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

/*
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
}