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1
2
3
4
5 package x509
6
7 import (
8 "crypto/ecdsa"
9 "crypto/elliptic"
10 "encoding/asn1"
11 "errors"
12 "fmt"
13 "math/big"
14 )
15
16 const ecPrivKeyVersion = 1
17
18
19
20
21
22
23
24 type ecPrivateKey struct {
25 Version int
26 PrivateKey []byte
27 NamedCurveOID asn1.ObjectIdentifier `asn1:"optional,explicit,tag:0"`
28 PublicKey asn1.BitString `asn1:"optional,explicit,tag:1"`
29 }
30
31
32 func ParseECPrivateKey(der []byte) (*ecdsa.PrivateKey, error) {
33 return parseECPrivateKey(nil, der)
34 }
35
36
37 func MarshalECPrivateKey(key *ecdsa.PrivateKey) ([]byte, error) {
38 oid, ok := oidFromNamedCurve(key.Curve)
39 if !ok {
40 return nil, errors.New("x509: unknown elliptic curve")
41 }
42
43 return marshalECPrivateKeyWithOID(key, oid)
44 }
45
46
47
48 func marshalECPrivateKeyWithOID(key *ecdsa.PrivateKey, oid asn1.ObjectIdentifier) ([]byte, error) {
49 privateKeyBytes := key.D.Bytes()
50 paddedPrivateKey := make([]byte, (key.Curve.Params().N.BitLen()+7)/8)
51 copy(paddedPrivateKey[len(paddedPrivateKey)-len(privateKeyBytes):], privateKeyBytes)
52
53 return asn1.Marshal(ecPrivateKey{
54 Version: 1,
55 PrivateKey: paddedPrivateKey,
56 NamedCurveOID: oid,
57 PublicKey: asn1.BitString{Bytes: elliptic.Marshal(key.Curve, key.X, key.Y)},
58 })
59 }
60
61
62
63
64
65 func parseECPrivateKey(namedCurveOID *asn1.ObjectIdentifier, der []byte) (key *ecdsa.PrivateKey, err error) {
66 var privKey ecPrivateKey
67 if _, err := asn1.Unmarshal(der, &privKey); err != nil {
68 return nil, errors.New("x509: failed to parse EC private key: " + err.Error())
69 }
70 if privKey.Version != ecPrivKeyVersion {
71 return nil, fmt.Errorf("x509: unknown EC private key version %d", privKey.Version)
72 }
73
74 var curve elliptic.Curve
75 if namedCurveOID != nil {
76 curve = namedCurveFromOID(*namedCurveOID)
77 } else {
78 curve = namedCurveFromOID(privKey.NamedCurveOID)
79 }
80 if curve == nil {
81 return nil, errors.New("x509: unknown elliptic curve")
82 }
83
84 k := new(big.Int).SetBytes(privKey.PrivateKey)
85 curveOrder := curve.Params().N
86 if k.Cmp(curveOrder) >= 0 {
87 return nil, errors.New("x509: invalid elliptic curve private key value")
88 }
89 priv := new(ecdsa.PrivateKey)
90 priv.Curve = curve
91 priv.D = k
92
93 privateKey := make([]byte, (curveOrder.BitLen()+7)/8)
94
95
96
97 for len(privKey.PrivateKey) > len(privateKey) {
98 if privKey.PrivateKey[0] != 0 {
99 return nil, errors.New("x509: invalid private key length")
100 }
101 privKey.PrivateKey = privKey.PrivateKey[1:]
102 }
103
104
105
106
107 copy(privateKey[len(privateKey)-len(privKey.PrivateKey):], privKey.PrivateKey)
108 priv.X, priv.Y = curve.ScalarBaseMult(privateKey)
109
110 return priv, nil
111 }
112
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