/
gcptokensource.go
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/
gcptokensource.go
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// Copyright 2022 The kpt 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 gcptokensource
import (
"context"
"fmt"
"time"
iamv1 "cloud.google.com/go/iam/credentials/apiv1"
"github.com/golang/protobuf/ptypes"
"golang.org/x/oauth2"
"google.golang.org/api/option"
iampb "google.golang.org/genproto/googleapis/iam/credentials/v1"
"k8s.io/klog/v2"
)
// New returns an oauth2.TokenSource that exchanges tokens from ts for tokens
// that authenticate as GCP Service Accounts.
func New(gcpServiceAccount string, scopes []string, tokenSource oauth2.TokenSource) oauth2.TokenSource {
// The cloud-platform scope is always required for the token exchange.
scopes = append(scopes, "https://www.googleapis.com/auth/cloud-platform")
return &gcpTokenSource{
gcpServiceAccount: gcpServiceAccount,
scopes: scopes,
tokenSource: tokenSource,
}
}
// gcpTokenSource produces tokens that authenticate as GCP ServiceAccounts.
type gcpTokenSource struct {
gcpServiceAccount string
scopes []string
tokenSource oauth2.TokenSource
}
// ensure gcpTokenSource implements oauth2.TokenSource
var _ oauth2.TokenSource = &gcpTokenSource{}
// Token exchanges the input token for a GCP SA token.
func (ts *gcpTokenSource) Token() (*oauth2.Token, error) {
ctx, cancel := context.WithTimeout(context.Background(), 10*time.Second)
defer cancel()
// use the provided token source to make the request
c, err := iamv1.NewIamCredentialsClient(ctx, option.WithTokenSource(ts.tokenSource))
if err != nil {
return nil, fmt.Errorf("failed to construct IAM client: %w", err)
}
resp, err := c.GenerateAccessToken(ctx,
&iampb.GenerateAccessTokenRequest{
Name: "projects/-/serviceAccounts/" + ts.gcpServiceAccount,
Scope: ts.scopes,
})
if err != nil {
return nil, fmt.Errorf("token exchange for GCP serviceaccount %q failed: %w", ts.gcpServiceAccount, err)
}
klog.Infof("got GCP token for %v", ts.gcpServiceAccount)
expiry, err := ptypes.Timestamp(resp.ExpireTime)
if err != nil {
return nil, fmt.Errorf("failed to parse expire time on returned token: %w", err)
}
return &oauth2.Token{
AccessToken: resp.AccessToken,
Expiry: expiry,
}, nil
}