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// Copyright 2022 Google LLC
//
// 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 rsassapss
import (
"crypto/rand"
"crypto/rsa"
"fmt"
"math/big"
"google.golang.org/protobuf/proto"
"github.com/tink-crypto/tink-go/v2/core/registry"
"github.com/tink-crypto/tink-go/v2/internal/internalapi"
"github.com/tink-crypto/tink-go/v2/internal/protoserialization"
internal "github.com/tink-crypto/tink-go/v2/internal/signature"
"github.com/tink-crypto/tink-go/v2/keyset"
commonpb "github.com/tink-crypto/tink-go/v2/proto/common_go_proto"
rsassapsspb "github.com/tink-crypto/tink-go/v2/proto/rsa_ssa_pss_go_proto"
tinkpb "github.com/tink-crypto/tink-go/v2/proto/tink_go_proto"
)
const (
signerKeyVersion = 0
signerTypeURL = "type.googleapis.com/google.crypto.tink.RsaSsaPssPrivateKey"
)
type signerKeyManager struct{}
var _ registry.PrivateKeyManager = (*signerKeyManager)(nil)
func hashName(h commonpb.HashType) string { return commonpb.HashType_name[int32(h)] }
func (km *signerKeyManager) Primitive(serializedKey []byte) (any, error) {
keySerialization, err := protoserialization.NewKeySerialization(&tinkpb.KeyData{
TypeUrl: signerTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_ASYMMETRIC_PRIVATE,
}, tinkpb.OutputPrefixType_RAW, 0)
if err != nil {
return nil, err
}
key, err := protoserialization.ParseKey(keySerialization)
if err != nil {
return nil, err
}
signerKey, ok := key.(*PrivateKey)
if !ok {
return nil, fmt.Errorf("rsassapss_signer_key_manager: invalid key type: got %T, want %T", key, (*PrivateKey)(nil))
}
return NewSigner(signerKey, internalapi.Token{})
}
func validateRSAPSSPrivateKey(privKey *rsassapsspb.RsaSsaPssPrivateKey) error {
if err := keyset.ValidateKeyVersion(privKey.GetVersion(), signerKeyVersion); err != nil {
return err
}
if err := validateRSAPSSPublicKey(privKey.GetPublicKey()); err != nil {
return err
}
if len(privKey.GetD()) == 0 ||
len(privKey.GetPublicKey().GetN()) == 0 ||
len(privKey.GetPublicKey().GetE()) == 0 ||
len(privKey.GetP()) == 0 ||
len(privKey.GetQ()) == 0 ||
len(privKey.GetDp()) == 0 ||
len(privKey.GetDq()) == 0 ||
len(privKey.GetCrt()) == 0 {
return fmt.Errorf("rsassapss_signer_key_manager: invalid key")
}
return nil
}
func (km *signerKeyManager) PublicKeyData(serializedPrivKey []byte) (*tinkpb.KeyData, error) {
privKey := &rsassapsspb.RsaSsaPssPrivateKey{}
if err := proto.Unmarshal(serializedPrivKey, privKey); err != nil {
return nil, err
}
if err := validateRSAPSSPrivateKey(privKey); err != nil {
return nil, err
}
serializedPubKey, err := proto.Marshal(privKey.GetPublicKey())
if err != nil {
return nil, err
}
return &tinkpb.KeyData{
TypeUrl: verifierTypeURL,
Value: serializedPubKey,
KeyMaterialType: tinkpb.KeyData_ASYMMETRIC_PUBLIC,
}, nil
}
func (km *signerKeyManager) NewKey(serializedKeyFormat []byte) (proto.Message, error) {
if len(serializedKeyFormat) == 0 {
return nil, fmt.Errorf("rsassapss_signer_key_manager: invalid key format")
}
keyFormat := &rsassapsspb.RsaSsaPssKeyFormat{}
if err := proto.Unmarshal(serializedKeyFormat, keyFormat); err != nil {
return nil, err
}
params := keyFormat.GetParams()
if params.GetSigHash() != params.GetMgf1Hash() {
return nil, fmt.Errorf("rsassapss_signer_key_manager: rsassapss hash and mgf1 hash must be the same")
}
if params.GetSaltLength() < 0 {
return nil, fmt.Errorf("rsassapss_signer_key_manager: salt length can't be negative")
}
if err := internal.ValidateRSAPublicKeyParams(params.GetSigHash(), int(keyFormat.GetModulusSizeInBits()), keyFormat.GetPublicExponent()); err != nil {
return nil, err
}
privKey, err := rsa.GenerateKey(rand.Reader, int(keyFormat.GetModulusSizeInBits()))
if err != nil {
return nil, err
}
return &rsassapsspb.RsaSsaPssPrivateKey{
Version: signerKeyVersion,
PublicKey: &rsassapsspb.RsaSsaPssPublicKey{
Version: signerKeyVersion,
Params: keyFormat.GetParams(),
N: privKey.PublicKey.N.Bytes(),
E: big.NewInt(int64(privKey.PublicKey.E)).Bytes(),
},
D: privKey.D.Bytes(),
P: privKey.Primes[0].Bytes(),
Q: privKey.Primes[1].Bytes(),
Dp: privKey.Precomputed.Dp.Bytes(),
Dq: privKey.Precomputed.Dq.Bytes(),
// In crypto/rsa `Qinv` is the "Chinese Remainder Theorem
// coefficient q^(-1) mod p". This corresponds with `Crt` in
// the Tink proto. This is unrelated to `CRTValues`, which
// contains values specifically for additional primes, which
// are not supported by Tink.
Crt: privKey.Precomputed.Qinv.Bytes(),
}, nil
}
func (km *signerKeyManager) NewKeyData(serializedKeyFormat []byte) (*tinkpb.KeyData, error) {
key, err := km.NewKey(serializedKeyFormat)
if err != nil {
return nil, err
}
serializedKey, err := proto.Marshal(key)
if err != nil {
return nil, err
}
return &tinkpb.KeyData{
TypeUrl: signerTypeURL,
Value: serializedKey,
KeyMaterialType: tinkpb.KeyData_ASYMMETRIC_PRIVATE,
}, nil
}
func (km *signerKeyManager) DoesSupport(typeURL string) bool {
return typeURL == signerTypeURL
}
func (km *signerKeyManager) TypeURL() string {
return signerTypeURL
}
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