certificates/kms/cloudkms/signer.go
2020-01-15 19:32:26 -08:00

78 lines
1.7 KiB
Go

package cloudkms
import (
"crypto"
"io"
"github.com/pkg/errors"
"github.com/smallstep/cli/crypto/pemutil"
kmspb "google.golang.org/genproto/googleapis/cloud/kms/v1"
)
// signer implements a crypto.Signer using Google's Cloud KMS.
type signer struct {
client keyManagementClient
signingKey string
}
func newSigner(c keyManagementClient, signingKey string) *signer {
return &signer{
client: c,
signingKey: signingKey,
}
}
// Public returns the public key of this signer or an error.
func (s *signer) Public() crypto.PublicKey {
ctx, cancel := defaultContext()
defer cancel()
response, err := s.client.GetPublicKey(ctx, &kmspb.GetPublicKeyRequest{
Name: s.signingKey,
})
if err != nil {
return errors.Wrap(err, "cloudKMS GetPublicKey failed")
}
pk, err := pemutil.ParseKey([]byte(response.Pem))
if err != nil {
return err
}
return pk
}
// Sign signs digest with the private key stored in Google's Cloud KMS.
func (s *signer) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
req := &kmspb.AsymmetricSignRequest{
Name: s.signingKey,
Digest: &kmspb.Digest{},
}
switch h := opts.HashFunc(); h {
case crypto.SHA256:
req.Digest.Digest = &kmspb.Digest_Sha256{
Sha256: digest,
}
case crypto.SHA384:
req.Digest.Digest = &kmspb.Digest_Sha384{
Sha384: digest,
}
case crypto.SHA512:
req.Digest.Digest = &kmspb.Digest_Sha512{
Sha512: digest,
}
default:
return nil, errors.Errorf("unsupported hash function %v", h)
}
ctx, cancel := defaultContext()
defer cancel()
response, err := s.client.AsymmetricSign(ctx, req)
if err != nil {
return nil, errors.Wrap(err, "cloudKMS AsymmetricSign failed")
}
return response.Signature, nil
}