1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
|
// Copyright 2020 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 subtle
import (
"crypto/ecdsa"
"crypto/rand"
"errors"
"fmt"
"hash"
"math/big"
"github.com/tink-crypto/tink-go/v2/subtle"
)
// ECDSASigner is an implementation of Signer for ECDSA.
// At the moment, the implementation only accepts DER encoding.
type ECDSASigner struct {
privateKey *ecdsa.PrivateKey
hashFunc func() hash.Hash
encoding string
}
// NewECDSASigner creates a new instance of ECDSASigner.
func NewECDSASigner(hashAlg, curve, encoding string, keyValue []byte) (*ECDSASigner, error) {
privKey := new(ecdsa.PrivateKey)
c := subtle.GetCurve(curve)
if c == nil {
return nil, errors.New("ecdsa_signer: invalid curve")
}
privKey.PublicKey.Curve = c
privKey.D = new(big.Int).SetBytes(keyValue)
privKey.PublicKey.X, privKey.PublicKey.Y = c.ScalarBaseMult(keyValue)
return NewECDSASignerFromPrivateKey(hashAlg, encoding, privKey)
}
// NewECDSASignerFromPrivateKey creates a new instance of ECDSASigner
func NewECDSASignerFromPrivateKey(hashAlg, encoding string, privateKey *ecdsa.PrivateKey) (*ECDSASigner, error) {
if privateKey.Curve == nil {
return nil, errors.New("ecdsa_signer: privateKey.Curve can't be nil")
}
curve := subtle.ConvertCurveName(privateKey.Curve.Params().Name)
if err := ValidateECDSAParams(hashAlg, curve, encoding); err != nil {
return nil, fmt.Errorf("ecdsa_signer: %s", err)
}
hashFunc := subtle.GetHashFunc(hashAlg)
return &ECDSASigner{
privateKey: privateKey,
hashFunc: hashFunc,
encoding: encoding,
}, nil
}
// Sign computes a signature for the given data.
func (e *ECDSASigner) Sign(data []byte) ([]byte, error) {
hashed, err := subtle.ComputeHash(e.hashFunc, data)
if err != nil {
return nil, err
}
var signatureBytes []byte
switch e.encoding {
case "IEEE_P1363":
r, s, err := ecdsa.Sign(rand.Reader, e.privateKey, hashed)
if err != nil {
return nil, err
}
sig := NewECDSASignature(r, s)
signatureBytes, err = sig.EncodeECDSASignature(e.encoding, e.privateKey.PublicKey.Curve.Params().Name)
if err != nil {
return nil, fmt.Errorf("ecdsa_signer: signing failed: %s", err)
}
case "DER":
signatureBytes, err = ecdsa.SignASN1(rand.Reader, e.privateKey, hashed)
if err != nil {
return nil, fmt.Errorf("ecdsa_signer: signing failed: %s", err)
}
default:
return nil, fmt.Errorf("ecdsa_signer: unsupported encoding: %s", e.encoding)
}
return signatureBytes, nil
}
|
