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// Copyright 2018 Google LLC All Rights Reserved.
//
// 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 google
import (
"strings"
"sync"
"github.com/google/go-containerregistry/pkg/authn"
"github.com/google/go-containerregistry/pkg/logs"
)
// Keychain exports an instance of the google Keychain.
var Keychain authn.Keychain = &googleKeychain{}
type googleKeychain struct {
once sync.Once
auth authn.Authenticator
}
// Resolve implements authn.Keychain a la docker-credential-gcr.
//
// This behaves similarly to the GCR credential helper, but reuses tokens until
// they expire.
//
// We can't easily add this behavior to our credential helper implementation
// of authn.Authenticator because the credential helper protocol doesn't include
// expiration information, see here:
// https://godoc.org/github.com/docker/docker-credential-helpers/credentials#Credentials
//
// In addition to being a performance optimization, the reuse of these access
// tokens works around a bug in gcloud. It appears that attempting to invoke
// `gcloud config config-helper` multiple times too quickly will fail:
// https://github.com/GoogleCloudPlatform/docker-credential-gcr/issues/54
//
// We could upstream this behavior into docker-credential-gcr by parsing
// gcloud's output and persisting its tokens across invocations, but then
// we have to deal with invalidating caches across multiple runs (no fun).
//
// In general, we don't worry about that here because we expect to use the same
// gcloud configuration in the scope of this one process.
func (gk *googleKeychain) Resolve(target authn.Resource) (authn.Authenticator, error) {
// Only authenticate GCR and AR so it works with authn.NewMultiKeychain to fallback.
host := target.RegistryStr()
if host != "gcr.io" &&
!strings.HasSuffix(host, ".gcr.io") &&
!strings.HasSuffix(host, ".pkg.dev") &&
!strings.HasSuffix(host, ".google.com") {
return authn.Anonymous, nil
}
gk.once.Do(func() {
gk.auth = resolve()
})
return gk.auth, nil
}
func resolve() authn.Authenticator {
auth, envErr := NewEnvAuthenticator()
if envErr == nil && auth != authn.Anonymous {
logs.Debug.Println("google.Keychain: using Application Default Credentials")
return auth
}
auth, gErr := NewGcloudAuthenticator()
if gErr == nil && auth != authn.Anonymous {
logs.Debug.Println("google.Keychain: using gcloud fallback")
return auth
}
logs.Debug.Println("Failed to get any Google credentials, falling back to Anonymous")
if envErr != nil {
logs.Debug.Printf("Google env error: %v", envErr)
}
if gErr != nil {
logs.Debug.Printf("gcloud error: %v", gErr)
}
return authn.Anonymous
}
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