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// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package x509
import (
"crypto/ecdh"
"crypto/ecdsa"
"crypto/ed25519"
"crypto/rsa"
"crypto/x509/pkix"
"encoding/asn1"
"errors"
"fmt"
)
// pkcs8 reflects an ASN.1, PKCS #8 PrivateKey. See
// ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-8/pkcs-8v1_2.asn
// and RFC 5208.
type pkcs8 struct {
Version int
Algo pkix.AlgorithmIdentifier
PrivateKey []byte
// optional attributes omitted.
}
// ParsePKCS8PrivateKey parses an unencrypted private key in PKCS #8, ASN.1 DER form.
//
// It returns a *rsa.PrivateKey, an *ecdsa.PrivateKey, an ed25519.PrivateKey (not
// a pointer), or an *ecdh.PrivateKey (for X25519). More types might be supported
// in the future.
//
// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
func ParsePKCS8PrivateKey(der []byte) (key any, err error) {
var privKey pkcs8
if _, err := asn1.Unmarshal(der, &privKey); err != nil {
if _, err := asn1.Unmarshal(der, &ecPrivateKey{}); err == nil {
return nil, errors.New("x509: failed to parse private key (use ParseECPrivateKey instead for this key format)")
}
if _, err := asn1.Unmarshal(der, &pkcs1PrivateKey{}); err == nil {
return nil, errors.New("x509: failed to parse private key (use ParsePKCS1PrivateKey instead for this key format)")
}
return nil, err
}
switch {
case privKey.Algo.Algorithm.Equal(oidPublicKeyRSA):
key, err = ParsePKCS1PrivateKey(privKey.PrivateKey)
if err != nil {
return nil, errors.New("x509: failed to parse RSA private key embedded in PKCS#8: " + err.Error())
}
return key, nil
case privKey.Algo.Algorithm.Equal(oidPublicKeyECDSA):
bytes := privKey.Algo.Parameters.FullBytes
namedCurveOID := new(asn1.ObjectIdentifier)
if _, err := asn1.Unmarshal(bytes, namedCurveOID); err != nil {
namedCurveOID = nil
}
key, err = parseECPrivateKey(namedCurveOID, privKey.PrivateKey)
if err != nil {
return nil, errors.New("x509: failed to parse EC private key embedded in PKCS#8: " + err.Error())
}
return key, nil
case privKey.Algo.Algorithm.Equal(oidPublicKeyEd25519):
if l := len(privKey.Algo.Parameters.FullBytes); l != 0 {
return nil, errors.New("x509: invalid Ed25519 private key parameters")
}
var curvePrivateKey []byte
if _, err := asn1.Unmarshal(privKey.PrivateKey, &curvePrivateKey); err != nil {
return nil, fmt.Errorf("x509: invalid Ed25519 private key: %v", err)
}
if l := len(curvePrivateKey); l != ed25519.SeedSize {
return nil, fmt.Errorf("x509: invalid Ed25519 private key length: %d", l)
}
return ed25519.NewKeyFromSeed(curvePrivateKey), nil
case privKey.Algo.Algorithm.Equal(oidPublicKeyX25519):
if l := len(privKey.Algo.Parameters.FullBytes); l != 0 {
return nil, errors.New("x509: invalid X25519 private key parameters")
}
var curvePrivateKey []byte
if _, err := asn1.Unmarshal(privKey.PrivateKey, &curvePrivateKey); err != nil {
return nil, fmt.Errorf("x509: invalid X25519 private key: %v", err)
}
return ecdh.X25519().NewPrivateKey(curvePrivateKey)
default:
return nil, fmt.Errorf("x509: PKCS#8 wrapping contained private key with unknown algorithm: %v", privKey.Algo.Algorithm)
}
}
// MarshalPKCS8PrivateKey converts a private key to PKCS #8, ASN.1 DER form.
//
// The following key types are currently supported: *rsa.PrivateKey,
// *ecdsa.PrivateKey, ed25519.PrivateKey (not a pointer), and *ecdh.PrivateKey.
// Unsupported key types result in an error.
//
// This kind of key is commonly encoded in PEM blocks of type "PRIVATE KEY".
func MarshalPKCS8PrivateKey(key any) ([]byte, error) {
var privKey pkcs8
switch k := key.(type) {
case *rsa.PrivateKey:
privKey.Algo = pkix.AlgorithmIdentifier{
Algorithm: oidPublicKeyRSA,
Parameters: asn1.NullRawValue,
}
privKey.PrivateKey = MarshalPKCS1PrivateKey(k)
case *ecdsa.PrivateKey:
oid, ok := oidFromNamedCurve(k.Curve)
if !ok {
return nil, errors.New("x509: unknown curve while marshaling to PKCS#8")
}
oidBytes, err := asn1.Marshal(oid)
if err != nil {
return nil, errors.New("x509: failed to marshal curve OID: " + err.Error())
}
privKey.Algo = pkix.AlgorithmIdentifier{
Algorithm: oidPublicKeyECDSA,
Parameters: asn1.RawValue{
FullBytes: oidBytes,
},
}
if privKey.PrivateKey, err = marshalECPrivateKeyWithOID(k, nil); err != nil {
return nil, errors.New("x509: failed to marshal EC private key while building PKCS#8: " + err.Error())
}
case ed25519.PrivateKey:
privKey.Algo = pkix.AlgorithmIdentifier{
Algorithm: oidPublicKeyEd25519,
}
curvePrivateKey, err := asn1.Marshal(k.Seed())
if err != nil {
return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
}
privKey.PrivateKey = curvePrivateKey
case *ecdh.PrivateKey:
if k.Curve() == ecdh.X25519() {
privKey.Algo = pkix.AlgorithmIdentifier{
Algorithm: oidPublicKeyX25519,
}
var err error
if privKey.PrivateKey, err = asn1.Marshal(k.Bytes()); err != nil {
return nil, fmt.Errorf("x509: failed to marshal private key: %v", err)
}
} else {
oid, ok := oidFromECDHCurve(k.Curve())
if !ok {
return nil, errors.New("x509: unknown curve while marshaling to PKCS#8")
}
oidBytes, err := asn1.Marshal(oid)
if err != nil {
return nil, errors.New("x509: failed to marshal curve OID: " + err.Error())
}
privKey.Algo = pkix.AlgorithmIdentifier{
Algorithm: oidPublicKeyECDSA,
Parameters: asn1.RawValue{
FullBytes: oidBytes,
},
}
if privKey.PrivateKey, err = marshalECDHPrivateKey(k); err != nil {
return nil, errors.New("x509: failed to marshal EC private key while building PKCS#8: " + err.Error())
}
}
default:
return nil, fmt.Errorf("x509: unknown key type while marshaling PKCS#8: %T", key)
}
return asn1.Marshal(privKey)
}
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