Add Certificate signerName admission plugins

plugin/BUILD

@@ -14,6 +14,7 @@ filegroup(
         "//plugin/pkg/admission/admit:all-srcs",
         "//plugin/pkg/admission/alwayspullimages:all-srcs",
         "//plugin/pkg/admission/antiaffinity:all-srcs",
+        "//plugin/pkg/admission/certificates:all-srcs",
         "//plugin/pkg/admission/defaulttolerationseconds:all-srcs",
         "//plugin/pkg/admission/deny:all-srcs",
         "//plugin/pkg/admission/eventratelimit:all-srcs",

plugin/pkg/admission/certificates/BUILD

@@ -0,0 +1,32 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library")
+
+package(default_visibility = ["//visibility:public"])
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [
+        ":package-srcs",
+        "//plugin/pkg/admission/certificates/approval:all-srcs",
+        "//plugin/pkg/admission/certificates/signing:all-srcs",
+        "//plugin/pkg/admission/certificates/subjectrestriction:all-srcs",
+    ],
+    tags = ["automanaged"],
+)
+
+go_library(
+    name = "go_default_library",
+    srcs = ["util.go"],
+    importpath = "k8s.io/kubernetes/plugin/pkg/admission/certificates",
+    deps = [
+        "//staging/src/k8s.io/apiserver/pkg/authentication/user:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authorization/authorizer:go_default_library",
+        "//vendor/k8s.io/klog:go_default_library",
+    ],
+)

plugin/pkg/admission/certificates/OWNERS

@@ -0,0 +1,8 @@
+# See the OWNERS docs at https://go.k8s.io/owners
+
+approvers:
+- sig-auth-certificates-approvers
+reviewers:
+- sig-auth-certificates-approvers
+labels:
+- sig/auth

plugin/pkg/admission/certificates/approval/BUILD

@@ -0,0 +1,44 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["admission.go"],
+    importpath = "k8s.io/kubernetes/plugin/pkg/admission/certificates/approval",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/apis/certificates:go_default_library",
+        "//plugin/pkg/admission/certificates:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission/initializer:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authorization/authorizer:go_default_library",
+        "//vendor/k8s.io/klog:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["admission_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//pkg/apis/certificates:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authentication/user:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authorization/authorizer:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

plugin/pkg/admission/certificates/approval/admission.go

@@ -0,0 +1,99 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package approval
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	"k8s.io/klog"
+
+	"k8s.io/apiserver/pkg/admission"
+	genericadmissioninit "k8s.io/apiserver/pkg/admission/initializer"
+	"k8s.io/apiserver/pkg/authorization/authorizer"
+
+	api "k8s.io/kubernetes/pkg/apis/certificates"
+	"k8s.io/kubernetes/plugin/pkg/admission/certificates"
+)
+
+// PluginName is a string with the name of the plugin
+const PluginName = "CertificateApproval"
+
+// Register registers a plugin
+func Register(plugins *admission.Plugins) {
+	plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) {
+		return NewPlugin(), nil
+	})
+}
+
+// Plugin holds state for and implements the admission plugin.
+type Plugin struct {
+	*admission.Handler
+	authz authorizer.Authorizer
+}
+
+// SetAuthorizer sets the authorizer.
+func (p *Plugin) SetAuthorizer(authz authorizer.Authorizer) {
+	p.authz = authz
+}
+
+// ValidateInitialization ensures an authorizer is set.
+func (p *Plugin) ValidateInitialization() error {
+	if p.authz == nil {
+		return fmt.Errorf("%s requires an authorizer", PluginName)
+	}
+	return nil
+}
+
+var _ admission.ValidationInterface = &Plugin{}
+var _ genericadmissioninit.WantsAuthorizer = &Plugin{}
+
+// NewPlugin creates a new CSR approval admission plugin
+func NewPlugin() *Plugin {
+	return &Plugin{
+		Handler: admission.NewHandler(admission.Update),
+	}
+}
+
+var csrGroupResource = api.Resource("certificatesigningrequests")
+
+// Validate verifies that the requesting user has permission to approve
+// CertificateSigningRequests for the specified signerName.
+func (p *Plugin) Validate(ctx context.Context, a admission.Attributes, _ admission.ObjectInterfaces) error {
+	// Ignore all calls to anything other than 'certificatesigningrequests/approval'.
+	// Ignore all operations other than UPDATE.
+	if a.GetSubresource() != "approval" ||
+		a.GetResource().GroupResource() != csrGroupResource {
+		return nil
+	}
+
+	// We check permissions against the *old* version of the resource, in case
+	// a user is attempting to update the SignerName when calling the approval
+	// endpoint (which is an invalid/not allowed operation)
+	csr, ok := a.GetOldObject().(*api.CertificateSigningRequest)
+	if !ok {
+		return admission.NewForbidden(a, fmt.Errorf("expected type CertificateSigningRequest, got: %T", a.GetOldObject()))
+	}
+
+	if !certificates.IsAuthorizedForSignerName(ctx, p.authz, a.GetUserInfo(), "approve", csr.Spec.SignerName) {
+		klog.V(4).Infof("user not permitted to approve CertificateSigningRequest %q with signerName %q", csr.Name, csr.Spec.SignerName)
+		return admission.NewForbidden(a, fmt.Errorf("user not permitted to approve requests with signerName %q", csr.Spec.SignerName))
+	}
+
+	return nil
+}

plugin/pkg/admission/certificates/approval/admission_test.go

@@ -0,0 +1,206 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package approval
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/admission"
+	"k8s.io/apiserver/pkg/authentication/user"
+	"k8s.io/apiserver/pkg/authorization/authorizer"
+
+	certificatesapi "k8s.io/kubernetes/pkg/apis/certificates"
+)
+
+func TestPlugin_Validate(t *testing.T) {
+	tests := map[string]struct {
+		attributes  admission.Attributes
+		allowedName string
+		allowed     bool
+		authzErr    error
+	}{
+		"wrong type": {
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approval",
+				oldObj:      &certificatesapi.CertificateSigningRequestList{},
+				operation:   admission.Update,
+			},
+			allowed: false,
+		},
+		"reject requests if looking up permissions fails": {
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approval",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				operation: admission.Update,
+			},
+			authzErr: errors.New("forced error"),
+			allowed:  false,
+		},
+		"should allow request if user is authorized for specific signerName": {
+			allowedName: "abc.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approval",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				operation: admission.Update,
+			},
+			allowed: true,
+		},
+		"should allow request if user is authorized with wildcard": {
+			allowedName: "abc.com/*",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approval",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				operation: admission.Update,
+			},
+			allowed: true,
+		},
+		"should deny request if user does not have permission for this signerName": {
+			allowedName: "notabc.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approval",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				operation: admission.Update,
+			},
+			allowed: false,
+		},
+		"should deny request if user attempts to update signerName to a new value they *do* have permission to approve for": {
+			allowedName: "allowed.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approval",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "notallowed.com/xyz",
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "allowed.com/xyz",
+				}},
+				operation: admission.Update,
+			},
+			allowed: false,
+		},
+	}
+
+	for n, test := range tests {
+		t.Run(n, func(t *testing.T) {
+			p := Plugin{
+				authz: fakeAuthorizer{
+					t:           t,
+					verb:        "approve",
+					allowedName: test.allowedName,
+					decision:    authorizer.DecisionAllow,
+					err:         test.authzErr,
+				},
+			}
+			err := p.Validate(context.Background(), test.attributes, nil)
+			if err == nil && !test.allowed {
+				t.Errorf("Expected authorization policy to reject CSR but it was allowed")
+			}
+			if err != nil && test.allowed {
+				t.Errorf("Expected authorization policy to accept CSR but it was rejected: %v", err)
+			}
+		})
+	}
+}
+
+type fakeAuthorizer struct {
+	t           *testing.T
+	verb        string
+	allowedName string
+	decision    authorizer.Decision
+	err         error
+}
+
+func (f fakeAuthorizer) Authorize(ctx context.Context, a authorizer.Attributes) (authorizer.Decision, string, error) {
+	if f.err != nil {
+		return f.decision, "forced error", f.err
+	}
+	if a.GetVerb() != f.verb {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised verb '%s'", a.GetVerb()), nil
+	}
+	if a.GetAPIGroup() != "certificates.k8s.io" {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised groupName '%s'", a.GetAPIGroup()), nil
+	}
+	if a.GetAPIVersion() != "*" {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised apiVersion '%s'", a.GetAPIVersion()), nil
+	}
+	if a.GetResource() != "signers" {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised resource '%s'", a.GetResource()), nil
+	}
+	if a.GetName() != f.allowedName {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised resource name '%s'", a.GetName()), nil
+	}
+	if !a.IsResourceRequest() {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised IsResourceRequest '%t'", a.IsResourceRequest()), nil
+	}
+	return f.decision, "", nil
+}
+
+type testAttributes struct {
+	resource    schema.GroupResource
+	subresource string
+	operation   admission.Operation
+	obj, oldObj runtime.Object
+	name        string
+
+	admission.Attributes // nil panic if any other methods called
+}
+
+func (t *testAttributes) GetResource() schema.GroupVersionResource {
+	return t.resource.WithVersion("ignored")
+}
+
+func (t *testAttributes) GetSubresource() string {
+	return t.subresource
+}
+
+func (t *testAttributes) GetObject() runtime.Object {
+	return t.obj
+}
+
+func (t *testAttributes) GetOldObject() runtime.Object {
+	return t.oldObj
+}
+
+func (t *testAttributes) GetName() string {
+	return t.name
+}
+
+func (t *testAttributes) GetOperation() admission.Operation {
+	return t.operation
+}
+
+func (t *testAttributes) GetUserInfo() user.Info {
+	return &user.DefaultInfo{Name: "ignored"}
+}

plugin/pkg/admission/certificates/signing/BUILD

@@ -0,0 +1,44 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["admission.go"],
+    importpath = "k8s.io/kubernetes/plugin/pkg/admission/certificates/signing",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/apis/certificates:go_default_library",
+        "//plugin/pkg/admission/certificates:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission/initializer:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authorization/authorizer:go_default_library",
+        "//vendor/k8s.io/klog:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["admission_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//pkg/apis/certificates:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authentication/user:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/authorization/authorizer:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

plugin/pkg/admission/certificates/signing/admission.go

@@ -0,0 +1,106 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signing
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"reflect"
+
+	"k8s.io/klog"
+
+	"k8s.io/apiserver/pkg/admission"
+	genericadmissioninit "k8s.io/apiserver/pkg/admission/initializer"
+	"k8s.io/apiserver/pkg/authorization/authorizer"
+
+	api "k8s.io/kubernetes/pkg/apis/certificates"
+	"k8s.io/kubernetes/plugin/pkg/admission/certificates"
+)
+
+// PluginName is a string with the name of the plugin
+const PluginName = "CertificateSigning"
+
+// Register registers a plugin
+func Register(plugins *admission.Plugins) {
+	plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) {
+		return NewPlugin(), nil
+	})
+}
+
+// Plugin holds state for and implements the admission plugin.
+type Plugin struct {
+	*admission.Handler
+	authz authorizer.Authorizer
+}
+
+// SetAuthorizer sets the authorizer.
+func (p *Plugin) SetAuthorizer(authz authorizer.Authorizer) {
+	p.authz = authz
+}
+
+// ValidateInitialization ensures an authorizer is set.
+func (p *Plugin) ValidateInitialization() error {
+	if p.authz == nil {
+		return fmt.Errorf("%s requires an authorizer", PluginName)
+	}
+	return nil
+}
+
+var _ admission.ValidationInterface = &Plugin{}
+var _ genericadmissioninit.WantsAuthorizer = &Plugin{}
+
+// NewPlugin creates a new CSR approval admission plugin
+func NewPlugin() *Plugin {
+	return &Plugin{
+		Handler: admission.NewHandler(admission.Update),
+	}
+}
+
+var csrGroupResource = api.Resource("certificatesigningrequests")
+
+// Validate verifies that the requesting user has permission to approve
+// CertificateSigningRequests for the specified signerName.
+func (p *Plugin) Validate(ctx context.Context, a admission.Attributes, o admission.ObjectInterfaces) error {
+	// Ignore all calls to anything other than 'certificatesigningrequests/approval'.
+	// Ignore all operations other than UPDATE.
+	if a.GetSubresource() != "status" ||
+		a.GetResource().GroupResource() != csrGroupResource {
+		return nil
+	}
+
+	oldCSR, ok := a.GetOldObject().(*api.CertificateSigningRequest)
+	if !ok {
+		return admission.NewForbidden(a, fmt.Errorf("expected type CertificateSigningRequest, got: %T", a.GetOldObject()))
+	}
+	csr, ok := a.GetObject().(*api.CertificateSigningRequest)
+	if !ok {
+		return admission.NewForbidden(a, fmt.Errorf("expected type CertificateSigningRequest, got: %T", a.GetObject()))
+	}
+
+	// only run if the status.certificate field has been changed
+	if reflect.DeepEqual(oldCSR.Status.Certificate, csr.Status.Certificate) {
+		return nil
+	}
+
+	if !certificates.IsAuthorizedForSignerName(ctx, p.authz, a.GetUserInfo(), "sign", oldCSR.Spec.SignerName) {
+		klog.V(4).Infof("user not permitted to sign CertificateSigningRequest %q with signerName %q", oldCSR.Name, oldCSR.Spec.SignerName)
+		return admission.NewForbidden(a, fmt.Errorf("user not permitted to sign requests with signerName %q", oldCSR.Spec.SignerName))
+	}
+
+	return nil
+}

plugin/pkg/admission/certificates/signing/admission_test.go

@@ -0,0 +1,260 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package signing
+
+import (
+	"context"
+	"errors"
+	"fmt"
+	"testing"
+
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/admission"
+	"k8s.io/apiserver/pkg/authentication/user"
+	"k8s.io/apiserver/pkg/authorization/authorizer"
+
+	certificatesapi "k8s.io/kubernetes/pkg/apis/certificates"
+)
+
+func TestPlugin_Validate(t *testing.T) {
+	tests := map[string]struct {
+		attributes  admission.Attributes
+		allowedName string
+		allowed     bool
+		authzErr    error
+	}{
+		"wrong type": {
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj:      &certificatesapi.CertificateSigningRequestList{},
+				obj:         &certificatesapi.CertificateSigningRequestList{},
+				operation:   admission.Update,
+			},
+			allowed: false,
+		},
+		"allowed if the 'certificate' field has not changed": {
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj: &certificatesapi.CertificateSigningRequest{Status: certificatesapi.CertificateSigningRequestStatus{
+					Certificate: []byte("data"),
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{Status: certificatesapi.CertificateSigningRequestStatus{
+					Certificate: []byte("data"),
+				}},
+				operation: admission.Update,
+			},
+			allowed:  true,
+			authzErr: errors.New("faked error"),
+		},
+		"deny request if authz lookup fails": {
+			allowedName: "abc.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{
+					Spec: certificatesapi.CertificateSigningRequestSpec{
+						SignerName: "abc.com/xyz",
+					},
+					Status: certificatesapi.CertificateSigningRequestStatus{
+						Certificate: []byte("data"),
+					},
+				},
+				operation: admission.Update,
+			},
+			authzErr: errors.New("test"),
+			allowed:  false,
+		},
+		"allow request if user is authorized for specific signerName": {
+			allowedName: "abc.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{
+					Spec: certificatesapi.CertificateSigningRequestSpec{
+						SignerName: "abc.com/xyz",
+					},
+					Status: certificatesapi.CertificateSigningRequestStatus{
+						Certificate: []byte("data"),
+					},
+				},
+				operation: admission.Update,
+			},
+			allowed: true,
+		},
+		"allow request if user is authorized with wildcard": {
+			allowedName: "abc.com/*",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{
+					Spec: certificatesapi.CertificateSigningRequestSpec{
+						SignerName: "abc.com/xyz",
+					},
+					Status: certificatesapi.CertificateSigningRequestStatus{
+						Certificate: []byte("data"),
+					},
+				},
+				operation: admission.Update,
+			},
+			allowed: true,
+		},
+		"should deny request if user does not have permission for this signerName": {
+			allowedName: "notabc.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "abc.com/xyz",
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{
+					Spec: certificatesapi.CertificateSigningRequestSpec{
+						SignerName: "abc.com/xyz",
+					},
+					Status: certificatesapi.CertificateSigningRequestStatus{
+						Certificate: []byte("data"),
+					},
+				},
+				operation: admission.Update,
+			},
+			allowed: false,
+		},
+		"should deny request if user attempts to update signerName to a new value they *do* have permission to sign for": {
+			allowedName: "allowed.com/xyz",
+			attributes: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "status",
+				oldObj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					SignerName: "notallowed.com/xyz",
+				}},
+				obj: &certificatesapi.CertificateSigningRequest{
+					Spec: certificatesapi.CertificateSigningRequestSpec{
+						SignerName: "allowed.com/xyz",
+					},
+					Status: certificatesapi.CertificateSigningRequestStatus{
+						Certificate: []byte("data"),
+					},
+				},
+				operation: admission.Update,
+			},
+			allowed: false,
+		},
+	}
+
+	for n, test := range tests {
+		t.Run(n, func(t *testing.T) {
+			p := Plugin{
+				authz: fakeAuthorizer{
+					t:           t,
+					verb:        "sign",
+					allowedName: test.allowedName,
+					decision:    authorizer.DecisionAllow,
+					err:         test.authzErr,
+				},
+			}
+			err := p.Validate(context.Background(), test.attributes, nil)
+			if err == nil && !test.allowed {
+				t.Errorf("Expected authorization policy to reject CSR but it was allowed")
+			}
+			if err != nil && test.allowed {
+				t.Errorf("Expected authorization policy to accept CSR but it was rejected: %v", err)
+			}
+		})
+	}
+}
+
+type fakeAuthorizer struct {
+	t           *testing.T
+	verb        string
+	allowedName string
+	decision    authorizer.Decision
+	err         error
+}
+
+func (f fakeAuthorizer) Authorize(ctx context.Context, a authorizer.Attributes) (authorizer.Decision, string, error) {
+	if f.err != nil {
+		return f.decision, "forced error", f.err
+	}
+	if a.GetVerb() != f.verb {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised verb '%s'", a.GetVerb()), nil
+	}
+	if a.GetAPIGroup() != "certificates.k8s.io" {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised groupName '%s'", a.GetAPIGroup()), nil
+	}
+	if a.GetAPIVersion() != "*" {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised apiVersion '%s'", a.GetAPIVersion()), nil
+	}
+	if a.GetResource() != "signers" {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised resource '%s'", a.GetResource()), nil
+	}
+	if a.GetName() != f.allowedName {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised resource name '%s'", a.GetName()), nil
+	}
+	if !a.IsResourceRequest() {
+		return authorizer.DecisionDeny, fmt.Sprintf("unrecognised IsResourceRequest '%t'", a.IsResourceRequest()), nil
+	}
+	return f.decision, "", nil
+}
+
+type testAttributes struct {
+	resource    schema.GroupResource
+	subresource string
+	operation   admission.Operation
+	oldObj, obj runtime.Object
+	name        string
+
+	admission.Attributes // nil panic if any other methods called
+}
+
+func (t *testAttributes) GetResource() schema.GroupVersionResource {
+	return t.resource.WithVersion("ignored")
+}
+
+func (t *testAttributes) GetSubresource() string {
+	return t.subresource
+}
+
+func (t *testAttributes) GetOldObject() runtime.Object {
+	return t.oldObj
+}
+
+func (t *testAttributes) GetObject() runtime.Object {
+	return t.obj
+}
+
+func (t *testAttributes) GetName() string {
+	return t.name
+}
+
+func (t *testAttributes) GetOperation() admission.Operation {
+	return t.operation
+}
+
+func (t *testAttributes) GetUserInfo() user.Info {
+	return &user.DefaultInfo{Name: "ignored"}
+}

plugin/pkg/admission/certificates/subjectrestriction/BUILD

@@ -0,0 +1,41 @@
+load("@io_bazel_rules_go//go:def.bzl", "go_library", "go_test")
+
+go_library(
+    name = "go_default_library",
+    srcs = ["admission.go"],
+    importpath = "k8s.io/kubernetes/plugin/pkg/admission/certificates/subjectrestriction",
+    visibility = ["//visibility:public"],
+    deps = [
+        "//pkg/apis/certificates:go_default_library",
+        "//staging/src/k8s.io/api/certificates/v1beta1:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
+        "//vendor/k8s.io/klog:go_default_library",
+    ],
+)
+
+go_test(
+    name = "go_default_test",
+    srcs = ["admission_test.go"],
+    embed = [":go_default_library"],
+    deps = [
+        "//pkg/apis/certificates:go_default_library",
+        "//staging/src/k8s.io/api/certificates/v1beta1:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime:go_default_library",
+        "//staging/src/k8s.io/apimachinery/pkg/runtime/schema:go_default_library",
+        "//staging/src/k8s.io/apiserver/pkg/admission:go_default_library",
+    ],
+)
+
+filegroup(
+    name = "package-srcs",
+    srcs = glob(["**"]),
+    tags = ["automanaged"],
+    visibility = ["//visibility:private"],
+)
+
+filegroup(
+    name = "all-srcs",
+    srcs = [":package-srcs"],
+    tags = ["automanaged"],
+    visibility = ["//visibility:public"],
+)

plugin/pkg/admission/certificates/subjectrestriction/admission.go

@@ -0,0 +1,93 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package subjectrestriction
+
+import (
+	"context"
+	"fmt"
+	"io"
+
+	certificatesv1beta1 "k8s.io/api/certificates/v1beta1"
+	"k8s.io/apiserver/pkg/admission"
+	"k8s.io/klog"
+	certificatesapi "k8s.io/kubernetes/pkg/apis/certificates"
+)
+
+// PluginName is a string with the name of the plugin
+const PluginName = "CertificateSubjectRestriction"
+
+// Register registers the plugin
+func Register(plugins *admission.Plugins) {
+	plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) {
+		return NewPlugin(), nil
+	})
+}
+
+// Plugin holds state for and implements the admission plugin.
+type Plugin struct {
+	*admission.Handler
+}
+
+// ValidateInitialization always returns nil.
+func (p *Plugin) ValidateInitialization() error {
+	return nil
+}
+
+var _ admission.ValidationInterface = &Plugin{}
+
+// NewPlugin constructs a new instance of the CertificateSubjectRestrictions admission interface.
+func NewPlugin() *Plugin {
+	return &Plugin{
+		Handler: admission.NewHandler(admission.Create),
+	}
+}
+
+var csrGroupResource = certificatesapi.Resource("certificatesigningrequests")
+
+// Validate ensures that if the signerName on a CSR is set to
+// `kubernetes.io/kube-apiserver-client`, that its organization (group)
+// attribute is not set to `system:masters`.
+func (p *Plugin) Validate(_ context.Context, a admission.Attributes, _ admission.ObjectInterfaces) error {
+	if a.GetResource().GroupResource() != csrGroupResource || a.GetSubresource() != "" {
+		return nil
+	}
+
+	csr, ok := a.GetObject().(*certificatesapi.CertificateSigningRequest)
+	if !ok {
+		return admission.NewForbidden(a, fmt.Errorf("expected type CertificateSigningRequest, got: %T", a.GetObject()))
+	}
+
+	if csr.Spec.SignerName != certificatesv1beta1.KubeAPIServerClientSignerName {
+		return nil
+	}
+
+	csrParsed, err := certificatesapi.ParseCSR(csr)
+	if err != nil {
+		return admission.NewForbidden(a, fmt.Errorf("failed to parse CSR: %v", err))
+	}
+
+	for _, group := range csrParsed.Subject.Organization {
+		if group == "system:masters" {
+			klog.V(4).Infof("CSR %s rejected by admission plugin %s for attempting to use signer %s with system:masters group",
+				csr.Name, PluginName, certificatesv1beta1.KubeAPIServerClientSignerName)
+			return admission.NewForbidden(a, fmt.Errorf("use of %s signer with system:masters group is not allowed",
+				certificatesv1beta1.KubeAPIServerClientSignerName))
+		}
+	}
+
+	return nil
+}

plugin/pkg/admission/certificates/subjectrestriction/admission_test.go

@@ -0,0 +1,189 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package subjectrestriction
+
+import (
+	"context"
+	"crypto/ed25519"
+	"crypto/rand"
+	"crypto/x509"
+	"crypto/x509/pkix"
+	"encoding/pem"
+	"testing"
+
+	certificatesv1beta1 "k8s.io/api/certificates/v1beta1"
+	"k8s.io/apimachinery/pkg/runtime"
+	"k8s.io/apimachinery/pkg/runtime/schema"
+	"k8s.io/apiserver/pkg/admission"
+	certificatesapi "k8s.io/kubernetes/pkg/apis/certificates"
+)
+
+func TestPlugin_Validate(t *testing.T) {
+	tests := []struct {
+		name    string
+		a       admission.Attributes
+		wantErr string
+	}{
+		{
+			name: "ignored resource",
+			a: &testAttributes{
+				resource: schema.GroupResource{
+					Group:    "foo",
+					Resource: "bar",
+				},
+			},
+			wantErr: "",
+		},
+		{
+			name: "ignored subresource",
+			a: &testAttributes{
+				resource:    certificatesapi.Resource("certificatesigningrequests"),
+				subresource: "approve",
+			},
+			wantErr: "",
+		},
+		{
+			name: "wrong type",
+			a: &testAttributes{
+				resource: certificatesapi.Resource("certificatesigningrequests"),
+				obj:      &certificatesapi.CertificateSigningRequestList{},
+				name:     "panda",
+			},
+			wantErr: `certificatesigningrequests.certificates.k8s.io "panda" is forbidden: expected type CertificateSigningRequest, got: *certificates.CertificateSigningRequestList`,
+		},
+		{
+			name: "some other signer",
+			a: &testAttributes{
+				resource: certificatesapi.Resource("certificatesigningrequests"),
+				obj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					Request:    pemWithGroup("system:masters"),
+					SignerName: certificatesv1beta1.KubeAPIServerClientKubeletSignerName,
+				}},
+			},
+			wantErr: "",
+		},
+		{
+			name: "invalid request",
+			a: &testAttributes{
+				resource: certificatesapi.Resource("certificatesigningrequests"),
+				obj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					Request:    []byte("this is not a CSR"),
+					SignerName: certificatesv1beta1.KubeAPIServerClientSignerName,
+				}},
+				name: "bear",
+			},
+			wantErr: `certificatesigningrequests.certificates.k8s.io "bear" is forbidden: failed to parse CSR: PEM block type must be CERTIFICATE REQUEST`,
+		},
+		{
+			name: "some other group",
+			a: &testAttributes{
+				resource: certificatesapi.Resource("certificatesigningrequests"),
+				obj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					Request:    pemWithGroup("system:admin"),
+					SignerName: certificatesv1beta1.KubeAPIServerClientSignerName,
+				}},
+			},
+			wantErr: "",
+		},
+		{
+			name: "request for system:masters",
+			a: &testAttributes{
+				resource: certificatesapi.Resource("certificatesigningrequests"),
+				obj: &certificatesapi.CertificateSigningRequest{Spec: certificatesapi.CertificateSigningRequestSpec{
+					Request:    pemWithGroup("system:masters"),
+					SignerName: certificatesv1beta1.KubeAPIServerClientSignerName,
+				}},
+				name: "pooh",
+			},
+			wantErr: `certificatesigningrequests.certificates.k8s.io "pooh" is forbidden: use of kubernetes.io/kube-apiserver-client signer with system:masters group is not allowed`,
+		},
+	}
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			p := &Plugin{}
+			if err := p.Validate(context.TODO(), tt.a, nil); errStr(err) != tt.wantErr {
+				t.Errorf("Validate() error = %v, wantErr %v", err, tt.wantErr)
+			}
+		})
+	}
+}
+
+type testAttributes struct {
+	resource    schema.GroupResource
+	subresource string
+	obj         runtime.Object
+	name        string
+
+	admission.Attributes // nil panic if any other methods called
+}
+
+func (t *testAttributes) GetResource() schema.GroupVersionResource {
+	return t.resource.WithVersion("ignored")
+}
+
+func (t *testAttributes) GetSubresource() string {
+	return t.subresource
+}
+
+func (t *testAttributes) GetObject() runtime.Object {
+	return t.obj
+}
+
+func (t *testAttributes) GetName() string {
+	return t.name
+}
+
+func errStr(err error) string {
+	if err == nil {
+		return ""
+	}
+	es := err.Error()
+	if len(es) == 0 {
+		panic("invalid empty error")
+	}
+	return es
+}
+
+func pemWithGroup(group string) []byte {
+	template := &x509.CertificateRequest{
+		Subject: pkix.Name{
+			Organization: []string{group},
+		},
+	}
+
+	_, key, err := ed25519.GenerateKey(rand.Reader)
+	if err != nil {
+		panic(err)
+	}
+
+	csrDER, err := x509.CreateCertificateRequest(rand.Reader, template, key)
+	if err != nil {
+		panic(err)
+	}
+
+	csrPemBlock := &pem.Block{
+		Type:  "CERTIFICATE REQUEST",
+		Bytes: csrDER,
+	}
+
+	p := pem.EncodeToMemory(csrPemBlock)
+	if p == nil {
+		panic("invalid pem block")
+	}
+
+	return p
+}

plugin/pkg/admission/certificates/util.go

@@ -0,0 +1,75 @@
+/*
+Copyright 2020 The Kubernetes Authors.
+
+Licensed under the Apache License, Version 2.0 (the "License");
+you may not use this file except in compliance with the License.
+You may obtain a copy of the License at
+
+    http://www.apache.org/licenses/LICENSE-2.0
+
+Unless required by applicable law or agreed to in writing, software
+distributed under the License is distributed on an "AS IS" BASIS,
+WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+See the License for the specific language governing permissions and
+limitations under the License.
+*/
+
+package certificates
+
+import (
+	"context"
+	"strings"
+
+	"k8s.io/apiserver/pkg/authentication/user"
+	"k8s.io/apiserver/pkg/authorization/authorizer"
+	"k8s.io/klog"
+)
+
+// IsAuthorizedForSignerName returns true if 'info' is authorized to perform the given
+// 'verb' on the synthetic 'signers' resource with the given signerName.
+// If the user does not have permission to perform the 'verb' on the given signerName,
+// it will also perform an authorization check against {domain portion}/*, for example
+// `kubernetes.io/*`. This allows an entity to be granted permission to 'verb' on all
+// signerNames with a given 'domain portion'.
+func IsAuthorizedForSignerName(ctx context.Context, authz authorizer.Authorizer, info user.Info, verb, signerName string) bool {
+	// First check if the user has explicit permission to 'verb' for the given signerName.
+	attr := buildAttributes(info, verb, signerName)
+	decision, reason, err := authz.Authorize(ctx, attr)
+	switch {
+	case err != nil:
+		klog.V(3).Infof("cannot authorize %q %q for policy: %v,%v", verb, attr.GetName(), reason, err)
+	case decision == authorizer.DecisionAllow:
+		return true
+	}
+
+	// If not, check if the user has wildcard permissions to 'verb' for the domain portion of the signerName, e.g.
+	// 'kubernetes.io/*'.
+	attr = buildWildcardAttributes(info, verb, signerName)
+	decision, reason, err = authz.Authorize(ctx, attr)
+	switch {
+	case err != nil:
+		klog.V(3).Infof("cannot authorize %q %q for policy: %v,%v", verb, attr.GetName(), reason, err)
+	case decision == authorizer.DecisionAllow:
+		return true
+	}
+
+	return false
+}
+
+func buildAttributes(info user.Info, verb, signerName string) authorizer.Attributes {
+	return authorizer.AttributesRecord{
+		User:            info,
+		Verb:            verb,
+		Name:            signerName,
+		APIGroup:        "certificates.k8s.io",
+		APIVersion:      "*",
+		Resource:        "signers",
+		ResourceRequest: true,
+	}
+}
+
+func buildWildcardAttributes(info user.Info, verb, signerName string) authorizer.Attributes {
+	parts := strings.Split(signerName, "/")
+	domain := parts[0]
+	return buildAttributes(info, verb, domain+"/*")
+}

plugin/pkg/auth/authorizer/rbac/bootstrappolicy/BUILD

@@ -17,6 +17,7 @@ go_library(
     deps = [
         "//pkg/apis/rbac/v1:go_default_library",
         "//pkg/features:go_default_library",
+        "//staging/src/k8s.io/api/certificates/v1beta1:go_default_library",
         "//staging/src/k8s.io/api/rbac/v1:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/api/meta:go_default_library",
         "//staging/src/k8s.io/apimachinery/pkg/apis/meta/v1:go_default_library",

plugin/pkg/auth/authorizer/rbac/bootstrappolicy/controller_policy.go

@@ -21,6 +21,7 @@ import (
 
 	"k8s.io/klog"
 
+	capi "k8s.io/api/certificates/v1beta1"
 	rbacv1 "k8s.io/api/rbac/v1"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
 	utilfeature "k8s.io/apiserver/pkg/util/feature"
@@ -337,6 +338,13 @@ func buildControllerRoles() ([]rbacv1.ClusterRole, []rbacv1.ClusterRoleBinding)
 		Rules: []rbacv1.PolicyRule{
 			rbacv1helpers.NewRule("get", "list", "watch", "delete").Groups(certificatesGroup).Resources("certificatesigningrequests").RuleOrDie(),
 			rbacv1helpers.NewRule("update").Groups(certificatesGroup).Resources("certificatesigningrequests/status", "certificatesigningrequests/approval").RuleOrDie(),
+			rbacv1helpers.NewRule("approve").Groups(certificatesGroup).Resources("signers").Names(capi.KubeAPIServerClientKubeletSignerName).RuleOrDie(),
+			rbacv1helpers.NewRule("sign").Groups(certificatesGroup).Resources("signers").Names(
+				capi.LegacyUnknownSignerName,
+				capi.KubeAPIServerClientSignerName,
+				capi.KubeAPIServerClientKubeletSignerName,
+				capi.KubeletServingSignerName,
+			).RuleOrDie(),
 			rbacv1helpers.NewRule("create").Groups(authorizationGroup).Resources("subjectaccessreviews").RuleOrDie(),
 			eventsRule(),
 		},

plugin/pkg/auth/authorizer/rbac/bootstrappolicy/policy.go

@@ -17,6 +17,7 @@ limitations under the License.
 package bootstrappolicy
 
 import (
+	capi "k8s.io/api/certificates/v1beta1"
 	rbacv1 "k8s.io/api/rbac/v1"
 	"k8s.io/apimachinery/pkg/api/meta"
 	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
@@ -459,6 +460,30 @@ func ClusterRoles() []rbacv1.ClusterRole {
 				rbacv1helpers.NewRule(ReadUpdate...).Groups(legacyGroup).Resources("persistentvolumeclaims").RuleOrDie(),
 			},
 		},
+		{
+			ObjectMeta: metav1.ObjectMeta{Name: "system:certificates.k8s.io:legacy-unknown-approver"},
+			Rules: []rbacv1.PolicyRule{
+				rbacv1helpers.NewRule("approve").Groups(certificatesGroup).Resources("signers").Names(capi.LegacyUnknownSignerName).RuleOrDie(),
+			},
+		},
+		{
+			ObjectMeta: metav1.ObjectMeta{Name: "system:certificates.k8s.io:kubelet-serving-approver"},
+			Rules: []rbacv1.PolicyRule{
+				rbacv1helpers.NewRule("approve").Groups(certificatesGroup).Resources("signers").Names(capi.KubeletServingSignerName).RuleOrDie(),
+			},
+		},
+		{
+			ObjectMeta: metav1.ObjectMeta{Name: "system:certificates.k8s.io:kube-apiserver-client-approver"},
+			Rules: []rbacv1.PolicyRule{
+				rbacv1helpers.NewRule("approve").Groups(certificatesGroup).Resources("signers").Names(capi.KubeAPIServerClientSignerName).RuleOrDie(),
+			},
+		},
+		{
+			ObjectMeta: metav1.ObjectMeta{Name: "system:certificates.k8s.io:kube-apiserver-client-kubelet-approver"},
+			Rules: []rbacv1.PolicyRule{
+				rbacv1helpers.NewRule("approve").Groups(certificatesGroup).Resources("signers").Names(capi.KubeAPIServerClientKubeletSignerName).RuleOrDie(),
+			},
+		},
 	}
 
 	if utilfeature.DefaultFeatureGate.Enabled(features.ServiceAccountIssuerDiscovery) {

plugin/pkg/auth/authorizer/rbac/bootstrappolicy/testdata/cluster-roles.yaml

@@ -419,6 +419,78 @@ items:
     - certificatesigningrequests/selfnodeclient
     verbs:
     - create
+- apiVersion: rbac.authorization.k8s.io/v1
+  kind: ClusterRole
+  metadata:
+    annotations:
+      rbac.authorization.kubernetes.io/autoupdate: "true"
+    creationTimestamp: null
+    labels:
+      kubernetes.io/bootstrapping: rbac-defaults
+    name: system:certificates.k8s.io:kube-apiserver-client-approver
+  rules:
+  - apiGroups:
+    - certificates.k8s.io
+    resourceNames:
+    - kubernetes.io/kube-apiserver-client
+    resources:
+    - signers
+    verbs:
+    - approve
+- apiVersion: rbac.authorization.k8s.io/v1
+  kind: ClusterRole
+  metadata:
+    annotations:
+      rbac.authorization.kubernetes.io/autoupdate: "true"
+    creationTimestamp: null
+    labels:
+      kubernetes.io/bootstrapping: rbac-defaults
+    name: system:certificates.k8s.io:kube-apiserver-client-kubelet-approver
+  rules:
+  - apiGroups:
+    - certificates.k8s.io
+    resourceNames:
+    - kubernetes.io/kube-apiserver-client-kubelet
+    resources:
+    - signers
+    verbs:
+    - approve
+- apiVersion: rbac.authorization.k8s.io/v1
+  kind: ClusterRole
+  metadata:
+    annotations:
+      rbac.authorization.kubernetes.io/autoupdate: "true"
+    creationTimestamp: null
+    labels:
+      kubernetes.io/bootstrapping: rbac-defaults
+    name: system:certificates.k8s.io:kubelet-serving-approver
+  rules:
+  - apiGroups:
+    - certificates.k8s.io
+    resourceNames:
+    - kubernetes.io/kubelet-serving
+    resources:
+    - signers
+    verbs:
+    - approve
+- apiVersion: rbac.authorization.k8s.io/v1
+  kind: ClusterRole
+  metadata:
+    annotations:
+      rbac.authorization.kubernetes.io/autoupdate: "true"
+    creationTimestamp: null
+    labels:
+      kubernetes.io/bootstrapping: rbac-defaults
+    name: system:certificates.k8s.io:legacy-unknown-approver
+  rules:
+  - apiGroups:
+    - certificates.k8s.io
+    resourceNames:
+    - kubernetes.io/legacy-unknown
+    resources:
+    - signers
+    verbs:
+    - approve
 - apiVersion: rbac.authorization.k8s.io/v1
   kind: ClusterRole
   metadata:

plugin/pkg/auth/authorizer/rbac/bootstrappolicy/testdata/controller-roles.yaml

@@ -101,6 +101,25 @@ items:
     - certificatesigningrequests/status
     verbs:
     - update
+  - apiGroups:
+    - certificates.k8s.io
+    resourceNames:
+    - kubernetes.io/kube-apiserver-client-kubelet
+    resources:
+    - signers
+    verbs:
+    - approve
+  - apiGroups:
+    - certificates.k8s.io
+    resourceNames:
+    - kubernetes.io/kube-apiserver-client
+    - kubernetes.io/kube-apiserver-client-kubelet
+    - kubernetes.io/kubelet-serving
+    - kubernetes.io/legacy-unknown
+    resources:
+    - signers
+    verbs:
+    - sign
   - apiGroups:
     - authorization.k8s.io
     resources: