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| 1 | +/* |
| 2 | +Copyright 2020 The Kubernetes Authors. |
| 3 | +
|
| 4 | +Licensed under the Apache License, Version 2.0 (the "License"); |
| 5 | +you may not use this file except in compliance with the License. |
| 6 | +You may obtain a copy of the License at |
| 7 | +
|
| 8 | + http://www.apache.org/licenses/LICENSE-2.0 |
| 9 | +
|
| 10 | +Unless required by applicable law or agreed to in writing, software |
| 11 | +distributed under the License is distributed on an "AS IS" BASIS, |
| 12 | +WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| 13 | +See the License for the specific language governing permissions and |
| 14 | +limitations under the License. |
| 15 | +*/ |
| 16 | + |
| 17 | +package approval |
| 18 | + |
| 19 | +import ( |
| 20 | + "context" |
| 21 | + "fmt" |
| 22 | + "io" |
| 23 | + |
| 24 | + "k8s.io/klog" |
| 25 | + |
| 26 | + "k8s.io/apiserver/pkg/admission" |
| 27 | + genericadmissioninit "k8s.io/apiserver/pkg/admission/initializer" |
| 28 | + "k8s.io/apiserver/pkg/authorization/authorizer" |
| 29 | + |
| 30 | + api "k8s.io/kubernetes/pkg/apis/certificates" |
| 31 | + "k8s.io/kubernetes/plugin/pkg/admission/certificates" |
| 32 | +) |
| 33 | + |
| 34 | +// PluginName is a string with the name of the plugin |
| 35 | +const PluginName = "CertificateApproval" |
| 36 | + |
| 37 | +// Register registers a plugin |
| 38 | +func Register(plugins *admission.Plugins) { |
| 39 | + plugins.Register(PluginName, func(config io.Reader) (admission.Interface, error) { |
| 40 | + return NewPlugin(), nil |
| 41 | + }) |
| 42 | +} |
| 43 | + |
| 44 | +// Plugin holds state for and implements the admission plugin. |
| 45 | +type Plugin struct { |
| 46 | + *admission.Handler |
| 47 | + authz authorizer.Authorizer |
| 48 | +} |
| 49 | + |
| 50 | +// SetAuthorizer sets the authorizer. |
| 51 | +func (p *Plugin) SetAuthorizer(authz authorizer.Authorizer) { |
| 52 | + p.authz = authz |
| 53 | +} |
| 54 | + |
| 55 | +// ValidateInitialization ensures an authorizer is set. |
| 56 | +func (p *Plugin) ValidateInitialization() error { |
| 57 | + if p.authz == nil { |
| 58 | + return fmt.Errorf("%s requires an authorizer", PluginName) |
| 59 | + } |
| 60 | + return nil |
| 61 | +} |
| 62 | + |
| 63 | +var _ admission.ValidationInterface = &Plugin{} |
| 64 | +var _ genericadmissioninit.WantsAuthorizer = &Plugin{} |
| 65 | + |
| 66 | +// NewPlugin creates a new CSR approval admission plugin |
| 67 | +func NewPlugin() *Plugin { |
| 68 | + return &Plugin{ |
| 69 | + Handler: admission.NewHandler(admission.Update), |
| 70 | + } |
| 71 | +} |
| 72 | + |
| 73 | +var csrGroupResource = api.Resource("certificatesigningrequests") |
| 74 | + |
| 75 | +// Validate verifies that the requesting user has permission to approve |
| 76 | +// CertificateSigningRequests for the specified signerName. |
| 77 | +func (p *Plugin) Validate(ctx context.Context, a admission.Attributes, _ admission.ObjectInterfaces) error { |
| 78 | + // Ignore all calls to anything other than 'certificatesigningrequests/approval'. |
| 79 | + // Ignore all operations other than UPDATE. |
| 80 | + if a.GetSubresource() != "approval" || |
| 81 | + a.GetResource().GroupResource() != csrGroupResource { |
| 82 | + return nil |
| 83 | + } |
| 84 | + |
| 85 | + // We check permissions against the *old* version of the resource, in case |
| 86 | + // a user is attempting to update the SignerName when calling the approval |
| 87 | + // endpoint (which is an invalid/not allowed operation) |
| 88 | + csr, ok := a.GetOldObject().(*api.CertificateSigningRequest) |
| 89 | + if !ok { |
| 90 | + return admission.NewForbidden(a, fmt.Errorf("expected type CertificateSigningRequest, got: %T", a.GetOldObject())) |
| 91 | + } |
| 92 | + |
| 93 | + if !certificates.IsAuthorizedForSignerName(ctx, p.authz, a.GetUserInfo(), "approve", csr.Spec.SignerName) { |
| 94 | + klog.V(4).Infof("user not permitted to approve CertificateSigningRequest %q with signerName %q", csr.Name, csr.Spec.SignerName) |
| 95 | + return admission.NewForbidden(a, fmt.Errorf("user not permitted to approve requests with signerName %q", csr.Spec.SignerName)) |
| 96 | + } |
| 97 | + |
| 98 | + return nil |
| 99 | +} |
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