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//
// Copyright 2021 The Sigstore 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 google
import (
"context"
"os"
"strings"
"google.golang.org/api/idtoken"
"google.golang.org/api/impersonate"
"github.com/sigstore/cosign/v2/pkg/cosign/env"
"github.com/sigstore/cosign/v2/pkg/providers"
)
func init() {
providers.Register("google-workload-identity", &googleWorkloadIdentity{})
providers.Register("google-impersonate", &googleImpersonate{})
}
type googleWorkloadIdentity struct{}
var _ providers.Interface = (*googleWorkloadIdentity)(nil)
// gceProductNameFile is the product file path that contains the cloud service name.
// This is a variable instead of a const to enable testing.
var gceProductNameFile = "/sys/class/dmi/id/product_name"
// Enabled implements providers.Interface
// This is based on k8s.io/kubernetes/pkg/credentialprovider/gcp
func (gwi *googleWorkloadIdentity) Enabled(ctx context.Context) bool {
data, err := os.ReadFile(gceProductNameFile)
if err != nil {
return false
}
name := strings.TrimSpace(string(data))
if name == "Google" || name == "Google Compute Engine" {
// Just because we're on Google, does not mean workload identity is available.
// TODO(mattmoor): do something better than this.
_, err := gwi.Provide(ctx, "garbage")
return err == nil
}
return false
}
// Provide implements providers.Interface
func (gwi *googleWorkloadIdentity) Provide(ctx context.Context, audience string) (string, error) {
ts, err := idtoken.NewTokenSource(ctx, audience)
if err != nil {
return "", err
}
tok, err := ts.Token()
if err != nil {
return "", err
}
return tok.AccessToken, nil
}
type googleImpersonate struct{}
var _ providers.Interface = (*googleImpersonate)(nil)
// Enabled implements providers.Interface
func (gi *googleImpersonate) Enabled(_ context.Context) bool {
// The "impersonate" method requires a target service account to impersonate.
return env.Getenv(env.VariableGoogleServiceAccountName) != ""
}
// Provide implements providers.Interface
func (gi *googleImpersonate) Provide(ctx context.Context, audience string) (string, error) {
target := env.Getenv(env.VariableGoogleServiceAccountName)
ts, err := impersonate.IDTokenSource(ctx, impersonate.IDTokenConfig{
Audience: audience,
TargetPrincipal: target,
IncludeEmail: true,
})
if err != nil {
return "", err
}
tok, err := ts.Token()
if err != nil {
return "", err
}
return tok.AccessToken, nil
}
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