Support Connect CAs that can't cross sign
* revert spurios mod changes from make tools
* Add log warning when forcing CA rotation
* Fixup SupportsCrossSigning to report errors and work with Plugin interface (fixes tests)
* Fix failing snake_case test
* Remove misleading comment
* Revert "Remove misleading comment"
This reverts commit bc4db9cabed8ad5d0e39b30e1fe79196d248349c.
* Remove misleading comment
* Regen proto files messed up by rebase
* pass logger through to provider
* test for proper operation of NeedsLogger
* remove public testServer function
* Ooops actually set the logger in all the places we need it - CA config set wasn't and causing segfault
* Fix all the other places in tests where we set the logger
* Allow CA Providers to persist some state
* Update CA provider plugin interface
* Fix plugin stubs to match provider changes
* Update agent/connect/ca/provider.go
Co-Authored-By: R.B. Boyer <rb@hashicorp.com>
* Cleanup review comments
This adds the `agent/connect/ca/plugin` library for consuming/serving Connect CA providers as [go-plugin](https://github.com/hashicorp/go-plugin) plugins. This **does not** wire this up in any way to Consul itself, so this will not enable using these plugins yet.
## Why?
We want to enable CA providers to be pluggable without modifying Consul so that any CA or PKI system can potentially back the Connect certificates. This CA system may also be used in the future for easier bootstrapping and internal cluster security.
### go-plugin
The benefit of `go-plugin` is that for the plugin consumer, the fact that the interface implementation is communicating over multi-process RPC is invisible. Internals of Consul will continue to just use `ca.Provider` interface implementations as if they're local. For plugin _authors_, they simply have to implement the interface. The network/transport/process management issues are handled by go-plugin itself.
The CA provider plugins support both `net/rpc` and gRPC transports. This enables easy authoring in any language. go-plugin handles the actual protocol handshake and connection. This is just a feature of go-plugin.
`go-plugin` is already in production use for years by Packer, Terraform, Nomad, Vault, and Sentinel. We've shown stability for both desktop and server-side software. It is very mature.
## Implementation Details
### `map[string]interface{}`
The `Configure` method passes a `map[string]interface{}`. This map contains only Go primitives and containers of primitives (no funcs, chans, etc.). For `net/rpc` we encode as-is using Gob. For gRPC we marshal to JSON and transmit as a `bytes` type. This is the same approach we take with Vault and other software.
Note that this is just the transport protocol, the end software views it fully decoded.
### `x509.Certificate` and `CertificateRequest`
We transmit the raw ASN.1 bytes and decode on the other side. Unit tests are verifying we get the same cert/csrs across the wire.
### Testing
`go-plugin` exposes test helpers that enable testing the full plugin RPC over real loopback network connections. We test all endpoints for success and error for both `net/rpc` and gRPC.
### Vendoring
This PR doesn't introduce vendoring for two reasons:
1. @banks's `f-envoy` branch introduces a lot of these and I didn't want conflict.
2. The library isn't actually used yet so it doesn't introduce compile-time errors (it does introduce test errors).
## Next Steps
With this in place, we need to figure out the proper way to actually hook these up to Consul, load them, etc. This discussion can happen elsewhere, since regardless of approach this plugin library implementation is the exact same.
