1/*
2Copyright 2016 The Kubernetes Authors.
3
4Licensed under the Apache License, Version 2.0 (the "License");
5you may not use this file except in compliance with the License.
6You may obtain a copy of the License at
7
8    http://www.apache.org/licenses/LICENSE-2.0
9
10Unless required by applicable law or agreed to in writing, software
11distributed under the License is distributed on an "AS IS" BASIS,
12WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13See the License for the specific language governing permissions and
14limitations under the License.
15*/
16
17// Package policybased implements a standard storage for ClusterRole that prevents privilege escalation.
18package policybased
19
20import (
21	"context"
22	"errors"
23
24	apierrors "k8s.io/apimachinery/pkg/api/errors"
25	metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
26	"k8s.io/apimachinery/pkg/runtime"
27	"k8s.io/apiserver/pkg/authorization/authorizer"
28	"k8s.io/apiserver/pkg/registry/rest"
29	kapihelper "k8s.io/kubernetes/pkg/apis/core/helper"
30	"k8s.io/kubernetes/pkg/apis/rbac"
31	rbacregistry "k8s.io/kubernetes/pkg/registry/rbac"
32	rbacregistryvalidation "k8s.io/kubernetes/pkg/registry/rbac/validation"
33)
34
35var groupResource = rbac.Resource("clusterroles")
36
37type Storage struct {
38	rest.StandardStorage
39
40	authorizer authorizer.Authorizer
41
42	ruleResolver rbacregistryvalidation.AuthorizationRuleResolver
43}
44
45func NewStorage(s rest.StandardStorage, authorizer authorizer.Authorizer, ruleResolver rbacregistryvalidation.AuthorizationRuleResolver) *Storage {
46	return &Storage{s, authorizer, ruleResolver}
47}
48
49func (r *Storage) NamespaceScoped() bool {
50	return false
51}
52
53func (r *Storage) StorageVersion() runtime.GroupVersioner {
54	svp, ok := r.StandardStorage.(rest.StorageVersionProvider)
55	if !ok {
56		return nil
57	}
58	return svp.StorageVersion()
59}
60
61var _ rest.StorageVersionProvider = &Storage{}
62
63var fullAuthority = []rbac.PolicyRule{
64	rbac.NewRule("*").Groups("*").Resources("*").RuleOrDie(),
65	rbac.NewRule("*").URLs("*").RuleOrDie(),
66}
67
68func (s *Storage) Create(ctx context.Context, obj runtime.Object, createValidatingAdmission rest.ValidateObjectFunc, options *metav1.CreateOptions) (runtime.Object, error) {
69	if rbacregistry.EscalationAllowed(ctx) || rbacregistry.RoleEscalationAuthorized(ctx, s.authorizer) {
70		return s.StandardStorage.Create(ctx, obj, createValidatingAdmission, options)
71	}
72
73	clusterRole := obj.(*rbac.ClusterRole)
74	rules := clusterRole.Rules
75	if err := rbacregistryvalidation.ConfirmNoEscalationInternal(ctx, s.ruleResolver, rules); err != nil {
76		return nil, apierrors.NewForbidden(groupResource, clusterRole.Name, err)
77	}
78	// to set the aggregation rule, since it can gather anything, requires * on *.*
79	if hasAggregationRule(clusterRole) {
80		if err := rbacregistryvalidation.ConfirmNoEscalationInternal(ctx, s.ruleResolver, fullAuthority); err != nil {
81			return nil, apierrors.NewForbidden(groupResource, clusterRole.Name, errors.New("must have cluster-admin privileges to use the aggregationRule"))
82		}
83	}
84
85	return s.StandardStorage.Create(ctx, obj, createValidatingAdmission, options)
86}
87
88func (s *Storage) Update(ctx context.Context, name string, obj rest.UpdatedObjectInfo, createValidation rest.ValidateObjectFunc, updateValidation rest.ValidateObjectUpdateFunc, forceAllowCreate bool, options *metav1.UpdateOptions) (runtime.Object, bool, error) {
89	if rbacregistry.EscalationAllowed(ctx) || rbacregistry.RoleEscalationAuthorized(ctx, s.authorizer) {
90		return s.StandardStorage.Update(ctx, name, obj, createValidation, updateValidation, forceAllowCreate, options)
91	}
92
93	nonEscalatingInfo := rest.WrapUpdatedObjectInfo(obj, func(ctx context.Context, obj runtime.Object, oldObj runtime.Object) (runtime.Object, error) {
94		clusterRole := obj.(*rbac.ClusterRole)
95		oldClusterRole := oldObj.(*rbac.ClusterRole)
96
97		// if we're only mutating fields needed for the GC to eventually delete this obj, return
98		if rbacregistry.IsOnlyMutatingGCFields(obj, oldObj, kapihelper.Semantic) {
99			return obj, nil
100		}
101
102		rules := clusterRole.Rules
103		if err := rbacregistryvalidation.ConfirmNoEscalationInternal(ctx, s.ruleResolver, rules); err != nil {
104			return nil, apierrors.NewForbidden(groupResource, clusterRole.Name, err)
105		}
106		// to change the aggregation rule, since it can gather anything and prevent tightening, requires * on *.*
107		if hasAggregationRule(clusterRole) || hasAggregationRule(oldClusterRole) {
108			if err := rbacregistryvalidation.ConfirmNoEscalationInternal(ctx, s.ruleResolver, fullAuthority); err != nil {
109				return nil, apierrors.NewForbidden(groupResource, clusterRole.Name, errors.New("must have cluster-admin privileges to use the aggregationRule"))
110			}
111		}
112
113		return obj, nil
114	})
115
116	return s.StandardStorage.Update(ctx, name, nonEscalatingInfo, createValidation, updateValidation, forceAllowCreate, options)
117}
118
119func hasAggregationRule(clusterRole *rbac.ClusterRole) bool {
120	return clusterRole.AggregationRule != nil && len(clusterRole.AggregationRule.ClusterRoleSelectors) > 0
121}
122