forked from kubernetes/kubernetes
-
Notifications
You must be signed in to change notification settings - Fork 1
/
admission.go
373 lines (321 loc) · 13.9 KB
/
admission.go
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
/*
Copyright 2016 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 admission
import (
"fmt"
"io"
"strings"
"github.com/golang/glog"
"k8s.io/apimachinery/pkg/api/errors"
metav1 "k8s.io/apimachinery/pkg/apis/meta/v1"
"k8s.io/apimachinery/pkg/runtime"
"k8s.io/apimachinery/pkg/util/validation/field"
"k8s.io/apimachinery/pkg/watch"
"k8s.io/apiserver/pkg/admission"
"k8s.io/apiserver/pkg/authentication/user"
"k8s.io/apiserver/pkg/authorization/authorizer"
"k8s.io/client-go/tools/cache"
"k8s.io/kubernetes/pkg/api"
"k8s.io/kubernetes/pkg/apis/extensions"
"k8s.io/kubernetes/pkg/client/clientset_generated/internalclientset"
kubeapiserveradmission "k8s.io/kubernetes/pkg/kubeapiserver/admission"
psp "k8s.io/kubernetes/pkg/security/podsecuritypolicy"
psputil "k8s.io/kubernetes/pkg/security/podsecuritypolicy/util"
sc "k8s.io/kubernetes/pkg/securitycontext"
"k8s.io/kubernetes/pkg/serviceaccount"
"k8s.io/kubernetes/pkg/util/maps"
)
const (
PluginName = "PodSecurityPolicy"
)
func init() {
admission.RegisterPlugin(PluginName, func(config io.Reader) (admission.Interface, error) {
plugin := NewPlugin(psp.NewSimpleStrategyFactory(), getMatchingPolicies, true)
return plugin, nil
})
}
// PSPMatchFn allows plugging in how PSPs are matched against user information.
type PSPMatchFn func(store cache.Store, user user.Info, sa user.Info, authz authorizer.Authorizer) ([]*extensions.PodSecurityPolicy, error)
// podSecurityPolicyPlugin holds state for and implements the admission plugin.
type podSecurityPolicyPlugin struct {
*admission.Handler
strategyFactory psp.StrategyFactory
pspMatcher PSPMatchFn
failOnNoPolicies bool
authz authorizer.Authorizer
reflector *cache.Reflector
stopChan chan struct{}
store cache.Store
}
// SetAuthorizer sets the authorizer.
func (plugin *podSecurityPolicyPlugin) SetAuthorizer(authz authorizer.Authorizer) {
plugin.authz = authz
}
// Validate ensures an authorizer is set.
func (plugin *podSecurityPolicyPlugin) Validate() error {
if plugin.authz == nil {
return fmt.Errorf("%s requires an authorizer", PluginName)
}
if plugin.store == nil {
return fmt.Errorf("%s requires an client", PluginName)
}
if plugin.store == nil {
return fmt.Errorf("%s requires an client", PluginName)
}
return nil
}
var _ admission.Interface = &podSecurityPolicyPlugin{}
var _ kubeapiserveradmission.WantsAuthorizer = &podSecurityPolicyPlugin{}
var _ kubeapiserveradmission.WantsInternalClientSet = &podSecurityPolicyPlugin{}
// NewPlugin creates a new PSP admission plugin.
func NewPlugin(strategyFactory psp.StrategyFactory, pspMatcher PSPMatchFn, failOnNoPolicies bool) *podSecurityPolicyPlugin {
return &podSecurityPolicyPlugin{
Handler: admission.NewHandler(admission.Create, admission.Update),
strategyFactory: strategyFactory,
pspMatcher: pspMatcher,
failOnNoPolicies: failOnNoPolicies,
}
}
func (a *podSecurityPolicyPlugin) SetInternalClientSet(client internalclientset.Interface) {
a.store = cache.NewStore(cache.MetaNamespaceKeyFunc)
a.reflector = cache.NewReflector(
&cache.ListWatch{
ListFunc: func(options metav1.ListOptions) (runtime.Object, error) {
return client.Extensions().PodSecurityPolicies().List(options)
},
WatchFunc: func(options metav1.ListOptions) (watch.Interface, error) {
return client.Extensions().PodSecurityPolicies().Watch(options)
},
},
&extensions.PodSecurityPolicy{},
a.store,
0,
)
a.Run()
}
func (a *podSecurityPolicyPlugin) Run() {
if a.stopChan == nil {
a.stopChan = make(chan struct{})
}
a.reflector.RunUntil(a.stopChan)
}
func (a *podSecurityPolicyPlugin) Stop() {
if a.stopChan != nil {
close(a.stopChan)
a.stopChan = nil
}
}
// Admit determines if the pod should be admitted based on the requested security context
// and the available PSPs.
//
// 1. Find available PSPs.
// 2. Create the providers, includes setting pre-allocated values if necessary.
// 3. Try to generate and validate a PSP with providers. If we find one then admit the pod
// with the validated PSP. If we don't find any reject the pod and give all errors from the
// failed attempts.
func (c *podSecurityPolicyPlugin) Admit(a admission.Attributes) error {
if a.GetResource().GroupResource() != api.Resource("pods") {
return nil
}
if len(a.GetSubresource()) != 0 {
return nil
}
pod, ok := a.GetObject().(*api.Pod)
// if we can't convert then we don't handle this object so just return
if !ok {
return nil
}
// get all constraints that are usable by the user
glog.V(4).Infof("getting pod security policies for pod %s (generate: %s)", pod.Name, pod.GenerateName)
var saInfo user.Info
if len(pod.Spec.ServiceAccountName) > 0 {
saInfo = serviceaccount.UserInfo(a.GetNamespace(), pod.Spec.ServiceAccountName, "")
}
matchedPolicies, err := c.pspMatcher(c.store, a.GetUserInfo(), saInfo, c.authz)
if err != nil {
return admission.NewForbidden(a, err)
}
// if we have no policies and want to succeed then return. Otherwise we'll end up with no
// providers and fail with "unable to validate against any pod security policy" below.
if len(matchedPolicies) == 0 && !c.failOnNoPolicies {
return nil
}
providers, errs := c.createProvidersFromPolicies(matchedPolicies, pod.Namespace)
logProviders(pod, providers, errs)
if len(providers) == 0 {
return admission.NewForbidden(a, fmt.Errorf("no providers available to validate pod request"))
}
// all containers in a single pod must validate under a single provider or we will reject the request
validationErrs := field.ErrorList{}
for _, provider := range providers {
if errs := assignSecurityContext(provider, pod, field.NewPath(fmt.Sprintf("provider %s: ", provider.GetPSPName()))); len(errs) > 0 {
validationErrs = append(validationErrs, errs...)
continue
}
// the entire pod validated, annotate and accept the pod
glog.V(4).Infof("pod %s (generate: %s) validated against provider %s", pod.Name, pod.GenerateName, provider.GetPSPName())
if pod.ObjectMeta.Annotations == nil {
pod.ObjectMeta.Annotations = map[string]string{}
}
pod.ObjectMeta.Annotations[psputil.ValidatedPSPAnnotation] = provider.GetPSPName()
return nil
}
// we didn't validate against any provider, reject the pod and give the errors for each attempt
glog.V(4).Infof("unable to validate pod %s (generate: %s) against any pod security policy: %v", pod.Name, pod.GenerateName, validationErrs)
return admission.NewForbidden(a, fmt.Errorf("unable to validate against any pod security policy: %v", validationErrs))
}
// assignSecurityContext creates a security context for each container in the pod
// and validates that the sc falls within the psp constraints. All containers must validate against
// the same psp or is not considered valid.
func assignSecurityContext(provider psp.Provider, pod *api.Pod, fldPath *field.Path) field.ErrorList {
generatedSCs := make([]*api.SecurityContext, len(pod.Spec.Containers))
var generatedInitSCs []*api.SecurityContext
errs := field.ErrorList{}
psc, pscAnnotations, err := provider.CreatePodSecurityContext(pod)
if err != nil {
errs = append(errs, field.Invalid(field.NewPath("spec", "securityContext"), pod.Spec.SecurityContext, err.Error()))
}
// save the original PSC and validate the generated PSC. Leave the generated PSC
// set for container generation/validation. We will reset to original post container
// validation.
originalPSC := pod.Spec.SecurityContext
pod.Spec.SecurityContext = psc
originalAnnotations := maps.CopySS(pod.Annotations)
pod.Annotations = pscAnnotations
errs = append(errs, provider.ValidatePodSecurityContext(pod, field.NewPath("spec", "securityContext"))...)
// Note: this is not changing the original container, we will set container SCs later so long
// as all containers validated under the same PSP.
for i, containerCopy := range pod.Spec.InitContainers {
// We will determine the effective security context for the container and validate against that
// since that is how the sc provider will eventually apply settings in the runtime.
// This results in an SC that is based on the Pod's PSC with the set fields from the container
// overriding pod level settings.
containerCopy.SecurityContext = sc.InternalDetermineEffectiveSecurityContext(pod, &containerCopy)
sc, scAnnotations, err := provider.CreateContainerSecurityContext(pod, &containerCopy)
if err != nil {
errs = append(errs, field.Invalid(field.NewPath("spec", "initContainers").Index(i).Child("securityContext"), "", err.Error()))
continue
}
generatedInitSCs = append(generatedInitSCs, sc)
containerCopy.SecurityContext = sc
pod.Annotations = scAnnotations
errs = append(errs, provider.ValidateContainerSecurityContext(pod, &containerCopy, field.NewPath("spec", "initContainers").Index(i).Child("securityContext"))...)
}
// Note: this is not changing the original container, we will set container SCs later so long
// as all containers validated under the same PSP.
for i, containerCopy := range pod.Spec.Containers {
// We will determine the effective security context for the container and validate against that
// since that is how the sc provider will eventually apply settings in the runtime.
// This results in an SC that is based on the Pod's PSC with the set fields from the container
// overriding pod level settings.
containerCopy.SecurityContext = sc.InternalDetermineEffectiveSecurityContext(pod, &containerCopy)
sc, scAnnotations, err := provider.CreateContainerSecurityContext(pod, &containerCopy)
if err != nil {
errs = append(errs, field.Invalid(field.NewPath("spec", "containers").Index(i).Child("securityContext"), "", err.Error()))
continue
}
generatedSCs[i] = sc
containerCopy.SecurityContext = sc
pod.Annotations = scAnnotations
errs = append(errs, provider.ValidateContainerSecurityContext(pod, &containerCopy, field.NewPath("spec", "containers").Index(i).Child("securityContext"))...)
}
if len(errs) > 0 {
// ensure psc is not mutated if there are errors
pod.Spec.SecurityContext = originalPSC
pod.Annotations = originalAnnotations
return errs
}
// if we've reached this code then we've generated and validated an SC for every container in the
// pod so let's apply what we generated. Note: the psc is already applied.
for i, sc := range generatedInitSCs {
pod.Spec.InitContainers[i].SecurityContext = sc
}
for i, sc := range generatedSCs {
pod.Spec.Containers[i].SecurityContext = sc
}
return nil
}
// createProvidersFromPolicies creates providers from the constraints supplied.
func (c *podSecurityPolicyPlugin) createProvidersFromPolicies(psps []*extensions.PodSecurityPolicy, namespace string) ([]psp.Provider, []error) {
var (
// collected providers
providers []psp.Provider
// collected errors to return
errs []error
)
for _, constraint := range psps {
provider, err := psp.NewSimpleProvider(constraint, namespace, c.strategyFactory)
if err != nil {
errs = append(errs, fmt.Errorf("error creating provider for PSP %s: %v", constraint.Name, err))
continue
}
providers = append(providers, provider)
}
return providers, errs
}
// getMatchingPolicies returns policies from the store. For now this returns everything
// in the future it can filter based on UserInfo and permissions.
//
// TODO: this will likely need optimization since the initial implementation will
// always query for authorization. Needs scale testing and possibly checking against
// a cache.
func getMatchingPolicies(store cache.Store, user user.Info, sa user.Info, authz authorizer.Authorizer) ([]*extensions.PodSecurityPolicy, error) {
matchedPolicies := make([]*extensions.PodSecurityPolicy, 0)
for _, c := range store.List() {
constraint, ok := c.(*extensions.PodSecurityPolicy)
if !ok {
return nil, errors.NewInternalError(fmt.Errorf("error converting object from store to a pod security policy: %v", c))
}
if authorizedForPolicy(user, constraint, authz) || authorizedForPolicy(sa, constraint, authz) {
matchedPolicies = append(matchedPolicies, constraint)
}
}
return matchedPolicies, nil
}
// authorizedForPolicy returns true if info is authorized to perform a "get" on policy.
func authorizedForPolicy(info user.Info, policy *extensions.PodSecurityPolicy, authz authorizer.Authorizer) bool {
// if no info exists then the API is being hit via the unsecured port. In this case
// authorize the request.
if info == nil {
return true
}
attr := buildAttributes(info, policy)
allowed, _, _ := authz.Authorize(attr)
return allowed
}
// buildAttributes builds an attributes record for a SAR based on the user info and policy.
func buildAttributes(info user.Info, policy *extensions.PodSecurityPolicy) authorizer.Attributes {
// TODO consider checking against the namespace that the pod is being
// created in to allow per-namespace PSP definitions.
attr := authorizer.AttributesRecord{
User: info,
Verb: "use",
Name: policy.Name,
APIGroup: extensions.GroupName,
Resource: "podsecuritypolicies",
ResourceRequest: true,
}
return attr
}
// logProviders logs what providers were found for the pod as well as any errors that were encountered
// while creating providers.
func logProviders(pod *api.Pod, providers []psp.Provider, providerCreationErrs []error) {
names := make([]string, len(providers))
for i, p := range providers {
names[i] = p.GetPSPName()
}
glog.V(4).Infof("validating pod %s (generate: %s) against providers %s", pod.Name, pod.GenerateName, strings.Join(names, ","))
for _, err := range providerCreationErrs {
glog.V(4).Infof("provider creation error: %v", err)
}
}