### Summary
As an initial attempt to secure the connection from clients to the gRPC tap
server on the tap Pod, the tap `addr` only listened on localhost.
As @adleong pointed out #3257, this was not actually secure because the inbound
proxy would establish a connection to localhost anyways.
This change removes the gRPC tap server listener and changes `TapByResource`
requests to interface with the server object directly.
From this, we know that all `TapByResourceRequests` have gone through the tap
APIServer and thus authorized by RBAC.
### Details
[NewAPIServer](ef90e0184f/controller/tap/apiserver.go (L25-L26)) now takes a [GRPCTapServer](f6362dfa80/controller/tap/server.go (L33-L34)) instead of a `pb.TapClient` so that
`TapByResource` requests can interact directly with the [TapByResource](f6362dfa80/controller/tap/server.go (L49-L50)) method.
`GRPCTapServer.TapByResource` now makes a private [grpcTapServer](ef90e0184f/controller/tap/handlers.go (L373-L374)) that satisfies
the [tap.TapServer](https://godoc.org/github.com/linkerd/linkerd2/controller/gen/controller/tap#TapServer) interface. Because this interface is satisfied, we can interact
with the tap server methods without spawning an additional listener.
Signed-off-by: Kevin Leimkuhler <kleimkuhler@icloud.com>
The Tap Service enabled tapping of any meshed pod, regardless of user
privilege.
This change introduces a new Tap APIService. Kubernetes provides
authentication and authorization of Tap requests, and then forwards
requests to a new Tap APIServer, which implements a Kubernetes
aggregated APIServer. The Tap APIServer authenticates the client TLS
from Kubernetes, and authorizes the user via a SubjectAccessReview.
This change also modifies the `linkerd tap` command to make requests
against the new APIService.
The Tap APIService implements these Kubernetes-style endpoints:
POST /apis/tap.linkerd.io/v1alpha1/watch/namespaces/:ns/tap
POST /apis/tap.linkerd.io/v1alpha1/watch/namespaces/:ns/:res/:name/tap
GET /apis
GET /apis/tap.linkerd.io
GET /apis/tap.linkerd.io/v1alpha1
GET /healthz
GET /healthz/log
GET /healthz/ping
GET /metrics
GET /openapi/v2
GET /version
Users authorize to the new `tap.linkerd.io/v1alpha1` via RBAC. Only the
`watch` verb is supported. Access is also available via subresources
such as `deployments/tap` and `pods/tap`.
This change introduces the following resources into the default Linkerd
install:
- Global
- APIService/v1alpha1.tap.linkerd.io
- ClusterRoleBinding/linkerd-linkerd-tap-auth-delegator
- `linkerd` namespace:
- Secret/linkerd-tap-tls
- `kube-system` namespace:
- RoleBinding/linkerd-linkerd-tap-auth-reader
Tasks not covered by this PR:
- `linkerd top`
- `linkerd dashboard`
- `linkerd profile --tap`
- removal of the unauthenticated tap controller
Fixes#2725, #3162, #3172
Signed-off-by: Andrew Seigner <siggy@buoyant.io>
Kevin Leimkuhler
Andrew Seigner