Avoid nil user special-casing in unsecured endpoint

pkg/kubeapiserver/server/BUILD

@@ -13,6 +13,7 @@ go_library(
     tags = ["automanaged"],
     deps = [
         "//vendor:github.com/golang/glog",
+        "//vendor:k8s.io/apiserver/pkg/authentication/user",
         "//vendor:k8s.io/apiserver/pkg/endpoints/filters",
         "//vendor:k8s.io/apiserver/pkg/endpoints/request",
         "//vendor:k8s.io/apiserver/pkg/server",

pkg/kubeapiserver/server/insecure_handler.go

@@ -22,6 +22,7 @@ import (
 
 	"github.com/golang/glog"
 
+	"k8s.io/apiserver/pkg/authentication/user"
 	genericapifilters "k8s.io/apiserver/pkg/endpoints/filters"
 	apirequest "k8s.io/apiserver/pkg/endpoints/request"
 	"k8s.io/apiserver/pkg/server"
@@ -35,6 +36,7 @@ import (
 
 func BuildInsecureHandlerChain(apiHandler http.Handler, c *server.Config) http.Handler {
 	handler := genericapifilters.WithAudit(apiHandler, c.RequestContextMapper, c.AuditWriter)
+	handler = genericapifilters.WithAuthentication(handler, c.RequestContextMapper, insecureSuperuser{}, nil)
 	handler = genericfilters.WithCORS(handler, c.CorsAllowedOriginList, nil, nil, nil, "true")
 	handler = genericfilters.WithPanicRecovery(handler, c.RequestContextMapper)
 	handler = genericfilters.WithTimeoutForNonLongRunningRequests(handler, c.RequestContextMapper, c.LongRunningFunc)
@@ -111,3 +113,15 @@ func serveInsecurely(insecureServingInfo *InsecureServingInfo, insecureHandler h
 	_, err = server.RunServer(insecureServer, insecureServingInfo.BindNetwork, stopCh)
 	return err
 }
+
+// insecureSuperuser implements authenticator.Request to always return a superuser.
+// This is functionally equivalent to skipping authentication and authorization,
+// but allows apiserver code to stop special-casing a nil user to skip authorization checks.
+type insecureSuperuser struct{}
+
+func (insecureSuperuser) AuthenticateRequest(req *http.Request) (user.Info, bool, error) {
+	return &user.DefaultInfo{
+		Name:   "system:unsecured",
+		Groups: []string{user.SystemPrivilegedGroup, user.AllAuthenticated},
+	}, true, nil
+}

pkg/registry/rbac/escalation_check.go

@@ -29,9 +29,7 @@ import (
 func EscalationAllowed(ctx genericapirequest.Context) bool {
 	u, ok := genericapirequest.UserFrom(ctx)
 	if !ok {
-		// the only way to be without a user is to either have no authenticators by explicitly saying that's your preference
-		// or to be connecting via the insecure port, in which case this logically doesn't apply
-		return true
+		return false
 	}
 
 	// system:masters is special because the API server uses it for privileged loopback connections

plugin/pkg/admission/security/podsecuritypolicy/admission.go

@@ -288,8 +288,7 @@ func getMatchingPolicies(lister extensionslisters.PodSecurityPolicyLister, user
 	}
 
 	for _, constraint := range list {
-		// if no user info exists then the API is being hit via the unsecured port. In this case authorize the request.
-		if user == nil || authorizedForPolicy(user, namespace, constraint, authz) || authorizedForPolicy(sa, namespace, constraint, authz) {
+		if authorizedForPolicy(user, namespace, constraint, authz) || authorizedForPolicy(sa, namespace, constraint, authz) {
 			matchedPolicies = append(matchedPolicies, constraint)
 		}
 	}

plugin/pkg/admission/security/podsecuritypolicy/admission_test.go

@@ -1612,25 +1612,34 @@ func TestGetMatchingPolicies(t *testing.T) {
 			},
 			expectedPolicies: sets.NewString("policy1", "policy2", "policy4", "policy5"),
 		},
-		"policies are allowed for nil user info": {
-			user:    nil,
-			sa:      &user.DefaultInfo{Name: "sa"},
-			ns:      "test",
-			allowed: map[string]map[string]map[string]bool{}, // authorizer not consulted
+		"policies are not allowed for nil user info": {
+			user: nil,
+			sa:   &user.DefaultInfo{Name: "sa"},
+			ns:   "test",
+			allowed: map[string]map[string]map[string]bool{
+				"sa": {
+					"test": {"policy1": true},
+				},
+				"user": {
+					"test": {"policy2": true},
+				},
+			},
 			inPolicies: []*extensions.PodSecurityPolicy{
 				policyWithName("policy1"),
 				policyWithName("policy2"),
 				policyWithName("policy3"),
 			},
-			// all policies are allowed regardless of the permissions when user info is nil
-			// (ie. a request hitting the unsecure port)
-			expectedPolicies: sets.NewString("policy1", "policy2", "policy3"),
+			// only the policies for the sa are allowed when user info is nil
+			expectedPolicies: sets.NewString("policy1"),
 		},
 		"policies are not allowed for nil sa info": {
 			user: &user.DefaultInfo{Name: "user"},
 			sa:   nil,
 			ns:   "test",
 			allowed: map[string]map[string]map[string]bool{
+				"sa": {
+					"test": {"policy1": true},
+				},
 				"user": {
 					"test": {"policy2": true},
 				},
@@ -1643,6 +1652,26 @@ func TestGetMatchingPolicies(t *testing.T) {
 			// only the policies for the user are allowed when sa info is nil
 			expectedPolicies: sets.NewString("policy2"),
 		},
+		"policies are not allowed for nil sa and user info": {
+			user: nil,
+			sa:   nil,
+			ns:   "test",
+			allowed: map[string]map[string]map[string]bool{
+				"sa": {
+					"test": {"policy1": true},
+				},
+				"user": {
+					"test": {"policy2": true},
+				},
+			},
+			inPolicies: []*extensions.PodSecurityPolicy{
+				policyWithName("policy1"),
+				policyWithName("policy2"),
+				policyWithName("policy3"),
+			},
+			// no policies are allowed if sa and user are both nil
+			expectedPolicies: sets.NewString(),
+		},
 	}
 	for k, v := range tests {
 		informerFactory := informers.NewSharedInformerFactory(nil, controller.NoResyncPeriodFunc())