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// Copyright The Notary Project 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 x509
import (
"bytes"
"crypto/x509"
"fmt"
"strings"
"time"
"github.com/notaryproject/notation-core-go/signature"
)
func isSelfSigned(cert *x509.Certificate) (bool, error) {
return isIssuedBy(cert, cert)
}
func isIssuedBy(subject *x509.Certificate, issuer *x509.Certificate) (bool, error) {
if err := subject.CheckSignatureFrom(issuer); err != nil {
return false, err
}
return bytes.Equal(issuer.RawSubject, subject.RawIssuer), nil
}
func validateSigningTime(cert *x509.Certificate, signingTime *time.Time) error {
if signingTime != nil && (signingTime.Before(cert.NotBefore) || signingTime.After(cert.NotAfter)) {
return fmt.Errorf("certificate with subject %q was invalid at signing time of %s. Certificate is valid from [%s] to [%s]",
cert.Subject, signingTime.UTC(), cert.NotBefore.UTC(), cert.NotAfter.UTC())
}
return nil
}
func validateCABasicConstraints(cert *x509.Certificate, expectedPathLen int) error {
if !cert.BasicConstraintsValid || !cert.IsCA {
return fmt.Errorf("certificate with subject %q: ca field in basic constraints must be present, critical, and set to true", cert.Subject)
}
maxPathLen := cert.MaxPathLen
isMaxPathLenPresent := maxPathLen > 0 || (maxPathLen == 0 && cert.MaxPathLenZero)
if isMaxPathLenPresent && maxPathLen < expectedPathLen {
return fmt.Errorf("certificate with subject %q: expected path length of %d but certificate has path length %d instead", cert.Subject, expectedPathLen, maxPathLen)
}
return nil
}
func validateLeafBasicConstraints(cert *x509.Certificate) error {
if cert.BasicConstraintsValid && cert.IsCA {
return fmt.Errorf("certificate with subject %q: if the basic constraints extension is present, the ca field must be set to false", cert.Subject)
}
return nil
}
func validateLeafKeyUsage(cert *x509.Certificate) error {
if cert.KeyUsage&x509.KeyUsageDigitalSignature == 0 {
return fmt.Errorf("the certificate with subject %q is invalid. The key usage must have the bit positions for \"Digital Signature\" set", cert.Subject)
}
var invalidKeyUsages []string
if cert.KeyUsage&x509.KeyUsageKeyEncipherment != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"KeyEncipherment"`)
}
if cert.KeyUsage&x509.KeyUsageDataEncipherment != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"DataEncipherment"`)
}
if cert.KeyUsage&x509.KeyUsageKeyAgreement != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"KeyAgreement"`)
}
if cert.KeyUsage&x509.KeyUsageCertSign != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"CertSign"`)
}
if cert.KeyUsage&x509.KeyUsageCRLSign != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"CRLSign"`)
}
if cert.KeyUsage&x509.KeyUsageEncipherOnly != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"EncipherOnly"`)
}
if cert.KeyUsage&x509.KeyUsageDecipherOnly != 0 {
invalidKeyUsages = append(invalidKeyUsages, `"DecipherOnly"`)
}
if len(invalidKeyUsages) > 0 {
return fmt.Errorf("the certificate with subject %q is invalid. The key usage must be \"Digital Signature\" only, but found %s", cert.Subject, strings.Join(invalidKeyUsages, ", "))
}
return nil
}
func validateSignatureAlgorithm(cert *x509.Certificate) error {
keySpec, err := signature.ExtractKeySpec(cert)
if err != nil {
return fmt.Errorf("certificate with subject %q: %w", cert.Subject, err)
}
if keySpec.SignatureAlgorithm() == 0 {
return fmt.Errorf("certificate with subject %q: unsupported signature algorithm with key spec %+v", cert.Subject, keySpec)
}
return nil
}
func ekuToString(eku x509.ExtKeyUsage) string {
switch eku {
case x509.ExtKeyUsageAny:
return "Any"
case x509.ExtKeyUsageServerAuth:
return "ServerAuth"
case x509.ExtKeyUsageClientAuth:
return "ClientAuth"
case x509.ExtKeyUsageOCSPSigning:
return "OCSPSigning"
case x509.ExtKeyUsageEmailProtection:
return "EmailProtection"
case x509.ExtKeyUsageCodeSigning:
return "CodeSigning"
case x509.ExtKeyUsageTimeStamping:
return "Timestamping"
default:
return fmt.Sprintf("%d", int(eku))
}
}
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