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Replace SHA-1 with SHA-256 for X.509 SubjectKeyIdentifier computation #41

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Replace SHA-1 with SHA-256 for X.509 SubjectKeyIdentifier computation #41

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22 changes: 15 additions & 7 deletions types/certificate_generator.go
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Original file line number Diff line number Diff line change
Expand Up @@ -3,15 +3,14 @@ package types
import (
"crypto/rand"
"crypto/rsa"
"crypto/sha256"
"crypto/x509"
"crypto/x509/pkix"
"encoding/pem"
"math/big"
"net"
"time"

"crypto/sha1"

"github.com/cloudfoundry/bosh-utils/errors"
)

Expand Down Expand Up @@ -60,10 +59,15 @@ func (cfg CertificateGenerator) Generate(parameters interface{}) (interface{}, e
return cfg.generateCertificate(params)
}

func (cfg CertificateGenerator) bigIntHash(n *big.Int) []byte {
h := sha1.New()
h.Write(n.Bytes())
return h.Sum(nil)
// computeSubjectKeyId derives the SubjectKeyIdentifier per RFC 7093 Method 4:
// SHA-256 of the full DER-encoded SubjectPublicKeyInfo structure.
func computeSubjectKeyId(pub *rsa.PublicKey) ([]byte, error) {
pubDER, err := x509.MarshalPKIXPublicKey(pub)
if err != nil {
return nil, err
}
hash := sha256.Sum256(pubDER)
return hash[:], nil
}

func (cfg CertificateGenerator) generateCertificate(cParams certParams) (CertResponse, error) {
Expand Down Expand Up @@ -94,7 +98,11 @@ func (cfg CertificateGenerator) generateCertificate(cParams certParams) (CertRes
}
}

certTemplate.SubjectKeyId = cfg.bigIntHash(privateKey.N)
subjectKeyId, err := computeSubjectKeyId(&privateKey.PublicKey)
if err != nil {
return certResponse, errors.WrapError(err, "Computing SubjectKeyId")
}
certTemplate.SubjectKeyId = subjectKeyId

if cParams.IsCA {
certTemplate.KeyUsage = x509.KeyUsageCertSign | x509.KeyUsageCRLSign
Expand Down