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cmd/k8s-operator,k8s-operator/sessionrecording: support recording kubectl exec sessions over WebSockets (#12947)

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cmd/k8s-operator,k8s-operator/sessionrecording: support recording WebSocket sessions

Kubernetes currently supports two streaming protocols, SPDY and WebSockets.
WebSockets are replacing SPDY, see
https://github.com/kubernetes/enhancements/issues/4006.
We were currently only supporting SPDY, erroring out if session
was not SPDY and relying on the kube's built-in SPDY fallback.

This PR:

- adds support for parsing contents of 'kubectl exec' sessions streamed
over WebSockets

- adds logic to distinguish 'kubectl exec' requests for a SPDY/WebSockets
sessions and call the relevant handler

Updates tailscale/corp#19821

Signed-off-by: Irbe Krumina <irbe@tailscale.com>
Co-authored-by: Tom Proctor <tomhjp@users.noreply.github.com>
This commit is contained in:
Irbe Krumina
2024-08-14 19:57:50 +03:00
committed by GitHub
parent 4c2e978f1e
commit a15ff1bade
13 changed files with 1270 additions and 73 deletions
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52
cmd/k8s-operator/proxy.go
View File

@@ -22,9 +22,8 @@ import (
"k8s.io/client-go/transport"
"tailscale.com/client/tailscale"
"tailscale.com/client/tailscale/apitype"
kubesessionrecording "tailscale.com/k8s-operator/sessionrecording"
ksr "tailscale.com/k8s-operator/sessionrecording"
tskube "tailscale.com/kube"
"tailscale.com/sessionrecording"
"tailscale.com/tailcfg"
"tailscale.com/tsnet"
"tailscale.com/util/clientmetric"
@@ -168,7 +167,8 @@ func runAPIServerProxy(ts *tsnet.Server, rt http.RoundTripper, log *zap.SugaredL
mux := http.NewServeMux()
mux.HandleFunc("/", ap.serveDefault)
mux.HandleFunc("/api/v1/namespaces/{namespace}/pods/{pod}/exec", ap.serveExec)
mux.HandleFunc("POST /api/v1/namespaces/{namespace}/pods/{pod}/exec", ap.serveExecSPDY)
mux.HandleFunc("GET /api/v1/namespaces/{namespace}/pods/{pod}/exec", ap.serveExecWS)
hs := &http.Server{
// Kubernetes uses SPDY for exec and port-forward, however SPDY is
@@ -209,9 +209,19 @@ func (ap *apiserverProxy) serveDefault(w http.ResponseWriter, r *http.Request) {
ap.rp.ServeHTTP(w, r.WithContext(whoIsKey.WithValue(r.Context(), who)))
}
// serveExec serves 'kubectl exec' requests, optionally configuring the kubectl
// exec sessions to be recorded.
func (ap *apiserverProxy) serveExec(w http.ResponseWriter, r *http.Request) {
// serveExecSPDY serves 'kubectl exec' requests for sessions streamed over SPDY,
// optionally configuring the kubectl exec sessions to be recorded.
func (ap *apiserverProxy) serveExecSPDY(w http.ResponseWriter, r *http.Request) {
ap.execForProto(w, r, ksr.SPDYProtocol)
}
// serveExecWS serves 'kubectl exec' requests for sessions streamed over WebSocket,
// optionally configuring the kubectl exec sessions to be recorded.
func (ap *apiserverProxy) serveExecWS(w http.ResponseWriter, r *http.Request) {
ap.execForProto(w, r, ksr.WSProtocol)
}
func (ap *apiserverProxy) execForProto(w http.ResponseWriter, r *http.Request, proto ksr.Protocol) {
who, err := ap.whoIs(r)
if err != nil {
ap.authError(w, err)
@@ -227,15 +237,17 @@ func (ap *apiserverProxy) serveExec(w http.ResponseWriter, r *http.Request) {
ap.rp.ServeHTTP(w, r.WithContext(whoIsKey.WithValue(r.Context(), who)))
return
}
kubesessionrecording.CounterSessionRecordingsAttempted.Add(1) // at this point we know that users intended for this session to be recorded
ksr.CounterSessionRecordingsAttempted.Add(1) // at this point we know that users intended for this session to be recorded
if !failOpen && len(addrs) == 0 {
msg := "forbidden: 'kubectl exec' session must be recorded, but no recorders are available."
ap.log.Error(msg)
http.Error(w, msg, http.StatusForbidden)
return
}
if r.Method != "POST" || r.Header.Get("Upgrade") != "SPDY/3.1" {
msg := "'kubectl exec' session recording is configured, but the request is not over SPDY. Session recording is currently only supported for SPDY based clients"
wantsHeader := upgradeHeaderForProto[proto]
if h := r.Header.Get("Upgrade"); h != wantsHeader {
msg := fmt.Sprintf("[unexpected] unable to verify that streaming protocol is %s, wants Upgrade header %q, got: %q", proto, wantsHeader, h)
if failOpen {
msg = msg + "; failure mode is 'fail open'; continuing session without recording."
ap.log.Warn(msg)
@@ -247,9 +259,22 @@ func (ap *apiserverProxy) serveExec(w http.ResponseWriter, r *http.Request) {
http.Error(w, msg, http.StatusForbidden)
return
}
spdyH := kubesessionrecording.New(ap.ts, r, who, w, r.PathValue("pod"), r.PathValue("namespace"), kubesessionrecording.SPDYProtocol, addrs, failOpen, sessionrecording.ConnectToRecorder, ap.log)
ap.rp.ServeHTTP(spdyH, r.WithContext(whoIsKey.WithValue(r.Context(), who)))
opts := ksr.HijackerOpts{
Req: r,
W: w,
Proto: proto,
TS: ap.ts,
Who: who,
Addrs: addrs,
FailOpen: failOpen,
Pod: r.PathValue("pod"),
Namespace: r.PathValue("namespace"),
Log: ap.log,
}
h := ksr.New(opts)
ap.rp.ServeHTTP(h, r.WithContext(whoIsKey.WithValue(r.Context(), who)))
}
func (h *apiserverProxy) addImpersonationHeadersAsRequired(r *http.Request) {
@@ -382,3 +407,8 @@ func determineRecorderConfig(who *apitype.WhoIsResponse) (failOpen bool, recorde
}
return failOpen, recorderAddresses, nil
}
var upgradeHeaderForProto = map[ksr.Protocol]string{
ksr.SPDYProtocol: "SPDY/3.1",
ksr.WSProtocol: "websocket",
}