auth: allow nodes to create tokones for svcaccts of pods

plugin/pkg/auth/authorizer/node/graph.go

@@ -107,16 +107,18 @@ const (
 	pvVertexType
 	secretVertexType
 	vaVertexType
+	serviceAccountVertexType
 )
 
 var vertexTypes = map[vertexType]string{
-	configMapVertexType: "configmap",
-	nodeVertexType:      "node",
-	podVertexType:       "pod",
-	pvcVertexType:       "pvc",
-	pvVertexType:        "pv",
-	secretVertexType:    "secret",
-	vaVertexType:        "volumeattachment",
+	configMapVertexType:      "configmap",
+	nodeVertexType:           "node",
+	podVertexType:            "pod",
+	pvcVertexType:            "pvc",
+	pvVertexType:             "pv",
+	secretVertexType:         "secret",
+	vaVertexType:             "volumeattachment",
+	serviceAccountVertexType: "serviceAccount",
 }
 
 // must be called under a write lock
@@ -204,6 +206,7 @@ func (g *Graph) deleteVertex_locked(vertexType vertexType, namespace, name strin
 //   secret    -> pod
 //   configmap -> pod
 //   pvc       -> pod
+//   svcacct   -> pod
 func (g *Graph) AddPod(pod *api.Pod) {
 	g.lock.Lock()
 	defer g.lock.Unlock()
@@ -213,6 +216,14 @@ func (g *Graph) AddPod(pod *api.Pod) {
 	nodeVertex := g.getOrCreateVertex_locked(nodeVertexType, "", pod.Spec.NodeName)
 	g.graph.SetEdge(newDestinationEdge(podVertex, nodeVertex, nodeVertex))
 
+	// TODO(mikedanese): If the pod doesn't mount the service account secrets,
+	// should the node still get access to the service account?
+	//
+	// ref https://github.com/kubernetes/kubernetes/issues/58790
+	if len(pod.Spec.ServiceAccountName) > 0 {
+		g.graph.SetEdge(newDestinationEdge(g.getOrCreateVertex_locked(serviceAccountVertexType, pod.Namespace, pod.Spec.ServiceAccountName), podVertex, nodeVertex))
+	}
+
 	podutil.VisitPodSecretNames(pod, func(secret string) bool {
 		g.graph.SetEdge(newDestinationEdge(g.getOrCreateVertex_locked(secretVertexType, pod.Namespace, secret), podVertex, nodeVertex))
 		return true

plugin/pkg/auth/authorizer/node/node_authorizer.go

@@ -70,6 +70,7 @@ var (
 	pvcResource       = api.Resource("persistentvolumeclaims")
 	pvResource        = api.Resource("persistentvolumes")
 	vaResource        = storageapi.Resource("volumeattachments")
+	svcAcctResource   = api.Resource("serviceaccounts")
 )
 
 func (r *NodeAuthorizer) Authorize(attrs authorizer.Attributes) (authorizer.Decision, string, error) {
@@ -106,6 +107,11 @@ func (r *NodeAuthorizer) Authorize(attrs authorizer.Attributes) (authorizer.Deci
 				return r.authorizeGet(nodeName, vaVertexType, attrs)
 			}
 			return authorizer.DecisionNoOpinion, fmt.Sprintf("disabled by feature gate %s", features.CSIPersistentVolume), nil
+		case svcAcctResource:
+			if r.features.Enabled(features.TokenRequest) {
+				return r.authorizeCreateToken(nodeName, serviceAccountVertexType, attrs)
+			}
+			return authorizer.DecisionNoOpinion, fmt.Sprintf("disabled by feature gate %s", features.TokenRequest), nil
 		}
 	}
 
@@ -165,6 +171,31 @@ func (r *NodeAuthorizer) authorize(nodeName string, startingType vertexType, att
 	return authorizer.DecisionAllow, "", nil
 }
 
+// authorizeCreateToken authorizes "create" requests to serviceaccounts 'token'
+// subresource of pods running on a node
+func (r *NodeAuthorizer) authorizeCreateToken(nodeName string, startingType vertexType, attrs authorizer.Attributes) (authorizer.Decision, string, error) {
+	if attrs.GetVerb() != "create" || len(attrs.GetName()) == 0 {
+		glog.V(2).Infof("NODE DENY: %s %#v", nodeName, attrs)
+		return authorizer.DecisionNoOpinion, "can only create tokens for individual service accounts", nil
+	}
+
+	if attrs.GetSubresource() != "token" {
+		glog.V(2).Infof("NODE DENY: %s %#v", nodeName, attrs)
+		return authorizer.DecisionNoOpinion, "can only create token subresource of serviceaccount", nil
+	}
+
+	ok, err := r.hasPathFrom(nodeName, startingType, attrs.GetNamespace(), attrs.GetName())
+	if err != nil {
+		glog.V(2).Infof("NODE DENY: %v", err)
+		return authorizer.DecisionNoOpinion, "no path found to object", nil
+	}
+	if !ok {
+		glog.V(2).Infof("NODE DENY: %q %#v", nodeName, attrs)
+		return authorizer.DecisionNoOpinion, "no path found to object", nil
+	}
+	return authorizer.DecisionAllow, "", nil
+}
+
 // hasPathFrom returns true if there is a directed path from the specified type/namespace/name to the specified Node
 func (r *NodeAuthorizer) hasPathFrom(nodeName string, startingType vertexType, startingNamespace, startingName string) (bool, error) {
 	r.graph.lock.RLock()

plugin/pkg/auth/authorizer/node/node_authorizer_test.go

@@ -38,6 +38,8 @@ import (
 var (
 	csiEnabledFeature  = utilfeature.NewFeatureGate()
 	csiDisabledFeature = utilfeature.NewFeatureGate()
+	trEnabledFeature   = utilfeature.NewFeatureGate()
+	trDisabledFeature  = utilfeature.NewFeatureGate()
 )
 
 func init() {
@@ -47,6 +49,12 @@ func init() {
 	if err := csiDisabledFeature.Add(map[utilfeature.Feature]utilfeature.FeatureSpec{features.CSIPersistentVolume: {Default: false}}); err != nil {
 		panic(err)
 	}
+	if err := trEnabledFeature.Add(map[utilfeature.Feature]utilfeature.FeatureSpec{features.TokenRequest: {Default: true}}); err != nil {
+		panic(err)
+	}
+	if err := trDisabledFeature.Add(map[utilfeature.Feature]utilfeature.FeatureSpec{features.TokenRequest: {Default: false}}); err != nil {
+		panic(err)
+	}
 }
 
 func TestAuthorizer(t *testing.T) {
@@ -152,6 +160,36 @@ func TestAuthorizer(t *testing.T) {
 			features: csiEnabledFeature,
 			expect:   authorizer.DecisionAllow,
 		},
+		{
+			name:     "allowed svcacct token create - feature enabled",
+			attrs:    authorizer.AttributesRecord{User: node0, ResourceRequest: true, Verb: "create", Resource: "serviceaccounts", Subresource: "token", Name: "svcacct0-node0", Namespace: "ns0"},
+			features: trEnabledFeature,
+			expect:   authorizer.DecisionAllow,
+		},
+		{
+			name:     "disallowed svcacct token create - serviceaccount not attached to node",
+			attrs:    authorizer.AttributesRecord{User: node0, ResourceRequest: true, Verb: "create", Resource: "serviceaccounts", Subresource: "token", Name: "svcacct0-node1", Namespace: "ns0"},
+			features: trEnabledFeature,
+			expect:   authorizer.DecisionNoOpinion,
+		},
+		{
+			name:     "disallowed svcacct token create - feature disabled",
+			attrs:    authorizer.AttributesRecord{User: node0, ResourceRequest: true, Verb: "create", Resource: "serviceaccounts", Subresource: "token", Name: "svcacct0-node0", Namespace: "ns0"},
+			features: trDisabledFeature,
+			expect:   authorizer.DecisionNoOpinion,
+		},
+		{
+			name:     "disallowed svcacct token create - no subresource",
+			attrs:    authorizer.AttributesRecord{User: node0, ResourceRequest: true, Verb: "create", Resource: "serviceaccounts", Name: "svcacct0-node0", Namespace: "ns0"},
+			features: trEnabledFeature,
+			expect:   authorizer.DecisionNoOpinion,
+		},
+		{
+			name:     "disallowed svcacct token create - non create",
+			attrs:    authorizer.AttributesRecord{User: node0, ResourceRequest: true, Verb: "update", Resource: "serviceaccounts", Subresource: "token", Name: "svcacct0-node0", Namespace: "ns0"},
+			features: trEnabledFeature,
+			expect:   authorizer.DecisionNoOpinion,
+		},
 	}
 
 	for _, tc := range tests {
@@ -459,6 +497,7 @@ func generate(opts sampleDataOpts) ([]*api.Pod, []*api.PersistentVolume, []*stor
 			pod.Namespace = fmt.Sprintf("ns%d", p%opts.namespaces)
 			pod.Name = fmt.Sprintf("pod%d-%s", p, nodeName)
 			pod.Spec.NodeName = nodeName
+			pod.Spec.ServiceAccountName = fmt.Sprintf("svcacct%d-%s", p, nodeName)
 
 			for i := 0; i < opts.uniqueSecretsPerPod; i++ {
 				pod.Spec.Volumes = append(pod.Spec.Volumes, api.Volume{VolumeSource: api.VolumeSource{