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//
// Copyright 2022 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 fulcioroots fetches Fulcio root and intermediate certificates from TUF metadata
package fulcioroots
import (
"bytes"
"context"
"crypto/x509"
"errors"
"fmt"
"sync"
"github.com/sigstore/sigstore/pkg/cryptoutils"
"github.com/sigstore/sigstore/pkg/tuf"
)
var (
rootsOnce sync.Once
roots []*x509.Certificate
intermediates []*x509.Certificate
singletonRootErr error
)
// This is the root in the fulcio project.
var fulcioTargetStr = `fulcio.crt.pem`
// This is the v1 migrated root.
var fulcioV1TargetStr = `fulcio_v1.crt.pem`
// This is the untrusted v1 intermediate CA certificate, used or chain building.
var fulcioV1IntermediateTargetStr = `fulcio_intermediate_v1.crt.pem`
// Get returns the Fulcio root certificate.
func Get() (*x509.CertPool, error) {
pool := x509.NewCertPool()
if err := GetWithCertPool(pool); err != nil {
return nil, err
}
return pool, nil
}
// GetWithCertPool returns the Fulcio root certificate appended to the given CertPool.
func GetWithCertPool(pool *x509.CertPool) error {
rootsOnce.Do(func() {
roots, intermediates, singletonRootErr = initRoots()
if singletonRootErr != nil {
return
}
})
if singletonRootErr != nil {
return singletonRootErr
}
for _, c := range roots {
pool.AddCert(c)
}
return nil
}
// GetIntermediates returns the Fulcio intermediate certificates.
func GetIntermediates() (*x509.CertPool, error) {
pool := x509.NewCertPool()
if err := GetIntermediatesWithCertPool(pool); err != nil {
return nil, err
}
return pool, nil
}
// GetIntermediatesWithCertPool returns the Fulcio intermediate certificates appended to the given CertPool.
func GetIntermediatesWithCertPool(pool *x509.CertPool) error {
rootsOnce.Do(func() {
roots, intermediates, singletonRootErr = initRoots()
if singletonRootErr != nil {
return
}
})
if singletonRootErr != nil {
return singletonRootErr
}
for _, c := range intermediates {
pool.AddCert(c)
}
return nil
}
func initRoots() ([]*x509.Certificate, []*x509.Certificate, error) {
tufClient, err := tuf.NewFromEnv(context.Background())
if err != nil {
return nil, nil, fmt.Errorf("initializing tuf: %w", err)
}
// Retrieve from the embedded or cached TUF root. If expired, a network
// call is made to update the root.
targets, err := tufClient.GetTargetsByMeta(tuf.Fulcio, []string{fulcioTargetStr, fulcioV1TargetStr, fulcioV1IntermediateTargetStr})
if err != nil {
return nil, nil, fmt.Errorf("error getting targets: %w", err)
}
if len(targets) == 0 {
return nil, nil, errors.New("none of the Fulcio roots have been found")
}
rootPool := []*x509.Certificate{}
intermediatePool := []*x509.Certificate{}
for _, t := range targets {
certs, err := cryptoutils.UnmarshalCertificatesFromPEM(t.Target)
if err != nil {
return nil, nil, fmt.Errorf("error unmarshalling certificates: %w", err)
}
for _, cert := range certs {
// root certificates are self-signed
if bytes.Equal(cert.RawSubject, cert.RawIssuer) {
rootPool = append(rootPool, cert)
} else {
intermediatePool = append(intermediatePool, cert)
}
}
}
return rootPool, intermediatePool, nil
}
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