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|
//go:build !noawskms
// +build !noawskms
package awskms
import (
"crypto"
"crypto/ecdsa"
"crypto/rsa"
"io"
"github.com/aws/aws-sdk-go-v2/service/kms"
"github.com/aws/aws-sdk-go-v2/service/kms/types"
"github.com/pkg/errors"
"go.step.sm/crypto/pemutil"
)
// Signer implements a crypto.Signer using the AWS KMS.
type Signer struct {
client KeyManagementClient
keyID string
publicKey crypto.PublicKey
}
// NewSigner creates a new signer using a key in the AWS KMS.
func NewSigner(client KeyManagementClient, signingKey string) (*Signer, error) {
keyID, err := parseKeyID(signingKey)
if err != nil {
return nil, err
}
// Make sure that the key exists.
signer := &Signer{
client: client,
keyID: keyID,
}
if err := signer.preloadKey(keyID); err != nil {
return nil, err
}
return signer, nil
}
func (s *Signer) preloadKey(keyID string) error {
ctx, cancel := defaultContext()
defer cancel()
resp, err := s.client.GetPublicKey(ctx, &kms.GetPublicKeyInput{
KeyId: pointer(keyID),
})
if err != nil {
return errors.Wrap(err, "awskms GetPublicKey failed")
}
s.publicKey, err = pemutil.ParseDER(resp.PublicKey)
return err
}
// Public returns the public key of this signer or an error.
func (s *Signer) Public() crypto.PublicKey {
return s.publicKey
}
// Sign signs digest with the private key stored in the AWS KMS.
func (s *Signer) Sign(_ io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
alg, err := getSigningAlgorithm(s.Public(), opts)
if err != nil {
return nil, err
}
req := &kms.SignInput{
KeyId: pointer(s.keyID),
SigningAlgorithm: alg,
Message: digest,
MessageType: types.MessageTypeDigest,
}
ctx, cancel := defaultContext()
defer cancel()
resp, err := s.client.Sign(ctx, req)
if err != nil {
return nil, errors.Wrap(err, "awskms Sign failed")
}
return resp.Signature, nil
}
func getSigningAlgorithm(key crypto.PublicKey, opts crypto.SignerOpts) (types.SigningAlgorithmSpec, error) {
switch key.(type) {
case *rsa.PublicKey:
_, isPSS := opts.(*rsa.PSSOptions)
switch h := opts.HashFunc(); h {
case crypto.SHA256:
if isPSS {
return types.SigningAlgorithmSpecRsassaPssSha256, nil
}
return types.SigningAlgorithmSpecRsassaPkcs1V15Sha256, nil
case crypto.SHA384:
if isPSS {
return types.SigningAlgorithmSpecRsassaPssSha384, nil
}
return types.SigningAlgorithmSpecRsassaPkcs1V15Sha384, nil
case crypto.SHA512:
if isPSS {
return types.SigningAlgorithmSpecRsassaPssSha512, nil
}
return types.SigningAlgorithmSpecRsassaPkcs1V15Sha512, nil
default:
return "", errors.Errorf("unsupported hash function %v", h)
}
case *ecdsa.PublicKey:
switch h := opts.HashFunc(); h {
case crypto.SHA256:
return types.SigningAlgorithmSpecEcdsaSha256, nil
case crypto.SHA384:
return types.SigningAlgorithmSpecEcdsaSha384, nil
case crypto.SHA512:
return types.SigningAlgorithmSpecEcdsaSha512, nil
default:
return "", errors.Errorf("unsupported hash function %v", h)
}
default:
return "", errors.Errorf("unsupported key type %T", key)
}
}
|
